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Sample records for accelerator-driven subcritical reactor

  1. Neutrino Physics with Accelerator Driven Subcritical Reactors

    NASA Astrophysics Data System (ADS)

    Ciuffoli, Emilio

    2017-09-01

    Accelerator Driven Subcritical System (ADS) reactors are being developed around the world, to produce energy and, at the same time, to provide an efficient way to dispose of and to recycle nuclear waste. Used nuclear fuel, by itself, cannot sustain a chain reaction; however in ADS reactors the additional neutrons which are required will be supplied by a high-intensity accelerator. This accelerator will produce, as a by-product, a large quantity of {\\bar{ν }}μ via muon Decay At Rest (µDAR). Using liquid scintillators, it will be possible to to measure the CP-violating phase δCP and to look for experimental signs of the presence of sterile neutrinos in the appearance channel, testing the LSND and MiniBooNE anomalies. Even in the first stage of the project, when the beam energy will be lower, it will be possible to produce {\\bar{ν }}e via Isotope Decay At Rest (IsoDAR), which can be used to provide competitive bounds on sterile neutrinos in the disappearance channel. I will consider several experimental setups in which the antineutrinos are created using accelerators that will be constructed as part of the China-ADS program.

  2. Comparing the new generation accelerator driven subcritical reactor system (ADS) to traditional critical reactors

    NASA Astrophysics Data System (ADS)

    Kemah, Elif; Akkaya, Recep; Tokgöz, Seyit Rıza

    2017-02-01

    In recent years, the accelerator driven subcritical reactors have taken great interest worldwide. The Accelerator Driven System (ADS) has been used to produce neutron in subcritical state by the external proton beam source. These reactors, which are hybrid systems, are important in production of clean and safe energy and conversion of radioactive waste. The ADS with the selection of reliability and robust target materials have been the new generation of fission reactors. In addition, in the ADS Reactors the problems of long-lived radioactive fission products and waste actinides encountered in the fission process of the reactor during incineration can be solved, and ADS has come to the forefront of thorium as fuel for the reactors.

  3. High power ring methods and accelerator driven subcritical reactor application

    SciTech Connect

    Tahar, Malek Haj

    2016-08-07

    High power proton accelerators allow providing, by spallation reaction, the neutron fluxes necessary in the synthesis of fissile material, starting from Uranium 238 or Thorium 232. This is the basis of the concept of sub-critical operation of a reactor, for energy production or nuclear waste transmutation, with the objective of achieving cleaner, safer and more efficient process than today’s technologies allow. Designing, building and operating a proton accelerator in the 500-1000 MeV energy range, CW regime, MW power class still remains a challenge nowadays. There is a limited number of installations at present achieving beam characteristics in that class, e.g., PSI in Villigen, 590 MeV CW beam from a cyclotron, SNS in Oakland, 1 GeV pulsed beam from a linear accelerator, in addition to projects as the ESS in Europe, a 5 MW beam from a linear accelerator. Furthermore, coupling an accelerator to a sub-critical nuclear reactor is a challenging proposition: some of the key issues/requirements are the design of a spallation target to withstand high power densities as well as ensure the safety of the installation. These two domains are the grounds of the PhD work: the focus is on the high power ring methods in the frame of the KURRI FFAG collaboration in Japan: upgrade of the installation towards high intensity is crucial to demonstrate the high beam power capability of FFAG. Thus, modeling of the beam dynamics and benchmarking of different codes was undertaken to validate the simulation results. Experimental results revealed some major losses that need to be understood and eventually overcome. By developing analytical models that account for the field defects, one identified major sources of imperfection in the design of scaling FFAG that explain the important tune variations resulting in the crossing of several betatron resonances. A new formula is derived to compute the tunes and properties established that characterize the effect of the field imperfections on the

  4. Electron versus proton accelerator driven sub-critical system performance using TRIGA reactors at power

    SciTech Connect

    Carta, M.; Burgio, N.; D'Angelo, A.; Santagata, A.; Petrovich, C.; Schikorr, M.; Beller, D.; Felice, L. S.; Imel, G.; Salvatores, M.

    2006-07-01

    This paper provides a comparison of the performance of an electron accelerator-driven experiment, under discussion within the Reactor Accelerator Coupling Experiments (RACE) Project, being conducted within the U.S. Dept. of Energy's Advanced Fuel Cycle Initiative (AFCI), and of the proton-driven experiment TRADE (TRIGA Accelerator Driven Experiment) originally planned at ENEA-Casaccia in Italy. Both experiments foresee the coupling to sub-critical TRIGA core configurations, and are aimed to investigate the relevant kinetic and dynamic accelerator-driven systems (ADS) core behavior characteristics in the presence of thermal reactivity feedback effects. TRADE was based on the coupling of an upgraded proton cyclotron, producing neutrons via spallation reactions on a tantalum (Ta) target, with the core driven at a maximum power around 200 kW. RACE is based on the coupling of an Electron Linac accelerator, producing neutrons via photoneutron reactions on a tungsten-copper (W-Cu) or uranium (U) target, with the core driven at a maximum power around 50 kW. The paper is focused on analysis of expected dynamic power response of the RACE core following reactivity and/or source transients. TRADE and RACE target-core power coupling coefficients are compared and discussed. (authors)

  5. Operation and reactivity measurements of an accelerator driven subcritical TRIGA reactor

    NASA Astrophysics Data System (ADS)

    O'Kelly, David Sean

    Experiments were performed at the Nuclear Engineering Teaching Laboratory (NETL) in 2005 and 2006 in which a 20 MeV linear electron accelerator operating as a photoneutron source was coupled to the TRIGA (Training, Research, Isotope production, General Atomics) Mark II research reactor at the University of Texas at Austin (UT) to simulate the operation and characteristics of a full-scale accelerator driven subcritical system (ADSS). The experimental program provided a relatively low-cost substitute for the higher power and complexity of internationally proposed systems utilizing proton accelerators and spallation neutron sources for an advanced ADSS that may be used for the burning of high-level radioactive waste. Various instrumentation methods that permitted ADSS neutron flux monitoring in high gamma radiation fields were successfully explored and the data was used to evaluate the Stochastic Pulsed Feynman method for reactivity monitoring.

  6. High-value use of weapons-plutonium by burning in molten salt accelerator-driven subcritical systems or reactors

    SciTech Connect

    Bowman, C.D.; Venneri, F.

    1993-11-01

    The application of thermal-spectrum molten-salt reactors and accelerator-driven subcritical systems to the destruction of weapons-return plutonium is considered from the perspective of deriving the maximum societal benefit. The enhancement of electric power production from burning the fertile fuel {sup 232}Th with the plutonium is evaluated. Also the enhancement of destruction of the accumulated waste from commercial nuclear reactors is considered using the neutron-rich weapons plutonium. Most cases examined include the concurrent transmutation of the long-lived actinide and fission product waste ({sup 99}Tc, {sup 129}I, {sup 135}Cs, {sup 126}Sn and {sup 79}Se).

  7. Accelerator driven sub-critical core

    DOEpatents

    McIntyre, Peter M; Sattarov, Akhdiyor

    2015-03-17

    Systems and methods for operating an accelerator driven sub-critical core. In one embodiment, a fission power generator includes a sub-critical core and a plurality of proton beam generators. Each of the proton beam generators is configured to concurrently provide a proton beam into a different area of the sub-critical core. Each proton beam scatters neutrons within the sub-critical core. The plurality of proton beam generators provides aggregate power to the sub-critical core, via the proton beams, to scatter neutrons sufficient to initiate fission in the sub-critical core.

  8. Accelerator Driven System Based on Plutonium Subcritical Reactor and 660 MeV Phasotron

    SciTech Connect

    Arkhipov, V.A.; Barashenkov, V.S.; Buttsev, V.S.; Chultem, D.; Dudarev, S.Yu.; Furman, V.I.; Gudowski, W.; Janczyszyn, J.; Maltsev, A.A.; Onischenko, L.M.; Pogodajev, G.N.; Polanski, A.; Popov, Yu.P.; Puzynin, I.V.; Sissakian, A.N.; Taczanowski, S.

    1999-12-31

    The proposal presents a PLUTONIUM BASED ENERGY AMPLIFIER TESTING CONCEPT which employs a plutonium subcritical assembly and a 660 MeV proton accelerator. operating in the JINR (Dubna, Russia). To make the present conceptual design of the Plutonium Energy Amplifier we have chosen a nominal unit capacity of 20 kW (thermal). This corresponds to a multiplication coefficient, keff, between 0.94 and 0.95 and an energy gain about 20.

  9. Accelerator driven system based on plutonium subcritical reactor and 660 MeV phasotron

    SciTech Connect

    Arkhipov, V. A.; Barashenkov, V. S.; Buttsev, V. S.; Chultem, D.; Furman, V. I.; Maltsev, A. A.; Onischenko, L. M.; Pogodajev, G. N.; Popov, Yu. P.; Puzynin, I. V.; Sissakian, A. N.; Dudarev, S. Yu.; Gudowski, W.; Janczyszyn, J.; Polanski, A.; Taczanowski, S.

    1999-11-16

    The proposal presents a PLUTONIUM BASED ENERGY AMPLIFIER TESTING CONCEPT which employs a plutonium subcritical assembly and a 660 MeV proton accelerator, operating in the the JINR (Dubna, Russia). To make the present conceptual design of the Plutonium Energy Amplifier we have chosen a nominal unit capacity of 20 kW (thermal). This corresponds to the multiplication coefficient keff between 0.94 and 0.95 and the energetic gain about 20.

  10. Conceptual design of thorium-fuelled Mitrailleuse accelerator-driven subcritical reactor using D-Be neutron source

    SciTech Connect

    Kokubo, Y.; Kamei, T.

    2012-07-01

    A distributed accelerator is a charged-particle accelerator that uses a new acceleration method based on repeated electrostatic acceleration. This method offers outstanding benefits not possible with the conventional radio-frequency acceleration method, including: (1) high acceleration efficiency, (2) large acceleration current, and (3) lower failure rate made possible by a fully solid-state acceleration field generation circuit. A 'Mitrailleuse Accelerator' is a product we have conceived to optimize this distributed accelerator technology for use with a high-strength neutron source. We have completed the conceptual design of a Mitrailleuse Accelerator and of a thorium-fuelled subcritical reactor driven by a Mitrailleuse Accelerator. This paper presents the conceptual design details and approach to implementing the subcritical reactor core. We will spend the next year or so on detailed design work, and then will start work on developing a prototype for demonstration. If there are no obstacles in setting up a development organization, we expect to finish verifying the prototype's performance by the third quarter of 2015. (authors)

  11. An accelerator-driven reactor for meeting future energy demand

    SciTech Connect

    Takahashi, Hiroshi; Yang, Y.; Yu, A.

    1997-12-31

    Fissile fuel can be produced at a high rate using an accelerator-driven Pu-fueled subcritical fast reactor which avoids encountering a shortage of Pu during a high growth rate in the production of nuclear energy. Furthermore, the necessity of the early introduction of the fast reactor can be moderated. Subcritical operation provides flexible nuclear energy options along with high neutron economy for producing the fuel, for transmuting high-level waste such as minor actinides, and for efficiently converting excess and military Pu into proliferation-resistant fuel.

  12. Accelerator-driven subcritical facility:Conceptual design development

    NASA Astrophysics Data System (ADS)

    Gohar, Yousry; Bolshinsky, Igor; Naberezhnev, Dmitry; Duo, Jose; Belch, Henry; Bailey, James

    2006-06-01

    A conceptual design development of an accelerator-driven subcritical facility has been carried out in the preparation of a joint activity with Kharkov Institute of Physics and Technology of Ukraine. The main functions of the facility are the medical isotope production and the support of the Ukraine nuclear industry. An electron accelerator is considered to drive the subcritical assembly. The neutron source intensity and spectrum have been studied. The energy deposition, spatial neutron generation, neutron utilization fraction, and target dimensions have been quantified to define the main target performance parameters, and to select the target material and beam parameters. Different target conceptual designs have been developed based the engineering requirements including heat transfer, thermal hydraulics, structure, and material issues. The subcritical assembly is designed to obtain the highest possible neutron flux level with a Keff of 0.98. Different fuel materials, uranium enrichments, and reflector materials are considered in the design process. The possibility of using low enrichment uranium without penalizing the facility performance is carefully evaluated. The mechanical design of the facility has been developed to maximize its utility and minimize the time for replacing the target and the fuel assemblies. Safety, reliability, and environmental considerations are included in the facility conceptual design. The facility is configured to accommodate future design improvements, upgrades, and new missions. In addition, it has large design margins to accommodate different operating conditions and parameters. In this paper, the conceptual design and the design analyses of the facility will be presented.

  13. Detector positioning for the initial subcriticality level determination in accelerator-driven systems

    SciTech Connect

    Uyttenhove, W.; Van Den Eynde, G.; Baeten, P.; Kochetkov, A.; Vittiglio, G.; Wagemans, J.; Lathouwers, D.; Kloosterman, J. L.; Van Der Hagen, T. J. H. H.; Wols, F.; Billebaud, A.; Chabod, S.; Thybault, H. E.

    2012-07-01

    Within the GUINEVERE project (Generation of Uninterrupted Intense Neutrons at the lead Venus Reactor) carried out at SCK-CEN in Mol, the continuous deuteron accelerator GENEPI-3C was coupled to the VENUS-F fast simulated lead-cooled reactor. Today the FREYA project (Fast Reactor Experiments for hYbrid Applications) is ongoing to study the neutronic behavior of this Accelerator Driven System (ADS) during different phases of operation. In particular the set-up of a monitoring system for the subcriticality of an ADS is envisaged to guarantee safe operation of the installation. The methodology for subcriticality monitoring in ADS takes into account the determination of the initial subcriticality level, the monitoring of reactivity variations, and interim cross-checking. At start-up, the Pulsed Neutron Source (PNS) technique is envisaged to determine the initial subcriticality level. Thanks to its reference critical state, the PNS technique can be validated on the VENUS-F core. A detector positioning methodology for the PNS technique is set up in this paper for the subcritical VENUS-F core, based on the reduction of higher harmonics in a static evaluation of the Sjoestrand area method. A first case study is provided on the VENUS-F core. This method can be generalised in order to create general rules for detector positions and types for full-scale ADS. (authors)

  14. New options for developing of nuclear energy using an accelerator-driven reactor

    SciTech Connect

    Takahashi, Hiroshi

    1997-09-01

    Fissile fuel can be produced at a high rate using an accelerator-driven Pu-fueled subcritical fast reactor. Thus, the necessity of early introduction of the fast reactor can be moderated. High reliability of the proton accelerator, which is essential to implementing an accelerator-driven reactor in the nuclear energy field can be achieved by a slight extension of the accelerator`s length, with only a small economical penalty. Subcritical operation provides flexible nuclear energy options including high neutron economy producing the fuel, transmuting high-level wastes, such as minor actinides, and of converting efficiently the excess Pu and military Pu into proliferation-resistant fuel.

  15. Candidate molten salt investigation for an accelerator driven subcritical core

    NASA Astrophysics Data System (ADS)

    Sooby, E.; Baty, A.; Beneš, O.; McIntyre, P.; Pogue, N.; Salanne, M.; Sattarov, A.

    2013-09-01

    We report a design for accelerator-driven subcritical fission in a molten salt core (ADSMS) that utilizes a fuel salt composed of NaCl and transuranic (TRU) chlorides. The ADSMS core is designed for fast neutronics (28% of neutrons >1 MeV) to optimize TRU destruction. The choice of a NaCl-based salt offers benefits for corrosion, operating temperature, and actinide solubility as compared with LiF-based fuel salts. A molecular dynamics (MD) code has been used to estimate properties of the molten salt system which are important for ADSMS design but have never been measured experimentally. Results from the MD studies are reported. Experimental measurements of fuel salt properties and studies of corrosion and radiation damage on candidate metals for the core vessel are anticipated. A special thanks is due to Prof. Paul Madden for introducing the ADSMS group to the concept of using the molten salt as the spallation target, rather than a conventional heavy metal spallation target. This feature helps to optimize this core as a Pu/TRU burner.

  16. Research program for the 660 MeV proton accelerator driven MOX-plutonium subcritical assembly

    NASA Astrophysics Data System (ADS)

    Barashenkov, V. S.; Buttsev, V. S.; Buttseva, G. L.; Dudarev, S. Ju.; Polanski, A.; Puzynin, I. V.; Sissakian, A. N.

    2000-07-01

    This paper presents the research program of the Experimental Accelerator Driven System (ADS), which employs a subcritical assembly and a 660 MeV proton accelerator operating in the Laboratory of Nuclear Problems at the Joint Institute for Nuclear Research in Dubna. Mixed-oxide (MOX) fuel (25% PuO2+75% UO2) designed for the BN-600 reactor use will be adopted for the core of the assembly. The present conceptual design of the experimental subcritical assembly is based on a core nominal unit capacity of 15 kW (thermal). This corresponds to the multiplication coefficient keff=0.945, energetic gain G=30, and accelerator beam power of 0.5 kW.

  17. Safety and control of accelerator-driven subcritical systems

    SciTech Connect

    Rief, H.; Takahashi, H.

    1995-10-01

    To study control and safety of accelertor driven nuclear systems, a one point kinetic model was developed and programed. It deals with fast transients as a function of reactivity insertion. Doppler feedback, and the intensity of an external neutron source. The model allows for a simultaneous calculation of an equivalent critical reactor. It was validated by a comparison with a benchmark specified by the Nuclear Energy Agency Committee of Reactor Physics. Additional features are the possibility of inserting a linear or quadratic time dependent reactivity ramp which may account for gravity induced accidents like earthquakes, the possibility to shut down the external neutron source by an exponential decay law of the form exp({minus}t/{tau}), and a graphical display of the power and reactivity changes. The calculations revealed that such boosters behave quite benignly even if they are only slightly subcritical.

  18. Disposition of nuclear waste using subcritical accelerator-driven systems

    SciTech Connect

    Venneri, F.; Li, N.; Williamson, M.; Houts, M.; Lawrence, G.

    1998-12-31

    Spent fuel from nuclear power plants contains large quantities of Pu, other actinides, and fission products (FP). This creates challenges for permanent disposal because of the long half-lives of some isotopes and the potential for diversion of the fissile material. Two issues of concern for the US repository concept are: (1) long-term radiological risk peaking tens-of-thousands of years in the future; and (2) short-term thermal loading (decay heat) that limits capacity. An accelerator-driven neutron source can destroy actinides through fission, and can convert long-lived fission products to shorter-lived or stable isotopes. Studies over the past decade have established that accelerator transmutation of waste (ATW) can have a major beneficial impact on the nuclear waste problem. Specifically, the ATW concept the authors are evaluating: (1) destroys over 99.9% of the actinides; (2) destroys over 99.9% of the Tc and I; (3) separates Sr-90 and Cs-137; (4) separates uranium from the spent fuel; (5) produces electric power.

  19. Accelerators for Subcritical Molten-Salt Reactors

    SciTech Connect

    Johnson, Roland

    2011-08-03

    Accelerator parameters for subcritical reactors have usually been based on using solid nuclear fuel much like that used in all operating critical reactors as well as the thorium burning accelerator-driven energy amplifier proposed by Rubbia et al. An attractive alternative reactor design that used molten salt fuel was experimentally studied at ORNL in the 1960s, where a critical molten salt reactor was successfully operated using enriched U235 or U233 tetrafluoride fuels. These experiments give confidence that an accelerator-driven subcritical molten salt reactor will work better than conventional reactors, having better efficiency due to their higher operating temperature, having the inherent safety of subcritical operation, and having constant purging of volatile radioactive elements to eliminate their accumulation and potential accidental release in dangerous amounts. Moreover, the requirements to drive a molten salt reactor can be considerably relaxed compared to a solid fuel reactor, especially regarding accelerator reliability and spallation neutron targetry, to the point that much of the required technology exists today. It is proposed that Project-X be developed into a prototype commercial machine to produce energy for the world by, for example, burning thorium in India and nuclear waste from conventional reactors in the USA.

  20. Temperature Profile of the Solution Vessel of an Accelerator-Driven Subcritical Fissile Solution System

    SciTech Connect

    Klein, Steven Karl; Determan, John C.

    2015-09-14

    Dynamic System Simulation (DSS) models of fissile solution systems have been developed and verified against a variety of historical configurations. DSS techniques have been applied specifically to subcritical accelerator-driven systems using fissile solution fuels of uranium. Initial DSS models were developed in DESIRE, a specialized simulation scripting language. In order to tailor the DSS models to specifically meet needs of system designers they were converted to a Visual Studio implementation, and one of these subsequently to National Instrument’s LabVIEW for human factors engineering and operator training. Specific operational characteristics of subcritical accelerator-driven systems have been examined using a DSS model tailored to this particular class using fissile fuel.

  1. Disposition of Nuclear Waste Using Subcritical Accelerator-Driven Systems

    SciTech Connect

    Doolen, G.D.; Venneri, F.; Li, N.; Williamson, M.A.; Houts, M.; Lawrence, G.

    1998-06-27

    ATW destroys virtually all the plutonium and higher actinides without reprocessing the spent fuel in a way that could lead to weapons material diversion. An ATW facility consists of three major elements: (1) a high-power proton linear accelerator; (2) a pyrochemical spent fuel treatment i waste cleanup system; (3) a liquid lead-bismuth cooled burner that produces and utilizes an intense source-driven neutron flux for transmutation in a heterogeneous (solid fuel) core. The concept is the result of many years of development at LANL as well as other major international research centers. Once demonstrated and developed, ATW could be an essential part of a global non-proliferation strategy for countries that could build up large quantities of plutonium from their commercial reactor waste. ATW technology, initially proposed in the US, has received wide and rapidly increasing attention abroad, especially in Europe and the Far East with major programs now being planned, organized and tided. Substantial convergence presently exists on the technology choices among the programs, opening the possibility of a strong and effective international collaboration on the phased development of the ATW technology.

  2. Disposition of nuclear waste using subcritical accelerator-driven systems

    SciTech Connect

    Venneri, F.; Li, N.; Williamson, M.; Houts, M.; Lawrence, G.

    1998-12-01

    Studies have shown that the repository long-term radiological risk is from the long-lived transuranics and the fission products Tc-99 and I-129, thermal loading concerns arise mainly form the short-lived fission products Sr-90 and Cs-137. In relation to the disposition of nuclear waste, ATW is expected to accomplish the following: (1) destroy over 99.9% of the actinides; (2) destroy over 99.9% of the Tc and I; (3) separate Sr and Cs (short half-life isotopes); (4) separate uranium; (5) produce electricity. In the ATW concept, spent fuel would be shipped to a ATW site where the plutonium, other transuranics and selected long-lived fission products would be destroyed by fission or transmutation in their only pass through the facility. This approach contrasts with the present-day reprocessing practices in Europe and Japan, during which high purity plutonium is produced and used in the fabrication of fresh mixed-oxide fuel (MOX) that is shipped off-site for use in light water reactors.

  3. Physics analyses of an accelerator-driven sub-critical assembly

    NASA Astrophysics Data System (ADS)

    Naberezhnev, Dmitry G.; Gohar, Yousry; Bailey, James; Belch, Henry

    2006-06-01

    Physics analyses have been performed for an accelerator-driven sub-critical assembly as a part of the Argonne National Laboratory activity in preparation for a joint conceptual design with the Kharkov Institute of Physics and Technology (KIPT) of Ukraine. KIPT has a plan to construct an accelerator-driven sub-critical assembly targeted towards the medical isotope production and the support of the Ukraine nuclear industry. The external neutron source is produced either through photonuclear reactions in tungsten or uranium targets, or deuteron reactions in a beryllium target. KIPT intends using the high-enriched uranium (HEU) for the fuel of the sub-critical assembly. The main objective of this paper is to study the possibility of utilizing low-enriched uranium (LEU) fuel instead of HEU fuel without penalizing the sub-critical assembly performance, in particular the neutron flux level. In the course of this activity, several studies have been carried out to investigate the main choices for the system's parameters. The external neutron source has been characterized and a pre-conceptual target design has been developed. Several sub-critical configurations with different fuel enrichments and densities have been considered. Based on our analysis, it was shown that the performance of the LEU fuel is comparable with that of the HEU fuel. The LEU fuel sub-critical assembly with 200-MeV electron energy and 100-kW electron beam power has an average total flux of ˜2.50×10 13 n/s cm 2 in the irradiation channels. The corresponding total facility power is ˜204 kW divided into 91 and 113 kW deposited in the target and sub-critical assemblies, respectively.

  4. Neutronics of accelerator-driven subcritical fission for burning transuranics in used nuclear fuel

    SciTech Connect

    Sattarov, A.; Assadi, S.; Badgley, K.; Baty, A.; Comeaux, J.; Gerity, J.; Kellams, J.; Mcintyre, P.; Pogue, N.; Sooby, E.; Tsvetkov, P.; Rosaire, G.; Mann, T.

    2013-04-19

    We report the development of a conceptual design for accelerator-driven subcritical fission in a molten salt core (ADSMS). ADSMS is capable of destroying all of the transuranics at the same rate and proportion as they are produced in a conventional nuclear power plant. The ADSMS core is fueled solely by transuranics extracted from used nuclear fuel and reduces its radiotoxicity by a factor 10,000. ADSMS offers a way to close the nuclear fuel cycle so that the full energy potential in the fertile fuels uranium and thorium can be recovered.

  5. High brightness 50 MeV Cyclotron for Accelerator-Driven Subcritical Fission

    NASA Astrophysics Data System (ADS)

    Assadi, Saeed; Badgley, Karie; Mann, Thomas; McIntyre, Peter; Pogue, Nathaniel; Sattarov, Akhdiyor

    2011-10-01

    The Accelerator Research Lab at Texas A&M University is developing new accelerator technology for a high-brightness, high-current cyclotron with capabilities that will be beneficial for applications to accelerator-driven subcritical fission, medical isotope production, and proton therapy. As a first embodiment of the technology, we are developing a detailed design for TAMU-50, a 50 MeV, 5 mA proton cyclotron with high beam brightness. In this presentation we present devices and beamline components for injection, extraction, controls and diagnostics. We emphasize the system integration and implementation of TAMU-50 for production of medical radioisotopes.

  6. Neutronics for critical fission reactors and subcritical fission in hybrids

    SciTech Connect

    Salvatores, Massimo

    2012-06-19

    The requirements of future innovative nuclear fuel cycles will focus on safety, sustainability and radioactive waste minimization. Critical fast neutron reactors and sub-critical, external source driven systems (accelerator driven and fusion-fission hybrids) have a potential role to meet these requirements in view of their physics characteristics. This paper provides a short introduction to these features.

  7. Superconducting Accelerating Structure for High-Current Cyclotrons for Accelerator-Driven Subcritical Fission

    NASA Astrophysics Data System (ADS)

    Pogue, Nathaniel; McIntyre, Peter; Sattarov, Akhdiyor

    2011-10-01

    An accelerator driven molten salt fission core is being designed to provide reliable power by subcritical nuclear fission for the next few millennia. Fission is driven by proton beams from a flux-coupled stack of three high-current cyclotrons. A key innovation in attaining the needed beam current and efficiency is a superconducting Niobium rf accelerating cavity that can accelerate bunches in the 200 orbits uniformly. The unique design allows for several cavities to be stacked, and also provides uniform acceleration and eliminates higher order modes in the cyclotron. The design and properties of the superconducting cavity will increase the efficiency of the cyclotron and the overall energy amplification from the molten salt core by an order of magnitude compared to conventional designs.

  8. Coupling MCNP-DSP and LAHET Monte Carlo Codes for Designing Subcriticality Monitors for Accelerator-Driven Systems

    SciTech Connect

    Valentine, T.E.; Rugama, Y. Munoz-Cobos, J.; Perez, R.

    2000-10-23

    The design of reactivity monitoring systems for accelerator-driven systems must be investigated to ensure that such systems remain subcritical during operation. The Monte Carlo codes LAHET and MCNP-DSP were combined together to facilitate the design of reactivity monitoring systems. The coupling of LAHET and MCNP-DSP provides a tool that can be used to simulate a variety of subcritical measurements such as the pulsed neutron, Rossi-{alpha}, or noise analysis measurements.

  9. Kinetics of accelerator driven devices

    SciTech Connect

    Perry, R.T.; Buksa, J.; Houts, M.

    1994-09-01

    Kinetic calculations were made to show that subcritical accelerator driven devices are robust and stable. The calculations show that large changes in reactivity that would lead to an uncontrollable excursion in a reactor would lead only to a new power level in subcritical device. Calculations were also made to show the rate of power changes resulting from startup and shutdown, and that methods also exist for continuously monitoring the reactivity of a subcritical system.

  10. A role of accelerator-driven reactor to meet future energy demands

    SciTech Connect

    Takahashi, H.; An, Y.; Yang, Y.; Zhao, Y.; Tsoupas, N.

    1998-03-01

    Fissile fuel can be produced at a high rate using an accelerator driven Pu fueled fast reactor operated at deep subcriticality; this approach avoids encountering a shortage of Pu during a high rate of growth in the production of nuclear energy. Slightly reducing the acceleration field minimizes the tripping of the beam and the radiation dose from the accelerator; hence the accelerator can be operated as a highly reliable industrial machine. The usefulness of a windowless liquid jet target, which eliminates the spreading of the beam and problems of radiation damage is emphasized, in association with the small size of the target. The requirements for a proton beam accelerator for this system are discussed.

  11. Study of a multi-beam accelerator driven thorium reactor

    SciTech Connect

    Ludewig, H.; Aronson, A.

    2011-03-01

    The primary advantages that accelerator driven systems have over critical reactors are: (1) Greater flexibility regarding the composition and placement of fissile, fertile, or fission product waste within the blanket surrounding the target, and (2) Potentially enhanced safety brought about by operating at a sufficiently low value of the multiplication factor to preclude reactivity induced events. The control of the power production can be achieved by vary the accelerator beam current. Furthermore, once the beam is shut off the system shuts down. The primary difference between the operation of an accelerator driven system and a critical system is the issue of beam interruptions of the accelerator. These beam interruptions impose thermo-mechanical loads on the fuel and mechanical components not found in critical systems. Studies have been performed to estimate an acceptable number of trips, and the value is significantly less stringent than had been previously estimated. The number of acceptable beam interruptions is a function of the length of the interruption and the mission of the system. Thus, for demonstration type systems and interruption durations of 1sec < t < 5mins, and t > 5mins 2500/yr and 50/yr are deemed acceptable. However, for industrial scale power generation without energy storage type systems and interruption durations of t < 1sec., 1sec < t < 10secs., 10secs < t < 5mins, and t > 5mins, the acceptable number of interruptions are 25000, 2500, 250, and 3 respectively. However, it has also been concluded that further development is required to reduce the number of trips. It is with this in mind that the following study was undertaken. The primary focus of this study will be the merit of a multi-beam target system, which allows for multiple spallation sources within the target/blanket assembly. In this manner it is possible to ameliorate the effects of sudden accelerator beam interruption on the surrounding reactor, since the remaining beams will still

  12. CFD Analysis and Design of Detailed Target Configurations for an Accelerator-Driven Subcritical System

    SciTech Connect

    Kraus, Adam; Merzari, Elia; Sofu, Tanju; Zhong, Zhaopeng; Gohar, Yousry

    2016-08-01

    High-fidelity analysis has been utilized in the design of beam target options for an accelerator driven subcritical system. Designs featuring stacks of plates with square cross section have been investigated for both tungsten and uranium target materials. The presented work includes the first thermal-hydraulic simulations of the full, detailed target geometry. The innovative target cooling manifold design features many regions with complex flow features, including 90 bends and merging jets, which necessitate three-dimensional fluid simulations. These were performed using the commercial computational fluid dynamics code STAR-CCM+. Conjugate heat transfer was modeled between the plates, cladding, manifold structure, and fluid. Steady-state simulations were performed but lacked good residual convergence. Unsteady simulations were then performed, which converged well and demonstrated that flow instability existed in the lower portion of the manifold. It was established that the flow instability had little effect on the peak plate temperatures, which were well below the melting point. The estimated plate surface temperatures and target region pressure were shown to provide sufficient margin to subcooled boiling for standard operating conditions. This demonstrated the safety of both potential target configurations during normal operation.

  13. Conceptual design of minor actinides burner with an accelerator-driven subcritical system.

    SciTech Connect

    Cao, Y.; Gohar, Y.

    2011-11-04

    In the environmental impact study of the Yucca Mountain nuclear waste repository, the limit of spent nuclear fuel (SNF) for disposal is assessed at 70,000 metric tons of heavy metal (MTHM), among which 63,000 MTHM are the projected SNF discharge from U.S. commercial nuclear power plants though 2011. Within the 70,000 MTHM of SNF in storage, approximately 115 tons would be minor actinides (MAs) and 585 tons would be plutonium. This study describes the conceptual design of an accelerator-driven subcritical (ADS) system intended to utilize (burn) the 115 tons of MAs. The ADS system consists of a subcritical fission blanket where the MAs fuel will be burned, a spallation neutron source to drive the fission blanket, and a radiation shield to reduce the radiation dose to an acceptable level. The spallation neutrons are generated from the interaction of a 1 GeV proton beam with a lead-bismuth eutectic (LBE) or liquid lead target. In this concept, the fission blanket consists of a liquid mobile fuel and the fuel carrier can be LBE, liquid lead, or molten salt. The actinide fuel materials are dissolved, mixed, or suspended in the liquid fuel carrier. Therefore, fresh fuel can be fed into the fission blanket to adjust its reactivity and to control system power during operation. Monte Carlo analyses were performed to determine the overall parameters of an ADS system utilizing LBE as an example. Steady-state Monte Carlo simulations were studied for three fission blanket configurations that are similar except that the loaded amount of actinide fuel in the LBE is either 5, 7, or 10% of the total volume of the blanket, respectively. The neutron multiplication factor values of the three configurations are all approximately 0.98 and the MA initial inventories are each approximately 10 tons. Monte Carlo burnup simulations using the MCB5 code were performed to analyze the performance of the three conceptual ADS systems. Preliminary burnup analysis shows that all three conceptual ADS

  14. Accelerator-driven subcritical fission in molten salt core: Closing the nuclear fuel cycle for green nuclear energy

    SciTech Connect

    McIntyre, Peter; Assadi, Saeed; Badgley, Karie; Baker, William; Comeaux, Justin; Gerity, James; Kellams, Joshua; McInturff, Al; Pogue, Nathaniel; Sattarov, Akhdiyor; Sooby, Elizabeth; Tsvetkov, Pavel; Phongikaroon, Supathorn; Simpson, Michael

    2013-04-19

    A technology for accelerator-driven subcritical fission in a molten salt core (ADSMS) is being developed as a basis for the destruction of the transuranics in used nuclear fuel. The molten salt fuel is a eutectic mixture of NaCl and the chlorides of the transuranics and fission products. The core is driven by proton beams from a strong-focusing cyclotron stack. This approach uniquely provides an intrinsically safe means to drive a core fueled only with transuranics, thereby eliminating competing breeding terms.

  15. Status of intense permanent magnet proton source for China-accelerator driven sub-critical system Linac

    SciTech Connect

    Wu, Q. Ma, H. Y.; Yang, Y.; Sun, L. T.; Zhang, X. Z.; Zhang, Z. M.; Zhao, H. Y.; He, Y.; Zhao, H. W.

    2016-02-15

    Two compact intense 2.45 GHz permanent magnet proton sources and their corresponding low energy beam transport (LEBT) system were developed successfully for China accelerator driven sub-critical system in 2014. Both the proton sources operate at 35 kV potential. The beams extracted from the ion source are transported by the LEBT, which is composed of two identical solenoids, to the 2.1 MeV Radio-Frequency Quadrupole (RFQ). In order to ensure the safety of the superconducting cavities during commissioning, an electrostatic-chopper has been designed and installed in the LEBT line that can chop the continuous wave beam into a pulsed one. The minimum width of the pulse is less than 10 μs and the fall/rise time of the chopper is about 20 ns. The performance of the proton source and the LEBT, such as beam current, beam profile, emittance and the impact to RFQ injection will be presented.

  16. A small scale accelerator driven subcritical assembly development and demonstration experiment at LAMPF

    SciTech Connect

    Wender, S. A.; Venneri, F.; Bowman, C. D.; Arthur, E. D.; Heighway, E.; Beard, C. A.; Bracht, R. R.; Buksa, J. J.; Chavez, W.; DeVolder, B. G.; Park, J. J.; Parker, R. B.; Pillai, C.; Pitcher, E.; Potter, R. C.; Reid, R. S.; Russell, G. J.; Trujillo, D. A.; Weinacht, D. J.; Wilson, W. B.

    1995-09-15

    A small scale experiment is described that will demonstrate many of the aspects of accelerator-driven transmutation technology. This experiment uses the high-power proton beam from the Los Alamos Meson Physics Facility accelerator and will be located in the Area-A experimental hall. Beam currents of up to 1 mA will be used to produce neutrons with a molten lead target. The target is surrounded by a molten salt and graphite moderator blanket. Fissionable material can be added to the molten salt to demonstrate plutonium burning or transmutation of commercial spent fuel or energy production from thorium. The experiment will be operated at power levels up to 5 MWt.

  17. Burnup calculations for KIPT accelerator driven subcritical facility using Monte Carlo computer codes-MCB and MCNPX.

    SciTech Connect

    Gohar, Y.; Zhong, Z.; Talamo, A.; Nuclear Engineering Division

    2009-06-09

    Argonne National Laboratory (ANL) of USA and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have been collaborating on the conceptual design development of an electron accelerator driven subcritical (ADS) facility, using the KIPT electron accelerator. The neutron source of the subcritical assembly is generated from the interaction of 100 KW electron beam with a natural uranium target. The electron beam has a uniform spatial distribution and electron energy in the range of 100 to 200 MeV. The main functions of the subcritical assembly are the production of medical isotopes and the support of the Ukraine nuclear power industry. Neutron physics experiments and material structure analyses are planned using this facility. With the 100 KW electron beam power, the total thermal power of the facility is {approx}375 kW including the fission power of {approx}260 kW. The burnup of the fissile materials and the buildup of fission products reduce continuously the reactivity during the operation, which reduces the neutron flux level and consequently the facility performance. To preserve the neutron flux level during the operation, fuel assemblies should be added after long operating periods to compensate for the lost reactivity. This process requires accurate prediction of the fuel burnup, the decay behavior of the fission produces, and the introduced reactivity from adding fresh fuel assemblies. The recent developments of the Monte Carlo computer codes, the high speed capability of the computer processors, and the parallel computation techniques made it possible to perform three-dimensional detailed burnup simulations. A full detailed three-dimensional geometrical model is used for the burnup simulations with continuous energy nuclear data libraries for the transport calculations and 63-multigroup or one group cross sections libraries for the depletion calculations. Monte Carlo Computer code MCNPX and MCB are utilized for this study. MCNPX transports the

  18. Requirements of a proton beam accelerator for an accelerator-driven reactor

    SciTech Connect

    Takahashi, H.; Zhao, Y.; Tsoupas, N.; An, Y.; Yamazaki, Y.

    1997-12-31

    When the authors first proposed an accelerator-driven reactor, the concept was opposed by physicists who had earlier used the accelerator for their physics experiments. This opposition arose because they had nuisance experiences in that the accelerator was not reliable, and very often disrupted their work as the accelerator shut down due to electric tripping. This paper discusses the requirements for the proton beam accelerator. It addresses how to solve the tripping problem and how to shape the proton beam.

  19. Accelerator-Driven Subcritical Fission in a Molten Salt Core: Green Nuclear Power for the New Millennium

    NASA Astrophysics Data System (ADS)

    McIntyre, Peter

    2011-10-01

    Scientists at Texas A&M University, Brookhaven National Lab, and Idaho National Lab are developing a design for accelerator-drive subcritical fission in a molten salt core (ADSMS). Three high-power proton beams are delivered to spallation targets in a molten salt core, where they provide ˜3% of the fast neutrons required to sustain 600 MW of fission. The proton beams are produced by a flux-coupled stack of superconducting strong-focusing cyclotrons. The fuel consists of a eutectic of sodium chloride with either spent nuclear fuel from a conventional U power reactor (ADSMS-U) or thorium (ADSMS-Th). The subcritical core cannot go critical under any failure mode. The core cannot melt down even if all power is suddenly lost to the facility for a prolonged period. The ultra-fast neutronics of the core makes it possible to operate in an isobreeding mode, in which neutron capture breeds the fertile nuclide into a fissile nuclide at the same rate that fission burns the fissile nuclide, and consumes 90% of the fertile inventory instead of the 5% consumed in the original use in a conventional power plant. The ultra-fast neutronics produces a very low equilibrium inventory of the long-lived minor actinides, ˜10^4 less than what is produced in conventional power plants. ADSMS offers a method to safely produce the energy needs for all mankind for the next 3000 years.

  20. Neutronics Study on Accelerator Driven Subcritical Systems with Thorium-Based Fuel for Comparison Between Solid and Molten-Salt Fuels

    SciTech Connect

    Ishimoto, Shunsuke; Ishibashi, Kenji; Tenzou, Hideki; Sasa, Toshinobu

    2002-06-15

    Since thorium is an abundant fertile material, there is hope for the thorium-cycle fuels for an accelerator driven subcritical system (ADS). The ADS utilizes neutrons, which are generated by high-energy protons of giga-electron-volt-grade, but cross sections for the interaction of high-energy particles are not available for use in current ADS engineering design. In this paper the neutron behavior in the ADS target based on the related experimental data is clarified, and the feasibility of the ADS regarding both the molten salts (Flibe: {sup 7}LiF-BeF{sub 2}-ThF{sub 4}-{sup 233}UF{sub 4}, chloride: NaCl-ThCl{sub 4}-{sup 233}UCl{sub 4}) and oxide ([Th, {sup 233}U]O{sub 2}) fuels is examined. The difference between the experiment and the calculated result at the ADS high-energy region is discussed. In a comparison of the fuels, the time evolution of k{sub eff} and the beam current in the burning period are calculated. The calculated results suggest that the ADS with solid fuel has better future prospects than that with molten-salt fuels. The ADS with Flibe molten-salt fuel tends to require a high beam current and consequently needs the installation of a metallic spallation target and the continuous removal for fission products and protactinium. In comparison with the Flibe fuel, the ADS with chloride fuel has a flux distribution that is similar to a solid fuel reactor.

  1. Optimum design and criticality safety of a beam-shaping assembly with an accelerator-driven subcritical neutron multiplier for boron neutron capture therapies.

    PubMed

    Hiraga, F

    2015-12-01

    The beam-shaping assembly for boron neutron capture therapies with a compact accelerator-driven subcritical neutron multiplier was designed so that an epithermal neutron flux of 1.9×10(9) cm(-2) s(-1) at the treatment position was generated by 5 MeV protons in a beam current of 2 mA. Changes in the atomic density of (135)Xe in the nuclear fuel due to the operation of the beam-shaping assembly were estimated. The criticality safety of the beam-shaping assembly in terms of Xe poisoning is discussed.

  2. Accelerator driven reactors and nuclear waste management projects in the Czech Republic

    SciTech Connect

    Janouch, F.; Mach, R.

    1995-10-01

    The Czech Republic is almost the only country in the central Europe which continues with the construction of nuclear power reactors. Its small territory and dense population causes public worries concerning the disposal of the spent nuclear fuel. The Czech nuclear scientists and the power companies and the nuclear industries are therefore looking for alternative solutions. The Los Alamos ATW project had received a positive response in the Czech mass-media and even in the industrial and governmental quarters. The recent scientific symposium {open_quotes}Accelerator driven reactors and nuclear waste management{close_quotes} convened at the Liblice castle near Prague, 27-29. 6. 1994 and sponsored by the Czech Energy Company CEZ, reviewed the competencies and experimental basis in the Czech republic and made the first attempt to formulate the national approach and to establish international collaboration in this area.

  3. YALINA facility a sub-critical Accelerator- Driven System (ADS) for nuclear energy research facility description and an overview of the research program (1997-2008).

    SciTech Connect

    Gohar, Y.; Smith, D. L.; Nuclear Engineering Division

    2010-04-28

    The YALINA facility is a zero-power, sub-critical assembly driven by a conventional neutron generator. It was conceived, constructed, and put into operation at the Radiation Physics and Chemistry Problems Institute of the National Academy of Sciences of Belarus located in Minsk-Sosny, Belarus. This facility was conceived for the purpose of investigating the static and dynamic neutronics properties of accelerator driven sub-critical systems, and to serve as a neutron source for investigating the properties of nuclear reactions, in particular transmutation reactions involving minor-actinide nuclei. This report provides a detailed description of this facility and documents the progress of research carried out there during a period of approximately a decade since the facility was conceived and built until the end of 2008. During its history of development and operation to date (1997-2008), the YALINA facility has hosted several foreign groups that worked with the resident staff as collaborators. The participation of Argonne National Laboratory in the YALINA research programs commenced in 2005. For obvious reasons, special emphasis is placed in this report on the work at YALINA facility that has involved Argonne's participation. Attention is given here to the experimental program at YALINA facility as well as to analytical investigations aimed at validating codes and computational procedures and at providing a better understanding of the physics and operational behavior of the YALINA facility in particular, and ADS systems in general, during the period 1997-2008.

  4. Basic concept for an accelerator-driven subcritical system to be used as a long-pulse neutron source for Condensed Matter research

    NASA Astrophysics Data System (ADS)

    Vivanco, R.; Ghiglino, A.; de Vicente, J. P.; Sordo, F.; Terrón, S.; Magán, M.; Perlado, J. M.; Bermejo, F. J.

    2014-12-01

    A model for an accelerator-driven subcritical system to be operated as a source of cold neutrons for Condensed Matter research is developed at the conceptual level. Its baseline layout relies upon proven accelerator, spalattion target and fuel array technologies, and consists in a proton accelerator able to deliver some 67.5 mA of proton beam with kinetic energy 0.6 GeV, a pulse length of 2.86 ms, and repetition rate of 14 Hz. The particle beam hits a target of conventional design that is surrounded by a multiplicative core made of fissile/fertile material, composed by a subcritical array of fuel bars made of aluminium Cermet cooled by light water poisoned with boric acid. Relatively low enriched uranium is chosen as fissile material. An optimisation of several parameters is carried out, using as components of the objective function several characteristics pertaining the cold neutron pulse. The results show that the optimal device will deliver up to 80% of the cold neutron flux expected for some of the ongoing projects using a significantly lower proton beam power than that managed in such projects. The total power developed within the core rises up to 22.8 MW, and the criticality range shifts to a final keff value of around 0.9 after the 50 days cycle.

  5. Monte Carlo Modeling of Fast Sub-critical Assembly with MOX Fuel for Research of Accelerator-Driven Systems

    NASA Astrophysics Data System (ADS)

    Polanski, A.; Barashenkov, V.; Puzynin, I.; Rakhno, I.; Sissakian, A.

    It is considered a sub-critical assembly driven with existing 660 MeV JINR proton accelerator. The assembly consists of a central cylindrical lead target surrounded with a mixed-oxide (MOX) fuel (PuO2 + UO2) and with reflector made of beryllium. Dependence of the energetic gain on the proton energy, the neutron multiplication coefficient, and the neutron energetic spectra have been calculated. It is shown that for subcritical assembly with a mixed-oxide (MOX) BN-600 fuel (28%PuO 2 + 72%UO2) with effective density of fuel material equal to 9 g/cm 3 , the multiplication coefficient keff is equal to 0.945, the energetic gain is equal to 27, and the neutron flux density is 1012 cm˜2 s˜x for the protons with energy of 660 MeV and accelerator beam current of 1 uA.

  6. Materials Testing for an Accelerator-Driven Subcritical Molten Salt Fission System: A look at the Materials Science of Molten Salt Corrosion

    NASA Astrophysics Data System (ADS)

    Sooby, Elizabeth; Balachandran, Shreyas; Foley, David; Hartwig, Karl; McIntyre, Peter; Phongikaroon, Supathorn; Pogue, Nathaniel; Simpson, Michael; Tripathy, Prabhat

    2011-10-01

    For an accelerator-driven subcritical molten salt fission core to survive its 50+ year fuel life, the primary vessel, heat exchanger, and various internal components must be made of materials that resist corrosion and radiation damage in a high-temperature environment, (500-800 C). An experimental study of the corrosion behavior of candidate metals in contact with molten salt is being conducted at the Center for Advanced Energy Studies. Initial experiments have been run on Nb, Ta, Ni, two zirconium alloys, Hastelloy-N, and a series of steel alloys to form a base line for corrosion in both chloride and bromide salt. Metal coupons were immersed in LiCl-KCl or LiBr-KBr at 700 C in an inert-atmosphere. Salt samples were extracted on a time schedule over a 24-hr period. The samples were analyzed using inductively coupled plasma-mass spectrometry to determine concentrations of metals from corrosion. Preliminary results will be presented.

  7. Reactor Dynamics Experiments with a Sub-Critical Assembly

    SciTech Connect

    Miley, G.H.; Yang, Y.; Wu, L.; Momota, H.

    2004-10-06

    A resurgence in use of nuclear power is now underway worldwide. However due to the shutdown of many university research reactors , student laboratories must rely more heavily on use of sub-critical assemblies. Here a driven sub-critical is described that uses a cylindrical Inertial Electrostatic Confinement (IEC) device to provide a fusion neutron source. The small IEC neutron source would be inserted in a fuel element position, with its power input controlled externally at a control panel. This feature opens the way to use of the critical assembly for a number of transient experiments such as sub-critical pulsing and neutron wave propagation. That in turn adds important new insights and excitement for the student teaching laboratory.

  8. THE ENEA ADS PROJECT:. Accelerator Driven System Prototype R&D and Industrial Program

    NASA Astrophysics Data System (ADS)

    Gherardi, Giuseppe

    2001-11-01

    Hybrid reactors (Accelerator Driven Sub-critical Systems, ADS), coupling an accelerator with a target and a sub-critical reactor, could simultaneously burn minor actinides and transmute long-lived fission products, while producing a consistent amount of electrical energy. A group of Italian research and development (R&D) organizations and industries have set up a team, which is studying the design issues related to the construction of an 80 MWth Experimental Facility. The planned activities and the (tentative) time schedule of the Italian program are presented.

  9. Preliminary design concept of a subcritical reactor using available resources

    SciTech Connect

    Churnetski, E.L.; Hoyny, V.; Chaudhuri, B.R.; Taprantzis, A.; Yavas, A.

    1993-12-31

    During the Fall 1993 semester, a project was initiated within the Nuclear Engineering Department of the University of Tennessee with the objective of developing a design for a subcritical reactor with maximized multiplication factor using materials currently available. Such a device, if constructed, would serve as a teaching tool for the Department of Nuclear Engineering. Design work was conducted as a large number of computer calculations, with trial pile configurations based on fundamental nuclear engineering principles, in an effort to maximize multiplication factor through fuel element geometry, moderator type, fissile/moderator ratio, and reflector character. The principal objective of the design group for the early phase of this project was to present several possible ``baseline`` reactor designs and identify directions for improvements. For the sake of calculational ease, the cores analyzes to date have been of nearly cubic shape. The SCALE CSAS25 software which runs KENO.Va, a Monte Carlo code, was used for all neutronics calculations. The baseline reactors resulting from work to date are cuboidal in shape and graphite reflected. Two types of fuel element geometries are proposed, a typical triangular pitch rod lattice and an arrangement of discrete fuel slugs placed in a lattice corresponding to body centered cubic packing. The latter arrangement provides slightly higher multiplication factors than the former. Calculations were performed for both graphite and heavy water moderation with heavy water moderation producing considerably higher multiplication factors, as expected. In general, the maximum k{sub eff} for the reactors are in the range of 0.5 to 0.9, well subcritical, except in the cases of the extreme possible values of fuel assay where critical configurations are possible. In these cases, designs with reduced fuel loading are recommended to assure a subcritical multiplication factor.

  10. Accelerator-driven Transmutation of Waste

    NASA Astrophysics Data System (ADS)

    Venneri, Francesco

    1998-04-01

    Nuclear waste from commercial power plants contains large quantities of plutonium, other fissionable actinides, and long-lived fission products that are potential proliferation concerns and create challenges for the long-term storage. Different strategies for dealing with nuclear waste are being followed by various countries because of their geologic situations and their views on nuclear energy, reprocessing and non-proliferation. The current United States policy is to store unprocessed spent reactor fuel in a geologic repository. Other countries are opting for treatment of nuclear waste, including partial utilization of the fissile material contained in the spent fuel, prior to geologic storage. Long-term uncertainties are hampering the acceptability and eventual licensing of a geologic repository for nuclear spent fuel in the US, and driving up its cost. The greatest concerns are with the potential for radiation release and exposure from the spent fuel for tens of thousands of years and the possible diversion and use of the actinides contained in the waste for weapons construction. Taking advantage of the recent breakthroughs in accelerator technology and of the natural flexibility of subcritical systems, the Accelerator-driven Transmutation of Waste (ATW) concept offers the United States and other countries the possibility to greatly reduce plutonium, higher actinides and environmentally hazardous fission products from the waste stream destined for permanent storage. ATW does not eliminate the need for, but instead enhances the viability of permanent waste repositories. Far from being limited to waste destruction, the ATW concept also brings to the table new technologies that could be relevant for next-generation power producing reactors. In the ATW concept, spent fuel would be shipped to the ATW site where the plutonium, transuranics and selected long-lived fission products would be destroyed by fission or transmutation in their first and only pass through the

  11. Accelerator Driven Nuclear Energy: The Thorium Option

    ScienceCinema

    Raja, Rajendran

    2016-07-12

    Conventional nuclear reactors use enriched Uranium as fuel and produce nuclear waste which needs to be stored away for over 10,000 years.   At the current rate of use, existing sources of Uranium will last for 50-100 years.  We describe a solution to the problem that uses particle accelerators to produce fast neutrons that can be used to burn existing nuclear waste and produce energy.  Such systems, initially proposed by Carlo Rubbia and collaborators in the 1990's, are being seriously considered by many countries as a possible solution to the green energy problem.  Accelerator driven reactors operate in a sub-critical regime and, thus, are safer and can obtain energy from plentiful elements such as Thorium-232 and Uranium-238. What is missing is the high intensity (10MW) accelerator that produces 1 GeV protons. We will describe scenarios which if implemented will make such systems a reality.  

  12. Prompt nuclear analytical techniques for material research in accelerator driven transmutation technologies: Prospects and quantitative analyses

    NASA Astrophysics Data System (ADS)

    Vacík, J.; Hnatowicz, V.; Červená, J.; Peřina, V.; Mach, R.; Peka, I.

    1998-04-01

    Accelerator driven transmutation technology (ADTT) is a promissing way toward liquidation of spent nuclear fuel, nuclear wastes and weapon grade Pu. The ADTT facility comprises a high current (proton) accelerator supplying a subcritical reactor assembly with spallation neutrons. The reactor part is supposed to be cooled by molten fluorides or metals which serve, at the same time, as a carrier of nuclear fuel. Assumed high working temperature (400-600°C) and high radiation load in the subcritical reactor and spallation neutron source put forward the problem of optimal choice of ADTT construction materials, especially from the point of their radiation and corrosion resistance when in contact with liquid working media. The use of prompt nuclear analytical techniques in ADTT related material research is considered and examples of preliminary analytical results obtained using neutron depth profiling method are shown for illustration.

  13. The physics design of accelerator-driven transmutation systems

    SciTech Connect

    Venneri, F.

    1995-10-01

    Nuclear systems under study in the Los Alamos Accelerator-Driven Transmutation Technology program (ADTT) will allow the destruction of nuclear spent fuel and weapons-return plutonium, as well as the production of nuclear energy from the thorium cycle, without a long-lived radioactive waste stream. The subcritical systems proposed represent a radical departure from traditional nuclear concepts (reactors), yet the actual implementation of ADTT systems is based on modest extrapolations of existing technology. These systems strive to keep the best that the nuclear technology has developed over the years, within a sensible conservative design envelope and eventually manage to offer a safe, less expensive and more environmentally sound approach to nuclear power.

  14. The physics design of accelerator-driven transmutation systems

    SciTech Connect

    Venneri, F.

    1995-02-01

    Nuclear systems under study in the Los Alamos Accelerator-Driven Transmutation Technology program (ADTT) will allow the destruction of nuclear spent fuel and weapons-return plutonium, as well as the production of nuclear energy from the thorium cycle, without a long-lived radioactive waste stream. The subcritical systems proposed represent a radical departure from traditional nuclear concepts (reactors), yet the actual implementation of ADTT systems is based on modest extrapolations of existing technology. These systems strive to keep the best that the nuclear technology has developed over the years, within a sensible conservative design envelope and eventually manage to offer a safer, less expensive and more environmentally sound approach to nuclear power.

  15. A fuel for sub-critical fast reactor

    SciTech Connect

    Moiseenko, V. E.; Chernitskiy, S. V.; Agren, O.; Noack, K.

    2012-06-19

    Along with the problem of the nuclear waste transmutation, the problem of minimization of waste production is of current interest. It is not possible to eliminate production of waste at a nuclear power plant, but, as is shown in this report, it is in principle possible to arrange a fuel composition with no net production of transuranic elements. The idea is to find the transuranic elements composition to which the depleted uranium is continuously supplied during frequent reprocessing, and amount of each other transuranic fuel component remains unchanged in time. For each transuranic component, the balance is achieved by equating burnup and production rates. The production is due to neutron capture by the neighboring lighter isotope and subsequent beta-decay. The burnup includes fission, neutron capture and decays. For the calculations a simplified burnup model which accounts for 9 isotopes of uranium, neptunium, plutonium and americium is used. The calculated fuel composition consists mainly of uranium with minority of plutonium isotopes. Such a fuel, after usage in a sub-critical fast reactor, should be reprocessed. The fission product content increases during burnup, representing a net production of waste, while the transuranic elements and {sup 238}U should be recycled into a new fuel. For such a fuel cycle, the net consumption is only for 238U, and the net waste production is just fission products.

  16. A fuel for sub-critical fast reactor

    NASA Astrophysics Data System (ADS)

    Moiseenko, V. E.; Chernitskiy, S. V.; Ågren, O.; Noack, K.

    2012-06-01

    Along with the problem of the nuclear waste transmutation, the problem of minimization of waste production is of current interest. It is not possible to eliminate production of waste at a nuclear power plant, but, as is shown in this report, it is in principle possible to arrange a fuel composition with no net production of transuranic elements. The idea is to find the transuranic elements composition to which the depleted uranium is continuously supplied during frequent reprocessing, and amount of each other transuranic fuel component remains unchanged in time. For each transuranic component, the balance is achieved by equating burnup and production rates. The production is due to neutron capture by the neighboring lighter isotope and subsequent beta-decay. The burnup includes fission, neutron capture and decays. For the calculations a simplified burnup model which accounts for 9 isotopes of uranium, neptunium, plutonium and americium is used. The calculated fuel composition consists mainly of uranium with minority of plutonium isotopes. Such a fuel, after usage in a sub-critical fast reactor, should be reprocessed. The fission product content increases during burnup, representing a net production of waste, while the transuranic elements and 238U should be recycled into a new fuel. For such a fuel cycle, the net consumption is only for 238U, and the net waste production is just fission products.

  17. Development and analysis of a metal-fueled accelerator-driven burner

    SciTech Connect

    Lypsch, F.; Hill, R.N.

    1994-08-01

    The purpose of this paper is to compare the safety characteristics of an accelerator driven metal fueled fast system to a critical core on a consistent basis to determine how these characteristics are affected solely by subcritically of the system. To accomplish this an accelerator proton beam/tungsten neutron source model is surrounded by a subcritical blanket using metallic fuel and sodium as coolant. The consequences of typical accident transients, namely unprotected transient overpower (TOP), loss of heat sink (LOHS), and loss of flow (LOP) were calculated for the hybrid system and compared to corresponding results for a metal-fueled fast reactor. Results indicate that the subcritical system exhibits superior performance for TOP (reactivity-induced) transits; however, only in the critical system are reactivity feedbacks able to cause passive shutdown in the LOHS ad LOP events. Therefore, for a full spectrum of accident initiators considered, the overall safety behavior of accelerator-driven metal-fueled systems can neither be concluded to be worse nor to be better than advanced reactor designs which rely on passive safety features.

  18. Reduction of the Radiotoxicity of Spent Nuclear Fuel Using a Two-Tiered System Comprising Light Water Reactors and Accelerator-Driven Systems

    SciTech Connect

    Trellue, Holly R.

    2003-06-01

    Two main issues regarding the disposal of spent nuclear fuel from nuclear reactors in the United States in the geological repository Yucca Mountain are: (1) Yucca Mountain is not designed to hold the amount of fuel that has been and is proposed to be generated in the next few decades, and (2) the radiotoxicity (i.e., biological hazard) of the waste (particularly the actinides) does not decrease below that of natural uranium ore for hundreds of thousands of years. One solution to these problems may be to use transmutation to convert the nuclides in spent nuclear fuel to ones with shorter half-lives. Both reactor and accelerator-based systems have been examined in the past for transmutation; there are advantages and disadvantages associated with each. By using existing Light Water Reactors (LWRs) to burn a majority of the plutonium in spent nuclear fuel and Accelerator-Driven Systems (ADSs) to transmute the remainder of the actinides, the benefits of each type of system can be realized. The transmutation process then becomes more efficient and less expensive. This research searched for the best combination of LWRs with multiple recycling of plutonium and ADSs to transmute spent nuclear fuel from past and projected nuclear activities (assuming little growth of nuclear energy). The neutronic design of each system is examined in detail although thermal hydraulic performance would have to be considered before a final system is designed. The results are obtained using the Monte Carlo burnup code Monteburns, which has been successfully benchmarked for MOX fuel irradiation and compared to other codes for ADS calculations. The best combination of systems found in this research includes 41 LWRs burning mixed oxide fuel with two recycles of plutonium (~40 years operation each) and 53 ADSs to transmute the remainder of the actinides from spent nuclear fuel over the course of 60 years of operation.

  19. Application of Burnable Absorbers in an Accelerator-Driven System

    SciTech Connect

    Wallenius, Jan; Tucek, Kamil; Carlsson, Johan; Gudowski, Waclaw

    2001-01-15

    The application of burnable absorbers (BAs) to minimize power peaking, reactivity loss, and capture-to-fission probabilities in an accelerator-driven waste transmutation system has been investigated. Boron-10-enriched B{sub 4}C absorber rods were introduced into a lead-bismuth-cooled core fueled with transuranic (TRU) discharges from light water reactors to achieve the smallest possible power peakings at beginning-of-life (BOL) subcriticality level of 0.97. Detailed Monte Carlo simulations show that a radial power peaking equal to 1.2 at BOL is attainable using a four-zone differentiation in BA content. Using a newly written Monte Carlo burnup code, reactivity losses were calculated to be 640 pcm per percent TRU burnup for unrecycled TRU discharges. Comparing to corresponding values in BA-free cores, BA introduction diminishes reactivity losses in TRU-fueled subcritical cores by {approx}20%. Radial power peaking after 300 days of operation at 1200-MW thermal power was <1.75 at a subcriticality level of {approx}0.92, which appears to be acceptable, with respect to limitations in cladding and fuel temperatures. In addition, the use of BAs yields significantly higher fission-to-capture probabilities in even-neutron-number nuclides. Fission-to-absorption probability ratio for {sup 241}Am equal to 0.33 was achieved in the configuration studied. Hence, production of the strong alpha-emitter {sup 242}Cm is reduced, leading to smaller fuel-swelling rates and pin pressurization. Disadvantages following BA introduction, such as increase of void worth and decrease of Doppler feedback in conjunction with small values of {beta}{sub eff}, need to be addressed by detailed studies of subcritical core dynamics.

  20. Monte Carlo Modeling of Electronuclear Processes in Experimental Accelerator Driven Systems

    NASA Astrophysics Data System (ADS)

    Polanski, Aleksander

    2000-01-01

    The paper presents results of Monte Carlo modeling of an experimental Accelerator Driven System (ADS), which employs a subcritical assembly and a 660 MeV proton accelerator operating at the Laboratory of Nuclear Problems of the Joint Institute for Nuclear Research in Dubna. The mix of oxides (PuO2 + UO2) MOX fuel designed for the reactor will be adopted for the core of the assembly. The present conceptual design of the experimental subcritical assembly in Dubna is based on the core with a nominal unit capacity of 30 kW (thermal). This corresponds to the multiplication coefficient keff= 0.945 and the accelerator beam power of 1 kW.

  1. Development of reactivity feedback effect measurement techniques under sub-critical condition in fast reactors

    SciTech Connect

    Kitano, A.; Nishi, H.; Suzuki, T.; Okajima, S.; Kanemoto, S.

    2012-07-01

    The first-of-a-kind reactor has been licensed by a safety examination of the plant design based on the measured data in precedent mock-up experiments. The validity of the safety design can be confirmed without a mock-up experiment, if the reactor feed-back characteristics can be measured before operation, with the constructed reactor itself. The 'Synthesis Method', a systematic and sophisticated method of sub-criticality measurement, is proposed in this work to ensure the safety margin before operation. The 'Synthesis Method' is based on the modified source multiplication method (MSM) combined with the noise analysis method to measure the reference sub-criticality level for MSM. A numerical simulation for the control-rod reactivity worth and the isothermal feed-back reactivity was conducted for typical fast reactors of 100 MWe-size, 300 MWe-size, 750 MWe-size, and 1500 MWe-size to investigate the applicability of Synthesis Method. The number of neutron detectors and their positions necessary for the measurement were investigated for both methods of MSM and the noise analysis by a series of parametric survey calculations. As a result, it was suggested that a neutron detector located above the core center and three or more neutron detectors located above the radial blanket region enable the measurement of sub-criticality within 10% uncertainty from -$0.5 to -$2 and within 15% uncertainty for the deeper sub-criticality. (authors)

  2. An alternative experimental approach for subcritical configurations of the IPEN/MB-01 nuclear reactor

    NASA Astrophysics Data System (ADS)

    Gonnelli, E.; Lee, S. M.; Pinto, L. N.; Landim, H. R.; Diniz, R.; Jerez, R.; dos Santos, A.

    2015-07-01

    This work presents an alternative approach for the reactivity worth experiments analysis in the IPEN/MB-01 reactor considering highly subcritical arrays. In order to reach the subcritical levels, the removal of a specific number of fuel rods is proposed. Twenty three configurations were carried out for this purpose. The control bank insertion experiment was used only as reference for the fuel rod experiment and, in addition, the control banks were maintained completely withdrawn during all the fuel rods experiment. The theoretical simulation results using the MCNP5 code and the ENDF/B-VII.0 library neutron data are in a very good agreement to experimental results.

  3. The use of linear superconducting electron accelerator for subcritical reactor driving

    NASA Astrophysics Data System (ADS)

    Guk, I. S.; Dovbnya, A. N.; Kononenko, S. G.; Peev, F. A.; Tarasenko, A. S.; van der Wiel, M.; Botman, J. I. M.

    2008-12-01

    At the National Science Centre, Kharkiv Institute of Physics and Technology (NSC KIPT) the possibility of creating an installation with a subcritical reactor driven by an electron accelerator is examined. To obtain the maximal stream of neutrons from a neutron-producing target at a minimal density of energy emission, the electron energy should be in the range of 100-200 MeV and the size of the target should be as large as possible. Other important requirements are beam continuity with time and long-term stability of the accelerator parameters. The variants of using the superconducting linear accelerator on the basis of a TESLA accelerating structure as of subcritical reactor driver are considered. The basic design parameters and characteristics of this installation are presented.

  4. LBE water interaction in sub-critical reactors: First experimental and modelling results

    NASA Astrophysics Data System (ADS)

    Ciampichetti, A.; Agostini, P.; Benamati, G.; Bandini, G.; Pellini, D.; Forgione, N.; Oriolo, F.; Ambrosini, W.

    2008-06-01

    This paper concerns the study of the phenomena involved in the interaction between LBE and pressurised water which could occur in some hypothetical accidents in accelerator driven system type reactors. The LIFUS 5 facility was designed and built at ENEA-Brasimone to reproduce this kind of interaction in a wide range of conditions. The first test of the experimental program was carried out injecting water at 70 bar and 235 °C in a reaction vessel containing LBE at 1 bar and 350 °C. A pressurisation up to 80 bar was observed in the test section during the considered transient. The SIMMER III code was used to simulate the performed test. The calculated data agree in a satisfactory way with the experimental results giving confidence in the possibility to use this code for safety analyses of heavy liquid metal cooled reactors.

  5. Measurements of the subcriticality using advanced technique of shooting source during operation of NPP reactors

    NASA Astrophysics Data System (ADS)

    Lebedev, G. V.; Petrov, V. V.; Bobylyov, V. T.; Butov, R. I.; Zhukov, A. M.; Sladkov, A. A.

    2014-12-01

    According to the rules of nuclear safety, the measurements of the subcriticality of reactors should be carried out in the process of performing nuclear hazardous operations. An advanced technique of shooting source of neutrons is proposed to meet this requirement. As such a source, a pulsed neutron source (PNS) is used. In order to realize this technique, it is recommended to enable a PNS with a frequency of 1-20 Hz. The PNS is stopped after achieving a steady-state (on average) number of neutrons in the reactor volume. The change in the number of neutrons in the reactor volume is measured in time with an interval of discreteness of ˜0.1 s. The results of these measurements with the application of a system of point-kinetics equations are used in order to calculate the sought subcriticality. The basic idea of the proposed technique used to measure the subcriticality is elaborated in a series of experiments on the Kvant assembly. The conditions which should be implemented in order to obtain a positive result of measurements are formulated. A block diagram of the basic version of the experimental setup is presented, whose main element is a pulsed neutron generator.

  6. Measurements of the subcriticality using advanced technique of shooting source during operation of NPP reactors

    SciTech Connect

    Lebedev, G. V. Petrov, V. V.; Bobylyov, V. T.; Butov, R. I.; Zhukov, A. M.; Sladkov, A. A.

    2014-12-15

    According to the rules of nuclear safety, the measurements of the subcriticality of reactors should be carried out in the process of performing nuclear hazardous operations. An advanced technique of shooting source of neutrons is proposed to meet this requirement. As such a source, a pulsed neutron source (PNS) is used. In order to realize this technique, it is recommended to enable a PNS with a frequency of 1–20 Hz. The PNS is stopped after achieving a steady-state (on average) number of neutrons in the reactor volume. The change in the number of neutrons in the reactor volume is measured in time with an interval of discreteness of ∼0.1 s. The results of these measurements with the application of a system of point-kinetics equations are used in order to calculate the sought subcriticality. The basic idea of the proposed technique used to measure the subcriticality is elaborated in a series of experiments on the Kvant assembly. The conditions which should be implemented in order to obtain a positive result of measurements are formulated. A block diagram of the basic version of the experimental setup is presented, whose main element is a pulsed neutron generator.

  7. Accelerator-driven assembly for plutonium transformation (ADAPT)

    NASA Astrophysics Data System (ADS)

    Tuyle, Greorgy J. Van; Todosow, Michael; Powell, James; Schweitzer, Donald

    1995-01-01

    A particle accelerator-driven spallation target and corresponding blanket region are proposed for the ultimate disposition of weapons-grade plutonium being retired from excess nuclear weapons in the U.S. and Russia. The highly fissle plutonium is contained within .25 to .5 cm diameter silicon-carbide coated graphite beads, which are cooled by helium, within the slightly subcritical blanket region. Major advantages include very high one-pass burnup (over 90%), a high integrity waste form (the coated beads), and operation in a subcritical mode, thereby minimizing the vulnerability to the positive reativity feedbacks often associated with plutonium fuel.

  8. A Subcritical, Gas-Cooled Fast Transmutation Reactor with a Fusion Neutron Source

    SciTech Connect

    Stacey, W.M.; Beavers, V.L.; Casino, W.A.; Cheatham, J.R.; Friis, Z.W.; Green, R.D.; Hamilton, W.R.; Haufler, K.W.; Hutchinson, J.D.; Lackey, W.J.; Lorio, R.A.; Maddox, J.W.; Mandrekas, J.; Manzoor, A.A.; Noelke, C.A.; Oliveira, C. de; Park, M.; Tedder, D.W.; Terry, M.R.; Hoffman, E.A.

    2005-05-15

    A design is presented for a subcritical, He-cooled fast reactor, driven by a tokamak D-T fusion neutron source, for the transmutation of spent nuclear fuel (SNF). The reactor is fueled with coated transuranic (TRU) particles and is intended for the deep-burn (>90%) transmutation of the TRUs in SNF without reprocessing of the coated fuel particles. The reactor design is based on the materials, fuel, and separations technologies under near-term development in the U.S. Department of Energy (DOE) Nuclear Energy Program and on the plasma physics and fusion technologies under near-term development in the DOE Fusion Energy Sciences Program, with the objective of intermediate-term ({approx}2040) deployment. The physical and performance characteristics and research and development requirements of such a reactor are described.

  9. Feasibility study of noise analysis methods on virtual thermal reactor subcriticality monitoring

    SciTech Connect

    Kong, C.; Lee, D.; Lee, E.

    2013-07-01

    This paper presents the analysis results of Rossi-alpha, cross-correlation, Feynman-alpha, and Feynman difference methods applied to the subcriticality monitoring of nuclear reactors. A thermal spectrum Godiva model has been designed for the analysis of the four methods. This Godiva geometry consists of a spherical core containing the isotopes of H-l, U-235 and U-238, and the H{sub 2}O reflector outside the core. A Monte Carlo code, McCARD, is used in real time mode to generate virtual detector signals to analyze the feasibility of the four methods. The analysis results indicate that the four methods can be used with high accuracy for the continuous monitoring of subcriticality. In addition to that, in order to analyze the impact of the random noise contamination on the accuracy of the noise analysis, the McCARD-generated signals are contaminated with arbitrary noise. It is noticed that, even when the detector signals are contaminated, the four methods can predict the subcriticality with reasonable accuracy. Nonetheless, in order to reduce the adverse impact of the random noise, eight detector signals, rather than a single signal, are generated from the core, one signal from each equally divided eighth part of the core. The preliminary analysis with multiple virtual detector signals indicates that the approach of using many detectors is promising to improve the accuracy of criticality prediction and further study will be performed in this regard. (authors)

  10. Optimization of accelerator-driven technology for LWR waste transmutation

    SciTech Connect

    Bowman, C.D.

    1996-12-31

    The role of accelerator-driven transmutation technology is examined in the context of the destruction of actinide waste from commercial light water reactors. It is pointed out that the commercial plutonium is much easier to use for entry-level nuclear weapons than weapons plutonium. Since commercial plutonium is easier to use, since there is very much more of it already, and since it is growing rapidly, the permanent disposition of commercial plutonium is an issue of greater importance than weapons plutonium. The minor actinides inventory, which may be influenced by transmutation, is compared in terms of nuclear properties with commercial and weapons plutonium and for possible utility as weapons material. Fast and thermal spectrum systems are compared as means for destruction of plutonium and the minor actinides. it is shown that the equilibrium fast spectrum actinide inventory is about 100 times larger than for thermal spectrum systems, and that there is about 100 times more weapons-usable material in the fast spectrum system inventory compared to the thermal spectrum system. Finally it is shown that the accelerator size for transmutation can be substantially reduced by design which uses the accelerator-produced neutrons only to initiate the unsustained fission chains characteristic of the subcritical system. The analysis argues for devoting primary attention to the development of thermal spectrum transmutation technology. A thermal spectrum transmuter operating at a fission power of 750-MWth fission power, which is sufficient to destroy the actinide waste from one 3,000-MWth light water reactor, may be driven by a proton beam of 1 GeV energy and a current of 7 mA. This accelerator is within the range of realizable cyclotron technology and is also near the size contemplated for the next generation spallation neutron source under consideration by the US, Europe, and Japan.

  11. The procedure and results of calculations of the equilibrium isotopic composition of a demonstration subcritical molten salt reactor

    NASA Astrophysics Data System (ADS)

    Nevinitsa, V. A.; Dudnikov, A. A.; Blandinskiy, V. Yu.; Balanin, A. L.; Alekseev, P. N.; Titarenko, Yu. E.; Batyaev, V. F.; Pavlov, K. V.; Titarenko, A. Yu.

    2015-12-01

    A subcritical molten salt reactor with an external neutron source is studied computationally as a facility for incineration and transmutation of minor actinides from spent nuclear fuel of reactors of VVER-1000 type and for producing 233U from 232Th. The reactor configuration is chosen, the requirements to be imposed on the external neutron source are formulated, and the equilibrium isotopic composition of heavy nuclides and the key parameters of the fuel cycle are calculated.

  12. The procedure and results of calculations of the equilibrium isotopic composition of a demonstration subcritical molten salt reactor

    SciTech Connect

    Nevinitsa, V. A. Dudnikov, A. A.; Blandinskiy, V. Yu.; Balanin, A. L.; Alekseev, P. N.; Titarenko, Yu. E.; Batyaev, V. F.; Pavlov, K. V.; Titarenko, A. Yu.

    2015-12-15

    A subcritical molten salt reactor with an external neutron source is studied computationally as a facility for incineration and transmutation of minor actinides from spent nuclear fuel of reactors of VVER-1000 type and for producing {sup 233}U from {sup 232}Th. The reactor configuration is chosen, the requirements to be imposed on the external neutron source are formulated, and the equilibrium isotopic composition of heavy nuclides and the key parameters of the fuel cycle are calculated.

  13. Safety features of subcritical fluid fueled systems

    SciTech Connect

    Bell, C.R.

    1995-10-01

    Accelerator-driven transmutation technology has been under study at Los Alamos for several years for application to nuclear waste treatment, tritium production, energy generation, and recently, to the disposition of excess weapons plutonium. Studies and evaluations performed to date at Los Alamos have led to a current focus on a fluid-fuel, fission system operating in a neutron source-supported subcritical mode, using molten salt reactor technology and accelerator-driven proton-neutron spallation. In this paper, the safety features and characteristics of such systems are explored from the perspective of the fundamental nuclear safety objectives that any reactor-type system should address. This exploration is qualitative in nature and uses current vintage solid-fueled reactors as a baseline for comparison. Based on the safety perspectives presented, such systems should be capable of meeting the fundamental nuclear safety objectives. In addition, they should be able to provide the safety robustness desired for advanced reactors. However, the manner in which safety objectives and robustness are achieved is very different from that associated with conventional reactors. Also, there are a number of safety design and operational challenges that will have to be addressed for the safety potential of such systems to be credible.

  14. Thermal-Hydraulic Analyses of the Submersion-Subcritical Safe Space (S and 4) Reactor

    SciTech Connect

    King, Jeffrey C.; El-Genk, Mohamed S.

    2007-01-30

    Detailed thermal-hydraulic analyses of the S and 4 reactor are performed to reduce the maximum fuel temperature of the Submersion-Subcritical Safe Space (S and 4) reactor to below 1300 K. The fuel pellet diameter is reduced from 1.315 cm to 1.25 cm, decreasing the thermal resistance of the pellets and each of the 1.54 cm diameter coolant channels in the reactor core are replaced with several 0.3 cm ID channels to increase the effective heat transfer area and to encourage mixing of the flowing helium-28% xenon coolant. The calculated maximum fuel temperature decreased from more than 1900 K to 1302 K and the relative pressure drop across the reactor core increased from 1.98% to 2.57% of the inlet pressure. Moving the concentric inlet and outlet pipes 1 cm towards the center of the reactor core encouraged more flow through the center region, further reducing the maximum fuel temperature by 14 degrees to 1288 K, with a negligible effect on the core pressure losses.

  15. Analysis of subcritical experiments using fresh and spent research reactor fuel assemblies

    NASA Astrophysics Data System (ADS)

    Zino, John Frederick

    1999-11-01

    This research investigated the concepts associated with crediting the burnup of spent nuclear fuel assemblies for the purposes of criticality safety. To accomplish this, a collaborative experimental research program was undertaken between Westinghouse, the University of Missouri Research Reactor (MURR) facility and Oak Ridge National Laboratory (ORNL). The purpose of the program was to characterize the subcritical behavior of a small array of fresh and spent MURR fuel assemblies using the 252Cf Source-driven noise technique. An aluminum test rig was built which was capable of holding up to four, highly enriched (93.15 wt.% 235U) MURR fuel assemblies in a 2 x 2 array. The rig was outfitted with one source and four detector drywells which allowed researchers to perform active neutron noise measurements on the array of fuel assemblies. The 1 atmosphere gas 3He neutron detectors used to perform the measurements were quenched with CF4 gas to allow improved discrimination of the neutron signals in the very high gamma-ray fields associated with spent fuel (˜8000 R/hr). In addition, the detector drywells were outfitted with 1″ lead collars to provide additional gamma-ray shielding from the spent fuel. Reactivity changes were induced in the subcritical lattice by replacing individual fresh assemblies (in a 4-assembly array) with spent assemblies of known, maximum burnup (143 Mw-D). The absolute and relative measured reactivity changes were then compared to those predicted by three-dimensional Monte Carlo calculations. The purpose of these comparisons was to investigate the accuracy of modern transport theory depletion calculations to accurately simulate the reactivity effects of burnup in spent nuclear fuel. A total of seven subcritical measurements were performed at the MURR reactor facility on July 20th and 27th, 1998. These measurements generated several estimates of prompt neutron decay constants (alpha) and ratios of spectral densities through frequency correlations

  16. Hydrolysis of polycarbonate in sub-critical water in fused silica capillary reactor with in situ Raman spectroscopy

    USGS Publications Warehouse

    Pan, Z.; Chou, I.-Ming; Burruss, R.C.

    2009-01-01

    The advantages of using fused silica capillary reactor (FSCR) instead of conventional autoclave for studying chemical reactions at elevated pressure and temperature conditions were demonstrated in this study, including the allowance for visual observation under a microscope and in situ Raman spectroscopic characterization of polycarbonate and coexisting phases during hydrolysis in subcritical water. ?? 2009 The Royal Society of Chemistry.

  17. Investigation of Lead Target Nuclei Used on Accelerator-Driven Systems for Tritium Production

    NASA Astrophysics Data System (ADS)

    Tel, E.; Aydin, A.

    2012-02-01

    High-current proton accelerators are being researched at Los Alamos National Laboratory and other laboratories for accelerator production of tritium, transmuting long-lived radioactive waste into shorter-lived products, converting excess plutonium, and producing energy. These technologies make use of spallation neutrons produced in ( p,xn) and ( n,xn) nuclear reactions on high-Z targets. Through ( p,xn) and ( n,xn) nuclear reactions, neutrons are produced and are moderated by heavy water. These moderated neutrons are subsequently captured on 3He to produce tritium via the ( n,p) reaction. Tritium self-sufficiency must be maintained for a commercial fusion power plant. Rubbia succeeded in a proposal of a full scale demonstration plant of the Energy Amplifier. This plant is to be known the accelerator-driven system (ADS). The ADS can be used for production of neutrons in spallation neutron source and they can act as an intense neutron source in accelerator-driven subcritical reactors, capable of incinerating nuclear waste and of producing energy. Thorium and Uranium are nuclear fuels and Lead, Bismuth, Tungsten are the target nuclei in these reactor systems. The spallation targets can be Pb, Bi, W, etc. isotopes and these target material can be liquid or solid. Naturally Lead includes the 204Pb (%1.42), 206Pb (%24.1), 207Pb (%22.1) and 208Pb (%52.3) isotopes. The design of ADS systems and also a fusion-fission hybrid reactor systems require the knowledge of a wide range of better data. In this study, by using Hartree-Fock method with an effective nucleon-nucleon Skyrme interactions rms nuclear charge radii, rms nuclear mass radii, rms nuclear proton, neutron radii and neutron skin thickness were calculated for the 204, 206, 208Pb isotopes . The calculated results have been compared with those of the compiled experimental and theoretical values of other studies.

  18. Detection rate evaluation of ex-core detectors in the subcritical OPR-1000 reactor

    SciTech Connect

    Won, B. H.; Shin, C. H.; Kim, S. H.; Kim, H. C.; Park, J. J.; Kim, J. K.

    2012-07-01

    The OPR-1000 is a PWR reactor developed in Korea. One-type ex-core detectors for monitoring of power distributions were installed in the OPR-1000 reactor to alternate the three-types of the ex-core detectors. For the verification of the detection performances, neutron transport calculation was performed by using MCNP5 code. The reaction rate in the ex-core detectors and the neutron flux were evaluated by using MCNP5 code as changing the boron concentration from 1800 ppm to 1122 ppm in the subcritical condition. The reaction rate results in fission chamber show that minimum and maximum values are 0.03577 and 3.33563 reactions/cm{sup 3}-sec, respectively. This study can be directly used for the verification and improvement of fission chamber performance in using one-type ex-core detector. Also, it can be utilized for the production of the reference data in determining neutron source strength. It is expected the proposed simulation method can be utilized to the improvement of the dose monitoring system. (authors)

  19. Simulator for an Accelerator-Driven Subcritical Fissile Solution System

    SciTech Connect

    Klein, Steven Karl; Day, Christy M.; Determan, John C.

    2015-09-14

    LANL has developed a process to generate a progressive family of system models for a fissile solution system. This family includes a dynamic system simulation comprised of coupled nonlinear differential equations describing the time evolution of the system. Neutron kinetics, radiolytic gas generation and transport, and core thermal hydraulics are included in the DSS. Extensions to explicit operation of cooling loops and radiolytic gas handling are embedded in these systems as is a stability model. The DSS may then be converted to an implementation in Visual Studio to provide a design team the ability to rapidly estimate system performance impacts from a variety of design decisions. This provides a method to assist in optimization of the system design. Once design has been generated in some detail the C++ version of the system model may then be implemented in a LabVIEW user interface to evaluate operator controls and instrumentation and operator recognition and response to off-normal events. Taken as a set of system models the DSS, Visual Studio, and LabVIEW progression provides a comprehensive set of design support tools.

  20. Experimental results from the VENUS-F critical reference state for the GUINEVERE accelerator driven system project

    SciTech Connect

    Uyttenhove, W.; Baeten, P.; Kochetkov, A.; Vittiglio, G.; Wagemans, J.; Ban, G.; Lecolley, F.R.; Lecouey, J.L.; Marie, N.; Steckmeyer, J.C.; Billebaud, A.; Chabod, S.; Thyebault, H.E.; Dessagne, P.; Kerveno, M.; Mellier, F.

    2012-12-15

    The GUINEVERE (Generation of Uninterrupted Intense Neutron pulses at the lead Venus Reactor) project was launched in 2006 within the framework of FP6 EUROTRANS in order to validate online reactivity monitoring and subcriticality level determination in accelerator driven systems (ADS). Therefore, the VENUS reactor at SCK.CEN in Mol, Belgium, was modified towards a fast core (VENUS-F) and coupled to the GENEPI-3C accelerator built by CNRS. The accelerator can operate in both continuous and pulsed mode. The VENUS-F core is loaded with enriched Uranium and reflected with solid lead. A well-chosen critical reference state is indispensable for the validation of the online subcriticality monitoring methodology. Moreover, a benchmarking tool is required for nuclear data research and code validation. In this paper, the design and the importance of the critical reference state for the GUINEVERE project are motivated. The results of the first experimental phase on the critical core are presented. The control rods worth is determined by the positive period method and the application of the Modified Source Multiplication (MSM) method allows the determination of the worth of the safety rods. The results are implemented in the VENUS-F core certificate for full exploitation of the critical core. (authors)

  1. Experimental results from the VENUS-F critical reference state for the GUINEVERE accelerator driven system project

    SciTech Connect

    Uyttenhove, W.; Baeten, P.; Ban, G.; Billebaud, A.; Chabod, S.; Dessagne, P.; Kerveno, M.; Kochetkov, A.; Lecolley, F. R.; Lecouey, J. L.; Marie, N.; Mellier, F.; Steckmeyer, J. C.; Thyebault, H. E.; Vittiglio, G.; Wagemans, J.

    2011-07-01

    The GUINEVERE (Generation of Uninterrupted Intense Neutron pulses at the lead Venus Reactor) project was launched in 2006 within the framework of FP6 EUROTRANS in order to validate on-line reactivity monitoring and subcriticality level determination in Accelerator Driven Systems. Therefore the VENUS reactor at SCK.CEN in Mol (Belgium) was modified towards a fast core (VENUS-F) and coupled to the GENEPI-3C accelerator built by CNRS The accelerator can operate in both continuous and pulsed mode. The VENUS-F core is loaded with enriched Uranium and reflected with solid lead. A well-chosen critical reference state is indispensable for the validation of the on-line subcriticality monitoring methodology. Moreover a benchmarking tool is required for nuclear data research and code validation. In this paper the design and the importance of the critical reference state for the GUINEVERE project are motivated. The results of the first experimental phase on the critical core are presented. The control rods worth is determined by the rod drop technique and the application of the Modified Source Multiplication (MSM) method allows the determination of the worth of the safety rods. The results are implemented in the VENUS-F core certificate for full exploitation of the critical core. (authors)

  2. 50 mm Diameter digital DC/pulse neutron generator for subcritical reactor test

    NASA Astrophysics Data System (ADS)

    Li, Gang; Zhang, Zhong-Shuai; Chi, Qian; Liu, Lin-Mao

    2012-11-01

    A 50 mm diameter digital DC/pulse neutron generator was developed with 25 mm ceramic drive-in target neutron tube. It was applied in the subcritical reactor test of China Institute of Atomic Energy (CIAE). The generator can produce neutron in three modes: DC, pulse and multiple pulse. The maximum neutron yield of the generator is 1 × 108 n/s, while the maximum pulse frequency is 10 kHz, and the minimum pulse width is 10 μs. As a remote controlled generator, it is small in volume, easy to be connected and controlled. The tested results indicate that penning ion source has the feature of delay time in glow discharge, and it is easier for glow discharge to happen when switching the DC voltage of penning ion source into pulse. According to these two characteristics, the generator has been modified. This improved generator can be used in many other areas including Prompt Gamma Neutron Activation Analysis (PGNAA), neutron testing and experiment.

  3. Experimental Neutron Source Facility Based on Accelerator Driven System

    NASA Astrophysics Data System (ADS)

    Gohar, Yousry

    2010-06-01

    An experimental neutron source facility has been developed for producing medical isotopes, training young nuclear professionals, providing capability for performing reactor physics, material research, and basic science experiments. It uses a driven subcritical assembly with an electron accelerator. The neutrons driving the subcritical assembly were generated from the electron interactions with a target assembly. Tungsten or uranium target material is used for the neutron production through photonuclear reactions. The neutron source intensity, spectrum, and spatial distribution have been studied to maximize the neutron yield and satisfy different engineering requirements. The subcritical assembly is designed to obtain the highest possible neutron flux intensity with a subcriticality of 0.98. Low enrichment uranium is used for the fuel material because it enhances the neutron source performance. Safety, reliability, and environmental considerations are included in the facility conceptual design. Horizontal neutron channels are incorporated for performing basic research including cold neutron source. This paper describes the conceptual design and summarizes some of the related analyses.

  4. Accelerator Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles

    SciTech Connect

    Brown, Nicholas R.; Heidet, Florent; Haj Tahar, Malek

    2016-01-01

    This article is a review of several accelerator–reactor interface issues and nuclear fuel cycle applications of acceleratordriven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focus on issues of interest, such as the impact of the energy required to run the accelerator and associated systems on the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also review the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity than a critical fast reactor with recycling of uranium and plutonium.

  5. Accelerator Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles

    DOE PAGES

    Brown, Nicholas R.; Heidet, Florent; Haj Tahar, Malek

    2016-01-01

    This article is a review of several accelerator–reactor interface issues and nuclear fuel cycle applications of acceleratordriven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focus on issues of interest, such as the impact of the energy required to run the accelerator and associated systemsmore » on the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also review the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity than a critical fast reactor with recycling of uranium and plutonium.« less

  6. Some basic advantages of accelerator-driven transmutation of minor actinides and iodine-129

    SciTech Connect

    Shmelev, A.N.; Apse, V.A.; Kulikov, G.G.

    1995-10-01

    The blanket of accelerator-driven facility designed for I-129 transmutation doesn`t contain fissile and fertile materials. So the overheating of iodine compounds transmuted is practically excluded. The efficacy of I-129 transmutation is estimated. Curium being accumulated in nuclear reactors can be incinerated in blanket of accelerator-driven facility. The deep depletion of curium diluted with inert material can be achieved.

  7. Simulator for SUPO, a Benchmark Aqueous Homogeneous Reactor (AHR)

    SciTech Connect

    Klein, Steven Karl; Determan, John C.

    2015-10-14

    A simulator has been developed for SUPO (Super Power) an aqueous homogeneous reactor (AHR) that operated at Los Alamos National Laboratory (LANL) from 1951 to 1974. During that period SUPO accumulated approximately 600,000 kWh of operation. It is considered the benchmark for steady-state operation of an AHR. The SUPO simulator was developed using the process that resulted in a simulator for an accelerator-driven subcritical system, which has been previously reported.

  8. Nuclear data needs for accelerator-driven transmutation systems

    SciTech Connect

    Arthur, E.D.; Wilson, W.B.; Young, P.G.

    1994-07-01

    The possibilities of several new technologies based on use of intense, medium-energy proton accelerators are being investigated at Los Alamos National Laboratory. The potential new areas include destruction of long-lived components of nuclear waste, plutonium burning, energy production, and production of tritium. The design, assessment, and safety analysis of potential facilities involves the understanding of complex combinations of nuclear processes, which in turn places new requirements on nuclear data that transcend the traditional needs of the fission and fusion reactor communities. In this paper an assessment of the nuclear data needs for systems currently being considered in the Los Alamos Accelerator-Driven Transmutation Technologies program is given.

  9. Georgia Tech Studies of Sub-Critical Advanced Burner Reactors with a D-T Fusion Tokamak Neutron Source for the Transmutation of Spent Nuclear Fuel

    NASA Astrophysics Data System (ADS)

    Stacey, W. M.

    2009-09-01

    The possibility that a tokamak D-T fusion neutron source, based on ITER physics and technology, could be used to drive sub-critical, fast-spectrum nuclear reactors fueled with the transuranics (TRU) in spent nuclear fuel discharged from conventional nuclear reactors has been investigated at Georgia Tech in a series of studies which are summarized in this paper. It is found that sub-critical operation of such fast transmutation reactors is advantageous in allowing longer fuel residence time, hence greater TRU burnup between fuel reprocessing stages, and in allowing higher TRU loading without compromising safety, relative to what could be achieved in a similar critical transmutation reactor. The required plasma and fusion technology operating parameter range of the fusion neutron source is generally within the anticipated operational range of ITER. The implications of these results for fusion development policy, if they hold up under more extensive and detailed analysis, is that a D-T fusion tokamak neutron source for a sub-critical transmutation reactor, built on the basis of the ITER operating experience, could possibly be a logical next step after ITER on the path to fusion electrical power reactors. At the same time, such an application would allow fusion to contribute to meeting the nation's energy needs at an earlier stage by helping to close the fission reactor nuclear fuel cycle.

  10. About the possibility of use of different types of targets as a neutron source for subcritical nuclear reactor driven by particle beam accelerator

    SciTech Connect

    Avdeev, E.F.; Dorokhovich, S.L.; Chusov, I.A.

    1995-10-01

    The schemes of jet gas and liquid targets as well as the gastargets with a solid phase dispersion are introduced to use to receive the neutrons admitted to a subcritical reactor core. The possible variants of target position in the reactor are considered, target characteristics are calculated. The authors pay a great attention to the estimation of radioactive products yield receiving due to the interaction of the beam with the target.

  11. Neutron cross-sections above 20 MeV for design and modeling of accelerator driven systems

    NASA Astrophysics Data System (ADS)

    Blomgren, J.

    2007-02-01

    One of the outstanding new developments in the field of partitioning and transmutation (P{&}T) concerns accelerator-driven systems (ADS) which consist of a combination of a high-power, high-energy accelerator, a spallation target for neutron production and a sub-critical reactor core. The development of the commercial critical reactors of today motivated a large effort on nuclear data up to about 20 MeV, and presently several million data points can be found in various data libraries. At higher energies, data are scarce or even non-existent. With the development of nuclear techniques based on neutrons at higher energies, nowadays there is a need also for higher-energy nuclear data. To provide alternative to this lack of data, a wide program on neutron-induced data related to ADS for P{&}T is running at the 20-180 MeV neutron beam facility at `The Svedberg Laboratory' (TSL), Uppsala. The programme encompasses studies of elastic scattering, inelastic neutron production, i.e., (n, xn') reactions, light-ion production, fission and production of heavy residues. Recent results are presented and future program of development is outlined.

  12. Conception of electron beam-driven subcritical molten salt ultimate safety reactor

    SciTech Connect

    Abalin, S.S.; Alekseev, P.N.; Ignat`ev, V.V.

    1995-10-01

    This paper is a preliminary sketch of a conception to develop the {open_quotes}ultimate safety reactor{close_quotes} using modern reactor and accelerator technologies. This approach would not require a long-range R&D program. The ultimate safety reactor could produce heat and electric energy, expand the production of fuel, or be used for the transmutation of long-lived wastes. The use of the combined double molten salt reactor system allows adequate neutron multiplication to permit using an electron accelerator for the initial neutron flux. The general parameters of such a system are discussed in this paper.

  13. Method for destroying hazardous organics and other combustible materials in a subcritical/supercritical reactor

    DOEpatents

    Janikowski, Stuart K.

    2000-01-01

    A waste destruction method using a reactor vessel to combust and destroy organic and combustible waste, including the steps of introducing a supply of waste into the reactor vessel, introducing a supply of an oxidant into the reactor vessel to mix with the waste forming a waste and oxidant mixture, introducing a supply of water into the reactor vessel to mix with the waste and oxidant mixture forming a waste, water and oxidant mixture, reciprocatingly compressing the waste, water and oxidant mixture forming a compressed mixture, igniting the compressed mixture forming a exhaust gas, and venting the exhaust gas into the surrounding atmosphere.

  14. Space-time analysis for reactivity determination in source-driven subcritical systems

    NASA Astrophysics Data System (ADS)

    Kulik, Viktoriya V.

    Increasing worldwide interests in accelerator-driven systems is related to their potential role in transmutation of the spent reactor fuel. Margin of safety expressed in terms of reactivity, measuring proximity to criticality, has to be properly addressed for such systems. Monitoring of reactivity enables us to predict performance of a nuclear system and prevent unforeseen accidents. However, due to the presence of a localized spallation source in an accelerator-driven subcritical system leads to a significantly different neutron flux shape than a source-free fundamental mode in critical systems. As a result, the simple point kinetics approach commonly used for determination of reactivity in critical systems does not account properly for space-time effects in accelerator-driven subcritical systems, yielding inaccurate estimates in reactivity. To overcome this problem and account properly for spatial and spectral effects in reactivity determination, a method directly combining measurements with numerical simulations of the experimental data is developed within a quasi-static formulation. This method provides space-time corrections to a variety of traditional point kinetics techniques and determines the reactivity essentially independent of the detector position, as long as sufficiently accurate information on the reactor configuration is provided. In the dissertation, the space-time corrections are derived for two well-known point kinetics methods: the area-ratio technique and the alpha-method. Numerical simulations performed with the FX2-TH diffusion theory code along with a space-time analysis of MUSE-4 pulsed source experimental data illustrate the applicability of the proposed methods for the determination of significant subcriticality levels in fast and thermal reactor systems. To perform space-time reactivity corrections at reduced computational cost, a modal-local method is developed for source-driven systems and tested with the ERANOS code. This dissertation

  15. Comparison of Reactivity Control Systems for the Submersion Subcritical Safe Space (S and 4) Reactor

    SciTech Connect

    Schriener, Timothy M.; El-Genk, Mohamed S.

    2008-01-21

    This paper compares the effectiveness of two control mechanisms for the S and 4 reactor, namely: (a) rotating BeO drums with 120 deg. thin segments of enriched B{sub 4}C in the radial reflector; and (b) sliding windows in the radial reflector. Investigated are the effects of using these control mechanisms on the differential reactor control worth, power generation profiles, and spatial neutrons flux distributions is the S and 4 reactor. For both control mechanism, the radial reflector has the same dimensions and volume. Results show that the difference in reactor performance with the two control mechanisms is small. The sliding reflector configuration features slightly lower mass and power peaking, and relatively more even fission power profiles in the core. The differential control worth for the sliding reflector segments is almost constant compared to that using rotating control drums, potentially simplifying the reactor control operation. The presence of a strong neutron absorber in the rotating drums slightly decreases the amount of excess reactivity at BOL compared with the sliding reflector configuration. However, the higher rate of reactivity depletion in the S and 4 reactor with the latter may negate this advantage.

  16. Comparison of Reactivity Control Systems for the Submersion Subcritical Safe Space (S∧4) Reactor

    NASA Astrophysics Data System (ADS)

    Schriener, Timothy M.; El-Genk, Mohamed S.

    2008-01-01

    This paper compares the effectiveness of two control mechanisms for the S∧4 reactor, namely: (a) rotating BeO drums with 120° thin segments of enriched B4C in the radial reflector; and (b) sliding windows in the radial reflector. Investigated are the effects of using these control mechanisms on the differential reactor control worth, power generation profiles, and spatial neutrons flux distributions is the S∧4 reactor. For both control mechanism, the radial reflector has the same dimensions and volume. Results show that the difference in reactor performance with the two control mechanisms is small. The sliding reflector configuration features slightly lower mass and power peaking, and relatively more even fission power profiles in the core. The differential control worth for the sliding reflector segments is almost constant compared to that using rotating control drums, potentially simplifying the reactor control operation. The presence of a strong neutron absorber in the rotating drums slightly decreases the amount of excess reactivity at BOL compared with the sliding reflector configuration. However, the higher rate of reactivity depletion in the S∧4 reactor with the latter may negate this advantage.

  17. Research opportunities with compact accelerator-driven neutron sources

    NASA Astrophysics Data System (ADS)

    Anderson, I. S.; Andreani, C.; Carpenter, J. M.; Festa, G.; Gorini, G.; Loong, C.-K.; Senesi, R.

    2016-10-01

    Since the discovery of the neutron in 1932 neutron beams have been used in a very broad range of applications, As an aging fleet of nuclear reactor sources is retired the use of compact accelerator-driven neutron sources (CANS) is becoming more prevalent. CANS are playing a significant and expanding role in research and development in science and engineering, as well as in education and training. In the realm of multidisciplinary applications, CANS offer opportunities over a wide range of technical utilization, from interrogation of civil structures to medical therapy to cultural heritage study. This paper aims to provide the first comprehensive overview of the history, current status of operation, and ongoing development of CANS worldwide. The basic physics and engineering regarding neutron production by accelerators, target-moderator systems, and beam line instrumentation are introduced, followed by an extensive discussion of various evolving applications currently exploited at CANS.

  18. Separations technology development to support accelerator-driven transmutation concepts

    SciTech Connect

    Venneri, F.; Arthur, E.; Bowman, C.

    1996-10-01

    This is the final report of a one-year Laboratory-Directed Research and Development (LDRD) Project at the Los Alamos National Laboratory (LANL). This project investigated separations technology development needed for accelerator-driven transmutation technology (ADTT) concepts, particularly those associated with plutonium disposition (accelerator-based conversion, ABC) and high-level radioactive waste transmutation (accelerator transmutation of waste, ATW). Specific focus areas included separations needed for preparation of feeds to ABC and ATW systems, for example from spent reactor fuel sources, those required within an ABC/ATW system for material recycle and recovery of key long-lived radionuclides for further transmutation, and those required for reuse and cleanup of molten fluoride salts. The project also featured beginning experimental development in areas associated with a small molten-salt test loop and exploratory centrifugal separations systems.

  19. Estimation of the sub-criticality of the sodium-cooled fast reactor Monju using the modified neutron source multiplication method

    SciTech Connect

    Truchet, G.; Van Rooijen, W. F. G.; Shimazu, Y.; Yamaguchi, K.

    2012-07-01

    The Modified Neutron Source Method (MNSM) is applied to the Monju reactor. This static method to estimate sub-criticality has already given good results on commercial Pressurized Water Reactors. The MNSM consists both in the extraction of the fundamental mode seen by a detector to avoid the effect of higher modes near sources, and the correction of flux distortion effects due to control rod movement. Among Monju's particularities that have a big influence on MNSM factors are: the presence of two californium sources and the position of the detector which is located far from the core outside of the reactor vessel. The importance of spontaneous fission and ({alpha}, n) reactions which have increased during the shutdown period of 15 years will also be discussed. The relative position of detectors and sources deeply affect the correction factors in some regions. In order to evaluate the detector count rate, an analytical propagation has been conducted from the reactor vessel. For two subcritical states, an estimation of the reactivity has been made and compared to experimental data obtained in the restart experiments at Monju (2010). (authors)

  20. Accelerator-driven X-ray Sources

    SciTech Connect

    Nguyen, Dinh Cong

    2015-11-09

    After an introduction which mentions x-ray tubes and storage rings and gives a brief review of special relativity, the subject is treated under the following topics and subtopics: synchrotron radiation (bending magnet radiation, wiggler radiation, undulator radiation, brightness and brilliance definition, synchrotron radiation facilities), x-ray free-electron lasers (linac-driven X-ray FEL, FEL interactions, self-amplified spontaneous emission (SASE), SASE self-seeding, fourth-generation light source facilities), and other X-ray sources (energy recovery linacs, Inverse Compton scattering, laser wakefield accelerator driven X-ray sources. In summary, accelerator-based light sources cover the entire electromagnetic spectrum. Synchrotron radiation (bending magnet, wiggler and undulator radiation) has unique properties that can be tailored to the users’ needs: bending magnet and wiggler radiation is broadband, undulator radiation has narrow spectral lines. X-ray FELs are the brightest coherent X-ray sources with high photon flux, femtosecond pulses, full transverse coherence, partial temporal coherence (SASE), and narrow spectral lines with seeding techniques. New developments in electron accelerators and radiation production can potentially lead to more compact sources of coherent X-rays.

  1. Accelerator-driven transmutation of spent fuel elements

    DOEpatents

    Venneri, Francesco; Williamson, Mark A.; Li, Ning

    2002-01-01

    An apparatus and method is described for transmuting higher actinides, plutonium and selected fission products in a liquid-fuel subcritical assembly. Uranium may also be enriched, thereby providing new fuel for use in conventional nuclear power plants. An accelerator provides the additional neutrons required to perform the processes. The size of the accelerator needed to complete fuel cycle closure depends on the neutron efficiency of the supported reactors and on the neutron spectrum of the actinide transmutation apparatus. Treatment of spent fuel from light water reactors (LWRs) using uranium-based fuel will require the largest accelerator power, whereas neutron-efficient high temperature gas reactors (HTGRs) or CANDU reactors will require the smallest accelerator power, especially if thorium is introduced into the newly generated fuel according to the teachings of the present invention. Fast spectrum actinide transmutation apparatus (based on liquid-metal fuel) will take full advantage of the accelerator-produced source neutrons and provide maximum utilization of the actinide-generated fission neutrons. However, near-thermal transmutation apparatus will require lower standing

  2. Th and U fuel photofission study by NTD for AD-MSR subcritical assembly

    NASA Astrophysics Data System (ADS)

    Sajo-Bohus, Laszlo; Greaves, Eduardo D.; Davila, Jesus; Barros, Haydn; Pino, Felix; Barrera, Maria T.; Farina, Fulvio

    2015-07-01

    During the last decade a considerable effort has been devoted for developing energy generating systems based on advanced nuclear technology within the design concepts of GEN-IV. Thorium base fuel systems such as accelerator driven nuclear reactors are one of the often mentioned attractive and affordable options. Several radiotherapy linear accelerators are on the market and due to their reliability, they could be employed as drivers for subcritical liquid fuel assemblies. Bremsstrahlung photons with energies above 5.5MeV, induce (γ,n) and (e,e'n) reactions in the W-target. Resulting gamma radiation and photo or fission neutrons may be absorbed in target materials such as thorium and uranium isotopes to induce sustained fission or nuclear transmutation in waste radioactive materials. Relevant photo driven and photo-fission reaction cross sections are important for actinides 232Th, 238U and 237Np in the radiotherapy machines energy range of 10-20 MV. In this study we employ passive nuclear track detectors (NTD) to determine fission rates and neutron production rates with the aim to establish the feasibility for gamma and photo-neutron driven subcritical assemblies. To cope with these objectives a 20 MV radiotherapy machine has been employed with a mixed fuel target. Results will support further development for a subcritical assembly employing a thorium containing liquid fuel. It is expected that acquired technological knowledge will contribute to the Venezuelan nuclear energy program.

  3. MCNPX, MONK, and ERANOS analyses of the YALINA booster subcritical assembly.

    SciTech Connect

    Talamo, A.; Gohar, Y.; Aliberti, G.; Cao, Y.; Smith, D.; Zhong, Z.; Kiyavitskaya, H.; Bournos, V.; Fokov, Y.; Routkovskaya, C.; Serafimovich, I.

    2011-05-01

    This paper compares the numerical results obtained from various nuclear codes and nuclear data libraries with the YALINA Booster subcritical assembly (Minsk, Belarus) experimental results. This subcritical assembly was constructed to study the physics and the operation of accelerator-driven subcritical systems (ADS) for transmuting the light water reactors (LWR) spent nuclear fuel. The YALINA Booster facility has been accurately modeled, with no material homogenization, by the Monte Carlo codes MCNPX (MCNP/MCB) and MONK. The MONK geometrical model matches that of MCNPX. The assembly has also been analyzed by the deterministic code ERANOS. In addition, the differences between the effective neutron multiplication factor and the source multiplication factors have been examined by alternative calculational methodologies. The analyses include the delayed neutron fraction, prompt neutron lifetime, generation time, neutron flux profiles, and spectra in various experimental channels. The accuracy of the numerical models has been enhanced by accounting for all material impurities and the actual density of the polyethylene material used in the assembly (the latter value was obtained by dividing the total weight of the polyethylene by its volume in the numerical model). There is good agreement between the results from MONK, MCNPX, and ERANOS. The ERANOS results show small differences relative to the other results because of material homogenization and the energy and angle discretizations.The MCNPX results match the experimental measurements of the {sup 3}He(n,p) reaction rates obtained with the californium neutron source.

  4. Th and U fuel photofission study by NTD for AD-MSR subcritical assembly

    SciTech Connect

    Sajo-Bohus, Laszlo; Greaves, Eduardo D.; Barros, Haydn; Pino, Felix; Barrera, Maria T.; Farina, Fulvio; Davila, Jesus

    2015-07-23

    During the last decade a considerable effort has been devoted for developing energy generating systems based on advanced nuclear technology within the design concepts of GEN-IV. Thorium base fuel systems such as accelerator driven nuclear reactors are one of the often mentioned attractive and affordable options. Several radiotherapy linear accelerators are on the market and due to their reliability, they could be employed as drivers for subcritical liquid fuel assemblies. Bremsstrahlung photons with energies above 5.5MeV, induce (γ,n) and (e,e’n) reactions in the W-target. Resulting gamma radiation and photo or fission neutrons may be absorbed in target materials such as thorium and uranium isotopes to induce sustained fission or nuclear transmutation in waste radioactive materials. Relevant photo driven and photo-fission reaction cross sections are important for actinides {sup 232}Th, {sup 238}U and {sup 237}Np in the radiotherapy machines energy range of 10-20 MV. In this study we employ passive nuclear track detectors (NTD) to determine fission rates and neutron production rates with the aim to establish the feasibility for gamma and photo-neutron driven subcritical assemblies. To cope with these objectives a 20 MV radiotherapy machine has been employed with a mixed fuel target. Results will support further development for a subcritical assembly employing a thorium containing liquid fuel. It is expected that acquired technological knowledge will contribute to the Venezuelan nuclear energy program.

  5. Absolute reactivity calibration of accelerator-driven systems after RACE-T experiments

    SciTech Connect

    Jammes, C. C.; Geslot, B.

    2006-07-01

    The RACE-T experiments that were held in november 2005 in the ENEA-Casaccia research center near Rome allowed us to improve our knowledge of the experimental techniques for absolute reactivity calibration at either startup or shutdown phases of accelerator-driven systems. Various experimental techniques for assessing a subcritical level were inter-compared through three different subcritical configurations SC0, SC2 and SC3, about -0.5, -3 and -6 dollars, respectively. The area-ratio method based of the use of a pulsed neutron source appears as the most performing. When the reactivity estimate is expressed in dollar unit, the uncertainties obtained with the area-ratio method were less than 1% for any subcritical configuration. The sensitivity to measurement location was about slightly more than 1% and always less than 4%. Finally, it is noteworthy that the source jerk technique using a transient caused by the pulsed neutron source shutdown provides results in good agreement with those obtained from the area-ratio technique. (authors)

  6. Dynamic response of an accelerator driven system to accelerator beam interruptions for criticality

    NASA Astrophysics Data System (ADS)

    Lafuente, A.; Abanades, A.; Leon, P. T.; Sordo, F.; Martinez-Val, J. M.

    2008-06-01

    Subcritical nuclear reactors driven by intense neutron sources can be very suitable tools for nuclear waste transmutation, particularly in the case of minor actinides with very low fractions of delayed neutrons. A proper control of these systems needs to know at every time the absolute value of the reactor subcriticality (negative reactivity), which must be measured by fully reliable methods, usually conveying a short interruption of the accelerator beam in order to assess the neutron flux reduction. Those interruptions should be very short in time, for not disturbing too much the thermal magnitudes of the reactor. Otherwise, the cladding and the fuel would suffer from thermal fatigue produced by those perturbations, and the mechanical integrity of the reactor would be jeopardized. It is shown in this paper that beam interruptions of the order of 400 μs repeated every second would not disturb significantly the reactor thermal features, while enabling for an adequate measurement of the negative reactivity.

  7. Shielding analysis at the upper section of the accelerator-driven system.

    PubMed

    Sasa, Toshinobu; Yang, Jin An; Oigawa, Hiroyuki

    2005-01-01

    The proton beam duct of the accelerator-driven system (ADS) acts as a streaming path for spallation neutrons and photons and causes the activation of the magnets and other devices above the subcritical core. We have performed a streaming analysis at the upper section of the lead-bismuth target/cooled ADS (800 MWth). MCNPX was used to calculate the radiation dose from streamed neutrons and photons through the beam duct. For the secondary photon production calculation, cross sections for several actinides were substituted with plutonium because of the lack of gamma production cross section. From the results of this analysis, the neutron dose from the beam duct is seen to be about 20 orders higher than that of the bulk shield. The magnets and shield plug are heavily irradiated by streaming neutrons according to the DCHAIN-SP analysis.

  8. A method and apparatus for destroying hazardous organics and other combustible materials in a subcritical/supercritical reactor

    SciTech Connect

    Janikowski, Stuart K.

    1997-12-01

    A waste destruction method is described using a reactor vessel to combust and destroy organic and combustible waste, including the steps of introducing a supply of waste into the reactor vessel, introducing a supply of an oxidant into the reactor vessel to mix with the waste forming a waste and oxidant mixture, introducing a supply of water into the reactor vessel to mix with the waste and oxidant mixture forming a waste, water and oxidant mixture, reciprocatingly compressing the waste, water and oxidant mixture forming a compressed mixture, igniting the compressed mixture forming a exhaust gas, and venting the exhaust gas into the surrounding atmosphere.

  9. Properties of the Feynman-alpha method applied to accelerator-driven subcritical systems.

    PubMed

    Taczanowski, S; Domanska, G; Kopec, M; Janczyszyn, J

    2005-01-01

    A Monte Carlo study of the Feynman-method with a simple code simulating the multiplication chain, confined to pertinent time-dependent phenomena has been done. The significance of its key parameters (detector efficiency and dead time, k-source and spallation neutrons multiplicities, required number of fissions etc.) has been discussed. It has been demonstrated that this method can be insensitive to properties of the zones surrounding the core, whereas is strongly affected by the detector dead time. In turn, the influence of harmonics in the neutron field and of the dispersion of spallation neutrons has proven much less pronounced.

  10. The neutronics of an Accelerator-Driven Energy Amplifier

    SciTech Connect

    Moeller, E.; Gudowski, W.

    1995-10-01

    This study has been focused on an Accelerator-Driven Energy Amplifier, based on the concept proposed by the CERN-group. To analyze the performance of this system the extensive optimization of the core lattice was done, the temperature coefficients of reactivity were investigated, reactivity budget and power distribution were estimated.

  11. Operational Characteristics of an Accelerator Driven Fissile Solution System

    SciTech Connect

    Kimpland, Robert Herbert

    2016-11-28

    Operational characteristics represent the set of responses that a nuclear system exhibits during normal operation. Operators rely on this behavior to assess the status of the system and to predict the consequences of off-normal events. These characteristics largely refer to the relationship between power and system operating conditions. The static and dynamic behavior of a chain-reacting system, operating at sufficient power, is primarily governed by reactivity effects. The science of reactor physics has identified and evaluated a number of such effects, including Doppler broadening and shifts in the thermal neutron spectrum. Often these reactivity effects are quantified in the form of feedback coefficients that serve as coupling coefficients relating the neutron population and the physical mechanisms that drive reactivity effects, such as fissile material temperature and density changes. The operational characteristics of such nuclear systems usually manifest themselves when perturbations between system power (neutron population) and system operating conditions arise. Successful operation of such systems requires the establishment of steady equilibrium conditions. However, prior to obtaining the desired equilibrium (steady-state) conditions, an approach from zero-power (startup) must occur. This operational regime may possess certain limiting system conditions that must be maintained to achieve effective startup. Once steady-state is achieved, a key characteristic of this operational regime is the level of stability that the system possesses. Finally, a third operational regime, shutdown, may also possess limiting conditions of operation that must be maintained. This report documents the operational characteristics of a “generic” Accelerator Driven Fissile Solution (ADFS) system during the various operational regimes of startup, steady-state operation, and shutdown. Typical time-dependent behavior for each operational regime will be illustrated, and key system

  12. Experimental study on the thorium-loaded accelerator-driven system at the Kyoto Univ. critical assembly

    SciTech Connect

    Pyeon, C. H.; Yagi, T.; Lim, J. Y.; Misawa, T.

    2012-07-01

    The experimental study on the thorium-loaded accelerator-driven system (ADS) is conducted in the Kyoto Univ. Critical Assembly (KUCA). The experiments are carried out in both the critical and subcritical states for attaining the reaction rates of the thorium capture and fission reactions. In the critical system, the thorium plate irradiation experiment is carried out for the thorium capture and fission reactions. From the results of the measurements, the thorium fission reactions are obtained apparently in the critical system, and the C/E values of reaction rates show the accuracy of relative difference of about 30%. In the ADS experiments with 14 MeV neutrons and 100 MeV protons, the subcritical experiments are carried out in the thorium-loaded cores to obtain the capture reaction rates through the measurements of {sup 115}In(n, {gamma}){sup 116m}In reactions. The results of the experiments reveal the difference between the reaction rate distributions for the change in not only the neutron spectrum but also the external neutron source. The comparison between the measured and calculated reaction rate distributions demonstrates a discrepancy of the accuracy of reaction rate analyses of thorium capture reactions through the thorium-loaded ADS experiments with 14 MeV neutrons. Hereafter, kinetic experiments are planned to be carried out to deduce the delayed neutron decay constants and subcriticality using the pulsed neutron method. (authors)

  13. Accelerator-Driven Thorium-Cycle Fission:. Green Nuclear Power for the New Millennium

    NASA Astrophysics Data System (ADS)

    McIntyre, Peter; Sattarov, Akhdiyor

    2011-03-01

    In thorium-cycle fission, fast neutrons are used to transmute thorium to fissionable 233U and then stimulate fission. In accelerator-driven thorium-cycle fission (ADTC) the fast neutrons are produced by injecting a symmetric pattern of 7 energetic proton beams into a Pb spallation zone in the core. The fast neutrons are adiabatically moderated by the Pb so that they capture efficiently on 232Th, and fission heat is transferred via a convective Pb column above the core. The 7 proton beams are generated by a flux-coupled stack of isochronous cyclotrons. ADTC offers a green solution to the Earth's energy needs: the core operates as a sub-critical pile and cannot melt down; it eats its own long-lived fission products; a GW ADTC core can operate with uniform power density for a 7-year fuel cycle without shuffling fuel pins, and there are sufficient thorium reserves to run man's energy needs for the next 2000 years.

  14. Fission-Produced (99)Mo Without a Nuclear Reactor.

    PubMed

    Youker, Amanda J; Chemerisov, Sergey D; Tkac, Peter; Kalensky, Michael; Heltemes, Thad A; Rotsch, David A; Vandegrift, George F; Krebs, John F; Makarashvili, Vakho; Stepinski, Dominique C

    2017-03-01

    (99)Mo, the parent of the widely used medical isotope (99m)Tc, is currently produced by irradiation of enriched uranium in nuclear reactors. The supply of this isotope is encumbered by the aging of these reactors and concerns about international transportation and nuclear proliferation. Methods: We report results for the production of (99)Mo from the accelerator-driven subcritical fission of an aqueous solution containing low enriched uranium. The predominately fast neutrons generated by impinging high-energy electrons onto a tantalum convertor are moderated to thermal energies to increase fission processes. The separation, recovery, and purification of (99)Mo were demonstrated using a recycled uranyl sulfate solution. Conclusion: The (99)Mo yield and purity were found to be unaffected by reuse of the previously irradiated and processed uranyl sulfate solution. Results from a 51.8-GBq (99)Mo production run are presented. © 2017 by the Society of Nuclear Medicine and Molecular Imaging.

  15. Accelerator-Driven Systems Neutronic Analyses at ENEA and Politecnico di Torino

    SciTech Connect

    Carta, M.; Burn, K.W.; D'Angelo, A.; Peluso, V.; Ravetto, P.

    1999-11-14

    A growing interest in accelerator-driven systems (ADSs) has led to the establishment in Italy of a basic research and development program aimed at the study of the physics and technological development needed to design an ADS for nuclear waste transmutation. In the framework of this program, ENEA and Politecnico di Torino are carrying out some neutronic analyses focused on an ADS prototype of small size, named EAP80 [{approx}80 MW(thermal)], fueled with a standard fast reactor fuel (Superphenix 1 type), and cooled by Pb/Bi. The EAP80 prototype was conceived with close reference to Rubbia et al.'s energy amplifier proposal. Current neutronic activities cover the development of computational tools and static and kinetics analyses. This paper summarizes some preliminary results and specifications.

  16. The GUINEVERE experiment: First PNS measurements in a lead moderated sub-critical fast core

    SciTech Connect

    Thyebault, H. E.; Billebaud, A.; Chabod, S.; Lecolley, F. R.; Lecouey, J. L.; Lehaut, G.; Marie, N.; Ban, G.

    2012-07-01

    The GUINEVERE (Generation of Uninterrupted Intense Neutrons at the lead Venus Reactor) experimental program is dedicated to the study of Accelerator Driven System reactivity monitoring. It was partly carried out within the EUROTRANS integrated project (EURATOM FP6). GUINEVERE consists in coupling the fast core of the VENUS-F reactor (SCK-CEN, Mol (Belgium)), composed of enriched uranium and solid lead, with a T(d,n) neutron source provided by the GENEPI-3C deuteron accelerator. This neutron source can be operated in several modes: pulsed mode, continuous mode and also continuous mode with short beam interruptions (the so called 'beam trips'). In the past, the key questions of the reactivity control and monitoring in a subcritical system were studied in the MUSE experiments (1998-2004). These experiments highlighted the difficulty to determine precisely the reactivity with a single technique. This led to investigate a new strategy which is based on the combination of the relative reactivity monitoring via the core power to beam current relationship with absolute reactivity cross-checks during programmed beam interruptions. Consequently, to determine the reactivity, several dynamical techniques of reactivity determination have to be compared. In addition, their accuracy for absolute reactivity determination must be evaluated using a reference reactivity determination technique (from a critical state: rod drop and MSM measurements). The first sub-critical configuration which was studied was around k{sub eff} = 0.96 (SCI). Pulsed Neutron Source experiments (PNS) were carried out. The neutron population decrease was measured using fission chambers in different locations inside the core and the reflector. Neutron population time decrease was analyzed using fitting techniques and the Area Method Results obtained for the SCI reactivity will be shown, discussed and compared to the reference value given by the MSM method. (authors)

  17. MYRRHA a multi-purpose hybrid research reactor for high-tech applications

    SciTech Connect

    Abderrahim, H. A.; Baeten, P.

    2012-07-01

    MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) is the flexible experimental accelerator driven system (ADS) in development at SCK-CEN. MYRRHA is able to work both in subcritical (ADS) as in critical mode. In this way, MYRRHA will allow fuel developments for innovative reactor systems, material developments for generation IV (GEN IV) systems, material developments for fusion reactors, radioisotope production and industrial applications, such as Si-doping. MYRRHA will also demonstrate the ADS full concept by coupling the three components (accelerator, spallation target and subcritical reactor) at reasonable power level to allow operation feedback, scalable to an industrial demonstrator and allow the study of efficient transmutation of high-level nuclear waste. MYRRHA is based on the heavy liquid metal technology and so it will contribute to the development of lead fast reactor (LFR) technology and in critical mode, MYRRHA will play the role of European technology pilot plant in the roadmap for LFR. In this paper the historical evolution of MYRRHA and the rationale behind the design choices is presented and the latest configuration of the reactor core and primary system is described. (authors)

  18. Review of Subcritical Source-Driven Noise Analysis Measurements

    SciTech Connect

    Valentine, T.E.

    1999-11-01

    Subcritical source-driven noise measurements are simultaneous Rossia and randomly pulsed neutron measurements that provide measured quantities that can be related to the subcritical neutron multiplication factor. In fact, subcritical source-driven noise measurements should be performed in lieu of Rossia measurements because of the additional information that is obtained from noise measurements such as the spectral ratio and the coherence functions. The basic understanding of source-driven noise analysis measurements can be developed from a point reactor kinetics model to demonstrate how the measured quantities relate to the subcritical neutron multiplication factor.

  19. Accelerator driven sytems from the radiological safety point of view

    NASA Astrophysics Data System (ADS)

    Sarkar, P. K.; Nandy, Maitreyee

    2007-02-01

    In the proposed accelerator driven systems (ADS) the possible use of several milliamperes of protons of about 1 GeV incident on high mass targets like the molten lead--bismuth eutectic is anticipated to pose radiological problems that have so far not been encountered by the radiation protection community. Spallation reaction products like high energy gammas, neutrons, muons, pions and several radiotoxic nuclides including Po-210 complicate the situation. In the present paper, we discuss radiation safety measures like bulk shielding, containment of radiation leakage through ducts and penetration and induced activity in the structure to protect radiation workers as well as estimation of sky-shine, soil and ground water activation, release of toxic gases to the environment to protect public as per the stipulations of the regulatory authorities. We recommend the application of the probabilistic safety analysis technique by assessing the probability and criticality of different hazard-initiating events using HAZOP and FMECA.

  20. Radiological Hazard of Spallation Products in Accelerator-Driven System

    SciTech Connect

    Saito, M.; Stankovskii, A.; Artisyuk, V.; Korovin, Yu.; Shmelev, A.; Titarenko, Yu.

    2002-09-15

    The central issue underlying this paper is related to elucidating the hazard of radioactive spallation products that might be an important factor affecting the design option of accelerator-driven systems (ADSs). Hazard analysis based on the concept of Annual Limit on Intake identifies alpha-emitting isotopes of rare earths (REs) (dysprosium, gadolinium, and samarium) as the dominant contributors to the overall toxicity of traditional (W, Pb, Pb-Bi) targets. The matter is addressed from several points of view: code validation to simulate their yields, choice of material for the neutron producing targets, and challenging the beam type. The paper quantitatively determines the domain in which the toxicity of REs exceeds that of polonium activation products broadly discussed now in connection with advertising lead-bismuth technology for the needs of ADSs.

  1. A Proposal for a Subcritical Reactivity Meter based on Gandini and Salvatores' point kinetics equations for Multiplying Subcritical Systems

    SciTech Connect

    Pinto, Leticia N.; Dos Santos, Adimir

    2015-07-01

    Multiplying Subcritical Systems were for a long time poorly studied and its theoretical description remains with plenty open questions. Great interest on such systems arose partly due to the improvement of hybrid concepts, such as the Accelerator-Driven Systems (ADS). Along with the need for new technologies to be developed, further study and understanding of subcritical systems are essential also in more practical situations, such as in the case of a PWR criticalization in their physical startup tests. Point kinetics equations are fundamental to continuously monitor the reactivity behavior to a possible variation of external sources intensity. In this case, quickly and accurately predicting power transients and reactivity becomes crucial. It is known that conventional Reactivity Meters cannot operate in subcritical levels nor describe the dynamics of multiplying systems in these conditions, by the very structure of the classical kinetic equations. Several theoretical models have been proposed to characterize the kinetics of such systems with special regard to the reactivity, as the one developed by Gandini and Salvatores among others. This work presents a discussion about the derivation of point kinetics equations for subcritical systems and the importance of considering the external source. From the point of view of the Gandini and Salvatores' point kinetics model and based on the experimental results provided by Lee and dos Santos, it was possible to develop an innovative approach. This article proposes an algorithm that describes the subcritical reactivity with external source, contributing to the advancement of studies in the field. (authors)

  2. Accelerator-driven transmutation technologies for resolution of long-term nuclear waste concerns

    SciTech Connect

    Bowman, C.D.

    1996-10-01

    The paper provides a rationale for resolution of the long-term waste disposition issue based on complete destruction of fissile material and all higher actinides. It begins with a brief history of geologic storage leading to the present impasse in the US. The proliferation aspects of commercial plutonium are presented in a new light as a further driver for complete destruction. The special problems in Russia and the US of the disposition of the highly enriched spent naval reactor fuel and spent research reactor fuel are also presented. The scale of the system required for complete destruction is also examined and it is shown that a practical system for complete destruction of commercial and defense fissile material must be widely dispersed rather than concentrated at a single site. Central tenants of the US National Academy of Sciences recommendations on waste disposition are examined critically and several technologies considered for waste destruction are described briefly and compared Recommendations for waste disposition based on Accelerator-Driven Transmutation Technology suitable for both the US and Russia are presented.

  3. A New Type of Plasma Wakefield Accelerator Driven By Magnetowaves

    SciTech Connect

    Chen, Pisin; Chang, Feng-Yin; Lin, Guey-Lin; Noble, Robert J.; Sydora, Richard; /Alberta U.

    2011-09-12

    We present a new concept for a plasma wakefield accelerator driven by magnetowaves (MPWA). This concept was originally proposed as a viable mechanism for the 'cosmic accelerator' that would accelerate cosmic particles to ultra-high energies in the astrophysical setting. Unlike the more familiar plasma wakefield accelerator (PWFA) and the laser wakefield accelerator (LWFA) where the drivers, the charged-particle beam and the laser, are independently existing entities, MPWA invokes the high-frequency and high-speed whistler mode as the driver, which is a medium wave that cannot exist outside of the plasma. Aside from the difference in drivers, the underlying mechanism that excites the plasma wakefield via the ponderomotive potential is common. Our computer simulations show that under appropriate conditions, the plasma wakefield maintains very high coherence and can sustain high-gradient acceleration over many plasma wavelengths. We suggest that in addition to its celestial application, the MPWA concept can also be of terrestrial utility. A proof-of-principle experiment on MPWA would benefit both terrestrial and celestial accelerator concepts.

  4. INSTRUMENTS AND METHODS OF INVESTIGATION: An accelerator-driven system for the destruction of nuclear waste

    NASA Astrophysics Data System (ADS)

    Revol, Jean-Pierre

    2003-07-01

    Progress in particle accelerator technology makes it possible to use a proton accelerator to produce energy and to destroy nuclear waste efficiently. The energy amplifier (EA) proposed by Carlo Rubbia and his group is a subcritical fast neutron system driven by a proton accelerator. It is particularly attractive for destroying, through fission, transuranic elements produced by presently operating nuclear reactors. The EA could also efficiently and at minimal cost transform long-lived fission fragments using the concept of adiabatic resonance crossing (ARC), recently tested at CERN with the TARC experiment. The ARC concept can be extended to several other domains of application (production of radioactive isotopes for medicine and industry, neutron research applications, etc.).

  5. Radioactive isotope production for medical applications using Kharkov electron driven subcritical assembly facility.

    SciTech Connect

    Talamo, A.; Gohar, Y.; Nuclear Engineering Division

    2007-05-15

    Kharkov Institute of Physics and Technology (KIPT) of Ukraine has a plan to construct an accelerator driven subcritical assembly. The main functions of the subcritical assembly are the medical isotope production, neutron thereby, and the support of the Ukraine nuclear industry. Reactor physics experiments and material research will be carried out using the capabilities of this facility. The United States of America and Ukraine have started collaboration activity for developing a conceptual design for this facility with low enrichment uranium (LEU) fuel. Different conceptual designs are being developed based on the facility mission and the engineering requirements including nuclear physics, neutronics, heat transfer, thermal hydraulics, structure, and material issues. Different fuel designs with LEU and reflector materials are considered in the design process. Safety, reliability, and environmental considerations are included in the facility conceptual design. The facility is configured to accommodate future design improvements and upgrades. This report is a part of the Argonne National Laboratory Activity within this collaboration for developing and characterizing the subcritical assembly conceptual design. In this study, the medical isotope production function of the Kharkov facility is defined. First, a review was carried out to identify the medical isotopes and its medical use. Then a preliminary assessment was performed without including the self-shielding effect of the irradiated samples. Finally, more detailed investigation was carried out including the self-shielding effect, which defined the sample size and irradiation location for producing each medical isotope. In the first part, the reaction rates were calculated as the multiplication of the cross section with the unperturbed neutron flux of the facility. Over fifty isotopes were considered and all transmutation channels are used including (n,{gamma}), (n,2n), (n,p), and ({gamma},n). In the second part

  6. Impact of intermediate and high energy nuclear data on the neutronic safety parameters of MYRRHA accelerator driven system

    NASA Astrophysics Data System (ADS)

    Stankovskiy, Alexey; Çelik, Yurdunaz; Eynde, Gert Van den

    2017-09-01

    Perturbation of external neutron source can cause significant local power changes transformed into undesired safety-related events in an accelerator driven system. Therefore for the accurate design of MYRRHA sub-critical core it is important to evaluate the uncertainty of power responses caused by the uncertainties in nuclear reaction models describing the particle transport from primary proton energy down to the evaluated nuclear data table range. The calculations with a set of models resulted in quite low uncertainty on the local power caused by significant perturbation of primary neutron yield from proton interactions with lead and bismuth isotopes. The considered accidental event of prescribed proton beam shape loss causes drastic increase in local power but does not practically change the total core thermal power making this effect difficult to detect. In the same time the results demonstrate a correlation between perturbed local power responses in normal operation and misaligned beam conditions indicating that generation of covariance data for proton and neutron induced neutron multiplicities for lead and bismuth isotopes is needed to obtain reliable uncertainties for local power responses.

  7. Review of Subcritical Source-Driven Noise Analysis Measurements

    SciTech Connect

    Valentine, T.E.

    1999-11-24

    Subcritical source-driven noise measurements are simultaneous Rossi-{alpha} and randomly pulsed neutron measurements that provide measured quantities that can be related to the subcritical neutron multiplication factor. In fact, subcritical source-driven noise measurements should be performed in lieu of Rossi-{alpha} measurements because of the additional information that is obtained from noise measurements such as the spectral ratio and the coherence functions. The basic understanding of source-driven noise analysis measurements can be developed from a point reactor kinetics model to demonstrate how the measured quantities relate to the subcritical neutron multiplication factor. More elaborate models can also be developed using a generalized stochastic model. These measurements can be simulated using Monte Carlo codes to determine the subcritical neutron multiplication factor or to determine the sensitivity of calculations to nuclear cross section data. The interpretation of the measurement using a Monte Carlo method is based on a perturbation model for the relationship between the spectral ratio and the subcritical neutron multiplication factor. The subcritical source-driven noise measurement has advantages over other subcritical measurement methods in that reference measurements at delayed critical are not required for interpreting the measurements. Therefore, benchmark or in-situ subcritical measurements can be performed outside a critical experiment facility. Furthermore, a certain ratio of frequency spectra has been shown to be independent of detection efficiency thereby making the measurement more robust and unaffected by drifts or changes in instrumentation during the measurement. Criteria have been defined for application of this measurement method for benchmarks and in-situ subcritical measurements. An extension of the source-driven subcritical noise measurement has also been discussed that eliminates the few technical challenges for in-situ applications.

  8. Accelerator-Driven Production of Fission 99Mo

    SciTech Connect

    Youker, A. J.; Chemerisov, S. D.; Tkac, P.; Krebs, J. F.; Rotsch, D. A.; Kalensky, M.; Heltemes, T. A.; Alford, K.; Byrnes, J. P.; Gromov, R.; Hafenrichter, L.; Hebden, A. S.; Jerden, J. L.; Jonah, C. D.; Makarashvili, V.; Quigley, K. J.; Schneider, J. F.; Stepinski, D. C.; Wesolowski, K. A.; Vandegrift, G. F.

    2016-01-01

    I{esults al'e reportecl for the procluction of eeMo l'rom the accelerator-clriveu subcritical fission of a low enriohed uranir¡m (Ltju) aqì.reous solution. Phase I ol'these experiments used a 5 L r.rranyl sulfate solution with a eeMo encl-of-irracliation produotion limit of 2 Ci. The separation, recovery, and pulification of eeMo were demonstrated Lrsing the recyclecl solution. Fission product paltitioriing tl'ends will be shown for the recovery colutt'ttt, concentratiorl colurnn, and LE,U Modified Cintichem prooess. The results fi'om a 1.4 Ci oeMo production run, where the fìnal product was seut to GE Flealthcare for testing, will be highlightecl. The information gained cluring Phase ì lias signilìcantly irnpacted the clesign and implernentation of Phase ll. Phase II focuses on an end-of-irradiation ploduction of 20 Ci of eeMo and a fissior'ì power density similar to the production fàcility in a20 L LìlU uranyl sulfate solution.

  9. Development of a coupled dynamics code with transport theory capability and application to accelerator driven systems transients

    SciTech Connect

    Cahalan, J. E.; Ama, T.; Palmiotti, G.; Taiwo, T. A.; Yang, W. S.

    2000-03-09

    The VARIANT-K and DIF3D-K nodal spatial kinetics computer codes have been coupled to the SAS4A and SASSYS-1 liquid metal reactor accident and systems analysis codes. SAS4A and SASSYS-1 have been extended with the addition of heavy liquid metal (Pb and Pb-Bi) thermophysical properties, heat transfer correlations, and fluid dynamics correlations. The coupling methodology and heavy liquid metal modeling additions are described. The new computer code suite has been applied to analysis of neutron source and thermal-hydraulics transients in a model of an accelerator-driven minor actinide burner design proposed in an OECD/NEA/NSC benchmark specification. Modeling assumptions and input data generation procedures are described. Results of transient analyses are reported, with emphasis on comparison of P1 and P3 variational nodal transport theory results with nodal diffusion theory results, and on significance of spatial kinetics effects.

  10. Accelerator-driven thorium-cycle fission power

    NASA Astrophysics Data System (ADS)

    Sattarov, Akhdiyor

    2009-10-01

    A flux-coupled stack of superconducting isochronous cyclotrons could be used to drive thorium-cycle fission power. The 800 MeV proton beams produce fast neutrons through spallation, then the fast neutrons transmute the thorium into uranium and drive fission. The thorium reactor would provide GW electric power, eat its own long-lived waste, run for 7 years between core accesses, operate below criticality, and be stable against melt-down. Reserves of thorium are sufficient to provide the world's energy needs for a thousand years.

  11. A neutron booster for spallation sources—application to accelerator driven systems and isotope production

    NASA Astrophysics Data System (ADS)

    Galy, J.; Magill, J.; Van Dam, H.; Valko, J.

    2002-06-01

    One can design a critical system with fissile material in the form of a thin layer on the inner surface of a cylindrical neutron moderator such as graphite or beryllium. Recently, we have investigated the properties of critical and near critical systems based on the use of thin actinide layers of uranium, plutonium and americium. The thickness of the required fissile layer depends on the type of fissile material, its concentration in the layer and on the geometrical arrangement, but is typically in the μm-mm range. The resulting total mass of fissile material can be as low as 100 g. Thin fissile layers have a variety of applications in nuclear technology—for example in the design neutron amplifiers for medical applications and "fast" islands in thermal reactors for waste incineration. In the present paper, we investigate the properties of a neutron booster unit for spallation sources and isotope production. In those applications a layer of fissile material surrounds the spallation source. Such a module could be developed for spallation targets foreseen in the MYRRHA (L. Van Den Durpel, H. Aı̈t Abderrahim, P. D'hondt, G. Minsart, J.L. Bellefontaine, S. Bodart, B. Ponsard, F. Vermeersch, W. Wacquier. A prototype accelerator driven system in Belgium: the Myrrha project, Technical Committee Meeting on Feasibility and Motivation for Hybrid concepts for Nuclear Energy generation and Transmutation, Madrid, Spain, September 17-19, 1997 [1]). or MEGAPIE (M. Salvatores, G.S. Bauer, G. Heusener. The MEGAPIE initiative: executive outline and status as per November 1999, MPO-1-GB-6/0_GB, 1999 [2]) projects. With a neutron multiplication factor of the booster unit in the range 10-20 (i.e. with a keff of 0.9-0.95), considerably less powerful accelerators would be required to obtain the desired neutron flux. Instead of the powerful accelerators with proton energies of 1 GeV and currents of 10 mA foreseen for accelerator driven systems, similar neutron fluxes can be obtained

  12. Lead-Cooled Fast Reactor (LFR) Design: Safety, Neutronics, Thermal Hydraulics, Structural Mechanics, Fuel, Core, and Plant Design

    SciTech Connect

    Smith, C

    2010-02-22

    The idea of developing fast spectrum reactors with molten lead (or lead alloy) as a coolant is not a new one. Although initially considered in the West in the 1950s, such technology was not pursued to completion because of anticipated difficulties associated with the corrosive nature of these coolant materials. However, in the Soviet Union, such technology was actively pursued during the same time frame (1950s through the 1980s) for the specialized role of submarine propulsion. More recently, there has been a renewal of interest in the West for such technology, both for critical systems as well as for Accelerator Driven Subcritical (ADS) systems. Meanwhile, interest in the former Soviet Union, primarily Russia, has remained strong and has expanded well beyond the original limited mission of submarine propulsion. This section reviews the past and current status of LFR development.

  13. Accelerator driven gamma and fast neutron radiography test-bed at Lawrence Livermore National Laboratory

    SciTech Connect

    Tang, V.; Rusnak, B.; Falabella, S.; Hawkins, S.; McCarrick, J. F.; Wang, H.; Hall, J. M.; Ellsworth, J.

    2013-04-19

    Accelerator driven fusion gammas and fast neutrons could provide unique radiography capabilities due to their ability to produce both high and low energy mono-energetic gammas and neutrons compared with broadband bremsstrahlung based x-ray sources. The possibility of simultaneously obtaining both gamma and neutron radiographs using one source could allow complex objects composed of a large range of low to high Z materials to be imaged. In this paper we review a 4 MV RFQ accelerator driven radiography test-bed at LLNL designed to study the physics involved in applying these dual output fusion reactions for radiography applications. First experimental neutron images from a carbon target are presented.

  14. High Power Cyclotrons for Accelerator Driven System (ADS)

    NASA Astrophysics Data System (ADS)

    Calabretta, Luciano

    2012-03-01

    We present an accelerator module based on a injector cyclotron and a Superconducting Ring Cyclotron (SRC) able to accelerate H2+ molecules. H2+ molecules are extracted from the SRC stripping the binding electron by a thin carbon foil. The SRC will be able to deliver proton beam with maximum energy of 800 MeV and a maximum power of 8 MW. This module is forecasted for the DAEdALUS (Decay At rest Experiment for δcp At Laboratory for Underground Science) experiment, which is a neutrino experiment proposed by groups of MIT and Columbia University. Extensive beam dynamics studies have been carrying out in the last two years and proved the feasibility of the design. The use of H2+ molecules beam has three main advantages: 1) it reduces the space charge effects, 2) because of stripping extraction, it simplifies the extraction process w.r.t. single turn extraction and 3) we can extract more than one beam out of one SRC. A suitable upgraded version of the cyclotron module able to deliver up to 10MW beam is proposed to drive ADS. The accelerator system which is presented, consists of having three accelerators modules. Each SRC is equipped with two extraction systems delivering two beams each one with a power up to 5 MW. Each accelerator module, feeds both the two reactors at the same time. The three accelerators modules assure to maintain continuity in functioning of the two reactors. In normal operation, all the three accelerators module will deliver 6.6 MW each one, just in case one of the three accelerator module will be off, due to a fault or maintenance, the other two modules are pushed at maximum power of 10 MW. The superconducting magnetic sector of the SRC, as well as the normal conducting sector of the injector cyclotron, is calculated with the TOSCA module of OPERA3D. Here the main features of the injector cyclotron, of the SRC and the beam dynamic along the cyclotrons are presented.

  15. Assessment of americium and curium transmutation in magnesia based targets in different spectral zones of an experimental accelerator driven system

    NASA Astrophysics Data System (ADS)

    Haeck, W.; Malambu, E.; Sobolev, V. P.; Aït Abderrahim, H.

    2006-06-01

    The potential to incinerate minor actinides (MA) in a sub-critical accelerator-driven system (ADS) is a subject of study in several countries where nuclear power plants are present. The performance of the MYRRHA experimental ADS, as to the transmutation of Am and Cm in the inert matrix fuel (IMF) samples consisting of 40 vol.% (Cm0.1Am0.5Pu0.4)O1.88 fuel and 60 vol.% MgO matrix with a density of 6.077 g cm-3 in three various spectrum regions, were analysed at the belgian nuclear research centre SCK · CEN. The irradiation period of 810 effective full power days (EFPD) followed by a storage period of 2 years was considered. The ALEPH code system currently under development at SCK · CEN was used to carry out this study. The total amount of MA is shown to decrease in all three considered cases. For Am, the decrease is the largest in the reflector (89% decrease) but at the cost of a net Cm production (92% increase). In the two other positions (inside the core region), 20-30% of Am has disappeared but with a lower production of Cm (between 7% and 11%). In the reflector, a significant build-up of long-lived 245Cm, 246Cm, 247Cm and 248Cm was also observed while the production of these isotopes is 10-1000 times smaller in the core. The reduction of the Pu content is also the highest in the reflector position (41%). In the other positions the incinerated amount of Pu is much smaller: 1-5%.

  16. Combining a gas turbine modular helium reactor and an accelerator and for near total destruction of weapons grade plutonium

    NASA Astrophysics Data System (ADS)

    Baxter, A. M.; Lane, R. K.; Sherman, R.

    1995-09-01

    Fissioning surplus weapons-grade plutonium (WG-Pu) in a reactor is an effective means of rendering this stockpile non-weapons useable. In addition the enormous energy content of the plutonium is released by the fission process and can be captured to produce valuable electric power. While no fission option has been identified that can accomplish the destruction of more than about 70% of the WG-Pu without repeated reprocessing and recycling, which presents additional opportunities for diversion, the gas turbine modular helium-cooled reactor (GT-MHR), using an annular graphite core and graphite inner and outer reflectors combines the maximum plutonium destruction and highest electrical production efficiency and economics in an inherently safe system. Accelerator driven sub-critical assemblies have also been proposed for WG-Pu destruction. These systems offer almost complete WG-Pu destruction, but achieve this goal by using circulating aqueous or molten salt solutions of the fuel, with potential safety implications. By combining the GT-MHR with an accelerator-driven sub-critical MHR assembly, the best features of both systems can be merged to achieve the near total destruction of WG-Pu in an inherently safe, diversion-proof system in which the discharged fuel elements are suitable for long term high level waste storage without the need for further processing. More than 90% total plutonium destruction, and more than 99.9% Pu-239 destruction, could be achieved. The modular concept minimizes the size of each unit so that both the GT-MHR and the accelerator would be straightforward extensions of current technology.

  17. Combining a gas turbine modular helium reactor and an accelerator and for near total destruction of weapons grade plutonium

    SciTech Connect

    Baxter, A.M.; Lane, R.K.; Sherman, R.

    1995-10-01

    Fissioning surplus weapons-grade plutonium (WG-Pu) in a reactor is an effective means of rendering this stockpile non-weapons useable. In addition the enormous energy content of the plutonium is released by the fission process and can be captured to produce valuable electric power. While no fission option has been identified that can accomplish the destruction of more than about 70% of the WG-Pu without repeated reprocessing and recycling, which presents additional opportunities for diversion, the gas turbine modular helium-cooled reactor (GT-MHR), using an annular graphite core and graphite inner and outer reflectors combines the maximum plutonium destruction and highest electrical production efficiency and economics in an inherently safe system. Accelerator driven sub-critical assemblies have also been proposed for WG-Pu destruction. These systems offer almost complete WG-Pu destruction, but achieve this goal by using circulating aqueous or molten salt solutions of the fuel, with potential safety implications. By combining the GT-MHR with an accelerator-driven sub-critical MHR assembly, the best features of both systems can be merged to achieve the near total destruction of WG-Pu in an inherently safe, diversion-proof system in which the discharged fuel elements are suitable for long term high level waste storage without the need for further processing. More than 90% total plutonium destruction, and more than 99.9% Pu-239 destruction, could be achieved. The modular concept minimizes the size of each unit so that both the GT-MHR and the accelerator would be straightforward extensions of current technology.

  18. The IAEA CRP on Studies of Advanced Reactor Technology Options for Effective Incineration of Radioactive Waste

    SciTech Connect

    Maschek, W.; Chen, X.; Rineiski, A.; Schikorr, M.; Stanculescu, A.; Arien, B.; Malambu, E.; Bai, Y.; Li, J.; Wu, Y.; Zheng, S.; Chabert, C.; Peneliau, Y.; Chebeskov, A.; Dekoussar, V.; Vorotyntsev, M.; da Cruz, D.F.; Devan, K.; Gopalakrishnan, V.; Harish, R.; Mohanakrishnan, P.; Pandikumar, G.; Dulla, S.; Ravetto, P.; Feynberg, O.; Ignatiev, V.; Subbotin, V.; Surenkov, A.; Zakirov, R.; Kophazi, J.; Szieberth, M.; Morita, K.; Srivenkatesan, R.; Taczanowski, S.; Tucek, K.; Wider, H.; Vertes, P.; Uhlir, J.

    2007-07-01

    In 2003, the IAEA has initiated the Coordinated Research Project (CRP) on 'Studies of Advanced Reactor Technology Options for Effective Incineration of Radioactive Waste'. The overall objective of the CRP, performed within the framework of IAEA's Nuclear Energy Department's Technical Working Group on Fast Reactors, is to increase the capability of Member States in developing and applying advanced technologies in the area of long-lived radioactive waste utilization and transmutation. Twenty institutions from 15 Member States and one international organization participated in this CRP. The CRP concentrated on the assessment of the dynamic behavior of various transmutation systems. The reactor systems investigated comprise critical reactors, sub-critical accelerator driven systems with heavy liquid metal and gas cooling, critical molten salt systems, and hybrid fusion/fission systems. Both fertile and fertile-free fuel options have been investigated. Apart from the benchmarking of steady state core configurations (including the investigation of transmutation potential, burn-up behavior and decay heat of minor actinide (MA) bearing fuels), the CRP participants determined the safety coefficients for the individual systems and, in a second stage, performed transient analyses which reflected the generic safety related behavior of the various reactors types. (authors)

  19. Subcritical transmutation of spent nuclear fuel

    NASA Astrophysics Data System (ADS)

    Sommer, Christopher M.

    2011-07-01

    A series of fuel cycle simulations were performed using CEA's reactor physics code ERANOS 2.0 to analyze the transmutation performance of the Subcritical Advanced Burner Reactor (SABR). SABR is a fusion-fission hybrid reactor that combines the leading sodium cooled fast reactor technology with the leading tokamak plasma technology based on ITER physics. Two general fuel cycles were considered for the SABR system. The first fuel cycle is one in which all of the transuranics from light water reactors are burned in SABR. The second fuel cycle is a minor actinide burning fuel cycle in which all of the minor actinides and some of the plutonium produced in light water reactors are burned in SABR, with the excess plutonium being set aside for starting up fast reactors in the future. The minor actinide burning fuel cycle is being considered in European Scenario Studies. The fuel cycles were evaluated on the basis of TRU/MA transmutation rate, power profile, accumulated radiation damage, and decay heat to the repository. Each of the fuel cycles are compared against each other, and the minor actinide burning fuel cycles are compared against the EFIT transmutation system, and a low conversion ratio fast reactor.

  20. Accelerator-driven nuclear synergetic systems-an overview of the research activities in Sweden

    SciTech Connect

    Conde, H.; Baecklin, A.; Carius, S.

    1995-10-01

    The rapid development of the accelerator technology which enables the construction of reliable and very intense neutron sources has initiated a growing interest for accelerator driven transmutation systems in Sweden. After the Specialist Meeting on Accelerator-Driven Transmutation Technology for Radwaste and other Applications on 24-28 June 1991 at Saltsjoebaden, Sweden, the research activities oriented towards accelerator-driven systems have been started at several research centers in Sweden. Also the governmental agencies responsible for the spent fuel policy showed a positive attitude to these activities through a limited financial support, particularly for studies of the safety aspects of these systems. Also the nuclear power industry and utilities show a positive interest in the research on these concepts. The present paper presents an overview of the Swedish research activities on accelerator-driven systems and the proposed future coordination, organizations and prospects for this research in the context of the national nuclear energy and spent fuel policy. The Swedish perspective for international cooperation is also described.

  1. Design and testing of a dc ion injector suitable for accelerator-driven transmutation

    SciTech Connect

    Schneider, J.D.; Meyer, E.; Stevens, R.R. Jr.; Hansborough, L.; Sherman, J.

    1994-08-01

    For a number of years, Los Alamos have collaborated with a team of experimentalists at Chalk River Labs who were pursuing the development of the front end of a high power cw proton accelerator. With the help of internal laboratory funding and modest defense conversion funds, we have set up and operated the accelerator at Los Alamos Operational equipment includes a slightly modified Chalk River Injector Test Stand (CRITS) including a 50 keV proton injector and a 1.25 MeV radio-frequency quadrupole (RFQ) with a klystrode rf power system. Many of the challenges involved in operating an rf linear accelerator to provide neutrons for an accelerator-driven reactor are encountered at the front (low energy) end of this system. The formation of the ion beam, the control of the beam parameters, and the focusing and matching of a highly space-charge-dominated beam are major problems. To address the operating problems in this critical front end, the Accelerator Operations and Technology Division at the Los Alamos National Laboratory has designed the APDF (Accelerator Prototype Demonstration Facility). The front end of this facility is a 75 keV, high-current, ion injector which has been assembled and is now being tested. This paper discusses the design modifications required in going from the 50 keV CRITS injector to the higher current, 75 keV injector. Major innovative changes were made in the design of this injector. This design eliminates all the control electronics and most of the ion source equipment at high potential. Also, a new, high-quality, ion-extractor system has been built. A dual-solenoid lens will be used in the low energy beam transport (LEBT) line to provide the capability of matching the extracted beam to a high-current ADTT linac. This new injector is the first piece of hardware in the APDF program and will be used to develop the long-term, reliable cw beam operation required for ADIT applications.

  2. Reaction kinetics of cellulose hydrolysis in subcritical and supercritical water

    NASA Astrophysics Data System (ADS)

    Olanrewaju, Kazeem Bode

    The uncertainties in the continuous supply of fossil fuels from the crisis-ridden oil-rich region of the world is fast shifting focus on the need to utilize cellulosic biomass and develop more efficient technologies for its conversion to fuels and chemicals. One such technology is the rapid degradation of cellulose in supercritical water without the need for an enzyme or inorganic catalyst such as acid. This project focused on the study of reaction kinetics of cellulose hydrolysis in subcritical and supercritical water. Cellulose reactions at hydrothermal conditions can proceed via the homogeneous route involving dissolution and hydrolysis or the heterogeneous path of surface hydrolysis. The work is divided into three main parts. First, the detailed kinetic analysis of cellulose reactions in micro- and tubular reactors was conducted. Reaction kinetics models were applied, and kinetics parameters at both subcritical and supercritical conditions were evaluated. The second major task was the evaluation of yields of water soluble hydrolysates obtained from the hydrolysis of cellulose and starch in hydrothermal reactors. Lastly, changes in molecular weight distribution due to hydrothermolytic degradation of cellulose were investigated. These changes were also simulated based on different modes of scission, and the pattern generated from simulation was compared with the distribution pattern from experiments. For a better understanding of the reaction kinetics of cellulose in subcritical and supercritical water, a series of reactions was conducted in the microreactor. Hydrolysis of cellulose was performed at subcritical temperatures ranging from 270 to 340 °C (tau = 0.40--0.88 s). For the dissolution of cellulose, the reaction was conducted at supercritical temperatures ranging from 375 to 395 °C (tau = 0.27--0.44 s). The operating pressure for the reactions at both subcritical and supercritical conditions was 5000 psig. The results show that the rate-limiting step in

  3. Evaluations for the choice of the best target material in a accelerator-driven reactor

    SciTech Connect

    Neuhold, P.

    1995-10-01

    From the point of view of the overall credibility of the machine the choice of the best target material play a fundamental role. That has to fulfill at least three requirements: (1) the maximum number of neutrons produced per incident proton; (2) the maximum melting point; (3) the minimum activation under neutron irradiation. A number of different candidates can be investigated, keeping in mind that the first requirement is roughly fulfilled by high atomic number elements: the most popular among them appear to be W, Pb, and Np. While the characteristics for the second point are well known (3410C, 327C and 640C), as well as many evaluations are done about the first point, even if showing numbers ranging roughly a factor of 2 between the lowest and the highest ones, poor attention instead has been given to the third one. As far as the operation/maintenance of the machine is concerned, is important to know the dose rate of the target due to its neutron activation. According to the author`s calculations, for example after one year of 800 MeV/62.5 mA proton irradiation of W, one can have, after one day of decay, dose rates as high as 2*10**6 Sv/hr, cumulative of the effects due to the direct proton beam and to the arising neutron flux. The author made use of the codes MSMPN, ANITA for the neutron activation analysis and of NMTC, ORIGEN for the proton interaction analysis. In particular it`s worth noting how dramatic differences can arise from different isotopic composition, that is for example between natural W or only W-186, due to the very different behavior of the daughter elements as decay time and gamma-energy. For example the dose rate due to the neutron activation alone, after one month of decay, for natural W is a factor of 500 greater than for W-186.

  4. Reactor physics studies for the Advanced Fuel Cycle Initiative (AFCI) Reactor-Accelerator Coupling Experiments (RACE) Project

    NASA Astrophysics Data System (ADS)

    Stankovskiy, Evgeny Yuryevich

    In the recently completed RACE Project of the AFCI, accelerator-driven subcritical systems (ADS) experiments were conducted to develop technology of coupling accelerators to nuclear reactors. In these experiments electron accelerators induced photon-neutron reactions in heavy-metal targets to initiate fission reactions in ADS. Although the Idaho State University (ISU) RACE ADS was constructed only to develop measurement techniques for advanced experiments, many reactor kinetics experiments were conducted there. In the research reported in this dissertation, a method was developed to calculate kinetics parameters for measurement and calculation of the reactivity of ADS, a safety parameter that is necessary for control and monitoring of power production. Reactivity is measured in units of fraction of delayed versus prompt neutron from fission, a quantity that cannot be directly measured in far-subcritical reactors such as the ISU RACE configuration. A new technique is reported herein to calculate it accurately and to predict kinetic behavior of a far-subcritical ADS. Experiments conducted at ISU are first described and experimental data are presented before development of the kinetic theory used in the new computational method. Because of the complexity of the ISU ADS, the Monte-Carlo method as applied in the MCNP code is most suitable for modeling reactor kinetics. However, the standard method of calculating the delayed neutron fraction produces inaccurate values. A new method was developed and used herein to evaluate actual experiments. An advantage of this method is that its efficiency is independent of the fission yield of delayed neutrons, which makes it suitable for fuel with a minor actinide component (e.g. transmutation fuels). The implementation of this method is based on a correlated sampling technique which allows the accurate evaluation of delayed and prompt neutrons. The validity of the obtained results is indicated by good agreement between experimental

  5. YALINA-booster subcritical assembly pulsed-neutron experiments : data processing and spatial corrections.

    SciTech Connect

    Cao, Y.; Gohar, Y.; Nuclear Engineering Division

    2010-10-11

    The YALINA-Booster experiments and analyses are part of the collaboration between Argonne National Laboratory of USA and the Joint Institute for Power & Nuclear Research - SOSNY of Belarus for studying the physics of accelerator driven systems for nuclear energy applications using low enriched uranium. The YALINA-Booster subcritical assembly is utilized for studying the kinetics of accelerator driven systems with its highly intensive D-T or D-D pulsed neutron source. In particular, the pulsed neutron methods are used to determine the reactivity of the subcritical system. This report examines the pulsed-neutron experiments performed in the YALINA-Booster facility with different configurations for the subcritical assembly. The 1141 configuration with 90% U-235 fuel and the 1185 configuration with 36% or 21% U-235 fuel are examined. The Sjoestrand area-ratio method is utilized to determine the reactivities of the different configurations. The linear regression method is applied to obtain the prompt neutron decay constants from the pulsed-neutron experimental data. The reactivity values obtained from the experimental data are shown to be dependent on the detector locations inside the subcritical assembly and the types of detector used for the measurements. In this report, Bell's spatial correction factors are calculated based on a Monte Carlo model to remove the detector dependences. The large differences between the reactivity values given by the detectors in the fast neutron zone of the YALINA-Booster are reduced after applying the spatial corrections. In addition, the estimated reactivity values after the spatial corrections are much less spatially dependent.

  6. Subcritical growth of natural hydraulic fractures

    NASA Astrophysics Data System (ADS)

    Garagash, D.

    2014-12-01

    Joints are the most common example of brittle tensile failure in the crust. Their genesis at depth is linked to the natural hydraulic fracturing, which requires pore fluid pressure in excess of the minimum in situ stress [Pollard and Aidyn, JSG1988]. Depending on the geological setting, high pore pressure can result form burial compaction of interbedded strata, diagenesis, or tectonics. Common to these loading scenarios is slow build-up of pore pressure over a geological timescale, until conditions for initiation of crack growth are met on favorably oriented/sized flaws. The flaws can vary in size from grain-size cracks in igneous rocks to a fossil-size flaws in clastic rock, and once activated, are inferred to propagate mostly subcritically [Segall JGR 1984; Olson JGR 1993]. Despite many observational studies of natural hydraulic fractures, the modeling attempts appear to be few [Renshaw and Harvey JGR 1994]. Here, we use boundary integral formulation for the pore fluid inflow from the permeable rock into a propagating joint [Berchenko et al. IJRMMS 1997] coupled with the criteria for subcritical propagation assisted by the environmental effects of pore fluid at the crack tip to solve for the evolution of a penny-shape joint, which, in interbedded rock, may eventually evolve to short-blade geometry (propagation confined to a bed). Initial growth is exceedingly slow, paced by the stress corrosion reaction kinetics at the crack tip. During this stage the crack is fully-drained (i.e. the fluid pressure in the crack is equilibrated with the ambient pore pressure). This "slow" stage is followed by a rapid acceleration, driven by the increase of the mechanical stress intensity factor with the crack length, towards the terminal joint velocity. We provide an analytical expression for the latter as a function of the rock diffusivity, net pressure loading at the initiation (or flaw lengthscale), and parameters describing resistance to fracture growth. Due to a much slower

  7. LANL sunnyside experiment: Study of neutron production in accelerator-driven targets

    SciTech Connect

    Morgan, G.; Butler, G.; Cappiello, M.

    1995-10-01

    Measurements have been made of the neutron production in prototypic targets for accelerator driven systems. Studies were conducted on four target assemblies containing lead, lithium, tungsten, and a thorium-salt mixture. Integral data on total neutron production were obtained as well as more differential data on neutron leakage and neutron flux profiles in the blanket/moderator region. Data analysis on total neutron production is complete and shows excellent agreement with calculations using the LAHET/MCNP code system.

  8. LANL sunnyside experiment: Study of neutron production in accelerator-driven targets

    NASA Astrophysics Data System (ADS)

    Morgan, G.; Butler, G.; Cappiello, M.; Carius, S.; Daemen, L.; DeVolder, B.; Frehaut, J.; Goulding, C.; Grace, R.; Green, R.; Lisowski, P.; Littleton, P.; King, J.; King, N.; Prael, R.; Stratton, T.; Turner, S.; Ullmann, J.; Venneri, F.; Yates, M.

    1995-09-01

    Measurements have been made of the neutron production in prototypic targets for accelerator driven systems. Studies were conducted on four target assemblies containing lead, lithium, tungsten, and a thorium-salt mixture. Integral data on total neutron production were obtained as well as more differential data on neutron leakage and neutron flux profiles in the blanket/moderator region. Data analysis on total neutron production is complete and shows excellent agreement with calculations using the LAHET/MCNP code system.

  9. Nuclear physics information needed for accelerator driven transmutation of nuclear waste

    SciTech Connect

    Lisowski, P.W.; Bowman, C.D.; Arthur, E.D.; Young, P.G.

    1991-01-01

    There is renewed interest in using accelerator driven neutron sources to address the problem of high-level long-lived nuclear waste. Several laboratories have developed systems that may have a significant impact on the future use of nuclear power, adding options for dealing with long-lived actinide wastes and fission products, and for power production. This paper describes a new Los Alamos concept using thermal neutrons and examines the nuclear data requirements. 7 refs., 3 figs., 1 tab.

  10. An innovative accelerator-driven inertial electrostatic confinement device using converging ion beams

    SciTech Connect

    Bauer, T. H.; Wigeland, R. A.

    1999-12-08

    Fundamental physics issues facing development of fusion power on a small-scale are assessed with emphasis on the idea of Inertial Electrostatic Confinement (IEC). The authors propose a new concept of accelerator-driven IEC fusion, termed Converging Beam Inertial Electrostatic Confinement (CB-IEC). CB-IEC offers a number of innovative features that make it an attractive pathway toward resolving fundamental physics issues and assessing the ultimate viability of the IEC concept for power generation.

  11. Subcritical crack growth in marble

    NASA Astrophysics Data System (ADS)

    Nara, Yoshitaka; Nishida, Yuki; Toshinori, Ii; Harui, Tomoki; Tanaka, Mayu; Kashiwaya, Koki

    2016-04-01

    It is essential to study time-dependent deformation and fracturing in various rock materials to prevent natural hazards related to the failure of a rock mass. In addition, information of time-dependent fracturing is essential to ensure the long-term stability of a rock mass surrounding various structures. Subcritical crack growth is one of the main causes of time-dependent fracturing in rock. It is known that subcritical crack growth is influenced by not only stress but also surrounding environment. Studies of subcritical crack growth have been widely conducted for silicate rocks such as igneous rocks and sandstones. By contrast, information of subcritical crack growth in carbonate rocks is not enough. Specifically, influence of surrounding environment on subcritical crack growth in carbonate rock should be clarified to ensure the long-term stability of a rock mass. In this study, subcritical crack growth in marble was investigated. Especially, the influence of the temperature, relative humidity and water on subcritical crack growth in marble is investigated. As rock samples, marbles obtained in Skopje-City in Macedonia and Carrara-City in Italy were used. To measure subcritical crack growth, we used the load relaxation method of the double-torsion (DT) test. All measurements by DT test were conducted under controlled temperature and relative humidity. For both marbles, it was shown that the crack velocity in marble in air increased with increasing relative humidity at a constant temperature. Additionally, the crack velocity in water was much higher than that in air. It was also found that the crack velocity increased with increasing temperature. It is considered that temperature and water have significant influences on subcritical crack growth in marble. For Carrara marble in air, it was recognized that the value of subcritical crack growth index became low when the crack velocity was higher than 10-4 m/s. This is similar to Region II of subcritical crack growth

  12. Increasing Fuel Utilization of Breed and Burn Reactors

    NASA Astrophysics Data System (ADS)

    Di Sanzo, Christian Diego

    Breed and Burn reactors (B&B), also referred to Traveling Wave Reactors, are fast spectrum reactors that can be fed indefinitely with depleted uranium only, once criticality is achieved without the need for fuel reprocessing. Radiation damage to the fuel cladding limits the fuel utilization of B&B reactors to ˜ 18-20% FIMA (Fissions of Initial Metal Atoms) -- the minimum burnup required for sustaining the B&B mode of operation. The fuel discharged from this type of cores contain ˜ 10% fissile plutonium. Such a high plutonium content poses environmental and proliferation concerns, but makes it possible to utilize the fuel for further energy production. The objectives of the research reported in this dissertation are to analyze the fuel cycle of B&B reactors and study new strategies to extend the fuel utilization beyond ˜ 18-20% FIMA. First, the B&B reactor physics is examined while recycling the fuel every 20% FIMA via a limited separation processing, using either the melt refining or AIROX dry processes. It was found that the maximum attainable burnup varies from 54% to 58% FIMA -- depending on the recycling process and on the fraction of neutrons lost via leakage and reactivity control. In Chapter 3 the discharge fuel characteristics of B&B reactors operating at 20% FIMA and 55% FIMA is analyzed and compared. It is found that the 20% FIMA reactor discharges a fuel with about ˜ 80% fissile plutonium over total plutonium content. Subsequently a new strategy of minimal reconditioning, called double cladding is proposed to extend the fuel utilization in specifically designed second-tier reactors. It is found that with this strategy it is possible to increase fuel utilization to 30% in a sodium fast reactor and up to 40% when a subcritical B&B core is driven by an accelerator-driven spallation neutron source. Lastly, a fuel cycle using Pressurized Water Reactors (PWR) to reduce the plutonium content of discharged B&B reactors is analyzed. It was found that it is

  13. Radiation-induced segregation in materials: Implications for accelerator-driven neutron source applications

    SciTech Connect

    Faulkner, R.B.; Song, S.

    1995-10-01

    This paper reviews exisiting models for radiation-induced segregation to microstrucural interfaces and surfaces. It indicates how the models have been successfully used in the past in neutron irradiation situations and how they may be modified to account for accelerator-driven RIS. The predictions of the models suggest that any impurity with large misfit will suffer RIS and that the effect is heightened as radiation damage increases. The paper suggests methods to utilise the RIS in transmutation technology by dynamically segregating long life nuclides to preferred sites in the microstructure so that subsequent transmutations occur with maximum efficiency.

  14. Summary of the Accelerator-Driven Transmutation Technologies and their applications

    SciTech Connect

    Wanger, T.P.

    1995-10-01

    During the past 15 years many advances have been made in the technology of high-power accelerators, and in the understanding of the beam-physics issues associated with their high-performance requirements. These developments have contributed significantly to the high level of confidence in the practicality of the applications that were the central point of the international Accelerator-Driven Transmutation Technologies (ADTT) Conference. Even so, there are many accelerator topics that needed to be addressed, and the Conference provided the opportunity to address these issues.

  15. Chemistry technology base and fuel cycle of the Los Alamos accelerator-driven transmutation system

    SciTech Connect

    Williamson, M.A.

    1997-12-01

    This paper provides a brief overview of the Los Alamos accelerator-driven transmutation system, a description of the pyrochemistry technology base and the fuel cycle for the system. The pyrochemistry technology base consists of four processes: direct oxide reduction, reductive extraction, electrorefining, and electrowinning. Each process and its utility is described. The fuel cycle is described for a liquid metal-based system with the focus being the conversion of commercial spent nuclear fuel to fuel for the transmutation system. Fission product separation and actinide recycle processes are also described.

  16. Important requirements for RF generators for Accelerator-Driven Transmutation Technologies (ADTT)

    SciTech Connect

    Lynch, M.T.; Tallerico, P.J.; Lawrence, G.P.

    1994-09-01

    All Accelerator-Driven Transmutation applications require very large amounts of RF Power. For example, one version of a Plutonium burning system requires an 800-MeV, 80-mA, proton accelerator running at 100% duty factor. This accelerator requires approximately 110-MW of continuous RF power if one assumes only 10% reserve power for control of the accelerator fields. In fact, to minimize beam spill, the RF controls may need as much as 15 to 20% of reserve power. In addition, unlike an electron accelerator in which the beam is relativistic, a failed RF station can disturb the synchronism of the beam, possibly shutting down the entire accelerator. These issues and more lead to a set of requirements for the RF generators which are stringent, and in some cases, conflicting. In this paper, we will describe the issues and requirements, and outline a plan for RF generator development to meet the needs of the Accelerator-Driven Transmutation Technologies. The key issues which will be discussed include: operating efficiency, operating linearity, effect on the input power grid, bandwidth, gain, reliability, operating voltage, and operating current.

  17. Dynamics of electron injection and acceleration driven by laser wakefield in tailored density profiles

    NASA Astrophysics Data System (ADS)

    Lee, P.; Maynard, G.; Audet, T. L.; Cros, B.; Lehe, R.; Vay, J.-L.

    2016-11-01

    The dynamics of electron acceleration driven by laser wakefield is studied in detail using the particle-in-cell code WARP with the objective to generate high-quality electron bunches with narrow energy spread and small emittance, relevant for the electron injector of a multistage accelerator. Simulation results, using experimentally achievable parameters, show that electron bunches with an energy spread of ˜11 % can be obtained by using an ionization-induced injection mechanism in a mm-scale length plasma. By controlling the focusing of a moderate laser power and tailoring the longitudinal plasma density profile, the electron injection beginning and end positions can be adjusted, while the electron energy can be finely tuned in the last acceleration section.

  18. Dynamics of electron injection and acceleration driven by laser wakefield in tailored density profiles

    DOE PAGES

    Lee, Patrick; Maynard, G.; Audet, T. L.; ...

    2016-11-16

    The dynamics of electron acceleration driven by laser wakefield is studied in detail using the particle-in-cell code WARP with the objective to generate high-quality electron bunches with narrow energy spread and small emittance, relevant for the electron injector of a multistage accelerator. Simulation results, using experimentally achievable parameters, show that electron bunches with an energy spread of ~11% can be obtained by using an ionization-induced injection mechanism in a mm-scale length plasma. By controlling the focusing of a moderate laser power and tailoring the longitudinal plasma density profile, the electron injection beginning and end positions can be adjusted, while themore » electron energy can be finely tuned in the last acceleration section.« less

  19. Towards the final BSA modeling for the accelerator-driven BNCT facility at INFN LNL.

    PubMed

    Ceballos, C; Esposito, J; Agosteo, S; Colautti, P; Conte, V; Moro, D; Pola, A

    2011-12-01

    Some remarkable advances have been made in the last years on the SPES-BNCT project of the Istituto Nazionale di Fisica Nucleare (INFN) towards the development of the accelerator-driven thermal neutron beam facility at the Legnaro National Laboratories (LNL), aimed at the BNCT experimental treatment of extended skin melanoma. The compact neutron source will be produced via the (9)Be(p,xn) reactions using the 5 MeV, 30 mA beam driven by the RFQ accelerator, whose modules construction has been recently completed, into a thick beryllium target prototype already available. The Beam Shaping Assembly (BSA) final modeling, using both neutron converter and the new, detailed, Be(p,xn) neutron yield spectra at 5 MeV energy recently measured at the CN Van de Graaff accelerator at LNL, is summarized here. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. Application of the EA-MC Code Package to the Design of Accelerator-Driven Systems

    NASA Astrophysics Data System (ADS)

    Kadi, Y.

    The Monte Carlo method (MC) is currently used to simulate the real time behaviour of a sub-critical system [1,2] like for instance the Energy Amplifier Demonstration Facility (EADF). The advantage of this method is that it can be made intrinsically free of unwanted approximations, provided that (i) the relevant cross sections are well known - a necessity of any method of computation - and (ii) the actual geometry is sufficiently well modeled. For instance a variety of processes with many different particles in the final state as well as detailed angular distributions can be taken correctly into account and there is no real limit to the complexity of the geometry and the number of separate components. This technique also ensures continuity between the simulation of the high energy, proton induced initial cascade, for which MC is the only formalism [3,4], and the subsequent sub-critical, fission dominated nuclear cascade. Therefore MC constitutes a superb tool to simulate realistically both the ordinary operation and a variety of transients in sub-critical or critical systems.

  1. Neutron spatial flux profile measurement in compact subcritical system using miniature neutron detectors

    NASA Astrophysics Data System (ADS)

    Shukla, Mayank; Desai, Shraddha S.; Roy, Tushar; Kashyap, Yogesh; Ray, Nirmal; Bajpai, Shefali; Patel, Tarun; Sinha, Amar

    2015-02-01

    A zero power multiplying assembly in subcritical regime serves as a benchmark for validating subcritical reactor physics. The utilization of a subcritical assembly for the determination of nuclear parameters in a multiplying medium requires a well-defined neutron flux to carry out the experiments. For this it is necessary to know the neutron flux profile inside a subcritical system. A compact subcritical assembly BRAHMMA has been developed in India. The experimental channels in this assembly are typically less than 8 mm diameter. This requires use of miniature detectors that can be mounted in these experimental channels. In this article we present the thermal neutron flux profile measurement in a compact subcritical system using indigenously developed miniature gas filled neutron detectors. These detectors were specially designed and fabricated considering the restrictive dimensional requirements of the subcritical core. Detectors of non-standard size with various sensitivities, from 0.4 to 0.001 cps/nv were used for neutron flux of interest ranging from 103 to 107 n-cm-2 s-1. A comparison of measured neutron flux using these detectors and simulated Monte Carlo calculations are also presented in this article.

  2. REACTOR

    DOEpatents

    Szilard, L.

    1963-09-10

    A breeder reactor is described, including a mass of fissionable material that is less than critical with respect to unmoderated neutrons and greater than critical with respect to neutrons of average energies substantially greater than thermal, a coolant selected from sodium or sodium--potassium alloys, a control liquid selected from lead or lead--bismuth alloys, and means for varying the quantity of control liquid in the reactor. (AEC)

  3. REACTOR

    DOEpatents

    Christy, R.F.

    1961-07-25

    A means is described for co-relating the essential physical requirements of a fission chain reaction in order that practical, compact, and easily controllable reactors can be built. These objects are obtained by employing a composition of fissionsble isotope and moderator in fluid form in which the amount of fissionsble isotcpe present governs the reaction. The size of the reactor is no longer a critical factor, the new criterion being the concentration of the fissionable isotope.

  4. A beamline systems model for Accelerator-Driven Transmutation Technology (ADTT) facilities

    SciTech Connect

    Todd, A.M.M.; Paulson, C.C.; Peacock, M.A.

    1995-10-01

    A beamline systems code, that is being developed for Accelerator-Driven Transmutation Technology (ADTT) facility trade studies, is described. The overall program is a joint Grumman, G.H. Gillespie Associates (GHGA) and Los Alamos National Laboratory effort. The GHGA Accelerator Systems Model (ASM) has been adopted as the framework on which this effort is based. Relevant accelerator and beam transport models from earlier Grumman systems codes are being adapted to this framework. Preliminary physics and engineering models for each ADTT beamline component have been constructed. Examples noted include a Bridge Coupled Drift Tube Linac (BCDTL) and the accelerator thermal system. A decision has been made to confine the ASM framework principally to beamline modeling, while detailed target/blanket, balance-of-plant and facility costing analysis will be performed externally. An interfacing external balance-of-plant and facility costing model, which will permit the performance of iterative facility trade studies, is under separate development. An ABC (Accelerator Based Conversion) example is used to highlight the present models and capabilities.

  5. Microwave Ion Source and Beam Injection for an Accelerator-drivenNeutron Source

    SciTech Connect

    Vainionpaa, J.H.; Gough, R.; Hoff, M.; Kwan, J.W.; Ludewigt,B.A.; Regis, M.J.; Wallig, J.G.; Wells, R.

    2007-02-15

    An over-dense microwave driven ion source capable ofproducing deuterium (or hydrogen) beams at 100-200 mA/cm2 and with atomicfraction>90 percent was designed and tested with an electrostaticlow energy beam transport section (LEBT). This ion source wasincorporatedinto the design of an Accelerator Driven Neutron Source(ADNS). The other key components in the ADNS include a 6 MeV RFQaccelerator, a beam bending and scanning system, and a deuterium gastarget. In this design a 40 mA D+ beam is produced from a 6 mm diameteraperture using a 60 kV extraction voltage. The LEBT section consists of 5electrodes arranged to form 2 Einzel lenses that focus the beam into theRFQ entrance. To create the ECR condition, 2 induction coils are used tocreate ~; 875 Gauss on axis inside the source chamber. To prevent HVbreakdown in the LEBT a magnetic field clamp is necessary to minimize thefield in this region. Matching of the microwave power from the waveguideto the plasma is done by an autotuner. We observed significantimprovement of the beam quality after installing a boron nitride linerinside the ion source. The measured emittance data are compared withPBGUNS simulations.

  6. REACTOR

    DOEpatents

    Roman, W.G.

    1961-06-27

    A pressurized water reactor in which automatic control is achieved by varying the average density of the liquid moderator-cooiant is patented. Density is controlled by the temperature and power level of the reactor ftself. This control can be effected by the use of either plate, pellet, or tubular fuel elements. The fuel elements are disposed between upper and lower coolant plenum chambers and are designed to permit unrestricted coolant flow. The control chamber has an inlet opening communicating with the lower coolant plenum chamber and a restricted vapor vent communicating with the upper coolant plenum chamber. Thus, a variation in temperature of the fuel elements will cause a variation in the average moderator density in the chamber which directly affects the power level of the reactor.

  7. REACTORS

    DOEpatents

    Spitzer, L. Jr.

    1961-10-01

    Thermonuclear reactors, methods, and apparatus are described for controlling and confining high temperature plasma. Main axial confining coils in combination with helical windings provide a rotational transform that avoids the necessity of a figure-eight shaped reactor tube. The helical windings provide a multipolar helical magnetic field transverse to the axis of the main axial confining coils so as to improve the effectiveness of the confining field by counteracting the tendency of the more central lines of force in the stellarator tube to exchange positions with the magnetic lines of force nearer the walls of the tube. (AEC)

  8. A useful observable for estimating keff in fast subcritical systems

    NASA Astrophysics Data System (ADS)

    Saracco, Paolo; Borreani, Walter; Chersola, Davide; Lomonaco, Guglielmo; Ricco, Gianni; Ripani, Marco

    2017-09-01

    The neutron multiplication factor keff is a key quantity to characterize subcritical neutron multiplying devices and for understanting their physical behaviour, being related to the fundamental eigenvalue of Boltzmann transport equation. Both the maximum available power - and all quantities related to it, like, e.g. the effectiveness in burning nuclear wastes - as well as reactor kinetics and dynamics depend on keff. Nevertheless, keff is not directly measurable and its determination results from the solution of an inverse problem: minimizing model dependence of the solution for keff then becomes a critical issue, relevant both for practical and theoretical reasons.

  9. Benchmarking shielding simulations for an accelerator-driven spallation neutron source

    DOE PAGES

    Cherkashyna, Nataliia; Di Julio, Douglas D.; Panzner, Tobias; ...

    2015-08-09

    The shielding at an accelerator-driven spallation neutron facility plays a critical role in the performance of the neutron scattering instruments, the overall safety, and the total cost of the facility. Accurate simulation of shielding components is thus key for the design of upcoming facilities, such as the European Spallation Source (ESS), currently in construction in Lund, Sweden. In this paper, we present a comparative study between the measured and the simulated neutron background at the Swiss Spallation Neutron Source (SINQ), at the Paul Scherrer Institute (PSI), Villigen, Switzerland. The measurements were carried out at several positions along the SINQ monolithmore » wall with the neutron dosimeter WENDI-2, which has a well-characterized response up to 5 GeV. The simulations were performed using the Monte-Carlo radiation transport code Geant4, and include a complete transport from the proton beam to the measurement locations in a single calculation. An agreement between measurements and simulations is about a factor of 2 for the points where the measured radiation dose is above the background level, which is a satisfactory result for such simulations spanning many energy regimes, different physics processes and transport through several meters of shielding materials. The neutrons contributing to the radiation field emanating from the monolith were confirmed to originate from neutrons with energies above 1 MeV in the target region. The current work validates Geant4 as being well suited for deep-shielding calculations at accelerator-based spallation sources. We also extrapolate what the simulated flux levels might imply for short (several tens of meters) instruments at ESS.« less

  10. Accelerator driven neutron source design via beryllium target and (208)Pb moderator for boron neutron capture therapy in alternative treatment strategy by Monte Carlo method.

    PubMed

    Khorshidi, Abdollah

    2017-01-01

    The reactor has increased its area of application into medicine especially boron neutron capture therapy (BNCT); however, accelerator-driven neutron sources can be used for therapy purposes. The present study aimed to discuss an alternative method in BNCT functions by a small cyclotron with low current protons based on Karaj cyclotron in Iran. An epithermal neutron spectrum generator was simulated with 30 MeV proton energy for BNCT purposes. A low current of 300 μA of the proton beam in spallation target concept via 9Be target was accomplished to model neutron spectrum using 208Pb moderator around the target. The graphite reflector and dual layer collimator were planned to prevent and collimate the neutrons produced from proton interactions. Neutron yield per proton, energy distribution, flux, and dose components in the simulated head phantom were estimated by MCNPX code. The neutron beam quality was investigated by diverse filters thicknesses. The maximum epithermal flux transpired using Fluental, Fe, Li, and Bi filters with thicknesses of 7.4, 3, 0.5, and 4 cm, respectively; as well as the epithermal to thermal neutron flux ratio was 161. Results demonstrated that the induced neutrons from a low energy and low current proton may be effective in tumor therapy using 208Pb moderator with average lethargy and also graphite reflector with low absorption cross section to keep the generated neutrons. Combination of spallation-based BNCT and proton therapy can be especially effective, if a high beam intensity cyclotron becomes available.

  11. Applications of compact accelerator-driven neutron sources: An updated assessment from the perspective of materials research in Italy

    DOE PAGES

    Andreani, C.; Anderson, I. S.; Carpenter, J. M.; ...

    2014-12-24

    In 2005 the International Atomic Energy Agency (IAEA) in Vienna published a report [1] on ‘Development Opportunities of Small and Medium Scale Accelerator Driven Neutron Sources’ which summarized the prospect of smaller sources in supporting the large spallation neutron sources for materials characterization and instrumentation, a theme advocated by Bauer, Clausen, Mank, and Mulhauser in previous publications [2-4]. In 2010 the Union for Compact Accelerator-driven Neutron Sources (UCANS) was established [5], galvanizing cross-disciplinary collaborations on new source and neutronics development and expanded applications based on both slow-neutron scattering and other neutron-matter interactions of neutron energies ranging from 10⁻⁶ to 10²more » MeV [6]. Here, we first cover the recent development of ongoing and prospective projects of compact accelerator-driven neutron sources (CANS) but concentrate on prospective accelerators currently proposed in Italy. Two active R&D topics, irradiation effects on electronics and cultural heritage studies, are chosen to illustrate the impact of state-of-the-art CANS on these programs with respect to the characteristics and complementarity of the accelerator and neutronics systems as well as instrumentation development.« less

  12. Applications of compact accelerator-driven neutron sources: An updated assessment from the perspective of materials research in Italy

    SciTech Connect

    Andreani, C.; Anderson, I. S.; Carpenter, J. M.; Festa, G.; Gorini, G.; Loong, C. -K.; Senesi, R.

    2014-12-24

    In 2005 the International Atomic Energy Agency (IAEA) in Vienna published a report [1] on ‘Development Opportunities of Small and Medium Scale Accelerator Driven Neutron Sources’ which summarized the prospect of smaller sources in supporting the large spallation neutron sources for materials characterization and instrumentation, a theme advocated by Bauer, Clausen, Mank, and Mulhauser in previous publications [2-4]. In 2010 the Union for Compact Accelerator-driven Neutron Sources (UCANS) was established [5], galvanizing cross-disciplinary collaborations on new source and neutronics development and expanded applications based on both slow-neutron scattering and other neutron-matter interactions of neutron energies ranging from 10⁻⁶ to 10² MeV [6]. Here, we first cover the recent development of ongoing and prospective projects of compact accelerator-driven neutron sources (CANS) but concentrate on prospective accelerators currently proposed in Italy. Two active R&D topics, irradiation effects on electronics and cultural heritage studies, are chosen to illustrate the impact of state-of-the-art CANS on these programs with respect to the characteristics and complementarity of the accelerator and neutronics systems as well as instrumentation development.

  13. Benchmarking criticality safety calculations with subcritical experiments

    SciTech Connect

    Mihalczo, J.T.

    1984-06-01

    Calculation of the neutron multiplication factor at delayed criticality may be necessary for benchmarking calculations but it may not be sufficient. The use of subcritical experiments to benchmark criticality safety calculations could result in substantial savings in fuel material costs for experiments. In some cases subcritical configurations could be used to benchmark calculations where sufficient fuel to achieve delayed criticality is not available. By performing a variety of measurements with subcritical configurations, much detailed information can be obtained which can be compared directly with calculations. This paper discusses several measurements that can be performed with subcritical assemblies and presents examples that include comparisons between calculation and experiment where possible. Where not, examples from critical experiments have been used but the measurement methods could also be used for subcritical experiments.

  14. Subcritical and supercritical water oxidation of CELSS model wastes

    NASA Technical Reports Server (NTRS)

    Takahashi, Y.; Wydeven, T.; Koo, C.

    1989-01-01

    A mixture of ammonium hydroxide with acetic acid and a slurry of human feces, urine, and wipes were used as CELSS model wastes to be wet-oxidized at temperatures from 250 to 500 C, i.e. below and above the critical point of water (374 C and 218 kg/sq cm or 21.4 MPa). The effects of oxidation temperature ( 250-500 C) and residence time (0-120 mn) on carbon and nitrogen and on metal corrosion from the reactor material were studied. Almost all of the organic matter in the model wastes was oxidized in the temperature range from 400 to 500 C, above the critical conditions for water. In contrast, only a small portion of the organic matter was oxidized at subcritical conditions. A substantial amount of nitrogen remained in solution in the form of ammonia at temperatures ranging from 350 to 450 C suggesting that, around 400 C, organic carbon is completely oxidized and most of the nitrogen is retained in solution. The Hastelloy C-276 alloy reactor corroded during subcritical and supercritical water oxidation.

  15. Subcritical and supercritical water oxidation of CELSS model wastes

    NASA Technical Reports Server (NTRS)

    Takahashi, Y.; Wydeven, T.; Koo, C.

    1989-01-01

    A mixture of ammonium hydroxide with acetic acid and a slurry of human feces, urine, and wipes were used as CELSS model wastes to be wet-oxidized at temperatures from 250 to 500 C, i.e. below and above the critical point of water (374 C and 218 kg/sq cm or 21.4 MPa). The effects of oxidation temperature ( 250-500 C) and residence time (0-120 mn) on carbon and nitrogen and on metal corrosion from the reactor material were studied. Almost all of the organic matter in the model wastes was oxidized in the temperature range from 400 to 500 C, above the critical conditions for water. In contrast, only a small portion of the organic matter was oxidized at subcritical conditions. A substantial amount of nitrogen remained in solution in the form of ammonia at temperatures ranging from 350 to 450 C suggesting that, around 400 C, organic carbon is completely oxidized and most of the nitrogen is retained in solution. The Hastelloy C-276 alloy reactor corroded during subcritical and supercritical water oxidation.

  16. Monitoring of MNSR operation by measuring subcritical photoneutron flux.

    PubMed

    Haddad, Kh; Alsomel, N

    2011-03-01

    Passive nondestructive assay methods are used to monitor the reactor's operation. It is required for nuclear regulatory, calculation validation and safeguards purposes. So, it plays a vital role in the safety and security of the nuclear plants. The possibility of MNSR operation monitoring by measuring the subcritical state photoneutron flux were investigated in this work. The photoneutron flux is induced by the fuels hard gamma radiation in the beryllium reflector. Theoretical formulation and experimental tests were performed. The results show that within a specified cooling time range, the photoneutron flux is induced by a single dominant hard gamma emitter such as (117)Cd (activation product) and (140)Ba ((140)La fission product). This phenomenon was utilized to monitor the cooling time and the operation neutron flux during the last campaign. Thus a passive nondestructive assay method is proposed with regard to the reactor operation's monitoring. Copyright © 2010 Elsevier Ltd. All rights reserved.

  17. Reactor

    DOEpatents

    Evans, Robert M.

    1976-10-05

    1. A neutronic reactor having a moderator, coolant tubes traversing the moderator from an inlet end to an outlet end, bodies of material fissionable by neutrons of thermal energy disposed within the coolant tubes, and means for circulating water through said coolant tubes characterized by the improved construction wherein the coolant tubes are constructed of aluminum having an outer diameter of 1.729 inches and a wall thickness of 0.059 inch, and the means for circulating a liquid coolant through the tubes includes a source of water at a pressure of approximately 350 pounds per square inch connected to the inlet end of the tubes, and said construction including a pressure reducing orifice disposed at the inlet ends of the tubes reducing the pressure of the water by approximately 150 pounds per square inch.

  18. Measuring alpha eigenvalue of a subcritical system by a intense pulsed neutron source

    SciTech Connect

    Hu, Meng-chun; Gong, Jian; Peng, Tai-ping; Li, Zhong-bao; Zhang, Jian-hua; Tang, Deng-pan; Bai, Yun; Peng, Xian-jue; Zeng, Qing

    2015-07-01

    Intense-Pulsed-Neutron-Source (IPNS) technique is a new approach to measure the subcriticality of a reactor system, which has been theoretically analyzed by us while not been verified in experiment in other reference. In INPS technique the reactivity is derived via the system response to a prompt pulsed neutron source. The method utilizes very intense neutron pulses (about 1010 neutrons/pulse) with the duration ranging from 10 ns to 100 ns, which are generated by the dense plasma focus (DPF) device filled with pure DT mixture as the working gas. The neutron pulse in high intensity provides the opportunity to measure the signal using a scintillator and a photo-multiplier tube (PMT) (the intense pulse radiation measure method) with the flight distance of only twenty centimeters. The attenuation of the dense plasma focus device must be faster than the subcritical system so that the attenuation of the system can be researched. In this paper, after a neutron pulse is injected into the subcritical reactor, the subcriticality is determined by measuring the instantaneous characteristics of the leaking reactor neutron. The Monte Carlo analysis shows that, with the linear arrangement of the dense plasma focus, the subcritical system and the detector, the signal-to-noise ratio at the measure point meets the investigate requirement, in which the 14 MeV neutrons are attenuated by the subcritical system. The detector is close with the subcritical system to reduce the influence of the outer background and the spread of time-of-flight of the neutrons. The measure system utilizing gated detection technology is characterized with fast attenuation time and large linear current, the a value obtained with this method is 2.05 μs{sup -1} while the measurements using the {sup 252}Cf stochastic pulsed source method and the Rossi-a method were 2.18μs{sup -1} and 2.16μs{sup -1}.It showed that the measured result obtained with dense plasma focus instantaneous pulsed source is consistent

  19. Monte Carlo modeling and analyses of YALINA booster subcritical assembly, Part III : low enriched uranium conversion analyses.

    SciTech Connect

    Talamo, A.; Gohar, Y.

    2011-05-12

    This study investigates the performance of the YALINA Booster subcritical assembly, located in Belarus, during operation with high (90%), medium (36%), and low (21%) enriched uranium fuels in the assembly's fast zone. The YALINA Booster is a zero-power, subcritical assembly driven by a conventional neutron generator. It was constructed for the purpose of investigating the static and dynamic neutronics properties of accelerator driven subcritical systems, and to serve as a fast neutron source for investigating the properties of nuclear reactions, in particular transmutation reactions involving minor-actinides. The first part of this study analyzes the assembly's performance with several fuel types. The MCNPX and MONK Monte Carlo codes were used to determine effective and source neutron multiplication factors, effective delayed neutron fraction, prompt neutron lifetime, neutron flux profiles and spectra, and neutron reaction rates produced from the use of three neutron sources: californium, deuterium-deuterium, and deuterium-tritium. In the latter two cases, the external neutron source operates in pulsed mode. The results discussed in the first part of this report show that the use of low enriched fuel in the fast zone of the assembly diminishes neutron multiplication. Therefore, the discussion in the second part of the report focuses on finding alternative fuel loading configurations that enhance neutron multiplication while using low enriched uranium fuel. It was found that arranging the interface absorber between the fast and the thermal zones in a circular rather than a square array is an effective method of operating the YALINA Booster subcritical assembly without downgrading neutron multiplication relative to the original value obtained with the use of the high enriched uranium fuels in the fast zone.

  20. ENHANCED ELECTROCHEMICAL PROCESSES IN SUBCRITICAL WATER

    SciTech Connect

    Steven B. Hawthorne

    2000-07-01

    This project involved designing and performing preliminary electrochemical experiments in subcritical water. An electrochemical cell with substantially better performance characteristics than presently available was designed, built, and tested successfully. The electrochemical conductivity of subcritical water increased substantially with temperature, e.g., conductivities increased by a factor of 120 when the temperature was increased from 25 to 250 C. Cyclic voltammograms obtained with platinum and nickel demonstrated that the voltage required to produce hydrogen and oxygen from water can be dropped by a factor of three in subcritical water compared to the voltages required at ambient temperatures. However, no enhancement in the degradation of 1,2-dichlorobenzene and the polychlorinated biphenyl 3,3',4,4'-tetrachlorobiphenyl was observed with applied potential in subcritical water.

  1. Preliminary investigation of the /sup 252/Cf-source-driven noise analysis method of subcriticality measurement in LWR fuel storage and initial loading applications

    SciTech Connect

    King, W.T.; Mihalczo, J.T.; Blakeman, E.D.

    1984-01-01

    The ability of the /sup 252/Cf-source-driven neutron noise analysis method to measure subcriticality has been demonstrated in a variety of experimental configurations of fissile materials. Calculations for an approximately 4-m-dia configuration of light water reactor (LWR) fuel elements indicated the feasibility of measuring the subcriticality of large, loosely coupled arrays of LWR fuel elements by this same method. These analysis suggested application to the initial loading of both pressurized and boiling water reactors, zero-power testing of reactors (such as shutdown margin measurements after initial loading), light water reactor refueling, and safe storage of LWR spent fuel. In the fuel storage application, direct measurement of subcriticality in the actual fuel storage facilities provides the parameter which is directly related to criticality safety.

  2. REACTOR CONTROL DEVICE

    DOEpatents

    Graham, R.H.

    1962-09-01

    A wholly mechanical compact control device is designed for automatically rendering the core of a fission reactor subcritical in response to core temperatures in excess of the design operating temperature limit. The control device comprises an expansible bellows interposed between the base of a channel in a reactor core and the inner end of a fuel cylinder therein which is normally resiliently urged inwardly. The bellows contains a working fluid which undergoes a liquid to vapor phase change at a temperature substantially equal to the design temperature limit. Hence, the bellows abruptiy expands at this limiting temperature to force the fuel cylinder outward and render the core subcritical. The control device is particularly applicable to aircraft propulsion reactor service. (AEC)

  3. Compact Torus Accelerator Driven Inertial Confinement Fusion Power Plant HYLIFE-CT

    SciTech Connect

    Logan, B G; Moir, R W; Tabak, M; Bieri, R L; Hammer, J H; Hartman, C W; Hoffman, M A; Leber, R L; Petzoldt, R W; Tobin, M T

    2005-03-30

    A Compact Torus Accelerator (CTA) is used to accelerate a Compact Torus (CT) to 35 MJ kinetic energy which is focused to a 20 mm diameter where its kinetic energy is converted to a shaped x-ray pulse of 30 MJ. The capsule yield with a prescribed radiation profile is calculated to be (gain 60 times 30 MJ) 1.8 GJ. Schemes for achieving this profile are described. The CT is accelerated in a length of 30 m within an annulus of 150 mm ID and 300 mm OD where the maximum magnetic field is 28 T. A 2.5 m conical taper reduces the mean diameter of the CT from 225 mm to 20 mm. The conical section is made out of solid Li{sub 2}BeF{sub 4}. The target with its frozen conical guide section is accurately placed at the end of the accelerator about once per second. The reactor called HYLIFE uses liquid jets to attenuate blast effects including shrapnel from the shattered conical guide section and radiation so that the vessel is expected to last 30 years. The calculated cost of electricity is estimated (in constant 1988 dollars) to be about 4.8 cents/kW {center_dot} h compared to the future cost of nuclear and coal of 4.3 to 5.8 cents/kW {center_dot} h. The CT driver contributes 17% to the cost of electricity. Present CT's make 2 x 10{sup 8} W/cm{sup 2}; the goal of experiments in progress is 10{sup 11} W/cm{sup 2} with further modifications to allow 10{sup 12}W/cm{sup 2}, whereas the reactor requires 10{sup 15} W/cm{sup 2} in a shaped pulse.

  4. Degradation kinetics of passion fruit pectin in subcritical water.

    PubMed

    Klinchongkon, Khwanjai; Khuwijitjaru, Pramote; Adachi, Shuji

    2017-04-01

    The degradation of passion fruit pectin by subcritical water treatment in a continuous flow-type reactor was investigated in the temperature range of 80-160 °C at a constant pressure of 5 MPa. Changes in the degree of polymerization and reducing end formation were monitored and modeled by applying the Emsley equation and zeroth-order kinetics, respectively. The results showed that both the pectin degradation rate constant and the change in the amount of reducing end were enhanced by temperature, and that the temperature dependence of these parameters obeyed the Arrhenius relationship. The activation energies for pectin degradation and reducing end formation were 62.8 and 86.9 kJ/mol, respectively. The non-linear relationship between the ratio of broken galacturonic acid units to the total galacturonic acid units and the change in the amount of reducing end indicated that pectin cleavage became easier as hydrolysis progressed.

  5. Cygnus Performance in Subcritical Experiments

    SciTech Connect

    G. Corrow, M. Hansen, D. Henderson, S. Lutz, C. Mitton, et al.

    2008-02-01

    The Cygnus Dual Beam Radiographic Facility consists of two identical radiographic sources with the following specifications: 4-rad dose at 1 m, 1-mm spot size, 50-ns pulse length, 2.25-MeV endpoint energy. The facility is located in an underground tunnel complex at the Nevada Test Site. Here SubCritical Experiments (SCEs) are performed to study the dynamic properties of plutonium. The Cygnus sources were developed as a primary diagnostic for these tests. Since SCEs are single-shot, high-value events - reliability and reproducibility are key issues. Enhanced reliability involves minimization of failure modes through design, inspection, and testing. Many unique hardware and operational features were incorporated into Cygnus to insure reliability. Enhanced reproducibility involves normalization of shot-to-shot output also through design, inspection, and testing. The first SCE to utilize Cygnus, Armando, was executed on May 25, 2004. A year later, April - May 2005, calibrations using a plutonium step wedge were performed. The results from this series were used for more precise interpretation of the Armando data. In the period February - May 2007 Cygnus was fielded on Thermos, which is a series of small-sample plutonium shots using a one-dimensional geometry. Pulsed power research generally dictates frequent change in hardware configuration. Conversely, SCE applications have typically required constant machine settings. Therefore, while operating during the past four years we have accumulated a large database for evaluation of machine performance under highly consistent operating conditions. Through analysis of this database Cygnus reliability and reproducibility on Armando, Step Wedge, and Thermos is presented.

  6. AIP conference on accelerator driven transmutation technologies and applications, Las Vegas, Nevada, July 25-29, 1994

    SciTech Connect

    Schriber, S.O.; Arthur, E.; Rodriguez, A.A.

    1995-07-01

    This conference was the first to bring together US and foreign researchers to define Accelerator Driven Transmutation Technology (ADTT) concepts in several important national and international application areas - nuclear waste transmutation, minimizing of world plutonium inventories, and long-term energy production. The conference covered a number of diverse technological areas - accelerators, target/blankets, separations, materials - that make up ADTT systems. The meeting provided one of the first opportunities for specialists in these technologies to meet together and learn about system requirements, components, and interface issues. It was also an opportunity to formulate plans for future developments in ADTT. During the conference over one hundred technical presentations were made describing ADTT system and technology concepts as well as the impact of ADTT on issues related to global plutonium management and the high-level nuclear waste problem areas. Separate abstracts have been entered into the database for articles from this report.

  7. Utilisation of British University Research Reactors.

    ERIC Educational Resources Information Center

    Duncton, P. J.; And Others

    British experience relating to the employment of university research reactors and subcritical assemblies in the education of nuclear scientists and technologists, in the training of reactor operators and for fundamental pure and applied research in this field is reviewed. The facilities available in a number of British universities and the uses…

  8. Utilisation of British University Research Reactors.

    ERIC Educational Resources Information Center

    Duncton, P. J.; And Others

    British experience relating to the employment of university research reactors and subcritical assemblies in the education of nuclear scientists and technologists, in the training of reactor operators and for fundamental pure and applied research in this field is reviewed. The facilities available in a number of British universities and the uses…

  9. Effects of Pb and Bi cross sections on ATW subcriticality predictions.

    SciTech Connect

    Khalil, H. S.; Yang, W. S.

    1999-06-25

    The accelerator-driven transmutation of waste (ATW) system has been proposed for transmuting the long-lived radioactive nuclei of high-level waste to stable or short-lived species. In recent ATW design concepts, lead-bismuth eutectic (LBE), consisting of 44.5% Pb and 55.5% Bi by weight is used as the spallation target, system coolant, and reflector. Because of the excellent neutron reflection properties of LBE, the subcriticality level of ATW is quite sensitive to the cross sections of lead and bismuth. The purpose of this paper is to investigate the effects of these cross sections on subcriticality and other core characteristics of ATW and to compare the results obtained using cross sections in different evaluated nuclear data files. The effects of lead and bismuth cross sections on the core characteristics of ATW were studied using 33 group cross section sets derived from the ENDF/B-VI, ENDF/B-V, JENDL-3.2, and BROND-2.2 nuclear data. A 2000 MW(thermal) ATW configuration similar to that described in Reference 1 was used in this study. In this configuration, the spallation target region is 55 cm high and 25 cm in radius, and is surrounded by a 15-cm thick LBE buffer. The adjacent fueled region is {approximately}65 cm thick and 200 cm high. The volume fractions of fuel, coolant, and structure are 25.7%, 59.3%, and 15%, respectively. The metal alloy fuel is composed of roughly 70% zirconium, 25% transuranics (TRU), and 5% Tc-99 by weight. A thick LBE reflector surrounds the whole core; its axial thickness is 250 cm, and its radial thickness is 295.2 cm.

  10. Selection of flowing liquid lead target structural materials for accelerator driven transmutation applications

    NASA Astrophysics Data System (ADS)

    Park, John J.; Buksa, John J.

    1995-09-01

    The beam entry window and container for a liquid lead spallation target will be exposed to high fluxes of protons and neutrons that are both higher in magnitude and energy than have been experienced in proton accelerators and fission reactors, as well as in a corrosive environment. The structural material of the target should have a good compatibility with liquid lead, a sufficient mechanical strength at elevated temperatures, a good performance under an intense irradiation environment, and a low neutron absorption cross section; these factors have been used to rank the applicability of a wide range of materials for structural containment. Nb-1Zr has been selected for use as the structural container for the LANL ABC/ATW molten lead target. Corrosion and mass transfer behavior for various candidate structural materials in liquid lead are reviewed, together with the beneficial effects of inhibitors and various coatings to protect substrate against liquid lead corrosion. Mechanical properties of some candidate materials at elevated temperatures and the property changes resulting from 800 MeV proton irradiation are also reviewed.

  11. Selection of flowing liquid lead target structural materials for accelerator driven transmutation applications

    SciTech Connect

    Park, J.J.; Buksa, J.J.

    1994-08-01

    The beam entry window and container for a liquid lead spallation target will be exposed to high fluxes of protons and neutrons that are both higher in magnitude and energy than have been experienced in proton accelerators and fission reactors, as well as in a corrosive environment. The structural material of the target should have a good compatibility with liquid lead, a sufficient mechanical strength at elevated temperatures, a good performance under an intense irradiation environment, and a low neutron absorption cross section; these factors have been used to rank the applicability of a wide range of materials for structural containment Nb-1Zr has been selected for use as the structural container for the LANL ABC/ATW molten lead target. Corrosion and mass transfer behavior for various candidate structural materials in liquid lead are reviewed, together with the beneficial effects of inhibitors and various coatings to protect substrate against liquid lead corrosion. Mechanical properties of some candidate materials at elevated temperatures and the property changes resulting from 800 MeV proton irradiation are also reviewed.

  12. K/sub infinity/-meter concept verified via subcritical-critical TRIGA experiments

    SciTech Connect

    Ocampo Mansilla, H.

    1983-01-01

    This work presents a technique for building a device to measure the k/sub infinity/ of a spent nuclear fuel assembly discharged from the core of a nuclear power plant. The device, called a k/sub infinity/-meter, consists of a cross-shaped subcritical assembly, two artificial neutron sources, and two separate neutron counting systems. The central position of the subcritical assembly is used to measure k/sub infinity/ of the spent fuel assembly. The initial subcritical assembly is calibrated to determine its k/sub eff/ and verify the assigned k/sub infinity/ of a selected fuel assembly placed in the central position. Count rates are taken with the fuel assembly of known k/sub infinity/'s placed in the central position and then repeated with a fuel assembly of unknown k/sub infinity/ placed in the central position. The count rate ratio of the unknown fuel assembly to the known fuel assembly is used to determine the k/sub infinity/ of the unknown fuel assembly. The k/sub infinity/ of the unknown fuel assembly is represented as a polynomial function of the count rate ratios. The coefficients of the polynomial equation are determined using the neutronic codes LEOPARD and EXTERMINATOR-II. The analytical approach has been validated by performing several subcritical/critical experiments, using the Penn State Breazeale TRIGA Reactor (PSBR), and comparing the experimental results with the calculations.

  13. Criticality Safety Evaluation of the LLNL Inherently Safe Subcritical Assembly (ISSA)

    SciTech Connect

    Percher, Catherine

    2012-06-19

    The LLNL Nuclear Criticality Safety Division has developed a training center to illustrate criticality safety and reactor physics concepts through hands-on experimental training. The experimental assembly, the Inherently Safe Subcritical Assembly (ISSA), uses surplus highly enriched research reactor fuel configured in a water tank. The training activities will be conducted by LLNL following the requirements of an Integration Work Sheet (IWS) and associated Safety Plan. Students will be allowed to handle the fissile material under the supervision of LLNL instructors. This report provides the technical criticality safety basis for instructional operations with the ISSA experimental assembly.

  14. SUB-LEU-METAL-THERM-001 SUBCRITICAL MEASUREMENTS OF LOW ENRICHED TUBULAR URANIUM METAL FUEL ELEMENTS BEFORE & AFTER IRRADIATION

    SciTech Connect

    SCHWINKENDORF, K.N.

    2006-05-12

    With the shutdown of the Hanford PUREX (Plutonium-Uranium Extraction Plant) reprocessing plant in the 1970s, adequate storage capacity for spent Hanford N Reactor fuel elements in the K and N Reactor pools became a concern. To maximize space utilization in the pools, accounting for fuel burnup was considered. Calculations indicated that at typical fuel exposures for N Reactor, the spent-fuel critical mass would be twice the critical mass for green fuel. A decision was reached to test the calculational result with a definitive experiment. If the results proved positive, storage capacity could be increased and N Reactor operation could be prolonged. An experiment to be conducted in the N Reactor spent-fuel storage pool was designed and assembled and the services of the Battelle Northwest Laboratories (BNWL) (now Pacific Northwest National Laboratory [PNNL]) critical mass laboratory were procured for the measurements. The experiments were performed in April 1975 in the Hanford N Reactor fuel storage pool. The fuel elements were MKIA fuel assemblies, comprising two concentric tubes of low-enriched metallic uranium. Two separate sets of measurements were performed: one with ''green'' (fresh) fuel and one with spent fuel. Both the green and spent fuel, were measured in the same geometry. The spent-fuel MKIA assemblies had an average burnup of 2865 MWd (megawatt days)/t. A constraint was imposed restricting the measurements to a subcritical limit of k{sub eff} = 0.97. Subcritical count rate data was obtained with pulsed-neutron and approach-to-critical measurements. Ten (10) configurations with green fuel and nine (9) configurations with spent fuel are described and evaluated. Of these, 3 green fuel and 4 spent fuel loading configurations were considered to serve as benchmark models. However, shortcomings in experimental data failed to meet the high standards for a benchmark problem. Nevertheless, the data provided by these subcritical measurements can supply useful

  15. Subcritical convection in an internally heated layer

    NASA Astrophysics Data System (ADS)

    Xiang, Linyan; Zikanov, Oleg

    2017-06-01

    Thermal convection in a horizontal layer with uniform internal heating and stress-free constant-temperature boundaries is analyzed numerically. The work is motivated by the questions arising in the development of liquid metal batteries, in which convection is induced by the Joule heating of electrolyte. It is demonstrated that three-dimensional convection cells exist at subcritical Rayleigh numbers.

  16. Comparison of Processes of Transmutation of Long-Lived Actinides in Different Reactors

    SciTech Connect

    Bergelson, B.R.; Gerasimov, A.S.; Kiselev, G.V.; Tikhomirov, G.V.

    2002-07-01

    Efficiency of transmutation of actinides was compared for different types of reactors-transmuters: light water VVER-1000 type reactor, fast breeder BN-600 and Super-Phenix type reactors, as well as high-flux subcritical ADS-800 type facility. Feed with minor actinides extracted from the reactor of VVER-1000 type was supposed. (authors)

  17. Sub-critical water hydrolysis of hog hair for amino acid production.

    PubMed

    Esteban, M B; García, A J; Ramos, P; Márquez, M C

    2010-04-01

    A recycling method using sub-critical water hydrolysis to convert hog hair from slaughterhouses into amino acids was developed. The influence of the reaction parameters such as temperature, time of reaction and initial substrate concentration were investigated in a batch reactor. The quality and quantity of amino acids in hydrolysates were determined and 17 kinds of amino acids were obtained. Under the tested conditions, the highest amino acid yield (325 mg/g protein) was reached at an initial substrate concentration of 10 g/l, a temperature of 250 degrees C and a reaction time of 60 min. A large amount of low-molecular weight amino acids, such alanine and glycine, was observed at these operating conditions. Sub-critical water hydrolysis was confirmed as an effective and practical process to recover amino acids from hog hair waste.

  18. Neutron field of accelerator-driven p(35 MeV)+Be fast neutron source at NPI Rez

    NASA Astrophysics Data System (ADS)

    Stefanik, Milan; Bem, Pavel; Majerle, Mitja; Novak, Jan; Simeckova, Eva

    2017-09-01

    The accelerator driven fast neutron sources of the white- and quasi-monoenergetic spectra are operated at the NPI Rez Fast Neutron Facility utilizing the Be(thick), D2O(thick), and 7Li(C) target stations and the variable energy proton beam (up to 37 MeV) from the U-120M isochronous cyclotron. Recently, the design of beryllium target station was upgraded in order to provide the higher neutron flux at the modified positions of irradiated samples. Afterwards, the thick target neutron field of the p+Be source reaction was investigated for proton energy of 35 MeV. The spectral neutron flux for several target-to-sample distances was determined using the multi-foil activation technique. From measured reaction rates, new neutron spectra were reconstructed employing the SAND-II unfolding code and validated against the MCNPX predictions. The IFMIF-like (International Fusion Material Irradiation Facility) neutron field obtained from the p(35)+Be source is suitable for the neutron cross-sections validation within the IFMIF research program, radiation hardness tests of electronics, and neutron activation analysis experiments.

  19. Mechanical Design and Analysis of a 200 MHz, Bolt-together RFQ forthe Accelerator Driven Neutron Source

    SciTech Connect

    Virostek, Steve; Hoff, Matt; Li, Derun; Staples, John; Wells,Russell

    2007-06-20

    A high-yield neutron source to screen sea-land cargocontainers for shielded Special Nuclear Materials (SNM) has been designedat LBNL [1,2]. The Accelerator-Driven Neutron Source (ADNS) uses theD(d,n)3He reaction to create a forward directed neutron beam. Keycomponents are a high-current radio-frequency quadrupole (RFQ)accelerator and a high-power target capable of producing a neutron fluxof>107 n/(cm2 cdot s) at a distance of 2.5 m. The mechanical designand analysis of the four-module, bolt-together RFQ will be presentedhere. Operating at 200 MHz, the 5.1 m long RFQ will accelerate a 40 mAdeuteron beam to 6 MeV. At a 5 percent duty factor, the time-average d+beam current on target is 1.5 mA. Each of the 1.27 m long RFQ moduleswill consist of four solid OFHC copper vanes. A specially designed 3-DO-ring will provide vacuum sealing between both the vanes and themodules. RF connections are made with canted coil spring contacts. Aseries of 60 water-cooled pi-mode rods provides quadrupole modestabilization. A set of 80 evenly spaced fixed slug tuners is used forfinal frequency adjustment and local field perturbationcorrection.

  20. Proliferation Potential of Accelerator-Drive Systems: Feasibility Calculations

    SciTech Connect

    Riendeau, C.D.; Moses, D.L.; Olson, A.P.

    1998-11-01

    Accelerator-driven systems for fissile materials production have been proposed and studied since the early 1950s. Recent advances in beam power levels for small accelerators have raised the possibility that such use could be feasible for a potential proliferator. The objective of this study is to review the state of technology development for accelerator-driven spallation neutron sources and subcritical reactors. Energy and power requirements were calculated for a proton accelerator-driven neutron spallation source and subcritical reactors to produce a significant amount of fissile material--plutonium.

  1. Monte Carlo modeling and analyses of YALINA-booster subcritical assembly part 1: analytical models and main neutronics parameters.

    SciTech Connect

    Talamo, A.; Gohar, M. Y. A.; Nuclear Engineering Division

    2008-09-11

    This study was carried out to model and analyze the YALINA-Booster facility, of the Joint Institute for Power and Nuclear Research of Belarus, with the long term objective of advancing the utilization of accelerator driven systems for the incineration of nuclear waste. The YALINA-Booster facility is a subcritical assembly, driven by an external neutron source, which has been constructed to study the neutron physics and to develop and refine methodologies to control the operation of accelerator driven systems. The external neutron source consists of Californium-252 spontaneous fission neutrons, 2.45 MeV neutrons from Deuterium-Deuterium reactions, or 14.1 MeV neutrons from Deuterium-Tritium reactions. In the latter two cases a deuteron beam is used to generate the neutrons. This study is a part of the collaborative activity between Argonne National Laboratory (ANL) of USA and the Joint Institute for Power and Nuclear Research of Belarus. In addition, the International Atomic Energy Agency (IAEA) has a coordinated research project benchmarking and comparing the results of different numerical codes with the experimental data available from the YALINA-Booster facility and ANL has a leading role coordinating the IAEA activity. The YALINA-Booster facility has been modeled according to the benchmark specifications defined for the IAEA activity without any geometrical homogenization using the Monte Carlo codes MONK and MCNP/MCNPX/MCB. The MONK model perfectly matches the MCNP one. The computational analyses have been extended through the MCB code, which is an extension of the MCNP code with burnup capability because of its additional feature for analyzing source driven multiplying assemblies. The main neutronics parameters of the YALINA-Booster facility were calculated using these computer codes with different nuclear data libraries based on ENDF/B-VI-0, -6, JEF-2.2, and JEF-3.1.

  2. Subcritical string and large N QCD

    SciTech Connect

    Thorn, Charles B.

    2008-10-15

    We pursue the possibility of using subcritical string theory in 4 spacetime dimensions to establish a string dual for large N QCD. In particular we study the even G-parity sector of the 4 dimensional Neveu-Schwarz dual resonance model as the natural candidate for this string theory. Our point of view is that the open string dynamics given by this model will determine the appropriate subcritical closed string theory, a tree level background of which should describe the sum of planar multiloop open string diagrams. We examine the one-loop open string diagram, which contains information about the closed string spectrum at weak coupling. Higher loop open string diagrams will be needed to determine closed string interactions. We also analyze the field theory limit of the one-loop open string diagram and recover the correct running coupling behavior of the limiting gauge theory.

  3. From reactors to long pulse sources

    SciTech Connect

    Mezei, F. |

    1995-12-31

    We will show, that by using an adapted instrumentation concept, the performance of a continuous source can be emulated by one switch on in long pulses for only about 10% of the total time. This 10 fold gain in neutron economy opens up the way for building reactor like sources with an order of magnitude higher flux than the present technological limits. Linac accelerator driven spallation lends itself favorably for the realization of this kind of long pulse sources, which will be complementary to short pulse spallation sources, the same way continuous reactor sources are.

  4. Accelerator driven assembly

    SciTech Connect

    Balderas, J.; Cappiello, M.; Cummings, C.E.; Davidson, R.

    1997-01-01

    This report addresses a Los Alamos National Laboratory (LANL) proposal to build a pulsed neutron source for simulating nuclear-weapons effects. A point design for the pulsed neutron facility was initiated early in FY94 after hosting a Defense Nuclear Agency (DNA) panel review and after subsequently visiting several potential clients and users. The technical and facility designs contained herein fulfill the Statement of Work (SOW) agreed upon by LANL and DNA. However, our point designs and parametric studies identify a unique, cost-effective, above-ground capability for neutron nuclear-weapons-effects studies at threat levels. This capability builds on existing capital installations and infrastructure at LANL. We believe that it is appropriate for us, together with the DNA, to return to the user community and ask for their comments and critiques. We also realize that the requirements of last year have changed significantly. Therefore, the present report is a `working document` that may be revised where feasible as we learn more about the most recent Department of Defense (DoD) and Department of Energy (DOE) needs.

  5. Characteristics of membrane fouling in submerged membrane bioreactor under sub-critical flux operation.

    PubMed

    Su, Y C; Huang, C P; Pan, Jill R; Lee, H C

    2008-01-01

    Recently, the membrane bioreactor (MBR) process has become one of the novel technologies to enhance the performance of biological treatment of wastewater. Membrane bioreactor process uses the membrane unit to replace a sediment tank, and this can greatly enhance treatment performance. However, membrane fouling in MBR restricts its widespread application because it leads to permeate flux decline, making more frequent membrane cleaning and replacement necessary, which then increases operating and maintenance costs. This study investigated the sludge characteristics in membrane fouling under sub-critical flux operation and also assessed the effect of shear stress on membrane fouling. Membrane fouling was slow under sub-critical flux operation. However, as filamentous microbes became dominant in the reactor, membrane fouling increased dramatically due to the increased viscosity and polysaccharides. A close link was found between membrane fouling and the amount of polysaccharides in soluble EPS. The predominant resistance was the cake resistance which could be minimized by increasing the shear stress. However, the resistance of colloids and solutes was not apparently reduced by increasing shear stress. Therefore, smaller particles such as macromolecules (e.g. polysaccharides) may play an important role in membrane fouling under sub-critical flux operation.

  6. Kinetics and mechanism of the synthesis of a novel protein-based plastic using subcritical water.

    PubMed

    Abdelmoez, Wael; Yoshida, Hiroyuki

    2008-01-01

    We investigated the intermolecular mechanism and kinetics of the synthesis of a novel biodegradable protein-based plastic from bovine serum albumin under subcritical water conditions using batch reactors. The reaction mechanism could be viewed as a chain reaction stabilized by the formation of intermolecular disulfide bonds. The kinetic analysis was based on non-steady-state kinetics using a theoretical model developed in one of our previous works. The activation energy and pre-exponential factor were found to be 7.2 kJ/mol and 0.9 s-1, respectively. These low values signify that the reaction is relatively temperature-insensitive with some diffusion limitation.

  7. Subcritical neutron generator-test facility for nuclear waste transmutation studies

    SciTech Connect

    Chuvilo, I.V.; Kolomiets, A.A.; Kozodaev, A.M.

    1995-10-01

    The development of the optimal design of high power facility for NPP transmutation and for a number of applications can not be carried out without preliminary tests of much cheaper prototypes. It has been proposed to combine in new test facility 36 MeV Linac ISTRA constructed in ITEP, original Be target and subcritical blanket that will be mounted on the place of partly disassembled heavy water ITEP experimental reactor. The basic parameters of Linac, schemes of the target and blanket are described. It will provide the direct experiments on installation which can be considered as prototype for future linac driven high power facilities.

  8. SABR fusion-fission hybrid transmutation reactor design concept

    NASA Astrophysics Data System (ADS)

    Stacey, Weston

    2009-11-01

    A conceptual design has been developed for a sub-critical advanced burner reactor (SABR) consisting of i) a sodium cooled fast reactor fueled with the transuranics (TRU) from spent nuclear fuel, and ii) a D-T tokamak fusion neutron source based on ITER physics and technology. Subcritical operation enables more efficient transmutation fuel cycles in TRU fueled reactors (without compromising safety), which may be essential for significant reduction in high-level waste repository requirements. ITER will serve as the prototype for the fusion neutron source, which means SABRs could be implemented to help close the nuclear fuel cycle during the 2^nd quarter of the century.

  9. Co-liquefaction of micro- and macroalgae in subcritical water.

    PubMed

    Jin, Binbin; Duan, Peigao; Xu, Yuping; Wang, Feng; Fan, Yunchang

    2013-12-01

    Co-liquefaction of microalgae (Spirulina platensis, SP) and macroalgae (Entermorpha prolifera, EP) was studied in subcritical water by using a stainless-steel batch reactor at different temperature (250 to 370°C), time (5 to 120 min), SP/EP mass ratio (0 to 100%), and water/algae mass ratio (1:1 to 6:1). The results suggested that a positive synergetic effect existed during the co-liquefaction of SP and EP, and this synergetic effect was dependent on reaction conditions. Co-liquefaction alleviated the severe reaction conditions compared to the separate liquefaction of SP and EP and also promoted the in situ deoxygenation of the bio-oil. The higher-heating-value of bio-oil produced from the co-liquefaction of SP and EP (wSP:wEP=1) is 35.3 MJ/kg. The energy recovery from the co-liquefaction is larger than the average value from the separate liquefaction of SP and EP. Co-liquefaction did not affect the molecular composition but affect the relative amount of each component in the bio-oil.

  10. A Methodology for the Neutronics Design of Space Nuclear Reactors

    SciTech Connect

    King, Jeffrey C.; El-Genk, Mohamed S.

    2004-02-04

    A methodology for the neutronics design of space power reactors is presented. This methodology involves balancing the competing requirements of having sufficient excess reactivity for the desired lifetime, keeping the reactor subcritical at launch and during submersion accidents, and providing sufficient control over the lifetime of the reactor. These requirements are addressed by three reactivity values for a given reactor design: the excess reactivity at beginning of mission, the negative reactivity at shutdown, and the negative reactivity margin in submersion accidents. These reactivity values define the control worth and the safety worth in submersion accidents, used for evaluating the merit of a proposed reactor type and design. The Heat Pipe-Segmented Thermoelectric Module Converters space reactor core design is evaluated and modified based on the proposed methodology. The final reactor core design has sufficient excess reactivity for 10 years of nominal operation at 1.82 MW of fission power and is subcritical at launch and in all water submersion accidents.

  11. Upper Subcritical Calculations Based on Correlated Data

    SciTech Connect

    Sobes, Vladimir; Rearden, Bradley T; Mueller, Don; Marshall, William BJ J; Scaglione, John M; Dunn, Michael E

    2015-01-01

    The American National Standards Institute and American Nuclear Society standard for Validation of Neutron Transport Methods for Nuclear Criticality Safety Calculations defines the upper subcritical limit (USL) as “a limit on the calculated k-effective value established to ensure that conditions calculated to be subcritical will actually be subcritical.” Often, USL calculations are based on statistical techniques that infer information about a nuclear system of interest from a set of known/well-characterized similar systems. The work in this paper is part of an active area of research to investigate the way traditional trending analysis is used in the nuclear industry, and in particular, the research is assessing the impact of the underlying assumption that the experimental data being analyzed for USL calculations are statistically independent. In contrast, the multiple experiments typically used for USL calculations can be correlated because they are often performed at the same facilities using the same materials and measurement techniques. This paper addresses this issue by providing a set of statistical inference methods to calculate the bias and bias uncertainty based on the underlying assumption that the experimental data are correlated. Methods to quantify these correlations are the subject of a companion paper and will not be discussed here. The newly proposed USL methodology is based on the assumption that the integral experiments selected for use in the establishment of the USL are sufficiently applicable and that experimental correlations are known. Under the assumption of uncorrelated data, the new methods collapse directly to familiar USL equations currently used. We will demonstrate our proposed methods on real data and compare them to calculations of currently used methods such as USLSTATS and NUREG/CR-6698. Lastly, we will also demonstrate the effect experiment correlations can have on USL calculations.

  12. Transient Thermo-Hydraulic Analysis of the Windowless Target System for the Lead Bismuth Eutectic Cooled Accelerator Driven System

    SciTech Connect

    Bianchi, Fosco; Ferri, Roberta; Moreau, Vincent

    2006-07-01

    The target system, whose function is to supply an external neutron source to the ADS sub-critical core to sustain the neutron chain reaction, is the most critical part of an ADS being subject to severe thermo-mechanical loading and material damage due to accelerator protons and fission neutrons. A windowless option was chosen as reference configuration for the target system of the LBE-cooled ADS within the European PDS-XADS project in order to reduce the material damage and to increase its life. This document deals with the thermo-hydraulic results of the calculations performed with STAR-CD and RELAP5 codes for studying the behaviour of the windowless target system during off-normal operating conditions. It also reports a description of modifications properly implemented in the codes needed for this analysis. The windowless target system shows a satisfactory thermo-hydraulic behaviour for the analysed accidents, except for the loss of both pumps without proton beam shut-off and the beam trips lasting more than one second. (authors)

  13. Subcritical water extraction of lipids from wet algal biomass

    DOEpatents

    Deng, Shuguang; Reddy, Harvind K.; Schaub, Tanner; Holguin, Francisco Omar

    2016-05-03

    Methods of lipid extraction from biomass, in particular wet algae, through conventionally heated subcritical water, and microwave-assisted subcritical water. In one embodiment, fatty acid methyl esters from solids in a polar phase are further extracted to increase biofuel production.

  14. Properties of rice stem extracts obtained by using subcritical fluids.

    PubMed

    Tangkhavanich, Boonnakhom; Kobayashi, Takashi; Adachi, Shuji

    2013-01-01

    Rice stems were subjected to a subcritical fluid treatment at 230 °C, using ethanol or acetone at a dilution of 0-100% in water. The obtained extracts were determined for their yield, carbohydrate content, phenolic content, DPPH radical scavenging ability, and color. The highest yield and carbohydrate content were achieved with the subcritical 20% (v/v) organic solvent, while the highest phenolic content was obtained with subcritical 80% (v/v) acetone. The highest radical scavenging ability was achieved with subcritical 60% (v/v) ethanol and 80% (v/v) acetone. The lightness of the extracts obtained with subcritical ethanol and acetone was negatively correlation with their radical scavenging ability (R=-0.85). The relationship between the lightness and phenolic content of the extracts was not significant, suggesting that other substances in the extract could also possess radical scavenging ability.

  15. Modeling new coal projects: supercritical or subcritical?

    SciTech Connect

    Carrino, A.J.; Jones, R.B.

    2006-11-15

    Decisions made on new build coal-fired plants are driven by several factors - emissions, fuel logistics and electric transmission access all provide constraints. The crucial economic decision whether to build supercritical or subcritical units often depends on assumptions concerning the reliability/availability of each technology, the cost of on-fuel operations including maintenance, the generation efficiencies and the potential for emissions credits at some future value. Modeling the influence of these key factors requires analysis and documentation to assure the assets actually meet the projected financial performance. This article addresses some of the issue related to the trade-offs that have the potential to be driven by the supercritical/subcritical decision. Solomon Associates has been collecting cost, generation and reliability data on coal-fired power generation assets for approximately 10 years using a strict methodology and taxonomy to categorize and compare actual plant operations data. This database provides validated information not only on performance, but also on alternative performance scenarios, which can provide useful insights in the pro forma financial analysis and models of new plants. 1 ref., 1 fig., 3 tabs.

  16. Off-line coupling of subcritical water extraction with subcritical water chromatography via a sorbent trap and thermal desorption.

    PubMed

    Lamm, Lori J; Yang, Yu

    2003-05-15

    In this study, the off-line coupling of subcritical water extraction (SBWE) with subcritical water chromatography (SBWC) was achieved using a sorbent trap and thermal desorption. The sorbent trap was employed to collect the extracted analytes during subcritical water extraction. After the extraction, the trap was connected to the subcritical water chromatography system, and thermal desorption of the trapped analytes was performed before the SBWC run. The thermally desorbed analytes were then introduced into the subcritical water separation column and detected by a UV detector. Anilines and phenols were extracted from sand and analyzed using this off-line coupling technique. Subcritical water extraction of flavones from orange peel followed by subcritical water chromatographic separation was also investigated. The effects of water volume and extraction temperature on flavone recovery were determined. Because a sorbent trap was used to collect the extracted analytes, the sensitivity of this technique was greatly enhanced as compared to that of subcritical water extraction with solvent trapping. Since no organic solvent-water extractions were necessary prior to analysis, this technique eliminated any use of organic solvents in both extraction and chromatography processes.

  17. Physics considerations involved in the use of insoluble poisons as an alternate means of ensuring subcriticality in the rotary fuel dissolver

    SciTech Connect

    Bucholz, J.A.

    1984-08-01

    While the use of soluble neutron poisons coupled with mass control is sufficient to guarantee subcriticality in the rotary fuel dissolver, an alternate means of ensuring subcriticality was also investigated from a reactor physics viewpoint. The scheme proposed in this report relies on the use of 0.25-in. diam stainless-steel-clad B/sub 4/C pellets which could be mixed uniformly with the sheared fuel from the Fast Flux Test Facility (FFTF) as it is being fed to the dissolver. The calculations described herein show that an infinite system of the type just described would be safely subcritical (k/sub infinity/ less than or equal to 0.95) at all H/Pu ratios as long as the relative volume of FFTF fuel in the dry system does not exceed 34%. The operational complexities and equipment modifications necessary to employ this method of criticality control have not been examined. 5 references, 6 figures, 8 tables.

  18. SUB-LEU-METAL-THERM-001 SUBCRITICAL MEASUREMENTS OF LOW ENRICHED TUBULAR URANIUM METAL FUEL ELEMENTS BEFORE & AFTER IRRADIATION

    SciTech Connect

    TOFFER, H.

    2006-07-18

    With the shutdown of the Hanford PUREX (Plutonium-Uranium Extraction Plant) reprocessing plant in the 1970s, adequate storage capacity for spent Hanford N Reactor fuel elements in the K and N Reactor pools became a concern. To maximize space utilization in the pools, accounting for fuel burnup was considered. Fuel that had experienced a neutron environment in a reactor is known as spent, exposed, or irradiated fuel. In contrast fuel that has not yet been placed in a reactor is known as green, unexposed, or unirradiated fuel. Calculations indicated that at typical fuel exposures for N Reactor, the spent-fuel critical mass would be twice the critical mass for green fuel. A decision was reached to test the calculational result with a definitive experiment. If the results proved positive, storage capacity could be increased and N Reactor operation could be prolonged. An experiment to be conducted in the N Reactor spent-fuel storage pool was designed and assembled (References 1 and 2) and the services of the Battelle Northwest Laboratories (BNWL) (now Pacific Northwest National Laboratory [PNNL]) critical mass laboratory were procured for the measurements (Reference 3). The experiments were performed in April 1975 in the Hanford N Reactor fuel storage pool. The fuel elements were MKIA fuel assemblies, comprised of two concentric tubes of low-enriched metallic uranium. Two separate sets of measurements were performed: one with unirradiated fuel and one with irradiated fuel. Both the unirradiated and irradiated fuel, were measured in the same geometry. The spent-fuel MKIA assemblies had an average burnup of 2865 MWd (megawatt days)/t. A constraint was imposed restricting the measurements to a subcritical limit of k{sub eff} = 0.97. Subcritical count rate data was obtained with pulsed-neutron and approach-to-critical measurements. Ten (10) configurations with green fuel and nine (9) configurations with spent fuel are described and evaluated. Of these, three (3) green fuel

  19. Review of High Temperature Water and Steam Cooled Reactor Concepts

    SciTech Connect

    Oka, Yoshiaki

    2002-07-01

    This review summarizes design concepts of supercritical-pressure water cooled reactors (SCR), nuclear superheaters and steam cooled fast reactors from 1950's to the present time. It includes water moderated supercritical steam cooled reactor, SCOTT-R and SC-PWR of Westinghouse, heavy water moderated light water cooled SCR of GE, SCLWR and SCFR of the University of Tokyo, B-500SKDI of Kurchatov Institute, CANDU -X of AECL, nuclear superheaters of GE, subcritical-pressure steam cooled FBR of KFK and B and W, Supercritical-pressure steam cooled FBR of B and W, subcritical-pressure steam cooled high converter by Edlund and Schultz and subcritical-pressure water-steam cooled FBR by Alekseev. This paper is prepared based on the previous review of SCR2000 symposium, and some author's comments are added. (author)

  20. Polychlorinated biphenyls degradation in subcritical water

    NASA Astrophysics Data System (ADS)

    Doctor, Ninad; Yang, Larry; Yang, Yu

    2017-08-01

    In this work, the degradation of PCB-118, PCB-156, and PCB-180 congeners under subcritical conditions has been investigated. Stainless reaction vessels were used to carry out the heating of reaction mixtures. Liquid-liquid extraction of the reaction mixtures was conducted prior to GC analysis. Approximately 30% PCBs were degraded by 30% hydrogen peroxide after 24 hours of reaction time but without heating the mixtures. The percent degradation of PCBs was however improved to approximately 60% after heating the mixtures at 300 °C for an hour. In general, the PCB degradation efficiency was enhanced by increasing the reaction temperature from 300 and 350 °C. The percent degradation of PCBs was mostly improved by increasing the heating time from 1 hour to 6 hours. In addition, increasing the percentage of hydrogen peroxide significantly increases the rate of PCB destruction.

  1. Microdeformation and subcritical cracking in chalk

    NASA Astrophysics Data System (ADS)

    Bergsaker, Anne; Dysthe, Dag Kristian

    2016-04-01

    Deformation processes in chalks, both in relation to changing pore fluids and stress conditions has been of great interest as chalk is an important reservoir rock for both hydrocarbons and ground water. Lately it has also gained interest as a potential reservoir rock for captured CO2. Chalks are composed of large amounts of biogenic calcite grains, the skeletal debris of marine microorganisms. Its deformation is highly time and stress dependent, and governed by a transition from distributed to localized deformation at the onset of yield, affected by mechanisms such as subcritical crack growth and pore collapse. We present a microdeformation rig which makes use of thermal expansion as a means of subjecting small samples to strictly controlled tensile stresses. High resolution imaging provides resolutions down to 0.5 micrometers, enabling study of pore scale processes during slow deformation. Examples of localized and distributed deformation are presented.

  2. Massive subcritical compact arrays of plutonium metal

    SciTech Connect

    Rothe, R.E.

    1998-04-01

    Two experimental critical-approach programs are reported. Both were performed at the Rocky Flats Plant near Denver, Colorado; and both date back to the late 1960s. Both involve very large arrays of massive plutonium ingots. These ingots had been cast in the foundry at the Rocky Flats Plant as part of their routine production operations; they were not specially prepared for either study. Consequently, considerable variation in ingot mass is encountered. This mass varied between approximately 7 kg and a little more than 10 kg. One program, performed in the spring of 1969, involved stacked arrays of ingots contained within cylindrical, disk-shaped, thin, steel cans. This program studied four arrays defined by the pattern of steel cans in a single layer. The four were: 1 x N, 3 x N, 2 x 2 x N, and 3 x 3 x N. The second was a tightly-packed, triangular-pitched patterns; the last two were square-pitched patterns. The other program, performed about a year earlier, involved similar ingots also contained in similar steel cans, but these canned plutonium ingots were placed in commercial steel drums. This study pertained to one-, two-, and three-layered horizontal arrays of drums. All cases proved to be well subcritical. Most would have remained subcritical had the parameters of the array under study been continued infinitely beyond the reciprocal multiplication safety limit. In one case for the drum arrays, an uncertain extrapolation of the data of the earlier program suggests that criticality might have eventually been attained had several thousand additional kilograms of plutonium been available for use.

  3. Carbon dioxide modified subcritical water chromatography.

    PubMed

    Fogwill, Michael O; Thurbide, Kevin B

    2008-07-18

    A novel method of increasing the elution strength in subcritical water chromatography (SWC) by adding CO2 to the water mobile phase is presented. Since the polarity of water reduces dramatically with increasing temperature, this property is used in SWC to create an isocratic mobile phase with tunable elutropic strength in reversed-phase separations. Unfortunately, thermal stability of the stationary phase dictates the upper temperature limit and therefore also the minimum available mobile phase polarity. As a result SWC is often not very effective at eluting non-polar analytes. However, when CO2 is blended into subcritical water, a considerable reduction in mobile phase polarity results and improves such separations. For example, in conventional SWC 1-octanol is not observed to elute from a PRP-1 column after several hours at the maximum column temperature of 200 degrees C. In contrast to this, when CO2 is present at 180atm (1atm=101325Pa) in the mobile phase, 1-octanol elutes with good peak shape in less than 4min at only 100 degrees C. The technique is applied to the separation of a variety of analytes which have previously been challenging or even not possible to analyze by conventional SWC. Further, the ability to use temperature and composition programming with the blended CO2/water mobile phase in SWC is also presented and discussed. Overall, the developed method considerably extends the range of non-polar analytes amenable to SWC analysis, while maintaining the beneficial conventional SWC features of flame ionization detection and environmental compatibility.

  4. Organic Sulfur and HAP Removal from Coal with Subcritical Water

    SciTech Connect

    1996-12-31

    To date, no economically feasible organic sulfur and hazardous air pollutant (HAP) precursor removal process has been developed; however, an effective sulfur and selected HAP removal process is needed to enhance the utilization of high-sulfur coals and to comply with increasingly stringent regulations. Subcritical water has been shown by the Energy & Environmental Research Center (EERC) researchers on this project to be an extremely effective fluid for the removal of organic sulfur from coals. A multigram reactor designed and built at the EERC for supercritical water extraction was used to scale up from milligram-sized samples to 10-20 grams of coal charge. Work performed during this project year resulted in production of low-sulfur (as low as 0.5% S) extracted coal first at supercritical conditions, i.e., 450{degrees}C and 400 atm (5880 psig), but then at conditions below the critical conditions, i.e., 420{degrees}C and 156 atm (2300 psig). Still milder conditions of 400{degrees}C and 156 atm (2300 psig) resulted in sulfur values similar to those of obtained under the supercritical conditions. IBC-102 extracted with supercritical water had a sulfur value of 0.7 wt%. Extraction of IBC-102 at subcritical conditions of 420{degrees}C and 156 atm (2300 psig) resulted in a sulfur content of 0.490A. The tar obtained from the extracted coal had sulfur values ranging from 1.4 to 6.5 wt% and when treated by catalytic desulfurization, tar was quantitatively recovered with a sulfur value of 0.6 wt%. Float-sink physical cleaning of IBC-102 with Certigrav 1.4 reduced the sulfur content of the coal to 1.5 wt% in a recovered float fraction of 83.3%. Approximately 300 lb of IBC-102 was obtained for use in preparing 100 lb of low-sulfur fuel. Float- sink cleaning on a sample of this new coal returned 87.1 wt% as float fraction, with 1.7 wt% sulfur. 158 lb of physically cleaned IBC-102 was used for the continuous process test on the pilot scale. An additional 150 lb of physically

  5. Astrobionibbler: In Situ Microfluidic Subcritical Water Extraction of Amino Acids

    NASA Astrophysics Data System (ADS)

    Noell, A. C.; Fisher, A. M.; Takano, N.; Fors-Francis, K.; Sherrit, S.; Grunthaner, F.

    2016-10-01

    A fluidic-chip based instrument for subcritical water extraction (SCWE) of amino acids and other organics from powder samples has been developed. A variety of soil analog extractions have been performed to better understand SCWE capabilities.

  6. Structural changes in microcrystalline cellulose in subcritical water treatment.

    PubMed

    Tolonen, Lasse K; Zuckerstätter, Gerhard; Penttilä, Paavo A; Milacher, Walter; Habicht, Wilhelm; Serimaa, Ritva; Kruse, Andrea; Sixta, Herbert

    2011-07-11

    Subcritical water is a high potential green chemical for the hydrolysis of cellulose. In this study microcrystalline cellulose was treated in subcritical water to study structural changes of the cellulose residues. The alterations in particle size and appearance were studied by scanning electron microscopy (SEM) and those in the degree of polymerization (DP) and molar mass distributions by gel permeation chromatography (GPC). Further, changes in crystallinity and crystallite dimensions were quantified by wide-angle X-ray scattering and (13)C solid-state NMR. The results showed that the crystallinity remained practically unchanged throughout the treatment, whereas the size of the remaining cellulose crystallites increased. Microcrystalline cellulose underwent significant depolymerization in subcritical water. However, depolymerization leveled off at a relatively high degree of polymerization. The molar mass distributions of the residues showed a bimodal form. We infer that cellulose gets dissolved in subcritical water only after extensive depolymerization.

  7. Feedback control of subcritical oscillatory instabilities.

    PubMed

    Golovin, A A; Nepomnyashchy, A A

    2006-04-01

    Feedback control of a subcritical oscillatory instability is investigated in the framework of a globally-controlled complex Ginzburg-Landau equation that describes the nonlinear dynamics near the instability threshold. The control is based on a feedback loop between the system linear growth rate and the maximum of the amplitude of the emerging pattern. It is shown that such control can suppress the blow up and result in the formation of spatially localized pulses similar to oscillons. In the one-dimensional case, depending on the values of the linear and nonlinear dispersion coefficients, several types of the pulse dynamics are possible in which the computational domain contains: (i) a single stationary pulse; (ii) several coexisting stationary pulses; (iii) competing pulses that appear one after another at random locations so that at each moment of time there is only one pulse in the domain; (iv) spatiotemporally chaotic system of short pulses; (v) spatially-synchronized pulses. Similar dynamic behavior is found also in the two-dimensional case. The effect of the feedback delay is also studied. It is shown that the increase of the delay leads to an oscillatory instability of the pulses and the formation of pulses with oscillating amplitude.

  8. Kinetic analysis for the isomerization of cellobiose to cellobiulose in subcritical aqueous ethanol.

    PubMed

    Soisangwan, Nontanut; Gao, Da-Ming; Kobayashi, Takashi; Khuwijitjaru, Pramote; Adachi, Shuji

    2016-10-04

    The isomerization of cellobiose to cellobiulose, and other degradation reactions of cellobiose were investigated in subcritical aqueous ethanol with concentrations of ethanol ranging from 0 to 60% (w/w) and at temperatures ranging from 170 to 200 °C. The maximum yield of cellobiulose (ca. 40%) was obtained from the treatment of cellobiose in 60% (w/w) aqueous ethanol at 190 °C. Glucose and fructose were also detected as byproducts. The concentration-time integral method was employed to analyze the rate constants for the isomerization and degradation processes. The rate constant of cellobiose isomerization to cellobiulose was greater than those of the degradation reactions under all experimental conditions, and it increased significantly with treatment temperature and ethanol concentration. However, the use of higher temperatures and ethanol concentrations was restricted due to decomposition of the saccharides and the low solubility of cellobiose, respectively. The effect of initial feed concentration (0.5-5.5% w/w) was also studied. The maximum productivity of cellobiulose, 54.1 kg/(h m(3)-reactor), was accomplished at a feed concentration of 5.5% (w/w) in 20% (w/w) subcritical aqueous ethanol.

  9. Subcritical measurements using the /sup 252/Cf source-driven neutron noise analysis method

    SciTech Connect

    Mihalczo, J.T.; Blakeman, E.D.; Ragan, G.E.; Kryter, R.C.

    1985-01-01

    This paper describes recent measurements of the subcritical neutron multiplication factor using the /sup 252/Cf source-driven neutron noise analysis method. This work was supported by a program of collaboration between the United States Department of Energy and the Power Reactor and Nuclear Fuel Development Corporation of Japan related to the development of fast breeder technology. The experiment reported consists of a configuration of two interacting tanks of uranyl nitrate aqueous solution with different uranium concentrations in each tank. The /sup 252/Cf-source-driven neutron noise analysis method obtains the subcriticality from the signals of three detectors: the first, a parallel plate ionization chamber with /sup 252/Cf electroplated on one of its plates that is located in or near the system containing the fissile material, and produces an electrical pulse for every spontaneous fission that occurs and thereby serves as a timed source of fission neutrons; and the second and third detectors that are placed in or near the system containing fissile material and serve to detect particles from the fission chain multiplication process. 9 refs.

  10. Subcritical ethylic biodiesel production from wet animal fat and vegetable oils: A net energy ratio analysis

    DOE PAGES

    Sales, Emerson A.; Ghirardi, Maria L.; Jorquera, Orlando

    2016-08-23

    Ethylic transesterification process for biodiesel production without any chemical or biochemical catalysts at different subcritical thermodynamic conditions was performed using wet animal fat, soybean and palm oils as feedstock. The results indicate that 2 h of reaction at 240 °C with pressures varying from 20 to 45 bar was sufficient to transform almost all lipid fraction of the samples to biodiesel, depending on the reactor dead volume and proportions between reactants. Conversions of 100%, 84% and 98.5% were obtained for animal fat, soybean oil and palm oil, respectively, in the presence of water, with a net energy ration values ofmore » 2.6, 2.1 and 2.5 respectively. Finally, these results indicate that the process is energetically favorable, and thus represents a cleaner technology with environmental advantages when compared to traditional esterification or transesterification processes.« less

  11. Subcritical ethylic biodiesel production from wet animal fat and vegetable oils: A net energy ratio analysis

    SciTech Connect

    Sales, Emerson A.; Ghirardi, Maria L.; Jorquera, Orlando

    2016-08-23

    Ethylic transesterification process for biodiesel production without any chemical or biochemical catalysts at different subcritical thermodynamic conditions was performed using wet animal fat, soybean and palm oils as feedstock. The results indicate that 2 h of reaction at 240 °C with pressures varying from 20 to 45 bar was sufficient to transform almost all lipid fraction of the samples to biodiesel, depending on the reactor dead volume and proportions between reactants. Conversions of 100%, 84% and 98.5% were obtained for animal fat, soybean oil and palm oil, respectively, in the presence of water, with a net energy ration values of 2.6, 2.1 and 2.5 respectively. Finally, these results indicate that the process is energetically favorable, and thus represents a cleaner technology with environmental advantages when compared to traditional esterification or transesterification processes.

  12. Mesoscopic approach to subcritical fatigue crack growth

    NASA Astrophysics Data System (ADS)

    Araújo, Maycon S.; Vieira, André P.; Andrade, José S.; Herrmann, Hans J.

    2016-10-01

    We investigate a model for fatigue crack growth in which damage accumulation is assumed to follow a power law of the local stress amplitude, a form that can be generically justified on the grounds of the approximately self-similar aspect of microcrack distributions. Our aim is to determine the relation between model ingredients and the Paris exponent governing subcritical crack-growth dynamics at the macroscopic scale, starting from a single small notch propagating along a fixed line. By a series of analytical and numerical calculations, we show that, in the absence of disorder, there is a critical damage-accumulation exponent γ , namely γc=2 , separating two distinct regimes of behavior for the Paris exponent m . For γ >γc , the Paris exponent is shown to assume the value m =γ , a result that proves robust against the separate introduction of various modifying ingredients. Explicitly, we deal here with (i) the requirement of a minimum stress for damage to occur, (ii) the presence of disorder in local damage thresholds, and (iii) the possibility of crack healing. On the other hand, in the regime γ <γc , the Paris exponent is seen to be sensitive to the different ingredients added to the model, with rapid healing or a high minimum stress for damage leading to m =2 for all γ <γc , in contrast with the linear dependence m =6 -2 γ observed for very long characteristic healing times in the absence of a minimum stress for damage. Upon the introduction of disorder on the local fatigue thresholds, which leads to the possible appearance of multiple cracks along the propagation line, the Paris exponent tends to m ≈4 for γ ≲2 while retaining the behavior m =γ for γ ≳4 .

  13. Investigation of radiation fields outside the Sub-critical Assembly in Dubna.

    PubMed

    Seltbor, P; Lopatkin, A; Gudowski, W; Shvetsov, V; Polanski, A

    2005-01-01

    The radiation fields outside the planned experimental Sub-critical Assembly in Dubna (SAD) have been studied in order to provide a basis for the design of the concrete shielding that cover the reactor core. The effective doses around the reactor, induced by leakage of neutrons and photons through the shielding, have been determined for a shielding thickness varying from 100 to 200 cm. It was shown that the neutron flux and the effective dose is higher above the shielding than at the side of it, owing to the higher fraction of high-energy spallation neutrons emitted in the direction of the incident beam protons. At the top, the effective dose was found to be -150 microSv s(-1) for a concrete thickness of 100 cm, while -2.5 microSv s(-1) for a concrete thickness of 200 cm. It was also shown that the high-energy neutrons (> 10 MeV), which are created in the proton-induced spallation interactions in the target, contribute for the major part of the effective doses outside the reactor.

  14. Nonlinear excitation of subcritical fast ion-driven modes

    NASA Astrophysics Data System (ADS)

    Lesur, M.; Itoh, K.; Ido, T.; Itoh, S.-I.; Kosuga, Y.; Sasaki, M.; Inagaki, S.; Osakabe, M.; Ogawa, K.; Shimizu, A.; Ida, K.; the LHD experiment Group

    2016-05-01

    In collisionless plasma, it is known that linearly stable modes can be destabilized (subcritically) by the presence of structures in phase-space. The growth of such structures is a nonlinear, kinetic mechanism, which provides a channel for free-energy extraction, different from conventional inverse Landau damping. However, such nonlinear growth requires the presence of a seed structure with a relatively large threshold in amplitude. We demonstrate that, in the presence of another, linearly unstable (supercritical) mode, wave-wave coupling can provide a seed, which can lead to subcritical instability by either one of two mechanisms. Both mechanisms hinge on a collaboration between fluid nonlinearity and kinetic nonlinearity. If collisional velocity diffusion is low enough, the seed provided by the supercritical mode overcomes the threshold for nonlinear growth of phase-space structure. Then, the supercritical mode triggers the conventional subcritical instability. If collisional velocity diffusion is too large, the seed is significantly below the threshold, but can still grow by a sustained collaboration between fluid and kinetic nonlinearities. Both of these subcritical instabilities can be triggered, even when the frequency of the supercritical mode is rapidly sweeping. These results were obtained by modeling the subcritical mode kinetically, and the impact of the supercritical mode by simple wave-wave coupling equations. This model is applied to bursty onset of geodesic acoustic modes in an LHD experiment. The model recovers several key features such as relative amplitude, timescales, and phase relations. It suggests that the strongest bursts are subcritical instabilities, with sustained collaboration between fluid and kinetic nonlinearities.

  15. ITEP Subcritical Neutron Generator driven by charged particle accelerator

    SciTech Connect

    Shvedov, O.V.; Chuvilo, I.V.; Vasiliev, V.V.

    1995-10-01

    A research facility prototype including a combination of a linear accelerator, a neutron generating target, a nuclear safety ensuring and means of its attainment for Subcritical Neutron Generator are considered. The scheme of the multiplying is shown. The assembly will be mounted in the body of the partly dismantled ITEP HWR. Requirements for subcritical assembly are worked out and their feasibility within the framework of the heavy-water blanket is shown. The facility`s application as a full-scale model of more powerful installations of this kind and for fundamental experimental research has been investigated.

  16. Subcritical-supercritical bifurcation crossover in directional solidification

    SciTech Connect

    Liu, D.; Williams, L.; Cummins, H. )

    1994-12-01

    The Mullins-Sekerka planar-cellular instability in directional solidification should be subcritical when the partition coefficient [ital k][lt]0.45 and latent heat is ignored. However, Merchant and Davis [Phys. Rev. Lett. [bold 63], 573 (1989)] predicted that as the solute concentration is reduced, the increasingly important thermal diffusion field would lead to a crossover from a subcritical to a supercritical bifurcation. We have performed directional solidification experiments on a series of succinonitrile samples containing different concentrations of Coumarin 152, and have found preliminary evidence for the predicted crossover at a concentration [ital C][sub [ital t

  17. Cermet fuel reactors

    SciTech Connect

    Cowan, C.L.; Palmer, R.S.; Van Hoomissen, J.E.; Bhattacharyya, S.K.; Barner, J.O.

    1987-09-01

    Cermet fueled nuclear reactors are attractive candidates for high performance space power systems. The cermet fuel consists of tungsten-urania hexagonal fuel blocks characterized by high strength at elevated temperatures, a high thermal conductivity and resultant high thermal shock resistance. Key features of the cermet fueled reactor design are (1) the ability to achieve very high coolant exit temperatures, and (2) thermal shock resistance during rapid power changes, and (3) two barriers to fission product release - the cermet matrix and the fuel element cladding. Additionally, thre is a potential for achieving a long operating life because of (1) the neutronic insensitivity of the fast-spectrum core to the buildup of fission products and (2) the utilization of a high strength refractory metal matrix and structural materials. These materials also provide resistance against compression forces that potentially might compact and/or reconfigure the core. In addition, the neutronic properties of the refractory materials assure that the reactor remains substantially subcritical under conditions of water immersion. It is concluded that cermet fueled reactors can be utilized to meet the power requirements for a broad range of advanced space applications. 4 refs., 4 figs., 3 tabs.

  18. Subcritical crack growth behavior of dispersion oxide ceramics.

    PubMed

    Kirsten, Armin; Begand, Sabine; Oberbach, Thomas; Telle, Rainer; Fischer, Horst

    2010-10-01

    Zirconia (Y-TZP) is used as material for components of implants and prostheses because of its high short-term strength. The mechanical long-term reliability, however, is limited for Y-TZP because of hydrothermal aging effects and a pronounced tendency for subcritical crack growth. The hypothesis of this study was that a substantial amount of alumina in a zirconia matrix can help to significantly suppress subcritical crack growth and thereby improve the mechanical long-term reliability. The Weibull parameters as well as the parameters of the subcritical crack growth were determined for Alumina, Y-TZP, and two dispersion ceramics, that is Alumina Toughened Zirconia (ATZ, 20% alumina/80% Y-TZP), and Zirconia Toughened Alumina (ZTA, 75% alumina/25% Y-TZP). The long-term failure probability as a function of service time was predicted for the four ceramics. The parameter n of the subcritical crack growth was approx. 80% higher for ATZ compared to Y-TZP. In consequence, the estimated lifetime revealed a significant better mechanical long-term reliability for ATZ. It can be concluded that tailored dispersion oxide ceramics can address the aging problem of monolithic zirconia. This makes ATZ very interesting for components of joint replacement as well as for dental prostheses and implants.

  19. Extraction of antioxidants from Chlorella sp. using subcritical water treatment

    NASA Astrophysics Data System (ADS)

    Zakaria, S. M.; Mustapa Kamal, S. M.; Harun, M. R.; Omar, R.; Siajam, S. I.

    2017-06-01

    Chlorella sp. microalgae is one of the main source of natural bioactive compounds used in the food and pharmaceutical industries. Subcritical water extraction is the technique that offers an efficient, non-toxic, and environmental-friendly method to obtain natural ingredients. In this work, the extracts of Chlorella sp. microalgae was evaluated in terms of: chemical composition, extraction (polysaccharides) yield and antioxidant activity, using subcritical water extraction. Extractions were performed at temperatures ranging from 100°C to 300°C. The results show that by using subcritical water, the highest yield of polysaccharides is 23.6 that obtained at 150°C. Analysis on the polysaccharides yield show that the contents were highly influenced by the extraction temperature. The individual antioxidant activity were evaluated by in vitro assay using a free radical method. In general, the antioxidant activity of the extracts obtained at different water temperatures was high, with values of 31.08-54.29 . The results indicated that extraction by subcritical water was effective and Chlorella sp. can be a useful source of natural antioxidants.

  20. Subcritical Destabilization of African Easterly Waves by Saharan Mineral Dust

    NASA Astrophysics Data System (ADS)

    Nathan, T. R.; Grogan, D.; Chen, S. H.

    2016-12-01

    A theoretical framework is presented that exposes the radiative-dynamical relationships that govern the subcritical destabilization of African easterly waves (AEWs) by Saharan mineral dust (SMD) aerosols. The framework is built on coupled equations for quasigeostrophic potential vorticity, temperature, and SMD mixing ratio. A perturbation analysis yields, for a subcritical, but otherwise arbitrary, zonal-mean background state, analytical expressions for the growth rate and frequency of the AEWs. The expressions are functions of the domain-averaged wave activity, which is primarily modulated by the background potential vorticity gradient, Doppler-shifted phase speed, and spatial variations in the background SMD field. Using an idealized version of the Weather Research and Forecasting (WRF) model that is coupled to an interactive dust model, a linear analysis shows, in agreement with the theoretical prediction, that for a realistic, subcritical African easterly jet (AEJ) and background SMD distribution consistent with observations, the SMD destabilizes the AEWs and slows their eastward propagation. The SMD-induced growth rates are commensurate with those obtained in previous dust-free studies in which the AEWs grow on AEJs that are supercritical with respect to the threshold for barotropic-baroclinic instability. The clarity of the theoretical framework can serve as a tool for understanding and predicting the effects of SMD aerosols on the linear instability of AEWs in subcritical, zonally averaged AEJs.

  1. Subcritical crack-growth behavior in advanced silicon nitride ceramics

    NASA Astrophysics Data System (ADS)

    Bhatnagar, Ajay

    Advanced silicon nitride ceramics (Sisb3Nsb4) are leading candidates for structural components in gas turbine and reciprocating engines. However, widespread use of these materials has been deterred due to their low fracture toughness under tensile loads. In the last decade, novel processing techniques have allowed extrinsic toughening of this material through grain bridging processes. The extrinsic toughening mechanisms, however, are prone to subcritical crack-growth processes through environmental, mechanical and high temperature degradation mechanisms. Understanding these failure mechanisms is critical for long term reliability and design. In the first part of this study, fracture and environmentally-assisted subcritical crack-growth processes were examined in bulk Y-Si-Al-O-N oxynitride glasses with compositions typical of the grain boundary phase of silicon nitride ceramics. Both long crack as well as short crack behavior were investigated to establish a reliable fracture toughness value and to elucidate the anomalous densification behavior of the oxynitride glass under indentation loads. Environmentally assisted subcritical crack-growth processes were studied in inert, moist and wet environments under both cyclic and static loading conditions and compared to commercial soda lime and borosilicate glasses. The second part of this study involved the effect of loading, microstructure and temperature on subcritical crack-growth behavior in silicon nitride ceramics. Crack-growth rates under an alternating applied stress intensity were compared to those under static loads. The effect of microstructure on fatigue crack-growth rates was determined in silicon nitrides sintered using different processing techniques and with different grain sizes. Unique experimental techniques were used to determine subcritical crack-growth behavior from room temperature to elevated temperatures of 1250sp°C. Frictional wear models were used to explain the trends in experimental data at

  2. Influence of surrounding environment on subcritical crack growth in marble

    NASA Astrophysics Data System (ADS)

    Nara, Yoshitaka; Kashiwaya, Koki; Nishida, Yuki; , Toshinori, Ii

    2017-06-01

    Understanding subcritical crack growth in rock is essential for determining appropriate measures to ensure the long-term integrity of rock masses surrounding structures and for construction from rock material. In this study, subcritical crack growth in marble was investigated experimentally, focusing on the influence of the surrounding environment on the relationship between the crack velocity and stress intensity factor. The crack velocity increased with increasing temperature and/or relative humidity. In all cases, the crack velocity increased with increasing stress intensity factor. However, for Carrara marble (CM) in air, we observed a region in which the crack velocity still increased with temperature, but the increase in the crack velocity with increasing stress intensity factor was not significant. This is similar to Region II of subcritical crack growth observed in glass in air. Region II in glass is controlled by mass transport to the crack tip. In the case of rock, the transport of water to the crack tip is important. In general, Region II is not observed for subcritical crack growth in rock materials, because rocks contain water. Because the porosity of CM is very low, the amount of water contained in the marble is also very small. Therefore, our results imply that we observed Region II in CM. Because the crack velocity increased in both water and air with increasing temperature and humidity, we concluded that dry conditions at low temperature are desirable for the long-term integrity of a carbonate rock mass. Additionally, mass transport to the crack tip is an important process for subcritical crack growth in rock with low porosity.

  3. Measurement of prompt neutron generation time at the VIR-2M pulsed nuclear reactor

    NASA Astrophysics Data System (ADS)

    Glukhov, L. Yu.; Kotkov, S. P.; Kuznetsov, M. S.; Chursin, S. S.

    2016-12-01

    The prompt neutron generation time is measured in the core of the VIR-2M research nuclear reactor. The measurements are performed using the Babala method while the reactor is in the subcritical state. The VIR-2M reactor and the relevant experimental equipment are briefly described, and the experimental procedure and data processing technique are presented. It is shown that the prompt neutron generation time with empty experimental channels is 35 ± 1 μs.

  4. Measurement of prompt neutron generation time at the VIR-2M pulsed nuclear reactor

    SciTech Connect

    Glukhov, L. Yu.; Kotkov, S. P.; Kuznetsov, M. S.; Chursin, S. S.

    2016-12-15

    The prompt neutron generation time is measured in the core of the VIR-2M research nuclear reactor. The measurements are performed using the Babala method while the reactor is in the subcritical state. The VIR-2M reactor and the relevant experimental equipment are briefly described, and the experimental procedure and data processing technique are presented. It is shown that the prompt neutron generation time with empty experimental channels is 35 ± 1 μs.

  5. The Physics Design for a Fusion Driven Sub-critical System

    NASA Astrophysics Data System (ADS)

    Bin, Wu

    2002-11-01

    The Fusion Driven Sub-critical System (FDS) is a sub-critical nuclear energy system drive by fusion neutron source, which provides a feasible, safe, economic and highly efficient potential of disposing High Level Waste (HLW) and produce fission nuclear fuel as a early application of fusion technology. This paper reviews the past physics reactor design of fusion-fission hybrid reactor in China, and a low aspect ratio tokamak energy system that has been proposed, which aims at high β, good confinement, and steady-state operation in a compact configuration at modest field. The system includes a low aspect ratio tokamak as fusion neutron driver, a radioactivity clean nuclear power system as blanket and novel concept of liquid metal conductor as centre conductor post. Parameters of such kind reactor are the following. Major radius 1.4m, Minor radius 1m, plasma current 9.2MA, Toroidal field 2.5T, Plasma edge q=5, Average density 1.6 10^20m^3, Average temperature 10keV, Plasma volume 50m^3, Bootstrap current fraction 0.72, Fusion power 100MW, Drive power 28MW, Neutron wall loading 1.0MW/m-2. The plasma configuration is an important part in the low-A tokamak. The Eq code has been used to get a equilibrium. From this calculation, we have found a simple set of PF coils that satisfies the requirements of the large elongation plasma configuration and a vertical field with less curve field lines in the low-A tokamak. The natural elongation can be attributed mostly to differences in the current density profile. In order to determine the feasibility of the low-A tokamak operation, a transient simulation has been made which includes the equilibrium, transport and plasma position shape control in the low-A tokamak. A 1-1/2 equilibrium evolution code has been used to make this simulation. The code is two-dimensional time dependent free boundary simulation code that advances the MHD equations describing the transport time-scale evolution of a axisymmetric tokamak plasma.

  6. Complete degradation of Orange G by electrolysis in sub-critical water.

    PubMed

    Yuksel, Asli; Sasaki, Mitsuru; Goto, Motonobu

    2011-06-15

    Complete degradation of azo dye Orange G was studied using a 500 mL continuous flow reactor made of SUS 316 stainless steel. In this system, a titanium reactor wall acted as a cathode and a titanium plate-type electrode was used as an anode in a subcritical reaction medium. This hydrothermal electrolysis process provides an environmentally friendly route that does not use any organic solvents or catalysts to remove organic pollutants from wastewater. Reactions were carried out from 30 to 90 min residence times at a pressure of 7 MPa, and at different temperatures of 180-250°C by applying various direct currents ranging from 0.5 to 1A. Removal of dye from the product solution and conversion of TOC increased with increasing current value. Moreover, the effect of salt addition on degradation of Orange G and TOC conversion was investigated, because in real textile wastewater, many salts are also included together with dye. Addition of Na(2)CO(3) resulted in a massive degradation of the dye itself and complete mineralization of TOC, while NaCl and Na(2)SO(4) obstructed the removal of Orange G. Greater than 99% of Orange G was successfully removed from the product solution with a 98% TOC conversion.

  7. Efficient, high-speed methane fermentation for sewage sludge using subcritical water hydrolysis as pretreatment.

    PubMed

    Yoshida, Hiroyuki; Tokumoto, Hayato; Ishii, Kyoko; Ishii, Ryo

    2009-06-01

    A novel biomass-energy process for the production of methane from sewage sludge using a subcritical water (sub-CW) hydrolysis reaction as pretreatment is proposed. The main substances of sewage sludge hydrolyzed by sub-CW at 513 K for 10 min were acetic acid, formic acid, pyroglutamic acid, alanine, and glycine. Fermentation experiments were conducted in an anaerobic-sludge reactor for two different samples: real sewage sludge and a model solution containing components typically produced by the sub-CW pretreatment of sewage sludge. In the experiment for the sub-CW pretreatment of sewage sludge, methane generation was twice that for non-pretreatment after 3 days of incubation. In the model experiment, the methane conversion was about 40% with the application of mixture of organic acids and amino acids after 5 days of incubation. Furthermore, the methane conversion was about 60% for 2 days when only organic acids, such as acetic acid and formic acid, were applied. Because acetic acid is the key intermediate and main precursor of the methanogenesis step, fermentation experiments were conducted in an anaerobic-sludge reactor with high concentrations of acetic acid (0.01-0.1M). Nearly 100% of acetic acid was converted to methane and carbon dioxide in 1-3 days.

  8. The Transmutation of Nuclear Waste in the Two-Zone Subcritical System Driven by High- Intensity Neutron Generator - 12098

    SciTech Connect

    Babenko, V.O.; Gulik, V.I.; Pavlovych, V.M.

    2012-07-01

    The main problems of transmutation of high-level radioactive waste (minor actinides and long-lived fission products) are considered in our work. The range of radioactive waste of nuclear power is analyzed. The conditions under which the transmutation of radioactive waste will be most effective are analyzed too. The modeling results of a transmutation of the main radioactive isotopes are presented and discussed. The transmutation of minor actinides and long-lived fission products are modeled in our work (minor actinides - Np-237, Am-241, Am-242, Am-243, Cm-244, Cm-245; long-lived fission products - I-129, Tc-99). The two-zone subcritical system is calculated with help of different neutron-physical codes (MCNP, Scale, Montebarn, Origen). The ENDF/B-VI nuclear data library used in above calculations. Thus, radioactive wastes can be divided into two main groups that need to be transmuted. The minor actinides form the first group and the long-lived fission products form the second one. For the purpose of effective transmutation these isotopes must be extracted from the spent nuclear fuel with the help of either PUREX technology or pyrometallurgical technology. The two-zone reactor system with fast and thermal regions is more effective for nuclear waste transmutation than the one-zone reactor. Modeling results show that nearly all radioactive wastes can be transmuted in the two-zone subcritical system driven by a high-intensity neutron generator with the external neutron source strength of 1.10{sup 13} n/sec. Obviously, transmutation rate will increase with a rise of the external neutron source strength. From the results above we can also see that the initial loading of radioactive isotopes into the reactor system should exceed by mass those isotopes that are finally produced. (authors)

  9. Sequential extraction of polycyclic aromatic hydrocarbons using subcritical water.

    PubMed

    Latawiec, Agnieszka E; Reid, Brian J

    2010-02-01

    A rapid sequential subcritical (superheated) water extraction method for polycyclic aromatic hydrocarbons (PAHs) in contaminated soil and sediment is presented. Decreasing the polarity of water by successive increase of the extraction temperature from 50 degrees C to 200 degrees C at the moderate pressure (10.3MPa) enabled selective, non-exhaustive extractions to be performed. Concurrent with increasing temperatures to 150 degrees C there was an increase in PAH extraction efficiencies. For the majority of determinations no significant differences between extractions at 150 degrees C and 200 degrees C were observed. Varied extraction efficiencies of PAHs at the same extraction conditions reflected dissimilarities between environmental matrices investigated. Selective subcritical water extraction of PAHs was proportional to their octanol-water partition coefficients. This technique may be applicable in evaluation of risks associated with PAH contaminated sites and in assessments of their bioremediation potential.

  10. Subcritical patterns and dissipative solitons due to intracavity photonic crystals

    SciTech Connect

    Gomila, Damia; Oppo, Gian-Luca

    2007-10-15

    Manipulation of the bifurcation structure of nonlinear optical systems via intracavity photonic crystals is demonstrated. In particular, subcritical regions between spatially periodic states are stabilized by modulations of the material's refractive index. An family of dissipative solitons within this bistability range due to the intracavity photonic crystal is identified and characterized in both one and two transverse dimensions. Nontrivial snaking of the modulated-cavity soliton solutions is also presented.

  11. A thermodynamic analysis of propagating subcritical cracks with cohesive zones

    NASA Technical Reports Server (NTRS)

    Allen, David H.

    1993-01-01

    The results of the so-called energetic approach to fracture with particular attention to the issue of energy dissipation due to crack propagation are applied to the case of a crack with cohesive zone. The thermodynamic admissibility of subcritical crack growth (SCG) is discussed together with some hypotheses that lead to the derivation of SCG laws. A two-phase cohesive zone model for discontinuous crack growth is presented and its thermodynamics analyzed, followed by an example of its possible application.

  12. Breaking rocks made easy: subcritical processes and tectonic predesign

    NASA Astrophysics Data System (ADS)

    Voigtlaender, Anne; Krautblatter, Michael

    2017-04-01

    In geomorphic studies, to change in landforms, e.g. by rock slope failure, fluvial or glacial erosion, a threshold is commonly assumed, which is crossed either by an increase in external driving or a decrease of internal resisting forces, respectively. If the threshold is crossed, bedrock breaks and slope fails, rivers incise and glaciers plug and sew their bed. Here we put forward a focus on the decrease of the resisting forces, as an increase in the driving forces, to match the strength of bedrock, is not that likely. We suggest that the degradation of resisting forces of bedrock can be better explained by subcritical processes like creep, fatigue and stress corrosion interplaying with tectonic predesign. Both concepts, subcritical processes and tectonic predesign have been issued in the last century, but have not been widely accepted nor have their assumptions been explicitly stressed in recent case studies. Moreover both concepts profit especially on scale issues if merged. Subcritical crack growth, includes different mechanisms promoting fractures well below the ultimate strength. Single infinitesimal but irreversible damage and deformations are induced in the material over time. They interact with inherent microstructural flaws and low applied stresses, limiting local strength and macroscopic behavior of bedrock. This reissues the concept of tectonic predesigned, as proposed by A.E. Scheidegger, which not only encompasses structural features that determine the routing of drainage patterns and shear planes, e.g. joints, faults and foliations, but also the (neo)tectonic stress-field and the (in-situ) strain state of bedrocks and mountains. Combining subcritical processes and tectonic predesign we can better explain, why and where we see a dissected, eroded and geomorphic divers' landscape. In this conceptual framework actual magnitudes of the driving forces are accounted for and so is the nature of the bedrock material, to better understand the trajectories of

  13. Droplet turbulence interactions under subcritical and supercritical conditions

    NASA Astrophysics Data System (ADS)

    Coy, E. B.; Greenfield, S. C.; Ondas, M. S.; Song, Y.-H.; Spegar, T. D.; Santavicca, D. A.

    1993-11-01

    The goal of this research is to experimentally characterize the behavior of droplets in vaporizing liquid sprays under conditions typical of those encountered in high pressure combustion systems such as liquid fueled rocket engines. Of particular interest are measurements of droplet drag, droplet heating, droplet vaporization, droplet distortion, and secondary droplet breakup, under both subcritical and supercritical conditions. The paper presents a brief description of the specific accomplishments which have been made over the past year.

  14. Droplet turbulence interactions under subcritical and supercritical conditions

    NASA Technical Reports Server (NTRS)

    Coy, E. B.; Greenfield, S. C.; Ondas, M. S.; Song, Y.-H.; Spegar, T. D.; Santavicca, D. A.

    1993-01-01

    The goal of this research is to experimentally characterize the behavior of droplets in vaporizing liquid sprays under conditions typical of those encountered in high pressure combustion systems such as liquid fueled rocket engines. Of particular interest are measurements of droplet drag, droplet heating, droplet vaporization, droplet distortion, and secondary droplet breakup, under both subcritical and supercritical conditions. The paper presents a brief description of the specific accomplishments which have been made over the past year.

  15. Subcritical dynamo bifurcation in the Taylor-Green flow.

    PubMed

    Ponty, Y; Laval, J-P; Dubrulle, B; Daviaud, F; Pinton, J-F

    2007-11-30

    We report direct numerical simulations of dynamo generation for flow generated using a Taylor-Green forcing. We find that the bifurcation is subcritical and show its bifurcation diagram. We connect the associated hysteretic behavior with hydrodynamics changes induced by the action of the Lorentz force. We show the geometry of the dynamo magnetic field and discuss how the dynamo transition can be induced when an external field is applied to the flow.

  16. Development concept for a small, split-core, heat-pipe-cooled nuclear reactor

    NASA Technical Reports Server (NTRS)

    Lantz, E.; Breitwieser, R.; Niederauer, G. F.

    1974-01-01

    There have been two main deterrents to the development of semiportable nuclear reactors. One is the high development costs; the other is the inability to satisfy with assurance the questions of operational safety. This report shows how a split-core, heat-pipe cooled reactor could conceptually eliminate these deterrents, and examines and summarizes recent work on split-core, heat-pipe reactors. A concept for a small reactor that could be developed at a comparatively low cost is presented. The concept would extend the technology of subcritical radioisotope thermoelectric generators using 238 PuO2 to the evolution of critical space power reactors using 239 PuO2.

  17. A proton-driven, intense, subcritical, fission neutron source for radioisotope production

    SciTech Connect

    Jongen, Y.

    1995-10-01

    {sup 99m}Tc, the most frequently used radioisotope in nuclear medicine, is distributed as {sup 99}Mo=>{sup 99m}Tc generators. {sup 99}Mo is a fission product of {sup 235}U. To replace the aging nuclear reactors used today for this production, the author proposes to use a spallation neutron source, with neutron multiplication by fission. A 150 MeV, H{sup {minus}} cyclotron can produce a 225 kW proton beam with 50% total system energy efficiency. The proton beam would hit a molten lead target, surrounded by a water moderator and a graphite reflector, producing around 0.96 primary neutron per proton. The primary spallation neutrons, moderated, would strike secondary targets containing a subcritical amount of {sup 235}U. The assembly would show a k{sub eff} of 0.8, yielding a fivefold neutron multiplication. The thermal neutron flux at the targets location would be 2 {times} 10{sup 14} n/cm{sup 2}.s, resulting in a fission power of 500 to 750 kW. One such system could supply the world demand in {sup 99}Mo, as well as other radioisotopes. Preliminary indications show that the cost would be lower than the cost of a commercial 10 MW isotope production reactor. The cost of operation, of disposal of radiowaste and of decommissioning should be significantly lower as well. Finally, the non-critical nature of the system would make it more acceptable for the public than a nuclear reactor and should simplify the licensing process.

  18. Subcritical Hopf bifurcations in low-density jets

    NASA Astrophysics Data System (ADS)

    Zhu, Yuanhang; Gupta, Vikrant; Li, Larry K. B.

    2016-11-01

    Low-density jets are known to bifurcate from a steady state (a fixed point) to self-excited oscillations (a periodic limit cycle) when the Reynolds number increases above a critical value corresponding to the Hopf point, ReH . In the literature, this Hopf bifurcation is often considered to be supercritical because the self-excited oscillations appear only when Re > ReH . However, we find that under some conditions, there exists a hysteretic bistable region at ReSN < Re < ReH , where ReSN denotes a saddle-node bifurcation point. This shows that the Hopf bifurcation can also be subcritical, which has three main implications. First, low-density jets could be triggered into self-excited oscillations even when Re < ReH . Second, in the modeling of low-density jets, the subcritical or supercritical nature of the Hopf bifurcation should be taken into account because the former is caused by cubic nonlinearity whereas the latter is caused by square nonlinearity. Third, the response of the system to external forcing and noise depends on its proximity to the bistable region. Therefore, when investigating the forced response of low-density jets, it is important to consider whether the Hopf bifurcation is subcritical or supercritical.

  19. A Numerical Model for Coupling of Neutron Diffusion and Thermomechanics in Fast Burst Reactors

    SciTech Connect

    Samet Y. Kadioglu; Dana A. Knoll; Cassiano De Oliveira

    2008-11-01

    We develop a numerical model for coupling of neutron diffusion adn termomechanics in order to stimulate transient behavior of a fast burst reactor. The problem involves solving a set of non-linear different equations which approximate neutron diffusion, temperature change, and material behavior. With this equation set we will model the transition from a supercritical to subcritical state and possible mechanical vibration.

  20. Experimental determination of neutron lifetimes through macroscopic neutron noise in the IPEN/MB-01 reactor

    SciTech Connect

    Gonnelli, Eduardo; Diniz, Ricardo

    2013-05-06

    The neutron lifetimes of the core, reflector, and global were experimentally obtained through macroscopic neutron noise in the IPEN/MB-01 reactor for five levels of subcriticality. The theoretical Auto Power Spectral Densities were derived by point kinetic equations taking the reflector effect into account, and one of the approaches consider an additional group of delayed neutrons.

  1. Experimental determination of neutron lifetimes through macroscopic neutron noise in the IPEN/MB-01 reactor

    NASA Astrophysics Data System (ADS)

    Gonnelli, Eduardo; Diniz, Ricardo

    2013-05-01

    The neutron lifetimes of the core, reflector, and global were experimentally obtained through macroscopic neutron noise in the IPEN/MB-01 reactor for five levels of subcriticality. The theoretical Auto Power Spectral Densities were derived by point kinetic equations taking the reflector effect into account, and one of the approaches consider an additional group of delayed neutrons.

  2. REMOVAL OF ORGANIC POLLUTANTS FROM SUBCRITICAL WATER WITH ACTIVATED CARBON

    SciTech Connect

    Steven B. Hawthorne; Arnaud J. Lagadec

    1999-08-01

    The Energy & Environmental Research Center (EERC) has demonstrated that controlling the temperature (and to a lesser extent, the pressure) of water can dramatically change its ability to extract organics and inorganics from matrices ranging from soils and sediments to waste sludges and coal. The dielectric constant of water can be changed from about 80 (a very polar solvent) to <5 (similar to a nonpolar organic solvent) by controlling the temperature (from ambient to about 400 C) and pressure (from about 5 to 350 bar). The EERC has shown that hazardous organic pollutants such as pesticides, PACS (polycyclic aromatic hydrocarbons), and PCBs (polychlorinated biphenyls) can be completely removed from soils, sludges, and sediments at temperatures (250 C) and pressures (<50 atm) that are much milder than typically used for supercritical water processes (temperature >374 C, pressure >221 atm). In addition, the process has been demonstrated to be particularly effective for samples containing very high levels of contaminants (e.g., part per thousand). Current projects include demonstrating the subcritical water remediation process at the pilot scale using an 8-liter system constructed under separate funding during 1997. To date, subcritical water has been shown to be an effective extraction fluid for removing a variety of organic pollutants from soils and sludges contaminated with fossil fuel products and waste products, including PACS from soil (e.g., town gas sites), refining catalysts, and petroleum tank bottom sludges; PCBs from soil and sediments; toxic gasoline components (e.g., benzene) from soil and waste sludge; and phenols from petroleum refinery sludges. The obvious need to clean the wastewater from subcritical water processes led to preliminary experiments with activated carbon placed in line after the extractor. Initial experiments were performed before and after cooling the extractant water (e.g., with water at 200 C and with water cooled to 25 C

  3. Sugars and char formation on subcritical water hydrolysis of sugarcane straw.

    PubMed

    Lachos-Perez, D; Tompsett, G A; Guerra, P; Timko, M T; Rostagno, M A; Martínez, Julian; Forster-Carneiro, T

    2017-11-01

    Subcritical water has potential as an environmentally friendly solvent for applications including hydrolysis, liquefaction, extraction, and carbonization. Here, we report hydrolysis of sugarcane straw, an abundant byproduct of sugar production, in a semi-continuous reactor at reaction temperatures ranging from 190 to 260°C and at operating pressures of 9 and 16MPa. The target hydrolysis products were total reducing sugars. The main products of sugarcane straw hydrolysis were glucose, xylose, arabinose, and galactose in addition to 5- hydroxymethylfurfural and furfural as minor byproducts. Fourier transform infrared spectroscopy and thermogravimetric analysis provided additional information on the surface and bulk composition of the residual biomass. Char was present on samples treated at temperatures equal to and greater than 190°C. Samples treated at 260°C contained approximately 20wt% char, yet retained substantial hemicellulose and cellulose content. Hydrolysis temperature of 200°C provided the greatest TRS yield while minimizing char formation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Combined subcritical water and enzymatic hydrolysis for reducing sugar production from coconut husk

    NASA Astrophysics Data System (ADS)

    Muharja, Maktum; Junianti, Fitri; Nurtono, Tantular; Widjaja, Arief

    2017-05-01

    Coconut husk wastes are abundantly available in Indonesia. It has a potential to be used into alternative renewable energy sources such as hydrogen using enzymatic hydrolysis followed by a fermentation process. Unfortunately, enzymatic hydrolysis is hampered by the complex structure of lignocellulose, so the cellulose component is hard to degrade. In this study, Combined Subcritical Water (SCW) and enzymatic hydrolysis are applied to enhance fermentable, thereby reducing production of sugar from coconut husk. There were two steps in this study, the first step was coconut husk pretreated by SCW in batch reactor at 80 bar and 150-200°C for 60 minutes reaction time. Secondly, solid fraction from the results of SCW was hydrolyzed using the mixture of pure cellulose and xylanase enzymes. Analysis was conducted on untreated and SCW-treated by gravimetric assay, liquid fraction after SCW and solid fraction after enzymatic hydrolysis using DNS assay. The maximum yield of reducing sugar (including xylose, arabinose glucose, galactose, mannose) was 1.254 gr per 6 gr raw material, representing 53.95% of total sugar in coconut husk biomass which was obtained at 150°C 80 bar for 60 minutes reaction time of SCW-treated and 6 hour of enzymatic hydrolysis using mixture of pure cellulose and xylanase enzymes (18.6 U /gram of coconut husk).

  5. Co-liquefaction of mixed culture microalgal strains under sub-critical water conditions.

    PubMed

    Dandamudi, Kodanda Phani Raj; Muppaneni, Tapaswy; Sudasinghe, Nilusha; Schaub, Tanner; Holguin, F Omar; Lammers, Peter J; Deng, Shuguang

    2017-07-01

    We report the co-liquefaction performance of unicellular, red alga Cyanidioschyzon merolae and Galdieria sulphuraria under sub-critical water conditions within a stainless-steel batch reactor under different temperatures (150-300°C), residence time (15-60min), and Cyanidioschyzon merolae to Galdieria sulphuraria mass loading (0-100%). Individual liquefaction of C. merolae and G. sulphuraria at 300°C achieved maximum biocrude oil yield of 18.9 and 14.0%, respectively. The yield of biocrude oil increased to 25.5%, suggesting a positive synergistic effect during the co-liquefaction of 80-20mass loading of C. merolae to G. sulphuraria. The biocrude oils were analyzed by FT-ICR MS which showed that co-liquefaction did not significantly affect the distribution of product compounds compared to individual oils. The co-liquefied biocrude and biochar have a higher-heating-value of 35.28 and 7.96MJ/kg. Ultimate and proximate analysis were performed on algae biomass, biocrude and biochar. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Fast Reactors

    NASA Astrophysics Data System (ADS)

    Esposito, S.; Pisanti, O.

    The following sections are included: * Elementary Considerations * The Integral Equation to the Neutron Distribution * The Critical Size for a Fast Reactor * Supercritical Reactors * Problems and Exercises

  7. Spatial and spectral effects in subcritical system pulsed experiments

    SciTech Connect

    Dulla, S.; Nervo, M.; Ravetto, P.; Carta, M.

    2013-07-01

    Accurate neutronic models are needed for the interpretation of pulsed experiments in subcritical systems. In this work, the extent of spatial and spectral effects in the pulse propagation phenomena is investigated and the analysis is applied to the GUINEVERE experiment. The multigroup cross section data is generated by the Monte Carlo SERPENT code and the neutronic evolution following the source pulse is simulated by a kinetic diffusion code. The results presented show that important spatial and spectral aspects need to be properly accounted for and that a detailed energy approach may be needed to adequately capture the physical features of the system to the pulse injection. (authors)

  8. The Nonlinear Dynamics of Time Dependent Subcritical Baroclinic Currents

    NASA Astrophysics Data System (ADS)

    Pedlosky, J.; Flierl, G. R.

    2006-12-01

    The nonlinear dynamics of baroclinically unstable waves in a time dependent zonal shear flow is considered in the framework of the two-layer Phillips model on the beta plane. In most cases considered in this study the amplitude of the shear is well below the critical value of the steady shear version of the model. Nevertheless, the time dependent problem in which the shear oscillates periodically is unstable, and the unstable waves grow to substantial amplitudes, in some cases with strongly nonlinear and turbulent characteristics. For very small values of the shear amplitude in the presence of dissipation an analytical, asymptotic theory predicts a self-sustained wave whose amplitude undergoes a nonlinear oscillation whose period is amplitude dependent. There is a sensitive amplitude dependence of the wave on the frequency of the oscillating shear when the shear amplitude is small. This behavior is also found in a truncated model of the dynamics, and that model is used to examine larger shear amplitudes. When there is a mean value of the shear in addition to the oscillating component, but such that the total shear is still subcritical, the resulting nonlinear states exhibit a rectified horizontal buoyancy flux with a nonzero time average as a result of the instability of the oscillating shear. For higher, still subcritical, values of the shear we have detected a symmetry breaking in which a second cross-stream mode is generated through an instability of the unstable wave although this second mode would by itself be stable on the basic time dependent current. For shear values that are substantially subcritical but of order of the critical shear, calculations with a full quasi-geostrophic numerical model reveal a turbulent flow generated by the instability. If the beta effect is disregarded the inviscid, linear problem is formally stable. However, our calculations show that a small degree of nonlinearity is enough to destabilize the flow leading to large amplitude

  9. Dynamics of parabolic problems with memory. Subcritical and critical nonlinearities

    NASA Astrophysics Data System (ADS)

    Li, Xiaojun

    2016-08-01

    In this paper, we study the long-time behavior of the solutions of non-autonomous parabolic equations with memory in cases when the nonlinear term satisfies subcritical and critical growth conditions. In order to do this, we show that the family of processes associated to original systems with heat source f(x, t) being translation bounded in Lloc 2 ( R ; L 2 ( Ω ) ) is dissipative in higher energy space M α , 0 < α ≤ 1, and possesses a compact uniform attractor in M 0 .

  10. Theoretical prediction of airplane stability derivatives at subcritical speeds

    NASA Technical Reports Server (NTRS)

    Tulinius, J.; Clever, W.; Nieman, A.; Dunn, K.; Gaither, B.

    1973-01-01

    The theoretical development and application is described of an analysis for predicting the major static and rotary stability derivatives for a complete airplane. The analysis utilizes potential flow theory to compute the surface flow fields and pressures on any configuration that can be synthesized from arbitrary lifting bodies and nonplanar thick lifting panels. The pressures are integrated to obtain section and total configuration loads and moments due side slip, angle of attack, pitching motion, rolling motion, yawing motion, and control surface deflection. Subcritical compressibility is accounted for by means of the Gothert similarity rule.

  11. Extending non-fatigue Mode I subcritical crack growth data to subcritical fatigue crack growth: Demonstration of the equivalence of the Charles' law and Paris law exponents

    NASA Astrophysics Data System (ADS)

    Keanini, Russell; Eppes, Martha-Cary

    2016-04-01

    Paris's law connects fatigue-induced subcritical crack growth and fatigue loading. Environmentally-driven subcritical crack growth, while a random process, can be decomposed into a spectrum of cyclic processes, where each spectral component is governed by Paris's law. Unfortunately, almost no data exists concerning the Paris law exponent, m; rather, the great majority of existing sub-critical crack growth measurements on rock have been carried out via Mode I tensile tests, where corresponding data are generally correlated using Charles' law, and where the latter, similar to Paris's law, exposes a power law relationship between crack growth rate and stress intensity. In this study, a statistical argument is used to derive a simple, rigorous relationship between the all-important Paris law and Charles law exponents, m and n. This result has a significant practical implication: subcritical fatigue crack growth in rock, driven by various random environmental weathering processes can now be predicted using available Mode I stress corrosion indices, n.

  12. Neutron noise measurements at the Delphi subcritical assembly

    SciTech Connect

    Szieberth, M.; Klujber, G.; Kloosterman, J. L.; De Haas, D.

    2012-07-01

    The paper presents the results and evaluations of a comprehensive set of neutron noise measurements on the Delphi subcritical assembly of the Delft Univ. of Technology. The measurements investigated the effect of different source distributions (inherent spontaneous fission and {sup 252}Cf) and the position of the detectors applied (both radially and vertically). The evaluation of the measured data has been performed by the variance-to-mean ratio (VTMR, Feynman-{alpha}), the autocorrelation (ACF, Rossi-{alpha}) and the cross-correlation (CCF) methods. The values obtained for the prompt decay constant show a strong bias, which depends both on the detector position and on the source distribution. This is due to the presence of higher modes in the system. It has been observed that the {alpha} value fitted is higher when the detector is close to the boundary of the core or to the {sup 252}Cf point-source. The higher alpha-modes have also been observed by fitting functions describing two alpha-modes. The successful set of measurement also provides a good basis for further theoretical investigations including the Monte Carlo simulation of the noise measurements and the calculation of the alpha-modes in the Delphi subcritical assembly. (authors)

  13. Hydrolysis of sweet blue lupin hull using subcritical water technology.

    PubMed

    Ciftci, Deniz; Saldaña, Marleny D A

    2015-10-01

    Hydrolysis of sweet blue lupin hulls was conducted in this study using subcritical water technology. Effects of process parameters, such as pressure (50-200 bar), temperature (160-220°C), flow rate (2-10 mL/min), and pH (2-12), were studied to optimize maximum hemicellulose sugars recovery in the extracts. Extracts were analyzed for total hemicellulose sugars, phenolics and organic carbon contents and solid residues left after treatments were also characterized. Temperature, flow rate, and pH had a significant effect on hemicellulose sugar removal; however, the effect of pressure was not significant. The highest yield of hemicellulose sugars in the extracts (85.5%) was found at 180°C, 50 bar, 5 mL/min and pH 6.2. The thermal stability of the solid residue obtained at optimum conditions improved after treatment and the crystallinity index increased from 11.5% to 58.6%. The results suggest that subcritical water treatment is a promising technology for hemicellulose sugars removal from biomass. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Extraction of defatted rice bran with subcritical aqueous acetone.

    PubMed

    Chiou, Tai-Ying; Neoh, Tze Loon; Kobayashi, Takashi; Adachi, Shuji

    2012-01-01

    Defatted rice bran extracts were obtained by subcritical treatment using aqueous acetone as extractant. Treatment with 40% (v/v) acetone at 230 °C for 5 min yielded an extract with the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (0.274 mmol of ascorbic acid/g of bran), total carbohydrate (0.188 g/g of bran), protein (0.512 g/g of bran), and total phenolic contents (88.2 mg of gallic acid/g of bran). The effect of treatment temperature (70-230 °C) was investigated using 40% (v/v) acetone, and the extract under 230 °C treatment showed the highest levels of all the determinations described above. The extracts obtained with various concentrations of aqueous acetone were subjected to UV absorption spectra and HPLC analysis, and the results showed changes in composition and polarity. Antioxidative activity evaluated against oxidation of bulk linoleic acid of the extract obtained with 80% (v/v) acetone was higher than that not only of the extract from subcritical water treatment but also of that obtained 40% (v/v) acetone treatment.

  15. Hydrolysis of whey protein isolate using subcritical water.

    PubMed

    Espinoza, Ashley D; Morawicki, Rubén O; Hager, Tiffany

    2012-01-01

    Hydrolyzed whey protein isolate (WPI) is used in the food industry for protein enrichment and modification of functional properties. The purpose of the study was to determine the feasibility of subcritical water hydrolysis (SWH) on WPI and to determine the temperature and reaction time effects on the degree of hydrolysis (DH) and the production of peptides and free amino acids (AAs). Effects of temperature (150 to 320 °C) and time (0 to 20 min) were initially studied with a central composite rotatable design followed by a completely randomized factorial design with temperature (250 and 300 °C) and time (0 to 50 min) as factors. SWH was conducted in an electrically heated, 100-mL batch, high pressure vessel. The DH was determined by a spectrophotometric method after derivatization. The peptide molecular weights (MWs) were analyzed by gel electrophoresis and mass spectrometry, and AAs were quantified by high-performance liquid chromotography. An interaction of temperature and time significantly affected the DH and AA concentration. As the DH increased, the accumulation of lower MW peptides also increased following SWH (and above 10% DH, the majority of peptides were <1000 Da). Hydrolysis at 300 °C for 40 min generated the highest total AA concentration, especially of lysine (8.894 mg/g WPI). Therefore, WPI was successfully hydrolyzed by subcritical water, and with adjustment of treatment parameters there is reasonable control of the end-products.

  16. Transition to subcritical turbulence in a tokamak plasma

    NASA Astrophysics Data System (ADS)

    van Wyk, F.; Highcock, E. G.; Schekochihin, A. A.; Roach, C. M.; Field, A. R.; Dorland, W.

    2016-12-01

    Tokamak turbulence, driven by the ion-temperature gradient and occurring in the presence of flow shear, is investigated by means of local, ion-scale, electrostatic gyrokinetic simulations (with both kinetic ions and electrons) of the conditions in the outer core of the Mega-Ampere Spherical Tokamak (MAST). A parameter scan in the local values of the ion-temperature gradient and flow shear is performed. It is demonstrated that the experimentally observed state is near the stability threshold and that this stability threshold is nonlinear: sheared turbulence is subcritical, i.e. the system is formally stable to small perturbations, but, given a large enough initial perturbation, it transitions to a turbulent state. A scenario for such a transition is proposed and supported by numerical results: close to threshold, the nonlinear saturated state and the associated anomalous heat transport are dominated by long-lived coherent structures, which drift across the domain, have finite amplitudes, but are not volume filling; as the system is taken away from the threshold into the more unstable regime, the number of these structures increases until they overlap and a more conventional chaotic state emerges. Whereas this appears to represent a new scenario for transition to turbulence in tokamak plasmas, it is reminiscent of the behaviour of other subcritically turbulent systems, e.g. pipe flows and Keplerian magnetorotational accretion flows.

  17. Subcritical water extractor for Mars analog soil analysis.

    PubMed

    Amashukeli, Xenia; Grunthaner, Frank J; Patrick, Steven B; Yung, Pun To

    2008-06-01

    Abstract Technologies that enable rapid and efficient extraction of biomarker compounds from various solid matrices are a critical requirement for the successful implementation of in situ chemical analysis of the martian regolith. Here, we describe a portable subcritical water extractor that mimics multiple organic solvent polarities by tuning the dielectric constant of liquid water through adjustment of temperature and pressure. Soil samples, collected from the Yungay region of the Atacama Desert (martian regolith analogue) in the summer of 2005, were used to test the instrument's performance. The total organic carbon was extracted from the samples at concentrations of 0.2-55.4 parts per million. The extraction data were compared to the total organic carbon content in the bulk soil, which was determined via a standard analytical procedure. The instrument's performance was examined over the temperature range of 25-250 degrees C at a fixed pressure of 20.7 MPa. Under these conditions, water remains in a subcritical fluid state with a dielectric constant varying between approximately 80 (at 25 degrees C) and approximately 30 (at 250 degrees C).

  18. Accelerated subcritical drying of large alkoxide silica gels

    NASA Astrophysics Data System (ADS)

    Wang, Shiho; Kirkbir, Fikret; Chaudhuri, S. R.; Sarkar, Arnab

    1992-12-01

    Fracture during drying has been the key hurdle in fabrication of large monolithic silica glass from alkoxide gels. Although existing literature suggests pore enlargement, aging, chemical additives, supercritical drying and freeze drying as helpful in avoiding fracture during drying, successful accelerated sub-critical drying of large silica monoliths from alkoxide gels has not yet been reported. In the present approach, acid catalyzed sols of TEOS, ethanol and water (pH equals 2) were cast as cylindrical rods in plastic molds of 8.0 and 10.0 cm diameter with volumes of 2000 cc and 3000 cc respectively. The resultant gels were aged for about 7 days and dried in a specially designed chamber under sub-critical conditions of the pore field. We have obtained monolithic dry gels in drying times of 3 - 7 days for sizes of 2000 - 3000 cc. The dry gels have narrow unimodal pore size distributions, with average pore radius of about 20 angstroms as measured by BET. Although capillary stress during drying increases with reduction of pore size, it was found that in this approach it is easier to dry gels of smaller pore size.

  19. Sub-critical insonification of buried elastic shells

    NASA Astrophysics Data System (ADS)

    Veljkovic, Irena; Schmidt, Henrik

    2002-11-01

    In a shallow water environment a high frequency high grazing angle mine-hunting sonar approach is vastly limited by the coverage rate, making the detection and classification of buried objects using subcritical grazing incidence an attractive alternative. One of the central issues in mine countermeasurements regarding the physics of scattering from spherical shells is the isolation and the analysis of the resonant excitations of the system distinguishing the manmade elastic targets from rocks or other clutter. Burial of an elastic target in the seabed results in a variety of modifications to the scattered response caused by different physical mechanisms, geometric constrains, and intrinsic sediment properties. The aim of this research is to identify, analyze, and explain the fundamental effects of the sediment and the proximity of the seabed interface on the scattering of sound from elastic spherical shells insonified using low frequencies at subcritical incident angles. A new, comprehensive understanding of the goats98 experimental data was obtained distinguishing the effects of the acoustics environment from the resonant signature of a buried elastic target. To achieve this and to further investigate the more intricate details of the scattering process, a numerically improved, OASES-3D modeling framework was used. [Work supported by ONR.

  20. NEUTRONIC REACTOR

    DOEpatents

    Fermi, E.; Zinn, W.H.; Anderson, H.L.

    1958-09-16

    Means are presenied for increasing the reproduction ratio of a gaphite- moderated neutronic reactor by diminishing the neutron loss due to absorption or capture by gaseous impurities within the reactor. This means comprised of a fluid-tight casing or envelope completely enclosing the reactor and provided with a valve through which the casing, and thereby the reactor, may be evacuated of atmospheric air.

  1. Evaluation of the /sup 252/Cf-source-driven neutron noise analysis method for measuring the subcriticality of LWR fuel storage casks

    SciTech Connect

    Mihalczo, J.T.

    1987-01-01

    The /sup 252/Cf-source-driven neutron noise analysis method was evaluated to determine if it could be used to measure the subcriticality of storage casks of burnt light water reactor (LWR) fuel submerged in fuel storage pools, fully loaded and as they are being loaded. Measurements of k/sub eff/ would provide the parameter most directly related to the criticality safety of storage cask configurations of LWR fuel and could allow proper credit for fuel burnup without reliance on calculations. This, in turn, could lead to more cost-effective cask designs. Evaluation of the method for this application was based on experiments already completed at a critical experiments facility using arrays of pressurized water reactor (PWR) fuel pins typical of the size of storage cask configurations, the existence of neutron detectors that can function in shipping cask environments, and the ability to construct ionization chambers containing /sup 252/Cf of adequate intensity for these measurements.

  2. Subcritical water extraction of organic matter from sedimentary rocks.

    PubMed

    Luong, Duy; Sephton, Mark A; Watson, Jonathan S

    2015-06-16

    Subcritical water extraction of organic matter containing sedimentary rocks at 300°C and 1500 psi produces extracts comparable to conventional solvent extraction. Subcritical water extraction of previously solvent extracted samples confirms that high molecular weight organic matter (kerogen) degradation is not occurring and that only low molecular weight organic matter (free compounds) are being accessed in analogy to solvent extraction procedures. The sedimentary rocks chosen for extraction span the classic geochemical organic matter types. A type I organic matter-containing sedimentary rock produces n-alkanes and isoprenoidal hydrocarbons at 300°C and 1500 psi that indicate an algal source for the organic matter. Extraction of a rock containing type II organic matter at the same temperature and pressure produces aliphatic hydrocarbons but also aromatic compounds reflecting the increased contributions from terrestrial organic matter in this sample. A type III organic matter-containing sample produces a range of non-polar and polar compounds including polycyclic aromatic hydrocarbons and oxygenated aromatic compounds at 300°C and 1500 psi reflecting a dominantly terrestrial origin for the organic materials. Although extraction at 300°C and 1500 psi produces extracts that are comparable to solvent extraction, lower temperature steps display differences related to organic solubility. The type I organic matter produces no products below 300°C and 1500 psi, reflecting its dominantly aliphatic character, while type II and type III organic matter contribute some polar components to the lower temperature steps, reflecting the chemical heterogeneity of their organic inventory. The separation of polar and non-polar organic compounds by using different temperatures provides the potential for selective extraction that may obviate the need for subsequent preparative chromatography steps. Our results indicate that subcritical water extraction can act as a suitable

  3. Iterative optimal subcritical aerodynamic design code including profile drag

    NASA Technical Reports Server (NTRS)

    Kuhlman, J. M.

    1983-01-01

    A subcritical aerodynamic design computer code has been developed, which uses linearized aerodynamics along with sweep theory and airfoil data to obtain minimum total drag preliminary designs for multiple planform configurations. These optimum designs consist of incidence distributions yielding minimum total drag at design values of Mach number and lift and pitching moment coefficients. Linear lofting is used between airfoil stations. Solutions for isolated transport wings have shown that the solution is unique, and that including profile drag effects decreases tip loading and incidence relative to values obtained for minimum induced drag solutions. Further, including effects of variation of profile drag with Reynolds number can cause appreciable changes in the optimal design for tapered wings. Example solutions are also discussed for multiple planform configurations.

  4. Iterative optimal subcritical aerodynamic design code including profile drag

    NASA Technical Reports Server (NTRS)

    Kuhlman, J. M.

    1983-01-01

    A subcritical aerodynamic design computer code has been developed, which uses linearized aerodynamics along with sweep theory and airfoil data to obtain minimum total drag preliminary designs for multiple planform configurations. These optimum designs consist of incidence distributions yielding minimum total drag at design values of Mach number and lift and pitching moment coefficients. Linear lofting is used between airfoil stations. Solutions for isolated transport wings have shown that the solution is unique, and that including profile drag effects decreases tip loading and incidence relative to values obtained for minimum induced drag solutions. Further, including effects of variation of profile drag with Reynolds number can cause appreciable changes in the optimal design for tapered wings. Example solutions are also discussed for multiple planform configurations.

  5. Transesterification of activated sludge in subcritical solvent mixture.

    PubMed

    Tran-Nguyen, Phuong Lan; Go, Alchris Woo; Ismadji, Suryadi; Ju, Yi-Hsu

    2015-12-01

    Most previous studies reported in literature on biodiesel production from sludge were performed by acid catalyzed transesterification that required long reaction time (about 24h) and high methanol loading. The objective of this study was to investigate the in situ transesterification of sludge in subcritical mixture of methanol and acetic acid. At 250°C and a solvent (85% methanol and 15% acetic acid) to sludge ratio of 5 (mLg(-1)), a FAME yield of 30.11% can be achieved in 30min, compared to the yield of 35% obtained by the acid-catalyzed (4% H2SO4) transesterification which required 24h at 55°C and a methanol to sludge ratio of 25 (mLg(-1)). The method developed in this study avoided using mineral acid, significantly reduced reaction time and methanol loading to achieve comparable FAME yield. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Glycolipid class profiling by packed-column subcritical fluid chromatography.

    PubMed

    Deschamps, Frantz S; Lesellier, Eric; Bleton, Jean; Baillet, Arlette; Tchapla, Alain; Chaminade, Pierre

    2004-06-18

    The potential of packed-column subcritical fluid chromatography (SubFC) for the separation of lipid classes has been assessed in this study. Three polar stationary phases were checked: silica, diol, and poly(vinyl alcohol). Carbon dioxide (CO2) with methanol as modifier was used as mobile phase and detection performed by evaporative light scattering detection. The influence of methanol content, temperature, and pressure on the chromatographic behavior of sphingolipids and glycolipids were investigated. A complete separation of lipid classes from a crude wheat lipid extract was achieved using a modifier gradient from 10 to 40% methanol in carbon dioxide. Solute selectivity was improved using coupled silica and diol columns in series. Because the variation of eluotropic strength depending on the fluid density changes, a normalized separation factor product (NSP) was used to select the nature, the number and the order of the columns to reach the optimum glycolipid separation.

  7. The physical mechanisms of subcritical collisionless shock-wave formation

    NASA Technical Reports Server (NTRS)

    Mellott, M. M.

    1984-01-01

    The key process in shock wave formation is related to energy dissipation, and the nature of the operative dissipation mechanism determines the basic character of the resulting shock. In the case of collisionless plasmas, the primary problem consists in the identification of the processes which can provide the necessary dissipation in relatively short spatial scale lengths. The present investigation is concerned with the various collisionless dissipation mechanisms which can operate in weak shocks, taking into account the effects of different mechanisms on shock structure. Particular attention is given to a restricted class of quasi-perpendicular low beta low Mach number shocks. Such shocks are traditionally called 'laminar shocks'. Resistive shocks are considered along with subcritical shocks observed with the aid of the ISEE spacecraft.

  8. Survey of aircraft subcritical flight flutter testing methods

    NASA Technical Reports Server (NTRS)

    Rosenbaum, R.

    1974-01-01

    The results of a survey of U. S., British and French subcritical aircraft flight flutter testing methods are presented and evaluation of the applicability of these methods to the testing of the space shuttle are discussed. Ten U. S. aircraft programs covering the large civil transport aircraft and a variety of military aircraft are reviewed. In addition, three major French and British programs are covered by the survey. The significant differences between the U. S., French and British practices in the areas of methods of excitation, data acquisition, transmission and analysis are reviewed. The effect of integrating the digital computer into the flight flutter test program is discussed. Significant saving in analysis and flight test time are shown to result from the use of special digital computer routines and digital filters.

  9. Subcritical transition to turbulence in planar shear flows

    NASA Technical Reports Server (NTRS)

    Orszag, S. A.; Patera, A. T.

    1981-01-01

    The two-dimensional steady and time dependent properties of plane Poiseuille and plane Couette flows are analyzed using iterative techniques and full numerical simulation of the Navier-Stokes equations. It is shown that the finite-amplitude two-dimensional states investigated are strongly unstable to very small three-dimensional perturbations. It is also shown, through full numerical simulation, that this explosive secondary instability can explain the subcritical transitions that occur in real flows. Finally, it is shown that the three-dimensional instability can be analyzed by a linear stability analysis of a two-dimensional flow consisting of the basic parallel flow and a steady (or quasi-steady) finite-amplitude two-dimensional cellular motion.

  10. Gravity-driven soap film dynamics in subcritical regimes

    NASA Astrophysics Data System (ADS)

    Auliel, M. I.; Castro, F.; Sosa, R.; Artana, G.

    2015-10-01

    We undertake the analysis of soap-film dynamics with the classical approach of asymptotic expansions. We focus our analysis in vertical soap film tunnels operating in subcritical regimes with elastic Mach numbers Me=O(10-1) . Considering the associated set of nondimensional numbers that characterize this flow, we show that the flow behaves as a two-dimensional (2D) divergence free flow with variable mass density. When the soap film dynamics agrees with that of a 2D and almost constant mass density flow, the regions where the second invariant of the velocity gradient is non-null correspond to regions where the rate of change of film thickness is non-negligible.

  11. Feedback control of subcritical Turing instability with zero mode.

    PubMed

    Golovin, A A; Kanevsky, Y; Nepomnyashchy, A A

    2009-04-01

    A global feedback control of a system that exhibits a subcritical monotonic instability at a nonzero wave number (short-wave or Turing instability) in the presence of a zero mode is investigated using a Ginzburg-Landau equation coupled to an equation for the zero mode. This system is studied analytically and numerically. It is shown that feedback control, based on measuring the maximum of the pattern amplitude over the domain, can stabilize the system and lead to the formation of localized unipulse stationary states or traveling solitary waves. It is found that the unipulse traveling structures result from an instability of the stationary unipulse structures when one of the parameters characterizing the coupling between the periodic pattern and the zero mode exceeds a critical value that is determined by the zero mode damping coefficient.

  12. Subcritical Noise Measurements with a Nickel-Reflected Plutonium Sphere

    SciTech Connect

    Jesson D. Hutchinson; John D. Bess

    2009-11-01

    Subcritical measurements were conducted with an a-phase plutonium sphere reflected by nickel hemishells using the 252Cf Source-Driven Noise Analysis (CSDNA) method to provide criticality safety benchmark data. Measured configurations included a bare plutonium sphere as well as the plutonium sphere reflected by the following nickel thicknesses: 1.27, 2.54, 3.81, 5.08, and 7.62 cm. A certain ratio of spectral quantities was measured for each configuration which varies linearly with the keff of the system. In addition, two types of Monte Carlo calculations were employed: a modified version of MCNP to calculate the ratio of spectral quantities and a KCODE calculation. From the measured and computed quantities the multiplication of each configuration can be approximated. A comprehensive uncertainty analysis was then performed that includes uncertainties in the geometry and materials present in the system in addition to the uncertainties in the method and nuclear data.

  13. Subcritical Water Extraction of Amino Acids from Atacama Desert Soils

    NASA Technical Reports Server (NTRS)

    Amashukeli, Xenia; Pelletier, Christine C.; Kirby, James P.; Grunthaner, Frank J.

    2007-01-01

    Amino acids are considered organic molecular indicators in the search for extant and extinct life in the Solar System. Extraction of these molecules from a particulate solid matrix, such as Martian regolith, will be critical to their in situ detection and analysis. The goals of this study were to optimize a laboratory amino acid extraction protocol by quantitatively measuring the yields of extracted amino acids as a function of liquid water temperature and sample extraction time and to compare the results to the standard HCl vapor- phase hydrolysis yields for the same soil samples. Soil samples from the Yungay region of the Atacama Desert ( Martian regolith analog) were collected during a field study in the summer of 2005. The amino acids ( alanine, aspartic acid, glutamic acid, glycine, serine, and valine) chosen for analysis were present in the samples at concentrations of 1 - 70 parts- per- billion. Subcritical water extraction efficiency was examined over the temperature range of 30 - 325 degrees C, at pressures of 17.2 or 20.0 MPa, and for water- sample contact equilibration times of 0 - 30 min. None of the amino acids were extracted in detectable amounts at 30 degrees C ( at 17.2 MPa), suggesting that amino acids are too strongly bound by the soil matrix to be extracted at such a low temperature. Between 150 degrees C and 250 degrees C ( at 17.2 MPa), the extraction efficiencies of glycine, alanine, and valine were observed to increase with increasing water temperature, consistent with higher solubility at higher temperatures, perhaps due to the decreasing dielectric constant of water. Amino acids were not detected in extracts collected at 325 degrees C ( at 20.0 MPa), probably due to amino acid decomposition at this temperature. The optimal subcritical water extraction conditions for these amino acids from Atacama Desert soils were achieved at 200 degrees C, 17.2 MPa, and a water- sample contact equilibration time of 10 min.

  14. Studies on the stability of preservatives under subcritical water conditions.

    PubMed

    Kapalavavi, B; Marple, R; Gamsky, C; Yang, Y

    2015-06-01

    The goal of this work was to further validate the subcritical water chromatography (SBWC) methods for separation and analysis of preservatives through the evaluation of analyte stability in subcritical water. In this study, the degradation of preservatives was investigated at temperatures of 100-200°C using two different approaches. First, the peak areas obtained by SBWC at high temperatures were compared with those achieved using the traditional high-performance liquid chromatography (HPLC) at 25°C. In the second approach, several preservatives and water were loaded into a vessel and heated at high temperatures for 30 or 60 min. The heated mixtures were then analysed by GC/MS to determine the stability of preservatives. The t- and F-test on the results of the first approach reveal that the peak areas achieved by HPLC and SBWC are not significantly different at the 95% confidence level, meaning that the preservatives studied are stable during the high-temperature SBWC runs. Although the results of the second approach show approximately 10% degradation of preservatives into mainly p-hydroxybenzoic acid and phenol at 200°C, the preservatives studied are stable at 100 and 150°C. This is in good agreement with the validation results obtained by the first approach. The findings of this work confirm that SBWC methods at temperatures up to 150°C are reliable for separation and analysis of preservatives in cosmetic and other samples. © 2014 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  15. Subcritical-Water Extraction of Organics from Solid Matrices

    NASA Technical Reports Server (NTRS)

    Amashukeli, Xenia; Grunthaner, Frank; Patrick, Steven; Kirby, James; Bickler, Donald; Willis, Peter; Pelletier, Christine; Bryson, Charles

    2009-01-01

    An apparatus for extracting organic compounds from soils, sands, and other solid matrix materials utilizes water at subcritical temperature and pressure as a solvent. The apparatus, called subcritical water extractor (SCWE), is a prototype of subsystems of future instrumentation systems to be used in searching for organic compounds as signs of past or present life on Mars. An aqueous solution generated by an apparatus like this one can be analyzed by any of a variety of established chromatographic or spectroscopic means to detect the dissolved organic compound( s). The apparatus can be used on Earth: indeed, in proof-of-concept experiments, SCWE was used to extract amino acids from soils of the Atacama Desert (Chile), which was chosen because the dryness and other relevant soil conditions there approximate those on Mars. The design of the apparatus is based partly on the fact that the relative permittivity (also known as the dielectric constant) of liquid water varies with temperature and pressure. At a temperature of 30 C and a pressure of 0.1 MPa, the relative permittivity of water is 79.6, due to the strong dipole-dipole electrostatic interactions between individual molecular dipoles. As the temperature increases, increasing thermal energy causes increasing disorientation of molecular dipoles, with a consequent decrease in relative permittivity. For example, water at a temperature of 325 C and pressure of 20 MPa has a relative permittivity of 17.5, which is similar to the relative permittivities of such nonpolar organic solvents as 1-butanol (17.8). In the operation of this apparatus, the temperature and pressure of water are adjusted so that the water can be used in place of commonly used organic solvents to extract compounds that have dissimilar physical and chemical properties.

  16. Subcritical crack growth under mode I, II, and III loading for Coconino sandstone

    NASA Astrophysics Data System (ADS)

    Ko, Tae Young

    In systems subjected to long-term loading, subcritical crack growth is the principal mechanism causing the time-dependent deformation and failure of rocks. Subcritical crack growth is environmentally-assisted crack growth, which can allow cracks to grow over a long period of time at stresses far smaller than their failure strength and at tectonic strain rates. The characteristics of subcritical crack growth can be described by a relationship between the stress intensity factor and the crack velocity. This study presents the results of studies conducted to validate the constant stress-rate test for determining subcritical crack growth parameters in Coconino sandstone, compared with the conventional testing method, the double torsion test. The results of the constant stress-rate test are in good agreement with the results of double torsion test. More importantly, the stress-rate tests can determine the parameter A with a much smaller standard deviation than the double torsion test. Thus the constant stress-rate test seems to be both a valid and preferred test method for determining the subcritical crack growth parameters in rocks. We investigated statistical aspects of the constant stress-rate test. The effects of the number of tests conducted on the subcritical crack growth parameters were examined and minimum specimen numbers were determined. The mean and standard deviation of the subcritical crack growth parameters were obtained by randomly selecting subsets from the original strength data. In addition, the distribution form of the subcritical crack growth parameters and the relation between the parameter n and A were determined. We extended the constant stress-rate test technique to modes II and III subcritical crack growth in rocks. The experimental results of the modes I, II and III tests show that the values of the subcritical crack growth parameters are similar to each other. The subcritical crack growth parameter n value for Coconino sandstone has the range

  17. Emissions of brominated compounds and polycyclic aromatic hydrocarbons during pyrolysis of E-waste debrominated in subcritical water.

    PubMed

    Soler, Aurora; Conesa, Juan A; Ortuño, Nuria

    2017-11-01

    Degradation of brominated flame retardants present in printed circuit boards (PCBs) was tested using subcritical water in a high pressure reactor. Debromination experiments were carried out in a batch stirred reactor at three different temperatures (225 °C, 250 °C and 275 °C) keeping a solid to liquid (S/L) ratio of PCB:water = 1:5 during 180 min. Results indicated that debromination efficiency was increased with temperature (18.5-63.6% of bromine present in the original PCB was removed). Thermal decomposition of the debrominated materials was studied and compared with that of the original PCB. Thermogravimetric analyses were performed at three different heating rates (5, 10 and 20 K min(-1)), studying both the pyrolysis (inert atmosphere) and combustion (in air). Pyrolysis runs of the debrominated materials were also performed in a quartz horizontal laboratory furnace at 850 °C, in order to study the emission of pollutants. More than 99% of the bromine was emitted in the form of HBr and Br2. Emissions of polycyclic aromatic hydrocarbons (PAHs) and bromophenols (BrPhs) decreased with the increase in the treatment temperature; naphthalene (10,800-18,300 mg kg(-1) original sample) and monobrominated phenols (12.8-16.9 mg kg(-1) original sample) were the most abundant compounds. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. BOILING REACTORS

    DOEpatents

    Untermyer, S.

    1962-04-10

    A boiling reactor having a reactivity which is reduced by an increase in the volume of vaporized coolant therein is described. In this system unvaporized liquid coolant is extracted from the reactor, heat is extracted therefrom, and it is returned to the reactor as sub-cooled liquid coolant. This reduces a portion of the coolant which includes vaporized coolant within the core assembly thereby enhancing the power output of the assembly and rendering the reactor substantially self-regulating. (AEC)

  19. NEUTRONIC REACTOR

    DOEpatents

    Daniels, F.

    1959-10-27

    A reactor in which at least a portion of the moderator is in the form of movable refractory balls is described. In addition to their moderating capacity, these balls may serve as carriers for fissionable material or fertile material, or may serve in a coolant capacity to remove heat from the reactor. A pneumatic system is used to circulate the balls through the reactor.

  20. NUCLEAR REACTOR

    DOEpatents

    Treshow, M.

    1961-09-01

    A boiling-water nuclear reactor is described wherein control is effected by varying the moderator-to-fuel ratio in the reactor core. This is accomplished by providing control tubes containing a liquid control moderator in the reactor core and providing means for varying the amount of control moderatcr within the control tubes.

  1. Subcritical water extraction of antioxidant phenolic compounds from XiLan olive fruit dreg.

    PubMed

    Yu, Xue-Mei; Zhu, Ping; Zhong, Qiu-Ping; Li, Meng-Ying; Ma, Han-Ruo

    2015-08-01

    Olive fruit dreg (OFD), waste from olive softdrink processing, has caused disposal problems. Nevertheless, OFD is a good source of functional ingredients, such as phenolic compounds. This study investigated the extraction conditions of phenolic compounds from OFD by using subcritical water (SCW) extraction method, antioxidant activity of SCW extracts, and components of phenolic compounds by LC-MS. SCW extraction experiments were performed in a batch stainless steel reactor at temperatures ranging from 100 to 180 °C at residence time of 5 to 60 min, and at solid-to-liquid ratio of 1:20 to 1:60. Higher recoveries of phenolic compounds [37.52 ± 0.87 mg gallic acid equivalents (GAE)/g, dry weight (DW)] were obtained at 160 °C, solid-to-liquid ratio of 1:50, and extract time of 30 min than at 2 h extraction with methanol (1.21 ± 0.16 mg GAE/g DW), ethanol (0.24 ± 0.07 mg GAE/g DW), and acetone (0.34 ± 0.01 mg GAE/g DW). The antioxidant activities of the SCW extracts were significantly stronger than those in methanol extracts at the same concentration of total phenolic contents. LC-MS analysis results indicated that SCW extracts contained higher amounts of phenolic compounds, such as chlorogenic acid, homovanillic acid, gallic acid, hydroxytyrosol, quercetin, and syringic acid. SCW at 160 °C, 30 min, and solid-to-liquid ratio of 1:50 may be a good substitute of organic solvents, such as methanol, ethanol, and acetone to recover phenolic compounds from OFD.

  2. SELECTIVE EXTRACTION OF OXYGENATES FROM SAVORY AND PEPPERMINT USING SUBCRITICAL WATER. (R825394)

    EPA Science Inventory

    The yields of oxygenated and non-oxygenated flavour and fragrance compounds from savory (Satureja hortensis) and peppermint (Mentha piperita) were compared using subcritical water extraction, supercritical carbon dioxide extraction (SFE) and hydrodistillation. Extraction rates wi...

  3. Supercritical (and Subcritical) Fluid Behavior and Modeling: Drops, Streams, Shear and Mixing Layers, Jets and Sprays

    NASA Technical Reports Server (NTRS)

    Bellan, J.

    1999-01-01

    A critical review of recent investigations in the real of supercritical (and subcritical) fluid behavior is presented with the goal of obtaining a perspective on the peculiarities of high pressure observations.

  4. Subcritical propagation of an oil-filled penny-shaped crack during kerogen-oil conversion

    NASA Astrophysics Data System (ADS)

    Fan, Z. Q.; Jin, Z.-H.; Johnson, S. E.

    2010-09-01

    We conduct a parametric study on the subcritical propagation of an oil-filled, penny-shaped microcrack induced by the pressure increase caused by transformation of kerogen to oil. The excess oil pressure on the crack surfaces, and the subcritical crack propagation distance and duration, are obtained using a coupled model of fracture mechanics and kerogen-oil transformation kinetics. The numerical results show that the excess oil pressure and crack propagation distance/duration are significantly influenced by the temperature and elastic/fracture properties of the source rock, and the initial kerogen particle size. The subcritical propagation behaviour is relatively insensitive to the volume expansion rate associated with the conversion of kerogen to oil. Because the subcritical crack propagation rate is much faster than the kerogen-oil conversion rate, the crack propagation duration is primarily determined by the transformation kinetics.

  5. SELECTIVE EXTRACTION OF OXYGENATES FROM SAVORY AND PEPPERMINT USING SUBCRITICAL WATER. (R825394)

    EPA Science Inventory

    The yields of oxygenated and non-oxygenated flavour and fragrance compounds from savory (Satureja hortensis) and peppermint (Mentha piperita) were compared using subcritical water extraction, supercritical carbon dioxide extraction (SFE) and hydrodistillation. Extraction rates wi...

  6. CONVECTION REACTOR

    DOEpatents

    Hammond, R.P.; King, L.D.P.

    1960-03-22

    An homogeneous nuclear power reactor utilizing convection circulation of the liquid fuel is proposed. The reactor has an internal heat exchanger looated in the same pressure vessel as the critical assembly, thereby eliminating necessity for handling the hot liquid fuel outside the reactor pressure vessel during normal operation. The liquid fuel used in this reactor eliminates the necessity for extensive radiolytic gas rocombination apparatus, and the reactor is resiliently pressurized and, without any movable mechanical apparatus, automatically regulates itself to the condition of criticality during moderate variations in temperature snd pressure and shuts itself down as the pressure exceeds a predetermined safe operating value.

  7. Research reactors

    SciTech Connect

    Tonneson, L.C.; Fox, G.J.

    1996-04-01

    There are currently 284 research reactors in operation, and 12 under construction around the world. Of the operating reactors, nearly two-thirds are used exclusively for research, and the rest for a variety of purposes, including training, testing, and critical assembly. For more than 50 years, research reactor programs have contributed greatly to the scientific and educational communities. Today, six of the world`s research reactors are being shut down, three of which are in the USA. With government budget constraints and the growing proliferation concerns surrounding the use of highly enriched uranium in some of these reactors, the future of nuclear research could be impacted.

  8. Space reactor assessment and validation study

    NASA Technical Reports Server (NTRS)

    Gedeon, Stephen; Morey, Dennis

    1987-01-01

    The present difficulties experienced by the United States in launching payloads into space has suggested a number of problems which are associated with the handling of hazardous materials in spacecraft. The question has arisen as to the safety of launching highly radioactive material such as plutonium-238, related to the possibility of its dispersion into the atmosphere during a launch vehicle explosion. An alternative is the use of a small nuclear reactor which is not started until it is in space and contains little or no radioactivity at launch. A first order assessment of six small reactor concepts with power levels up to 100 MWe was performed. Both the nuclear feasibility of these concepts to operate at their rated power levels between 7 and 10 years and the capability of these concepts to remain subcritical both before and during launch and also in the case of water immersion during a potential launch failure or abort were investigated.

  9. Space reactor assessment and validation study

    NASA Astrophysics Data System (ADS)

    Gedeon, Stephen; Morey, Dennis

    The present difficulties experienced by the United States in launching payloads into space has suggested a number of problems which are associated with the handling of hazardous materials in spacecraft. The question has arisen as to the safety of launching highly radioactive material such as plutonium-238, related to the possibility of its dispersion into the atmosphere during a launch vehicle explosion. An alternative is the use of a small nuclear reactor which is not started until it is in space and contains little or no radioactivity at launch. A first order assessment of six small reactor concepts with power levels up to 100 MWe was performed. Both the nuclear feasibility of these concepts to operate at their rated power levels between 7 and 10 years and the capability of these concepts to remain subcritical both before and during launch and also in the case of water immersion during a potential launch failure or abort were investigated.

  10. Space reactor assessment and validation study

    NASA Technical Reports Server (NTRS)

    Gedeon, Stephen; Morey, Dennis

    1987-01-01

    The present difficulties experienced by the United States in launching payloads into space has suggested a number of problems which are associated with the handling of hazardous materials in spacecraft. The question has arisen as to the safety of launching highly radioactive material such as plutonium-238, related to the possibility of its dispersion into the atmosphere during a launch vehicle explosion. An alternative is the use of a small nuclear reactor which is not started until it is in space and contains little or no radioactivity at launch. A first order assessment of six small reactor concepts with power levels up to 100 MWe was performed. Both the nuclear feasibility of these concepts to operate at their rated power levels between 7 and 10 years and the capability of these concepts to remain subcritical both before and during launch and also in the case of water immersion during a potential launch failure or abort were investigated.

  11. Subcritical Kelvin-Helmholtz instability in a Hele-Shaw cell.

    PubMed

    Meignin, L; Gondret, P; Ruyer-Quil, C; Rabaud, M

    2003-06-13

    We investigate experimentally the subcritical behavior of the Kelvin-Helmholtz instability for a gas-liquid shearing flow in a Hele-Shaw cell. The subcritical curve separating the solutions of a stable plane interface and a fully saturated nonlinear wave train is determined. Experimental results are fitted by a fifth order complex Ginzburg-Landau equation whose linear coefficients are compared to theoretical ones.

  12. Review of the state of criticality of the Three Mile Island Unit 2 core and reactor vessel

    SciTech Connect

    Stratton, W.R. )

    1987-04-15

    The events during the early hours of the Three Mile Island Unit 2 (TMI-2) accident on March 28, 1979 caused the fuel in the reactor core to crumble or disintegrate, and then subside into a rubble structure more compact that its normal configuration. The present height of the core is about seven feet, five feet less than its normal configuration of 12 feet. With the same boron content and some or all of the control rod and burnable poison rod material as the normal core configuration, the collapsed structure is calculated to be more reactive. However, the reactor is assuredly subcritical at present because of the extraordinarily high boron concentration maintained in the coolant water. Four additional and different physical models are discussed briefly in the report to illustrate the margin of subcriticality, to provide a better estimate of the neutron multiplication factor, and to provide some understanding of the criticality effects of the important parameters. Two different finite, cylindrical models of a collapsed core are also presented in this report. The conclusion of this review is that the reactor is now very far subcritical with a boron concentration of 4350 ppM or more, and no conceivable rearrangement of fuel can create a critical state. Careful administrative control to maintain the boron concentration of the reactor coolant close to 5000 ppM, and controls to rigorously exclude addition of unborated water to the primary system, provide additional assurance that subcriticality will be maintained. The immediate corollary is that the defueling of the reactor vessel can proceed as planned, with complete confidence that such operations will remain subcritical. 20 refs.

  13. Subcritical Water Hydrolysis of Peptides: Amino Acid Side-Chain Modifications

    NASA Astrophysics Data System (ADS)

    Powell, Thomas; Bowra, Steve; Cooper, Helen J.

    2017-09-01

    Previously we have shown that subcritical water may be used as an alternative to enzymatic digestion in the proteolysis of proteins for bottom-up proteomics. Subcritical water hydrolysis of proteins was shown to result in protein sequence coverages greater than or equal to that obtained following digestion with trypsin; however, the percentage of peptide spectral matches for the samples treated with trypsin were consistently greater than for those treated with subcritical water. This observation suggests that in addition to cleavage of the peptide bond, subcritical water treatment results in other hydrolysis products, possibly due to modifications of amino acid side chains. Here, a model peptide comprising all common amino acid residues (VQSIKCADFLHYMENPTWGR) and two further model peptides (VCFQYMDRGDR and VQSIKADFLHYENPTWGR) were treated with subcritical water with the aim of probing any induced amino acid side-chain modifications. The hydrolysis products were analyzed by direct infusion electrospray tandem mass spectrometry, either collision-induced dissociation or electron transfer dissociation, and liquid chromatography collision-induced dissociation tandem mass spectrometry. The results show preferential oxidation of cysteine to sulfinic and sulfonic acid, and oxidation of methionine. In the absence of cysteine and methionine, oxidation of tryptophan was observed. In addition, water loss from aspartic acid and C-terminal amidation were observed in harsher subcritical water conditions. [Figure not available: see fulltext.

  14. Recycling high-performance carbon fiber reinforced polymer composites using sub-critical and supercritical water

    NASA Astrophysics Data System (ADS)

    Knight, Chase C.

    complete recycling loop. After showing the feasibility and power of this technology, the third phase of the study was focused on the fundamentals on the degradation of highly cross-linked polymer network by sub- and near-critical water. A methodology framework was established to study the apparent kinetics of the degradation of epoxy in sub-critical water. The reaction rate was modeled by a phenomenological rate model of nth order, and the rate constant was modeled by taking into account of the contributions of important physical parameters, e.g., pressure, temperature and dielectric constants. The applicability of the established model to describe the degradation kinetics was confirmed by the validation runs. This model is a suitable starting point to gain the knowledge required for eventual industrial process design. The final phase of this research consisted of a preliminary foray into investigating the economic feasibility of this technology. A process model was designed around a reactor which was sized according to considerations of industrial relevancy. The simulation of the process was done using Aspen Plus, powerful and comprehensive process simulation software. Economic analysis of this pseudo-realistic process suggested that such technology was economically viable and competitive comparing to other recycling technologies. In summary, this dissertation work represents the first comprehensive investigation on recycling aerospace-grade, multilayer woven fabric composites using supercritical and sub-critical water. The fundamental knowledge gained and process technology developed during this research is anticipated to play an important role in advancing this recycling technology toward potential adoption and implementation by the recycling and composite industry.

  15. Retention behavior of phenols, anilines, and alkylbenzenes in liquid chromatographic separations using subcritical water as the mobile phase.

    PubMed

    Yang, Y; Jones, A D; Eaton, C D

    1999-09-01

    The unique characteristic of subcritical water is its widely tunable physical properties. For example, the polarity (measured by dielectric constant) of water is significantly decreased by raising water temperature. At temperatures of 200-250 °C (under moderate pressure to keep water in the liquid state), the polarity of pure water is similar to that of pure methanol or acetonitrile at ambient conditions. Therefore, pure subcritical water may be able to serve as the mobile phase for reversed-phase separations. To investigate the retention behavior in subcritical water separation, the retention factors of BTEX (benzene, toluene, ethylbenzene, and m-xylene), phenol, aniline, and their derivatives have been determined using subcritical water, methanol/water, and acetonitrile/water systems. Subcritical water separations were also performed using alumina, silica-bonded C18, and poly(styrene-divinylbenzene) columns to study the influence of the stationary phase on analyte retention under subcritical water conditions.

  16. Pati-Salam version of subcritical hybrid inflation

    NASA Astrophysics Data System (ADS)

    Bryant, B. Charles; Raby, Stuart

    2016-05-01

    In this paper we present a model of subcritical hybrid inflation with a Pati-Salam (PS) symmetry group. Both the inflaton and waterfall fields contribute to the necessary e -foldings of inflation, while only the waterfall field spontaneously breaks PS hence monopoles produced during inflation are diluted during the inflationary epoch. The model is able to produce a tensor-to-scalar ratio, r <0.09 consistent with the latest BICEP2/Keck and Planck data, as well as scalar density perturbations and spectral index, ns, consistent with Planck data. For particular values of the parameters, we find r =0.084 and ns=0.0963 . The energy density during inflation is directly related to the PS breaking scale, vPS. The model also incorporates a Z4R symmetry which can resolve the μ problem and suppress dimension 5 operators for proton decay, leaving over an exact R parity. Finally the model allows for a complete three-family extension with a D4 family symmetry which reproduces low energy precision electroweak and LHC data.

  17. Evaporation of LOX under supercritical and subcritical conditions

    NASA Technical Reports Server (NTRS)

    Yang, A. S.; Hsieh, W. H.; Kuo, K. K.; Brown, J. J.

    1993-01-01

    The evaporation of LOX under supercritical and subcritical conditions was studied experimentally and theoretically. In experiments, the evaporation rate and surface temperature were measured for LOX strand vaporizing in helium environments at pressures ranging from 5 to 68 atmospheres. Gas sampling and chromatography analysis were also employed to profile the gas composition above the LOX surface for the purpose of model validation. A comprehensive theoretical model was formulated and solved numerically to simulate the evaporation process of LOX at high pressures. The model was based on the conservation equations of mass, momentum, energy, and species concentrations for a multicomponent system, with consideration of gravitational body force, solubility of ambient gases in liquid, and variable thermophysical properties. Good agreement between predictions and measured oxygen mole fraction profiles was obtained. The effect of pressure on the distribution of the Lewis number, as well as the effect of variable diffusion coefficient, were further examined to elucidate the high-pressure transport behavior exhibited in the LOX vaporization process.

  18. Catalytic upgrading of duckweed biocrude in subcritical water.

    PubMed

    Zhang, Caicai; Duan, Peigao; Xu, Yuping; Wang, Bing; Wang, Feng; Zhang, Lei

    2014-08-01

    Herein, a duckweed biocrude produced from the hydrothermal liquefaction of Lemna minor was treated in subcritical water with added H₂. Effects of several different commercially available materials such as Ru/C, Pd/C, Pt/C, Pt/γ-Al₂O₃, Pt/C-sulfide, Rh/γ-Al₂O₃, activated carbon, MoS₂, Mo₂C, Co-Mo/γ-Al₂O₃, and zeolite on the yields of product fractions and the deoxygenation, denitrogenation, and desulfurization of biocrude at 350°C were examined, respectively. All the materials showed catalytic activity for deoxygenation and desulfurization of the biocrude and only Ru/C showed activity for denitrogenation. Of those catalysts examined, Pt/C showed the best performance for deoxygenation. Among all the upgraded oils, the oil produced with Ru/C shows the lowest sulfur, the highest hydrocarbon content (25.6%), the highest energy recovery (85.5%), and the highest higher heating value (42.6 MJ/kg). The gaseous products were mainly unreacted H₂, CH₄, CO₂, and C₂H6. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Degradation of benzoic acid and its derivatives in subcritical water.

    PubMed

    Lindquist, Edward; Yang, Yu

    2011-04-15

    In this research, the stability of benzoic acid and three of its derivatives (anthranilic acid, salicylic acid, and syringic acid) under subcritical water conditions was investigated. The stability studies were carried out at temperatures ranging from 50 to 350°C with heating times of 10-630 min. The degradation of the benzoic acid derivatives increased with rising temperature and the acids became less stable with longer heating time. The three benzoic acid derivatives showed very mild degradation at 150°C. Severe degradation of benzoic acid derivatives was observed at 200°C while their complete degradation occurred at 250°C. However, benzoic acid remained stable at temperatures up to 300°C. The degradation products of benzoic acid and the three derivatives were identified and quantified by HPLC and confirmed by GC/MS. Anthranilic acid, salicylic acid, syringic acid, and benzoic acid in high-temperature water underwent decarboxylation to form aniline, phenol, syringol, and benzene, respectively. Copyright © 2010 Elsevier B.V. All rights reserved.

  20. The Chain-Length Distribution in Subcritical Systems

    SciTech Connect

    Nolen, Steven Douglas

    2000-06-01

    The individual fission chains that appear in any neutron multiplying system provide a means, via neutron noise analysis, to unlock a wealth of information regarding the nature of the system. This work begins by determining the probability density distributions for fission chain lengths in zero-dimensional systems over a range of prompt neutron multiplication constant (K) values. This section is followed by showing how the integral representation of the chain-length distribution can be used to obtain an estimate of the system's subcritical prompt multiplication (MP). The lifetime of the chains is then used to provide a basis for determining whether a neutron noise analysis will be successful in assessing the neutron multiplication constant, k, of the system in the presence of a strong intrinsic source. A Monte Carlo transport code, MC++, is used to model the evolution of the individual fission chains and to determine how they are influenced by spatial effects. The dissertation concludes by demonstrating how experimental validation of certain global system parameters by neutron noise analysis may be precluded in situations in which the system K is relatively low and in which realistic detector efficiencies are simulated.

  1. Subcritical solvent extraction of anthocyanins from dried red grape pomace.

    PubMed

    Monrad, Jeana K; Howard, Luke R; King, Jerry W; Srinivas, Keerthi; Mauromoustakos, Andy

    2010-03-10

    Accelerated solvent extraction (ASE) was used to optimize and determine the effectiveness of an alternative, environmentally friendly extraction procedure using subcritical solvents to recover anthocyanins from freeze-dried, ground Sunbelt red grape pomace. Anthocyanins were extracted from pomace using the following ASE variables: pressure (6.8 MPa), one extraction cycle, and temperature (40, 60, 80, 100, 120, and 140 degrees C). Conventional solvent extraction with methanol/water/formic acid (60:37:3 v/v/v) was compared to four hydroethanolic solvents (10, 30, 50, and 70% ethanol in water, v/v). Anthocyanins in the extracts were identified and quantified by HPLC-MS and HPLC. There was an insignificant interaction between solvent and temperature (p = 0.0663). Solvents containing 70 and 50% ethanol in water extracted more total anthocyanins (463 and 455 mg/100 g of DW, respectively) than other solvents. The total amounts of anthocyanins extracted at 100 degrees C (450 mg/100 g of DW), 80 degrees C (436 mg/100 g of DW), and 120 degrees C (411 mg/100 g of DW) were higher than at the other temperatures. Solvents containing 70 and 50% ethanol in water extracted similar amounts of anthocyanins as conventional extraction solvent.

  2. Evaporation of LOX under supercritical and subcritical conditions

    NASA Technical Reports Server (NTRS)

    Yang, A. S.; Hsieh, W. H.; Kuo, K. K.; Brown, J. J.

    1993-01-01

    The evaporation of LOX under supercritical and subcritical conditions was studied experimentally and theoretically. In experiments, the evaporation rate and surface temperature were measured for LOX strand vaporizing in helium environments at pressures ranging from 5 to 68 atmospheres. Gas sampling and chromatography analysis were also employed to profile the gas composition above the LOX surface for the purpose of model validation. A comprehensive theoretical model was formulated and solved numerically to simulate the evaporation process of LOX at high pressures. The model was based on the conservation equations of mass, momentum, energy, and species concentrations for a multicomponent system, with consideration of gravitational body force, solubility of ambient gases in liquid, and variable thermophysical properties. Good agreement between predictions and measured oxygen mole fraction profiles was obtained. The effect of pressure on the distribution of the Lewis number, as well as the effect of variable diffusion coefficient, were further examined to elucidate the high-pressure transport behavior exhibited in the LOX vaporization process.

  3. Kinetic behavior of liquefaction of Japanese beech in subcritical phenol.

    PubMed

    Mishra, Gaurav; Saka, Shiro

    2011-12-01

    Non-catalytic liquefaction of Japanese beech (Fagus crenata) wood in subcritical phenol was investigated using a batch-type reaction vessel. After samples were treated at 160 °C/0.9 MPa-350 °C/4.2 MPa for 3-30 min, they were fractionated into a phenol-soluble portion and phenol-insoluble residues. These residues were then analyzed for their chemical composition. Based on the obtained data, the kinetics for liquefaction was modeled using first-order reaction rate law. Subsequently, the liquefaction rate constants of the major cell wall components including cellulose, hemicellulose, and lignin were determined. The different kinetic mechanisms were found to exist for lignin and cellulose at two different temperature ranges, lower 160-290 °C and higher 310-350 °C, whereas for hemicellulose, it was only liquefied in the lower temperature range. Thus, the liquefaction behaviors of these major cell wall components highlighted hemicellulose to be the most susceptible to liquefaction, followed by lignin and cellulose.

  4. Advances in Subcritical Hydro-/Solvothermal Processing of Graphene Materials.

    PubMed

    Sasikala, Suchithra Padmajan; Poulin, Philippe; Aymonier, Cyril

    2017-02-28

    Many promising graphene-based materials are kept away from mainstream applications due to problems of scalability and environmental concerns in their processing. Hydro-/solvothermal techniques overwhelmingly satisfy both the aforementioned criteria, and have matured as alternatives to wet-chemical methods with advances made over the past few decades. The insolubility of graphene in many solvents poses considerable difficulties in their processing. In this context hydro-/solvothermal techniques present an ideal opportunity for processing of graphenic materials with their versatility in manipulating the physical and thermodynamic properties of the solvent. The flexibility in hydro-/solvothermal techniques for manipulation of solvent composition, temperature and pressure provides numerous handles to manipulate graphene-based materials during synthesis. This review provides a comprehensive look at the subcritical hydro-/solvothermal synthesis of graphene-based functional materials and their applications. Several key synthetic strategies governing the morphology and properties of the products such as temperature, pressure, and solvent effects are elaborated. Advances in the synthesis, doping, and functionalization of graphene in hydro-/solvothermal media are highlighted together with our perspectives in the field.

  5. Effective Subcritical Butane Extraction of Bifenthrin Residue in Black Tea.

    PubMed

    Zhang, Yating; Gu, Lingbiao; Wang, Fei; Kong, Lingjun; Qin, Guangyong

    2017-03-30

    As a natural and healthy beverage, tea is widely enjoyed; however, the pesticide residues in tea leaves affect the quality and food safety. To develop a highly selective and efficient method for the facile removal of pesticide residues, the subcritical butane extraction (SBE) technique was employed, and three variables involving temperature, time and extraction cycles were studied. The optimum SBE conditions were found to be as follows: extraction temperature 45 °C, extraction time 30 min, number of extraction cycles 1, and in such a condition that the extraction efficiency reached as high as 92%. Further, the catechins, theanine, caffeine and aroma components, which determine the quality of the tea, fluctuated after SBE treatment. Compared with the uncrushed leaves, pesticide residues can more easily be removed from crushed leaves, and the practical extraction efficiency was 97%. These results indicate that SBE is a useful method to efficiently remove the bifenthrin, and as appearance is not relevant in the production process, tea leaves should first be crushed and then extracted in order that residual pesticides are thoroughly removed.

  6. Enhanced Capabilities for Subcritical Experiments (ECSE) Risk Management Plan

    SciTech Connect

    Urban, Mary Elizabeth

    2016-05-02

    Risk is a factor, element, constraint, or course of action that introduces an uncertainty of outcome that could impact project objectives. Risk is an inherent part of all activities, whether the activity is simple and small, or large and complex. Risk management is a process that identifies, evaluates, handles, and monitors risks that have the potential to affect project success. The risk management process spans the entire project, from its initiation to its successful completion and closeout, including both technical and programmatic (non-technical) risks. This Risk Management Plan (RMP) defines the process to be used for identifying, evaluating, handling, and monitoring risks as part of the overall management of the Enhanced Capabilities for Subcritical Experiments (ECSE) ‘Project’. Given the changing nature of the project environment, risk management is essentially an ongoing and iterative process, which applies the best efforts of a knowledgeable project staff to a suite of focused and prioritized concerns. The risk management process itself must be continually applied throughout the project life cycle. This document was prepared in accordance with DOE O 413.3B, Program and Project Management for the Acquisition of Capital Assets, its associated guide for risk management DOE G 413.3-7, Risk Management Guide, and LANL ADPM AP-350-204, Risk and Opportunity Management.

  7. Subcritical Transition to Turbulence in Couette-Poiseuille flow

    NASA Astrophysics Data System (ADS)

    Wesfreid, Jose Eduardo; Klotz, Lukasz

    2016-11-01

    We study the subcritical transition to turbulence in the plane Couette-Poiseuille shear flow with zero mean advection velocity. Our experimental configuration consists on one moving wall of the test section (the second one remains stationary), which acts like a driving force for the flow, imposing linear streamwise velocity profile (Couette) and adverse pressure gradient in the streamwise direction (Poiseuille) at the same time. This flow, which had only been studied theoretically up to now, is always linearly stable. The transition to turbulence is forced by a very well controlled finite-size perturbation by injection, into the test section, of a water jet during a very short time. Using PIV technique, we characterized quantitatively the initial development of the triggered turbulent spot and compared its energy evolution with the theoretical predictions of the transient growth theory. In addition, we show results concerning the importance of nonlinearities, when waviness of streaks in streamwise direction induced self-sustained process in the turbulent spot. We also measured precisely the large-scale flow which is generated around the turbulent spot and studied its strength as a function of the Reynolds number.

  8. Rapid column heating method for subcritical water chromatography.

    PubMed

    Fogwill, Michael O; Thurbide, Kevin B

    2007-01-19

    A novel resistive heating method is presented for subcritical water chromatography (SWC) that provides higher column heating rates than those conventionally obtained from temperature-programmed gas chromatography (GC) convection ovens. Since the polarity of water reduces dramatically with increasing temperature, SWC employs column heating to achieve gradient elution. As such, the rate at which the mobile phase is heated directly impacts the magnitude of such gradients applied in SWC. Data from the current study demonstrate that the maximum column heating rate attainable in a typical SWC apparatus (i.e. using a GC convection oven) is around 10 degrees C/min, even at instrument oven settings of over three times this value. Conversely, by wrapping the separation column with ceramic insulation and a resistively heated wire, the column heating rates are increased five-fold. As a result, elution times can be greatly decreased in SWC employing gradients. Separations of standard alcohol test mixtures demonstrate that the retention time of the latest eluting component decreases by 35 to 50% using the prototype method. Additionally, solute retention times in this mode deviate by less than 1% RSD over several trials, which compares very well to those obtained using a conventional GC convection oven. Results suggest that the developed method can be a useful alternative heating technique in SWC.

  9. Neutronics and safety analysis of pellet bed reactor for nuclear thermal propulsion

    SciTech Connect

    Morley, N.J.; El-Genk, M.S. )

    1993-01-15

    The Pellet Bed Reactor for Nuclear Thermal Propulsion is modeled using the TWODANT discrete ordinance code to determine a reactor point design based on the selection of a fuel fraction in and a diameter of the pellets, dimensions of the reactor core, maximum fuel temperature, and sub-criticality during a water flooding accident. A total excess reactivity of approximately $1.25 (or k[sub eff] of 1.01), an order of magnitude higher than that estimated at BOM for 15 hours of full power, steady-state operation of the PeBR, is considered. Besides calculating the dimensions of the reactor core to satisfy the excess reactivity at BOM, the results of the neutronics calculations include estimates of the radial and axial fission power density profiles in the PeBR core. These results, in conjunction with a 1-D, steady-state thermal hydraulics analysis are used to select the operation and design characteristics of the PeBR point design, namely: (a) core radius and height of 38.4 cm and 120 cm, respectively, (b) pellet matrix fraction of 0.5, (c) total reactor mass of 3500 kg, excluding those of the radiation shield, the propulsion nozzle, external structure for the propellant flow into the core, and the drive mechanisms of the control drums in the radial reflector, (d) power density of 10 and 15 MW/l for a reactor thermal power of 1000 MW and 1500 MW, submersion calculations show that with all safety rods removed from the core, the 16 control drums are insufficient to maintain the reactor sub-critical. However, when the 8, B[sub 4]C safety rods are inserted into the reactor, it is possible to maintain the submerged PeBR point design $7.5 sub-critical (k[sub eff]=0.94).

  10. Neutronics and safety analysis of pellet bed reactor for nuclear thermal propulsion

    NASA Astrophysics Data System (ADS)

    Morley, Nicholas J.; El-Genk, Mohamed S.

    1993-01-01

    The Pellet Bed Reactor for Nuclear Thermal Propulsion is modeled using the TWODANT discrete ordinance code to determine a reactor point design based on the selection of a fuel fraction in and a diameter of the pellets, dimensions of the reactor core, maximum fuel temperature, and sub-criticality during a water flooding accident. A total excess reactivity of approximately 1.25 (or keff of 1.01), an order of magnitude higher than that estimated at BOM for 15 hours of full power, steady-state operation of the PeBR, is considered. Besides calculating the dimensions of the reactor core to satisfy the excess reactivity at BOM, the results of the neutronics calculations include estimates of the radial and axial fission power density profiles in the PeBR core. These results, in conjunction with a 1-D, steady-state thermal hydraulics analysis are used to select the operation and design characteristics of the PeBR point design, namely: (a) core radius and height of 38.4 cm and 120 cm, respectively, (b) pellet matrix fraction of 0.5, (c) total reactor mass of 3500 kg, excluding those of the radiation shield, the propulsion nozzle, external structure for the propellant flow into the core, and the drive mechanisms of the control drums in the radial reflector, (d) power density of 10 and 15 MW/l for a reactor thermal power of 1000 MW and 1500 MW, submersion calculations show that with all safety rods removed from the core, the 16 control drums are insufficient to maintain the reactor sub-critical. However, when the 8, B4C safety rods are inserted into the reactor, it is possible to maintain the submerged PeBR point design 7.5 sub-critical (keff=0.94).

  11. NEUTRONIC REACTOR

    DOEpatents

    Fraas, A.P.; Mills, C.B.

    1961-11-21

    A neutronic reactor in which neutron moderation is achieved primarily in its reflector is described. The reactor structure consists of a cylindrical central "island" of moderator and a spherical moderating reflector spaced therefrom, thereby providing an annular space. An essentially unmoderated liquid fuel is continuously passed through the annular space and undergoes fission while contained therein. The reactor, because of its small size, is particularly adapted for propulsion uses, including the propulsion of aircraft. (AEC)

  12. Neutronic Analyses of the Trade Demonstration Facility

    SciTech Connect

    Rubbia, C.

    2004-09-15

    The TRiga Accelerator-Driven Experiment (TRADE), to be performed in the TRIGA reactor of the ENEA-Casaccia Centre in Italy, consists of the coupling of an external proton accelerator to a target to be installed in the central channel of the reactor scrammed to subcriticality. This pilot experiment, aimed at a global demonstration of the accelerator-driven system concept, is based on an original idea of C. Rubbia. The present paper reports the results of some neutronic analyses focused on the feasibility of TRADE. Results show that all relevant experiments (at different power levels in a wide range of subcriticalities) can be carried out with relatively limited modifications to the present TRIGA reactor.

  13. REACTOR COOLING

    DOEpatents

    Quackenbush, C.F.

    1959-09-29

    A nuclear reactor with provisions for selectively cooling the fuel elements is described. The reactor has a plurality of tubes extending throughout. Cylindrical fuel elements are disposed within the tubes and the coolant flows through the tubes and around the fuel elements. The fuel elements within the central portion of the reactor are provided with roughened surfaces of material. The fuel elements in the end portions of the tubes within the reactor are provlded with low conduction jackets and the fuel elements in the region between the central portion and the end portions are provided with smooth surfaces of high heat conduction material.

  14. Criticality of spent reactor fuel

    SciTech Connect

    Harris, D.R.

    1987-01-01

    The storage capacity of spent reactor fuel pools can be greatly increased by consolidation. In this process, the fuel rods are removed from reactor fuel assemblies and are stored in close-packed arrays in a canister or skeleton. An earlier study examined criticality consideration for consolidation of Westinghouse fuel, assumed to be fresh, in canisters at the Millstone-2 spent-fuel pool and in the General Electric IF-300 shipping cask. The conclusions were that the fuel rods in the canister are so deficient in water that they are adequately subcritical, both in normal and in off-normal conditions. One potential accident, the water spill event, remained unresolved in the earlier study. A methodology is developed here for spent-fuel criticality and is applied to the water spill event. The methodology utilizes LEOPARD to compute few-group cross sections for the diffusion code PDQ7, which then is used to compute reactivity. These codes give results for fresh fuel that are in good agreement with KENO IV-NITAWL Monte Carlo results, which themselves are in good agreement with continuous energy Monte Carlo calculations. These methodologies are in reasonable agreement with critical measurements for undepleted fuel.

  15. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.

    1958-04-22

    A nuclear reactor for isotope production is described. This reactor is designed to provide a maximum thermal neutron flux in a region adjacent to the periphery of the reactor rather than in the center of the reactor. The core of the reactor is generally centrally located with respect tn a surrounding first reflector, constructed of beryllium. The beryllium reflector is surrounded by a second reflector, constructed of graphite, which, in tune, is surrounded by a conventional thermal shield. Water is circulated through the core and the reflector and functions both as a moderator and a coolant. In order to produce a greatsr maximum thermal neutron flux adjacent to the periphery of the reactor rather than in the core, the reactor is designed so tbat the ratio of neutron scattering cross section to neutron absorption cross section averaged over all of the materials in the reflector is approximately twice the ratio of neutron scattering cross section to neutron absorption cross section averaged over all of the material of the core of the reactor.

  16. Reactor building

    SciTech Connect

    Hista, J. C.

    1984-09-18

    Reactor building comprising a vessel shaft anchored in a slab which is peripherally locked. This reactor building comprises a confinement enclosure within which are positioned internal structures constituted by an internal structure floor, a vessel shaft, a slab being positioned between the general floor and the internal structure floor, the vesse

  17. NEUTRONIC REACTOR

    DOEpatents

    Metcalf, H.E.; Johnson, H.W.

    1961-04-01

    BS>A nuclear reactor incorporating fuel rods passing through a moderator and including tubes of a material of higher Thermal conductivity than the fuel in contact with the fuel is described. The tubes extend beyond the active portion of the reactor into contant with a fiuld coolant.

  18. Subcritical water liquefaction of oil palm fruit press fiber in the presence of sodium hydroxide: an optimisation study using response surface methodology.

    PubMed

    Mazaheri, Hossein; Lee, Keat Teong; Bhatia, Subhash; Mohamed, Abdul Rahman

    2010-12-01

    Thermal decomposition of oil palm fruit press fiber (FPF) into a liquid product (LP) was achieved using subcritical water treatment in the presence of sodium hydroxide in a high pressure batch reactor. This study uses experimental design and process optimisation tools to maximise the LP yield using response surface methodology (RSM) with central composite rotatable design (CCRD). The independent variables were temperature, residence time, particle size, specimen loading, and additive loading. The mathematical model that was developed fit the experimental results well for all of the response variables that were studied. The optimal conditions were found to be a temperature of 551 K, a residence time of 40 min, a particle size of 710-1000 microm, a specimen loading of 5 g, and a additive loading of 9 wt.% to achieve a LP yield of 76.16%.

  19. Evaporation and combustion of LOX under supercritical and subcritical conditions

    NASA Technical Reports Server (NTRS)

    Yang, A. S.; Hsieh, W. H.; Kuo, K. K.

    1993-01-01

    The objective is to study the evaporation and combustion of LOX under supercritical and subcritical conditions both experimentally and theoretically. In the evaporation studies, evaporation rate and surface temperature were measured when LOX vaporizing in helium environments at pressures ranging from 5 to 68 atm. A Varian 3700 gas chromatograph was employed to measure the oxygen concentration above the LOX surface. For the combustion tests, high-magnification video photography was used to record direct images of the flame shape of a LOX/H2/He laminar diffusion flame. The gas composition in the post-flame region is also being measured with the gas sampling and chromatography analysis. These data are being used to validate the theoretical model. A comprehensive theoretical model with the consideration of the solubility of ambient gases as well as variable thermophysical properties was formulated and solved numerically to study the gasification and burning of LOX at elevated pressures. The calculated flame shape agreed reasonably well with the edge of the observed luminous flame surface. The effect of gravity on the flame structure of laminar diffusion flames was found to be significant. In addition, the predicted results using the flame-sheet model were compared with those based upon full equilibrium calculations (which considered the formation of intermediate species) at supercritical pressures. Except at the flame front where temperature exceeded 2,800 K, the flame-sheet and equilibrium solutions in terms of temperature distributions were in very close agreement. The temperature deviation in the neighborhood of the flame front is caused by the effect of high-temperature dissociation.

  20. Kinetic Parameter Measurements in the MINERVE Reactor

    NASA Astrophysics Data System (ADS)

    Perret, Grégory; Geslot, Benoit; Gruel, Adrien; Blaise, Patrick; Di-Salvo, Jacques; De Izarra, Grégoire; Jammes, Christian; Hursin, Mathieu; Pautz, Andréas

    2017-01-01

    In the framework of an international collaboration, teams of the PSI and CEA research institutes measure the critical decay constant (α0 = β/A), delayed neutron fraction (β) and generation time (A) of the Minerve reactor using the Feynman-α, Power Spectral Density and Rossi-α neutron noise measurement techniques. These measurements contribute to the experimental database of kinetic parameters used to improve nuclear data files and validate modern methods in Monte Carlo codes. Minerve is a zero-power pool reactor composed of a central experimental test lattice surrounded by a large aluminum buffer and four high-enriched driver regions. Measurements are performed in three slightly subcritical configurations (-2 cents to -30 cents) using two high-efficiency 235U fission chambers in the driver regions. Measurement of α0 and β obtained by the two institutes and with the different techniques are consistent for the configurations envisaged. Slight increases of the β values are observed with the subcriticality level. Best estimate values are obtained with the Cross-Power Spectral Density technique at -2 cents, and are worth: β = 716.9±9.0 pcm, α0 = 79.0±0.6 s-1 and A = 90.7±1.4 μs. The kinetic parameters are predicted with MCNP5-v1.6 and TRIPOLI4.9 and the JEFF-3.1/3.1.1 and ENDF/B-VII.1 nuclear data libraries. The predictions for β and α0 overestimate the experimental results by 3-5% and 10-12%, respectively; that for A underestimate the experimental result by 6-7%. The discrepancies are suspected to come from the driven system nature of Minerve and the location of the detectors in the driver regions, which prevent accounting for the full reactor.

  1. Effect of water on critical and subcritical fracture properties of Woodford shale

    NASA Astrophysics Data System (ADS)

    Chen, Xiaofeng; Eichhubl, Peter; Olson, Jon E.

    2017-04-01

    Subcritical fracture behavior of shales under aqueous conditions is poorly characterized despite increased relevance to oil and gas resource development and seal integrity in waste disposal and subsurface carbon sequestration. We measured subcritical fracture properties of Woodford shale in ambient air, dry CO2 gas, and deionized water by using the double-torsion method. Compared to tests in ambient air, the presence of water reduces fracture toughness by 50%, subcritical index by 77%, and shear modulus by 27% and increases inelastic deformation. Comparison between test specimens coated with a hydrophobic agent and uncoated specimens demonstrates that the interaction of water with the bulk rock results in the reduction of fracture toughness and enhanced plastic effects, while water-rock interaction limited to the vicinity of the propagating fracture tip by a hydrophobic specimen coating lowers subcritical index and increases fracture velocity. The observed deviation of a rate-dependent subcritical index from the power law K-V relations for coated specimens tested in water is attributed to a time-dependent weakening process resulting from the interaction between water and clays in the vicinity of the fracture tip.

  2. Subcritical water extraction of flavoring and phenolic compounds from cinnamon bark (Cinnamomum zeylanicum).

    PubMed

    Khuwijitjaru, Pramote; Sayputikasikorn, Nucha; Samuhasaneetoo, Suched; Penroj, Parinda; Siriwongwilaichat, Prasong; Adachi, Shuji

    2012-01-01

    Cinnamon bark (Cinnamomum zeylanicum) powder was treated with subcritical water at 150 and 200°C in a semi-continuous system at a constant flow rate (3 mL/min) and pressure (6 MPa). Major flavoring compounds, i.e., cinnamaldehyde, cinnamic acid, cinnamyl alcohol and coumarin, were extracted at lower recoveries than the extraction using methanol, suggesting that degradation of these components might occur during the subcritical water treatment. Caffeic, ferulic, p-coumaric, protocatechuic and vanillic acids were identified from the subcritical water treatment. Extraction using subcritical water was more effective to obtain these acids than methanol (50% v/v) in both number of components and recovery, especially at 200°C. Subcritical water treatment at 200°C also resulted in a higher total phenolic content and DPPH radical scavenging activity than the methanol extraction. The DPPH radical scavenging activity and total phenolic content linearly correlated but the results suggested that the extraction at 200°C might result in other products that possessed a free radical scavenging activity other than the phenolic compounds.

  3. Solvent tailoring in coal liquefaction. Quarterly report, May 1982-August 1982. [Comparison of subcritical and supercritical conditions

    SciTech Connect

    Tarrer, A.R.; Guin, J.A.; Curtis, C.W.; Williams, D.C.

    1982-01-01

    The initial objective of this work was to study the phase distribution of donor solvents and solvent mixtures during the liquefaction of coal, to investigate the effects of phase distribution on coal conversion, and to determine the advantages, if any, of operating at subcritical and/or supercritical conditions. Computer simulations were used to predict the phase distribution, for various binary systems, as a function of temperature. The FLASH program was used to theoretically predict phase distribution for various model systems. Due to limitations in the computer program, success was achieved only in a few cases. Even in these cases, the existence of two-phase regions was observed only at temperatures and pressures far below normal liquefaction conditions. An extensive review of the literature was carried out in order to survey methods of experimentally studying vapor-liquid equilibria. Finally, some preliminary laboratory studies were carried out with the use of benzothiophene-dodecane as the model reaction system. It was felt that the study of the effect of reactor configuration on conversion would provide insight into whether phase distribution or mass transfer was the limiting consideration for coal conversion. However, no conclusive results were obtained from these studies.

  4. Subcritical water liquefaction of oil palm fruit press fiber for the production of bio-oil: effect of catalysts.

    PubMed

    Mazaheri, Hossein; Lee, Keat Teong; Bhatia, Subhash; Mohamed, Abdul Rahman

    2010-01-01

    Decomposition of oil palm fruit press fiber (FPF) to various liquid products in subcritical water was investigated using a high-pressure autoclave reactor with and without the presence of catalyst. When the reaction was carried in the absence of catalyst, the conversion of solid to liquid products increased from 54.9% at 483 K to 75.8% at 603 K. Simultaneously, the liquid yield increased from 28.8% to 39.1%. The liquid products were sub-categorized to bio-oil (benzene soluble, diethylether soluble, acetone soluble) and water soluble. When 10% ZnCl(2) was added, the conversion increased slightly but gaseous products increased significantly. However, when 10% Na(2)CO(3) and 10% NaOH were added independently, the solid conversion increased to almost 90%. In the presence of catalyst, the liquid products were mainly bio-oil compounds. Although solid conversion increased at higher reaction temperature, but the liquid yield did not increase at higher temperature.

  5. Safety status of space radioisotope and reactor power sources

    NASA Technical Reports Server (NTRS)

    Bennett, Gary L.

    1990-01-01

    The current overall safety criterion for both radioisotope and reactor power sources is containment or immobilization in the case of a reentry accident. In addition, reactors are designed to remain subcritical under conditions of land impact or water immersion. A very extensive safety test and analysis program was completed on the radioisotope thermoelectric generators (RTGs) in use on the Galileo spacecraft and planned for use on the Ulysses spacecraft. The results of this work show that the RTGs will pose little or no risk for any credible accident. The SP-100 space nuclear reactor program has begun addressing its safety criteria, and the design is planned to be such as to ensure meeting the various safety criteria. Preliminary mission risk analyses on SP-100 show the expected value population dose from postulated accidents on the reference mission to be very small. It is concluded that the current US nuclear power sources are the safest flown.

  6. Development of a small specimen test machine to evaluate irradiation embrittlement of fusion reactor materials

    NASA Astrophysics Data System (ADS)

    Ishii, T.; Ohmi, M.; Saito, J.; Hoshiya, T.; Ooka, N.; Jitsukawa, S.; Eto, M.

    2000-12-01

    Small specimen test techniques (SSTT) are essential to use an accelerator-driven deuterium-lithium stripping reaction neutron source for the study of fusion reactor materials because of the limitation of the available irradiation volume. A remote-controlled small punch (SP) test machine was developed at the hot laboratory of the Japan Materials Testing Reactor (JMTR) in the Japan Atomic Energy Research Institute (JAERI). This report describes the SP test method and machine for use in a hot cell, and test results on irradiated ferritic steels. The specimen was either a coupon 10×10×0.25 mm 3 or a TEM disk 3 mm in diameter by 0.25 mm in thickness. Tests can be performed at temperatures ranging from 93 to 1123 K in a vacuum or in an inert gas environment. The ductile to brittle transition temperature of the irradiated ferritic steel as determined by the SP test is also evaluated.

  7. Hydrodynamic Limit of Condensing Two-Species Zero Range Processes with Sub-critical Initial Profiles

    NASA Astrophysics Data System (ADS)

    Dirr, Nicolas; Stamatakis, Marios G.; Zimmer, Johannes

    2017-08-01

    Two-species condensing zero range processes (ZRPs) are interacting particle systems with two species of particles and zero range interaction exhibiting phase separation outside a domain of sub-critical densities. We prove the hydrodynamic limit of nearest neighbour mean zero two-species condensing ZRP with bounded local jump rate for sub-critical initial profiles, i.e., for initial profiles whose image is contained in the region of sub-critical densities. The proof is based on H.T. Yau's relative entropy method, which relies on the existence of sufficiently regular solutions to the hydrodynamic equation. In the particular case of the species-blind ZRP, we prove that the solutions of the hydrodynamic equation exist globally in time and thus the hydrodynamic limit is valid for all times.

  8. Enhanced enzymatic cellulose hydrolysis by subcritical carbon dioxide pretreatment of sugarcane bagasse.

    PubMed

    Zhang, Hongdan; Wu, Shubin

    2014-04-01

    Most biomass pretreatment processes for sugar production are run at low-solid concentration (<10 wt.%). Subcritical carbon dioxide (CO2) could provide a more sustainable pretreatment medium while using relative high-solid contents (15 wt.%). The effects of subcritical CO2 pretreatment of sugarcane bagasse to the solid and glucan recoveries at different pretreatment conditions were investigated. Subsequently, enzymatic hydrolysis at different hydrolysis time was applied to obtain maximal glucose yield, which can be used for ethanol fermentation. The maximum glucose yield in enzyme hydrolyzate reached 38.5 g based on 100g raw material after 72 h of enzymatic hydrolysis, representing 93.0% glucose in sugarcane bagasse. The enhanced digestibilities of subcritical CO2 pretreated sugarcane bagasse were due to the removal of hemicellulose, which were confirmed by XRD, FTIR, SEM, and TGA analyses.

  9. Environmentally friendly assessment of organic compound bioaccessibility using sub-critical water.

    PubMed

    Latawiec, Agnieszka E; Swindell, Annika L; Reid, Brian J

    2008-11-01

    The evaluation of microbial availability of contaminants is of high importance for better reflecting the processes governing contaminant fate in soil and for establishing the risk associated with contaminated sites. A sub-critical water extraction technique was assessed for its potential to determine the microbially degradable fraction of [(14)C]phenanthrene-associated activity in two dissimilar soils at three different ageing times (14, 28 and 49 days). For the majority of determinations, no significant (p>0.05) difference between sub-critical water-extracted (14)C-activity at 160 degrees C and the fraction mineralized by catabolically active Pseudomonas sp. was observed. Collectively, the results suggested that the sub-critical water extraction technique was an appropriate technique for predicting the biodegradable fraction of phenanthrene-associated (14)C-activity in dissimilar soils following increasing soil-contaminant contact time.

  10. Prompt neutron decay constants and subcritical measurements for material control and accountability in SHEBA

    SciTech Connect

    Sanchez, R.; Jaegers, P.

    1998-08-01

    Rossi-Alpha measurements were performed on the SHEBA assembly to determine the prompt neutron decay constants. These prompt neutron decay constants represent an eigenvalue characteristic of this particular assembly, which can be used to infer the amount of fissile material in the assembly. In addition, subcritical measurements using Rossi-Alpha and the source-jerk techniques were also performed on the SHEBA assembly. These measurements were compared against TWODANT calculations and agreed quite well. The subcritical measurements were also used to obtain a unique signature that represented the amount of material associated with the degree of subcriticality of the SHEBA assembly. Finally, the Feynman variance-to-mean technique in conjunction with TWODANT, were used to determine the effective delayed neutron fraction for the SHEBA assembly.

  11. Invariance Under Quasi-isometries of Subcritical and Supercritical Behavior in the Boolean Model of Percolation

    NASA Astrophysics Data System (ADS)

    Coletti, Cristian F.; Miranda, Daniel; Mussini, Filipe

    2016-02-01

    In this work we study the Poisson Boolean model of percolation in locally compact Polish metric spaces and we prove the invariance of subcritical and supercritical phases under mm-quasi-isometries. More precisely, we prove that if a metric space M is mm-quasi-isometric to another metric space N and the Poisson Boolean model in M exhibits any of the following: (a) a subcritical phase; (b) a supercritical phase; or (c) a phase transition, then respectively so does the Poisson Boolean model of percolation in N. Then we use these results in order to understand the phase transition phenomenon in a large family of metric spaces. Indeed, we study the Poisson Boolean model of percolation in the context of Riemannian manifolds, in a large family of nilpotent Lie groups and in Cayley graphs. Also, we prove the existence of a subcritical phase in Gromov spaces with bounded growth at some scale.

  12. Influence of humidity and water on subcritical crack growth in marble

    NASA Astrophysics Data System (ADS)

    Nara, Yoshitaka; Nishida, Yuki

    2014-05-01

    For the prevention of natural hazards related to the failure of rock, it is essential to investigate time-dependent deformation and fracturing in various rock materials. In addition, to ensure the long-term stability of a rock mass surrounding various structures, information of subcritical crack growth is essential. Subcritical crack growth is one of the main causes of time-dependent fracturing in rock. It is known that subcritical crack growth is influenced by not only stress but also surrounding environment. Studies of subcritical crack growth have been widely conducted for silicate rocks such as igneous rocks and sandstones. On the other hand, information of subcritical crack growth in carbonate rocks is not enough. Especially, influence of surrounding environment on subcritical crack growth in carbonate rock should be clarified to ensure the long-term integrity of a rock mass. However, influence of surrounding environmental conditions on subcritical crack growth in carbonate rock has not been clarified yet. In this study, we investigated subcritical crack growth in carbonate rocks. Specifically, we investigated the influence of relative humidity and water on subcritical crack growth in air at a constant temperature (50 °C). A marble obtained in Skopje-City in Macedonia was used as a rock sample, because this is a homogeneous, fine-grained and brittle carbonate rock. To measure subcritical crack growth, we used the load relaxation method of the double-torsion (DT) test. In order to investigate the influence of environmental condition, all measurements by DT test were conducted under controlled temperature and relative humidity. It was shown that the crack velocity in marble in air increased with increasing relative humidity at a constant temperature. Additionally, the crack velocity in water was much higher than that in air. It was also found that the crack velocity in air was higher than that predicted from a calculation theoretically at 100 % relative

  13. Hydrodynamic Limit of Condensing Two-Species Zero Range Processes with Sub-critical Initial Profiles

    NASA Astrophysics Data System (ADS)

    Dirr, Nicolas; Stamatakis, Marios G.; Zimmer, Johannes

    2017-07-01

    Two-species condensing zero range processes (ZRPs) are interacting particle systems with two species of particles and zero range interaction exhibiting phase separation outside a domain of sub-critical densities. We prove the hydrodynamic limit of nearest neighbour mean zero two-species condensing ZRP with bounded local jump rate for sub-critical initial profiles, i.e., for initial profiles whose image is contained in the region of sub-critical densities. The proof is based on H.T. Yau's relative entropy method, which relies on the existence of sufficiently regular solutions to the hydrodynamic equation. In the particular case of the species-blind ZRP, we prove that the solutions of the hydrodynamic equation exist globally in time and thus the hydrodynamic limit is valid for all times.

  14. Production of rare sugars from common sugars in subcritical aqueous ethanol.

    PubMed

    Gao, Da-Ming; Kobayashi, Takashi; Adachi, Shuji

    2015-05-15

    A new isomerization reaction was developed to synthesize rare ketoses. D-tagatose, D-xylulose, and D-ribulose were obtained in the maximum yields of 24%, 38%, and 40%, respectively, from the corresponding aldoses, D-galactose, D-xylose, and D-ribose, by treating the aldoses with 80% (v/v) subcritical aqueous ethanol at 180°C. The maximum productivity of D-tagatose was ca. 80 g/(Lh). Increasing the concentration of ethanol significantly increased the isomerization of D-galactose. Variation in the reaction temperature did not significantly affect the production of D-tagatose from D-galactose. Subcritical aqueous ethanol converted both 2,3-threo and 2,3-erythro aldoses to the corresponding C-2 ketoses in high yields. Thus, the treatment of common aldoses in subcritical aqueous ethanol can be regarded as a new method to synthesize the corresponding rare sugars. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Subcritical transition to turbulence: What we can learn from the physics of glasses.

    PubMed

    Dauchot, Olivier; Bertin, Eric

    2012-09-01

    In this note, we discuss possible analogies between the subcritical transition to turbulence in shear flows and the glass transition in supercooled liquids. We briefly review recent experimental and numerical results, as well as theoretical proposals, and compare the difficulties arising in assessing the divergence of the turbulence lifetime in subcritical shear flow with that encountered for the relaxation time in the study of the glass transition. In order to go beyond the purely methodological similarities, we further elaborate on this analogy and propose a simple model for the transition to turbulence, inspired by the random energy model (a standard model for the glass transition), with the aim to possibly foster yet-unexplored directions of research in subcritical shear flows.

  16. Incubation time for sub-critical crack propagation in SiC-SiC composites

    SciTech Connect

    El-Azab, A.; Ghoniem, N.M.

    1995-04-01

    The objective of this work is to investigate the time for sub-critical crack propagation is SiC-SiC composites at high temperatures. The effects of fiber thermal creep on the relaxation of crack bridging tractions in SiC-SiC ceramic matrix composites (CMCs) is considered in the present work, with the objective of studying the time-to propagation of sub-critical matrix cracks in this material at high temperatures. Under the condition of fiber stress relaxation in the bridiging zone, it is found that the crack opening and the stress intensity factor increase with time for sub-critical matrix cracks. The time elapsed before the stress intensity reaches the critical value for crack propagation is calculated as a function of the initial crack length, applied stress and temperature. Stability domains for matrix cracks are defined, which provide guidelines for conducting high-temperature crack propagation experiments.

  17. Compact Reactor

    NASA Astrophysics Data System (ADS)

    Williams, Pharis E.

    2007-01-01

    Weyl's Gauge Principle of 1929 has been used to establish Weyl's Quantum Principle (WQP) that requires that the Weyl scale factor should be unity. It has been shown that the WQP requires the following: quantum mechanics must be used to determine system states; the electrostatic potential must be non-singular and quantified; interactions between particles with different electric charges (i.e. electron and proton) do not obey Newton's Third Law at sub-nuclear separations, and nuclear particles may be much different than expected using the standard model. The above WQP requirements lead to a potential fusion reactor wherein deuterium nuclei are preferentially fused into helium nuclei. Because the deuterium nuclei are preferentially fused into helium nuclei at temperatures and energies lower than specified by the standard model there is no harmful radiation as a byproduct of this fusion process. Therefore, a reactor using this reaction does not need any shielding to contain such radiation. The energy released from each reaction and the absence of shielding makes the deuterium-plus-deuterium-to-helium (DDH) reactor very compact when compared to other reactors, both fission and fusion types. Moreover, the potential energy output per reactor weight and the absence of harmful radiation makes the DDH reactor an ideal candidate for space power. The logic is summarized by which the WQP requires the above conditions that make the prediction of DDH possible. The details of the DDH reaction will be presented along with the specifics of why the DDH reactor may be made to cause two deuterium nuclei to preferentially fuse to a helium nucleus. The presentation will also indicate the calculations needed to predict the reactor temperature as a function of fuel loading, reactor size, and desired output and will include the progress achieved to date.

  18. Compact Reactor

    SciTech Connect

    Williams, Pharis E.

    2007-01-30

    Weyl's Gauge Principle of 1929 has been used to establish Weyl's Quantum Principle (WQP) that requires that the Weyl scale factor should be unity. It has been shown that the WQP requires the following: quantum mechanics must be used to determine system states; the electrostatic potential must be non-singular and quantified; interactions between particles with different electric charges (i.e. electron and proton) do not obey Newton's Third Law at sub-nuclear separations, and nuclear particles may be much different than expected using the standard model. The above WQP requirements lead to a potential fusion reactor wherein deuterium nuclei are preferentially fused into helium nuclei. Because the deuterium nuclei are preferentially fused into helium nuclei at temperatures and energies lower than specified by the standard model there is no harmful radiation as a byproduct of this fusion process. Therefore, a reactor using this reaction does not need any shielding to contain such radiation. The energy released from each reaction and the absence of shielding makes the deuterium-plus-deuterium-to-helium (DDH) reactor very compact when compared to other reactors, both fission and fusion types. Moreover, the potential energy output per reactor weight and the absence of harmful radiation makes the DDH reactor an ideal candidate for space power. The logic is summarized by which the WQP requires the above conditions that make the prediction of DDH possible. The details of the DDH reaction will be presented along with the specifics of why the DDH reactor may be made to cause two deuterium nuclei to preferentially fuse to a helium nucleus. The presentation will also indicate the calculations needed to predict the reactor temperature as a function of fuel loading, reactor size, and desired output and will include the progress achieved to date.

  19. NUCLEAR REACTOR

    DOEpatents

    Moore, R.V.; Bowen, J.H.; Dent, K.H.

    1958-12-01

    A heterogeneous, natural uranium fueled, solid moderated, gas cooled reactor is described, in which the fuel elements are in the form of elongated rods and are dlsposed within vertical coolant channels ln the moderator symmetrically arranged as a regular lattice in groups. This reactor employs control rods which operate in vertical channels in the moderator so that each control rod is centered in one of the fuel element groups. The reactor is enclosed in a pressure vessel which ls provided with access holes at the top to facilitate loading and unloadlng of the fuel elements, control rods and control rod driving devices.

  20. How Small Can Fast-Spectrum Space Reactors Get?

    SciTech Connect

    Hatton, Steven A.; El-Genk, Mohamed S.

    2006-01-20

    Fast neutron spectrum space reactors are an appropriate choice for high thermal powers, but for low powers, they may not satisfy the excess reactivity requirement while remaining sub-critical when immersed in wet sand and flooded with seawater following a launch abort accident. This paper identifies the smallest size fast spectrum, Sectored, Compact Reactor loaded with Single UN fuel pins (SCoRe-S7), which satisfy the requirements of cold clean excess reactivity > $4.00 and remains at least $1.00 subcritical at shutdown and in submersion conditions. Results indicate that increasing the diameter of the SCoRe-S core reduces its active height and the UN fuel enrichment, but increases the Spectrum-Shift Absorber (SSA) of 157GdN additive to the fuel. All SCoRe-S cores also have a 0.1 mm thick 157Gd2O3 SSA coating on the outer surface of the reactor vessel to reduce the effect of the wet sand reflector, while the SSA fuel additive reduces the effect on the criticality of the flooded reactor caused by thermal neutron fission. The active core height decreases from 42.4 cm for the smallest SCoRe-S7 to as much as to 37.4 cm for the largest core of SCoRe-S11. For a 1.8 MWth reactor thermal power the UN fuel specific power decreases from 17.0 in the SCoRe-S7 to 11.5 Wth/kg in the -S11. The corresponding reactor total mass, including the BeO reflector, increases from 440 kg to 512 kg.

  1. How Small Can Fast-Spectrum Space Reactors Get?

    NASA Astrophysics Data System (ADS)

    Hatton, Steven A.; El-Genk, Mohamed S.

    2006-01-01

    Fast neutron spectrum space reactors are an appropriate choice for high thermal powers, but for low powers, they may not satisfy the excess reactivity requirement while remaining sub-critical when immersed in wet sand and flooded with seawater following a launch abort accident. This paper identifies the smallest size fast spectrum, Sectored, Compact Reactor loaded with Single UN fuel pins (SCoRe-S7), which satisfy the requirements of cold clean excess reactivity > $4.00 and remains at least $1.00 subcritical at shutdown and in submersion conditions. Results indicate that increasing the diameter of the SCoRe-S core reduces its active height and the UN fuel enrichment, but increases the Spectrum-Shift Absorber (SSA) of 157GdN additive to the fuel. All SCoRe-S cores also have a 0.1 mm thick 157Gd2O3 SSA coating on the outer surface of the reactor vessel to reduce the effect of the wet sand reflector, while the SSA fuel additive reduces the effect on the criticality of the flooded reactor caused by thermal neutron fission. The active core height decreases from 42.4 cm for the smallest SCoRe-S7 to as much as to 37.4 cm for the largest core of SCoRe-S11. For a 1.8 MWth reactor thermal power the UN fuel specific power decreases from 17.0 in the SCoRe-S7 to 11.5 Wth/kg in the -S11. The corresponding reactor total mass, including the BeO reflector, increases from 440 kg to 512 kg.

  2. Pin-Type Gas Cooled Reactor for Nuclear Electric Propulsion

    NASA Astrophysics Data System (ADS)

    Wright, Steven A.; Lipinski, Ronald J.

    2003-01-01

    This paper describes a point design for a pin-type Gas-Cooled Reactor concept that uses a fuel pin design similar to the SP100 fuel pin. The Gas-Cooled Reactor is designed to operate at 100 kWe for 7 years plus have a reduced power mode of 20% power for a duration of 5 years. The power system uses a gas-cooled, UN-fueled, pin-type reactor to heat He/Xe gas that flows directly into a recuperated Brayton system to produce electricity. Heat is rejected to space via a thermal radiator that unfolds in space. The reactor contains approximately 154 kg of 93.15 % enriched UN in 313 fuel pins. The fuel is clad with rhenium-lined Nb-1Zr. The pressures vessel and ducting are cooled by the 900 K He/Xe gas inlet flow or by thermal radiation. This permits all pressure boundaries to be made of superalloy metals rather than refractory metals, which greatly reduces the cost and development schedule required by the project. The reactor contains sufficient rhenium (a neutron poison) to make the reactor subcritical under water immersion accidents without the use of internal shutdown rods. The mass of the reactor and reflectors is about 750 kg.

  3. Pellet Bed Reactor for nuclear thermal propelled vehicles

    NASA Astrophysics Data System (ADS)

    El-Genk, Mohamed S.; Morley, Nicholas J.; Haloulakos, V. E. (Bill)

    1991-01-01

    The Pellet Bed Reactor (PeBR) concept is capable of operating at a high power density of up to 3.0 kWt/cm3 and an exit hydrogen gas temperature of 3000 K. The nominal reactor thermal power is 1500 MW and the reactor core is 0.80 m in diameter and 1.3 m high. The nominal PeBR engine generates a thrust of approximately 315 kN at a Specific Impulse (Isp) of 1000 s for a mission duration to Mars of 250 days requiring a total firing time of 170 minutes. Because of its low diameter-to-height ratio, PeBR has enough surface area for passive removal of the decay heat from the reactor core. In addition, the reactor is equipped with two independent shutdown mechanisms; 8-D4C safety rods and 26 BeO/B4C control drums; each system is capable of operating and scraming the reactor safely. The core k-effective at Beginning of-Life (BOL) is about 1.07 and in case of water immersion the reactor core is subcritical (k-effective of 0.93). Due to the absence of core internal support structures, the PeBR can be fueled and refueled in orbit using the vacuum of space. These unique features of the PeBR provide for safety during launch, simplicity of handling, deployment, and end-of-life disposal, and vehicle extended lifetime.

  4. Experiments on Substrate Erosion via Subcritical Turbidity Currents

    NASA Astrophysics Data System (ADS)

    McElroy, B.; Mohrig, D.; Buttles, J.

    2006-12-01

    system. This experiment points out turbulence generated near the bed is not the only contributor to sediment transport in relatively thin, subcritical turbidity currents. Turbulence produced by breaking internal waves at the current-ambient fluid interface can augment vertical mixing throughout the entire current affecting local sediment transport and patterns of bed erosion and deposition.

  5. NEUTRONIC REACTOR

    DOEpatents

    Fermi, E.

    1960-04-01

    A nuclear reactor is described consisting of blocks of graphite arranged in layers, natural uranium bodies disposed in holes in alternate layers of graphite blocks, and coolant tubes disposed in the layers of graphite blocks which do not contain uranium.

  6. NEUTRONIC REACTORS

    DOEpatents

    Wigner, E.P.

    1960-11-22

    A nuclear reactor is described wherein horizontal rods of thermal- neutron-fissionable material are disposed in a body of heavy water and extend through and are supported by spaced parallel walls of graphite.

  7. NEUTRONIC REACTOR

    DOEpatents

    Anderson, H.L.

    1960-09-20

    A nuclear reactor is described comprising fissionable material dispersed in graphite blocks, helium filling the voids of the blocks and the spaces therebetween, and means other than the helium in thermal conductive contact with the graphite for removing heat.

  8. Reactor apparatus

    DOEpatents

    Echtler, J. Paul

    1981-01-01

    A reactor apparatus for hydrocracking a polynuclear aromatic hydrocarbonaceous feedstock to produce lighter hydrocarbon fuels by contacting the hydrocarbonaceous feedstock with hydrogen in the presence of a molten metal halide catalyst.

  9. Chemical Reactors.

    ERIC Educational Resources Information Center

    Kenney, C. N.

    1980-01-01

    Describes a course, including content, reading list, and presentation on chemical reactors at Cambridge University, England. A brief comparison of chemical engineering education between the United States and England is also given. (JN)

  10. NEUTRONIC REACTOR

    DOEpatents

    Hurwitz, H. Jr.; Brooks, H.; Mannal, C.; Payne, J.H.; Luebke, E.A.

    1959-03-24

    A reactor of the heterogeneous, liquid cooled type is described. This reactor is comprised of a central region of a plurality of vertically disposed elongated tubes surrounded by a region of moderator material. The central region is comprised of a central core surrounded by a reflector region which is surrounded by a fast neutron absorber region, which in turn is surrounded by a slow neutron absorber region. Liquid sodium is used as the primary coolant and circulates through the core which contains the fuel elements. Control of the reactor is accomplished by varying the ability of the reflector region to reflect neutrons back into the core of the reactor. For this purpose the reflector is comprised of moderator and control elements having varying effects on reactivity, the control elements being arranged and actuated by groups to give regulation, shim, and safety control.

  11. Reactor Engineering

    NASA Astrophysics Data System (ADS)

    Lema, Juan M.; López, Carmen; Eibes, Gemma; Taboada-Puig, Roberto; Moreira, M. Teresa; Feijoo, Gumersindo

    In this chapter, the engineering aspects of processes catalyzed by peroxidases will be presented. In particular, a discussion of the existing technologies that utilize peroxidases for different purposes, such as the removal of recalcitrant compounds or the synthesis of polymers, is analyzed. In the first section, the essential variables controlling the process will be investigated, not only those that are common in any enzymatic system but also those specific to peroxidative reactions. Next, different reactor configurations and operational modes will be proposed, emphasizing their suitability and unsuitability for different systems. Finally, two specific reactors will be described in detail: enzymatic membrane reactors and biphasic reactors. These configurations are especially valuable for the treatment of xenobiotics with high and poor water solubility, respectively.

  12. NUCLEAR REACTOR

    DOEpatents

    Miller, H.I.; Smith, R.C.

    1958-01-21

    This patent relates to nuclear reactors of the type which use a liquid fuel, such as a solution of uranyl sulfate in ordinary water which acts as the moderator. The reactor is comprised of a spherical vessel having a diameter of about 12 inches substantially surrounded by a reflector of beryllium oxide. Conventionnl control rods and safety rods are operated in slots in the reflector outside the vessel to control the operation of the reactor. An additional means for increasing the safety factor of the reactor by raising the ratio of delayed neutrons to prompt neutrons, is provided and consists of a soluble sulfate salt of beryllium dissolved in the liquid fuel in the proper proportion to obtain the result desired.

  13. NUCLEAR REACTOR

    DOEpatents

    Sherman, J.; Sharbaugh, J.E.; Fauth, W.L. Jr.; Palladino, N.J.; DeHuff, P.G.

    1962-10-23

    A nuclear reactor incorporating seed and blanket assemblies is designed. Means are provided for obtaining samples of the coolant from the blanket assemblies and for varying the flow of coolant through the blanket assemblies. (AEC)

  14. REACTOR SHIELD

    DOEpatents

    Wigner, E.P.; Ohlinger, L.E.; Young, G.J.; Weinberg, A.M.

    1959-02-17

    Radiation shield construction is described for a nuclear reactor. The shield is comprised of a plurality of steel plates arranged in parallel spaced relationship within a peripheral shell. Reactor coolant inlet tubes extend at right angles through the plates and baffles are arranged between the plates at right angles thereto and extend between the tubes to create a series of zigzag channels between the plates for the circulation of coolant fluid through the shield. The shield may be divided into two main sections; an inner section adjacent the reactor container and an outer section spaced therefrom. Coolant through the first section may be circulated at a faster rate than coolant circulated through the outer section since the area closest to the reactor container is at a higher temperature and is more radioactive. The two sections may have separate cooling systems to prevent the coolant in the outer section from mixing with the more contaminated coolant in the inner section.

  15. NEUTRONIC REACTORS

    DOEpatents

    Vernon, H.C.

    1959-01-13

    A neutronic reactor of the heterogeneous, fluid cooled tvpe is described. The reactor is comprised of a pressure vessel containing the moderator and a plurality of vertically disposed channels extending in spaced relationship through the moderator. Fissionable fuel material is placed within the channels in spaced relationship thereto to permit circulation of the coolant fluid. Separate means are provided for cooling the moderator and for circulating a fluid coolant thru the channel elements to cool the fuel material.

  16. NUCLEAR REACTOR

    DOEpatents

    Anderson, C.R.

    1962-07-24

    A fluidized bed nuclear reactor and a method of operating such a reactor are described. In the design means are provided for flowing a liquid moderator upwardly through the center of a bed of pellets of a nentron-fissionable material at such a rate as to obtain particulate fluidization while constraining the lower pontion of the bed into a conical shape. A smooth circulation of particles rising in the center and falling at the outside of the bed is thereby established. (AEC)

  17. NUCLEAR REACTOR

    DOEpatents

    Breden, C.R.; Dietrich, J.R.

    1961-06-20

    A water-soluble non-volatile poison may be introduced into a reactor to nullify excess reactivity. The poison is removed by passing a side stream of the water containing the soluble poison to an evaporation chamber. The vapor phase is returned to the reactor to decrease the concentration of soluble poison and the liquid phase is returned to increase the concentration of soluble poison.

  18. BENCHMARK EVALUATION OF THE START-UP CORE REACTOR PHYSICS MEASUREMENTS OF THE HIGH TEMPERATURE ENGINEERING TEST REACTOR

    SciTech Connect

    John Darrell Bess

    2010-05-01

    The benchmark evaluation of the start-up core reactor physics measurements performed with Japan’s High Temperature Engineering Test Reactor, in support of the Next Generation Nuclear Plant Project and Very High Temperature Reactor Program activities at the Idaho National Laboratory, has been completed. The evaluation was performed using MCNP5 with ENDF/B-VII.0 nuclear data libraries and according to guidelines provided for inclusion in the International Reactor Physics Experiment Evaluation Project Handbook. Results provided include updated evaluation of the initial six critical core configurations (five annular and one fully-loaded). The calculated keff eigenvalues agree within 1s of the benchmark values. Reactor physics measurements that were evaluated include reactivity effects measurements such as excess reactivity during the core loading process and shutdown margins for the fully-loaded core, four isothermal temperature reactivity coefficient measurements for the fully-loaded core, and axial reaction rate measurements in the instrumentation columns of three core configurations. The calculated values agree well with the benchmark experiment measurements. Fully subcritical and warm critical configurations of the fully-loaded core were also assessed. The calculated keff eigenvalues for these two configurations also agree within 1s of the benchmark values. The reactor physics measurement data can be used in the validation and design development of future High Temperature Gas-cooled Reactor systems.

  19. NUCLEAR REACTOR

    DOEpatents

    Grebe, J.J.

    1959-07-14

    High temperature reactors which are uniquely adapted to serve as the heat source for nuclear pcwered rockets are described. The reactor is comprised essentially of an outer tubular heat resistant casing which provides the main coolant passageway to and away from the reactor core within the casing and in which the working fluid is preferably hydrogen or helium gas which is permitted to vaporize from a liquid storage tank. The reactor core has a generally spherical shape formed entirely of an active material comprised of fissile material and a moderator material which serves as a diluent. The active material is fabricated as a gas permeable porous material and is interlaced in a random manner with very small inter-connecting bores or capillary tubes through which the coolant gas may flow. The entire reactor is divided into successive sections along the direction of the temperature gradient or coolant flow, each section utilizing materials of construction which are most advantageous from a nuclear standpoint and which at the same time can withstand the operating temperature of that particular zone. This design results in a nuclear reactor characterized simultaneously by a minimum critiral size and mass and by the ability to heat a working fluid to an extremely high temperature.

  20. Anisotropic etching of monocrystalline silicon under subcritical conditions

    NASA Astrophysics Data System (ADS)

    Gonzalez-Pereyra, Nestor Gabriel

    Sub- and supercritical fluids remain an underexploited resource for materials processing. Around its critical point a common compound such as water behaves like a different substance exhibiting changes in its properties that modify its behavior as a solvent and unlock reaction paths not viable in other conditions. In the subcritical region water's properties can be directed by controlling temperature and pressure. Water and silicon are two of the most abundant, versatile, environmentally non-harmful, and simplest substances on Earth. They are among the most researched and best-known substances. Both are ubiquitous and essential for present-day world. Silicon is fundamental in semiconductor fabrication, microelectromechanical systems, and photovoltaic cells. Wet etching of silicon is a fabrication strategy shared by these three applications. Processing of silicon requires large amounts of water, often involving dangerous and environmentally hazardous chemicals. Yet, minimal knowledge is available on the ways high temperature water interacts with crystalline silicon. The purpose of this project is to identify and implement a method for the modification of monocrystalline silicon surfaces with three important characteristics: 1) requires minimal amounts of added chemicals, 2) controllability of morphological features formed, 3) reduced processing time. This will be accomplished by subjecting crystalline silicon to diluted alkaline solutions working in the subcritical region of water. This approach allows for variations on surface morphologies and etching rates by adapting the reactions conditions, with focus on composition and temperature of the solutions used. The work reported discusses the techniques used for producing surfaces with a variety of morphologies that ultimately allowed to create patterns and textures on silicon wafers, using highly diluted alkaline solutions that can be used for photovoltaic applications. These morphologies were created with a

  1. Research reactors - an overview

    SciTech Connect

    West, C.D.

    1997-03-01

    A broad overview of different types of research and type reactors is provided in this paper. Reactor designs and operating conditions are briefly described for four reactors. The reactor types described include swimming pool reactors, the High Flux Isotope Reactor, the Mark I TRIGA reactor, and the Advanced Neutron Source reactor. Emphasis in the descriptions is placed on safety-related features of the reactors. 7 refs., 7 figs., 2 tabs.

  2. Critical and Subcritical 0-Power Experiment at Rensselaer (CaSPER)

    SciTech Connect

    Arthur, Jennifer Ann

    2016-05-09

    This report discusses the 0-power experiment at Rensselaer Polytechnic Institute (CaSPER). Keff simulation results, list-mode multiplication results, and related work are included. The aim of the work is subcritical measurements for code and nuclear data validation.

  3. ELUTION OF ORGANIC SOLUTES FROM DIFFERENT POLARITY SORBENTS USING SUBCRITICAL WATER. (R825394)

    EPA Science Inventory

    The intermolecular interactions between organic solutes and sorbent matrices under subcritical water conditions have been investigated at a pressure of 50 bar and temperatures ranging from 50 to 250°C. Both polar and nonpolar organics (chlorophenols, amines, n-alkanes...

  4. Time-delayed feedback control of coherence resonance near subcritical Hopf bifurcation: Theory versus experiment

    SciTech Connect

    Semenov, Vladimir; Feoktistov, Alexey; Vadivasova, Tatyana; Schöll, Eckehard Zakharova, Anna

    2015-03-15

    Using the model of a generalized Van der Pol oscillator in the regime of subcritical Hopf bifurcation, we investigate the influence of time delay on noise-induced oscillations. It is shown that for appropriate choices of time delay, either suppression or enhancement of coherence resonance can be achieved. Analytical calculations are combined with numerical simulations and experiments on an electronic circuit.

  5. Production of keto-disaccharides from aldo-disaccharides in subcritical aqueous ethanol.

    PubMed

    Gao, Da-Ming; Kobayashi, Takashi; Adachi, Shuji

    2016-05-01

    Isomerization of disaccharides (maltose, isomaltose, cellobiose, lactose, melibiose, palatinose, sucrose, and trehalose) was investigated in subcritical aqueous ethanol. A marked increase in the isomerization of aldo-disaccharides to keto-disaccharides was noted and their hydrolytic reactions were suppressed with increasing ethanol concentration. Under any study condition, the maximum yield of keto-disaccharides produced from aldo-disaccharides linked by β-glycosidic bond was higher than that produced from aldo-disaccharides linked by α-glycosidic bond. Palatinose, a keto-disaccharide, mainly underwent decomposition rather than isomerization in subcritical water and subcritical aqueous ethanol. No isomerization was noted for the non-reducing disaccharides trehalose and sucrose. The rate constant of maltose to maltulose isomerization almost doubled by changing solvent from subcritical water to 80 wt% aqueous ethanol at 220 °C. Increased maltose monohydrate concentration in feed decreased the conversion of maltose and the maximum yield of maltulose, but increased the productivity of maltulose. The maximum productivity of maltulose was ca. 41 g/(h kg-solution).

  6. NEUTRONIC REACTOR

    DOEpatents

    Ohlinger, L.A.; Wigner, E.P.; Weinberg, A.M.; Young, G.J.

    1958-09-01

    This patent relates to neutronic reactors of the heterogeneous water cooled type, and in particular to a fuel element charging and discharging means therefor. In the embodiment illustrated the reactor contains horizontal, parallel coolant tubes in which the fuel elements are disposed. A loading cart containing a magnzine for holding a plurality of fuel elements operates along the face of the reactor at the inlet ends of the coolant tubes. The loading cart is equipped with a ram device for feeding fuel elements from the magazine through the inlot ends of the coolant tubes. Operating along the face adjacent the discharge ends of the tubes there is provided another cart means adapted to receive irradiated fuel elements as they are forced out of the discharge ends of the coolant tubes by the incoming new fuel elements. This cart is equipped with a tank coataining a coolant, such as water, into which the fuel elements fall, and a hydraulically operated plunger to hold the end of the fuel element being discharged. This inveation provides an apparatus whereby the fuel elements may be loaded into the reactor, irradiated therein, and unloaded from the reactor without stopping the fiow of the coolant and without danger to the operating personnel.

  7. HILBILAC development for accelerator-driven transmutation

    SciTech Connect

    Pirozhenko, V.; Plink, O.

    1995-10-01

    High-Intensity Low-Beta Ion Linac (HILBILAC) is intended for acceleration of ion beams with current of about 1 A and higher. The CW HILBILAC with beam current of 2l50 mA is under development at MRTI. Concept of parameters choice is presented along with results of beam dynamics and resonator parameters calculations. A pulse prototype HILBILAC-TEST will have to be constructed and tested for the CW accelerator development, its scheme and parameters are presented.

  8. Accelerator-driven boron neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Edgecock, Rob

    2014-05-01

    Boron Neutron Capture Therapy is a binary treatment for certain types of cancer. It works by loading the cancerous cells with a boron-10 carrying compound. This isotope has a large cross-section for thermal neutrons, the reaction producing a lithium nucleus and alpha particle that kill the cell in which they are produced. Recent studies of the boron carrier compound indicate that the uptake process works best in particularly aggressive cancers. Most studied is glioblastoma multiforme and a trial using a combination of BNCT and X-ray radiotherapy has shown an increase of nearly a factor of two in mean survival over the state of the art. However, the main technical problem with BNCT remains producing a sufficient flux of neutrons for a reasonable treatment duration in a hospital environment. This paper discusses this issue.

  9. Miniature accelerator-driven gamma source concept.

    SciTech Connect

    Garnett, R. W.; Chan, K. D.; Wangler, Thomas P.,; Wood R. L.; Carlsten, B. E.; Kirbie, H. C.

    2003-01-01

    Recent developments in W-band (-100 GHz) traveling wave tube technology at Los Alarnos may lead to a compact high-power W-band RE source. A conceptual design of a compact 8-MeV electron linac that codd be powered by this source is presented, including electromagnetic structure calculations, proposed rnicrojbbrication and manufacturing methods, supporting calculations to estimate accelerator performance, and gumma production rates based on preliminary target geometries and expected output beam current.

  10. NUCLEAR REACTOR

    DOEpatents

    Christy, R.F.

    1958-07-15

    A nuclear reactor of the homogeneous liquid fuel type is described wherein the fissionable isotope is suspended or dissolved in a liquid moderator such as water. The reactor core is comprised essentially of a spherical vessel for containing the reactive composition surrounded by a reflector, preferably of beryllium oxide. The reactive composition may be an ordinary water solution of a soluble salt of uranium, the quantity of fissionable isotope in solution being sufficient to provide a critical mass in the vessel. The liquid fuel is stored in a tank of non-crtttcal geometry below the reactor vessel and outside of the reflector and is passed from the tank to the vessel through a pipe connecting the two by air pressure means. Neutron absorbing control and safety rods are operated within slots in the reflector adjacent to the vessel.

  11. NEUTRONIC REACTOR

    DOEpatents

    Metcalf, H.E.

    1957-10-01

    A reactor of the type which preferably uses plutonium as the fuel and a liquid moderator, preferably ordinary water, and which produces steam within the reactor core due to the heat of the chain reaction is described. In the reactor shown the fuel elements are essentially in the form of trays and are ventically stacked in spaced relationship. The water moderator is continuously supplied to the trays to maintain a constant level on the upper surfaces of the fuel element as it is continually evaporated by the heat. The steam passes out through the spaces between the fuel elements and is drawn off at the top of the core. The fuel elements are clad in aluminum to prevent deterioration thereof with consequent contamimation of the water.

  12. REACTOR CONTROL

    DOEpatents

    Fortescue, P.; Nicoll, D.

    1962-04-24

    A control system employed with a high pressure gas cooled reactor in which a control rod is positioned for upward and downward movement into the neutron field from a position beneath the reactor is described. The control rod is positioned by a coupled piston cylinder releasably coupled to a power drive means and the pressurized coolant is directed against the lower side of the piston. The coolant pressure is offset by a higher fiuid pressure applied to the upper surface of the piston and means are provided for releasing the higher pressure on the upper side of the piston so that the pressure of the coolant drives the piston upwardly, forcing the coupled control rod into the ncutron field of the reactor. (AEC)

  13. NEUTRONIC REACTORS

    DOEpatents

    Wigner, E.P.; Young, G.J.

    1958-10-14

    A method is presented for loading and unloading rod type fuel elements of a neutronic reactor of the heterogeneous, solld moderator, liquid cooled type. In the embodiment illustrated, the fuel rods are disposed in vertical coolant channels in the reactor core. The fuel rods are loaded and unloaded through the upper openings of the channels which are immersed in the coolant liquid, such as water. Unloading is accomplished by means of a coffer dam assembly having an outer sleeve which is placed in sealing relation around the upper opening. A radiation shield sleeve is disposed in and reciprocable through the coffer dam sleeve. A fuel rod engaging member operates through the axial bore in the radiation shield sleeve to withdraw the fuel rod from its position in the reactor coolant channel into the shield, the shield snd rod then being removed. Loading is accomplished in the reverse procedure.

  14. Bioconversion reactor

    DOEpatents

    McCarty, Perry L.; Bachmann, Andre

    1992-01-01

    A bioconversion reactor for the anaerobic fermentation of organic material. The bioconversion reactor comprises a shell enclosing a predetermined volume, an inlet port through which a liquid stream containing organic materials enters the shell, and an outlet port through which the stream exits the shell. A series of vertical and spaced-apart baffles are positioned within the shell to force the stream to flow under and over them as it passes from the inlet to the outlet port. The baffles present a barrier to the microorganisms within the shell causing them to rise and fall within the reactor but to move horizontally at a very slow rate. Treatment detention times of one day or less are possible.

  15. Catalytic reactor

    SciTech Connect

    Aaron, Timothy Mark; Shah, Minish Mahendra; Jibb, Richard John

    2009-03-10

    A catalytic reactor is provided with one or more reaction zones each formed of set(s) of reaction tubes containing a catalyst to promote chemical reaction within a feed stream. The reaction tubes are of helical configuration and are arranged in a substantially coaxial relationship to form a coil-like structure. Heat exchangers and steam generators can be formed by similar tube arrangements. In such manner, the reaction zone(s) and hence, the reactor is compact and the pressure drop through components is minimized. The resultant compact form has improved heat transfer characteristics and is far easier to thermally insulate than prior art compact reactor designs. Various chemical reactions are contemplated within such coil-like structures such that as steam methane reforming followed by water-gas shift. The coil-like structures can be housed within annular chambers of a cylindrical housing that also provide flow paths for various heat exchange fluids to heat and cool components.

  16. POWER REACTOR

    DOEpatents

    Zinn, W.H.

    1958-07-01

    A fast nuclear reactor system ls described for producing power and radioactive isotopes. The reactor core is of the heterogeneous, fluid sealed type comprised of vertically arranged elongated tubular fuel elements having vertical coolant passages. The active portion is surrounded by a neutron reflector and a shield. The system includes pumps and heat exchangers for the primary and secondary coolant circuits. The core, primary coolant pump and primary heat exchanger are disposed within an irapenforate tank which is filled with the primary coolant, in this case a liquid metal such as Na or NaK, to completely submerge these elements. The tank is completely surrounded by a thick walled concrete shield. This reactor system utilizes enriched uranium or plutonium as the fissionable material, uranium or thorium as a diluent and thorium or uranium containing less than 0 7% of the U/sup 235/ isotope as a fertile material.

  17. Plutonium Critical Mass Curve Comparison to Mass at Upper Subcritical Limit (USL) Using Whisper

    SciTech Connect

    Alwin, Jennifer Louise; Zhang, Ning

    2016-09-27

    Whisper is computational software designed to assist the nuclear criticality safety analyst with validation studies with the MCNP® Monte Carlo radiation transport package. Standard approaches to validation rely on the selection of benchmarks based upon expert judgment. Whisper uses sensitivity/uncertainty (S/U) methods to select relevant benchmarks to a particular application or set of applications being analyzed. Using these benchmarks, Whisper computes a calculational margin. Whisper attempts to quantify the margin of subcriticality (MOS) from errors in software and uncertainties in nuclear data. The combination of the Whisper-derived calculational margin and MOS comprise the baseline upper subcritical limit (USL), to which an additional margin may be applied by the nuclear criticality safety analyst as appropriate to ensure subcriticality. A series of critical mass curves for plutonium, similar to those found in Figure 31 of LA-10860-MS, have been generated using MCNP6.1.1 and the iterative parameter study software, WORM_Solver. The baseline USL for each of the data points of the curves was then computed using Whisper 1.1. The USL was then used to determine the equivalent mass for plutonium metal-water system. ANSI/ANS-8.1 states that it is acceptable to use handbook data, such as the data directly from the LA-10860-MS, as it is already considered validated (Section 4.3 4) “Use of subcritical limit data provided in ANSI/ANS standards or accepted reference publications does not require further validation.”). This paper attempts to take a novel approach to visualize traditional critical mass curves and allows comparison with the amount of mass for which the keff is equal to the USL (calculational margin + margin of subcriticality). However, the intent is to plot the critical mass data along with USL, not to suggest that already accepted handbook data should have new and more rigorous requirements for validation.

  18. NEUTRONIC REACTOR

    DOEpatents

    Fermi, E.; Szilard, L.

    1957-09-24

    Reactors of the type employing plates of natural uranium in a moderator are discussed wherein the plates are um-formly disposed in parallel relationship to each other thereby separating the moderator material into distinct and individual layers. Each plate has an uninterrupted sunface area substantially equal to the cross-sectional area of the active portion of the reactor, the particular size of the plates and the volume ratio of moderator to uranium required to sustain a chain reaction being determinable from the known purity of these materials and other characteristics such as the predictable neutron losses due to the formation of radioactive elements of extremely high neutron capture cross section.

  19. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.; Weinberg, A.W.; Young, G.J.

    1958-04-15

    A nuclear reactor which uses uranium in the form of elongated tubes as fuel elements and liquid as a coolant is described. Elongated tubular uranium bodies are vertically disposed in an efficient neutron slowing agent, such as graphite, for example, to form a lattice structure which is disposed between upper and lower coolant tanks. Fluid coolant tubes extend through the uranium bodies and communicate with the upper and lower tanks and serve to convey the coolant through the uranium body. The reactor is also provided with means for circulating the cooling fluid through the coolant tanks and coolant tubes, suitable neutron and gnmma ray shields, and control means.

  20. Hydrothermal decomposition of liquid crystal in subcritical water.

    PubMed

    Zhuang, Xuning; He, Wenzhi; Li, Guangming; Huang, Juwen; Lu, Shangming; Hou, Lianjiao

    2014-04-30

    Treatment of liquid crystal has important significance for the environment protection and human health. This study proposed a hydrothermal process to decompose the liquid crystal of 4-octoxy-4'-cyanobiphenyl. Experiments were conducted with a 5.7 mL stainless tube reactor and heated by a salt-bath. Factors affecting the decomposition rate of 4-octoxy-4'-cyanobiphenyl were evaluated with HPLC. The decomposed liquid products were characterized by GC-MS. Under optimized conditions i.e., 0.2 mL H2O2 supply, pH value 6, temperature 275°C and reaction time 5 min, 97.6% of 4-octoxy-4'-cyanobiphenyl was decomposed into simple and environment-friendly products. Based on the mechanism analysis and products characterization, a possible hydrothermal decomposition pathway was proposed. The results indicate that hydrothermal technology is a promising choice for liquid crystal treatment.

  1. Influence of temperature and water on subcritical crack growth parameters and long-term strength for igneous rocks

    NASA Astrophysics Data System (ADS)

    Nara, Yoshitaka; Yamanaka, Hiroshi; Oe, Yuma; Kaneko, Katsuhiko

    2013-04-01

    Understanding of time-dependent deformation and fracture propagation in rock is essential, since the knowledge of the long-term integrity of rock is required for many subsurface structures excavated in a rock mass. Time-dependent fracture propagation has been invoked as a potential key mechanism responsible for the increase in seismicity preceding earthquake ruptures and volcanic eruptions. In engineering projects, and in preventing natural hazards, the study of subcritical crack growth and the long-term strength of rock is necessary. Since the long-term strength is affected by the values of the subcritical crack growth parameters, it is important to know the influence of the surrounding environment on the subcritical crack growth parameters and long-term strength. The influence of the surrounding environment on the subcritical crack growth parameters, however, has not been completely clarified yet. In this study, the subcritical crack growth parameters were estimated under various environmental conditions on igneous rocks (andesite and granite) using the Double-Torsion method. Based on the results of subcritical crack growth parameters estimations, we calculated the long-term strength of rock. It was shown that the subcritical crack growth parameters were affected by the environmental conditions such as the temperature, humidity and existence of water. Especially, it was shown that the subcritical crack growth index in water was smaller than that in air. When the relative humidity of the air was higher, subcritical crack growth index tended to be smaller. The subcritical crack growth index at 90 per cent relative humidity was close to the value in water. By the calculation based on the results of our subcritical crack growth parameters estimation, it was shown that long-term strength decreased under the conditions of higher temperature, humidity in air and in water. It is concluded that the subcritical crack growth parameters and long-term strength are affected by

  2. Neutronic analysis of a fusion hybrid reactor

    SciTech Connect

    Kammash, T.

    2012-07-01

    In a PHYSOR 2010 paper(1) we introduced a fusion hybrid reactor whose fusion component is the gasdynamic mirror (GDM), and whose blanket was made of thorium - 232. The thrust of that study was to demonstrate the performance of such a reactor by establishing the breeding of uranium - 233 in the blanket, and the burning thereof to produce power. In that analysis, we utilized the diffusion equation for one-energy neutron group, namely, those produced by the fusion reactions, to establish the power distribution and density in the system. Those results should be viewed as a first approximation since the high energy neutrons are not effective in inducing fission, but contribute primarily to the production of actinides. In the presence of a coolant, however, such as water, these neutrons tend to thermalize rather quickly, hence a better assessment of the reactor performance would require at least a two group analysis, namely the fast and thermal groups. We follow that approach and write an approximate set of equations for the fluxes of these groups. From these relations we deduce the all-important quantity, k{sub eff}, which we utilize to compute the multiplication factor, and subsequently, the power density in the reactor. We show that k{sub eff} can be made to have a value of 0.99, thus indicating that 100 thermal neutrons are generated per fusion neutron, while allowing the system to function as 'subcritical.' Moreover, we show that such a hybrid reactor can generate hundreds of megawatts of thermal power per cm of length depending on the flux of the fusion neutrons impinging on the blanket. (authors)

  3. Correlation of nuclear criticality safety computer codes with plutonium benchmark experiments and derivation of subcritical limits. [MGBS, TGAN, KEFF, HRXN, GLASS, ANISN, SPBL, and KENO

    SciTech Connect

    Clark, H.K.

    1981-10-01

    A compilation of benchmark critical experiments was made for essentially one-dimensional systems containing plutonium. The systems consist of spheres, series of experiments with cylinders and cuboids that permit extrapolation to infinite cylinders and slabs, and large cylinders for which separability of the neutron flux into a product of spatial components is a good approximation. Data from the experiments were placed in a form readily usable as computer code input. Aqueous solutions of Pu(NO/sub 3/)/sub 4/ are treated as solutions of PuO/sub 2/ in nitric acid. The apparent molal volume of PuO/sub 2/ as a function of plutonium concentration was derived from analyses of solution density data and was incorporated in the Savannah River Laboratory computer codes along with density tables for nitric acid. The biases of three methods of calculation were established by correlation with the benchmark experiments. The oldest method involves two-group diffusion theory and has been used extensively at the Savannah River Laboratory. The other two involve S/sub n/ transport theory with, in one method, Hansen-Roach cross sections and, in the other, cross sections derived from ENDF/B-IV. Subcritical limits were calculated by all three methods. Significant differences were found among the results and between the results and limits currently in the American National Standard for Nuclear Criticality Safety in Operations with Fissionable Materials Outside Reactor (ANSI N16.1), which were calculated by yet another method, despite the normalization of all four methods to the same experimental data. The differences were studied, and a set of subcritical limits was proposed to supplement and in some cases to replace those in the ANSI Standard, which is currently being reviewed.

  4. Neutronic reactor

    DOEpatents

    Carleton, John T.

    1977-01-25

    A graphite-moderated nuclear reactor includes channels between blocks of graphite and also includes spacer blocks between adjacent channeled blocks with an axis of extension normal to that of the axis of elongation of the channeled blocks to minimize changes in the physical properties of the graphite as a result of prolonged neutron bombardment.

  5. Sonochemical Reactors.

    PubMed

    Gogate, Parag R; Patil, Pankaj N

    2016-10-01

    Sonochemical reactors are based on the generation of cavitational events using ultrasound and offer immense potential for the intensification of physical and chemical processing applications. The present work presents a critical analysis of the underlying mechanisms for intensification, available reactor configurations and overview of the different applications exploited successfully, though mostly at laboratory scales. Guidelines have also been presented for optimum selection of the important operating parameters (frequency and intensity of irradiation, temperature and liquid physicochemical properties) as well as the geometric parameters (type of reactor configuration and the number/position of the transducers) so as to maximize the process intensification benefits. The key areas for future work so as to transform the successful technique at laboratory/pilot scale into commercial technology have also been discussed. Overall, it has been established that there is immense potential for sonochemical reactors for process intensification leading to greener processing and economic benefits. Combined efforts from a wide range of disciplines such as material science, physics, chemistry and chemical engineers are required to harness the benefits at commercial scale operation.

  6. NEUTRONIC REACTORS

    DOEpatents

    Anderson, H.L.

    1958-10-01

    The design of control rods for nuclear reactors are described. In this design the control rod consists essentially of an elongated member constructed in part of a neutron absorbing material and having tube means extending therethrough for conducting a liquid to cool the rod when in use.

  7. NEUTRONIC REACTOR

    DOEpatents

    Creutz, E.C.; Ohlinger, L.A.; Weinberg, A.M.; Wigner, E.P.; Young, G.J.

    1959-10-27

    BS>A reactor cooled by water, biphenyl, helium, or other fluid with provision made for replacing the fuel rods with the highest plutonium and fission product content without disassembling the entire core and for promptly cooling the rods after their replacement in order to prevent build-up of heat from fission product activity is described.

  8. Neutronic reactor

    DOEpatents

    Wende, Charles W. J.

    1976-08-17

    A safety rod for a nuclear reactor has an inner end portion having a gamma absorption coefficient and neutron capture cross section approximately equal to those of the adjacent shield, a central portion containing materials of high neutron capture cross section and an outer end portion having a gamma absorption coefficient at least equal to that of the adjacent shield.

  9. Dynamical Safety Analysis of the SABR Fusion-Fission Hybrid Reactor

    NASA Astrophysics Data System (ADS)

    Sumner, Tyler; Stacey, Weston; Ghiaassian, Seyed

    2009-11-01

    A hybrid fusion-fission reactor for the transmutation of spent nuclear fuel is being developed at Georgia Tech. The Subcritical Advanced Burner Reactor (SABR) is a 3000 MWth sodium-cooled, metal TRU-Zr fueled fast reactor driven by a tokamak fusion neutron source based on ITER physics and technology. We are investigating the accident dynamics of SABR's coupled fission, fusion and heat removal systems to explore the safety characteristics of a hybrid reactor. Possible accident scenarios such as loss of coolant mass flow (LOFA), of power (LOPA) and of heat sink (LOHSA), as well as inadvertent reactivity insertions and fusion source excursion are being analyzed using the RELAP5-3D code, the ATHENA version of which includes liquid metal coolants.

  10. American National Standard ANSI/ANS-8. 6, Safety in conducting subcritical neutron---Multiplication measurement in situ

    SciTech Connect

    McLaughlin, T.P.

    1991-01-01

    There are many examples of expeditious and cost effective in situ measurements dating from the 1940's and 50's. These subcritical experiment, upon which the safety of operations were based, were paralleled by numerous critical experiments which provide most of the bases for computer code validations presently. As the capability to expeditiously and cost effectively perform critical experiments withers, in situ subcritical measurements may provide the information necessary to further reduce uncertainties and biases in safety margins and thus incorporate more safety and efficiency into process operations. Finally, certain site restoration activities may demand knowledge of the subcritical state before disturbing the buried material. In situ neutron multiplication measurements may offer the only practical means to this knowledge. This document discusses the standard of conducting subcritical Neutron-Multiplication measurements, in situ. 4 refs., 1 fig.

  11. Solid-Core, Gas-Cooled Reactor for Space and Surface Power

    SciTech Connect

    King, Jeffrey C.; El-Genk, Mohamed S.

    2006-01-20

    The solid-core, gas-cooled, Submersion-Subcritical Safe Space (S and 4) reactor is developed for future space power applications and avoidance of single point failures. The Mo-14%Re reactor core is loaded with uranium nitride fuel in enclosed cavities, cooled by He-30%Xe, and sized to provide 550 kWth for seven years of equivalent full power operation. The beryllium oxide reflector disassembles upon impact on water or soil. In addition to decreasing the reactor and shadow shield mass, Spectral Shift Absorber (SSA) materials added to the reactor core ensure that it remains subcritical in the worst-case submersion accident. With a 0.1 mm thick boron carbide coating on the outside surface of the core block and 0.25 mm thick iridium sleeves around the fuel stacks, the reflector outer diameter is 43.5 cm and the combined reactor and shadow shield mass is 935.1 kg. With 12.5 atom% gadolinium-155 added to the fuel, 2.0 mm diameter gadolinium-155 sesquioxide intersititial pins, and a 0.1 mm thick gadolinium-155 sesquioxide coating, the S and 4 reactor has a slightly smaller reflector outer diameter of 43.0 cm, and a total reactor and shield mass of 901.7 kg. With 8.0 atom% europium-151 added to the fuel, 2.0 mm diameter europium-151 sesquioxide interstitial pins, and a 0.1 mm thick europium-151 sesquioxide coating, the reflector's outer diameter and the total reactor and shield mass are further reduced to 41.5 cm and 869.2 kg, respect0011ive.

  12. MONTE CARLO SIMULATIONS OF PERIODIC PULSED REACTOR WITH MOVING GEOMETRY PARTS

    SciTech Connect

    Cao, Yan; Gohar, Yousry

    2015-11-01

    In a periodic pulsed reactor, the reactor state varies periodically from slightly subcritical to slightly prompt supercritical for producing periodic power pulses. Such periodic state change is accomplished by a periodic movement of specific reactor parts, such as control rods or reflector sections. The analysis of such reactor is difficult to perform with the current reactor physics computer programs. Based on past experience, the utilization of the point kinetics approximations gives considerable errors in predicting the magnitude and the shape of the power pulse if the reactor has significantly different neutron life times in different zones. To accurately simulate the dynamics of this type of reactor, a Monte Carlo procedure using the transfer function TRCL/TR of the MCNP/MCNPX computer programs is utilized to model the movable reactor parts. In this paper, two algorithms simulating the geometry part movements during a neutron history tracking have been developed. Several test cases have been developed to evaluate these procedures. The numerical test cases have shown that the developed algorithms can be utilized to simulate the reactor dynamics with movable geometry parts.

  13. Determination of the relative power density distribution in a heterogeneous reactor from the results of measurements of the reactivity effects and the neutron importance function

    SciTech Connect

    Bobrov, A. A.; Glushkov, E. S.; Zimin, A. A.; Kapitonova, A. V.; Kompaniets, G. V.; Nosov, V. I. Petrushenko, R. P.; Smirnov, O. N.

    2012-12-15

    A method for experimental determination of the relative power density distribution in a heterogeneous reactor based on measurements of fuel reactivity effects and importance of neutrons from a californium source is proposed. The method was perfected on two critical assembly configurations at the NARCISS facility of the Kurchatov Institute, which simulated a small-size heterogeneous nuclear reactor. The neutron importance measurements were performed on subcritical and critical assemblies. It is shown that, along with traditionally used activation methods, the developed method can be applied to experimental studies of special features of the power density distribution in critical assemblies and reactors.

  14. Determination of the relative power density distribution in a heterogeneous reactor from the results of measurements of the reactivity effects and the neutron importance function

    NASA Astrophysics Data System (ADS)

    Bobrov, A. A.; Glushkov, E. S.; Zimin, A. A.; Kapitonova, A. V.; Kompaniets, G. V.; Nosov, V. I.; Petrushenko, R. P.; Smirnov, O. N.

    2012-12-01

    A method for experimental determination of the relative power density distribution in a heterogeneous reactor based on measurements of fuel reactivity effects and importance of neutrons from a californium source is proposed. The method was perfected on two critical assembly configurations at the NARCISS facility of the Kurchatov Institute, which simulated a small-size heterogeneous nuclear reactor. The neutron importance measurements were performed on subcritical and critical assemblies. It is shown that, along with traditionally used activation methods, the developed method can be applied to experimental studies of special features of the power density distribution in critical assemblies and reactors.

  15. NUCLEAR REACTOR

    DOEpatents

    Grebe, J.J.

    1959-12-15

    A reactor which is particularly adapted tu serve as a heat source for a nuclear powered alrcraft or rocket is described. The core of this reactor consists of a porous refractory modera;or body which is impregnated with fissionable nuclei. The core is designed so that its surface forms tapered inlet and outlet ducts which are separated by the porous moderator body. In operation a gaseous working fluid is circulated through the inlet ducts to the surface of the moderator, enters and passes through the porous body, and is heated therein. The hot gas emerges into the outlet ducts and is available to provide thrust. The principle advantage is that tremendous quantities of gas can be quickly heated without suffering an excessive pressure drop.

  16. REACTOR UNLOADING

    DOEpatents

    Leverett, M.C.

    1958-02-18

    This patent is related to gas cooled reactors wherein the fuel elements are disposed in vertical channels extending through the reactor core, the cooling gas passing through the channels from the bottom to the top of the core. The invention is a means for unloading the fuel elements from the core and comprises dump values in the form of flat cars mounted on wheels at the bottom of the core structure which support vertical stacks of fuel elements. When the flat cars are moved, either manually or automatically, for normal unloading purposes, or due to a rapid rise in the reproduction ratio within the core, the fuel elements are permtted to fall by gravity out of the core structure thereby reducing the reproduction ratio or stopping the reaction as desired.

  17. NEUTRONIC REACTOR

    DOEpatents

    Wade, E.J.

    1958-09-16

    This patent relates to a reflector means for a neutronic reactor. A reflector comprised of a plurality of vertically movable beryllium control members is provided surrounding the sides of the reactor core. An absorber of fast neutrons comprised of natural uramum surrounds the reflector. An absorber of slow neutrons surrounds the absorber of fast neutrons and is formed of a plurality of beryllium blocks having natural uranium members distributcd therethrough. in addition, a movable body is positioned directly below the core and is comprised of a beryllium reflector and an absorbing member attached to the botiom thereof, the absorbing member containing a substance selected from the goup consisting of natural urantum and Th/sup 232/.

  18. REACTOR MONITORING

    DOEpatents

    Bugbee, S.J.; Hanson, V.F.; Babcock, D.F.

    1959-02-01

    A neutron density inonitoring means for reactors is described. According to this invention a tunnel is provided beneath and spaced from the active portion of the reactor and extends beyond the opposite faces of the activc portion. Neutron beam holes are provided between the active portion and the tunnel and open into the tunnel near the middle thereof. A carriage operates back and forth in the tunnel and is adapted to convey a neutron detector, such as an ion chamber, and position it beneath one of the neutron beam holes. This arrangement affords convenient access of neutron density measuring instruments to a location wherein direct measurement of neutron density within the piles can be made and at the same time affords ample protection to operating personnel.

  19. Nuclear reactor

    DOEpatents

    Wade, Elman E.

    1979-01-01

    A nuclear reactor including two rotatable plugs and a positive top core holddown structure. The top core holddown structure is divided into two parts: a small core cover, and a large core cover. The small core cover, and the upper internals associated therewith, are attached to the small rotating plug, and the large core cover, with its associated upper internals, is attached to the large rotating plug. By so splitting the core holddown structures, under-the-plug refueling is accomplished without the necessity of enlarging the reactor pressure vessel to provide a storage space for the core holddown structure during refueling. Additionally, the small and large rotating plugs, and their associated core covers, are arranged such that the separation of the two core covers to permit rotation is accomplished without the installation of complex lifting mechanisms.

  20. NUCLEAR REACTOR

    DOEpatents

    Treshow, M.

    1958-08-19

    A neuclear reactor is described of the heterogeneous type and employing replaceable tubular fuel elements and heavy water as a coolant and moderator. A pluraltty of fuel tubesa having their axes parallel, extend through a tank type pressure vessel which contatns the liquid moderator. The fuel elements are disposed within the fuel tubes in the reaetive portion of the pressure vessel during normal operation and the fuel tubes have removable plug members at each end to permit charging and discharging of the fuel elements. The fuel elements are cylindrical strands of jacketed fissionable material having helical exterior ribs. A bundle of fuel elements are held within each fuel tube with their longitudinal axes parallel, the ribs serving to space them apart along their lengths. Coolant liquid is circulated through the fuel tubes between the spaced fuel elements. Suitable control rod and monitoring means are provided for controlling the reactor.

  1. Neutronic reactor

    DOEpatents

    Lewis, Warren R.

    1978-05-30

    A graphite-moderated, water-cooled nuclear reactor including a plurality of rectangular graphite blocks stacked in abutting relationship in layers, alternate layers having axes which are normal to one another, alternate rows of blocks in alternate layers being provided with a channel extending through the blocks, said channeled blocks being provided with concave sides and having smaller vertical dimensions than adjacent blocks in the same layer, there being nuclear fuel in the channels.

  2. NUCLEAR REACTORS

    DOEpatents

    Long, E.; Ashby, J.W.

    1958-09-16

    ABS>A graphite moderator structure is presented for a nuclear reactor compriscd of an assembly of similarly orientated prismatic graphite blocks arranged on spaced longitudinal axes lying in common planes wherein the planes of the walls of the blocks are positioned so as to be twisted reintive to the planes of said axes so thatthe unlmpeded dtrect paths in direction wholly across the walls of the blocks are limited to the width of the blocks plus spacing between the blocks.

  3. NUCLEAR REACTOR

    DOEpatents

    Grebe, J.J.

    1961-01-24

    A core structure for neutronic reactors adapted for the propulsion of aircraft and rockets is offered. The core is designed for cooling by gaseous media, and comprises a plurality of hollow tapered tubular segments of a porous moderating material impregniated with fissionable fuel nested about a common axis. Alternate ends of the segments are joined. In operation a coolant gas passes through the porous structure and is heated.

  4. NUCLEAR REACTORS

    DOEpatents

    Koch, L.J.; Rice, R.E. Jr.; Denst, A.A.; Rogers, A.J.; Novick, M.

    1961-12-01

    An active portion assembly for a fast neutron reactor is described wherein physical distortions resulting in adverse changes in the volume-to-mass ratio are minimized. A radially expandable locking device is disposed within a cylindrical tube within each fuel subassembly within the active portion assembly, and clamping devices expandable toward the center of the active portion assembly are disposed around the periphery thereof. (AEC)

  5. Subcritical ethanol extraction of flavonoids from Moringa oleifera leaf and evaluation of antioxidant activity.

    PubMed

    Wang, Yongqiang; Gao, Yujie; Ding, Hui; Liu, Shejiang; Han, Xu; Gui, Jianzhou; Liu, Dan

    2017-03-01

    A large-scale process to extract flavonoids from Moringa oleifera leaf by subcritical ethanol was developed and HPLC-MS analysis was conducted to qualitatively identify the compounds in the extracts. To optimize the effects of process parameters on the yield of flavonoids, a Box-Behnken design combined with response surface methodology was conducted in the present work. The results indicated that the highest extraction yield of flavonoids by subcritical ethanol extraction could reach 2.60% using 70% ethanol at 126.6°C for 2.05h extraction. Under the optimized conditions, flavonoids yield was substantially improved by 26.7% compared with the traditional ethanol reflux method while the extraction time was only 2h, and obvious energy saving was observed. FRAP and DPPH assays showed that the extracts had strong antioxidant and free radical scavenging activities. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. On a 1D nonlocal transport equation with nonlocal velocity and subcritical or supercritical diffusion

    NASA Astrophysics Data System (ADS)

    Lazar, Omar

    2016-11-01

    We study a 1D transport equation with nonlocal velocity with subcritical or supercritical dissipation. For all data in the weighted Sobolev space Hk (wλ,κ) ∩L∞, where k = max ⁡ (0 , 3 / 2 - α) and wλ,κ is a given family of Muckenhoupt weights, we prove a global existence result in the subcritical case α ∈ (1 , 2). We also prove a local existence theorem for large data in H2 (wλ,κ) ∩L∞ in the supercritical case α ∈ (0 , 1). The proofs are based on the use of the weighted Littlewood-Paley theory, interpolation along with some new commutator estimates.

  7. REACTOR CONTROL

    DOEpatents

    Ruano, W.J.

    1957-12-10

    This patent relates to nuclear reactors of the type which utilize elongited rod type fuel elements immersed in a liquid moderator and shows a design whereby control of the chain reaction is obtained by varying the amount of moderator or reflector material. A central tank for containing liquid moderator and fuel elements immersed therein is disposed within a surrounding outer tank providing an annular space between the two tanks. This annular space is filled with liquid moderator which functions as a reflector to reflect neutrons back into the central reactor tank to increase the reproduction ratio. Means are provided for circulating and cooling the moderator material in both tanks and additional means are provided for controlling separately the volume of moderator in each tank, which latter means may be operated automatically by a neutron density monitoring device. The patent also shows an arrangement for controlling the chain reaction by injecting and varying an amount of poisoning material in the moderator used in the reflector portion of the reactor.

  8. Space reactors

    NASA Astrophysics Data System (ADS)

    Ranken, W. A.

    1983-01-01

    Progress in design studies and technology for the SP-100 Project - successor to the Space Power Advanced Reactor (SPAR) Project - is reported for the period October 1, 1981 to March 31, 1982. The basis for selecting a high-temperature, UO2-fueled, heat-pipe-cooled reactor with a thermoelectric conversion system as the 100/kW-sub e/ reference design has been reviewed. Although no change has been made in the general concept, design studies have been done to investigate various reactor/conversion system coupling methods and core design modifications. Thermal and mechanical finite element modeling and three dimensional Monte Carlo analysis of a core with individual finned fuel elements are reported. Studies of unrestrained fuel irradiation data are discussed that are relevant both to the core modeling work and to the design and fabrication of the first in-pile irradiation test, which is also reported. Work on lithium-filled core heat pipe development is described, including the attainment of 15.6 kW/sub t/ operation at 1525 K for a 2-m-long heat pipe with a 15.7-mm outside diameter. The successful operation of a 5.5-m-long, lightweight potassium/titanium heat pipe at 760 K is described, and test results of a thermoelectric module with GaP-modified SiGe thermoelectric elements are presented.

  9. Reactivity Control Schemes for Fast Spectrum Space Nuclear Reactors

    SciTech Connect

    Craft, Aaron E.; King, Jeffrey C.

    2008-01-21

    Several different reactivity control schemes are considered for future space nuclear reactor power systems. Each of these control schemes uses a combination of boron carbide absorbers and/or beryllium oxide reflectors to achieve sufficient reactivity swing to keep the reactor subcritical during launch and to provide sufficient excess reactivity to operate the reactor over its expected 7-15 year lifetime. The size and shape of the control system directly impacts the size and mass of the space reactor's reflector and shadow shield, leading to a tradeoff between reactivity swing and total system mass. This paper presents a trade study of drum, shutter, and petal control schemes based on reactivity swing and mass effects for a representative fast-spectrum, gas-cooled reactor. For each control scheme, the dimensions and composition of the core are constant, and the reflector is sized to provide $5 of cold-clean excess reactivity with each configuration in its most reactive state. The advantages and disadvantages of each configuration are discussed, along with optimization techniques and novel geometric approaches for each scheme.

  10. CONCEPTUAL DESIGN OF A LUNAR REGOLITH CLUSTERED-REACTOR SYSTEM

    SciTech Connect

    John Darrell Bess

    2009-06-01

    It is proposed that a fast-fission, heatpipe-cooled, lunar-surface power reactor system be divided into subcritical units that could be launched safely without the incorporation of additional spectral shift absorbers or other complex means of control. The reactor subunits are to be emplaced directly into the lunar regolith utilizing the regolith not just for shielding but as the reflector material to increase the neutron economy of the system. While a single subunit cannot achieve criticality by itself, coordinated placement of additional subunits will provide a critical reactor system for lunar surface power generation. A lunar regolith clustered-reactor system promotes reliability, safety, and ease of manufacture and testing at the cost of a slight increase in launch mass per rated power level and an overall reduction in neutron economy when compared to a single-reactor system. Additional subunits may be launched with future missions to increase the cluster size and power according to desired lunar base power demand and lifetime. The results address the potential uncertainties associated with the lunar regolith material and emplacement of the subunit systems. Physical distance between subunits within the clustered emplacement exhibits the most significant feedback regarding changes in overall system reactivity. Narrow, deep holes will be the most effective in reducing axial neutron leakage from the core. The variation in iron concentration in the lunar regolith can directly influence the overall system reactivity although its effects are less than the more dominant factors of subunit emplacement.

  11. Bio-oil production via subcritical hydrothermal liquefaction of biomass

    NASA Astrophysics Data System (ADS)

    Durak, Halil

    2017-04-01

    Biomass based raw materials can be converted into the more valued energy forms using biochemical methods such as ethanol fermentation, methane fermentation and the thermochemical methods such as direct combustion, pyrolysis, gasification, liquefaction. The bio-oil obtained from the biomass has many advantages than traditional use. Firstly, it has features such as high energy density, easy storage and easy transportation. Bio-oil can be used as a fuel in engines, turbines and burning units directly. Besides, it can be converted into products in higher quality and volume via catalytic cracking, hydrodexygenation, emulsification, and steam reforming [1,2]. Many organic solvents such as acetone, ethanol, methanol, isopropanol are used in the supercritical liquefaction processes. When we think about the cost and effects of the organic solvent on nature, it will be understood better that it is necessary to find solvent that are more sensitive against nature. Here, water must have an important place because of its features. Most important solvent of the world water is named as "universal solvent" because none of the liquids can dissolve the materials as much as done by water. Water is found much at the nature and cost of it is very few when compared with the other solvent. Hydrothermal liquefaction, a thermochemical conversion process is an effective method used for converting biomass into the liquid products. General reaction conditions for hydrothermal liquefaction process are the 250-374 °C temperature range and 4 - 22 Mpa pressure values range, besides, the temperature values can be higher according to the product that is expected to be obtained [3,4]. In this study, xanthium strumarium plant stems have been used as biomass source. The experiments have been carried out using a cylindrical reactor (75 mL) at the temperatures of 300 °C. The produced liquids at characterized by elemental analysis, GC-MS and FT-IR. According to the analysis, different types of compounds

  12. Evaluation of sub-critical fatigue crack propagation in a restorative composite.

    PubMed

    Loughran, Galyna M; Versluis, Antheunis; Douglas, William H

    2005-03-01

    Fracture is a major reason for clinical failure of dental restorations. Many clinical fractures are likely to be preceded by a slow sub-critical crack propagation. The purpose of this study was to determine slow crack propagation in a restorative composite. Notched composite (Z100, 3M ESPE) specimens were fatigued in a four-point bending test. The notch (1 mm) was created by embedding a sharpened razor blade in the specimen mold. The specimens were load-cycled at 5 Hz between -5 and -30 N until failure. Displacement and load were recorded during the fatigue tests and used to derive crack propagation based on beam-compliance. The number of cycles until failure ranged between 34 and 82,481. In the last 1500 cycles prior to final fracture, the beam compliance increased consistently, indicating sub-critical crack propagation. It was calculated from the compliance change that the crack length increased 8% (77 +/- 14 microm) before final failure. The crack growth rate during sub-critical crack propagation was determined as a function of the stress intensity for the last 1500 cycles before fracture. A method is presented to determine slow crack propagation using a four-point bending test. Although fatigue lifetime varied widely, stable crack growth prior to fracture was consistent. This consistency allowed formulation of stress-based crack propagation relationships that can be used in concert with numerical simulations to predict composite restoration performance. The large variation found for specimen lifetime was attributed to the initiation process that precedes sub-critical crack propagation.

  13. The effect of fluid composition, salinity, and acidity on subcritical crack growth in calcite crystals

    NASA Astrophysics Data System (ADS)

    Bergsaker, Anne Schad; Røyne, Anja; Ougier-Simonin, Audrey; Aubry, Jérôme; Renard, François

    2016-03-01

    Chemically activated processes of subcritical cracking in calcite control the time-dependent strength of this mineral, which is a major constituent of the Earth's brittle upper crust. Here experimental data on subcritical crack growth are acquired with a double torsion apparatus to characterize the influence of fluid pH (range 5-7.5) and ionic strength and species (Na2SO4, NaCl, MgSO4, and MgCl2) on the propagation of microcracks in calcite single crystals. The effect of different ions on crack healing has also been investigated by decreasing the load on the crack for durations up to 30 min and allowing it to relax and close. All solutions were saturated with CaCO3. The crack velocities reached during the experiments are in the range 10-9-10-2 m/s and cover the range of subcritical to close to dynamic rupture propagation velocities. Results show that for calcite saturated solutions, the energy necessary to fracture calcite is independent of pH. As a consequence, the effects of fluid salinity, measured through its ionic strength, or the variation of water activity have stronger effects on subcritical crack propagation in calcite than pH. Consequently, when considering the geological sequestration of CO2 into carbonate reservoirs, the decrease of pH within the range of 5-7.5 due to CO2 dissolution into water should not significantly alter the rate of fracturing of calcite. Increase in salinity caused by drying may lead to further reduction in cracking and consequently a decrease in brittle creep. The healing of cracks is found to vary with the specific ions present.

  14. Pressure recovery, drag, and subcritical stability characteristics of conical supersonic diffusers with boundary-layer removal

    NASA Technical Reports Server (NTRS)

    Obey, Leonard T; Englert, Gerald W; Nussdorfer, Theodore J , Jr

    1952-01-01

    A study of two 20 degrees half-angle, low mass-flow ratio conical supersonic inlets with cone boundary-layer bleed was made on a 16-inch ram-jet engine in the Lewis 8- by 6-foot supersonic wind tunnel. A greater stable subcritical range of operation was obtained with the bleed inlets than with the corresponding inlet without boundary-layer bleed. The drag added by the bleed system was small.

  15. Determination of subcritical frequency and damping from B-1 flight flutter test data

    NASA Technical Reports Server (NTRS)

    Dobbs, S. K.; Hodson, C. H.

    1979-01-01

    The application of the time-lag products correlation/frequency analysis procedure to determine subcritical frequency and damping from structural response measurements made during flight flutter test of the B-1 prototype airplane is described. The analysis procedure, the test airplane, and flight test procedures are discussed. Summary frequency and damping results are presented for six transonic flight conditions. Illustrative results obtained by applying various options and variations of the analysis method are included for one flight condition.

  16. Transient behavior of a nuclear reactor coupled to an accelerator

    NASA Astrophysics Data System (ADS)

    Sadineni, Suresh Babu

    Accelerator Driven Systems (ADS) present one of the most viable solutions for transmutation and effective utilization of nuclear fuel. Spent fuel from reactors will be partitioned to separate plutonium and other minor actinides to be transmuted in the ADS. Without the ADS, minor actinides must be stored at a geologic repository for long periods of time. One problem with ADS is understanding the control issues that arise when coupling an accelerator to a reactor. "ADSTRANS" was developed to predict the transient behavior of a nuclear reactor coupled to an accelerator. It was based on MCNPX, a radiation transport code developed at the LANL, and upon a numerical model of the neutron transport equation. MCNPX was used to generate the neutron "source" term that occurs when the accelerator is fired. ADSTRANS coupled MCNPX to a separate finite difference code that solved the transient neutron transport equation. A cylindrical axisymmetric reactor with steel shielding was considered for this analysis. Multiple neutron energy groups, neutron precursor groups and neutron poisons were considered. ENDF/B cross-section data obtained through MCNPX was also employed. The reactor was assumed to be isothermal and near zero power level. Unique features of this code are: (1) it predicts the neutron behavior of an ADS for different reactor geometry, material concentration, both electron and proton particle accelerators, and target material, (2) it develops input files for MCNPX to simulate neutron production, runs MCNPX, and retrieves information from the MCNPX output files. Neutron production predicted by MCNPX for a 20 MeV electron accelerator and lead target was compared with experimental data from the Idaho Accelerator Center and found to be in good agreement. The spatial neutron flux distribution and transient neutron flux in the reactor as predicted by the code were compared with analytical solutions and found to be in good agreement. Fuel burnup and poison buildup were also as

  17. Subcritical crack propagation as a mechanism of crevasse formation and iceberg calving

    NASA Astrophysics Data System (ADS)

    Weiss, Jérôme

    Recent investigations of crevassing on alpine glaciers and ice shelves have been based on linear elastic fracture mechanics (LEFM). However, LEFM is unable to explain some aspects of crevasse formation such as the initiation of crevasse propagation from crystal-scale (mm) microcracks, the slow propagation of large fractures in ice shelves, and the acceleration of crevasse opening before breaking of the ice terminus. Here another mechanism to account for these observations is proposed: subcritical crevassing. Subcritical crack growth, documented in many materials though not yet explored in ice, is characterized by a crack velocity that scales as a power of the tensile stress intensity factor, but is much less than that associated with critical crack propagation. This mechanism allows crevasse propagation from mm-scale microcracks at velocities much lower than body wave speeds, and explains crevasse-opening accelerations in a natural way. Subcritical crevassing is theoretically explored for several simplified situations but is limited by a lack of available data on crevasse evolution.

  18. Experimental study of elliptical jet from supercritical to subcritical conditions using planar laser induced fluorescence

    NASA Astrophysics Data System (ADS)

    Muthukumaran, C. K.; Vaidyanathan, Aravind

    2015-03-01

    The study of fluid jet dynamics at supercritical conditions involves strong coupling between fluid dynamic and thermodynamic phenomena. Beyond the critical point, the liquid-vapor coexistence ceases to exist, and the fluid exists as a single phase known as supercritical fluid with its properties that are entirely different from liquids and gases. At the critical point, the liquids do not possess surface tension and latent heat of evaporation. Around the critical point, the fluid undergoes large changes in density and possesses thermodynamic anomaly like enhancement in thermal conductivity and specific heat. In the present work, the transition of the supercritical and near-critical elliptical jet into subcritical as well as supercritical environment is investigated experimentally with nitrogen and helium as the surrounding environment. Under atmospheric condition, a liquid jet injected from the elliptical orifice exhibits axis switching phenomena. As the injection temperature increases, the axis switching length also increases. Beyond the critical temperature, the axis switching is not observed. The investigation also revealed that pressure plays a major role in determining the thermodynamic transition of the elliptical jet only for the case of supercritical jet injected into subcritical chamber conditions. At larger pressures, the supercritical jet undergoes disintegration and formation of droplets in the subcritical environment is observed. However, for supercritical jet injection into supercritical environment, the gas-gas like mixing behavior is observed.

  19. Subcritical crack growth in soda-lime glass in combined mode I and mode II loading

    NASA Technical Reports Server (NTRS)

    Singh, Dileep; Shetty, Dinesh K.

    1990-01-01

    Subcritical crack growth under mixed-mode loading was studied in soda-lime glass. Pure mode I, combined mode I and mode II, and pure mode II loadings were achieved in precracked disk specimens by loading in diametral compression at selected angles with respect to the symmetric radial crack. Crack growth was monitored by measuring the resistance changes in a microcircuit grid consisting of parallel, electrically conducting grid lines deposited on the surface of the disk specimens by photolithography. Subcritical crack growth rates in pure mode I, pure mode II, and combined mode I and mode II loading could be described by an exponential relationship between crack growth rate and an effective crack driving force derived from a mode I-mode II fracture toughness envelope. The effective crack driving force was based on an empirical representation of the noncoplanar strain energy release rate. Stress intensities for kinked cracks were assessed using the method of caustics and an initial decrease and a subsequent increase in the subcritical crack growth rates of kinked cracks were shown to correlate with the variations of the mode I and the mode II stress intensities.

  20. Advanced Subcritical Assistance Radioisotope Thermoelectric Generator: An Imperative Solution for the Future of NASA Exploration

    NASA Astrophysics Data System (ADS)

    Arias, F. J.

    A new generation of radioisotope thermoelectrical generator is proposed for very long space exploration missions. The Advanced Subcritical Assistance Radioisotope Thermoelectric Generator (ASA-RTG) amplify the power from natural decay of pu-238 by a small subcritical multiplication produced from the small neutron background generated from (α, n) reactions between the α particles from Pu-238 and beryllium, lithium or other low-Z isotope, extracting the maximum advantage and performance from the precious α disintegration, and then of the very scarce pu-238. The process is self controlled by the natural decay of Pu-238 with the progressive reduction of the power output (RTG) and additionally and simultaneously compensate by the natural decay of a neutronic poisson which increase simultaneously the subcritical multiplication resulting in a contrary effect, i.e., causing an increase in the power. ASA-RTG is not in conflict with previous RTG, and could fit within the type of Radioisotope Thermoelectric Generator developed for NASA space missions as the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) and the Advanced Stirling Radioisotope Generator (ASRG).

  1. Experimental study of elliptical jet from supercritical to subcritical conditions using planar laser induced fluorescence

    SciTech Connect

    Muthukumaran, C. K.; Vaidyanathan, Aravind

    2015-03-15

    The study of fluid jet dynamics at supercritical conditions involves strong coupling between fluid dynamic and thermodynamic phenomena. Beyond the critical point, the liquid-vapor coexistence ceases to exist, and the fluid exists as a single phase known as supercritical fluid with its properties that are entirely different from liquids and gases. At the critical point, the liquids do not possess surface tension and latent heat of evaporation. Around the critical point, the fluid undergoes large changes in density and possesses thermodynamic anomaly like enhancement in thermal conductivity and specific heat. In the present work, the transition of the supercritical and near-critical elliptical jet into subcritical as well as supercritical environment is investigated experimentally with nitrogen and helium as the surrounding environment. Under atmospheric condition, a liquid jet injected from the elliptical orifice exhibits axis switching phenomena. As the injection temperature increases, the axis switching length also increases. Beyond the critical temperature, the axis switching is not observed. The investigation also revealed that pressure plays a major role in determining the thermodynamic transition of the elliptical jet only for the case of supercritical jet injected into subcritical chamber conditions. At larger pressures, the supercritical jet undergoes disintegration and formation of droplets in the subcritical environment is observed. However, for supercritical jet injection into supercritical environment, the gas-gas like mixing behavior is observed.

  2. Optimization of subcritical fluid extraction of bioactive compounds using Hansen solubility parameters.

    PubMed

    Srinivas, K; King, J W; Monrad, J K; Howard, L R; Hansen, C M

    2009-08-01

    Process engineering operations in food and nutraceutical industries pertaining to the design of extraction of value-added products from biomass using pressurized liquids involve a careful selection of the solvent and optimal temperature conditions to achieve maximum yield. Complex molecular structure and limited physical property data in the literature of biological solutes extracted from biomass compounds have necessitated the process modeling of such operations. In this study, we have applied the Hansen 3-dimensional solubility parameter concept to optimize the extraction of molecularly complex solutes using subcritical fluid solvents. Hansen solubility spheres characterized by the relative energy differences (RED) have been used to characterize and quantify the solute-subcritical solvent interactions as a function of temperature. The solvent power of subcritical water and compressed hydroethanolic mixtures above their boiling points has been characterized using the above-mentioned method. The use of group contribution methods in collaboration with computerized algorithms to plot the Hansen spheres provides a quantitative prediction tool for optimizing the design of extraction conditions. The method can be used to estimate conditions for solute-solvent miscibility, an optimum temperature range for conducting extractions under pressurized conditions, and approximate extraction conditions of solutes from natural matrices.

  3. Neutron Detector Signal Processing to Calculate the Effective Neutron Multiplication Factor of Subcritical Assemblies

    SciTech Connect

    Talamo, Alberto; Gohar, Yousry

    2016-06-01

    This report describes different methodologies to calculate the effective neutron multiplication factor of subcritical assemblies by processing the neutron detector signals using MATLAB scripts. The subcritical assembly can be driven either by a spontaneous fission neutron source (e.g. californium) or by a neutron source generated from the interactions of accelerated particles with target materials. In the latter case, when the particle accelerator operates in a pulsed mode, the signals are typically stored into two files. One file contains the time when neutron reactions occur and the other contains the times when the neutron pulses start. In both files, the time is given by an integer representing the number of time bins since the start of the counting. These signal files are used to construct the neutron count distribution from a single neutron pulse. The built-in functions of MATLAB are used to calculate the effective neutron multiplication factor through the application of the prompt decay fitting or the area method to the neutron count distribution. If the subcritical assembly is driven by a spontaneous fission neutron source, then the effective multiplication factor can be evaluated either using the prompt neutron decay constant obtained from Rossi or Feynman distributions or the Modified Source Multiplication (MSM) method.

  4. Subcritical crack growth in soda-lime glass in combined mode I and mode II loading

    NASA Technical Reports Server (NTRS)

    Singh, Dileep; Shetty, Dinesh K.

    1990-01-01

    Subcritical crack growth under mixed-mode loading was studied in soda-lime glass. Pure mode I, combined mode I and mode II, and pure mode II loadings were achieved in precracked disk specimens by loading in diametral compression at selected angles with respect to the symmetric radial crack. Crack growth was monitored by measuring the resistance changes in a microcircuit grid consisting of parallel, electrically conducting grid lines deposited on the surface of the disk specimens by photolithography. Subcritical crack growth rates in pure mode I, pure mode II, and combined mode I and mode II loading could be described by an exponential relationship between crack growth rate and an effective crack driving force derived from a mode I-mode II fracture toughness envelope. The effective crack driving force was based on an empirical representation of the noncoplanar strain energy release rate. Stress intensities for kinked cracks were assessed using the method of caustics and an initial decrease and a subsequent increase in the subcritical crack growth rates of kinked cracks were shown to correlate with the variations of the mode I and the mode II stress intensities.

  5. Fermentable hexose production from corn stalks and wheat straw with combined supercritical and subcritical hydrothermal technology.

    PubMed

    Zhao, Yan; Lu, Wen-Jing; Wang, Hong-Tao; Yang, Jin-Long

    2009-12-01

    Lignocellulosic wastes, including corn stalks and wheat straw, were pretreated and hydrolyzed with combined supercritical and subcritical hydrothermal technology. Soluble sugars were collected by pre-washing the crushed materials before hydrolysis. The effects of solid-liquid ratio, temperature, and reaction time on oligosaccharide production were investigated and the optimum supercritical conditions were found to be 20 mg/2.5 ml water, 384 degrees C, 17 s for corn stalks and 20 mg/2.5 ml water, 384 degrees C, 19 s for wheat straw. Subsequent subcritical processing of the hydrolyzate (with or without the water extract) from supercritical treatment was guided by a previous analysis of cellulose hydrolysis kinetics. The highest yield of fermentable hexoses from corn stalks (27.4% of raw material) was obtained at 280 degrees C, 27 s, and from wheat straw (6.7% of raw material) at 280 degrees C, 54 s. This study provides novel key parameters for fermentable hexose production from lignocellulosic feedstocks using combined supercritical and subcritical hydrothermal treatment.

  6. Observation of subcritical geodesic acoustic mode excitation in the large helical device

    NASA Astrophysics Data System (ADS)

    Ido, T.; Itoh, K.; Lesur, M.; Osakabe, M.; Shimizu, A.; Ogawa, K.; Nishiura, M.; Yamada, I.; Yasuhara, R.; Kosuga, Y.; Sasaki, M.; Ida, K.; Inagaki, S.; Itoh, S.-I.; the LHD Experiment Group

    2017-07-01

    The abrupt and strong excitation of the geodesic acoustic mode (GAM) has been found in the large helical device (LHD), when the frequency of a chirping energetic particle-driven GAM (EGAM) approaches twice that of the GAM frequency. The temporal evolution of the phase relation between the abrupt GAM and the chirping EGAM is common in all events. The result indicates a coupling between the GAM and the EGAM. In addition, the nonlinear evolution of the growth rate of the GAM is observed, and there is a threshold in the amplitude of the GAM for the appearance of nonlinear behavior. A threshold in the amplitude of the EGAM for the abrupt excitation of the GAM is also observed. According to one theory (Lesur et al 2016 Phys. Rev. Lett. 116 015003, Itoh et al 2016 Plasma Phys. Rep. 42 418) the observed abrupt phenomenon can be interpreted as the excitation of the subcritical instability of the GAM. The excitation of a subcritical instability requires a trigger and a seed with sufficient amplitude. The observed threshold in the amplitude of the GAM seems to correspond with the threshold in the seed, and the threshold in the amplitude of the EGAM seems to correspond with the threshold in the magnitude of the trigger. Thus, the observed threshold supports the interpretation that the abrupt phenomenon is the excitation of a subcritical instability of the GAM.

  7. Turbulence effect on crossflow around a circular cylinder at subcritical Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Sadeh, W. Z.; Saharon, D. B.

    1982-01-01

    An investigation of the effect of freestream turbulence on the flow around a smooth circular cylinder at subcritical Reynolds numbers from 5.2 x 10 to the 4th power to 2.09 x 10 to the 5th power was conducted. Measurements show that the interaction of incident turbulence with the initial laminar boundary layer: (1) modifies the characteristics of the mean surface pressure distribution; (2) induces an aft shift in the separation point ranging from 5 to 50 beyond the laminar separation angle of 80 degrees; and, (3) reduces the mean drag coefficient to values between 97 and 46% of its nearly constant laminar counterpart. The extent of these changes depends on the particular Reynolds number background turbulence combination. These results demonstrate that a boundary-layer flow similar to that found in critical, supercritical and/or transcritical flow regimes is induced by turbulence at subcritical Reynolds numbers and, hence, the effect of turbulence is equivalent to an effective increase in the Reynolds number. The change in the nature and properties of the boundary layer in the subcritical regime, consequent upon the penetration of turbulence into it, is in agreement with the model proposed by the vorticity-amplification theory.

  8. Efficiency comparison of subcritical OTEC power cycle using various working fluids

    NASA Astrophysics Data System (ADS)

    Yoon, Jung-In; Son, Chang-Hyo; Baek, Seung-Moon; Kim, Hyeon-Ju; Lee, Ho-Saeng

    2014-07-01

    This paper presents an investigation into the thermal efficiency and main component size of the subcritical ocean thermal energy conversion (OTEC) power cycle using various working fluids under different operation conditions. The analysis procedure was performed with a simulation program written in Engineering Equation Solver. With the given analysis conditions, efficiencies of three types of working fluids were evaluated and compared. It was found that the thermal efficiencies of the subcritical OTEC power cycle depend strongly on the evaporating and condensing temperature, and turbine efficiency, while not roughly depending on superheating degrees and pump efficiencies. With a thorough grasp of these results, an efficient OTEC power cycle can be designed. R717 and R404A yielded the highest and lowest thermal efficiencies among the wet fluids, and R22 showed the largest efficiency among the dry fluids. For the iso-entropic fluids, R245fa provided the highest thermal efficiency. In comparison of main component sizes, R404A and R744 had the largest and smallest condenser size, respectively. Also, R744 exhibited the smallest evaporator size, and R404A and R227ea show the largest size. And R744 and R245fa gave the largest and smallest pump size, respectively. From the results of thermal efficiency and main components for various working fluids in the OTEC power cycle, R717 in the subcritical OTEC power cycle is the preferred working fluid, except for its toxicity and flammability.

  9. Nuclear Reactors. Revised.

    ERIC Educational Resources Information Center

    Hogerton, John F.

    This publication is one of a series of information booklets for the general public published by the United States Atomic Energy Commission. Among the topics discussed are: How Reactors Work; Reactor Design; Research, Teaching, and Materials Testing; Reactors (Research, Teaching and Materials); Production Reactors; Reactors for Electric Power…

  10. A Basic LEGO Reactor Design for the Provision of Lunar Surface Power

    SciTech Connect

    John Darrell Bess

    2008-06-01

    A final design has been established for a basic Lunar Evolutionary Growth-Optimized (LEGO) Reactor using current and near-term technologies. The LEGO Reactor is a modular, fast-fission, heatpipe-cooled, clustered-reactor system for lunar-surface power generation. The reactor is divided into subcritical units that can be safely launched with lunar shipments from Earth, and then emplaced directly into holes drilled into the lunar regolith to form a critical reactor assembly. The regolith would not just provide radiation shielding, but serve as neutron-reflector material as well. The reactor subunits are to be manufactured using proven and tested materials for use in radiation environments, such as uranium-dioxide fuel, stainless-steel cladding and structural support, and liquid-sodium heatpipes. The LEGO Reactor system promotes reliability, safety, and ease of manufacture and testing at the cost of an increase in launch mass per overall rated power level and a reduction in neutron economy when compared to a single-reactor system. A single unshielded LEGO Reactor subunit has an estimated mass of approximately 448 kg and provides approximately 5 kWe. The overall envelope for a single subunit with fully extended radiator panels has a height of 8.77 m and a diameter of 0.50 m. Six subunits could provide sufficient power generation throughout the initial stages of establishing a lunar outpost. Portions of the reactor may be neutronically decoupled to allow for reduced power production during unmanned periods of base operations. During later stages of lunar-base development, additional subunits may be emplaced and coupled into the existing LEGO Reactor network, subject to lunar base power demand. Improvements in reactor control methods, fuel form and matrix, shielding, as well as power conversion and heat rejection techniques can help generate an even more competitive LEGO Reactor design. Further modifications in the design could provide power generative opportunities for

  11. Nuclear reactor

    DOEpatents

    Pennell, William E.; Rowan, William J.

    1977-01-01

    A nuclear reactor in which the core components, including fuel-rod assemblies, control-rod assemblies, fertile rod-assemblies, and removable shielding assemblies, are supported by a plurality of separate inlet modular units. These units are referred to as inlet module units to distinguish them from the modules of the upper internals of the reactor. The modular units are supported, each removable independently of the others, in liners in the supporting structure for the lower internals of the reactor. The core assemblies are removably supported in integral receptacles or sockets of the modular units. The liners, units, sockets and assmblies have inlet openings for entry of the fluid. The modular units are each removably mounted in the liners with fluid seals interposed between the opening in the liner and inlet module into which the fluid enters and the upper and lower portion of the liner. Each assembly is similarly mounted in a corresponding receptacle with fluid seals interposed between the openings where the fluid enters and the lower portion of the receptacle or fitting closely in these regions. As fluid flows along each core assembly a pressure drop is produced along the fluid so that the fluid which emerges from each core assembly is at a lower pressure than the fluid which enters the core assembly. However because of the seals interposed in the mountings of the units and assemblies the pressures above and below the units and assemblies are balanced and the units are held in the liners and the assemblies are held in the receptacles by their weights as they have a higher specific gravity than the fluid. The low-pressure spaces between each module and its liner and between each core assembly and its module is vented to the low-pressure regions of the vessel to assure that fluid which leaks through the seals does not accumulate and destroy the hydraulic balance.

  12. NUCLEAR REACTORS

    DOEpatents

    Long, E.; Ashley, J.W.

    1958-12-16

    A graphite moderator structure is described for a gas-cooled nuclear reactor having a vertical orlentation wherein the structure is physically stable with regard to dlmensional changes due to Wigner growth properties of the graphite, and leakage of coolant gas along spaces in the structure is reduced. The structure is comprised of stacks of unlform right prismatic graphite blocks positioned in layers extending in the direction of the lengths of the blocks, the adjacent end faces of the blocks being separated by pairs of tiles. The blocks and tiles have central bores which are in alignment when assembled and are provided with cooperatlng keys and keyways for physical stability.

  13. ELECTRONUCLEAR REACTOR

    DOEpatents

    Lawrence, E.O.; McMillan, E.M.; Alvarez, L.W.

    1960-04-19

    An electronuclear reactor is described in which a very high-energy particle accelerator is employed with appropriate target structure to produce an artificially produced material in commercial quantities by nuclear transformations. The principal novelty resides in the combination of an accelerator with a target for converting the accelerator beam to copious quantities of low-energy neutrons for absorption in a lattice of fertile material and moderator. The fertile material of the lattice is converted by neutron absorption reactions to an artificially produced material, e.g., plutonium, where depleted uranium is utilized as the fertile material.

  14. REACTOR COMPONETN

    DOEpatents

    Creutz, E.C.

    1959-10-27

    A reactor fuel element comprised of a slug of fissionable material disposed in a sheath of corrosion resistantmaterial is described. The sheath is in the form of a tubular container closed at one end and is in tight-fitting engagement with the peripheral sunface of the slug. An inner cap is insented into the open end of the sheath against the slug, which end is then bent around the inner cap and welded thereto. An outer cap is then welded around its peripheny to the bent portion of the container.

  15. Photocatalytic reactor

    DOEpatents

    Bischoff, B.L.; Fain, D.E.; Stockdale, J.A.D.

    1999-01-19

    A photocatalytic reactor is described for processing selected reactants from a fluid medium comprising at least one permeable photocatalytic membrane having a photocatalytic material. The material forms an area of chemically active sites when illuminated by light at selected wavelengths. When the fluid medium is passed through the illuminated membrane, the reactants are processed at these sites separating the processed fluid from the unprocessed fluid. A light source is provided and a light transmitting means, including an optical fiber, for transmitting light from the light source to the membrane. 4 figs.

  16. Hybrid adsorptive membrane reactor

    NASA Technical Reports Server (NTRS)

    Tsotsis, Theodore T. (Inventor); Sahimi, Muhammad (Inventor); Fayyaz-Najafi, Babak (Inventor); Harale, Aadesh (Inventor); Park, Byoung-Gi (Inventor); Liu, Paul K. T. (Inventor)

    2011-01-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  17. Hybrid adsorptive membrane reactor

    DOEpatents

    Tsotsis, Theodore T [Huntington Beach, CA; Sahimi, Muhammad [Altadena, CA; Fayyaz-Najafi, Babak [Richmond, CA; Harale, Aadesh [Los Angeles, CA; Park, Byoung-Gi [Yeosu, KR; Liu, Paul K. T. [Lafayette Hill, PA

    2011-03-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  18. Updated Generation IV Reactors Integrated Materials Technology Program Plan, Revision 2

    SciTech Connect

    Corwin, William R; Burchell, Timothy D; Halsey, William; Hayner, George; Katoh, Yutai; Klett, James William; McGreevy, Timothy E; Nanstad, Randy K; Ren, Weiju; Snead, Lance Lewis; Stoller, Roger E; Wilson, Dane F

    2005-12-01

    The Department of Energy's (DOE's) Generation IV Nuclear Energy Systems Program will address the research and development (R&D) necessary to support next-generation nuclear energy systems. Such R&D will be guided by the technology roadmap developed for the Generation IV International Forum (GIF) over two years with the participation of over 100 experts from the GIF countries. The roadmap evaluated over 100 future systems proposed by researchers around the world. The scope of the R&D described in the roadmap covers the six most promising Generation IV systems. The effort ended in December 2002 with the issue of the final Generation IV Technology Roadmap [1.1]. The six most promising systems identified for next generation nuclear energy are described within the roadmap. Two employ a thermal neutron spectrum with coolants and temperatures that enable hydrogen or electricity production with high efficiency (the Supercritical Water Reactor - SCWR and the Very High Temperature Reactor - VHTR). Three employ a fast neutron spectrum to enable more effective management of actinides through recycling of most components in the discharged fuel (the Gas-cooled Fast Reactor - GFR, the Lead-cooled Fast Reactor - LFR, and the Sodium-cooled Fast Reactor - SFR). The Molten Salt Reactor (MSR) employs a circulating liquid fuel mixture that offers considerable flexibility for recycling actinides, and may provide an alternative to accelerator-driven systems. A few major technologies have been recognized by DOE as necessary to enable the deployment of the next generation of advanced nuclear reactors, including the development and qualification of the structural materials needed to ensure their safe and reliable operation. Accordingly, DOE has identified materials as one of the focus areas for Gen IV technology development.

  19. Control Means for Reactor

    DOEpatents

    Manley, J. H.

    1961-06-27

    An apparatus for controlling a nuclear reactor includes a tank just below the reactor, tubes extending from the tank into the reactor, and a thermally expansible liquid neutron absorbent material in the tank. The liquid in the tank is exposed to a beam of neutrons from the reactor which heats the liquid causing it to expand into the reactor when the neutron flux in the reactor rises above a predetermincd danger point. Boron triamine may be used for this purpose.

  20. Oxidative degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) in subcritical and supercritical waters.

    PubMed

    Hashimoto, M; Taniguchi, S; Takanami, R; Giri, R R; Ozaki, H

    2010-01-01

    Presence of chlorinated organic compounds in water bodies has become a concern among governments, health authorities and general public. Oxidation of organic compounds in water under high temperature and pressure is considered as a promising technique, but usefulness of the technique to mineralize 2,4-dichlorophenoxyacetic acid (2,4-D) is not well understood. This article aimed to elucidate degradation characteristics of 2,4-D in both subcritical and supercritical waters by laboratory batch experiments. 2,4-D degradation, total organic carbon (TOC) removal and dechlorination increased with increasing reaction time and temperature especially in subcritical waters, while dechlorination was a major step. 2,4-dichlorophenol (2,4-DCP) and acetic acid were the main degradation intermediates both in subcritical and supercritical waters. Though 2,4-D disappeared almost completely in subcritical waters near critical region ( approximately 99%), significant amounts of TOC and organic chlorine still remained as 2,4-DCP and acetic acid. But TOC removal and dechlorination were significantly enhanced ( approximately 95 and 91% respectively) in supercritical waters. Complete mineralization of 2,4-D in subcritical waters required a considerably longer reaction period, while the mineralization was almost complete within a short reaction period in supercritical waters. This is an important information of practical significance for oxidative degradation of chlorinated pesticides similar to 2,4-D.

  1. NEUTRONIC REACTOR

    DOEpatents

    Stewart, H.B.

    1958-12-23

    A nuclear reactor of the type speclfically designed for the irradiation of materials is discussed. In this design a central cyllndrical core of moderating material ls surrounded by an active portlon comprlsed of an annular tank contalning fissionable material immersed ln a liquid moderator. The active portion ls ln turn surrounded by a reflector, and a well ls provided in the center of the core to accommodate the materlals to be irradiated. The over-all dimensions of the core ln at least one plane are equal to or greater than twice the effective slowing down length and equal to or less than twlce the effective diffuslon length for neutrons in the core materials.

  2. NEUTRONIC REACTOR

    DOEpatents

    Daniels, F.

    1962-12-18

    A power plant is described comprising a turbine and employing round cylindrical fuel rods formed of BeO and UO/sub 2/ and stacks of hexagonal moderator blocks of BeO provided with passages that loosely receive the fuel rods so that coolant may flow through the passages over the fuels to remove heat. The coolant may be helium or steam and fiows through at least one more heat exchanger for producing vapor from a body of fluid separate from the coolant, which fluid is to drive the turbine for generating electricity. By this arrangement the turbine and directly associated parts are free of particles and radiations emanating from the reactor. (AEC)

  3. NEUTRONIC REACTOR

    DOEpatents

    McGarry, R.J.

    1958-04-22

    Fluid-cooled nuclear reactors of the type that utilize finned uranium fuel elements disposed in coolant channels in a moderater are described. The coolant channels are provided with removable bushings composed of a non- fissionable material. The interior walls of the bushings have a plurality of spaced, longtudinal ribs separated by grooves which receive the fins on the fuel elements. The lands between the grooves are spaced from the fuel elements to form flow passages, and the size of the now passages progressively decreases as the dlstance from the center of the core increases for the purpose of producing a greater cooling effect at the center to maintain a uniform temperature throughout the core.

  4. Nuclear fuel cycle analysis of the SABR fusion-fission hybrid transmutation reactor

    NASA Astrophysics Data System (ADS)

    Sommer, Chris; Stacey, Weston; Petrovic, Bojan

    2009-11-01

    Various fuel cycles have been designed and analyzed for the Subcritical Advanced Burner Reactor (SABR). SABR is a sodium cooled fast reactor fueled with transuranics (TRU) from spent fuel of light water reactors and driven by a tokamak fusion neutron source based on ITER physics and technology. SABR employs a four batch fuel cycle using an out-to-in shuffling pattern, with the fuel being reprocessed at the end of each cycle. The reprocessing method assumes recovery rates of 99.9% of the actinides and 0.1% of the fission products remain in the recycled fuel. The reprocessing fuel cycles were analyzed to find an optimal cycle length in terms of burn up, power distribution, and materials limitations. Fuel cycles are analyzed using CEA's ERANOS2.0 code, with fuel residence times limited by radiation damage at 100, 150 and 200 dpa.

  5. Methods for modeling impact-induced reactivity changes in small reactors.

    SciTech Connect

    Tallman, Tyler N.; Radel, Tracy E.; Smith, Jeffrey A.; Villa, Daniel L.; Smith, Brandon M.; Radel, Ross F.; Lipinski, Ronald J.; Wilson, Paul Philip Hood

    2010-10-01

    This paper describes techniques for determining impact deformation and the subsequent reactivity change for a space reactor impacting the ground following a potential launch accident or for large fuel bundles in a shipping container following an accident. This technique could be used to determine the margin of subcriticality for such potential accidents. Specifically, the approach couples a finite element continuum mechanics model (Pronto3D or Presto) with a neutronics code (MCNP). DAGMC, developed at the University of Wisconsin-Madison, is used to enable MCNP geometric queries to be performed using Pronto3D output. This paper summarizes what has been done historically for reactor launch analysis, describes the impact criticality analysis methodology, and presents preliminary results using representative reactor designs.

  6. Nuclear reactor neutron shielding

    DOEpatents

    Speaker, Daniel P; Neeley, Gary W; Inman, James B

    2017-09-12

    A nuclear reactor includes a reactor pressure vessel and a nuclear reactor core comprising fissile material disposed in a lower portion of the reactor pressure vessel. The lower portion of the reactor pressure vessel is disposed in a reactor cavity. An annular neutron stop is located at an elevation above the uppermost elevation of the nuclear reactor core. The annular neutron stop comprises neutron absorbing material filling an annular gap between the reactor pressure vessel and the wall of the reactor cavity. The annular neutron stop may comprise an outer neutron stop ring attached to the wall of the reactor cavity, and an inner neutron stop ring attached to the reactor pressure vessel. An excore instrument guide tube penetrates through the annular neutron stop, and a neutron plug comprising neutron absorbing material is disposed in the tube at the penetration through the neutron stop.

  7. Burning high-level TRU waste in fusion fission reactors

    NASA Astrophysics Data System (ADS)

    Shen, Yaosong

    2016-09-01

    Recently, the concept of actinide burning instead of a once-through fuel cycle for disposing spent nuclear fuel seems to get much more attention. A new method of burning high-level transuranic (TRU) waste combined with Thorium-Uranium (Th-U) fuel in the subcritical reactors driven by external fusion neutron sources is proposed in this paper. The thorium-based TRU fuel burns all of the long-lived actinides via a hard neutron spectrum while outputting power. A one-dimensional model of the reactor concept was built by means of the ONESN_BURN code with new data libraries. The numerical results included actinide radioactivity, biological hazard potential, and much higher burnup rate of high-level transuranic waste. The comparison of the fusion-fission reactor with the thermal reactor shows that the harder neutron spectrum is more efficient than the soft. The Th-U cycle produces less TRU, less radiotoxicity and fewer long-lived actinides. The Th-U cycle provides breeding of 233U with a long operation time (>20 years), hence significantly reducing the reactivity swing while improving safety and burnup.

  8. Reactor and method of operation

    DOEpatents

    Wheeler, John A.

    1976-08-10

    A nuclear reactor having a flattened reactor activity curve across the reactor includes fuel extending over a lesser portion of the fuel channels in the central portion of the reactor than in the remainder of the reactor.

  9. Nuclear reactor

    DOEpatents

    Yant, Howard W.; Stinebiser, Karl W.; Anzur, Gregory C.

    1977-01-01

    A nuclear reactor, particularly a liquid-metal breeder reactor, whose upper internals include outlet modules for channeling the liquid-metal coolant from selected areas of the outlet of the core vertically to the outlet plenum. The modules are composed of a highly-refractory, high corrosion-resistant alloy, for example, INCONEL-718. Each module is disposed to confine and channel generally vertically the coolant emitted from a subplurality of core-component assemblies. Each module has a grid with openings, each opening disposed to receive the coolant from an assembly of the subplurality. The grid in addition serves as a holdown for the assemblies of the corresponding subplurality preventing their excessive ejection upwardly from the core. In the region directly over the core the outlet modules are of such peripheral form that they nest forming a continuum over the core-component assemblies whose outlet coolant they confine. Each subassembly includes a chimney which confines the coolant emitted by its corresponding subassemblies to generally vertical flow between the outlet of the core and the outlet plenum. Each subplurality of assemblies whose emitted coolant is confined by an outlet module includes assemblies which emit lower-temperature coolant, for example, a control-rod assembly, or fertile assemblies, and assemblies which emit coolant of substantially higher temperature, for example, fuel-rod assemblies. The coolants of different temperatures are mixed in the chimneys reducing the effect of stripping (hot-cold temperature fluctuations) on the remainder of the upper internals which are composed typically of AISI-304 or AISI-316 stainless steel.

  10. Subcritical and supercritical technology for the production of second generation bioethanol.

    PubMed

    Rostagno, Mauricio A; Prado, Juliana M; Mudhoo, Ackmez; Santos, Diego T; Forster-Carneiro, Tânia; Meireles, M Angela A

    2015-01-01

    There is increased interest in reducing our reliance on fossil fuels and increasing the share of renewable raw materials in our energy supply chain due to environmental and economic concerns. Ethanol is emerging as a potential alternative to liquid fuels due to its eco-friendly characteristics and relatively low production costs. As ethanol is currently produced from commodities also used for human and animal consumption, there is an urgent need of identifying renewable raw materials that do not pose a competitive problem. Lignocellulosic agricultural residues are an ideal choice since they can be effectively hydrolyzed to fermentable sugars and integrated in the context of a biorefinery without competing with the food supply chain. However, the conventional hydrolysis methods still have major issues that need to be addressed. These issues are related to the processing rate and generation of fermentation inhibitors, which can compromise the quality of the product and the cost of the process. As the knowledge of the processes taking place during hydrolysis of agricultural residues is increasing, new techniques are being exploited to overcome these drawbacks. This review gives an overview of the state-of-the-art of hydrolysis with subcritical and supercritical water in the context of reusing agricultural residues for the production of suitable substrates to be processed during the fermentative production of bioethanol. Presently, subcritical and/or supercritical water hydrolysis has been found to yield low sugar contents mainly due to concurrent competing degradation of sugars during the hydrothermal processes. In this line of thinking, the present review also revisits the recent applications and advances to provide an insight of future research trends to optimize on the subcritical and supercritical process kinetics.

  11. Surface chemistry and corrosion behavior of Inconel 625 and 718 in subcritical, supercritical, and ultrasupercritical water

    NASA Astrophysics Data System (ADS)

    Rodriguez, David; Merwin, Augustus; Karmiol, Zachary; Chidambaram, Dev

    2017-05-01

    Corrosion behavior of Inconel 625 and 718 in subcritical, supercritical and ultrasupercritical water was studied as a function of temperature and time. The change in the chemistry of the as-received surface film on Inconel 625 and 718 after exposure to subcritical water at 325 °C and supercritical water at 425 °C and 527.5 °C for 2 h was studied. After exposure to 325 °C subcritical water, the CrO42- based film formed; however minor quantities of NiFexCr2-xO4 spinel compounds were observed. The oxide film formed on both alloys when exposed to supercritical water at 425 °C consisted of NiFexCr2-xO4 spinel. The surface films on both alloys were identified as NiFe2O4 when exposed to supercritical water at 527.5 °C. To characterize the fully developed oxide layer, studies were conducted at test solution temperatures of 527.5 and 600 °C. Samples were exposed to these temperatures for 24, 96, and 200 h. Surface chemistry was analyzed using X-ray diffraction, as well as Raman and X-ray photoelectron spectroscopies. Inconel 718 exhibited greater mass gain than Inconel 625 for all temperatures and exposure times. The differences in corrosion behavior of the two alloys are attributed to the lower content of chromium and increased iron content of Inconel 718 as compared to Inconel 625.

  12. Conversion of Japanese red pine wood (Pinus densiflora) into valuable chemicals under subcritical water conditions.

    PubMed

    Asghari, Feridoun Salak; Yoshida, Hiroyuki

    2010-01-11

    A comparative study on the decomposition of Japanese red pine wood under subcritical water conditions in the presence and absence of phosphate buffer was investigated in a batch-type reaction vessel. Since cellulose makes up more than 40-45% of the components found in most wood species, a series of experiments were also carried out using pure cellulose as a model for woody biomass. Several parameters such as temperature and residence time, as well as pH effects, were investigated in detail. The best temperature for decomposition and hydrolysis of pure cellulose was found around 270 degrees C. The effects of the initial pH of the solution which ranged from 1.5 to 6.5 were studied. It was found that the pH has a considerable effect on the hydrolysis and decomposition of the cellulose. Several products in the aqueous phase were identified and quantified. The conditions obtained from the subcritical water treatment of pure cellulose were applied for the Japanese red pine wood chips. As a result, even in the absence of acid catalyst, a large amount of wood sample was hydrolyzed in water; however, by using phosphate buffer at pH 2, there was an increase in the hydrolysis and dissolution of the wood chips. In addition to the water-soluble phase, acetone-soluble and water-acetone-insoluble phases were also isolated after subcritical water treatment (which can be attributed mainly to the degraded lignin, tar, and unreacted wood chips, respectively). The initial wood:acid ratio in the case of reactions catalyzed by phosphate buffer was also investigated. The results showed that this weight ratio can be as high as 3:1 without changing the catalytic activity. The size of the wood chips as one of the most important experimental parameters was also investigated.

  13. PRACTICAL APPLICATION OF THE SINGLE-PARAMETER SUBCRITICAL MASS LIMIT FOR PLUTONIUM METAL

    SciTech Connect

    MITCHELL, MARK VON

    2007-01-10

    According to ANS-8.1, operations with fissile materials can be performed safely by complying with any of the listed single-parameter subcritical limits. For metallic units, when interspersed moderators are present, the mass limits apply to a single piece having no concave surfaces. On a practical level, when has any operation with fissile metal involved a single piece and absolutely no moderating material, e.g., water, oil, plastic, etc.? This would be rare. This paper explores the application of the single-parameter plutonium metal mass limit for realistic operational environments.

  14. Simple No-Go Test for Subcritical Damage in Body Armor Panels

    NASA Astrophysics Data System (ADS)

    Fisher, Jason; Chimenti, D. E.

    2011-06-01

    The development of a simple test for subcritical damage in body armor panels using pressure-sensitive dye-indicator film has been performed and demonstrated effective. Measurements have shown that static indicator levels are accurately reproduced in dynamic loading events. Impacts from hard blunt impactors instrumented with an accelerometer and embedded force transducer were studied. Reliable correlations between the indicator film and instrumented impact force are shown for a range of impact energies. Force and acceleration waveforms with corresponding indicator film results are presented for impact events onto damaged and undamaged panels. We find that panel damage can occur at impact levels far below the National Institute of Justice acceptance test standard.

  15. Subcritical and supercritical fuel injection and mixing in single and binary species systems

    NASA Astrophysics Data System (ADS)

    Roy, Arnab

    Subcritical and supercritical fluid injection using a single round injector into a quiescent atmosphere comprising single and binary species was investigated using optical diagnostics. Different disintegration and mixing modes are expected for the two cases. In the binary species case, the atmosphere comprised an inert gas of a different composition than that of the injected fluid. In single species case, the atmosphere consisted of the same species as that of the injected fluid. Density values were quantified and density gradient profiles were inferred from the experimental data. A novel method was applied for the detection of detailed structures throughout the entire jet center plane. Various combinations of injectant and chamber conditions were tested and a wide range of density ratios were covered. The subcritical cases demonstrated the importance of surface tension and inertial forces, while the supercritical cases showed no signs of surface tension and, in most situations, resembled the mixing characteristics of a gaseous jet injected into a gaseous environment. A comparison between the single and binary species systems has also been provided. A detailed laser calibration procedure was undertaken to account for the laser absorption through the gas and liquid phases and for fluorescence in the non-linear excitation regime for high laser pulse energy. Core lengths were measured for binary species cases and correlated with visualization results. An eigenvalue approach was taken to determine the location of maximum gradients for determining the core length. Jet divergence angles were also calculated and were found to increase with chamber-to-injectant density ratio for both systems. A model was proposed for the spreading angle dependence on density ratio for both single and binary species systems and was compared to existing theoretical studies and experimental work. Finally, a linear stability analysis was performed for the jet injected into both subcritical and

  16. Simple go/no-go test for subcritical damage in body armor panels

    SciTech Connect

    Fisher, Jason; Chimenti, D. E.

    2011-06-23

    The development of a simple test for subcritical damage in body armor panels using pressure-sensitive dye-indicator film has been performed and demonstrated effective. Measurements have shown that static indicator levels are accurately reproduced in dynamic loading events. Impacts from hard blunt impactors instrumented with an accelerometer and embedded force transducer were studied. Reliable correlations between the indicator film and instrumented impact force are shown for a range of impact energies. Force and acceleration waveforms with corresponding indicator film results are presented for impact events onto damaged and undamaged panels. We find that panel damage can occur at impact levels far below the National Institute of Justice acceptance test standard.

  17. Subcritical flow past a circular cylinder surrounded by a porous layer

    NASA Astrophysics Data System (ADS)

    Sobera, M. P.; Kleijn, C. R.; Van den Akker, H. E. A.

    2006-03-01

    A study of the flow at subcritical Re =3900 around a circular cylinder, surrounded at some fixed small distance by a porous layer with a hydraulic resistance typical for that of textile materials, has been performed by means of direct numerical simulations. The flow in the space between the porous layer and the solid cylinder was found to be laminar and periodic, with a frequency locked to that of the vortex shedding in the wake behind the cylinder. Time averaged flow velocities underneath the porous material were in good agreement with experimental data from laser Doppler anemometry.

  18. Subcritical microwave streamer discharge at the surface of a polymer foil

    NASA Astrophysics Data System (ADS)

    Popovic, S.; Vuskovic, L.; Esakov, I. I.; Gratchev, L. P.; Khodataev, K. V.

    2002-09-01

    An innovative type of subcritical streamer discharge, generated by bursts of focused microwave (MW) radiation in transverse electromagnetic mode with wavelength of 10 cm, pulse duration of 40 mus, and intensity of 5.6 x104 W/cm2, was initiated at the surface of a polymer foil at 420 Torr in air. The MW field of a quasioptical beam was three times lower than the critical breakdown field. Exposure of a polymer foil to the discharge caused a transition from hydrophobicity to hydrophilicity.

  19. Reactor safety method

    DOEpatents

    Vachon, Lawrence J.

    1980-03-11

    This invention relates to safety means for preventing a gas cooled nuclear reactor from attaining criticality prior to start up in the event the reactor core is immersed in hydrogenous liquid. This is accomplished by coating the inside surface of the reactor coolant channels with a neutral absorbing material that will vaporize at the reactor's operating temperature.

  20. Subcritical crack-growth behavior of borosilicate glass under cyclic loads: Evidence of a mechanical fatigue effect

    SciTech Connect

    Dill, S.J.; Dauskardt, R.H.; Bennison, S.J.

    1997-03-01

    Amorphous glasses are generally considered immune to mechanical fatigue effects associated with cyclic loading. In this study surprising new evidence is presented for a mechanical fatigue effect in borosilicate glass, in both moist air and dry nitrogen environments. The fatigue effect occurs at near threshold subcritical crack-growth rates (da/dt < 3 {times} 10{sup {minus}8} m/s) as the crack extension per cycle approaches the dimensions of the borosilicate glass network. While subcritical crack growth under cyclic loads at higher load levels is entirely consistent with environmentally assisted crack growth, lower growth rates actually exceed those measured under monotonic loads. This suggests a mechanical fatigue effect which accelerates subcritical crack-growth rates. Likely mechanisms for the mechanical fatigue effect are presented.

  1. A study of the effect of subcritical crack growth on the geometry dependence on nonlinear fracture toughness parameters

    NASA Technical Reports Server (NTRS)

    Jones, D. L.; Poulose, P. K.; Liebowitz, H.

    1976-01-01

    The effect of subcritical crack growth on the geometry dependence of nonlinear fracture toughness parameters was studied by comparing the toughness values for different specimen geometries at the onset of subcritical crack growth and at the initiation of unstable crack propagation. Center-cracked thin sheet specimens of 2024-T3 and 7075-T6 aluminum alloys were tested by varying the specimen length L, width w, and crack length-to-width ratio c/w. When the onset of unstable crack propagation was selected as the critical point, the nonlinear energy toughness and the R curve toughness increased with increasing w and decreasing L and c/w. However, when the onset of subcritical crack growth was taken as the critical point, energy toughness and the linear toughness values were independent of these geometrical variables.

  2. The 5 kWe scale-down of the SPAR/SP-100 heat pipe reactor

    NASA Astrophysics Data System (ADS)

    Adrian, John M.; Benke, Steven M.

    The SPAR/SP-100 heat pipe reactor was designed to operate at 100 kWe. Work done on a 5 kWe scaled-down version of the SPAR/SP-100 is presented. This scale-down was done in order to compare the performance of a small heat pipe reactor to Radioisotope Thermoelectric Generators (RTGs). The work on this design is broken into the following categories: reactor core modeling, control drum modeling, heat rejection modeling, and shadow shield modeling. The reactor core modeling will be completed using the already available computer programs FEMP2D and ORIGEN. The REMP2D will be used to complete the neutronics survey through the core and control drums and it will also be used to ensure the core will be subcritical in case of a water abort. Another safety aspect that will be investigated using FEMP2D is ensuring that a fuel element remains subcritical in the event of reactor break-up during reentry. The ORIGEN wil be used to check the burn-up characteristics of the core design. The reactor control drums will be modeled using a FORTRAN program in order to provide atom density information for use in FEMP2D. The heat rejection system will be modeled in order to determine weight requirements of the radiator. The shadow shield model will also provide information on the weight requirements of the shield with respect to the reactor size. The data obtained from the different categories wil be used to compare the performance of a small heat pipe reactor to the RTG. Comparisons will be made in the following areas: specific power, operating characteristics, and safety.

  3. Radiogenic lead as coolant, reflector and moderator in advanced fast reactors

    NASA Astrophysics Data System (ADS)

    Kulikov, E. G.

    2017-01-01

    Main purpose of the study is assessing reasonability for recovery, production and application of radiogenic lead as a coolant, neutron moderator and neutron reflector in advanced fast reactors. When performing the study, thermal, physical and neutron-physical properties of natural and radiogenic lead were analyzed. The following results were obtained: 1. Radiogenic lead with high content of isotope 208Pb can be extracted from thorium or mixed thorium-uranium ores because 208Pb is a final product of 232Th natural decay chain. 2. The use of radiogenic lead with high 208Pb content in advanced fast reactors and accelerator-driven systems (ADS) makes it possible to improve significantly their neutron-physical and thermal-hydraulic parameters. 3. The use of radiogenic lead with high 208Pb content in advanced fast reactors as a coolant opens the possibilities for more intense fuel breeding and for application of well-known oxide fuel instead of the promising but not tested enough nitride fuel under the same safety parameters. 4. The use of radiogenic lead with high 208Pb content in ADS as a coolant can upgrade substantially the level of neutron flux in the ADS blanket, which enables effective transmutation of radioactive wastes with low cross-sections of radiative neutron capture.

  4. Nuclear reactor

    DOEpatents

    Thomson, Wallace B.

    2004-03-16

    A nuclear reactor comprising a cylindrical pressure vessel, an elongated annular core centrally disposed within and spaced from the pressure vessel, and a plurality of ducts disposed longitudinally of the pressure vessel about the periphery thereof, said core comprising an annular active portion, an annular reflector just inside the active portion, and an annular reflector just outside the active a portion, said annular active portion comprising rectangular slab, porous fuel elements radially disposed around the inner reflector and extending the length of the active portion, wedge-shaped, porous moderator elements disposed adjacent one face of each fuel element and extending the length of the fuel element, the fuel and moderator elements being oriented so that the fuel elements face each other and the moderator elements do likewise, adjacent moderator elements being spaced to provide air inlet channels, and adjacent fuel elements being spaced to provide air outlet channels which communicate with the interior of the peripheral ducts, and means for introducing air into the air inlet channels which passes through the porous moderator elements and porous fuel elements to the outlet channel.

  5. Final Progress Report: FRACTURE AND SUBCRITICAL DEBONDING IN THIN LAYERED STRUCTURES: EXPERIMENTS AND MULTI-SCALE MODELING

    SciTech Connect

    Reinhold H. Dauskardt

    2005-08-30

    Final technical report detailing unique experimental and multi-scale computational modeling capabilities developed to study fracture and subcritical cracking in thin-film structures. Our program to date at Stanford has studied the mechanisms of fracture and fatigue crack-growth in structural ceramics at high temperature, bulk and thin-film glasses in selected moist environments where we demonstrated the presence of a true mechanical fatigue effect in some glass compositions. We also reported on the effects of complex environments and fatigue loading on subcritical cracking that effects the reliability of MEMS and other micro-devices using novel micro-machined silicon specimens and nanomaterial layers.

  6. Subcritical convection of liquid metals in a rotating sphere using a quasi-geostrophic model

    NASA Astrophysics Data System (ADS)

    Guervilly, Céline; Cardin, Philippe

    2016-12-01

    We study nonlinear convection in a rapidly rotating sphere with internal heating for values of the Prandtl number relevant for liquid metals ($Pr\\in[10^{-2},10^{-1}]$). We use a numerical model based on the quasi-geostrophic approximation, in which variations of the axial vorticity along the rotation axis are neglected, whereas the temperature field is fully three-dimensional. We identify two separate branches of convection close to onset: (i) a well-known weak branch for Ekman numbers greater than $10^{-6}$, which is continuous at the onset (supercritical bifurcation) and consists of thermal Rossby waves, and (ii) a novel strong branch at lower Ekman numbers, which is discontinuous at the onset. The strong branch becomes subcritical for Ekman numbers of the order of $10^{-8}$. On the strong branch, the Reynolds number of the flow is greater than $10^3$, and a strong zonal flow with multiple jets develops, even close to the nonlinear onset of convection. We find that the subcriticality is amplified by decreasing the Prandtl number. The two branches can co-exist for intermediate Ekman numbers, leading to hysteresis ($Ek=10^{-6}$, $Pr=10^{-2}$). Nonlinear oscillations are observed near the onset of convection for $Ek=10^{-7}$ and $Pr=10^{-1}$.

  7. Subcritical thermal convection of liquid metals in a rotating sphere using a quasi-geostrophic model

    NASA Astrophysics Data System (ADS)

    Cardin, P.; Guervilly, C.

    2016-12-01

    We study non-linear convection in a rapidly rotating sphere with internal heating for values of the Prandtl number relevant for liquid metals (10-2-1). We use a numerical model based on the quasi-geostrophic approximation, in which variations of the axial vorticity along the rotation axis are neglected, whereas the temperature field is fully three-dimensional. We identify two separate branches of convection close to onset: (i) a well-known weak branch for Ekman numbers greater than 10-6, which is continuous at the onset (supercritical bifurcation) and consists of the interaction of thermal Rossby waves, and (ii) a novel strong branch at lower Ekman numbers, which is discontinuous at the onset. The strong branch becomes subcritical for Ekman numbers of the order of 10-8. On the strong branch, the Reynolds number of the flow is greater than 1000, and a strong zonal flow with multiple jets develops, even close to the non-linear onset of convection. We find that the subcriticality is amplified by decreasing the Prandtl number. The two branches can co-exist for intermediate Ekman numbers, leading to hysteresis (E = 10-6, Pr =10-2). Non-linear oscillations are observed near the onset of convection for E = 10-7 and Pr = 10-1.

  8. Functional properties and structure changes of soybean protein isolate after subcritical water treatment.

    PubMed

    Zhang, Qiu-Ting; Tu, Zong-Cai; Wang, Hui; Huang, Xiao-Qin; Fan, Liang-Liang; Bao, Zhong-Yu; Xiao, Hui

    2015-06-01

    Subcritical water is an emerging method in food industry. In this study, soybean protein isolate (SPI) was treated by subcritical water (SBW) at various temperatures (0, 120, 160, 200 °C) for 20 min. The changes in the appearances, physicochemical properties and structural changes were investigated. After SBW treatment, the color of SPI solution modified turned to be yellow. The mean particle size and turbidity of SPI had similar behaviors. The mean particle size was decreased from 263.7 nm to 116.8 nm at 120 °C and then reached the maximum at 160 °C (1446.1 nm) due to the aggregation of protein. Then it was decreased to 722.9 nm at 200 °C caused by the protein degradation. SBW treatment could significantly enhance the solubility, emulsifying and foaming properties of SPI. With increasing temperature, the crystalline structure of protein was gradually collapsed. The degradation of the protein advanced structure occurred, especially at 200 °C revealed by ultra-high resolution mass spectrometry. Better functional properties exhibited in hydrolysis products indicating that SBW treatment could be used as a good method to modify the properties of soy proteins isolate for specific purposes under appropriate treatment condition.

  9. Ultrasound-Enhanced Subcritical CO2 Extraction of Lutein from Chlorella pyrenoidosa.

    PubMed

    Fan, Xiao-Dan; Hou, Yan; Huang, Xing-Xin; Qiu, Tai-Qiu; Jiang, Jian-Guo

    2015-05-13

    Lutein is an important pigment of Chlorella pyrenoidosa with many beneficial functions in human health. The main purpose of this study was to extract lutein from C. pyrenoidosa using ultrasound-enhanced subcritical CO2 extraction (USCCE). Effects of operating conditions on the extraction, including extraction pretreatment, temperature, pressure, time, CO2 flow rate, and ultrasonic power, were investigated, and an orthogonal experiment was designed to study the effects of extraction pressure, temperature, cosolvent amount, and time on the extraction yields. The USCCE method was compared with other extraction methods in terms of the yields of lutein and the microstructure of C. pyrenoidosa powder by scanning electron microscopy. A maximal extraction yield of 124.01 mg lutein/100 g crude material was achieved under optimal conditions of extraction temperature at 27 °C, extraction pressure at 21 MPa, cosolvent amount at 1.5 mL/g ethanol, and ultrasound power at 1000 W. Compared to other methods, USCCE could significantly increase the lutein extraction yield at lower extraction temperature and pressure. Furthermore, the kinetic models of USCCE and subcritical CO2 extraction (SCCE) of lutein from C. pyrenoidosa were set as E = 130.64 × (1 - e(-0.6599t)) and E = 101.82 × (1 - e(-0.5683t)), respectively. The differences of parameters in the kinetic models indicate that ultrasound was able to enhance the extraction process of SCCE.

  10. Initial instability of round liquid jet at subcritical and supercritical environments

    SciTech Connect

    Muthukumaran, C. K.; Vaidyanathan, Aravind

    2016-07-15

    In the present experimental work, the behavior of laminar liquid jet in its own vapor as well as supercritical fluid environment is conducted. Also the study of liquid jet injection into nitrogen (N{sub 2}) environment is carried out at supercritical conditions. It is expected that the injected liquid jet would undergo thermodynamic transition to the chamber condition and this would alter the behavior of the injected jet. Moreover at such conditions there is a strong dependence between thermodynamic and fluid dynamic processes. Thus the thermodynamic transition has its effect on the initial instability as well as the breakup nature of the injected liquid jet. In the present study, the interfacial disturbance wavelength, breakup characteristics, and mixing behavior are analysed for the fluoroketone liquid jet that is injected into N{sub 2} environment as well as into its own vapor at subcritical to supercritical conditions. It is observed that at subcritical chamber conditions, the injected liquid jet exhibits classical liquid jet characteristics with Rayleigh breakup at lower Weber number and Taylor breakup at higher Weber number for both N{sub 2} and its own environment. At supercritical chamber conditions with its own environment, the injected liquid jet undergoes sudden thermodynamic transition to chamber conditions and single phase mixing characteristics is observed. However, the supercritical chamber conditions with N{sub 2} as ambient fluid does not have significant effect on the thermodynamic transition of the injected liquid jet.

  11. Vacuum ultraviolet spectroscopy of the lowest-lying electronic state in subcritical and supercritical water

    DOE PAGES

    Marin, Timothy W.; Janik, Ireneusz; Bartels, David M.; ...

    2017-05-17

    The nature and extent of hydrogen bonding in water has been scrutinized for decades, including how it manifests in optical properties. Here we report vacuum ultraviolet absorption spectra for the lowest-lying electronic state of subcritical and supercritical water. For subcritical water, the spectrum redshifts considerably with increasing temperature, demonstrating the gradual breakdown of the hydrogen-bond network. Tuning the density at 381°C gives insight into the extent of hydrogen bonding in supercritical water. The known gas-phase spectrum, including its vibronic structure, is duplicated in the low-density limit. With increasing density, the spectrum blueshifts and the vibronic structure is quenched as themore » water monomer becomes electronically perturbed. Fits to the supercritical water spectra demonstrate consistency with dimer/trimer fractions calculated from the water virial equation of state and equilibrium constants. As a result, using the known water dimer interaction potential, we estimate the critical distance between molecules (ca. 4.5 Å) needed to explain the vibronic structure quenching.« less

  12. Feedback control of transient energy growth in subcritical plane Poiseuille flow

    NASA Astrophysics Data System (ADS)

    Martinelli, Fulvio; Quadrio, Maurizio; McKernan, John; Whidborne, James F.

    Subcritical flows may experience large transient perturbation energy amplifications, that could trigger nonlinear mechanisms and eventually lead to transition to turbulence. In plane Poiseuille flow, controlled via wall blowing/suction with zero net mass flux, optimal and robust control theory has been recently applied to a state-space representation of the Orr-Sommerfeld-Squire equations, leading to reduced transient growth as well as increased transition thresholds. However, to date no feedback control law has been found that is capable of ensuring the closed-loop Poiseuille flow to be monotonically stable. The present paper addresses first the possibility of complete feedback suppression of the transient growth mechanism in subcritical plane Poiseuille flow when wall actuation is available, and demonstrates that closed-loop monotonic stability cannot be achieved in such a case. Secondly, a Linear Matrix Inequality (LMI) technique is employed to design controllers that directly target the energy growth mechanism. The performance of such control laws is quantified by using Direct Numerical Simulations of transitional plane Poiseuille flow, and the increase in transition thresholds due to the control action is assessed.

  13. Subcritical Water Technology for Enhanced Extraction of Biochemical Compounds from Chlorella vulgaris

    PubMed Central

    Awaluddin, S. A.; Thiruvenkadam, Selvakumar; Izhar, Shamsul; Hiroyuki, Yoshida; Danquah, Michael K.; Harun, Razif

    2016-01-01

    Subcritical water extraction (SWE) technology has been used for the extraction of active compounds from different biomass materials with low process cost, mild operating conditions, short process times, and environmental sustainability. With the limited application of the technology to microalgal biomass, this work investigates parametrically the potential of subcritical water for high-yield extraction of biochemicals such as carbohydrates and proteins from microalgal biomass. The SWE process was optimized using central composite design (CCD) under varying process conditions of temperature (180–374°C), extraction time (1–20 min), biomass particulate size (38–250 μm), and microalgal biomass loading (5–40 wt.%). Chlorella vulgaris used in this study shows high volatile matter (83.5 wt.%) and carbon content (47.11 wt.%), giving advantage as a feedstock for biofuel production. The results showed maximum total carbohydrate content and protein yields of 14.2 g/100 g and 31.2 g/100 g, respectively, achieved under the process conditions of 277°C, 5% of microalgal biomass loading, and 5 min extraction time. Statistical analysis revealed that, of all the parameters investigated, temperature is the most critical during SWE of microalgal biomass for protein and carbohydrate production. PMID:27366748

  14. High order statistical signatures from source-driven measurements of subcritical fissile systems

    NASA Astrophysics Data System (ADS)

    Mattingly, John Kelly

    1998-11-01

    This research focuses on the development and application of high order statistical analyses applied to measurements performed with subcritical fissile systems driven by an introduced neutron source. The signatures presented are derived from counting statistics of the introduced source and radiation detectors that observe the response of the fissile system. It is demonstrated that successively higher order counting statistics possess progressively higher sensitivity to reactivity. Consequently, these signatures are more sensitive to changes in the composition, fissile mass, and configuration of the fissile assembly. Furthermore, it is shown that these techniques are capable of distinguishing the response of the fissile system to the introduced source from its response to any internal or inherent sources. This ability combined with the enhanced sensitivity of higher order signatures indicates that these techniques will be of significant utility in a variety of applications. Potential applications include enhanced radiation signature identification of weapons components for nuclear disarmament and safeguards applications and augmented nondestructive analysis of spent nuclear fuel. In general, these techniques expand present capabilities in the analysis of subcritical measurements.

  15. Subcritical Thermal Convection of Liquid Metals in a Rapidly Rotating Sphere

    NASA Astrophysics Data System (ADS)

    Kaplan, E. J.; Schaeffer, N.; Vidal, J.; Cardin, P.

    2017-09-01

    Planetary cores consist of liquid metals (low Prandtl number Pr) that convect as the core cools. Here, we study nonlinear convection in a rotating (low Ekman number Ek) planetary core using a fully 3D direct numerical simulation. Near the critical thermal forcing (Rayleigh number Ra), convection onsets as thermal Rossby waves, but as Ra increases, this state is superseded by one dominated by advection. At moderate rotation, these states (here called the weak branch and strong branch, respectively) are smoothly connected. As the planetary core rotates faster, the smooth transition is replaced by hysteresis cycles and subcriticality until the weak branch disappears entirely and the strong branch onsets in a turbulent state at Ek <10-6. Here, the strong branch persists even as the thermal forcing drops well below the linear onset of convection (Ra =0.7 Racrit in this study). We highlight the importance of the Reynolds stress, which is required for convection to subsist below the linear onset. In addition, the Péclet number is consistently above 10 in the strong branch. We further note the presence of a strong zonal flow that is nonetheless unimportant to the convective state. Our study suggests that, in the asymptotic regime of rapid rotation relevant for planetary interiors, thermal convection of liquid metals in a sphere onsets through a subcritical bifurcation.

  16. Pyrolysis of low density polyethylene waste in subcritical water optimized by response surface methodology.

    PubMed

    Wong, S L; Ngadi, N; Amin, N A S; Abdullah, T A T; Inuwa, I M

    2016-01-01

    Pyrolysis of low density polyethylene (LDPE) waste from local waste separation company in subcritical water was conducted to investigate the effect of reaction time, temperature, as well as the mass ratio of water to polymer on the liquid yield. The data obtained from the study were used to optimize the liquid yield using response surface methodology. The range of reaction temperature used was 162-338°C, while the reaction time ranged from 37 min to 143 min, and the ratio of water to polymer ranged from 1.9 to 7.1. It was found that pyrolysis of LDPE waste in subcritical water produced hydrogen, methane, carbon monoxide and carbon dioxide, while the liquid product contained alkanes and alkenes with 10-50 carbons atoms, as well as heptadecanone, dichloroacetic acid and heptadecyl ester. The optimized conditions were 152.3°C, reaction time of 1.2 min and ratio of water solution to polymer of 32.7, with the optimum liquid yield of 13.6 wt% and gases yield of 2.6 wt%.

  17. YALINA-booster subcritical assembly pulsed-neutron e xperiments: detector dead time and apatial corrections.

    SciTech Connect

    Cao, Y.; Gohar, Y.; Nuclear Engineering Division

    2010-10-11

    In almost every detector counting system, a minimal dead time is required to record two successive events as two separated pulses. Due to the random nature of neutron interactions in the subcritical assembly, there is always some probability that a true neutron event will not be recorded because it occurs too close to the preceding event. These losses may become rather severe for counting systems with high counting rates, and should be corrected before any utilization of the experimental data. This report examines the dead time effects for the pulsed neutron experiments of the YALINA-Booster subcritical assembly. The nonparalyzable model is utilized to correct the experimental data due to dead time. Overall, the reactivity values are increased by 0.19$ and 0.32$ after the spatial corrections for the YALINA-Booster 36% and 21% configurations respectively. The differences of the reactivities obtained with He-3 long or short detectors at the same detector channel diminish after the dead time corrections of the experimental data for the 36% YALINA-Booster configuration. In addition, better agreements between reactivities obtained from different experimental data sets are also observed after the dead time corrections for the 21% YALINA-Booster configuration.

  18. Initial instability of round liquid jet at subcritical and supercritical environments

    NASA Astrophysics Data System (ADS)

    Muthukumaran, C. K.; Vaidyanathan, Aravind

    2016-07-01

    In the present experimental work, the behavior of laminar liquid jet in its own vapor as well as supercritical fluid environment is conducted. Also the study of liquid jet injection into nitrogen (N2) environment is carried out at supercritical conditions. It is expected that the injected liquid jet would undergo thermodynamic transition to the chamber condition and this would alter the behavior of the injected jet. Moreover at such conditions there is a strong dependence between thermodynamic and fluid dynamic processes. Thus the thermodynamic transition has its effect on the initial instability as well as the breakup nature of the injected liquid jet. In the present study, the interfacial disturbance wavelength, breakup characteristics, and mixing behavior are analysed for the fluoroketone liquid jet that is injected into N2 environment as well as into its own vapor at subcritical to supercritical conditions. It is observed that at subcritical chamber conditions, the injected liquid jet exhibits classical liquid jet characteristics with Rayleigh breakup at lower Weber number and Taylor breakup at higher Weber number for both N2 and its own environment. At supercritical chamber conditions with its own environment, the injected liquid jet undergoes sudden thermodynamic transition to chamber conditions and single phase mixing characteristics is observed. However, the supercritical chamber conditions with N2 as ambient fluid does not have significant effect on the thermodynamic transition of the injected liquid jet.

  19. Extraction of astaxanthin from Euphausia pacific using subcritical 1, 1, 1, 2-tetrafluoroethane

    NASA Astrophysics Data System (ADS)

    Han, Yuqian; Ma, Qinchuan; Wang, Lan; Xue, Changhu

    2012-12-01

    Euphausia pacific is an important source of natural astaxanthin. Studies were carried out to assess the extractability of astaxanthin from E. pacific using subcritical 1, 1, 1, 2-tetrafluoroethane (R134a). To examine the effects of multiple process variables on the extraction yield, astaxanthin was extracted under various conditions of pressure (30-150 bar), temperature (303-343 K), time (10-50 min), flow rate (2-10 g min-1), moisture content (5.5%-63.61%), and particle size (0.25-0.109 mm). The results showed that the extraction yield increased with temperature, pressure, time and flow rate, but decreased with moisture content and particle size. A maximum yield of 87.74% was obtained under conditions of 100 bar, 333 K, and 30 min with a flow rate of 6 g min-1 and a moisture content of 5.5%. The substantial astaxanthin yield obtained under low-pressure conditions demonstrates that subcritical R134a is a good alternative to CO2 for extraction of astaxanthin from E. pacific.

  20. Vacuum ultraviolet spectroscopy of the lowest-lying electronic state in subcritical and supercritical water

    PubMed Central

    Marin, Timothy W.; Janik, Ireneusz; Bartels, David M.; Chipman, Daniel M.

    2017-01-01

    The nature and extent of hydrogen bonding in water has been scrutinized for decades, including how it manifests in optical properties. Here we report vacuum ultraviolet absorption spectra for the lowest-lying electronic state of subcritical and supercritical water. For subcritical water, the spectrum redshifts considerably with increasing temperature, demonstrating the gradual breakdown of the hydrogen-bond network. Tuning the density at 381 °C gives insight into the extent of hydrogen bonding in supercritical water. The known gas-phase spectrum, including its vibronic structure, is duplicated in the low-density limit. With increasing density, the spectrum blueshifts and the vibronic structure is quenched as the water monomer becomes electronically perturbed. Fits to the supercritical water spectra demonstrate consistency with dimer/trimer fractions calculated from the water virial equation of state and equilibrium constants. Using the known water dimer interaction potential, we estimate the critical distance between molecules (ca. 4.5 Å) needed to explain the vibronic structure quenching. PMID:28513601