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1

Advanced High Temperature Reactor Neutronic Core Design  

SciTech Connect

The AHTR is a 3400 MW(t) FHR class reactor design concept intended to serve as a central generating station type power plant. While significant technology development and demonstration remains, the basic design concept appears sound and tolerant of much of the remaining performance uncertainty. No fundamental impediments have been identified that would prevent widespread deployment of the concept. This paper focuses on the preliminary neutronic design studies performed at ORNL during the fiscal year 2011. After a brief presentation of the AHTR design concept, the paper summarizes several neutronic studies performed at ORNL during 2011. An optimization study for the AHTR core is first presented. The temperature and void coefficients of reactivity are then analyzed for a few configurations of interest. A discussion of the limiting factors due to the fast neutron fluence follows. The neutronic studies conclude with a discussion of the control and shutdown options. The studies presented confirm that sound neutronic alternatives exist for the design of the AHTR to maintain full passive safety features and reasonable operation conditions.

Ilas, Dan [ORNL; Holcomb, David Eugene [ORNL; Varma, Venugopal Koikal [ORNL

2012-01-01

2

Conceptual study of advanced PWR core design. Development of advanced PWR core neutronics analysis system.  

National Technical Information Service (NTIS)

The neutronics design system of the advanced PWR consists of (i) hexagonal cell and fuel assembly code for generation of homogenized few-group cross sections and (ii) global core neutronics analysis code for computations of steady-state pin-wise or assemb...

C. H. Kim S. C. Kim T. K. Kim J. Y. Cho H. C. Lee

1995-01-01

3

Optimizing a three-element core design for the Advanced Neutron Source Reactor  

SciTech Connect

Source of neutrons in the proposed Advanced Neutron Source facility is a multipurpose research reactor providing 5-10 times the flux, for neutron beams, of the best existing facilities. Baseline design for the reactor core, based on the ``no new inventions`` rule, was an assembly of two annular fuel elements similar to those used in the Oak Ridge and Grenoble high flux reactors, containing highly enriched U silicide particles. DOE commissioned a study of the use of medium- or low-enriched U; a three-element core design was studied as a means to provide extra volume to accommodate the additional U compound required when the fissionable {sup 235}U has to be diluted with {sup 238}U to reduce the enrichment. This paper describes the design and optimization of that three-element core.

West, C.D.

1995-12-31

4

Optimizing a three-element core design for the advanced neutron source reactor  

SciTech Connect

The source of neutrons in the proposed Advanced Neutron Source facility is a multipurpose research reactor providing 5 to 10 times the flux, for neutron beams, of the best existing facilities. The project team constrained the design with the {open_quotes}no new inventions rule,{close_quotes} which states that the design should not rely on the development of new technology to meet the minimum design criteria (although research and development that can lead to further major improvements beyond the minimum requirements is encouraged). The baseline design for the reactor core, based on this objective and within this constraint, was an assembly of two annular fuel elements, similar to those used in the high-flux reactors at Oak Ridge and Grenoble, containing highly enriched (93%) uranium silicide particles. Subsequently, the U.S. Department of Energy commissioned a study of the impact on performance and on cost of using medium - or low-enriched uranium. In the course of that work, a three-element core design was studied as a means to provide extra volume to accommodate the additional uranium compound required when the fissionable {sup 235}U has to be diluted with {sup 238}U to reduce the enrichment. This paper describes the design and optimization of that three-element core.

West, C.D. [Martin Marietta Energy System, Oak Ridge, TN (United States)

1995-12-31

5

PWR core design, neutronics evaluation and fuel cycle analysis for thorium-uranium breeding recycle  

SciTech Connect

This paper was focused on core design, neutronics evaluation and fuel cycle analysis for Thorium-Uranium Breeding Recycle in current PWRs, without any major change to the fuel lattice and the core internals, but substituting the UOX pellet with Thorium-based pellet. The fuel cycle analysis indicates that Thorium-Uranium Breeding Recycle is technically feasible in current PWRs. A 4-loop, 193-assembly PWR core utilizing 17 x 17 fuel assemblies (FAs) was taken as the model core. Two mixed cores were investigated respectively loaded with mixed reactor grade Plutonium-Thorium (PuThOX) FAs and mixed reactor grade {sup 233}U-Thorium (U{sub 3}ThOX) FAs on the basis of reference full Uranium oxide (UOX) equilibrium-cycle core. The UOX/PuThOX mixed core consists of 121 UOX FAs and 72 PuThOX FAs. The reactor grade {sup 233}U extracted from burnt PuThOX fuel was used to fabrication of U{sub 3}ThOX for starting Thorium-. Uranium breeding recycle. In UOX/U{sub 3}ThOX mixed core, the well designed U{sub 3}ThOX FAs with 1.94 w/o fissile uranium (mainly {sup 233}U) were located on the periphery of core as a blanket region. U{sub 3}ThOX FAs remained in-core for 6 cycles with the discharged burnup achieving 28 GWD/tHM. Compared with initially loading, the fissile material inventory in U{sub 3}ThOX fuel has increased by 7% via 1-year cooling after discharge. 157 UOX fuel assemblies were located in the inner of UOX/U{sub 3}ThOX mixed core refueling with 64 FAs at each cycle. The designed UOX/PuThOX and UOX/U{sub 3}ThOX mixed core satisfied related nuclear design criteria. The full core performance analyses have shown that mixed core with PuThOX loading has similar impacts as MOX on several neutronic characteristic parameters, such as reduced differential boron worth, higher critical boron concentration, more negative moderator temperature coefficient, reduced control rod worth, reduced shutdown margin, etc.; while mixed core with U{sub 3}ThOX loading on the periphery of core has no visible impacts on neutronic characteristics compared with reference full UOX core. The fuel cycle analysis has shown that {sup 233}U mono-recycling with U{sub 3}ThOX fuel could save 13% of natural uranium resource compared with UOX once through fuel cycle, slightly more than that of Plutonium single-recycling with MOX fuel. If {sup 233}U multi-recycling with U{sub 3}ThOX fuel is implemented, more natural uranium resource would be saved. (authors)

Bi, G.; Liu, C.; Si, S. [Shanghai Nuclear Engineering Research and Design Inst., No. 29, Hongcao Road, Shanghai, 200233 (China)

2012-07-01

6

NEUTRONIC REACTOR CORE  

DOEpatents

An improved core for a gas-cooled power reactor which admits gas coolant at high temperatures while affording strong integral supporting structure and efficient moderation of neutrons is described. The multiplicities of fuel elements constituting the critical amassment of fissionable material are supported and confined by a matrix of metallic structure which is interspersed therebetween. Thermal insulation is interposed between substantially all of the metallic matrix and the fuel elements; the insulation then defines the principal conduit system for conducting the coolant gas in heat-transfer relationship with the fuel elements. The metallic matrix itseif comprises a system of ducts through which an externally-cooled hydrogeneous liquid, such as water, is circulated to serve as the principal neutron moderant for the core and conjointly as the principal coolant for the insulated metallic structure. In this way, use of substantially neutron transparent metals, such as aluminum, becomes possible for the supporting structure, despite the high temperatures of the proximate gas. The Aircraft Nuclear Propulsion program's "R-1" reactor design is a preferred embodiment.

Thomson, W.B.; Corbin, A. Jr.

1961-07-18

7

NEUTRONIC REACTOR CORE INSTRUMENT  

DOEpatents

A multi-purpose instrument for measuring neutron flux, coolant flow rate, and coolant temperature in a nuclear reactor is described. The device consists essentially of a hollow thimble containing a heat conducting element protruding from the inner wall, the element containing on its innermost end an amount of fissionsble materinl to function as a heat source when subjected to neutron flux irradiation. Thermocouple type temperature sensing means are placed on the heat conducting element adjacent the fissionable material and at a point spaced therefrom, and at a point on the thimble which is in contact with the coolant fluid. The temperature differentials measured between the thermocouples are determinative of the neutron flux, coolant flow, and temperature being measured. The device may be utilized as a probe or may be incorporated in a reactor core. (AE C)

Mims, L.S.

1961-08-22

8

RELAP5 model for advanced neutron source reactor thermal-hydraulic transients, three-element-core design  

SciTech Connect

In order to utilize reduced enrichment fuel, the three-element-core design has been proposed. The proposed core configuration consists of inner, middle, and outer elements, with the middle element offset axially beneath the inner and outer elements, which are axially aligned. The three-element-core RELAP5 model assumes that the reactor hardware is changed only within the core region, so that the loop piping, heat exchangers, and pumps remain as assumed for the two-element-core configuration. However, the total flow rate through the core is greater and the pressure drop across the core is less so that the primary coolant pumps and heat exchangers are operating at a different point in their performance curves. This report describes the new RELAP5 input for the core components.

Chen, N.C.J.; Wendel, M.W.; Yoder, G.L.

1996-02-01

9

ATW neutronics design studies.  

SciTech Connect

The Accelerator Transmutation of Waste (ATW) concept has been proposed as a transuranics (TRU) (and long-lived fission product) incinerator for processing the 87,000 metric tonnes of Light Water Reactor used fuel which will have been generated by the time the currently deployed fleet of commercial reactors in the US reach the end of their licensed lifetime. The ATW is proposed to separate the uranium from the transuranics and fission products in the LWR used fuel, to fission the transuranics, to send the LWR and ATW generated fission products to the geologic repository and to send the uranium to either a low level waste disposal site or to save it for future use. The heat liberated in fissioning the transuranics would be converted to electricity and sold to partially offset the cost of ATW construction and operations. Options for incineration of long-lived fission products are under evaluation. A six-year science-based program of ATW trade and system studies was initiated in the US FY 2000 to achieve two main purposes: (1) ''to evaluate ATW within the framework of nonproliferation, waste management, and economic considerations,'' and (2) ''to evaluate the efficacy of the numerous technical options for ATW system configuration.'' This paper summarizes the results from neutronics and thermal/hydraulics trade studies which were completed at Argonne National Laboratory during the first year of the program. Core designs were developed for Pb-Bi cooled and Na cooled 840 MW{sub th} fast spectrum transmuter designs employing recycle. Additionally, neutronics analyses were performed at Argonne for a He cooled 600 MW{sub th} hybrid thermal and fast core design proposed by General Atomics Co. which runs critical for 3/4 and subcritical for 1/4 of its four year once-thin burn cycle. The mass flows and the ultimate loss of transuranic isotopes to the waste stream per unit of heat generated during transmutation have been calculated on a consistent basis and are compared. (Long-lived fission product incineration has not been considered in the studies reported here.)

Wade, D. C.; Yang, W. S.; Khalil, H.

2000-11-10

10

NEUTRONIC REACTOR DESIGN TO REDUCE NEUTRON LOSS  

DOEpatents

A nuclear reactor construction is described in which an unmoderated layer of the fissionable material is inserted between the moderated portion of the reactor core and the core container steel wall which is surrounded by successive layers of pure fertile material and fertile material having moderator. The unmoderated layer of the fissionable material will insure that a greater portion of fast neutrons will pass through the steel wall than would thermal neutrons. As the steel has a smaller capture cross-section for the fast neutrons, then greater numbers of the neutrons will pass into the blanket thereby increasing the over-all efficiency of the reactor.

Mills, F.T.

1961-05-01

11

Neutron radiography facility annular core pulse reactor  

Microsoft Academic Search

Neutron radiography capabilities which are an integral part of the Annular Core Pulse Reactor (ACPR) experiment facilities have been extended and improved. Neutron radiography provides an important non-destructive testing technique. Ordinary x- or gamma-radiography are not entirely satisfactory for the non-destructive testing of such items as explosives, valve seals, sealing materials, and electrical potting compounds. The non-linearity in neutron absorption

B. F. Estes; J. S. Philbin; F. V. Thome

1976-01-01

12

Automated Core Design  

SciTech Connect

Multistate searching methods are a subfield of distributed artificial intelligence that aims to provide both principles for construction of complex systems involving multiple states and mechanisms for coordination of independent agents' actions. This paper proposes a multistate searching algorithm with reinforcement learning for the automatic core design of a boiling water reactor. The characteristics of this algorithm are that the coupling structure and the coupling operation suitable for the assigned problem are assumed and an optimal solution is obtained by mutual interference in multistate transitions using multiagents. Calculations in an actual plant confirmed that the proposed algorithm increased the convergence ability of the optimization process.

Kobayashi, Yoko; Aiyoshi, Eitaro

2005-07-15

13

FAST FOSSIL ROTATION OF NEUTRON STAR CORES  

SciTech Connect

It is argued that the superfluid core of a neutron star super-rotates relative to the crust, because stratification prevents the core from responding to the electromagnetic braking torque, until the relevant dissipative (viscous or Eddington-Sweet) timescale, which can exceed {approx}10{sup 3} yr and is much longer than the Ekman timescale, has elapsed. Hence, in some young pulsars, the rotation of the core today is a fossil record of its rotation at birth, provided that magnetic crust-core coupling is inhibited, e.g., by buoyancy, field-line topology, or the presence of uncondensed neutral components in the superfluid. Persistent core super-rotation alters our picture of neutron stars in several ways, allowing for magnetic field generation by ongoing dynamo action and enhanced gravitational wave emission from hydrodynamic instabilities.

Melatos, A., E-mail: amelatos@unimelb.edu.au [School of Physics, University of Melbourne, Parkville, VIC 3010 (Australia)

2012-12-10

14

Neutronic analysis of three-element core configurations for the Advanced Neutron Source Reactor  

SciTech Connect

Calculations of several important neutronic parameters have been performed for ten different three-element configurations considered for the Advanced Neutron Source (ANS) Reactor. Six of these configurations (labeled ST, SB, MT, MB, LT, and LB) are there result of the permutations of the same three elements. Two configurations (ST- MOD and SB-MOD) have the same element configuration as their base core design (ST and SB) but have slightly different element dimensions, and two configurations (ST-OL1 and ST-OL2) have two overlapping elements to increase the neutron fluxes in the reflector. For each configuration, in addition to the conceptual two-element design, fuel-cycle calculations were performed with calculations required to obtain unperturbed fluxes. The element power densities, peak thermal neutron flux as a function of position throughout the cycle, fast flux, fast-to-thermal flux ratios, irradiation and production region fluxes, and control rod worth curves were determined. The effective multiplication factor for each fuel element criticality. A comparison shows that the ST core configurations have the best overall performance, and the fully overlapping core configuration ST-OL2 has the best performance by a large margin. Therefore, on the basis of the neutronics results, the fully overlapping configuration is recommended for further consideration in using a three-element ANS reactor core. Other considerations such as thermal-hydraulics, safety, and engineering that are not directly related to the core neutronic performance must be weighed before a final design is chosen.

Gehin, J.C.

1995-08-01

15

Baryon Superfluidity in Neutron Star Cores  

NASA Astrophysics Data System (ADS)

Whether hyperons admixed in neutron star cores could be superfluid or not is investigated by a realistic approach to take account of the information on YY and YN interactions from hypernuclear data. It is found that the ?-superfluid is surely realized, though in a restricted density region, and also the ?-- and ?--superfluids have a strong possibility to be realized. A comment is given to the influences of hyperon components on neutron superfluidity.

Takatsuka, T.; Nishizaki, S.; Yamamoto, Y.; Tamagaki, R.

2003-04-01

16

Thermal-hydraulic mixing in the split-core ANS reactor design  

Microsoft Academic Search

A design has been proposed for the advanced neutron source (ANS) reactor that incorporates a split core, one purpose of which is to create a mixing plenum between the upper and lower cores. It was hoped that in addition to introducing various desirable neutronics features, such as decreasing the fast neutron flux contamination of thermal and cold neutron beams located

Dorning

1988-01-01

17

Dynamics of dissipative multifluid neutron star cores  

NASA Astrophysics Data System (ADS)

We present a Newtonian multifluid formalism for superfluid neutron star cores, focusing on the additional dissipative terms which arise when one takes into account the individual dynamical degrees of freedom associated with the coupled “fluids.” The problem is of direct astrophysical interest as the nature of the dissipative terms can have significant impact on the damping of the various oscillation modes of the star and the associated gravitational-wave signatures. A particularly interesting application concerns the gravitational-wave driven instability of f- and r-modes. We apply the developed formalism to two specific three-fluid systems: (i) a hyperon core in which both ? and ?- hyperons are present and (ii) a core of deconfined quarks in the color-flavor-locked phase in which a population of neutral K0 kaons is present. The formalism is, however, general and can be applied to other problems in neutron-star dynamics (such as the effect of thermal excitations close to the superfluid transition temperature) as well as laboratory multifluid systems.

Haskell, B.; Andersson, N.; Comer, G. L.

2012-09-01

18

NEUTRONIC REACTOR OPERATIONAL METHOD AND CORE SYSTEM  

DOEpatents

Homogeneous neutronic reactor systems are described wherein an aqueous fuel solution is continuously circulated through a spherical core tank. The pumped fuel solution-is injected tangentially into the hollow spherical interior, thereby maintaining vigorous rotation of the solution within the tank in the form of a vortex; gaseous radiolytic decomposition products concentrate within the axial vortex cavity. The evolved gas is continuously discharged through a gas- outlet port registering with an extremity of the vortex cavity. and the solution stream is discharged through an annular liquid outlet port concentrically encircling the gas outlet by virtue of which the vortex and its cavity are maintained precisely axially aligned with the gas outlet. A primary heat exchanger extracts useful heat from the hot effluent fuel solution before its recirculation into the core tank. Hollow cylinders and other alternative core- tank configurations defining geometric volumes of revolution about a principal axis are also covered. AEC's Homogeneous Reactor Experiment No. 1 is a preferred embodiment.

Winters, C.E.; Graham, C.B.; Culver, J.S.; Wilson, R.H.

1960-07-19

19

The spin evolution of neutron stars with the superfluid core  

NASA Astrophysics Data System (ADS)

We investigate the neutron stars spin evolution (breaking, inclination angle evolution and radiative precession), taking into account the superfluidity of the neutrons in the star core. The neutron star is treated as a two-component system consisting of a `charged' component (including the crust and the core protons, electrons and normal neutrons) and a core superfluid neutron component. The components are supposed to interact through the mutual friction force. We assume that the `charged' component rotates rigidly. The neutron superfluid velocity field is calculated directly from linearized hydrodynamical equations. It is shown that the superfluid core accelerates the evolution of inclination angle and makes all pulsars evolve to either the orthogonal or coaxial state. However, rapid evolution seems to contradict the observation data. Obtained results together with the observations may allow us to examine the superfluid models.

Barsukov, D. P.; Goglichidze, O. A.; Tsygan, A. I.

2013-06-01

20

Gas core reactor (neutronics)-theoretical modeling and experimental verification  

Microsoft Academic Search

The development of a sound scientific data base that includes key information in the areas of neutronics, thermophysical properties, and materials for cyclic gaseous core reactors has been the objective of a lengthy theoretical\\/experimental research program at the University of Florida. The most recently completed phase of this program includes theoretical neutronics modeling and experimental verification. Static and dynamic neutronic

E. T. Dugan; E. E. Carroll; N. J. Diaz; H. M. Forehand

1985-01-01

21

Measurements of the thermal neutrons flux near the EAS core  

NASA Astrophysics Data System (ADS)

The characteristics of the thermal neutrons flux have been measured near the EAS core at the "Carpet-2" EAS array. The thermal neutron detectors were placed on the floor of the tunnel of the Muon Detector (MD) and showers with a core near the MD were selected. Thermal neutrons multiplicity spectrum has been obtained for these showers. Measurements of the lateral distribution function of thermal neutrons at distances of 1-16 m from the shower axis have been performed. The mean number of the recorded thermal neutrons as a function of the number of hadrons crossing the MD has been measured.

Dzhappuev, D. D.; Volchenko, V. I.; Kudzhaev, A. U.; Mikhailova, O. I.; Petkov, V. B.; Stenkin, Yu V.; Tsyabuk, A. L.

2013-02-01

22

Development of structural design criteria for highly irradiated core components  

Microsoft Academic Search

This paper reviews development to date in the US of structural design criteria for fast breeder reactor core components. Since these components operate in an elevated temperature, fast neutron environment, the criteria for them must take into account the significant time-dependent changes in structural material behavior resulting from irradiation. Objective is to establish a national consensus on design rules, together

D. V. Nelson; M. M. Abo-El-Ata; J. D. Stephen; R. G. Sim

1978-01-01

23

400 MWth gas cooled ADT core neutronic benchmark  

SciTech Connect

In France, the 'December 1991 act' has generated much R and D on nuclear waste management. One of the main conclusions is that fast reactors offer the best performances to transmute minor actinides. Two types of fast spectrum reactors can be used: critical or sub-critical ones (in this case, Accelerator Driven systems, ADS). Within this scope, a Gas-cooled ADT core neutronic benchmark has been proposed by CEA for an IAEA Coordinated Research Project (CRP) on 'Studies of Advanced Reactor Technology Options for Effective Incineration of Radioactive Waste'. This will help clarifying the future issues associated to the improvement of the core designs with more reliable and accurate tools. The benchmark exercise is based on a 400 MWth gas-cooled ADT with fertile-free fuel (Pu, Np, Am, Cm)O{sub 2} within MgO matrix. (authors)

Chabert, C.; Rimpault, G.; Peneliau, Y.; Tommasi, J.; Plisson-Rieunier, D. [Commissariat a l'Energie Atomique - CEA, Cadarache Centre, 13108 Saint-Paul-lez-Durance Cedex (France); da Cruz, D.F. [NRG Petten (Netherlands); Malambu, E. [SCK CEN (Belgium); Rineiski, A. [FZK Karlsruhe (Germany)

2007-07-01

24

Preliminary engineering design of sodium-cooled CANDLE core  

NASA Astrophysics Data System (ADS)

The CANDLE burning process is characterized by the autonomous shifting of burning region with constant reactivity and constant spacial power distribution. Evaluations of such critical burning process by using widely used neutron diffusion and burning codes under some realistic engineering constraints are valuable to confirm the technical feasibility of the CANDLE concept and to put the idea into concrete core design. In the first part of this paper, it is discussed that whether the sustainable and stable CANDLE burning process can be reproduced even by using conventional core analysis tools such as SLAROM and CITATION-FBR. As a result, it is certainly possible to demonstrate it if the proper core configuration and initial fuel composition required as CANDLE core are applied to the analysis. In the latter part, an example of a concrete image of sodium cooled, metal fuel, 2000MWt rating CANDLE core has been presented by assuming an emerging inevitable technology of recladding. The core satisfies engineering design criteria including cladding temperature, pressure drop, linear heat rate, and cumulative damage fraction (CDF) of cladding, fast neutron fluence and sodium void reactivity which are defined in the Japanese FBR design project. It can be concluded that it is feasible to design CADLE core by using conventional codes while satisfying some realistic engineering design constraints assuming that recladding at certain time interval is technically feasible.

Takaki, Naoyuki; Namekawa, Azuma; Yoda, Tomoyuki; Mizutani, Akihiko; Sekimoto, Hiroshi

2012-06-01

25

Superfluidity in the Core of Neutron Stars  

NASA Astrophysics Data System (ADS)

The year (1958) after the publication of the BCS theory, Bohr, Mottelson & Pines showed that nuclei should also contain superfluid neutrons and superconducting protons. In 1959, A. Migdal proposed that neutron superfluidity should also occur in the interior of neutron stars. Pairing in nuclei forms Cooper pairs with zero spin, but the relevant component of the nuclear interaction becomes repulsive at densities larger than the nuclear matter density. It has been proposed that neutron-neutron interaction in the spin-triplet state, and L=1 orbital angular momentum, that is known to be attractive from laboratory experiments, may result in a new form of neutron superfluidity in the neutron star interior. I will review our present understanding of the structure of neutron stars and describe how superfluidity strongly affects their thermal evolution. I will show how a ``Minimal Model'' that excludes the presence of ``exotic'' matter (Bose condensates, quarks, etc.) is compatible with most observations of the surface temperatures of young isolated neutron stars in the case this neutron superfluid exists. Compared to the case of isotropic spin-zero Cooper pairs, the formation of anisotropic spin-one Cooper pairs results in a strong neutrino emission that leads to an enhanced cooling of neutron stars after the onset of the pairing phase transition and allows the Minimal Cooling scenario to be compatible with most observations. In the case the pairing critical temperature Tc is less than about 6 x10^8 K, the resulting rapid cooling of the neutron star may be observable. It was recently reported that 10 years of Chandra observations of the 333 year young neutron star in the Cassiopeia A supernova remnant revealed that its temperature has dropped by about 5%. This result indicates that neutrons in this star are presently becoming superfluid and, if confirmed, provides us with the first direct observational evidence for neutron superfluidity at supra-nuclear densities.

Page, Dany

2013-04-01

26

Design configuration of GCFR core assemblies  

SciTech Connect

The current design configurations of the core assemblies for the gas-cooled fast reactor (GCFR) demonstration plant reactor core conceptual design are described. Primary emphasis is placed upon the design innovations that have been incorporated in the design of the core assemblies since the establishment of the initial design of an upflow GCFR core. A major feature of the design configurations is that they are prototypical of core assemblies for use in commercial plants; a larger number of the same assemblies would be used in a commercial plant.

LaBar, M.P.; Lee, G.E.; Meyer, R.J.

1980-05-01

27

Optimization of IEC grid design for maximum neutron production  

SciTech Connect

Two different, complementary approaches were taken to determine the effects of an Inertial Electrostatic Confinement (IEC) grid`s design on the neutron production rate of the device. A semi-empirical formula developed from experimental data predicts the neutron yield of an IEC device, given the chamber size, grid radius and transparency, and operating voltage and current. Results from the IXL computer program support some of the scalings found in the semi-empirical formula. A second formula was also developed that predicts the neutron yield of an IEC device using grid design parameters and the ion core radius. The SIMION computer program was used to calculate the ion core radius. These formulas are useful tools for designing grids that will maximize the neutron yield for IEC devices. 7 refs., 9 figs.

Miley, G.H.; DeMora, J.; Stubbers, R.; Tzonev, I.V. [Univ. of Illinois, Urbana, IL (United States); Anderl, R.A. [Lockheed Martin Idaho Technologies Company, Idaho Falls, ID (United States); Nadler, J.H. [Department of Energy, Idaho Falls, ID (United States); Nebel, R. [Los Alamos National Lab., NM (United States)

1996-12-31

28

Neutron beam design for neutron radiography at the Musashi reactor  

Microsoft Academic Search

Studies were carried out for the design of a thermal, an epithermal, and a fast neutron beam for neutron radiography (NRG) in the horizontal beam port or in the thermalizing column at the Musashi reactor (TRIGA-II, 100 kW). Thermal, epithermal and fast neutron energy ranges were selected as 10 keV, respectively. To produce a good neutron beam in terms of

Tetsuo Matsumoto

1996-01-01

29

Heat transfer and core neutronics considerations of the heat pipe cooled thermionic reactor  

NASA Astrophysics Data System (ADS)

The authors summarize the results of detailed neutronic and thermal-hydraulic evaluations of the heat pipe cooled thermionic (HPTI) reactor design, identify its key design attributes, and quantify its performance characteristics. The HPTI core uses modular, liquid-metal core heat transfer assemblies to replace the liquid-metal heat transport loop employed by in-core thermionic reactor designs of the past. The nuclear fuel, power conversion, heat transport, and heat rejection functions are all combined into a single modular unit. The reactor/converter assembly uses UN fuel pins to obtain a critical core configuration with in-core safety rods and reflector controls added to complete the subassembly. By thermally bonding the core heat transfer assemblies during the reactor core is coupled neutronically, thermally, and electrically into a modular assembly of individual power sources with cross-tied architecture. A forward-facing heat pipe radiator assembly extends from the reactor head in the shape of a frustum of a cone on the opposite side of the power system from the payload. Important virtues of the concept are the absence of any single-point failures and the ability of the core to effectively transfer the TFE waste heat load laterally to other in-core heat transfer assemblies in the event of multiple failures in either in-core and radiator heat pipes.

Determan, W. R.; Lewis, Brian

30

Nodal weighting factor method for ex-core fast neutron fluence evaluation  

SciTech Connect

The nodal weighting factor method is developed for evaluating ex-core fast neutron flux in a nuclear reactor by utilizing adjoint neutron flux, a fictitious unit detector cross section for neutron energy above 1 or 0.1 MeV, the unit fission source, and relative assembly nodal powers. The method determines each nodal weighting factor for ex-core neutron fast flux evaluation by solving the steady-state adjoint neutron transport equation with a fictitious unit detector cross section for neutron energy above 1 or 0.1 MeV as the adjoint source, by integrating the unit fission source with a typical fission spectrum to the solved adjoint flux over all energies, all angles and given nodal volume, and by dividing it with the sum of all nodal weighting factors, which is a normalization factor. Then, the fast neutron flux can be obtained by summing the various relative nodal powers times the corresponding nodal weighting factors of the adjacent significantly contributed peripheral assembly nodes and times a proper fast neutron attenuation coefficient over an operating period. A generic set of nodal weighting factors can be used to evaluate neutron fluence at the same location for similar core design and fuel cycles, but the set of nodal weighting factors needs to be re-calibrated for a transition-fuel-cycle. This newly developed nodal weighting factor method should be a useful and simplified tool for evaluating fast neutron fluence at selected locations of interest in ex-core components of contemporary nuclear power reactors. (authors)

Chiang, R. T. [AREVA NP Inc., 6399 San Ignacio Ave., San Jose, CA 95119 (United States)

2012-07-01

31

MODULAR CORE UNITS FOR A NEUTRONIC REACTOR  

DOEpatents

A modular core unit for use in a nuclear reactor is described. Many identical core modules can be placed next to each other to make up a complete core. Such a module includes a cylinder of moderator material surrounding a fuel- containing re-entrant coolant channel. The re-entrant channel provides for the circulation of coolant such as liquid sodium from one end of the core unit, through the fuel region, and back out through the same end as it entered. Thermal insulation surrounds the moderator exterior wall inducing heat to travel inwardly to the coolant channel. Spaces between units may be used to accommodate control rods and support structure, which may be cooled by a secondary gas coolant, independently of the main coolant. (AEC)

Gage, J.F. Jr.; Sherer, D.B.

1964-04-01

32

Preliminary fracture analysis of the core pressure boundary tube for the Advanced Neutron Source Research Reactor  

Microsoft Academic Search

The outer core pressure boundary tube (CPBT) of the Advanced neutron Source (ANS) reactor being designed at Oak Ridge National Laboratory is currently specified as being composed of 6061-T6 aluminum. ASME Boiler and Pressure Vessel Code fracture analysis rules for nuclear components are based on the use of ferritic steels; the expressions, tables, charts and equations were all developed from

K. C. Schulz; G. T. Yahr

1995-01-01

33

A proposal of a new in-core neutron monitor using nuclear pumped laser  

Microsoft Academic Search

A new type of in-core neutron monitor using the 3He-Ne nuclear pumped laser (NPL) is proposed and the optimum design and characteristics of this detector are discussed, especially for application to the fast breeder reactor (FBR). Through this optimum design study, a highest efficiency monitor has been found to show the simple and practical relation of PR = 3.54 [atom

A. Okumura; S. Soramoto; H. Hayashida; H. Nakamura; M. Nakazawa

1991-01-01

34

No-core full configuration calculations for neutron droplets  

NASA Astrophysics Data System (ADS)

We present recent results from no-core full configuration calculations for neutron droplets in an external field. We use several different NN interactions (JISP16, chiral N3LO, and Minnesota) and discuss the similarities and differences in the obtained energies, rms radii, and density profiles. We get good numerical convergence for up to 20 neutrons, and our results are in agreement with other methods. These results form an excellent basis for validation and verification of new energy-density functionals for nuclear physics.

Vary, James; Maris, Pieter

2010-11-01

35

Core length testable reactor concept neutronic analysis  

SciTech Connect

Development work on thermionic reactor systems has been ongoing in the US since the early 1950s. While significant successes were achieved, progress has been hampered by frequent changes in direction and funding instabilities (as has been true for many high technology initiatives). The recent Air Force thermionics initiative (1991) represents the latest in thermionics reactor development in the US. This Air Force initiative called for the development of thermionics reactors with the output power of about 40 kWe, and which incorporated the features of testability, fabricability, low development cost, high level of safety and reliability, and survivability. Several concepts were analyzed to define a design that would meet all the requirements set forth by the Air Force. This report describes the methodology used, the different designs analyzed and reasons for the evolution of the design, and presents the results for the different concepts.

Hanan, N.A.; Bhattacharyya, S.K.

1992-09-01

36

Design and Performance of Neutron Detector N  

Microsoft Academic Search

The design of the N* Detector (``Neutron Sandwich Transmuter\\/Activation-gamma Radiator'') and its response to neutrons are described. The N* is a high efficiency plastic-scintillation detector with sensitivity to neutrons in a wide energy range and multi-hit information. The device consists of a stack of plastic scintillator slabs (Saint Gobain BC-408) alternating with thin radiator films (PDMS), which are loaded with

Iwona Pawelczak; Jan Toke; Yun-Tse Tsai; W. Udo Schröder

2008-01-01

37

DANDE: a linked code system for core neutronics/depletion analysis  

SciTech Connect

This report describes DANDE - a modular neutronics, depletion code system for reactor analysis. It consists of nuclear data processing, core physics, and fuel depletion modules, and allows one to use diffusion and transport methods interchangeably in core neutronics calculations. This latter capability is especially important in the design of small modular cores. Additional unique features include the capability of updating the nuclear data file during a calculation; a detailed treatment of depletion, burnable poisons as well as fuel; and the ability to make geometric changes such as control rod repositioning and fuel relocation in the course of a calculation. The detailed treatment of reactor fuel burnup, fission-product creation and decay, as well as inventories of higher-order actinides is a necessity when predicting the behavior of reactor fuel under increased burn conditions. The operation of the code system is made clear in this report by following a sample problem.

LaBauve, R.J.; England, T.R.; George, D.C.; MacFarlane, R.E.; Wilson, W.B.

1985-06-01

38

DANDE: a linked code system for core neutronics/depletion analysis  

SciTech Connect

This report describes DANDE - a modular neutronics, depletion code system for reactor analysis. It consists of nuclear data processing, core physics, and fuel depletion modules, and allows one to use diffusion and transport methods interchangeably in core neutronics calculations. This latter capability is especially important in the design of small modular cores. Additional unique features include the capability of updating the nuclear data file during a calculation; a detailed treatment of depletion, burnable poisons as well as fuel; and the ability to make geometric changes such as control rod repositioning and fuel relocation in the cource of a calculation. The detailed treatment of reactor fuel burnup, fission-product creation and decay, as well as inventories of higher-order actinides is a necessity when predicting the behavior of reactor fuel under increased burn conditions. The operation of the code system is illustrated in this report by two sample problems. 25 refs.

LaBauve, R.J.; England, T.R.; George, D.C.; MacFarlane, R.E.; Wilson, W.B.

1986-01-01

39

Design of multidirectional neutron beams for boron neutron capture synovectomy  

SciTech Connect

Boron neutron capture synovectomy (BNCS) is a potential application of the {sup 10}B(n, a) {sup 7}Li reaction for the treatment of rheumatoid arthritis. The target of therapy is the synovial membrane. Rheumatoid synovium is greatly inflamed and is the source of the discomfort and disability associated with the disease. The BNCS proposes to destroy the synovium by first injecting a boron-labeled compound into the joint space and then irradiating the joint with a neutron beam. This study discusses the design of a multidirectional neutron beam for BNCS.

Gierga, D.P.; Yanch, J.C. [Massachusetts Institute of Technology, Cambridge, MA (United States); Shefer, R.E. [Newton Scientific, Inc., Cambridge, MA (United States)

1997-12-01

40

Attributes of a rotating neutron star with a hyperon core  

SciTech Connect

We study the effect of rotation on the global properties of a neutron star with a hyperon core in an effective chiral model with varying nucleon effective masses within a mean-field approach. The resulting gross properties of the rotating compact star sequences are then compared and analyzed with other theoretical predictions and observations from neutron stars. The maximum mass of the compact star predicted by the model lies in the range of (1.4-2.4)M{sub {center_dot}} at Kepler frequency {omega}{sub K}, which is consistent with recent observations of high mass stars, thereby reflecting the sensitivity of the underlying nucleon effective mass in the dense matter equation of state. We also discuss the implications of the experimental constraints from the flow data from heavy-ion collisions on the global properties of rotating neutron stars.

Jha, T. K.; Mishra, H.; Sreekanth, V. [Theoretical Physics Division, Physical Research Laboratory, Navrangpura, Ahmedabad, India-380 009 (India)

2008-04-15

41

Attributes of a rotating neutron star with a hyperon core  

NASA Astrophysics Data System (ADS)

We study the effect of rotation on the global properties of a neutron star with a hyperon core in an effective chiral model with varying nucleon effective masses within a mean-field approach. The resulting gross properties of the rotating compact star sequences are then compared and analyzed with other theoretical predictions and observations from neutron stars. The maximum mass of the compact star predicted by the model lies in the range of (1.4-2.4)M? at Kepler frequency ?K, which is consistent with recent observations of high mass stars, thereby reflecting the sensitivity of the underlying nucleon effective mass in the dense matter equation of state. We also discuss the implications of the experimental constraints from the flow data from heavy-ion collisions on the global properties of rotating neutron stars.

Jha, T. K.; Mishra, H.; Sreekanth, V.

2008-04-01

42

Nuclear design of a vapor core reactor for space nuclear propulsion  

Microsoft Academic Search

Neutronic analysis methodology and results are presented for the nuclear design of a vapor core reactor for space nuclear propulsion. The Nuclear Vapor Thermal Reactor (NVTR) Rocket Engine uses modified NERVA geometry and systems which the solid fuel replaced by uranium tetrafluoride vapor. The NVTR is an intermediate term gas core thermal rocket engine with specific impulse in the range

Edward T. Dugan; Yoichi Watanabe; Stephen A. Kuras; Isaac Maya; Nils J. Diaz

1993-01-01

43

Advanced neutron source three-element-core fuel grading.  

National Technical Information Service (NTIS)

The proposed Advanced Neutron Source (ANS) pre-conceptual design consists of a two-element 330 MW(sub f) nuclear reactor fueled with highly-enriched uranium and is cooled, moderated, and reflected with heavy water. Recently, the ANS design has been change...

J. C. Gehin

1995-01-01

44

Identifying the Core in Art and Design.  

ERIC Educational Resources Information Center

|Presents a model for systematizing the relationships between core content and educational objectives in British art and design classes. The model shows how the expressive, perceptual, analytic and cultural domains of art and design education are interrelated. Available from Carfax Publishing Company, P.O. Box 25, Abingdon, Oxfordshire OX14 1RW…

Allison, Brian

1982-01-01

45

Neutronic design of a fission converter-based epithermal neutron beam for neutron capture therapy  

Microsoft Academic Search

To meet the needs for neutron capture theory (NCT) irradiations, a high-intensity, high-quality fusion converter-based epithermal neutron beam has been designed for the MITR-II research reactor. This epithermal neutron beam, capable of delivering treatments in a few minutes with negligible background contamination from fast neutrons and photons, will be installed in the present thermal column and hohlraum of the 5-MW

W. S. Kiger; S. Sakamoto; O. K. Harling

1999-01-01

46

Neutron tube design study for boron neutron capture therapy application  

SciTech Connect

Radio-frequency (RF) driven ion sources are being developed in Lawrence Berkeley National Laboratory (LBNL) for sealed-accelerator-tube neutron generator application. By using a 5-cm-diameter RF-driven multicusp source H{sup +} yields over 95% have been achieved. These experimental findings will enable one to develop compact neutron generators based on the D-D or D-T fusion reactions. In this new neutron generator, the ion source, the accelerator and the target are all housed in a sealed metal container without external pumping. Recent moderator design simulation studies have shown that 14 MeV neutrons could be moderated to therapeutically useful energy ranges for boron neutron capture therapy (BNCT). The dose near the center of the brain with optimized moderators is about 65% higher than the dose obtained from a typical neutron spectrum produced by the Brookhaven Medical Research Reactor (BMRR), and is comparable to the dose obtained by other accelerator-based neutron sources. With a 120 keV and 1 A deuteron beam, a treatment time of {approx}35 minutes is estimated for BNCT.

Verbeke, J.M.; Lee, Y.; Leung, K.N.; Vujic, J.; Williams, M.D.; Wu, L.K.; Zahir, N.

1999-05-06

47

Neutron Streak Camera Electron Gun Design.  

National Technical Information Service (NTIS)

Representative values for electrode voltages, time compensation, and transmission efficiency are obtained by computer simulation for a preliminary design of an electron gun to be used in a neutron streak camera application. The calculations indicate a tim...

E. R. Close J. S. Colonias

1984-01-01

48

CHINA SPALLATION NEUTRON SOURCE DESIGN.  

SciTech Connect

The China Spallation Neutron Source (CSNS) is an accelerator-based high-power project currently in preparation under the direction of the Chinese Academy of Sciences (CAS). The complex is based on an H- linear accelerator, a rapid cycling proton synchrotron accelerating the beam to 1.6 GeV, a solid tungsten target station, and five initial instruments for spallation neutron applications. The facility will operate at 25 Hz repetition rate with a phase-I beam power of about 120 kW. The major challenge is to build a robust and reliable user's facility with upgrade potential at a fractional of ''world standard'' cost.

WEI,J.

2007-01-29

49

Detection of residual core in air-cooled turbine blades using neutron radiography  

NASA Astrophysics Data System (ADS)

Neutron radiography has proven to be the most efficient nondestructive method for the detection of residual core material in air-cooled turbine blades. The method relies on the addition of gadolinium compounds to the core material and the subsequent thermal neutron radiography of the casting after the core removal process.

Tsukimura, R. R.; Meren, A. W.; Scott, V. P.

1995-07-01

50

Observational prospects for massive stars with degenerate neutron cores  

NASA Astrophysics Data System (ADS)

In this paper we present observable characteristics of massive stars with degenerate neutron cores, or Thorne-Zytkow objects, which would distinguish them from other stars. Spectroscopically these stars are red supergiants, but they have peculiar surface abundances compared with 'normal' red supergiants. This is due to the convection of rp-process products from the nuclear burning region to the surface. We present predictions of surface abundances of elelments heavier than iron. In particular, Mo should have an abundance greater than 1000 times solar. We estimate that several of the about 100 red supergiants within 5 kpc of the Sun are Thorne-Zytkow objects.

Biehle, Garrett T.

1994-01-01

51

A shallow water analogue of asymmetric core-collapse, and neutron star kick/spin  

NASA Astrophysics Data System (ADS)

Massive stars end their life with the gravitational collapse of their core and the formation of a neutron star. Their explosion as a supernova depends on the revival of a spherical accretion shock, located in the inner 200km and stalled during a few hundred milliseconds. Numerical simulations suggest that the large scale asymmetry of the neutrino-driven explosion is induced by a hydrodynamical instability named SASI. Its non radial character is able to influence the kick and the spin of the resulting neutron star. The SWASI experiment is a simple shallow water analog of SASI, where the role of acoustic waves and shocks is played by surface waves and hydraulic jumps. Distances in the experiment are scaled down by a factor one million, and time is slower by a factor one hundred. This experiment is designed to illustrate the asymmetric nature of core-collapse supernova.

Foglizzo, Thierry; Masset, Frédéric; Guilet, Jérôme; Durand, Gilles

2012-09-01

52

Combined analysis of neutron and photon flux measurements for the Jules Horowitz reactor core mapping  

SciTech Connect

We study the combined analysis of nuclear measurements to improve the knowledge of the irradiation conditions in the experimental locations of the future Jules Horowitz Reactor (JHR). The goal of the present work is to measure more accurately neutron flux, photon flux and nuclear heating in the reactor. In a Material Testing Reactor (MTR), nuclear heating is a crucial parameter to design the experimental devices to be irradiated in harsh nuclear conditions. This parameter drives the temperature of the devices and of the samples. The numerical codes can predict this parameter but in-situ measurements are necessary to reach the expected accuracy. For this reason, one objective of the IN-CORE program [1] is to study the combined measurements of neutron and photon flux and their cross advanced interpretation. It should be reminded that both neutron and photon sensors are not totally selective as their signals are due to neutron and photon interactions. We intend to measure the neutron flux by three different kinds of sensors (Uranium Fission chamber, Plutonium Fission chamber and Self Powered Neutron Detector), the photon flux by two different sensors (Ionization chamber and Self Powered Gamma Detector) and the nuclear heating by two different ones (Differential calorimeter and Gamma Thermometer). For the same parameter, we expect that the use of different kinds of sensors will allow a better estimation of the aimed parameter by mixing different spectrum responses and different neutron and gamma contributions. An experimental test called CARMEN-1 is scheduled in OSIRIS reactor (CEA Saclay - France) at the end of 2011, with the goal to map irradiation locations in the reactor reflector to get a first validation of the analysis model. This article focuses on the sensor selection for CARMEN-1 experiment and to the way to link neutron and photon flux measurements in view to reduce their uncertainties but also to better assess the neutron and photon contributions to nuclear heating. (authors)

Fourmentel, D.; Villard, J. F.; Lyoussi, A. [DEN Reactor Studies Dept., French Nuclear Energy and Alternative Energies Commission, CEA Cadarache, 13108 Saint Paul-Lez-Durance (France); Reynard-Carette, C. [Laboratoire Chimie Provence LCP UMR 6264, Univ. of Provence, Centre St. Jerome, 13397 Marseille Cedex 20 (France); Bignan, G.; Chauvin, J. P.; Gonnier, C.; Guimbal, P.; Malo, J. Y. [DEN Reactor Studies Dept., French Nuclear Energy and Alternative Energies Commission, CEA Cadarache, 13108 Saint Paul-Lez-Durance (France); Carette, M.; Janulyte, A.; Merroun, O.; Brun, J.; Zerega, Y.; Andre, J. [Laboratoire Chimie Provence LCP UMR 6264, Univ. of Provence, Centre St. Jerome, 13397 Marseille Cedex 20 (France)

2011-07-01

53

Many-core design from a thermal perspective  

Microsoft Academic Search

Air cooling limits have been a major design challenge in recent years for integrated circuits. Multi-core exacerbates thermal chal- lenges because power scales with the number of cores, but also creates new opportunities for temperature-aware design, because multi-core designs offer more design parameters than single-core designs. This paper investigates the relationship between core size and on-chip hot spot temperature and

Wei Huang; Mircea R. Stant; Karthik Sankaranarayanan; Robert J. Ribando; Kevin Skadron

2008-01-01

54

Design and simulation of a neutron facility.  

PubMed

State and other regulatory entities require that for any facility housing a particle accelerator the surrounding areas must be restricted to public access unless the dose equivalent rate is less than 0.02 mSv h at 5 cm from any accessible wall surrounding the facility under conditions of maximum radiation output. A Monte Carlo radiation transport simulation code, MCNP5, was used to design a proposed facility to shield two D-T neutron generators and one D-D neutron generator. A number of different designs were simulated, but due to cost and space issues a small concrete cave proved to be the best solution for the shielding problem. With this design, all of the neutron generators could be used and all of the rooms surrounding the neutron facility could be considered unrestricted to public access. To prevent unauthorized access into the restricted area of the neutron facility, light curtains, warning lights, door interlocks, and rope barriers will be built into the facility. PMID:17228186

Studenski, Matthew T; Kearfott, Kimberlee J

2007-02-01

55

Neutronic and thermal design considerations for heat-pipe reactors  

SciTech Connect

SABRE (Space-Arena Baseline Reactor) is a 100-kW/sub e/, heat-pipe-cooled, beryllium-reflected, fast reactor that produces heat at a temperature of 1500/sup 0/K and radiatively transmits it to high-temperature thermoelectric (TE) conversion elements. The use of heat pipes for core heat removal eliminates single-point failure mechanisms in the reactor cooling system, and provides minimal temperature drop radiative coupling to the TE array, as well as automatic, self-actuating removal of reactor afterheat. The question of how the failure of a fuel module heat pipe will affect neighboring fuel modules in the core is discussed, as is fission density peaking that occurs at the core/reflector interface. Results of neutronic calculations of the control margin available are described. Another issue that is addressed is that of helium generation in the heat pipes from neutron reactions in the core with the heat pipe fluid. Finally, the growth potential of the SABRE design to much higher powers is examined.

Ranken, W.A.; Koenig, D.R.

1983-01-01

56

Advanced Neutron Sources: Plant Design Requirements  

SciTech Connect

The Advanced Neutron Source (ANS) is a new, world class facility for research using hot, thermal, cold, and ultra-cold neutrons. At the heart of the facility is a 350-MW{sub th}, heavy water cooled and moderated reactor. The reactor is housed in a central reactor building, with supporting equipment located in an adjoining reactor support building. An array of cold neutron guides fans out into a large guide hall, housing about 30 neutron research stations. Office, laboratory, and shop facilities are included to provide a complete users facility. The ANS is scheduled to begin operation at the Oak Ridge National Laboratory at the end of the decade. This Plant Design Requirements document defines the plant-level requirements for the design, construction, and operation of the ANS. This document also defines and provides input to the individual System Design Description (SDD) documents. Together, this Plant Design Requirements document and the set of SDD documents will define and control the baseline configuration of the ANS.

Not Available

1990-07-01

57

The effect of quantized magnetic flux lines on the dynamics of superfluid neutron star cores  

Microsoft Academic Search

We investigate dynamical coupling time-scales of a neutron star's superfluid core, taking into account the interactions of quantized neutron vortices with quantized flux lines of the proton superconductor in addition to the previously considered scattering of the charged components against the spontaneous magnetization of the neutron vortex line. We compare the cases where vortex motion is constrained in different ways

T. Sidery; M. A. Alpar

2009-01-01

58

Systematic thermal reduction of neutronization in core-collapse supernovae  

NASA Astrophysics Data System (ADS)

We investigate to what extent the temperature dependence of the nuclear symmetry energy can affect the neutronization of the stellar core prior to neutrino trapping during gravitational collapse. To this end, we implement a one-zone simulation to follow the collapse until ?-equilibrium is reached and the lepton fraction remains constant. Since the strength of electron capture on the neutron-rich nuclei associated to the supernova scenario is still an open issue, we keep it as a free parameter. We find that the temperature dependence of the symmetry energy consistently yields a small reduction of deleptonization, which corresponds to a systematic effect on the shock wave energetics: the gain in dissociation energy of the shock has a small yet non-negligible value of about 0.4 foe (1 foe=10 erg) and this result is almost independent from the strength of nuclear electron capture. The presence of such a systematic effect and its robustness under changes of the parameters of the one-zone model are significant enough to justify further investigations with detailed numerical simulations of supernova explosions.

Fantina, A. F.; Donati, P.; Pizzochero, P. M.

2009-06-01

59

Conceptual tokamak design at high neutron fluence  

Microsoft Academic Search

For the future fusion reactor, it is important to design an experimental device that can be performed testing in-vessel components including tritium breeding modules relevant to the future fusion reactor with high neutron fluence. To realize this requirement, a conceptual tokamak design has been performed in accordance with plasma performance and shape at quasi-steady-state operation. One of the promising scenarios

M. Araki; S. Sato; I. Senda; J. Ohmori; T. Shoji

2001-01-01

60

Advanced Neutron Source: Plant Design Requirements  

SciTech Connect

The Advanced Neutron Source will be a new world-class facility for research using hot, thermal, cold, and ultra-cold neutrons. The heart of the facility will be a 330-MW (fission), heavy-water cooled and heavy-water moderated reactor. The reactor will be housed in a central reactor building, with supporting equipment located in an adjoining reactor support building. An array of cold neutron guides will fan out into a large guide hall, housing about 30 neutron research stations. Appropriate office, laboratory, and shop facilities will be included to provide a complete facility for users. The ANS is scheduled to begin operation at the Oak Ridge National Laboratory early in the next decade. This PDR document defines the plant-level requirements for the design, construction, and operation of ANS. It also defines and provides input to the individual System Design Description (SDD) documents. Together, this PDR document and the set of SDD documents will define and control the baseline configuration of ANS.

Not Available

1990-07-01

61

Characterization of Neutron Fields in the Experimental Fast Reactor Joyo Mk-Iii Core  

Microsoft Academic Search

In 2003, Joyo MK-III core was upgraded to increase the irradiation testing capability. This paper describes the details of distributions of neutron flux and reaction rate in the MK-III core that was measured by characterization tests during the first two operating cycles. The calculation accuracy of the core management codes HESTIA, TORT and MCNP, was also evaluated by the measured

Shigetaka Maeda; Chikara Ito; Yasushi Ohkawachi; Takashi Sekine; Takafumi Aoyama

2009-01-01

62

Global shielding analysis for the three-element core advanced neutron source reactor under normal operating conditions  

SciTech Connect

Two-dimensional discrete ordinates radiation transport calculations were performed for a model of the three-element core Advanced Neutron Source reactor design under normal operating conditions. The core consists of two concentric upper elements and a lower element radially centered in the annulus between the upper elements. The initial radiation transport calculations were performed with the DORT two-dimensional discrete ordinates radiation transport code using the 39-neutron-group/44-gamma-ray-group ANSL-V cross-section library, an S{sub 6} quadrature, and a P{sub 1} Legendre polynomial expansion of the cross sections to determine the fission neutron source distribution in the core fuel elements. These calculations were limited to neutron groups only. The final radiation transport calculations, also performed with DORT using the 39-neutron-group/44-gamma-ray-group ANSL-V cross-section library, an S{sub l0} quadrature, and a P{sub 3} Legendre polynomial expansion of the cross sections, produced neutron and gamma-ray fluxes over the full extent of the geometry model. Responses (or activities) at various locations in the model were then obtained by folding the appropriate response functions with the fluxes at those locations. Some comparisons were made with VENTURE-calculated (diffusion theory) 20-group neutron fluxes that were summed into four broad groups. Tne results were in reasonably good agreement when the effects of photoneutrons were not included, thus verifying the physics model upon which the shielding model was based. Photoneutrons increased the fast-neutron flux levels deep within the D{sub 2}0 several orders of magnitude. Results are presented as tables of activity values for selected radial and axial traverses, plots of the radial and axial traverse data, and activity contours superimposed on the calculational geometry model.

Slater, C.O.; Bucholz, J.A.

1995-08-01

63

Calculated Neutron and Gamma-Ray Spectra across the Prismatic Very High Temperature Reactor Core  

NASA Astrophysics Data System (ADS)

Neutron and gamma-ray flux spectra are calculated using the MCNP5 computer code and a one-sixth core model of a prismatic Very High Temperature Reactor based on the General Atomics Gas Turbine-Modular Helium Reactor. Spectra are calculated in the five inner reflector graphite block rings, three annular active core fuel rings, three outer graphite reflector block rings, and the core barrel. The neutron spectra are block and fuel pin averages and are calculated as a function of temperature and burnup. Also provided are the total, fast, and thermal radial profile fluxes and core barrel dpa rates.

Sterbentz, James W.

2009-08-01

64

Stars with neutron cores - The possibility of the existence of objects with a low neutrino luminosity  

NASA Astrophysics Data System (ADS)

The model of a red giant star with a neutron core proposed by Thorne and Zytkow (1975) is analyzed theoretically with respect to temporal evolution. The lifetime and accretion rate of the envelope surrounding neutron core are computed on the basis of boundary conditions. It is found that the strong neutrino emission which develops as the neutron core moves to deeper layers of the envelope implies temperatures greater than the upper limit identified by Thorne and Zytkow in their original formulation of the model. It is also found that allowing for the release of gravitational energy in the massive envelope results in the expansion of the possible outflow of material at a rate of about 0.00001 solar mass per year. It is concluded that only stars with hot neutron cores (greater than 10 to the 10th K) and a high neutrino luminosity could possibly exist, and their lifetime before collapse would be about 100 years.

Bisnovatyi-Kogan, G. S.; Lamzin, S. A.

1984-04-01

65

Neutronic design of a fission converter-based epithermal neutron beam for neutron capture therapy  

SciTech Connect

To meet the needs for neutron capture theory (NCT) irradiations, a high-intensity, high-quality fusion converter-based epithermal neutron beam has been designed for the MITR-II research reactor. This epithermal neutron beam, capable of delivering treatments in a few minutes with negligible background contamination from fast neutrons and photons, will be installed in the present thermal column and hohlraum of the 5-MW MITR-II research reactor. Spent or fresh MITR-II fuel elements will be used to fuel the converter. With a fission converter power of {approximately}80 kW using spent fuel, epithermal fluxes (1 eV < E < 10 keV) in excess of 10{sup 10} n/cm{sup 2} {center_dot} s are achievable at the target position with negligible photon and fast neutron contamination, i.e., <2 {times} 10{sup {minus}11}cGy-cm{sup 2}/n. With the currently available {sup 10}B delivery compound boronophenylalanine-fructose, average therapeutic ratios of {approximately}5 can be achieved using this beam for brain irradiations with deep effective penetration ({approximately}9.5 cm) and high dose rates of up to 400 to 600 RBE cGy/min. If NCT becomes an accepted therapy, fission converter-based beams constructed at existing reactors could meet a large fraction of the projected requirements for intense, low-background epithermal neutron beams at a relatively low cost. The results of an extensive set of neutronic design studies investigating all components of the beam are presented. These detailed studies can be useful as guidance for others who may wish to use the fission converter approach to develop epithermal beams for NCT.

Kiger, W.S. III; Sakamoto, S.; Harling, O.K. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1999-01-01

66

From Crust to Core:. a Brief Review of Quark Matter in Neutron Stars  

NASA Astrophysics Data System (ADS)

This paper provides a short overview of the multifaceted, possible role of quark matter for compact stars (neutron stars and strange quark matter stars). We began with a variational investigation of the maximum possible energy densities in the cores of neutron stars. This is followed by a brief discussion of the possible existence of quark matter in the cores of neutron stars and how such matter could manifest itself in neutron star observables. The possible presence of color superconducting strange quark matter nuggets in the crusts of neutron stars is reviewed next, and their impact on the pycnonuclear reaction rates in the crusts of neutron stars is discussed. The second part of the paper discusses the impact of ultra-strong electric fields on the bulk properties of strange quark matter stars and presents results of a preliminary study that models the thermal evolution of radio-quiet, X-ray bright, central compact objects (CCOs).

Weber, F.; Hamil, O.; Mimura, K.; Negreiros, R.

67

REVIEWS OF TOPICAL PROBLEMS: Cooling of neutron stars and superfluidity in their cores  

NASA Astrophysics Data System (ADS)

We study the heat capacity and neutrino emission reactions (direct and modified Urca processes, nucleon-nucleon bremsstrahlung, Cooper pairing of nucleons) in the supranuclear density matter of neutron star cores with superfluid neutrons and protons. Various superfluidity types are analysed (singlet-state pairing and two types of triplet-state pairing, without and with gap nodes at the nucleon Fermi surface). The results are used for cooling simulations of isolated neutron stars. Both the standard cooling and the cooling enhanced by the direct Urca process are strongly affected by nucleon superfluidity. Comparison of the cooling theory of isolated neutron stars with observations of their thermal radiation may give stringent constraints on the critical temperatures of the neutron and proton superfluidities in the neutron star cores.

Yakovlev, Dmitrii G.; Levenfish, Kseniya P.; Shibanov, Yurii A.

1999-08-01

68

Development and preliminary verification of the 3D core neutronic code: COCO  

SciTech Connect

As the recent blooming economic growth and following environmental concerns (China)) is proactively pushing forward nuclear power development and encouraging the tapping of clean energy. Under this situation, CGNPC, as one of the largest energy enterprises in China, is planning to develop its own nuclear related technology in order to support more and more nuclear plants either under construction or being operation. This paper introduces the recent progress in software development for CGNPC. The focus is placed on the physical models and preliminary verification results during the recent development of the 3D Core Neutronic Code: COCO. In the COCO code, the non-linear Green's function method is employed to calculate the neutron flux. In order to use the discontinuity factor, the Neumann (second kind) boundary condition is utilized in the Green's function nodal method. Additionally, the COCO code also includes the necessary physical models, e.g. single-channel thermal-hydraulic module, burnup module, pin power reconstruction module and cross-section interpolation module. The preliminary verification result shows that the COCO code is sufficient for reactor core design and analysis for pressurized water reactor (PWR). (authors)

Lu, H.; Mo, K.; Li, W.; Bai, N.; Li, J. [Reactor Design and Fuel Management Research Center, China Nuclear Power Technology Research Inst., 47F/A Jiangsu Bldg., Yitian Road, Futian District, Shenzhen (China)

2012-07-01

69

Core bit design reduces mud invasion, improves ROP  

SciTech Connect

A recently developed core bit reduces fluid invasion in the cut core by minimizing the exposure to the drilling fluid and by increasing the rate of penetration (ROP). A high ROP during coring is one of the major factors in reducing mud filtrate invasion in cores. This new low-invasion polycrystalline diamond compact (PDC) core bit was designed to achieve a higher ROP than conventional PDC core bits without detriment to the cutting structure. The paper describes the bit and its operation, results of lab tests, fluid dynamics, and results of field tests.

Clydesdale, G. (Security DBS, Aberdeen (United Kingdom)); Leseultre, A.; Lamine, E. (Security DBS, Brussels (Belgium))

1994-08-08

70

Potential of an accelerator-based neutron source for the logging of bore-hole cores  

NASA Astrophysics Data System (ADS)

The determination of gold in bore-hole cores has been investigated using neutron activation analysis with the reaction 197Au(n, ?)198Au. Comparisons between the results obtained by neutron activation and those obtained by fire assay show that the method is capable of great accuracy. The experimental results were obtained with a 252Cf source but the irradiation and counting times were far too long for a pracitical instrument. Extrapolations to fluxes available with modern accelerator sources of neutrons show that a suitable system would be capable of measuring the gold distribution in about 20 m of core per day.

Watterson, J. I. W.; Rahmanian, H.

1993-06-01

71

Effective delayed neutron fraction measurements in FCA-XIX cores by using modified Bennett method  

Microsoft Academic Search

As the part of the international benchmark experiment of the effective delayed neutron fraction held in the Fast Critical Assembly of the Japan Atomic Energy Research Institute, we measured the effective beta for the FCA XIX-1 (Uranium) core, XIX-2 (Plutonium\\/Natural Uranium) core, and XIX-3(Plutonium) core by using a modified Bennett method. This method was proposed by these authors to suppress

Shigeaki Okajima; Takeshi Sakurai

1999-01-01

72

Advanced BWR core component designs and the implications for SFD analysis  

SciTech Connect

Prior to the DF-4 boiling water reactor (BWR) severe fuel damage (SFD) experiment conducted at the Sandia National Laboratories in 1986, no experimental data base existed for guidance in modeling core component behavior under postulated severe accident conditions in commercial BWRs. This paper will present the lessons learned from the DF-4 experiment (and subsequent German CORA BWR SFD tests) and the impact on core models in the current generation of SFD codes. The DF-4 and CORA BWR test assemblies were modeled on the core component designs circa 1985; that is, the 8 x 8 fuel assembly with two water rods and a cruciform control blade constructed of B{sub 4}C-filled tubelets. Within the past ten years, the state-of-the-art with respect to BWR core component development has out-distanced the current SFD experimental data base and SFD code capabilities. For example, modern BWR control blade design includes hafnium at the tips and top of each control blade wing for longer blade operating lifetimes; also water rods have been replaced by larger water channels for better neutronics economy; and fuel assemblies now contain partial-length fuel rods, again for better neutronics economy. This paper will also discuss the implications of these advanced fuel assembly and core component designs on severe accident progression and on the current SFD code capabilities.

Ott, L.J.

1997-02-01

73

Advanced Neutron Source radiological design criteria  

SciTech Connect

The operation of the proposed Advanced Neutron Source (ANS) facility will present a variety of radiological protection problems. Because it is desired to design and operate the ANS according to the applicable licensing standards of the Nuclear Regulatory Commission (NRC), it must be demonstrated that the ANS radiological design basis is consistent not only with state and Department of Energy (DOE) and other usual federal regulations, but also, so far as is practicable, with NRC regulations and with recommendations of such organizations as the Institute of Nuclear Power Operations (INPO) and the Electric Power Research Institute (EPRI). Also, the ANS radiological design basis is in general to be consistent with the recommendations of authoritative professional and scientific organizations, specifically the National Council on Radiation Protection and Measurements (NCRP) and the International Commission on Radiological Protection (ICRP). As regards radiological protection, the principal goals of DOE regulations and guidance are to keep occupational doses ALARA [as low as (is) reasonably achievable], given the current state of technology, costs, and operations requirements; to control and monitor contained and released radioactivity during normal operation to keep public doses and releases to the environment ALARA; and to limit doses to workers and the public during accident conditions. Meeting these general design objectives requires that principles of dose reduction and of radioactivity control by employed in the design, operation, modification, and decommissioning of the ANS. The purpose of this document is to provide basic radiological criteria for incorporating these principles into the design of the ANS. Operations, modification, and decommissioning will be covered only as they are affected by design.

Westbrook, J.L.

1995-08-01

74

Neutronic optimization of solid breeder blankets for STARFIRE design  

SciTech Connect

Extensive neutronic tradeoff studies were carried out to define and optimize the neutronic performance of the different solid breeder options for the STARFIRE blanket design. A set of criteria were employed to select the potential blanket materials. The basic criteria include the neutronic performance, tritium-release characteristics, material compatibility, and chemical stability. Three blanket options were analyzed. The first option is based on separate zones for each basic blanket function where the neutron multiplier is kept in a separate zone. The second option is a heterogeneous blanket type with two tritium breeder zones. In the first zone the tritium breeder is assembled in a neutron multiplier matrix behind the first wall while the second zone has a neutron moderator matrix instead of the neutron multiplier. The third blanket option is similar to the second concept except the tritium breeder and the neutron multiplier form a homogeneous mixture.

Gohar, Y.; Abdou, M.A.

1980-01-01

75

Monte Carlo code for neutron scattering instrumentation design and analysis  

SciTech Connect

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) at the Los Alamos National Laboratory (LANL). The development of next generation, accelerator based neutron sources calls for the design of new instruments for neutron scattering studies of materials. It will be necessary, in the near future, to evaluate accurately and rapidly the performance of new and traditional neutron instruments at short- and long-pulse spallation neutron sources, as well as continuous sources. We have developed a code that is a design tool to assist the instrument designer model new or existing instruments, test their performance, and optimize their most important features.

Daemen, L.; Fitzsimmons, M.; Hjelm, R.; Olah, G.; Roberts, J.; Seeger, P.; Smith, G.; Thelliez, T.

1996-09-01

76

Maximum mass of a hot neutron star with a quark core  

NASA Astrophysics Data System (ADS)

We have considered a hot neutron star with a quark core, a mixed phase of quark-hadron matter, and a hadronic matter crust and have determined the equation of state of the hadronic phase and the quark phase. We have then found the equation of state of the mixed phase under the Gibbs conditions. Finally, we have computed the structure of a hot neutron star with a quark core and compared our results with those of the neutron star without a quark core. For the quark matter calculations, we have used the MIT bag model in which the total energy of the system is considered as the kinetic energy of the particles plus a bag constant. For the hadronic matter calculations, we have used the lowest order constrained variational formalism. Our calculations show that the results for the maximum gravitational mass of a hot neutron star with a quark core are substantially different from those of a neutron star without the quark core.

Yazdizadeh, Tayebeh; Bordbar, Gholam Hossein

2011-04-01

77

Determination of the kinetic parameters of the CALIBAN metallic core reactor from stochastic neutron measurements  

SciTech Connect

Several experimental devices are operated by the Criticality and Neutron Science Research Dept. of the CEA Valduc Laboratory. One of these is the Caliban metallic core reactor. The purpose of this study is to develop and perform experiments allowing to determinate some of fundamental kinetic parameters of the reactor. The prompt neutron decay constant and particularly its value at criticality can be measured with reactor noise techniques such as Rossi-{alpha} and Feynman variance-to-mean methods. Subcritical, critical, and even supercritical experiments were performed. Fission chambers detectors were put nearby the core and measurements were analyzed with the Rossi-{alpha} technique. A new value of the prompt neutron decay constant at criticality was determined, which allows, using the Nelson number method, new evaluations of the effective delayed neutron fraction and the in core neutron lifetime. As an introduction of this paper, some motivations of this work are given in part 1. In part 2, principles of the noise measurements experiments performed at the CEA Valduc Laboratory are reminded. The Caliban reactor is described in part 3. Stochastic neutron measurements analysis techniques used in this study are then presented in part 4. Results of fission chamber experiments are summarized in part 5. Part 6 is devoted to the current work, improvement of the experimental device using He 3 neutron detectors and first results obtained with it. Finally, conclusions and perspectives are given in part 7. (authors)

Casoli, P.; Authier, N.; Chapelle, A. [Commissariat a l'Energie Atomique et Aux Energies Alternatives, CEA, DAM, F-21120 Is sur Tille (France)

2012-07-01

78

Basic criticality relations for gas core design  

SciTech Connect

Minimum critical fissile concentrations are calculated for U-233, U-235, Pu-239, and Am-242m mixed homogeneously with hydrogen at temperatures to 15,000K. Minimum critical masses of the same mixtures in a 1000 liter sphere are also calculated. It is shown that propellent efficiencies of a gas core fizzler engine using Am-242m as fuel would exceed those in a solid core engine as small as 1000L operating at 100 atmospheres pressure. The same would be true for Pu-239 and possibly U-233 at pressures of 1000 atm. or at larger volumes.

Tanner, J.E.

1992-05-22

79

Novel kind of DSP design method based on IP core  

Microsoft Academic Search

With the pressure from the design productivity and various special applications, original design method for DSP can no longer keep up with the required speed. A novel design method is needed urgently. Intellectual Property (IP) reusing is a tendency for DSP design, but simple plug-and-play IP cores approaches almost never work. Therefore, appropriate control strategies are needed to connect all

Qiaoyan Yu; Peng Liu; Weidong Wang; Xiang Hong; Jicheng Chen; Jianzhong Yuan; Keming Chen

2004-01-01

80

Design of the Clinch River Breeder Reactor Plant heterogeneous core  

SciTech Connect

The original core design for the Clinch River Breeder Reactor Plant (CRBRP) was a homogeneous core, as are essentially all of present day liquid metal fast breeder reactors. A study was undertaken to determine if a rearrangement of the core into a heterogeneous configuration, with fertile elements interspersed within the fueled zone, would improve the breeding ratio significantly without excessive adverse effects on other aspects of the design. The result of the study was that the heterogeneous concept improved not only the breeding ratio and doubling time, but also the control assembly worth, core restraint response, and the fuel cycle cost. This paper describes the design evolution and the major effects of the change from a homogeneous to a heterogeneous core in the Clinch River Breeder Reactor Plant.

Dickson, P.W. Jr.; Arnold, W.H.

1982-01-01

81

Designing systems-on-chip using cores  

Microsoft Academic Search

Leading-edge systems-on-chip (SoC) being designed today could reach 20 Million gates and 0.5 to 1 GHz operating frequency. In order to implement such systems, designers are increasingly relying on reuse of Intellectual property (IP) blocks. Since IP blocks are pre-designed and pre-verified, the designer can concentrate on the complete system without having to worry about the correctness or performance of

Reinaldo A. Bergamaschi; William R. Lee

2000-01-01

82

The Encapsulated Nuclear Heat Source (ENHS) Reactor Core Design  

SciTech Connect

A once-for-life, uniform composition, blanket-free and fuel-shuffling-free reference core has been designed for the Encapsulated Nuclear Heat Source (ENHS) to provide the design goals of a nearly zero burnup reactivity swing throughout {approx}20 yr of full-power operation up to the peak discharge burnup of more than 100 GWd/t HM. What limits the core life is radiation damage to the HT-9 structural material. The temperature coefficients of reactivity are all negative, except for that of the coolant expansion. However, the negative reactivity coefficient associated with the radial expansion of the core structure can compensate for the coolant thermal expansion. The void coefficient is positive but of no safety concern because the boiling temperature of lead or lead-bismuth is so high that there is no conceivable mechanism for the introduction of significant void fraction into the core. The core reactivity coefficients, reactivity worth, and power distributions are almost constant throughout the core life.It was found possible to design such once-for-life cores using different qualities of Pu and transuranics as long as U is used as the primary fertile material. It is also feasible to design ENHS cores using nitride rather than metallic fuel. Relative to the reference metallic fuel core, nitride fuel cores offer up to {approx}25% higher discharge burnup and longer life, up to {approx}38% more energy per core, a significantly more negative Doppler reactivity coefficient, and less positive coolant expansion and coolant void reactivity coefficient but a somewhat smaller negative fuel expansion reactivity coefficient. The pitch-to-diameter ratio (1.45 of the nitride fuel cores using enriched N) is larger than that (1.36) for the reference metallic fuel core, implying a reduction of the coolant friction loss, thus enabling an increase in the power level that can be removed from the core by natural circulation cooling.It is also possible to design Pu-U(10Zr) fueled ENHS-type cores using Na as the primary coolant with either Na or Pb-Bi secondary coolants. The Na-cooled cores feature a tighter lattice and are therefore more compact but have spikier power distribution, more positive coolant temperature reactivity coefficients, and smaller reactivity worth of the control elements.

Hong, Ser Gi [Korea Atomic Energy Research Institute (Korea, Republic of); Greenspan, Ehud [University of California, Berkeley (United States); Kim, Yeong Il [Korea Atomic Energy Research Institute (Korea, Republic of)

2005-01-15

83

Design and characterisation of a pulsed neutron interrogation facility.  

PubMed

The Joint Research Centre recently obtained a license to operate a new experimental device intended for research in the field of nuclear safeguards. The research projects currently being planned for the new device includes mass determination of fissile materials in matrices and detection of contraband non-nuclear materials. The device incorporates a commercial pulsed neutron generator and a large graphite mantle surrounding the sample cavity. In this configuration, a relatively high thermal neutron flux with a long lifetime is achieved inside the sample cavity. By pulsing the neutron generator, a sample may be interrogated by a pure thermal neutron flux during repeated time periods. The paper reports on the design of the new device and the pulsed fast and thermal neutron source. The thermal neutron flux caused by the neutron generator and the graphite structure has been characterised by foil activation, fission chamber and (3)He proportional counter measurements. PMID:17496298

Favalli, A; Pedersen, B

2007-05-12

84

Design Analyses and Shielding of HFIR Cold Neutron Scattering Instruments  

SciTech Connect

Research reactor geometries and special characteristics present unique dosimetry analysis and measurement issues. The introduction of a cold neutron moderator and the production of cold neutron beams at the Oak Ridge National Laboratory High Flux Isotope Reactor have created the need for modified methods and devices for analyzing and measuring low energy neutron fields (0.01 to 100 meV). These methods include modifications to an MCNPX version to provide modeling of neutron mirror reflection capability. This code has been used to analyze the HFIR cold neutron beams and to design new instrument equipment that will use the beams. Calculations have been compared with time-of-flight measurements performed at the start of the neutron guides and at the end of one of the guides. The results indicate that we have a good tool for analyzing the transport of these low energy beams through neutron mirror and guide systems for distance up to 60 meters from the reactor. (authors)

Gallmeier, F.X.; Selby, D.L.; Winn, B.; Stoica, D.; Jones, A.B.; Crow, L. [Neutron Sciences Directorate, Oak Ridge National Laboratory (United States)

2011-07-01

85

Reactor physics analyses of the advanced neutron source three-element core  

SciTech Connect

A reactor physics analysis was performed for the Advanced Neutron Source reactor with a three-element core configuration. The analysis was performed with a two-dimensional r-z 20-energy-group finite-difference diffusion theory model of the 17-d fuel cycle. The model included equivalent r-z geometry representations of the central control rods, the irradiation and production targets, and reflector components. Calculated quantities include fuel cycle parameters, fuel element power distributions, unperturbed neutron fluxes in the reflector and target regions, reactivity perturbations, and neutron kinetics parameters.

Gehin, J.C.

1995-08-01

86

Thermal hydraulic response of the Advanced Neutron Source Reactor to piping breaks near the core region  

SciTech Connect

This paper describes the application of the RELAP5 thermal hydraulic code to a highly subcooled, plate type reactor typical of many research and production reactor systems. The specific system modeled is the latest design of the Advanced Neutron Source Reactor (ANSR). A discussion of the model as well as the results from several loss-of-coolant accident (LOCA) scenarios is included. The results indicate that this system responds to these accidents by a very rapid depressurization (over a few milliseconds) followed by a pressure recovery due to fluid inertia. In addition, the effect of including a gas pressurized accumulator in the system is addressed. The results show that tracking the pressure response of the system over these short time scales will be a key to accurately predicting the thermal response of the core of the reactor. Further, the break time scale as well as the time scale of the thermal response of the core, presently treated conservatively, will be additional important areas of study. 22 refs.

Chen, N.C.J.; Williams, P.T.; Yoder, G.L.

1992-01-01

87

IRSN working program status on tools for evaluation of SFR cores static neutronics safety parameters  

SciTech Connect

As technical support of the French Nuclear Safety Authority, IRSN will be in charge of safety assessment of any future project of Sodium Fast Reactor (SFR) that could be built in France. One of the main safety topics will deal with reactivity control. Since the design and safety assessment of the last two SFR plants in France (Phenix and Superphenix, more than thirty years ago), methods, codes and safety objectives have evolved. That is why a working program on core neutronic simulations has been launched in order to be able to evaluate accuracy of future core characteristics computations. The first step consists in getting experienced with the ERANOS well-known deterministic code used in the past for Phenix and Superphenix. Then Monte-Carlo codes have been tested to help in the interpretation of ERANOS results and to define what place this kind of codes can have in a new SFR safety demonstration. This experience is based on open benchmark computations. Different cases are chosen to cover a wide range of configurations. The paper shows, as an example, criticality results obtained with ERANOS, SCALE and MORET, and the first conclusions based on these results. In the future, this work will be extended to other safety parameters such as sodium void and Doppler effects, kinetic parameters or flux distributions. (authors)

Ivanov, E.; Tiberi, V.; Ecrabet, F.; Chegrani, Y.; Canuti, E.; Bisogni, D.; Sargeni, A.; Bernard, F. [Institut de Radioprotection et de Surete Nucleaire IRSN, BP 17, 92262 Fontenay-aux-roses (France)

2012-07-01

88

Core and Refueling Design Studies for the Advanced High Temperature Reactor  

SciTech Connect

The Advanced High Temperature Reactor (AHTR) is a design concept for a central generating station type [3400 MW(t)] fluoride-salt-cooled high-temperature reactor (FHR). The overall goal of the AHTR development program is to demonstrate the technical feasibility of FHRs as low-cost, large-size power producers while maintaining full passive safety. This report presents the current status of ongoing design studies of the core, in-vessel structures, and refueling options for the AHTR. The AHTR design remains at the notional level of maturity as important material, structural, neutronic, and hydraulic issues remain to be addressed. The present design space exploration, however, indicates that reasonable options exist for the AHTR core, primary heat transport path, and fuel cycle provided that materials and systems technologies develop as anticipated. An illustration of the current AHTR core, reactor vessel, and nearby structures is shown in Fig. ES1. The AHTR core design concept is based upon 252 hexagonal, plate fuel assemblies configured to form a roughly cylindrical core. The core has a fueled height of 5.5 m with 25 cm of reflector above and below the core. The fuel assembly hexagons are {approx}45 cm across the flats. Each fuel assembly contains 18 plates that are 23.9 cm wide and 2.55 cm thick. The reactor vessel has an exterior diameter of 10.48 m and a height of 17.7 m. A row of replaceable graphite reflector prismatic blocks surrounds the core radially. A more complete reactor configuration description is provided in Section 2 of this report. The AHTR core design space exploration was performed under a set of constraints. Only low enrichment (<20%) uranium fuel was considered. The coated particle fuel and matrix materials were derived from those being developed and demonstrated under the Department of Energy Office of Nuclear Energy (DOE-NE) advanced gas reactor program. The coated particle volumetric packing fraction was restricted to at most 40%. The pressure drop across the core was restricted to no more than 1.5 atm during normal operation to minimize the upward force on the core. Also, the flow velocity in the core was restricted to 3 m/s to minimize erosion of the fuel plates. Section 3.1.1 of this report discusses the design restrictions in more detail.

Holcomb, David Eugene [ORNL; Ilas, Dan [ORNL; Varma, Venugopal Koikal [ORNL; Cisneros, Anselmo T [ORNL; Kelly, Ryan P [ORNL; Gehin, Jess C [ORNL

2011-09-01

89

Advanced Neutron Source design: Burnout heat flux correlation development  

SciTech Connect

In the Advanced Neutron Source Reactor (ANSR) fuel element region, heat fluxes will be elevated. Early designs corresponded to average and estimated hot-spot fluxes of 11-12 and 21-22 MW/m/sup 2/, respectively. Design changes under consideration may lower these values to about 9 and 17 MW/m/sup 2/. In either event, the development of a satisfactory burnout heat flux correlation is an important element among the many thermal-hydraulic design issues, since the critical power ration will depend in part on its validity. Relatively little work in the area of subcooled-flow burnout has been published over the past 12 years. We have compared seven burnout correlations and modifications thereof with several sets of experimental data, of which the most relevant to the ANS core are presently those referenced. The best overall agreement between the correlations tested and these data is currently provided by a modification of Thorgerson's correlation. 7 refs., 1 tab.

Gambill, W.R.; Mochizuki, T.

1988-01-01

90

Fuel and Core Design Experiences in Cofrentes NPP  

SciTech Connect

The electricity market deregulation in Spain is increasing the need for innovations in nuclear power generation, which can be achieved in the fuel area by improving fuel and core designs and by introducing vendors competition. Iberdrola has developed the GIRALDA methodology for design and licensing of Cofrentes reloads, and has introduced mixed cores with fuel from different vendors. The application of GIRALDA is giving satisfactory results, and is showing its capability to adequately reproduce the core behaviour. The nuclear design team is acquiring an invaluable experience and a deep knowledge of the core, very useful to support cycle operation. Continuous improvements are expected for the future in design strategies as well as in the application of new technologies to redesign the methodology processes. (authors)

Garcia-Delgado, L.; Lopez-Carbonell, M.T.; Gomez-Bernal, I. [Iberdrola Generacion, Nuclear Fuel Department, Hermosilla 3, 28001 Madrid (Spain)

2002-07-01

91

Cooling of hybrid neutron stars and hypothetical self-bound objects with superconducting quark cores  

Microsoft Academic Search

We study the consequences of superconducting quark cores (with color-flavor-locked phase as representative example) for the evolution of temperature profiles and cooling curves in quark-hadron hybrid stars and in hypothetical self-bound objects having no hadron shell (quark core neutron stars). The quark gaps are varied from 0 to Deltaq =50 MeV. For hybrid stars we find time scales of 1\\/5,

D. Blaschke; H. Grigorian; D. N. Voskresensky

2001-01-01

92

Higher order polynomial expansion nodal method for hexagonal core neutronics analysis  

Microsoft Academic Search

A higher-order polynomial expansion nodal(PEN) method is newly formulated as a means to improve the accuracy of the conventional PEN method solutions to multi-group diffusion equations in hexagonal core geometry. The new method is applied to solving various hexagonal core neutronics benchmark problems. The computational accuracy of the higher order PEN method is then compared with that of the conventional

Jin Young Cho; Chang Hyo Kim

1998-01-01

93

Conceptual design of an RFQ accelerator-based neutron source for boron neutron-capture therapy  

SciTech Connect

We present a conceptual design of a low-energy neutron generator for treatment of brain tumors by boron neutron capture theory (BNCT). The concept is based on a 2.5-MeV proton beam from a radio-frequency quadrupole (RFQ) linac, and the neutrons are produced by the /sup 7/Li(p,n)/sup 7/Be reaction. A liquid lithium target and modulator assembly are designed to provide a high flux of epithermal neutrons. The patient is administered a tumor-specific /sup 10/Be-enriched compound and is irradiated by the neutrons to create a highly localized dose from the reaction /sup 10/B(n,..cap alpha..)/sup 7/Li. An RFQ accelerator-based neutron source for BNCT is compact, which makes it practical to site the facility within a hospital. 11 refs., 5 figs., 1 tab.

Wangler, T.P.; Stovall, J.E.; Bhatia, T.S.; Wang, C.K.; Blue, T.E.; Gahbauer, R.A.

1989-01-01

94

The Encapsulated Nuclear Heat Source (ENHS) Reactor Core Design  

Microsoft Academic Search

A once-for-life, uniform composition, blanket-free and fuel-shuffling-free reference core has been designed for the Encapsulated Nuclear Heat Source (ENHS) to provide the design goals of a nearly zero burnup reactivity swing throughout â20 yr of full-power operation up to the peak discharge burnup of more than 100 GWd\\/t HM. What limits the core life is radiation damage to the HT-9

Ser Gi Hong; Ehud Greenspan; Yeong Il Kim

2005-01-01

95

De novo design of the hydrophobic core of ubiquitin.  

PubMed Central

We have previously reported the development and evaluation of a computational program to assist in the design of hydrophobic cores of proteins. In an effort to investigate the role of core packing in protein structure, we have used this program, referred to as Repacking of Cores (ROC), to design several variants of the protein ubiquitin. Nine ubiquitin variants containing from three to eight hydrophobic core mutations were constructed, purified, and characterized in terms of their stability and their ability to adopt a uniquely folded native-like conformation. In general, designed ubiquitin variants are more stable than control variants in which the hydrophobic core was chosen randomly. However, in contrast to previous results with 434 cro, all designs are destabilized relative to the wild-type (WT) protein. This raises the possibility that beta-sheet structures have more stringent packing requirements than alpha-helical proteins. A more striking observation is that all variants, including random controls, adopt fairly well-defined conformations, regardless of their stability. This result supports conclusions from the cro studies that non-core residues contribute significantly to the conformational uniqueness of these proteins while core packing largely affects protein stability and has less impact on the nature or uniqueness of the fold. Concurrent with the above work, we used stability data on the nine ubiquitin variants to evaluate and improve the predictive ability of our core packing algorithm. Additional versions of the program were generated that differ in potential function parameters and sampling of side chain conformers. Reasonable correlations between experimental and predicted stabilities suggest the program will be useful in future studies to design variants with stabilities closer to that of the native protein. Taken together, the present study provides further clarification of the role of specific packing interactions in protein structure and stability, and demonstrates the benefit of using systematic computational methods to predict core packing arrangements for the design of proteins.

Lazar, G. A.; Desjarlais, J. R.; Handel, T. M.

1997-01-01

96

Neutron single-particle strength outside the N=50 core  

NASA Astrophysics Data System (ADS)

The single-neutron properties of N = 51 nuclei have been studied with the (d,p) and (?,3He) reactions, at beam energies of 15 and 50 MeV respectively, on 88Sr, 90Zr, and 92Mo targets. The light reaction products were momentum analyzed using a conventional magnetic spectrometer. Additionally, the 2H(86Kr,p) reaction was measured at a beam energy of 10 MeV/u, where outgoing light ions were analyzed using a helical-orbit spectrometer. Absolute cross sections and angular distributions corresponding to the population of different final states in the heavy product were obtained for each reaction. Spectroscopic factors were extracted and centroids of the single-particle strength were deduced. The observations appear consistent with calculations based on an evolution of single-particle structure driven by the nucleon-nucleon forces acting between valence protons and neutrons.

Sharp, D. K.; Kay, B. P.; Thomas, J. S.; Freeman, S. J.; Schiffer, J. P.; Back, B. B.; Bedoor, S.; Bloxham, T.; Clark, J. A.; Deibel, C. M.; Hoffman, C. R.; Howard, A. M.; Lighthall, J. C.; Marley, S. T.; Mitchell, A. J.; Otsuka, T.; Parker, P. D.; Rehm, K. E.; Shetty, D. V.; Wuosmaa, A. H.

2013-01-01

97

Device for Supporting the Core of a Fast Neutron Reactor.  

National Technical Information Service (NTIS)

The object of the invention is a supporting device for the core of a fast reactor cooled by a molten sodium circulation comprising a tank, a flooring mounted to this tank, a grid equipped with studs for the entry of the fuel elements, the grid which is su...

J. Lleres J. P. Martin M. Perona R. Venot

1977-01-01

98

Verification of JUPITER Standard Analysis Method for Upgrading Joyo MK-III Core Design and Management  

NASA Astrophysics Data System (ADS)

In the experimental fast reactor Joyo, loading of irradiation test rigs causes a decrease in excess reactivity because the rigs contain less fissile materials than the driver fuel. In order to carry out duty operation cycles using as many irradiation rigs as possible, it is necessary to upgrade the core performance to increase its excess reactivity and irradiation capacity. Core modification plans have been considered, such as the installation of advanced radial reflectors and reduction of the number of control rods. To implement such core modifications, it is first necessary to improve the prediction accuracy in core design and to optimize safety margins. In the present study, verification of the JUPITER fast reactor standard analysis method was conducted through a comparison between the calculated and the measured Joyo MK-III core characteristics, and it was concluded that the accuracy for a small sodium-cooled fast reactor with a hard neutron spectrum was within 5 % of unity. It was shown that, the performance of the irradiation bed core could be upgraded by the improvement of the prediction accuracy of the core characteristics and optimization of safety margins.

Maeda, Shigetaka; Ito, Chikara; Sekine, Takashi; Aoyama, Takafumi

99

Design of low-energy neutron beams for boron neutron capture synovectomy  

NASA Astrophysics Data System (ADS)

A novel application of the 10B(n, (alpha) )7Li nuclear reaction for the treatment of rheumatoid arthritis is under development. this application, called Boron Neutron Capture Synovectomy (BNCS), is briefly described here and the differences between BNCS and Boron Neutron Capture Therapy (BNCT) are discussed in detail. These differences lead to substantially altered demands on neutron beam design for each therapy application. In this paper the considerations for neutron beam design for the treatment of arthritic joints via BNCS are discussed, and comparisons with the design requirements for BNCT are made. This is followed by a description of potential moderator/reflector assemblies that are calculated to produce intense, high- quality neutron beams based on the 7Li(p,n) accelerator- based reactions. Total therapy time and therapeutic ratios are given as a function of both moderator length and boron concentration. Finally, a means of carrying out multi- directional irradiations of arthritic joints is proposed.

Yanch, Jacquelyn C.; Shefer, Ruth E.; Binello, E.

1997-02-01

100

Development of an asymmetric multiple position neutron source (AMPNS) method for monitoring the criticality of the degraded reactor core  

Microsoft Academic Search

An analytical\\/experiment method was developed to monitor the subcritical reactivity and unfold the k\\/sub infinity\\/ distribution of a degraded reactor core. The method uses several fixed neutron detectors and a Cf-252 neutron source placed sequentially in multiple positions in the core. Therefore, it is called the asymmetric multiple position neutron source (AMPNS) method. The AMPNS method employs the nucleonic codes

1984-01-01

101

Optimum design of single core shear walls  

Microsoft Academic Search

Design of reinforced concrete thin walled open sections subjected to combined loading such as axial force, biaxial bending moment and torsional moment is cumbersome. This is due to the fact that such structures possess very little torsional rigidity and the plane cross section does not remain plane after the deformation. In this study, an algorithm is developed for the optimum

S. S. Al-Mosawi; M. P. Saka

1999-01-01

102

Preliminary fracture analysis of the core pressure boundary tube for the Advanced Neutron Source Research Reactor  

SciTech Connect

The outer core pressure boundary tube (CPBT) of the Advanced neutron Source (ANS) reactor being designed at Oak Ridge National Laboratory is currently specified as being composed of 6061-T6 aluminum. ASME Boiler and Pressure Vessel Code fracture analysis rules for nuclear components are based on the use of ferritic steels; the expressions, tables, charts and equations were all developed from tests and analyses conducted for ferritic steels. Because of the nature of the Code, design with thin aluminum requires analytical approaches that do not directly follow the Code. The intent of this report is to present a methodology comparable to the ASME Code for ensuring the prevention of nonductile fracture of the CPBT in the ANS reactor. 6061-T6 aluminum is known to be a relatively brittle material; the linear elastic fracture mechanics (LEFM) approach is utilized to determine allowable flaw sizes for the CPBT. A J-analysis following the procedure developed by the Electric Power Research Institute was conducted as a check; the results matched those for the LEFM analysis for the cases analyzed. Since 6061-T6 is known to embrittle when irradiated, the reduction in K{sub Q} due to irradiation is considered in the analysis. In anticipation of probable requirements regarding maximum allowable flaw size, a survey of nondestructive inspection capabilities is also presented. A discussion of probabilistic fracture mechanics approaches, principally Monte Carlo techniques, is included in this report as an introduction to what quantifying the probability of nonductile failure of the CPBT may entail.

Schulz, K.C. [Univ. of Turabo, Gurabo, Puerto (Puerto Rico). College of Engineering; Yahr, G.T. [Oak Ridge National Lab., TN (United States)

1995-08-01

103

Sensitivity Degradation Characteristics of In-core Neutron Detector for Heavy Water Reactor, Fugen NPP  

SciTech Connect

Fugen nuclear power plant is a 165 MWe, heavy water-moderated, boiling light water-cooled, pressure tube-type reactor developed by JNC, which is the world's first thermal neutron power reactor to utilize mainly Uranium and Plutonium mixed oxide (MOX) fuel. Fugen has been loaded a total of 726 MOX fuel assemblies since the initial core in 1978. Each in-core neutron detector assembly of Fugen composed of four Local Power Monitors (LPM) is located at sixteen positions in the area of heavy water moderator in the core and monitors its power distribution during operation. The thermal neutron flux of Fugen is relatively higher than that of Boiling Water Reactor (BWR), therefore LPM, which is comprised of a fission chamber, degrades more quickly than that of BWR. An Improved Long-life LPM (LLPM) pasted inner surface wall of the chamber with {sup 234}U/{sup 235}U at a ratio of 4 to 1 had been developed through the irradiation test at Japan Material Test Reactor (JMTR). The {sup 234}U is converted to {sup 235}U with absorption of neutron, and compensates the consumption of {sup 235}U. LPM has been loaded to the initial core of Fugen since 1978. JNC had evaluated its sensitivity degradation characteristics through the accumulated irradiation data and the parametric survey for {sup 234}U and {sup 235}U. Based on the experience of evaluation for sensitivity degradation, JNC has applied shuffling operation of LPM assemblies during an annual inspection outage to reduce the operating cost. This operation realizes the reduction of replacing number of LPM assemblies and volume of radioactive waste. This paper describes the sensitivity degradation characteristics of in-core neutron detector and the degradation evaluation methods established in Fugen. (authors)

Tsuyoshi Okawa; Naoyuki Yomori [Japan Nuclear Cycle Development Institute (Japan)

2002-07-01

104

Design of a RISC Microcontroller Core in 48 Hours  

Microsoft Academic Search

In this paper we present a design case study using Handel-C—a recently developed programming language for compilation of high-level programs directly into FPGA hardware. The design is an 8-bit RISC microcontroller core with 33 instructions, prescaler and a programmable timer. Handel-C was used throughout the entire design and debugging flow. The RISC microcontroller design was implemented in on the XESS

D. ulÍk; M. Vasilko; P. Fuchs

105

Characterization of Neutron Fields in the Experimental Fast Reactor Joyo Mk-Iii Core  

NASA Astrophysics Data System (ADS)

In 2003, Joyo MK-III core was upgraded to increase the irradiation testing capability. This paper describes the details of distributions of neutron flux and reaction rate in the MK-III core that was measured by characterization tests during the first two operating cycles. The calculation accuracy of the core management codes HESTIA, TORT and MCNP, was also evaluated by the measured data. The calculated fission rates of 235U by HESTIA agreed well with the measured one within approximately 4% in the fuel region. MCNP could simulate within 6% in the central non-fuel irradiation test subassembly and the radial reflector region, while large discrepancies were obtained in TORT results. Hence, the precise geometry model was effective in evaluating the neutron spectrum and the flux at such locations.

Maeda, Shigetaka; Ito, Chikara; Ohkawachi, Yasushi; Sekine, Takashi; Aoyama, Takafumi

2009-08-01

106

Simulation of Fast Neutronics in an Accelerator-Driven Sub-Critical Core  

NASA Astrophysics Data System (ADS)

Accelerator-driven subcritical fission in a molten salt core (ADSMS) is being developed as a technology for green nuclear power. ADSMS burns its fertile fuel to completion, it cannot melt down, and it destroys long-lived minor actinides. The ADSMS core consists of a vessel filled with a molten salt eutectic of UCl3 and NaCl. The fast neutronics of ADSMS makes possible two unique benefits: isobreeding, a steady-state equilibrium in which ^238U is bred to ^239Pu and the ^239Pu fissions, and destruction of minor actinides, in which fission of the intermediary nuclides dominates of breeding. Results of simulations of the fast neutronics in the ADSMS core will be presented.

Gwyn Rosaire, C.; Sattarov, Akhdiyor; McIntyre, Peter; Tsvetkov, Pavel

2011-10-01

107

Neutronic calculations for the conversion to LEU of a research reactor core  

SciTech Connect

For a five-year transitional period the Greek Research Reactor (GRR-1) was operating with a mixed core, containing both Low Enrichment (LEU) and High Enrichment (HEU) Uranium MTR- type fuel assemblies. The neutronic study of the GRR-1 conversion to LEU has been performed using a code system comprising the core-analysis code CITATION-LDI2 and the cell-calculation modules XSDRNPM and NITAWL-II of the SCALE code. A conceptual LEU core configuration was defined and analyzed with respect to the three dimensional multi-group neutron fluxes, the power distribution, the control-rod worth and the compliance with pre-defined Operation Limiting Conditions. Perturbation calculations and reactivity feedback computations were also carried out to provide input to a subsequent thermal-hydraulic study. (author)

Varvayanni, M.; Catsaros, N.; Stakakis, E. [National Center for Scientific Research 'DEMOKRITOS', 153 10 Aghia Paraskevi (Greece); Grigoriadis, D. [National Center for Scientific Research 'DEMOKRITOS', 153 10 Aghia Paraskevi (Greece); Department of Mechanical and Manufacturing Engineering, University of Cyprus, P.O. Box 20537, Nicosia 1678 (Cyprus)

2008-07-15

108

A Method Using Nuclear Emulsions for Measuring the Anisotropy of Fast Neutron Fluxes due to Arrangement of Fast Core Cell  

Microsoft Academic Search

Measurements using nuclear emulsions have been made on the neutron spectra and on the fine structure of neutron fluxes in the cell of the I-4 core of the fast critical assembly at the Japan Atomic Energy Research Institute. The I-4 core is a graphite-diluted fast core with 3:1 volume ratio of 20% enriched metallic uranium and graphite. The nuclear emulsions

Shoji NOMOTO; Takehiko YASUNO; Hisashi NAKAMURA

1970-01-01

109

Characterization and quantification of an in-core neutron irradiation facility at a TRIGA II research reactor  

NASA Astrophysics Data System (ADS)

Experiments have been performed to characterize the neutron environment at an in-core TRIGA type nuclear research reactor. Steady-state thermal and epithermal neutron environment testing is important for many applications including, materials, electronics and biological cells. A well characterized neutron environment at a research reactor, including energy spectrum and spatial distribution, can be useful to many research communities and for educational research. This paper describes the characterization process and an application of exposing electronics to high neutron fluence.

Aghara, Sukesh; Charlton, William

2006-07-01

110

Nuclear data for Non-refueling core design  

Microsoft Academic Search

For design of innovative control system and safety characteristic of the Non-refueling core design of long life, a series of critical experiments is conducted at the fast critical facility, FCA of JAEA-Tokai. To quantitatively estimate the uncertainty reduction through critical experiments, an uncertainty reduction ratio (UR) is introduced, using the cross section error. Additionally with sensitivity analysis of the cross

Tetsuo MATSUMURA; Yasushi NAUCHI; Nobuyuki UEDA; Shigeaki OKAJIMA; Toshikazu TAKEDA

111

Hydraulic design and performance of a GCFR core assembly orifice  

Microsoft Academic Search

The design and performance of a core assembly orifice for gas-cooled fast-breeder reactors (GCFRs) are studied in this report. Successful reactor operation relies on adequate cooling, among other things, and orificing is important to cooling. A simple, yet effective, graphical design method for estimating the loss coefficient of an orifice and its associated opening area is presented. A numerical example

1980-01-01

112

The new cold neutron chopper spectrometer at the Spallation Neutron Source: Design and performance  

NASA Astrophysics Data System (ADS)

The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.

Ehlers, G.; Podlesnyak, A. A.; Niedziela, J. L.; Iverson, E. B.; Sokol, P. E.

2011-08-01

113

The new cold neutron chopper spectrometer at the Spallation Neutron Source: Design and performance  

SciTech Connect

The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.

Ehlers, G.; Podlesnyak, A. A.; Niedziela, J. L.; Iverson, E. B. [Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Sokol, P. E. [Department of Physics, Indiana University, Bloomington, Indiana 47405 (United States)

2011-08-15

114

The new cold neutron chopper spectrometer at the Spallation Neutron Source: design and performance.  

PubMed

The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments. PMID:21895276

Ehlers, G; Podlesnyak, A A; Niedziela, J L; Iverson, E B; Sokol, P E

2011-08-01

115

The new Cold Neutron Chopper Spectrometer at the Spallation Neutron Source -- Design and Performance  

SciTech Connect

The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.

Ehlers, Georg [ORNL; Podlesnyak, Andrey A [ORNL; Niedziela, Jennifer L [ORNL; Iverson, Erik B [ORNL; Sokol, Paul E [ORNL

2011-01-01

116

Maximum mass of neutron stars with quark matter core  

NASA Astrophysics Data System (ADS)

We propose a new strategy to construct the equation of state (EOS) for neutron stars (NSs) with hadron-quark (H-Q) phase transition, by considering three density-regions. We supplement the EOS at H-Q region, very uncertain due to the confinement-deconfinement problems, by sandwitching in between and matching to the relatively ``well known'' EOSs, i.e., the EOS at lower densities (H-phase up to several times nuclear density, calculated from a G-matrix approach) and that at ultra high densities (Q-phase, form a view of asymptotic freedom). Here, as a first step, we try a simple case and discuss the maximum mass of NSs.

Takatsuka, Tatsuyuki; Hatsuda, Tetsuo; Masuda, Kota

2012-11-01

117

A Tight Lattice, Epithermal Core Design for the Integral PWR  

SciTech Connect

An 8-year core design for an epithermal, water-cooled reactor has been developed based upon assessments of nuclear reactor physics, thermal-hydraulics and economics. An integral vessel configuration is adopted and self-supporting wire-wrap fuel is employed for the tight lattice of the epithermal core. A streaming path is incorporated in each assembly to ensure a negative void coefficient. A whole-core MCNP simulation of the tight core shows a negative void coefficient for any burnup with positive K{sub EFF}. The VIPRE{sup TM} code has been used to calculate the critical heat flux (CHF) by means of an appropriate wire-wrap CHF correlation, specifically introduced in the source code. Economically, the high fuel enrichment (14% w/o {sup 235}U) and the very long core life (8 ys) lead to high lifetime-levelized unit fuel cycle cost (in mills/kWhre). However, both operation and maintenance and capital-related expenditures strongly benefited from the higher electric output per unit volume, which yielded quite small lifetime-levelized unit capital and operation and maintenance costs for the overall plant. Financing costs are included and an estimate is provided for the total lifetime-levelized unit cost of the epithermal core, which is about 20% lower than that of a more open lattice thermal spectrum core fitting into the same core envelope and with 4-year lifetime. (authors)

Saccheri, J.G.B. [Brookhaven National Laboratory, Nuclear Science and Technology Division Bldg 475, Upton, New York 11973-5000 (United States); Todreas, N.E.; Driscoll, M.J. [Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Bldg. 24-205 MA 02139-4307 (United States)

2004-07-01

118

Giant and supergiant stars with degenerate neutron cores  

NASA Astrophysics Data System (ADS)

Two classes of Thorne-Zytkow (TZ) stellar models are investigated: the giant models with low-mass envelopes and gravitational energy generation, and the super giant ones with more massive envelopes and nuclear energy generation. Bisnovatyi-Kogan and Lamzin (1984) argue that there is a flaw in the TZ match of the giant star's envelope onto their cores, that no equilibrium giant models will be possible when this flaw is corrected, and that such giant stars will turn out to die quickly via runaway neutrino losses and catastrophic contraction. The paper shows that Bisnovatyi-Kogan and Lamzin are mistaken: there is no flaw in the match to the core; fully self-consistent equilibrium models do exist; and the structure of those models suggests that they will be stable against neutrino-loss-triggered contraction. By contrast, there are genuine difficulties with the TZ supergiant models because their hot CNO cycle nuclear reactions get hung up waiting for beta-decays and thus have difficulty generating enough energy for hydrostatic support. An unsuccessful attempt to build self-consistent supergiant models based on a nonequilibrium hot CNO cycle is described.

Eich, Chris; Zimmermann, Mark E.; Thorne, Kip S.; Zytkow, Anna N.

1989-11-01

119

Design assumptions and bases for small D-T-fueled spherical tokamak (ST) fusion core  

SciTech Connect

Recent progress in defining the assumptions and clarifying the bases for a small D-T-fueled ST fusion core are presented. The paper covers several issues in the physics of ST plasmas, the technology of neutral beam injection, the engineering design configuration, and the center leg material under intense neutron irradiation. This progress was driven by the exciting data from pioneering ST experiments, a heightened interest in proof-of-principle experiments at the MA level in plasma current, and the initiation of the first conceptual design study of the small ST fusion core. The needs recently identified for a restructured fusion energy sciences program have provided a timely impetus for examining the subject of this paper. Our results, though preliminary in nature, strengthen the case for the potential realism and attractiveness of the ST approach. 51 refs., 6 figs., 3 tabs.

Peng, Y.K.M. [Oak Ridge National Lab., TN (United States); Cheng, E.T.; Cerbone, R.J. [TSI Research, Inc., Solana Beach, CA (United States)] [and others

1996-12-31

120

Design assumptions and bases for small D-T-fueled spherical tokamak (ST) fusion core  

SciTech Connect

Recent progress in defining the assumptions and clarifying the bases for a small D-T-fueled ST fusion core are presented. The paper covers several issues in the physics of ST plasmas, the technology of neutral beam injection, the engineering design configuration, and the center leg material under intense neutron irradiation. This progress was driven by the exciting data from pioneering ST experiments, a heightened interest in proof-of-principle experiments at the MA level in plasma current, and the initiation of the first conceptual design study of the small ST fusion core. The needs recently identified for a restructured fusion energy sciences program have provided a timely impetus for examining the subject of this paper. Our results, though preliminary in nature, strengthen the case for the potential realism and attractiveness of the ST approach.

Peng, Yueng Kay Martin [ORNL; Haines, J.R. [Oak Ridge National Laboratory (ORNL)

1996-01-01

121

Transport properties of a quark-hadron Coulomb lattice in the cores of neutron stars  

NASA Astrophysics Data System (ADS)

Already more that 40 years ago, it has been suggested that because of the enormous mass densities in the cores of neutron stars, the hadrons in the centers of neutron stars may undergo a phase transition to deconfined quark matter. In this picture, neutron stars could contain cores made of pure (up, down, strange) quark matter which are surrounded by a mixed phase of quarks and hadrons. More than that, because of the competition between the Coulomb and the surface energies associated with the positively charged regions of nuclear matter and negatively charged regions of quark matter, the mixed phase may develop geometrical structures similarly to what is expected of the subnuclear liquid-gas phase transition. In this paper we restrict ourselves to considering the formation of rare phase blobs in the mixed quark-hadron phase. The influence of rare phase blobs on the thermal and transport properties of neutron star matter is investigated. The total specific heat cV, thermal conductivity ?, and electron-blob bremsstrahlung neutrino emissivities ??,BR, of quark-hybrid matter are computed, and the results are compared with the associated thermal and transport properties of standard neutron star matter. Our results show that the contribution of rare phase blobs to the specific heat is negligibly small. This is different for the neutrino emissivity from electron-blob bremsstrahlung scattering, which turns out to be of the same order of magnitude as the total contributions from other bremsstrahlung processes for temperatures below about 108K.

Na, Xuesen; Xu, Renxin; Weber, Fridolin; Negreiros, Rodrigo

2012-12-01

122

Resistance to torsional forces of various post and core designs.  

PubMed

This in vitro study investigated the resistance of various post and core designs to torsional forces. Cast gold, parallel-sided, serrated post and cores were cemented in extracted teeth. The test groups were made up of the following designs: controls without an antirotational feature, keyway form, coronal flare form, auxiliary pin form, a cervical collar form, and included a tapered post group. The specimens were mounted on an Instron Universal testing machine and a torsional force was applied to the core using a lever arm until failure. All the antirotational features tested elevated resistance to torque. Failure occurred through fracture of the tooth, the cement, or an optional auxiliary pin. The cervical collar was the most favorable design, embracing resistance and reducing tooth fractures. PMID:1800728

Hemmings, K W; King, P A; Setchell, D J

1991-09-01

123

Comparative safety assessment of upflow versus downflow GCFR core designs  

SciTech Connect

This report presents a hypothetical core disruptive accident safety assessment and a post-accident fuel containment evaluation which were performed for the upflow versus downflow core design decision for the GCFR. Differences between the upflow and downflow unprotected accident sequences were not significant. However, differences do appear when potential accident mitigation and recriticality prevention design concepts are investigated for the loss of shutdown cooling and flow blockage accidents. An in-vessel molten fuel containment system is preferred over an ex-vessel system for both the upflow and downflow concepts.

Frank, M.V.; Kang, C.S.; Reilly, J.T.; Wheeler, P.A.

1980-09-01

124

EU Blanket Design Activities and Neutronics Support Efforts  

SciTech Connect

An overview is provided of the design activities and the related neutronics support efforts conducted in the European Union for the development of breeder blankets for future fusion power reactors. The EU fusion programme considers two blanket lines, the Helium-Cooled Pebble Bed (HCPB) blanket with Lithium ceramics pebbles (Li{sub 4}SiO{sub 4} or Li{sub 2}TiO{sub 3}) as breeder and beryllium pebbles as neutron multiplier, and the Helium-Cooled Lithium-Lead (HCLL) blanket with the Pb-Li eutectic alloy as breeder and neutron multiplier. The blanket design and the related R and D efforts are based on the use of the same coolant and the same modular blanket structure to minimise the development costs as much as possible. The neutronic support efforts include design analyses for the layout and optimization of the modular HCPB/HCLL blankets based on detailed three-dimensional Monte Carlo calculations as well as underlying neutronics activities conducted in the frame of the European Fusion and Activation File (EFF/EAF) projects to develop qualified nuclear data and computational tools for reliable neutronics design calculations.

Fischer, U. [Forschungszentrum Karlsruhe (Germany); Batistoni, P. [ENEA Fusion Division (Italy); Boccaccini, L.V. [Forschungszentrum Karlsruhe (Germany); Giancarli, L. [CEA Saclay (France); Hermsmeyer, S. [Forschungszentrum Karlsruhe (Germany); Poitevin, Y. [CEA Saclay (France)

2005-05-15

125

China Spallation Neutron Source: Design, R&D, and outlook  

NASA Astrophysics Data System (ADS)

The China Spallation Neutron Source (CSNS) is an accelerator based multidiscipline user facility planned to be constructed in Dongguan, Guangdong, China. The CSNS complex consists of an negative hydrogen linear accelerator, a rapid cycling proton synchrotron accelerating the beam to 1.6 GeV energy, a solid tungsten target station, and instruments for spallation neutron applications. The facility operates at 25 Hz repetition rate with an initial design beam power of 120 kW and is upgradeable to 500 kW. The primary challenge is to build a robust and reliable user's facility with upgrade potential at a fraction of “world standard” cost. We report the status, design, R&D, and upgrade outlook including applications using spallation neutron, muon, fast neutron, and proton, as well as related programs including medical therapy and accelerator-driven sub-critical reactor (ADS) programs for nuclear waste transmutation.

Wei, Jie; Chen, Hesheng; Chen, Yanwei; Chen, Yuanbo; Chi, Yunlong; Deng, Changdong; Dong, Haiyi; Dong, Lan; Fang, Shouxian; Feng, Ji; Fu, Shinian; He, Lunhua; He, Wei; Heng, Yuekun; Huang, Kaixi; Jia, Xuejun; Kang, Wen; Kong, Xiangcheng; Li, Jian; Liang, Tianjiao; Lin, Guoping; Liu, Zhenan; Ouyang, Huafu; Qin, Qing; Qu, Huamin; Shi, Caitu; Sun, Hong; Tang, Jingyu; Tao, Juzhou; Wang, Chunhong; Wang, Fangwei; Wang, Dingsheng; Wang, Qingbin; Wang, Sheng; Wei, Tao; Xi, Jiwei; Xu, Taoguang; Xu, Zhongxiong; Yin, Wen; Yin, Xuejun; Zhang, Jing; Zhang, Zong; Zhang, Zonghua; Zhou, Min; Zhu, Tao

2009-02-01

126

Water-level measurements using ex-core neutron detectors at Farley Unit One. Final report  

SciTech Connect

This report documents the theory, tests, results, and analyses of water level measurement tests performed at the Farley Unit One nuclear power plant in November 1980. Measurements were made during a normal plant outage using an ex-core neutron detector system placed on top of the reactor vessel head. The data indicate that this system was able to indicate when the water level in the vessel approached to within approximately four feet of the top of the reactor core. Two-dimensional computer calculations simulating the experiment agree well with trends and results of the measured data.

Untermyer, S.; Hagan, W.K.; Jones, J.E.

1982-04-01

127

Micro-pocket fission detectors (MPFD) for in-core neutron flux monitoring  

NASA Astrophysics Data System (ADS)

Micro-pocket fission detectors (MPFD) have been fabricated and tested as in-core flux monitors in the 250 kW TRIGA nuclear reactor at Kansas State University. The prototype devices have been coated with a natural uranyl-nitrate to provide a neutron reactive coating. The devices are composed of alumina substrates sealed together to form a miniature gas pocket 3 mm in diameter and 1 mm wide. The devices are radiation hard and can operate in pulse mode in a neutron flux exceeding 1012 cm-2 s-1. Placed in the central thimble of the reactor core, the MPFDs have shown count rate linearity from low to high power. Dead time losses become apparent at power levels exceeding 100 kW, yet are still low enough to allow for pulse mode operation.

McGregor, Douglas S.; Ohmes, Martin F.; Ortiz, Rylan E.; Sabbir Ahmed, A. S. M.; Kenneth Shultis, J.

2005-12-01

128

Design of a new CCD-camera neutron radiography detector  

Microsoft Academic Search

A new electronic neutron radiography detector has been designed at the Paul Scherrer Institute with the aim of providing a tool for scientific and industrial radiography applications requiring high-quantitative precision.The basic principle of the detector is the combination of a CCD-camera with a neutron-sensitive scintillator screen. The light from the screen is reflected to the camera by a mirror and

Helena Pleinert; Eberhard Lehmann; Sonja Körner

1997-01-01

129

Advanced neutronics tools for BWR design calculations  

Microsoft Academic Search

This paper summarizes the developments implemented in the new APOLLO2.8 neutronics tool to meet the required target accuracy in LWR applications, particularly void effects and pin-by-pin power map in BWRs. The Method of Characteristics was developed to allow efficient LWR assembly calculations in 2D-exact heterogeneous geometry; resonant reaction calculation was improved by the optimized SHEM-281 group mesh, which avoids resonance

A. Santamarina; N. Hfaiedh; R. Letellier; V. Marotte; S. Misu; A. Sargeni; C. Vaglio; I. Zmijarevic

2008-01-01

130

Advanced Neutronics Tools for BWR Design Calculations  

Microsoft Academic Search

This paper summarizes the developments implemented in the new APOLLO2.8 neutronics tool to meet the required target accuracy in LWR applications, particularly void effects and pin-by-pin power map in BWRs. The Method Of Characteristics was developed to allow efficient LWR assembly calculations in 2D-exact heterogeneous geometry; resonant reaction calculation was improved by the optimized SHEM-281 group mesh, which avoids resonance

A. Santamarina; N. Hfaiedh; R. Letellier; A. Sargeni; C. Vaglio; V. Marotte; S. Misu; I. Zmijarevic

2006-01-01

131

The Interplay between Proto--Neutron Star Convection and Neutrino Transport in Core-Collapse Supernovae  

Microsoft Academic Search

We couple two-dimensional hydrodynamics to realistic one-dimensional multigroup flux-limited diffusion neutrino transport to investigate proto-neutron star convection in core-collapse supernovae, and more specifically, the interplay between its development and neutrino transport. Our initial conditions, time-dependent boundary conditions, and neutrino distributions for computing neutrino heating, cooling, and deleptonization rates are obtained from one-dimensional simulations that implement multigroup flux-limited diffusion and one-dimensional

A. Mezzacappa; A. C. Calder; S. W. Bruenn; J. M. Blondin; M. W. Guidry; M. R. Strayer; A. S. Umar

1998-01-01

132

Design of a Moderated Multidetector Neutron Spectrometer for Optimal Specificity  

SciTech Connect

Neutron spectrometry can play an important role in the detection and identification of neutron-emitting sources in various security applications. In the present work, a portable filtered array neutron spectrometer, consisting of twelve 6LiF-based thermal neutron detectors embedded within a single heterogeneous volume was designed and its expected performance compared to that of a commercially available 12-sphere Bonner spheres spectrometer. Each detector within the volume was designed to optimally respond to a unique portion of the neutron spectrum by varying the type and thickness of materials used to filter the spectrum as well as the thickness of the moderator in front of the detector. The available design space was permuted and performance metrics developed to identify the optimal geometries. The top performing detector geometries were then combinatorially explored to identify the best array of geometries that yielded the most information about a neutron spectrum. The best performing filtered array was found to provide as much spectral information as, or more than, the commercially available 12-sphere Bonner spheres spectrometer to which it was compared.

Harrison, Mark J [ORNL; Cherel, Quentin [University of Florida, Gainesville; Monterial, Mateusz [ORNL

2011-01-01

133

Active Neutron Veto Shield Design for SuperCDMS-SNOLAB  

NASA Astrophysics Data System (ADS)

Protection against neutron backgrounds is one of the key issues for the next generation SuperCDMS direct dark matter detection experiment that aims at exploring the 10-46 cm^2 cross section region for spin-independent interactions of Weakly Interacting Massive Particles (WIMPs) with nucleons. Estimation of the background from radioactive processes is a crucial task for the current experiment stage and for designing future large-scale detectors. An active neutron veto would make the next generation of dark matter experiment more robust, improving the credibility of a dark matter detection claim based on the observation of a few recoil events. SuperCDMS is investigating the feasibility of adding a liquid scintillator active neutron veto, loaded with high neutron capture cross section isotopes, to the SuperCDMS SNOLAB shield design. This system not only will allow us to reject neutron-induced backgrounds, but also will provide an in-situ measurement of the neutron flux near the detector. I will report the status of ongoing studies related to the design and construction of such a veto.

Qiu, Hang

2013-04-01

134

Two stochastic optimization algorithms applied to nuclear reactor core design  

Microsoft Academic Search

Two stochastic optimization algorithms conceptually similar to Simulated Annealing are presented and applied to a core design optimization problem previously solved with Genetic Algorithms. The two algorithms are the novel Particle Collision Algorithm (PCA), which is introduced in detail, and Dueck's Great Deluge Algorithm (GDA). The optimization problem consists in adjusting several reactor cell parameters, such as dimensions, enrichment and

Wagner F. Sacco; Cassiano R. E. de oliveira; Cláudio M. N. A. Pereira

2006-01-01

135

Design Studies on Iron-Core Synchronously Operating Linear Motors.  

National Technical Information Service (NTIS)

This report concerns the design of iron-core synchronously-operating linear motors with passive rail track. Claw-pole and homopolar inductor motors were the 2 basic types considered. The principal conclusions were the homopolar inductor motor is the prefe...

E. Levi

1981-01-01

136

Hydraulic Design and Performance of a GCFR Core Assembly Orifice.  

National Technical Information Service (NTIS)

The design and performance of a core assembly orifice for gas-cooled fast-breeder reactors (GCFRs) are studied in this report. Successful reactor operation relies on adequate cooling, among other things, and orificing is important to cooling. A simple, ye...

I. M. Tang

1980-01-01

137

Calculation of Design Parameters for an Equilibrium LEU Core in the NBSR  

SciTech Connect

A plan is being developed for the conversion of the NIST research reactor (NBSR) from high-enriched uranium (HEU) fuel to low-enriched uranium (LEU) fuel. Previously, the design of the LEU fuel had been determined in order to provide the users of the NBSR with the same cycle length as exists for the current HEU fueled reactor. The fuel composition at different points within an equilibrium fuel cycle had also been determined. In the present study, neutronics parameters have been calculated for these times in the fuel cycle for both the existing HEU and the proposed LEU equilibrium cores. The results showed differences between the HEU and LEU cores that would not lead to any significant changes in the safety analysis for the converted core. In general the changes were reasonable except that the figure-of-merit for neutrons that can be used by experimentalists shows there will be a 10% reduction in performance. The calculations included kinetics parameters, reactivity coefficients, reactivity worths of control elements and abnormal configurations, and power distributions.

Hanson, A.L.; Diamond, D.

2011-09-30

138

A practical neutron shielding design based on data-base interpolation  

Microsoft Academic Search

Neutron shielding design is an important part of the construction of nuclear reactors and high-energy accelerators. Neutron shielding design is also indispensable in the packaging and storage of isotopic neutron sources. Most efforts in the development of neutron shielding design have been concentrated on nuclear reactor shielding because of its huge mass and strict requirement of accuracy. Sophisticated computational tools,

S. H. Jiang; R. J. Sheu

1993-01-01

139

Study of the neutron beam line shield design for JSNS.  

PubMed

The JSNS, a spallation neutron source of J-PARC (JAERI-KEK Joint Project of the High Intensity Proton Accelerator) has 23 neutron beam lines. In the present study, a database was formulated for an optimum shielding design using the MCNP-X code. The calculations involved two steps. In the first step, the neutron distributions were created in the typical neutron beam line with a model that included the spallation neutron source target. The neutron currents evaluated flowed from the duct into the duct wall which was the boundary source for the bulk shield surrounding the beam line. In the second step, bulk-shield calculations were performed for the various shielding materials (iron, concrete, heavy concrete and so on) used and their composites up to thicknesses of 3 m. The results were compared with each other. Composite material shields of iron and such hydrogeneous materials as polyethylene or concrete were more effective. A typical design was prepared for a beam line within 25 m distance from a moderator, as a sample. PMID:16381789

Kawai, M; Saito, K; Sanami, T; Nakao, N; Maekawa, F

2005-01-01

140

Neutron Tube Design Study for Boron Neutron Capture TherapyApplication  

SciTech Connect

Radio-frequency (RF) driven ion sources are being developed in Lawrence Berkeley National Laboratory (LBNL) for sealed-accelerator-tube neutron generator application. By using a 5-cm-diameter RF-driven multicusp source H{sup +} yields over 95% have been achieved. These experimental findings will enable one to develop compact neutron generators based on the D-D or D-T fusion reactions. In this new neutron generator, the ion source, the accelerator and the target are all housed in a sealed metal container without external pumping. Recent moderator design simulation studies have shown that 14 MeV neutrons could be moderated to therapeutically useful energy ranges for boron neutron capture therapy (BNCT). The dose near the center of the brain with optimized moderators is about 65% higher than the dose obtained from a typical neutron spectrum produced by the Brookhaven Medical Research Reactor (BMRR), and is comparable to the dose obtained by other accelerator-based neutron sources. With a 120 keV and 1 A deuteron beam, a treatment time of {approx}35 minutes is estimated for BNCT.

Verbeke, J.M.; Lee, Y.; Leung, K.N.; Vujic, J.; Williams, M.D.; Wu, L.K.; Zahir, N.

1998-01-04

141

Advanced Neutronics Tools for BWR Design Calculations  

SciTech Connect

This paper summarizes the developments implemented in the new APOLLO2.8 neutronics tool to meet the required target accuracy in LWR applications, particularly void effects and pin-by-pin power map in BWRs. The Method Of Characteristics was developed to allow efficient LWR assembly calculations in 2D-exact heterogeneous geometry; resonant reaction calculation was improved by the optimized SHEM-281 group mesh, which avoids resonance self-shielding approximation below 23 eV, and the new space-dependent method for resonant mixture that accounts for resonance overlapping. Furthermore, a new library CEA2005, processed from JEFF3.1 evaluations involving feedback from Critical Experiments and LWR P.I.E, is used. The specific '2005-2007 BWR Plan' settled to demonstrate the validation/qualification of this neutronics tool is described. Some results from the validation process are presented: the comparison of APOLLO2.8 results to reference Monte Carlo TRIPOLI4 results on specific BWR benchmarks emphasizes the ability of the deterministic tool to calculate BWR assembly multiplication factor within 200 pcm accuracy for void fraction varying from 0 to 100%. The qualification process against the BASALA mock-up experiment stresses APOLLO2.8/CEA2005 performances: pin-by-pin power is always predicted within 2% accuracy, reactivity worth of B4C or Hf cruciform control blade, as well as Gd pins, is predicted within 1.2% accuracy. (authors)

Santamarina, A.; Hfaiedh, N.; Letellier, R.; Sargeni, A.; Vaglio, C. [CEA-Cadarache, 13108 St Paul lez Durance Cedex (France); Marotte, V. [AREVA NP SAS (France); Misu, S. [AREVA NP GmbH (Germany); Zmijarevic, I. [CEA-Saclay, 91191 Gif-sur-Yvette Cedex (France)

2006-07-01

142

Neutronic design studies for the MIT fission converter beam  

SciTech Connect

Currently available epithermal neutron beams at the Massachusetts Institute of Technology (MIT) are not sufficiently intense to meet the anticipated demand for boron neutron capture therapy (BNCT) treatments if initial, currently in progress clinical trials of BNCT prove successful. Indeed, they are not really adequate for extensive (phase-III) clinical trials. To fulfill this need, a high-intensity, high-quality fission converter-based epithermal neutron beam for BNCT has been designed for the MIT Research Reactor, (MITR-II). This epithermal neutron beam, capable of delivering treatments in a few minutes with negligible beam background contamination, would be installed in the present thermal column and hohlraum of the MITR-II.

Kiger, W.S. III; Harling, O.K. [Massachusetts Inst. of Technology, Cambridge, MA (United States)

1996-12-31

143

Design of radial neutron spectrometer array for the International Thermonuclear Experimental Reactor  

Microsoft Academic Search

We designed the radial neutron spectrometer using a new type DT neutron spectrometer base on a recoil proton counter-telescope technique aiming ion temperature measurement for the International Thermonuclear Experimental Reactor (ITER). The neutron spectrometer will be installed on the well collimated neutron beam line. A large area recoil proton emitter is placed parallel to the incident neutron beam and microchannel

T. Nishitani; S. Kasai; T. Iguchi; E. Takada; K. Ebisawa; Y. Kita

1997-01-01

144

Design and analysis of PCRV core cavity closure  

SciTech Connect

Design requirements and considerations for a core cavity closure which led to the choice of a concrete closure with a toggle hold-down as the design for the Gas-Cooled Fast Breeder Reactor (GCFR) plant are discussed. A procedure for preliminary stress analysis of the closure by means of a three-dimensional finite element method is described. A limited parametric study using this procedure indicates the adequacy of the present closure design and the significance of radial compression developed as a result of inclined support reaction.

Lee, T.T.; Schwartz, A.A.; Koopman, D.C.A.

1980-05-01

145

Neutronics analyses in support of the conceptual design of the MAPS NTP reactor  

SciTech Connect

Within the framework of the French nuclear thermal propulsion program called MAPS (Lenain 1996), several neutronics studies and analyses were performed. The aim was to determine the basic design features of a reactor based on the Pebble Bed Reactor concept (Powell 1985) and needing minimum technological developments. In the concern to further enhance the reactor safety posture and to maintain a minimum engine mass breakdown, a beryllium moderated/reflected reactor using highly enriched UO{sub 2} or UC{sub 2} as fuel has been designed with a mean hydrogen core outlet temperature of 2200 K (theoretical ISP of 859 s). The objective of this paper is to give a detailed neutronics analysis of the MAPS reactor. {copyright} {ital 1996 American Institute of Physics.}

Raepsaet, X.; Lenain, R. [Commissariat a l`Energie Atomique, DRN/DMT CEN Saclay, F-91191 Gif-sur-Yvette Cedex (France); Naury, S. [Altran Technologies, 58 Boulvard Gouvion Saint Cyr, 75858 PARIS Cedex 17 (France)

1996-03-01

146

Neutron core excitations in the N=126 nuclide {sup 210}Po  

SciTech Connect

Excited states above the 16{sup +} isomer in {sup 210}Po have been identified using time-correlated {gamma}-ray spectroscopy techniques and the {sup 204}Hg({sup 13}C,3n{alpha}){sup 210}Po reaction. States up to {approx}27({Dirac_h}/2{pi}) have been identified, including an isomer at 8074 keV with a mean life of 13(2) ns. Among the new states, a candidate for the 17{sup +} state obtained from maximal coupling of the {pi}[h{sub 9/2}i{sub 13/2}]{sub 11{sup -}} valence proton configuration and the {nu}[p{sub 1/2}{sup -1}i{sub 11/2}]{sub 6{sup -}} neutron core excitation has been identified. This and other results are compared with semiempirical shell-model calculations that predict that single core excitations from the i{sub 13/2} neutron orbital and double core excitations out of the p{sub 1/2} and f{sub 5/2} orbitals, populating the g{sub 9/2},i{sub 11/2}, and j{sub 15/2} orbitals above the N=126 shell, will compete in energy. Good agreement is obtained for the lower states but there are systematic discrepancies at high spins including the absence of states that are calculated to lie low in the spectrum, implying uncertainties for configurations associated either with the i{sub 13/2} neutron hole or double core excitations.

Dracoulis, G. D.; Lane, G. J.; Davidson, P. M.; Kibedi, T.; Nieminen, P.; Maier, K. H.; Watanabe, H. [Department of Nuclear Physics, R. S. Phys. S. E., Australian National University, Canberra ACT 0200 (Australia); Byrne, A. P.; Wilson, A. N. [Department of Nuclear Physics, R. S. Phys. S. E., Australian National University, Canberra ACT 0200 (Australia); Department of Physics, The Faculties, Australian National University, Canberra ACT 0200 (Australia)

2008-03-15

147

Phenix Power Plant Decommissioning Project - Removal of Core and Neutron Blanket Components  

SciTech Connect

Phenix is a sodium-cooled fast neutron reactor located at the CEA's Rhone Valley Center where it was commissioned in 1974. It has an electric power rating of 250 MW and is operated jointly by the CEA and EDF. Its primary role today is to investigate the transmutation of long-lived radioactive waste into shorter-lived wasteform. Its final shutdown is scheduled for the beginning of 2009 in accordance with the reactor operating program with a mean availability of 80%. In this context the Phenix Power Plant Decommissioning Project was initiated in 2003. It covers the definitive cessation of plant operation and the dismantling (D and D) operations together with the final shutdown preparatory phase. The final shutdown phase corresponds to the initial operations undertaken to remove the maximum of hazardous materials. During this phase, subject to the standard operating methodological procedures, all the fuel in the plant will be removed and most of the other reactor core elements and other removable components (primary pumps, intermediate heat exchangers, control rod mechanisms, etc.) will be also dismantled and packaged in accordance with the available disposition routes. The core elements include fissile and fertile subassemblies, steel reflectors, and lateral neutron shielding rods. About half the lateral neutron shielding rods are accessible using the existing handling equipment; specific development work will be necessary to remove the others. Multiple engineering studies are in progress concerning the removal of the core elements. They address safety concerns taking into account thermal and seismic stresses, waste management including radiological characterization of the objects to be removed and the specification of suitable disposal routes (interim storage or disposal facilities), and scenario studies with the definition of each stage of the waste removal process. All these aspects are discussed in this paper. The feasibility of removing the core elements has been demonstrated with regard to handling and safety. A new handling arm is now being developed to remove the inaccessible core elements. The new earthquake safety calculations completed in 2006 did not reveal any insurmountable difficulties. Major work remains to characterize the core elements and determine the capacity of the disposition routes. The characterization program now in progress will validate the core element activation levels, but must be supplemented by a program to characterize the surface contamination from the primary sodium system. Concerning the disposition routes, several specific containers and shipping casks must be developed; engineering studies are now in progress to obtain the necessary approvals.

Moitrier, C. [CEA /Marcoule DDCO/SDSP BP 17171 302078 Bagnols Sur Ceze (France)

2008-01-15

148

New casing and backfill design for neutron logging access boreholes  

SciTech Connect

In an effort to enhance the usefulness of neutron logging for environmental applications, a new combination of backfill and casing materials for access boreholes has been developed. The combination of acrylic casing and polyurethane foam backfill has been tested under laboratory and field conditions. Acrylic casing does not significantly attenuate fluxes of either high energy or thermal neutrons, in contrast with polyvinyl chloride casing which reduces the thermal neutron flux by more than 40% due to neutron absorption by chlorine. Polyurethane foam, which is inert, hydrophobic, and insoluble in water, adheres well to both dry and wetted soils, sediments, and rocks. It can be formed in situ at a low, but controllable, bulk density. At a bulk density of 0.08 g cm{sup {minus}3}, and in combination with acrylic casing, polyurethane foam increases the thermal neutron count by less than 5% in a saturated sand, relative to background. In addition to its small effect on the neutron flux, polyurethane foam, unlike bentonite or cement, does not affect the moisture content of the surrounding formation during installation. Furthermore, because it is a closed-cell foam, its moisture content does not change under varying formation moisture conditions. As was shown in related field tests, polyurethane foam is especially well suited for backfilling boreholes in fractured rocks because of its fast set time which minimizes penetration into fractures. The design proved to be convenient and durable under rugged field conditions.

Zawislanski, P.T.; Faybishenko, B. [Lawrence Berkeley National Lab., CA (United States). Earth Sciences Div.

1999-01-01

149

New casing and backfill design for neutron logging access boreholes  

SciTech Connect

In an effort to enhance the usefulness of neutron logging for environmental applications, a new combination of backfill and casing materials for access boreholes has been developed. The combination of acrylic casing and polyurethane foam backfill has been tested under laboratory and field conditions. Acrylic casing does not significantly attenuate fluxes of either high energy or thermal neutrons, in contrast with polyvinyl chloride casing which reduces the thermal neutron flux by more than 40 percent due to neutron absorption by chlorine, Polyurethane foam, which is inert, hydrophobic, and insoluble in water, adheres well to both dry and wetted soils, sediments, and rocks. It can be formed in situ at a low but controllable, bulk density. At a bulk density of 0.08 g cm(-3), and in combination with acrylic casing, polyurethane foam increases the thermal neutron count by less than 5 percent in a saturated sand, relative to background. In addition to its small effect on the neutron flux, polyurethane foam, unlike bentonite or cement, does not affect the moisture content of the surrounding formation during installation. Furthermore, because it is a closed-cell foam, its moisture content does not change under varying formation moisture conditions. As was shown in related field tests, polyurethane foam is especially well suited for backfilling boreholes in fractured rocks because of its fast set time which minimizes penetration into fractures. The design proved to be convenient and durable under rugged field conditions.

Zawislanski, Peter T.; Faybishenko, Boris

1998-12-01

150

ORR core re-configuration measurements to increase the fast neutron flux in the Magnetic Fusion Energy (MFE) experiments  

Microsoft Academic Search

The relative increases obtainable in the fast neutron flux in the Magnetic Fusion Energy (MFE) experiment positions were studied by reconfiguring the current ORR core. The percentage increase possible in the current displacement per atom (dpa) rate was examined. The principle methods to increase the fast flux, consisted of reducing the current core size (number of fuel elements), to increase

R. W. Hobbs; R. M. Stinnett; T. M. Sims

1985-01-01

151

A shielding design for an accelerator-based neutron source for boron neutron capture therapy.  

PubMed

Research in boron neutron capture therapy (BNCT) at The Ohio State University Nuclear Engineering Department has been primarily focused on delivering a high quality neutron field for use in BNCT using an accelerator-based neutron source (ABNS). An ABNS for BNCT is composed of a proton accelerator, a high-energy beam transport system, a (7)Li target, a target heat removal system (HRS), a moderator assembly, and a treatment room. The intent of this paper is to demonstrate the advantages of a shielded moderator assembly design, in terms of material requirements necessary to adequately protect radiation personnel located outside a treatment room for BNCT, over an unshielded moderator assembly design. PMID:15308187

Hawk, A E; Blue, T E; Woollard, J E

2004-11-01

152

Design of a boron neutron capture enhanced fast neutron therapy assembly  

SciTech Connect

The use of boron neutron capture to boost tumor dose in fast neutron therapy has been investigated at several fast neutron therapy centers worldwide. This treatment is termed boron neutron capture enhanced fast neutron therapy (BNCEFNT). It is a combination of boron neutron capture therapy (BNCT) and fast neutron therapy (FNT). It is believed that BNCEFNT may be useful in the treatment of some radioresistant brain tumors, such as glioblastoma multiform (GBM). A boron neutron capture enhanced fast neutron therapy assembly has been designed for the Fermilab Neutron Therapy Facility (NTF). This assembly uses a tungsten filter and collimator near the patient's head, with a graphite reflector surrounding the head to significantly increase the dose due to boron neutron capture reactions. The assembly was designed using Monte Carlo radiation transport code MCNP version 5 for a standard 20x20 cm{sup 2} treatment beam. The calculated boron dose enhancement at 5.7-cm depth in a water-filled head phantom in the assembly with a 5x5 cm{sup 2} collimation was 21.9% per 100-ppm {sup 10}B for a 5.0-cm tungsten filter and 29.8% for a 8.5-cm tungsten filter. The corresponding dose rate for the 5.0-cm and 8.5-cm thick filters were 0.221 and 0.127 Gy/min, respectively; about 48.5% and 27.9% of the dose rate of the standard 10x10 cm{sup 2} fast neutron treatment beam. To validate the design calculations, a simplified BNCEFNT assembly was built using four lead bricks to form a 5x5 cm{sup 2} collimator. Five 1.0-cm thick 20x20 cm{sup 2} tungsten plates were used to obtain different filter thicknesses and graphite bricks/blocks were used to form a reflector. Measurements of the dose enhancement of the simplified assembly in a water-filled head phantom were performed using a pair of tissue-equivalent ion chambers. One of the ion chambers is loaded with 1000-ppm natural boron (184-ppm {sup 10}B) to measure dose due to boron neutron capture. The measured dose enhancement at 5.0-cm depth in the head phantom for the 5.0-cm thick tungsten filter is (16.6 {+-} 1.8)%, which agrees well with the MCNP simulation of the simplified BNCEFNT assembly, (16.4 {+-} 0.5)%. The error in the calculated dose enhancement only considers the statistical uncertainties. The total dose rate measured at 5.0-cm depth using the non-borated ion chamber is (0.765 {+-} 0.076) Gy/MU, about 61% of the fast neutron standard dose rate (1.255Gy/MU) at 5.0-cm depth for the standard 10x10 cm{sup 2} treatment beam. The increased doses to other organs due to the use of the BNCEFNT assembly were calculated using MCNP5 and a MIRD phantom. The activities of the activation products produced in the BNCEFNT assembly after neutron beam delivery were computed. The photon ambient dose rate due to the radioactive activation products was also estimated.

Wang, Zhonglu; /Georgia Tech

2006-08-01

153

Expansion of the 16O-core in neutron drip-line nuclei: 23O and 24O  

NASA Astrophysics Data System (ADS)

We study an effect of the expansion of the core nucleus to the radius of 23O and 24O. In order to clarify the importance of the expansion of the core, we perform two calculations; an m-scheme approach of the cluster-orbital shell model for O16+Xn systems and a simplified model approach for core+n and core+2n systems. We calculate the energy and r.m.s. radius of oxygen isotopes by using these two approaches and discuss the effect of the expansion of the 16O-core and the relation to the presence of valence neutrons. Furthermore, we propose a new approach of a coupled-channel model including a particle-hole excitation in the 16O-core and the motion of the valence neutron.

Masui, H.; Kat?, K.; Ikeda, K.

2012-12-01

154

High Flux Isotope Reactor cold neutron source reference design concept  

SciTech Connect

In February 1995, Oak Ridge National Laboratory`s (ORNL`s) deputy director formed a group to examine the need for upgrades to the High Flux Isotope Reactor (HFIR) system in light of the cancellation of the Advanced neutron Source Project. One of the major findings of this study was that there was an immediate need for the installation of a cold neutron source facility in the HFIR complex. In May 1995, a team was formed to examine the feasibility of retrofitting a liquid hydrogen (LH{sub 2}) cold source facility into an existing HFIR beam tube. The results of this feasibility study indicated that the most practical location for such a cold source was the HB-4 beam tube. This location provides a potential flux environment higher than the Institut Laue-Langevin (ILL) vertical cold source and maximizes the space available for a future cold neutron guide hall expansion. It was determined that this cold neutron beam would be comparable, in cold neutron brightness, to the best facilities in the world, and a decision was made to complete a preconceptual design study with the intention of proceeding with an activity to install a working LH{sub 2} cold source in the HFIR HB-4 beam tube. During the development of the reference design the liquid hydrogen concept was changed to a supercritical hydrogen system for a number of reasons. This report documents the reference supercritical hydrogen design and its performance. The cold source project has been divided into four phases: (1) preconceptual, (2) conceptual design and testing, (3) detailed design and procurement, and (4) installation and operation. This report marks the conclusion of the conceptual design phase and establishes the baseline reference concept.

Selby, D.L.; Lucas, A.T.; Hyman, C.R. [and others

1998-05-01

155

The mandibular incisor: rethinking guidelines for post and core design.  

PubMed

In post and core research, little attention has been given to the tooth with minimal bulk and mesialdistal width. The purpose of this in vitro study was to investigate retention and fracture characteristics of lower incisors restored with variable dowel designs. Fifty freshly extracted mandibular incisors were endodontically treated. Four groups of 10 teeth, decoronalized and dowel- and core-restored, were tested for retention characteristics and fracture resistance. One group of 10 teeth restored with composite resin in intact natural crown acted as controls. Dowel variables included a prefabricated round cross-sectional design and a morphologic dowel that reproduced the canal space. A universal testing machine created tensile and transverse loads, and failure was measured and recorded. Results showed no difference in resistance to transverse loading between morphological and standardized dowels (p > 0.05). However, when analyzing modes of failure, ferruled morphological post and core design was less likely to result in a catastrophic root or post fracture. In addition, morphological dowels were significantly more retentive than standardized round dowels in teeth with narrow cross-sections (p = 0.007). This study also reaffirmed the findings of previous investigations, that the intact natural crown of an endodontically treated tooth provides maximum resistance to root fracture. PMID:7714432

Gluskin, A H; Radke, R A; Frost, S L; Watanabe, L G

1995-01-01

156

Neutronic design of a Liquid Salt-cooled Pebble Bed Reactor (LSPBR)  

SciTech Connect

A renewed interest has been raised for liquid salt cooled nuclear reactors. The excellent heat transfer properties of liquid salt coolants provide several benefits, like lower fuel temperatures, higher coolant outlet temperatures, increased core power density and better decay heat removal. In order to benefit from the online refueling capability of a pebble bed reactor, the Liquid Salt Pebble Bed Reactor (LSPBR) is proposed. This is a high temperature pebble-bed reactor with a fuel design similar to existing HTRs, but using a liquid salt as a coolant. In this paper, the selection criteria for the liquid salt coolant are described. Based on its neutronic properties, LiF-BeF{sub 2} (FLIBE) was selected for the LSPBR. Two designs of the LSPBR were considered: a cylindrical core and an annular core with a graphite inner reflector. Coupled neutronic-thermal hydraulic calculations were performed to obtain the steady state power distribution and the corresponding fuel temperatures. Finally, calculations were performed to investigate the decay heat removal capability in a protected loss-of-forced cooling accident. The maximum allowable power that can be produced with the LSPBR is hereby determined. (authors)

De Zwaan, S. J.; Boer, B.; Lathouwers, D.; Kloosterman, J. L. [Delft Univ. of Technology (TUD), Mekelweg 15, 2629 JB Delft (Netherlands)

2006-07-01

157

Neutronic assessment of stringer fuel assembly design for liquid-salt-cooledvery high temperature reactor (LS-VHTR).  

SciTech Connect

Neutronic studies of 18-pin and 36-pin stringer fuel assemblies have been performed to ascertain that core design requirements for the Liquid-Salt Cooled Very High Temperature Reactor (LS-VHTR) can be met. Parametric studies were performed to determine core characteristics required to achieve a target core cycle length of 18 months and fuel discharge burnup greater than 100 GWd/t under the constraint that the uranium enrichment be less than 20% in order to support non-proliferation goals. The studies were done using the WIMS9 lattice code and the linear reactivity model to estimate the core reactivity balance, fuel composition, and discharge burnup. The results show that the design goals can be met using a 1-batch fuel management scheme, uranium enrichment of 15% and a fuel packing fraction of 30% or greater for the 36-pin stringer fuel assembly design.

Szakaly, F. J.; Kim, T. K.; Taiwo, T. A.

2006-09-15

158

Proton vs. neutron captures in the neutrino winds of core-collapse supernovae  

NASA Astrophysics Data System (ADS)

Recent one-dimensional (1D) hydrodynamical simulations of core-collapse supernovae (CCSNe) with a sophisticated treatment of neutrino transport indicate the neutrino-driven winds being proton-rich all the way until the end of their activity. This seems to exclude all possibilities of neutron-capture nucleosynthesis, but provide ideal conditions for the ?p-process, in neutrino winds. New 2D explosion simulations of electron-capture supernovae (ECSNe; a subset of CCSNe) exhibit, however, convective neutron-rich lumps, which are absent in the 1D case. Our nucleosynthesis calculations indicate that these neutron-rich lumps allow for interesting production of elements between iron group and N = 50 nuclei (Zn, Ge, As, Se, Br, Kr, Rb, Sr, Y, Zr, with little Ga). Our models do not confirm ECSNe as sources of the strong r-process (but possibly of a weak r-process up to Pd, Ag, and Cd in the neutron-rich lumps) nor of the ?p-process in the subsequent proton-rich outflows. We further study the ?p-process with semi-analytic models of neutrino winds assuming the physical conditions for CCSNe. We also explore the sensitivities of some key nuclear reaction rates to the nucleosynthetic abundances. Our result indicates that the ?/p-process in CCSNe (other than ECSNe) can be the origin of p-nuclei up to A = 108, and even up to A = 152 in limiting conditions.

Wanajo, S.; Janka, H.-T.; Müller, B.; Kubono, S.

2011-09-01

159

3D Core-Collapse Supernova Simulations: Neutron Star Kicks and Nickel Distribution  

NASA Astrophysics Data System (ADS)

We perform a set of neutrino-driven core-collapse supernova (CCSN) simulations studying the hydrodynamical neutron star kick mechanism in three-dimensions. Our simulations produce neutron star (NS) kick velocities in a range between ~100-600 km/s resulting mainly from the anisotropic gravitational tug by the asymmetric mass distribution behind the supernova shock. This stochastic kick mechanism suggests that a NS kick velocity of more than 1000 km/s may as well be possible. An enhanced production of heavy elements in the direction roughly opposite to the NS recoil direction is also observed as a result of the asymmetric explosion. This large scale asymmetry might be detectable and can be used to constrain the NS kick mechanism.

Wongwathanarat, Annop; Janka, Hans-Thomas; Müller, Ewald

2012-09-01

160

Thermal hydraulic response of the Advanced Neutron Source Reactor to piping breaks near the core region  

Microsoft Academic Search

This paper describes the application of the RELAP5 thermal hydraulic code to a highly subcooled, plate type reactor typical of many research and production reactor systems. The specific system modeled is the latest design of the Advanced Neutron Source Reactor (ANSR). A discussion of the model as well as the results from several loss-of-coolant accident (LOCA) scenarios is included. The

N. C. J. Chen; P. T. Williams; G. L. Yoder

1992-01-01

161

System design description for GCFR-core flow test loop  

SciTech Connect

The Core Flow Test Loop is a high-pressure, high-temperature, out-of-reactor helium circulation system that is being constructed to permit detailed study of the thermomechanical and thermal performance at prototypic steady-state and transient operating conditions of simulated segments of core assemblies for a GCFR Demonstration Plant, as designed by General Atomic Company. It will also permit the expermental verification of predictive analytical models of the GCFR core assemblies needed to reduce operational and safety uncertainties of the GCFR. Full-sized blanket assemblies and segments of fuel rod and control rod fuel assemblies will be simulated with test bundles of electrically powered fuel rod or blanket rod simulators. The loop will provide the steady-state and margin test requirements of bundle power and heat removal, and of helium coolant flow rate, pressure, and temperature for test bundles having up to 91 rods; these requirements set the maximum power, coolant helium flow, and thermal requirements for the loop. However, the size of the test vessel that contains the test bundles will be determined by the bundles that simulate a full-sized GCFR blanket assembly. The loop will also provide for power and coolant transients to simulate transient operation of GCFR core assemblies, including the capability for rapid helium depressurization to simulate the depressurization class of GCFR accidents. In addition, the loop can be used as an out-of-reactor test bed for characterizing in-reactor test bundle configurations.

Huntley, W.R.; Grindell, A.G.

1980-12-01

162

Coupled 3D-neutronics / thermal-hydraulics analysis of an unprotected loss-of-flow accident for a 3600 MWth SFR core  

SciTech Connect

The core behaviour of a large (3600 MWth) sodium-cooled fast reactor (SFR) is investigated in this paper with the use of a coupled TRACE/PARCS model. The SFR neutron spectrum is characterized by several performance advantages, but also leads to one dominating neutronics drawback - a positive sodium void reactivity. This implies a positive reactivity effect when sodium coolant is removed from the core. In order to evaluate such feedback in terms of the dynamics, a representative unprotected loss-of-flow (ULOF) transient, i.e. flow run-down without SCRAM in which sodium boiling occurs, is analyzed. Although analysis of a single transient cannot allow general conclusions to be drawn, it does allow better understanding of the underlying physics and can lead to proposals for improving the core response during such an accident. The starting point of this study is the reference core design considered in the framework of the Collaborative Project on the European Sodium Fast Reactor (CP-ESFR). To reduce the void effect, the core has been modified by introducing an upper sodium plenum (along with a boron layer) and by reducing the core height-to-diameter ratio. For the ULOF considered, a sharp increase in core power results in melting of the fuel in the case of the reference core. In the modified core, a large dryout leads to melting of the clad. It seems that, for the hypothetical event considered, fuel failure cannot be avoided with just improvement of the neutronics design; therefore, thermal-hydraulics optimization has been considered. An innovative assembly design is proposed to prevent sodium vapour blocking the fuel channel. This results in preventing a downward propagation of the sodium boiling to the core center, thus limiting it to the upper region. Such a void map introduces a negative coolant density reactivity feedback, which dominates the total reactivity change. As a result, the power level and the fuel temperature are effectively reduced, and a large dryout is prevented. As a next step, the classical sodium plenum is replaced by a fission gas plenum (with lower sodium fraction), thus improving flow stability. Stable boiling at a steady power level is achieved in this final configuration. (authors)

Sun, K. [Paul Scherrer Institut PSI, 5232 Villigen PSI (Switzerland); Ecole Polytechnique Federale de Lausanne EPFL, 1015 Lausanne (Switzerland); Chenu, A. [Ecole Polytechnique Federale de Lausanne EPFL, 1015 Lausanne (Switzerland); Mikityuk, K.; Krepel, J. [Paul Scherrer Institut PSI, 5232 Villigen PSI (Switzerland); Chawla, R. [Paul Scherrer Institut PSI, 5232 Villigen PSI (Switzerland); Ecole Polytechnique Federale de Lausanne EPFL, 1015 Lausanne (Switzerland)

2012-07-01

163

CHINA SPALLATION NEUTRON SOURCE ACCELERATORS: DESIGN, RESEARCH, AND DEVELOPMENT.  

SciTech Connect

The China Spallation Neutron Source (CSNS) is a newly approved high-power accelerator project based on a H{sup -} linear accelerator and a rapid cycling synchrotron. During the past year, several major revisions were made on the design including the type of the front end, the linac frequency, the transport layout, the ring lattice, and the type of ring components. Here, we discuss the rationale of design revisions, status of the R&D efforts, and upgrade considerations.

WEI, J.; FU, S.; FANG, S.

2006-06-26

164

Linac design study for an intense neutron-source driver  

SciTech Connect

The 1-MW spallation-neutron source under design study at Los Alamos is driven by a linac-compressor-ring scheme that utilizes a large portion of the existing Los Alamos Meson Physics Facility (LAMPF) linac, as well as the facility infrastructure. The project is referred to as the National Center for Neutron Research (NCNR). A second phase of the proposal will upgrade the driver power to 5 MW. A description of the 1-MW scheme is given in this paper. In addition, the upgrade path to the substantial increase of beam power required for the 5 MW scenario is discussed.

Lynch, M.T.; Browman, A.; DeHaven, R.; Jameson, R.; Jason, A.; Neuschaefer, G.; Tallerico, P.; Regan, A.

1993-06-01

165

Linac design study for an intense neutron-source driver  

SciTech Connect

The 1-MW spallation-neutron source under design study at Los Alamos is driven by a linac-compressor-ring scheme that utilizes a large portion of the existing Los Alamos Meson Physics Facility (LAMPF) linac, as well as the facility infrastructure. The project is referred to as the National Center for Neutron Research (NCNR). A second phase of the proposal will upgrade the driver power to 5 MW. A description of the 1-MW scheme is given in this paper. In addition, the upgrade path to the substantial increase of beam power required for the 5 MW scenario is discussed.

Lynch, M.T.; Browman, A.; DeHaven, R.; Jameson, R.; Jason, A.; Neuschaefer, G.; Tallerico, P.; Regan, A.

1993-01-01

166

Maximum mass of neutron stars and strange neutron-star cores  

NASA Astrophysics Data System (ADS)

Context. The recent measurement of mass of PSR J1614-2230 rules out most existing models of the equation of state (EOS) of dense matter with high-density softening due to hyperonization that were based on the recent hyperon-nucleon and hyperon-hyperon interactions, which leads to a "hyperon puzzle". Aims: We study a specific solution of this hyperon puzzle that consists of replacing a too soft hyperon core by a sufficiently stiff quark core. In terms of the quark structure of the matter, one replaces a strangeness-carrying baryon phase of confined quark triplets, some of them involving s quarks, by a quark plasma of deconfined u, d, and s quarks. Methods: We constructed an analytic approximation that fits modern EOSs of the two flavor (2SC) and the color-flavor-locked (CFL) color-superconducting phases of quark matter very well. Then, we used it to generate a continuum of EOSs of quark matter. This allowed us to simulate continua of sequences of first-order phase transitions at prescribed pressures, from hadronic matter to the 2SC and then to the CFL state of color-superconducting quark matter. Results: We obtain constraints in the parameter space of the EOS of superconducting quark cores, EOS.Q, resulting from Mmax > 2 M?. These constraints depend on the assumed EOS of baryon phase, EOS.B. We also derive constraints that would result from significantly higher measured masses. For 2.4 M? the required stiffness of the CFL quark core is close to the causality limit while the density jump at the phase transition is very small. Conclusions: The condition Mmax > 2 M? puts strong constraints on the EOSs of the 2SC and CFL phases of quark matter. Density jumps at the phase transitions have to be sufficiently small and sound speeds in quark matter sufficiently large. The condition of thermodynamic stability of the quark phase results in a maximum mass of hybrid stars similar to that of purely baryon stars. This is due to the phase transition of quark matter back to the baryon phase (reconfinement) that we find for both EOS.B. Therefore, to obtain Mmax > 2 M? for hybrid stars, both sufficiently strong additional hyperon repulsion at high-density baryon matter and a sufficiently stiff EOS of quark matter would be needed. However, we think that the high-density instability, which results in the reconfinement of quark matter, indicates actually the inadequacy of the point-particle model of baryons in dense matter at ? ? 5 ÷ 8?0. We expect that reconfinement can be removed by a sufficient stiffening of the baryon phase, resulting from the repulsive finite size contribution for baryons to the EOS.

Zdunik, J. L.; Haensel, P.

2013-03-01

167

Characterization of core debris/concrete interactions for the Advanced Neutron Source  

SciTech Connect

This report provides the results of a recent study conducted to explore the molten core/concrete interaction (MCCI) issue for the Advanced Neutron Source (ANS). The need for such a study arises from the potential threats to reactor system integrity posed by MCCI. These threats include direct attack of the concrete basemat of the containment; generation and release of large quantities of gas that can pressurize the containment; the combustion threat of these gases; and the potential generation, release, and transport of radioactive aerosols to the environment.

Hyman, C.R.; Taleyarkhan, R.P.

1992-02-01

168

Neutronic design studies for an unattended, low power reactor  

SciTech Connect

The Los Alamos National Laboratory is involved in the design and demonstrations of a small, long-lived nuclear heat and electric power source for potential applications at remote sites where alternate fossil energy systems would not be cost effective. This paper describes the neutronic design analysis that was performed to arrive at two conceptual designs, one using thermoelectric conversion, the other using an organic Rankine cycle. To meet the design objectives and constraints a number of scoping and optimization studies were carried out. The results of calculations of control worths, temperature coefficients of reactivity and fuel depletion effects are reported.

Palmer, R.G.; Durkee, J.W. Jr.

1986-01-01

169

Status of axial heterogeneous liquid-metal fast breeder reactor core design studies and research and development  

Microsoft Academic Search

The current status of axial heterogeneous core (AHC) design development in Japan, which consists of an AHC core design in a pool-type demonstration fast breeder reactor (DFBR) and research and development activities supporting AHC core design, is presented. The DFBR core design objectives developed by The Japan Atomic Power Company include (a) favorable core seismic response, (b) core compactness, (c)

H. Nakagawa; T. Inagaki; H. Yoshimi; K. Shirakata; Y. Watari; M. Suzuki; K. Inoue

1988-01-01

170

Coupled full core neutron transport/CFD simulations of pressurized water reactors  

SciTech Connect

Recently as part of the CASL project, a capability to perform 3D whole-core coupled neutron transport and computational fluid dynamics (CFD) calculations was demonstrated. This work uses the 2D/1D transport code DeCART and the commercial CFD code STAR-CCM+. It builds on previous CASL work demonstrating coupling for smaller spatial domains. The coupling methodology is described along with the problem simulated and results are presented for fresh hot full power conditions. An additional comparison is made to an equivalent model that uses lower order T/H feedback to assess the importance and cost of high fidelity feedback to the neutronics problem. A simulation of a quarter core Combustion Engineering (CE) PWR core was performed with the coupled codes using a Fixed Point Gauss-Seidel iteration technique. The total approximate calculation requirements are nearly 10,000 CPU hours and 1 TB of memory. The problem took 6 coupled iterations to converge. The CFD coupled model and low order T/H feedback model compared well for global solution parameters, with a difference in the critical boron concentration and average outlet temperature of 14 ppm B and 0.94 deg. C, respectively. Differences in the power distribution were more significant with maximum relative differences in the core-wide pin peaking factor (Fq) of 5.37% and average relative differences in flat flux region power of 11.54%. Future work will focus on analyzing problems more relevant to CASL using models with less approximations. (authors)

Kochunas, B.; Stimpson, S.; Collins, B.; Downar, T. [Dept. of Nuclear Engineering and Radiological Sciences, Univ. of Michigan, 2200 Bonisteel Blvd, Ann Arbor, MI 48104 (United States); Brewster, R.; Baglietto, E. [CD-adapco, 60 Broadhollow Road, Melville, NY 11747 (United States); Yan, J. [Westinghouse Electric Company LLC, Columbia, SC (United States)

2012-07-01

171

BEAM DUMP WINDOW DESIGN FOR THE SPALLATION NEUTRON SOURCE.  

SciTech Connect

The Spallation Neutron Source accelerator systems will provide a 1 GeV, 1.44 MW proton beam to a liquid mercury target for neutron production. Beam tuning dumps are provided at the end of the linac (the Linac Dump) and in the Ring-to-Target transport line (the Extraction Dump) [1]. Thin windows are required to separate the accelerator vacuum from the poor vacuum upstream of the beam dump. There are several challenging engineering issues that have been addressed in the window design. Namely, handling of the high local power density deposited by the stripped electrons from the H-beam accelerated in the linac, and the need for low-exposure removal and replacement of an activated window. The thermal design of the linac dump window is presented, as is the design of a vacuum clamp and mechanism that allows remote removal and replacement of the window.

RAPARIA,D.RANK,J.MURDOCH,G.ET AL.

2004-03-10

172

5 MW pulsed spallation neutron source, Preconceptual design study  

SciTech Connect

This report describes a self-consistent base line design for a 5 MW Pulsed Spallation Neutron Source (PSNS). It is intended to establish feasibility of design and as a basis for further expanded and detailed studies. It may also serve as a basis for establishing project cost (30% accuracy) in order to intercompare competing designs for a PSNS not only on the basis of technical feasibility and technical merit but also on the basis of projected total cost. The accelerator design considered here is based on the objective of a pulsed neutron source obtained by means of a pulsed proton beam with average beam power of 5 MW, in {approx} 1 {mu}sec pulses, operating at a repetition rate of 60 Hz. Two target stations are incorporated in the basic facility: one for operation at 10 Hz for long-wavelength instruments, and one operating at 50 Hz for instruments utilizing thermal neutrons. The design approach for the proton accelerator is to use a low energy linear accelerator (at 0.6 GeV), operating at 60 Hz, in tandem with two fast cycling booster synchrotrons (at 3.6 GeV), operating at 30 Hz. It is assumed here that considerations of cost and overall system reliability may favor the present design approach over the alternative approach pursued elsewhere, whereby use is made of a high energy linear accelerator in conjunction with a dc accumulation ring. With the knowledge that this alternative design is under active development, it was deliberately decided to favor here the low energy linac-fast cycling booster approach. Clearly, the present design, as developed here, must be carried to the full conceptual design stage in order to facilitate a meaningful technology and cost comparison with alternative designs.

Not Available

1994-06-01

173

Designing accelerator-based epithermal neutron beams for boron neutron capture therapy.  

PubMed

The 7Li(p,n)7Be reaction has been investigated as an accelerator-driven neutron source for proton energies between 2.1 and 2.6 MeV. Epithermal neutron beams shaped by three moderator materials, Al/AlF3, 7LiF, and D2O, have been analyzed and their usefulness for boron neutron capture therapy (BNCT) treatments evaluated. Radiation transport through the moderator assembly has been simulated with the Monte Carlo N-particle code (MCNP). Fluence and dose distributions in a head phantom were calculated using BNCT treatment planning software. Depth-dose distributions and treatment times were studied as a function of proton beam energy and moderator thickness. It was found that an accelerator-based neutron source with Al/AlF3 or 7LiF as moderator material can produce depth-dose distributions superior to those calculated for a previously published neutron beam design for the Brookhaven Medical Research Reactor, achieving up to approximately 50% higher doses near the midline of the brain. For a single beam treatment, a proton beam current of 20 mA, and a 7LiF moderator, the treatment time was estimated to be about 40 min. The tumor dose deposited at a depth of 8 cm was calculated to be about 21 Gy-Eq. PMID:9775379

Bleuel, D L; Donahue, R J; Ludewigt, B A; Vujic, J

1998-09-01

174

Pre-conceptual design and preliminary neutronic analysis of the proposed National Spallation Neutron Source (NSNS)  

SciTech Connect

The Department of Energy (DOE) has initiated a pre-conceptual design study for the National Spallation Neutron Source (NSNS) and given preliminary approval for the proposed facility to be built at Oak Ridge National Laboratory (ORNL). The pre-conceptual design of the NSNS initially consists of an accelerator system capable of delivering a 1 to 2 GeV proton beam with 1 MW of beam power in an approximate 0.5 {micro}s pulse at a 60 Hz frequency onto a single target station. The NSNS will be upgradable to a significantly higher power level with two target stations (a 60 Hz station and a 10 Hz station). There are many possible layouts and designs for the NSNS target stations. This paper gives a brief overview of the proposed NSNS with respect to the target station, as well as the general philosophy adopted for the neutronic design of the NSNS target stations. A reference design is presented, and some preliminary neutronic results for the NSNS are briefly discussed.

Johnson, J.O.; Barnes, J.M.; Charlton, L.A. [Oak Ridge National Lab., TN (United States). Computational Physics and Engineering Div.

1997-03-01

175

Advanced Neutron Source: Plant Design Requirements. Revision 4  

SciTech Connect

The Advanced Neutron Source will be a new world-class facility for research using hot, thermal, cold, and ultra-cold neutrons. The heart of the facility will be a 330-MW (fission), heavy-water cooled and heavy-water moderated reactor. The reactor will be housed in a central reactor building, with supporting equipment located in an adjoining reactor support building. An array of cold neutron guides will fan out into a large guide hall, housing about 30 neutron research stations. Appropriate office, laboratory, and shop facilities will be included to provide a complete facility for users. The ANS is scheduled to begin operation at the Oak Ridge National Laboratory early in the next decade. This PDR document defines the plant-level requirements for the design, construction, and operation of ANS. It also defines and provides input to the individual System Design Description (SDD) documents. Together, this PDR document and the set of SDD documents will define and control the baseline configuration of ANS.

Not Available

1990-07-01

176

Monte Carlo methods of neutron beam design for neutron capture therapy at the MIT Research Reactor (MITR-II)  

Microsoft Academic Search

Monte Carlo methods of coupled neutron\\/photon transport are being used in the design of filtered beams for Neutron Capture Therapy (NCT). This method of beam analysis provides segregation of each individual dose component, and thereby facilitates beam optimization. The Monte Carlo method is discussed in some detail in relation to NCT epithermal beam design. Ideal neutron beams (i.e., plane-wave monoenergetic

S. D. Clement; J. R. Choi; R. G. Zamenhof; J. C. Yanch; O. K. Harling

1990-01-01

177

Design and Testing of a Position-Sensitive Plastic Scintillator Detector for Fast Neutron Imaging  

Microsoft Academic Search

We describe the design and performance of a position sensitive scintillator detector developed for neutron measurements. Several of these detectors are to be used in the assembly of the Fast Neutron Imaging Telescope (FNIT), an instrument with imaging and energy measurement capabilities, sensitive to neutrons in the 2-20 MeV energy range. FNIT was initially conceived to study solar neutrons as

Ulisse Bravar; Paul J. Bruillard; Erwin O. Flückiger; John R. Macri; Mark L. McConnell; Michael R. Moser; James M. Ryan; Richard S. Woolf

2006-01-01

178

Picosecond lifetime measurement of neutron core-excited states in the N=50 nucleus 95Rh  

NASA Astrophysics Data System (ADS)

Lifetimes of high-spin states in the N=50 nucleus 95Rh were measured using the recoil-distance Doppler-shift technique. The nuclei were produced via the reaction 58Ni(40Ca,3p) at 145 MeV beam energy and the ? radiation was detected in six EUROBALL cluster detectors. Reduced transition probabilities for seventeen ? transitions and limits for nine further transitions were extracted and compared with the predictions of the spherical shell model based on the extended configuration space, (0f5/2, 1p3/2, 1p1/2, 0g9/2) for protons and (0g9/2, 1d5/2) for neutrons relative to a hypothetical 68Ni core. The results indicate that all observed states with 27/2 <=I <=39/2 are built from a neutron g9/2 -->d5/2 excitation across the N=50 shell closure, coupled to up to five valence protons in different configurations. Evidence of stretched dipole cascades having large M1 strengths was found and explained by spin recoupling within the ?(g9/2)-1?(d5/2) neutron part of the wavefunctions.

Jungclaus, A.; Kast, D.; Lieb, K. P.; Teich, C.; Weiszflog, M.; Härtlein, T.; Ender, C.; Köck, F.; Schwalm, D.; Reif, J.; Peusquens, R.; Dewald, A.; Eberth, J.; Thomas, H.-G.; Górska, M.; Grawe, H.

1998-07-01

179

The determination of neutron energy spectrum in reactor core C1 of reactor VR-1 Sparrow  

SciTech Connect

This contribution overviews neutron spectrum measurement, which was done on training reactor VR-1 Sparrow with a new nuclear fuel. Former nuclear fuel IRT-3M was changed for current nuclear fuel IRT-4M with lower enrichment of 235U (enrichment was reduced from former 36% to 20%) in terms of Reduced Enrichment for Research and Test Reactors (RERTR) Program. Neutron spectrum measurement was obtained by irradiation of activation foils at the end of pipe of rabit system and consecutive deconvolution of obtained saturated activities. Deconvolution was performed by computer iterative code SAND-II with 620 groups' structure. All gamma measurements were performed on Canberra HPGe. Activation foils were chosen according physical and nuclear parameters from the set of certificated foils. The Resulting differential flux at the end of pipe of rabit system agreed well with typical spectrum of light water reactor. Measurement of neutron spectrum has brought better knowledge about new reactor core C1 and improved methodology of activation measurement. (author)

Vins, M. [Department of Nuclear Reactors, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, V Holesovickach 2, 180 00 Prague 8 (Czech Republic)], E-mail: vinsmiro@seznam.cz

2008-07-15

180

The Double Pulsar: Evidence for Neutron Star Formation without an Iron Core-collapse Supernova  

NASA Astrophysics Data System (ADS)

The double pulsar system PSR J0737–3039A/B is a double neutron star binary, with a 2.4 hr orbital period, which has allowed measurement of relativistic orbital perturbations to high precision. The low mass of the second-formed neutron star, as well as the low system eccentricity and proper motion, point to a different evolutionary scenario compared to most other known double neutron star systems. We describe analysis of the pulse profile shape over 6 years of observations and present the resulting constraints on the system geometry. We find the recycled pulsar in this system, PSR J0737–3039A, to be a near-orthogonal rotator with an average separation between its spin and magnetic axes of 90° ± 11° ± 5°. Furthermore, we find a mean 95% upper limit on the misalignment between its spin and orbital angular momentum axes of 3.°2, assuming that the observed emission comes from both magnetic poles. This tight constraint lends credence to the idea that the supernova that formed the second pulsar was relatively symmetric, possibly involving electron capture onto an O-Ne-Mg core.

Ferdman, R. D.; Stairs, I. H.; Kramer, M.; Breton, R. P.; McLaughlin, M. A.; Freire, P. C. C.; Possenti, A.; Stappers, B. W.; Kaspi, V. M.; Manchester, R. N.; Lyne, A. G.

2013-04-01

181

Natural nuclear reactor at Oklo and variation of fundamental constants: Computation of neutronics of a fresh core  

SciTech Connect

Using modern methods of reactor physics, we performed full-scale calculations of the Oklo natural reactor. For reliability, we used recent versions of two Monte Carlo codes: the Russian code MCU-REA and the well-known international code MCNP. Both codes produced similar results. We constructed a computer model of the Oklo reactor zone RZ2 which takes into account all details of design and composition. The calculations were performed for three fresh cores with different uranium contents. Multiplication factors, reactivities, and neutron fluxes were calculated. We also estimated the temperature and void effects for the fresh core. As would be expected, we found for the fresh core a significant difference between reactor and Maxwell spectra, which had been used before for averaging cross sections in the Oklo reactor. The averaged cross section of {sub 62}{sup 149}Sm and its dependence on the shift of a resonance position E{sub r} (due to variation of fundamental constants) are significantly different from previous results. Contrary to the results of previous papers, we found no evidence of a change of the samarium cross section: a possible shift of the resonance energy is given by the limits -73{<=}{delta}E{sub r}{<=}62 meV. Following tradition, we have used formulas of Damour and Dyson to estimate the rate of change of the fine structure constant {alpha}. We obtain new, more accurate limits of -4x10{sup -17}{<=}{alpha}{center_dot}/{alpha}{<=}3x10{sup -17} yr{sup -1}. Further improvement of the accuracy of the limits can be achieved by taking account of the core burn-up. These calculations are in progress.

Petrov, Yu. V.; Nazarov, A. I.; Onegin, M. S.; Petrov, V. Yu.; Sakhnovsky, E. G. [St. Petersburg Nuclear Physics Institute, Gatchina, RU-188-300, St. Petersburg (Russian Federation)

2006-12-15

182

Development of an inconel self powered neutron detector for in-core reactor monitoring  

NASA Astrophysics Data System (ADS)

The paper describes the development and testing of an Inconel600 (2 mm diameter×21 cm long) self-powered neutron detector for in-core neutron monitoring. The detector has 3.5 mm overall diameter and 22 cm length and is integrally coupled to a 12 m long mineral insulated cable. The performance of the detector was compared with cobalt and platinum detectors of similar dimensions. Gamma sensitivity measurements performed at the 60Co irradiation facility in 14 MR/h gamma field showed values of -4.4×10-18 A/R/h/cm (-9.3×10-24 A/?/cm2-s/cm), -5.2×10-18 A/R/h/cm (-1.133×10-23 A/?/cm2-s/cm) and 34×10-18 A/R/h/cm (7.14×10-23 A/?/cm2-s/cm) for the Inconel, Co and Pt detectors, respectively. The detectors together with a miniature gamma ion chamber and fission chamber were tested in the in-core Apsara Swimming Pool type reactor. The ion chambers were used to estimate the neutron and gamma fields. With an effective neutron cross-section of 4b, the Inconel detector has a total sensitivity of 6×10-23 A/nv/cm while the corresponding sensitivities for the platinum and cobalt detectors were 1.69×10-22 and 2.64×10-22 A/nv/cm. The linearity of the detector responses at power levels ranging from 100 to 200 kW was within ±5%. The response of the detectors to reactor scram showed that the prompt response of the Inconel detector was 0.95 while it was 0.7 and 0.95 for the platinum and cobalt self-powered detectors, respectively. The detector was also installed in the horizontal flux unit of 540 MW Pressurised Heavy Water Reactor (PHWR). The neutron flux at the detector location was calculated by Triveni code. The detector response was measured from 0.02% to 0.07% of full power and showed good correlation between power level and detector signals. Long-term tests and the dynamic response of the detector to shut down in PHWR are in progress.

Alex, M.; Ghodgaonkar, M. D.

2007-04-01

183

Nuclear design of a vapor core reactor for space nuclear propulsion  

NASA Astrophysics Data System (ADS)

Neutronic analysis methodology and results are presented for the nuclear design of a vapor core reactor for space nuclear propulsion. The Nuclear Vapor Thermal Reactor (NVTR) Rocket Engine uses modified NERVA geometry and systems which the solid fuel replaced by uranium tetrafluoride vapor. The NVTR is an intermediate term gas core thermal rocket engine with specific impulse in the range of 1000-1200 seconds; a thrust of 75,000 lbs for a hydrogen flow rate of 30 kg/s; average core exit temperatures of 3100 K to 3400 K; and reactor thermal powers of 1400 to 1800 MW. Initial calculations were performed on epithermal NVTRs using ZrC fuel elements. Studies are now directed at thermal NVTRs that use fuel elements made of C-C composite. The large ZrC-moderated reactors resulted in thrust-to-weight ratios of only 1 to 2; the compact C-C composite systems yield thrust-to-weight ratios of 3 to 5.

Dugan, Edward T.; Watanabe, Yoichi; Kuras, Stephen A.; Maya, Isaac; Diaz, Nils J.

1993-01-01

184

GEANT4 used for neutron beam design of a neutron imaging facility at TRIGA reactor in Morocco  

NASA Astrophysics Data System (ADS)

Neutron imaging has a broad scope of applications and has played a pivotal role in visualizing and quantifying hydrogenous masses in metallic matrices. The field continues to expand into new applications with the installation of new neutron imaging facilities. In this scope, a neutron imaging facility for computed tomography and real-time neutron radiography is currently being developed around 2.0MW TRIGA MARK-II reactor at Maamora Nuclear Research Center in Morocco (Reuscher et al., 1990 [1] ; de Menezes et al., 2003 [2] ; Deinert et al., 2005 [3] ). The neutron imaging facility consists of neutron collimator, real-time neutron imaging system and imaging process systems. In order to reduce the gamma-ray content in the neutron beam, the tangential channel was selected. For power of 250 kW, the corresponding thermal neutron flux measured at the inlet of the tangential channel is around 3×10 11 ncm 2 /s. This facility will be based on a conical neutron collimator with two circular diaphragms with diameters of 4 and 2 cm corresponding to L/D-ratio of 165 and 325, respectively. These diaphragms' sizes allow reaching a compromise between good flux and efficient L/D-ratio. Convergent-divergent collimator geometry has been adopted. The beam line consists of a gamma filter, fast neutrons filter, neutron moderator, neutron and gamma shutters, biological shielding around the collimator and several stages of neutron collimator. Monte Carlo calculations by a fully 3D numerical code GEANT4 were used to design the neutron beam line ( http://www.info.cern.ch/asd/geant4/geant4.html [4] ). To enhance the neutron thermal beam in terms of quality, several materials, mainly bismuth (Bi) and sapphire (Al 2 O 3 ) were examined as gamma and neutron filters respectively. The GEANT4 simulations showed that the gamma and epithermal and fast neutron could be filtered using the bismuth (Bi) and sapphire (Al 2 O 3 ) filters, respectively. To get a good cadmium ratio, GEANT 4 simulations were used to define the design of the moderator in the inlet of the radiation channel. A graphite block of 22 cm thickness seems to be the optimal neutron moderator. The results showed that the combination of 5 cm of bismuth with 5 cm of sapphire permits the filtration of gamma-rays, epithermal neutrons as well as fast neutrons in a considerable way without affecting the neutron thermal flux.

Ouardi, A.; Machmach, A.; Alami, R.; Bensitel, A.; Hommada, A.

2011-09-01

185

Development of neutron chambers with improved electrode design  

NASA Astrophysics Data System (ADS)

A boron-lined neutron chamber has been developed with improved electrode design. The use of suitably machined PEEK spacers at the ends of the electrodes resulted in better performance of the ion chamber. The performance of the ion chamber was compared with a similar detector developed earlier with alumina discs. Neutron sensitivity tests on both types of chambers at Apsara Thermal Column chamber showed a sharper knee in the case of the chamber with PEEK spacers due to well-defined volume and elimination of edge and fringe effects. Tests with a calibrated 60Co Teletherapy source at gamma intensity levels ranging from 900 to 3000R/h showed an average gamma compensation factor of 3.8%. The corresponding value for chambers with the alumina discs was 11.5%. A plot of the compensation factor as a function of gamma flux, showed a much more pronounced variation in the gamma compensation factor in the earlier design using alumina discs.

Alex, Mary; Prasad, D. N.; Prasad, K. R.; Kataria, S. K.

2004-07-01

186

Shielding Design of the Spallation Neutron Source (SNS)  

SciTech Connect

The shielding design is important for the construction of an intense high-energy accelerator facility like the proposed Spallation Neutron Source (SNS) due to its impact on conventional facility design, maintenance operations, and since the cost for the radiation shielding shares a considerable part of the total facility costs. A calculational strategy utilizing coupled high energy Monte Carlo calculations and multi-dimensional discrete ordinates calculations, along with semi-empirical calculations, was implemented to perform the conceptual design shielding assessment of the proposed SNS. Biological shields have been designed and assessed for the proton beam transport system and associated beam dumps, the target station, and the target service cell and general remote maintenance cell. Shielding requirements have been assessed with respect to weight, space, and dose-rate constraints for operating, shutdown, and accident conditions. A discussion of the proposed facility design, conceptual design shielding requirements, calculational strategy, source terms, preliminary results and conclusions, and recommendations for additional analyses are presented.

Johnson, J.O.

1998-09-17

187

The Spallation Neutron Source (SNS) conceptual design shielding analysis  

SciTech Connect

The shielding design is important for the construction of an intense high-energy accelerator facility like the proposed Spallation Neutron Source (SNS) due to its impact on conventional facility design, maintenance operations, and since the cost for the radiation shielding shares a considerable part of the total facility costs. A calculational strategy utilizing coupled high energy Monte Carlo calculations and multi-dimensional discrete ordinates calculations, along with semi-empirical calculations, was implemented to perform the conceptual design shielding assessment of the proposed SNS. Biological shields have been designed and assessed for the proton beam transport system and associated beam dumps, the target station, and the target service cell and general remote maintenance cell. Shielding requirements have been assessed with respect to weight, space, and dose-rate constraints for operating, shutdown, and accident conditions. A discussion of the proposed facility design, conceptual design shielding requirements calculational strategy, source terms, preliminary results and conclusions, and recommendations for additional analyses are presented.

Johnson, J.O.; Odano, N.; Lillie, R.A.

1998-03-01

188

Documented Safety Analysis Addendum for the Neutron Radiography Reactor Facility Core Conversion  

SciTech Connect

The Neutron Radiography Reactor Facility (NRAD) is a Training, Research, Isotope Production, General Atomics (TRIGA) reactor which was installed in the Idaho National Laboratory (INL) Hot Fuels Examination Facility (HFEF) at the Materials and Fuels Complex (MFC) in the mid 1970s. The facility provides researchers the capability to examine both irradiated and non-irradiated materials in support of reactor fuel and components programs through non-destructive neutron radiography examination. The facility has been used in the past as one facet of a suite of reactor fuels and component examination facilities available to researchers at the INL and throughout the DOE complex. The facility has also served various commercial research activities in addition to the DOE research and development support. The reactor was initially constructed using Fuel Lifetime Improvement Program (FLIP)- type highly enriched uranium (HEU) fuel obtained from the dismantled Puerto Rico Nuclear Center (PRNC) reactor. In accordance with international non-proliferation agreements, the NRAD core will be converted to a low enriched uranium (LEU) fuel and will continue to utilize the PRNC control rods, control rod drives, startup source, and instrument console as was previously used with the HEU core. The existing NRAD Safety Analysis Report (SAR) was created and maintained in the preferred format of the day, combining sections of both DOE-STD-3009 and Nuclear Regulatory Commission Regulatory Guide 1.70. An addendum was developed to cover the refueling and reactor operation with the LEU core. This addendum follows the existing SAR format combining required formats from both the DOE and NRC. This paper discusses the project to successfully write a compliant and approved addendum to the existing safety basis documents.

Boyd D. Christensen

2009-05-01

189

Core transform design for high-efficiency video coding  

NASA Astrophysics Data System (ADS)

High Efficiency Video Coding (HEVC) is the next generation video coding standard currently being developed by the Joint Collaborative Team on Video Coding (JCT-VC). It employs various coding unit sizes 2K×2K, where K is a positive integer with the typical values from 3 to 6; it also uses larger transform sizes up to 32×32. This raises the interest in seeking high performance higher order integer transforms with low computation requirements. This paper presents approaches to designing order-N (N=4, 8, 16, 32) integer transforms, by which the derived integer transforms have special symmetry structures to ensure the matrix factorization. The proposed set of high order integer transforms with well selected elements demonstrates excellent coding performance, compared with the core transform design in HEVC.

Dong, Jie; Ye, Yan

2012-10-01

190

Initial global 2-D shielding analysis for the Advanced Neutron Source core and reflector  

SciTech Connect

This document describes the initial global 2-D shielding analyses for the Advanced Neutron Source (ANS) reactor, the D{sub 2}O reflector, the reflector vessel, and the first 200 mm of light water beyond the reflector vessel. Flux files generated here will later serve as source terms in subsequent shielding analyses. In addition to reporting fluxes and other data at key points of interest, a major objective of this report was to document how these analyses were performed, the phenomena that were included, and checks that were made to verify that these phenomena were properly modeled. In these shielding analyses, the fixed neutron source distribution in the core was based on the `lifetime-averaged` spatial power distribution. Secondary gamma production cross sections in the fuel were modified so as to account intrinsically for delayed fission gammas in the fuel as well as prompt fission gammas. In and near the fuel, this increased the low-energy gamma fluxes by 50 to 250%, but out near the reflector vessel, these same fluxes changed by only a few percent. Sensitivity studies with respect to mesh size were performed, and a new 2-D mesh distribution developed after some problems were discovered with respect to the use of numerous elongated mesh cells in the reflector. All of the shielding analyses were performed sing the ANSL-V 39n/44g coupled library with 25 thermal neutron groups in order to obtain a rigorous representation of the thermal neutron spectrum throughout the reflector. Because of upscatter in the heavy water, convergence was very slow. Ultimately, the fission cross section in the various materials had to be artificially modified in order to solve this fixed source problem as an eigenvalue problem and invoke the Vondy error-mode extrapolation technique which greatly accelerated convergence in the large 2-D RZ DORT analyses. While this was quite effective, 150 outer iterations (over energy) were still required.

Bucholz, J.A.

1995-08-01

191

Aperture design and numerical reconstruction technique requirements for high-resolution imaging of neutrons in inertial confinement fusion (ICF)  

NASA Astrophysics Data System (ADS)

In Inertial Confinement Factor (ICF) experiments, radiation from compressed core is increasingly reabsorbed. For the largest experiments, the only radiation to escape is the 14 MeV fusion neutrons to which we must turn to learn of the physical processes taking place. The most important parameters are the shape and the size of the compressed core and this involves imaging the neutrons produced by the fusion reactions. The penumbral technique is ideally suited to neutron imaging and the feasibility of this technique has been demonstrated at the Lawrence Livermore National Laboratory in the United States. At the Phebus laser facility in France, this method has been used to image compressed ICF cores with diameters of 150 micrometers yielding approximately 109 neutrons, and the overall spatial resolution obtained in the reconstructed source was approximately 100 micrometers . On the Laser Megajoule project which is the equivalent of the National Ignition Facility in the United States, the spatial resolution required to diagnose high-convergence targets is 10 micrometers . We wish first to obtain a spatial resolution of 30 micrometers to image source with a diameter neutron yield in the range of 1011 - 1014 neutrons. A collaborative experimental program with the Laboratory for Laser Energetics at the University of Rochester in this perspective is planned. At the same time, there is a research program in collaboration with Laval University concerning coded aperture designs and the associated reconstruction techniques. In this article we first review the basic requirements of such imagery and the concept of the penumbral imaging technique. Then we concentrate on the aperture design criteria and on the quantity of information necessary to achieve high spatial resolution. Finally, we survey the reconstruction techniques used followed by results and comparative evaluation of those methods.

Delage, Olivier; Arsenault, Henri H.

1998-10-01

192

Designing for safety in the conceptual design of the advanced neutron source  

Microsoft Academic Search

The Advanced Neutron Source (ANS) is a new research reactor facility for the Department of Energy currently in conceptual design at the Oak Ridge National Laboratory. Major design concepts for the heavy-water-cooled, -moderated, and -reflected reactor are described. The overall approach to nuclear safety adopted for the ANS relies heavily on probabilistic risk assessment and the incorporation of inherent means

1991-01-01

193

Neutron scattering studies and modeling of high mobility group 14 core nucleosome complex.  

PubMed Central

Considerable evidence relates the nonhistone proteins high mobility group (HMG) 14 and HMG 17 with the structure of active or potentially active chromatin. In this study, bulk nucleosome core particles prepared from chicken erythrocytes and the complex formed by binding two HMG 14 molecules per nucleosome core were studied by use of small-angle neutron scattering techniques. By varying the H2O/2H2O ratio, and hence the contrast between the solvent and the particles, it was possible to determine the radius of gyration of the protein and of the DNA independently and as a function of HMG 14 binding. The results show an increase of 0.9 +/- 0.6 A (mean +/- SEM) in the protein radius of gyration and of 2.7 +/- 0.6 A in the DNA radius of gyration upon binding of HMG 14 to the nucleosome. These changes are considered in the light of several postulated modes for the unfolding or perturbation of the nucleosome structure. Modeling calculations demonstrate that the observed changes in radius of gyration for the DNA and for the protein are too small to be consistent with an overall unfolding or opening of the core particle upon HMG 14 binding. However, the observed changes are consistent with several models that involve only minor changes in the structure. It is postulated that the differences observed may be an indication of the type of conformational change occurring in active nucleosomes. Images

Uberbacher, E C; Mardian, J K; Rossi, R M; Olins, D E; Bunick, G J

1982-01-01

194

Neutronic analysis of the conversion of HEU to LEU fuel for a 5-MW MTR core  

SciTech Connect

In recent years, due to cessation of highly enriched uranium (HEU) fuel supply, practical steps have been taken to substitute HEU fuel in almost all research reactors by medium-enriched uranium or low-enriched uranium (LEU) fuels. In this study, a neutronic calculation of a 5-MW research reactor core fueled with HEU (93% /sup 235/U) is presented. In order to assess the performance of the core with the LEU (< 20%) fuel replacement, while keeping fuel element geometry nearly unchanged, several different /sup 235/U loadings were examined. The core consists of 22 standard fuel elements (SFEs) and 6 control fuel elements (CFEs). Each fuel elements has 18 curved plates of which two end plates are dummies. Initial /sup 235/U content is 195 g /sup 235/U/SFE and 9.7 g /sup 235/U/CFE or /PFE. In all calculations the permitted changes to the fuel elements are (a) 18 active plates per SFE, (b) fuel plates assumed to be flat, and (c) 8 or 9 active plates per CFE.

Pazirandeh, A.; Bartsch, G.

1987-01-01

195

A New Equation of State for Neutron Star Matter with Nuclei in the Crust and Hyperons in the Core  

NASA Astrophysics Data System (ADS)

The equation of state for neutron stars in a wide-density range at zero temperature is constructed. The chiral quark-meson coupling model within relativistic Hartree-Fock approximation is adopted for uniform nuclear matter. The coupling constants are determined so as to reproduce the experimental data of atomic nuclei and hypernuclei. In the crust region, nuclei are taken into account within the Thomas-Fermi calculation. All octet baryons are considered in the core region, while only ?– appears in neutron stars. The resultant maximum mass of neutron stars is 1.95 M ?, which is consistent with the constraint from the recently observed massive pulsar, PSR J1614-2230.

Miyatsu, Tsuyoshi; Yamamuro, Sachiko; Nakazato, Ken'ichiro

2013-11-01

196

Physics design of the National Spallation Neutron Source linac  

SciTech Connect

The National Spallation Neutron Source (NSNS) requires a linac that accelerates a H{sup {minus}} beam to 1.0 GeV. The linac starts with a radio-frequency quadrupole (RFQ) accelerator, which is followed by a drift-tube linac (DTL), a coupled-cavity drift-tube linac (CCDTL), and a conventional coupled-cavity linac (CCL). In this paper, the authors focus on the DTL, CCDTL, and CCL parts of the accelerator. They discuss the linac design parameters and beam dynamics issues. The design rationale of no separate matching sections between different accelerating sections maintains the current independence of beam behavior.

Takeda, H.; Billen, J.H.; Nath, S.

1997-10-01

197

SPALLATION NEUTRON SOURCE RING-DESIGN AND CONSTRUCTION SUMMARY.  

SciTech Connect

After six years, the delivery of components for the Spallation Neutron Source (SNS) accumulator ring (AR) and the transport lines was completed in Spring 2005. Designed to deliver 1.5 MW beam power (1.5 x 10{sup 14} protons of 1 GeV kinetic energy at a repetition rate of 60 Hz), stringent measures were implemented in the fabrication, test, and assembly to ensure the quality of the accelerator systems. This paper summarizes the design, R&D, and construction of the ring and transport systems.

WEI,J.

2005-05-16

198

Energy efficient engine core design and performance report. Report, January 1978-December 1982  

SciTech Connect

The Energy Efficient Engine (E3) is a NASA program to develop fuel saving technology for future large transport aircraft engines. Testing of the General Electric E3 core showed that the core component performance and core system performance necessary to meet the program goals can be achieved. The E3 core design and test results are described.

Stearns, E.M.

1982-12-01

199

NEUTRONIC REACTOR  

DOEpatents

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.

Wigner, E.P.

1958-04-22

200

DESIGN OPTIMIZATION AND THE PATH TOWARDS A 2 MW SPALLATION NEUTRON SOURCE.  

SciTech Connect

The Spallation Neutron Source (SNS) is designed to ultimately reach an average proton beam power of 2 MW for pulsed neutron production. The SNS physics groups analyze the machine performance within the hardware constraints, optimize the accelerator design, and establish the best path towards a 2 MW and higher spallation neutron source.

WEI,J.; BLASKIEWICZ,M.; CATALAN-LASHERAS,N.; DAVINO,D.; FEDOTOV,A.; LEE,Y.Y.; MALITSKY,N.; ET AL

2001-06-18

201

A detailed neutronics comparison of the university of Florida training reactor (UFTR) current HEU and proposed LEU cores  

SciTech Connect

For over 35 years, the UFTR highly-enriched core has been safely operated. As part of the Reduced Enrichment for Research and Test Reactors Program, the core is currently being converted to low-enriched uranium fuel. The analyses presented in this paper were performed to verify that, from a neutronic perspective, a proposed low-enriched core can be operated as safely and as effectively as the highly-enriched core. Detailed Monte Carlo criticality calculations are performed to determine: i) Excess reactivity for different core configurations, ii) Individual integral blade worth and shutdown margin, iii) Reactivity coefficients and kinetic parameters, and iv) Flux profiles and core six-factor formula parameters. (authors)

Dionne, B.; Haghighat, A.; Yi, C.; Smith, R.; Ghita, G.; Manalo, K.; Sjoden, G.; Huh, J.; Baciak, J.; Mock, T.; Wenner, M. [Dept. of Nuclear and Radiological Engineering, Univ. of Florida, Gainesville, FL (United States); Matos, J.; Stillman, J. [Reduced Enrichment for Research and Test Reactors Program, Argonne National Laboratory, Argonne, IL (United States)

2006-07-01

202

ORR core re-configuration measurements to increase the fast neutron flux in the Magnetic Fusion Energy (MFE) experiments  

SciTech Connect

A study has been made of the relative increases obtainable in the fast neutron flux in the Magnetic Fusion Energy (MFE) experiment positions by reconfiguring the current ORR core. The study was made at the request of the MFE program to examine the percentage increase possible in the current displacement per atom (dpa) rate (assumed proportional to the fast flux). The principle methods investigated to increase the fast flux consisted of reducing the current core size (number of fuel elements) to increase the core average power density and arrangement of the fuel elements in the reduced-size core to tilt the core power distribution towards the MFE positions. The study concluded that fast fluxes in the E-3 core position could be increased by approximately 15 to 20% over current values and in E-5 by approximately 45 to 55%.

Hobbs, R.W.; Stinnett, R.M.; Sims, T.M.

1985-06-01

203

Passive neutron design study for 200-L waste drums  

SciTech Connect

We have developed a passive neutron counter for the measurement of plutonium in 200-L drums of scrap and waste. The counter incorporates high efficiency for the multiplicity counting in addition to the traditional coincidence counting. The {sup 252}Cf add-a-source feature is used to provide an accurate assay over a wide range of waste matrix materials. The room background neutron rate is reduced by using 30 cm of external polyethylene shielding and the cosmic-ray background is reduced by statistical filtering techniques. Monte Carlo Code calculations were used to determine the optimum detector design, including the gas pressure, size, number, and placement of the {sup 3}He tubes in the moderator. Various moderators, including polyethylene, plastics, teflon, and graphite, were evaluated to obtain the maximum efficiency and minimum detectable mass of plutonium.

Menlove, H.O.; Beddingfield, D.B.; Pickrell, M.M. [and others

1997-09-01

204

FEM simulations in designing saturated iron core superconducting fault current limiters  

Microsoft Academic Search

Proper design of the iron cores is crucial for a saturated iron core superconducting fault current limiter. An optimized design requires guaranteeing sufficient magnetic saturation on the iron cores holding the AC coils, ensuring the efficiency of current limiting, minimizing the use of materials, as well as satisfying the safety and stability obligations. One of the key tasks in the

J. Z. Wang; W. Z. Gong; Y. Xin; J. Y. Zhang; X. M. Hu; Y. W. Sun; T. Q. Wu; B. Tian; Y. Wang; H. Hong; X. Y. Niu; Q. Li; L. F. Zhang

2009-01-01

205

Modeling & analysis of core debris recriticality during hypothetical severe accidents in the Advanced Neutron Source Reactor  

SciTech Connect

This paper discusses salient aspects of severe-accident-related recriticality modeling and analysis in the Advanced Neutron Source (ANS) reactor. The development of an analytical capability using the KEN05A-SCALE system is described including evaluation of suitable nuclear cross-section sets to account for the effects of system geometry, mixture temperature, material dispersion and other thermal-hydraulic conditions. Benchmarking and validation efforts conducted with KEN05-SCALE and other neutronic codes against critical experiment data are described. Potential deviations and biases resulting from use of the 16-group Hansen-Roach library are shown. A comprehensive test matrix of calculations to evaluate the threat of a criticality event in the ANS is described. Strong dependencies on geometry, material constituents, and thermal-hydraulic conditions are described. The introduction of designed mitigative features are described.

Kim, S.H.; Georgevich, V.; Simpson, D.B.; Slater, C.O.; Taleyarkhan, R.P.

1992-10-01

206

Electron-muon heat conduction in neutron star cores via the exchange of transverse plasmons  

SciTech Connect

We calculate the thermal conductivity of electrons and muons {kappa}{sub e{mu}} produced due to electromagnetic interactions of charged particles in neutron star cores and show that these interactions are dominated by the exchange of transverse plasmons (via the Landau damping of these plasmons in nonsuperconducting matter and via a specific plasma screening in the presence of proton superconductivity). For normal protons, the Landau damping strongly reduces {kappa}{sub e{mu}} and makes it temperature independent. Proton superconductivity suppresses the reduction and restores the Fermi-liquid behavior {kappa}{sub e{mu}}{proportional_to}T{sup -1}. Comparing with the thermal conductivity of neutrons {kappa}{sub n}, we obtain {kappa}{sub e{mu}} > or approx. {kappa}{sub n} for T > or approx. 2x10{sup 9} K in normal matter and for any T in superconducting matter with proton critical temperatures T{sub cp} > or approx. 3x10{sup 9} K. The results are described by simple analytic formulae.

Shternin, P. S.; Yakovlev, D. G. [Ioffe Physico-Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg (Russian Federation)

2007-05-15

207

Neutron transport with the method of characteristics for 3-D full core boiling water reactor applications  

NASA Astrophysics Data System (ADS)

The Numerical Nuclear Reactor (NNR) is a code suite that is being developed to provide high-fidelity multi-physics capability for the analysis of light water nuclear reactors. The focus of the work here is to extend the capability of the NNR by incorporation of the neutronics module, DeCART, for Boiling Water Reactor (BWR) applications. The DeCART code has been coupled to the NNR fluid mechanics and heat transfer module STAR-CD for light water reactor applications. The coupling has been accomplished via an interface program, which is responsible for mapping the STAR-CD and DeCART meshes, managing communication, and monitoring convergence. DeCART obtains the solution of the 3-D Boltzmann transport equation by performing a series of 2-D modular ray tracing-based method of characteristics problems that are coupled within the framework of 3-D coarse-mesh finite difference. The relatively complex geometry and increased axial heterogeneity found in BWRs are beyond the modeling capability of the original version of DeCART. In this work, DeCART is extended in three primary areas. First, the geometric capability is generalized by extending the modular ray tracing scheme and permitting an unstructured mesh in the global finite difference kernel. Second, numerical instabilities, which arose as a result of the severe axial heterogeneity found in BWR cores, have been resolved. Third, an advanced nodal method has been implemented to improve the accuracy of the axial flux distribution. In this semi-analytic nodal method, the analytic solution to the transverse-integrated neutron diffusion equation is obtained, where the nonhomogeneous neutron source was first approximated by a quartic polynomial. The successful completion of these three tasks has allowed the application of the coupled DeCART/STAR-CD code to practical BWR problems.

Thomas, Justin W.

208

Improved core design of the high temperature supercritical-pressure light water reactor  

Microsoft Academic Search

A new coolant flow scheme has been devised to raise the average coolant core outlet temperature of the High Temperature Supercritical-Pressure Light Water Reactor (SCLWR-H). A new equilibrium core is designed with this flow scheme to show the feasibility of an SCLWR-H core with an average coolant core outlet temperature of 530°C.In previous studies, the average coolant core outlet temperature

A. Yamaji; K. Kamei; Y. Oka; S. Koshizuka

2005-01-01

209

Design of the Core Support and Restraint Structures for FFTF and CRBRP.  

National Technical Information Service (NTIS)

This paper presents and compares the design and fabrication of the FFTF and CRBRP reactor structures which support and restrain the reactor core assemblies. The fabrication of the core support structure (CSS) for the FFTF reactor was completed October 197...

H. G. Sutton J. A. Rylatt

1977-01-01

210

Core design studies for a 1000 MW{sub th} advanced burner reactor.  

SciTech Connect

This paper describes the core design and performance characteristics of 1000 MW{sub th} Advanced Burner Reactor (ABR) core concepts with a wide range of TRU conversion ratio. Using ternary metal alloy and mixed oxide fuels, reference core designs of a medium TRU conversion ratio of {approx}0.7 were developed by trade-off between burnup reactivity loss and TRU conversion ratio. Based on these reference core concepts, TRU burner cores with low and high TRU conversion ratios were developed by changing the intra-assembly design parameters and core configurations. Reactor performance characteristics were evaluated in detail, including equilibrium cycle core performances, reactivity feedback coefficients, and shutdown margins. The results showed that by employing different assembly designs, a wide range of TRU conversion ratios from {approx}0.2 to break-even can be achieved within the same core without introducing significant performance and safety penalties.

Kim, T. K.; Yang, W. S.; Grandy, C.; Hill, R.; Nuclear Engineering Division

2009-04-01

211

Tokamak Fusion Core Experiment: design studies based on superconducting and hybrid toroidal field coils. Design overview  

SciTech Connect

This document is a design overview that describes the scoping studies and preconceptual design effort performed in FY 1983 on the Tokamak Fusion Core Experiment (TFCX) class of device. These studies focussed on devices with all-superconducting toroidal field (TF) coils and on devices with superconducting TF coils supplemented with copper TF coil inserts located in the bore of the TF coils in the shield region. Each class of device is designed to satisfy the mission of ignition and long pulse equilibrium burn. Typical design parameters are: major radius = 3.75 m, minor radius = 1.0 m, field on axis = 4.5 T, plasma current = 7.0 MA. These designs relay on lower hybrid (LHRH) current rampup and heating to ignition using ion cyclotron range of frequency (ICRF). A pumped limiter has been assumed for impurity control. The present document is a design overview; a more detailed design description is contained in a companion document.

Flanagan, C.A. (ed.)

1984-10-01

212

Design of a multi-element TEPC for neutron monitoring.  

PubMed

Tissue-equivalent proportional counters (TEPCs) have long been considered suitable candidate instruments for more accurate neutron monitors in nuclear power plants. It has also been recognised that the production of truly light-weight devices based on TEPCs requires further effort directed towards increasing their sensitivity and decreasing their physical size. This paper deals with the construction of a multi-element TEPC (METEPC) designed to have the sensitivity of a 12.7-cm (5-in.) diameter spherical TEPC, but with approximately one-tenth of its physical size. Construction of the METEPC is achieved by machining 61 elongated cylindrical cavities in a single block of A150 TE plastic. Comparative measurements carried out in neutron fields with mean energies ranging from 34 to 354 keV demonstrate that the METEPC constructed does match the sensitivity of a 5-in. spherical TEPC and that microdosimetric lineal energy spectra measured with both detectors have the same features and show the same changes with neutron radiation quality. PMID:21186210

Waker, A J; Aslam; Lori, J

2010-12-24

213

Nuclear design analysis of a multicavity gas core reactor system  

Microsoft Academic Search

The Innovative Nuclear Space Power Institute (INSPI) at the University of Florida has undertaken extensive research to establish the scientific feasibility and engineering validation of gaseous core reactor and energy conversion systems that have core power densities of a kilowatt per cubic centimeter and reactor masses of a kilogram per thermal megawatt for burstpower space applications. Gaseous core fission concepts

M. M. Panicker; E. T. Dugan; S. Anghaie

1987-01-01

214

Neutronics Assessment of Molten Salt Breeding Blanket Design Options  

SciTech Connect

Neutronics assessment has been performed for molten salt breeding blanket design options that can be utilized in fusion power plants. The concepts evaluated are a self-cooled Flinabe blanket with Be multiplier and dual-coolant blankets with He-cooled FW and structure. Three different molten salts were considered including the high melting point Flibe, a low melting point Flibe, and Flinabe. The same TBR can be achieved with a thinner self-cooled blanket compared to the dual-coolant blanket. A thicker Be zone is required in designs with Flinabe. The overall TBR will be {approx}1.07 based on 3-D calculations without breeding in the divertor region. Using Be yields higher blanket energy multiplication than obtainable with Pb. A modest amount of tritium is produced in the Be ({approx}3 kg) over the blanket lifetime of {approx}3 FPY. Using He gas in the dual-coolant blanket results in about a factor of 2 lower blanket shielding effectiveness. We show that it is possible to ensure that the shield is a lifetime component, the vacuum vessel is reweldable, and the magnets are adequately shielded. We conclude that molten salt blankets can be designed for fusion power plants with neutronics requirements such as adequate tritium breeding and shielding being satisfied.

Sawan, M.E. [University of Wisconsin-Madison (United States); Malang, S. [Fusion Nuclear Technology Consulting (United States); Wong, C.P.C. [General Atomics (United States); Youssef, M.Z. [University of California-Los Angeles (United States)

2005-04-15

215

Design and fabrication of embedded two elliptical cores hollow fiber  

NASA Astrophysics Data System (ADS)

We propose a novel embedded two elliptical cores fiber with a hollow air hole, and demonstrate the fabrication of the embedded two elliptical cores hollow fiber (EECHF). By using a suspended core-in-tube technique, the fibers are drawn from the preform utilizing a fiber drawing system with a pressure controller. The fiber have a 60?m diameter hollow air hole centrally, a 125?m diameter cladding, two 7.2?m /3.0?m (major axis/minor axis) elliptical cores, and a 3?m thickness silica cladding between core layer and air hole. The EECHF has a great potential for PMFs, high sensitivity in-fiber interferometers, poling fiber and Bio-sensor based on evanescent wave field. The fabrication technology is simple and versatile, and can be easily utilized to fabricate multi-core fiber with any desired aspect ratio elliptical core.

Tian, Fengjun; Yuan, Libo; Dai, Qian; Liu, Zhihai

2011-11-01

216

Designing for safety in the conceptual design of the Advanced Neutron Source  

SciTech Connect

The Advanced Neutron Source is a major new research facility proposed by the Department of Energy for construction over the next six years. The unique set of nuclear safety features selected to give the recently completed conceptual design a high degree of safety are identified and discussed.

Harrington, R.M.; West, C.D.

1993-06-01

217

Design and Applications of a {sup 252}Cf Cold Neutron Source  

SciTech Connect

The goal was to design a source of cold neutrons from such sources as {sup 252}Cf, {sup 241}Am-Be, {sup 244}Cm-Be, or {sup 124}Sb-Be and to find the limitations when such a source is applied to neutron activation analysis. Here, cold neutrons are neutrons with a kinetic energy < 0.01 eV. The initial kinetic energy of most of the neutrons produced from the decay of the {sup 252}Cf nucleus lies in the range from 0.5 to 10 MeV, so moderation is necessary to produce a significant quantity of cold neutrons from these initial neutrons. The same is true for the other three neutron sources. The general design that was selected for the cold neutron source has two moderation regions, and the geometry was restricted to cylindrical symmetry with the sample region along the cylindrical axis. The moderation regions may have different temperatures and may contain different moderating materials. The design tasks are then to find the optimum geometry, moderating materials, and moderating temperatures. A cold neutron flux in the sample region of 2.7 x 10 {sup -3} cold neutrons per source neutron is obtainable in a {sup 252}Cf cold neutron source that has polyethylene as the cold and thermal moderator or with trimethylbenzene as the cold moderator and polyethylene as the thermal moderator. The neutron fluxes obtained are probably within 10{percent} of the fluxes that would be obtained in an actual cold neutron source that is based on the model used. This flux of cold neutrons is adequate for sensitive prompt and delayed neutron activation analysis measurements. The results show that a useful flux of cold neutrons can be obtained from small amounts of {sup 252}Cf, {sup 241}Am, {sup 244}Cm, or {sup 124}Sb.

Elijah Johnson; Larry Robinson; Li Zhao

2000-11-12

218

Design of the Mechanical Parts for the Neutron Guide System at HANARO  

NASA Astrophysics Data System (ADS)

The research reactor HANARO (High-flux Advanced Neutron Application ReactOr) in Korea will be equipped with a neutron guide system, in order to transport cold neutrons from the neutron source to the neutron scattering instruments in the neutron guide hall near the reactor building. The neutron guide system of HANARO consists of the in-pile plug assembly with in-pile guides, the primary shutter with in-shutter guides, the neutron guides in the guide shielding room with dedicated secondary shutters, and the neutron guides connected to the instruments in the neutron guide hall. Functions of the in-pile plug assembly are to shield the reactor environment from nuclear radiation and to support the neutron guides and maintain them precisely oriented. The primary shutter is a mechanical structure to be installed just after the in-pile plug assembly, which stops neutron flux on demand. This paper describes the design of the in-pile assembly and the primary shutter for the neutron guide system at HANARO. The design of the guide shielding assembly for the primary shutter and the neutron guides is also presented.

Shin, J. W.; Cho, Y. G.; Cho, S. J.; Ryu, J. S.

2008-03-01

219

Design of the Mechanical Parts for the Neutron Guide System at HANARO  

SciTech Connect

The research reactor HANARO (High-flux Advanced Neutron Application ReactOr) in Korea will be equipped with a neutron guide system, in order to transport cold neutrons from the neutron source to the neutron scattering instruments in the neutron guide hall near the reactor building. The neutron guide system of HANARO consists of the in-pile plug assembly with in-pile guides, the primary shutter with in-shutter guides, the neutron guides in the guide shielding room with dedicated secondary shutters, and the neutron guides connected to the instruments in the neutron guide hall. Functions of the in-pile plug assembly are to shield the reactor environment from nuclear radiation and to support the neutron guides and maintain them precisely oriented. The primary shutter is a mechanical structure to be installed just after the in-pile plug assembly, which stops neutron flux on demand. This paper describes the design of the in-pile assembly and the primary shutter for the neutron guide system at HANARO. The design of the guide shielding assembly for the primary shutter and the neutron guides is also presented.

Shin, J. W.; Cho, Y. G.; Cho, S. J.; Ryu, J. S. [Korea Atomic Energy Research Institute, 1045 Daedeok-daero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of)

2008-03-17

220

Design of a neutron radiography facility at the spallation source SINQ  

Microsoft Academic Search

The continuous-current neutron source SINQ is presently under construction at the Paul Scherrer Institute (Switzerland). First operational tests are scheduled to begin during the last quarter of 1996. SINQ will provide both thermal and cold neutron beams for a wide variety of experimental facilities.A neutron radiography facility has been designed and is under construction. It consists of the first collimation

Eberhard Lehmann; Helena Pleinert; Luzius Wiezel

1996-01-01

221

Design of a laboratory for experiments with a pulsed neutron source  

Microsoft Academic Search

We present the results of a neutron shielding design and optimisation study performed to reduce the exposure to radiological doses arising from a 14 MeV pulsed neutron generator (PNG) having a maximum emission strength of 2.0 × 108 neutrons s-1. The source was intended to be used in a new irradiation facility for the realisation of an experiment on acoustical

G. Memoli; J. P. M. Trusler; A. K. Ziver

2009-01-01

222

Design of a laboratory for experiments with a pulsed neutron source  

Microsoft Academic Search

We present the results of a neutron shielding design and optimisation study performed to reduce the exposure to radiological doses arising from a 14 MeV pulsed neutron generator (PNG) having a maximum emission strength of 2.0 × 108 neutrons s?1. The source was intended to be used in a new irradiation facility for the realisation of an experiment on acoustical

G Memoli; J P M Trusler; A K Ziver

2009-01-01

223

Design study of a medical proton linac for neutron therapy  

SciTech Connect

This paper describes a design study which establishes the physical parameters of the low energy beam transport, radiofrequency quadrupole, and linac, using computer programs available at Fermilab. Beam dynamics studies verify that the desired beam parameters can be achieved. The machine described here meets the aforementioned requirements and can be built using existing technology. Also discussed are other technically feasible options which could be attractive to clinicians, though they would complicate the design of the machine and increase construction costs. One of these options would allow the machine to deliver 2.3 MeV protons to produce epithermal neutrons for treating brain tumors. A second option would provide 15 MeV protons for isotope production. 21 refs., 33 figs.

Machida, S.; Raparia, D.

1988-08-26

224

Design study of a medical linac for neutron therapy  

NASA Astrophysics Data System (ADS)

A 66 MeV proton linac for neutron therapy has been studied and conceptual designs for low energy beam transport (LEBT), a radio-frequency quadrupole (RFQ) and a drift tube linac (DTL) have been achieved. The machine is compact and simple enough to be operated in hospitals. The LEBT consists of two Einzel lenses and is 22 cm long. The 425 MHz RFQ is designed for 50 mA peak current at 60 Hz and is 1 m long. The 18-m-long DTL has the same frequency as the RFQ and uses permanent quadrupole magnets. Beam dynamics are very important for this compact and high-brightness machine. This paper emphasizes our investigation of the beam dynamics.

Raparia, D.; Machida, S.

1989-04-01

225

Design study of a medical linac for neutron therapy  

SciTech Connect

A 66 MeV proton linac for neutron therapy has been studied and conceptual designs for low energy beam transport (LEBT), a radio frequency quadrupole (RFQ), and a drift tube linac (DTL) have been achieved. The machine is compact and simple enough to be operated in hospitals. The LEBT consists of two Einzel lenses and is 22 cm long. The 425 MHz RFQ is designed for 50 milliamps peak current at 60 Hz and is one meter long. The 18-meter-long DTL has the same frequency as the RFQ and uses permanent quadrupole magnets. Beam dynamics are very important for this compact and high-brightness machine. This paper emphasizes our investigation of the beam dynamics. 5 refs., 4 figs., 3 tabs.

Raparia, D.; Machida, S.

1988-01-01

226

CORTAP: a coupled neutron kinetics-heat transfer digital computer program for the dynamic simulation of the high temperature gas cooled reactor core  

Microsoft Academic Search

CORTAP (Core Transient Analysis Program) was developed to predict the dynamic behavior of the High Temperature Gas Cooled Reactor (HTGR) core under normal operational transients and postulated accident conditions. CORTAP is used both as a stand-alone component simulation and as part of the HTGR nuclear steam supply (NSS) system simulation code ORTAP. The core thermal neutronic response is determined by

1977-01-01

227

Simulation of in-core neutron noise measurements for axial void profile reconstruction in boiling water reactors  

SciTech Connect

A possibility to reconstruct the axial void profile from the simulated in-core neutron noise which is caused by density fluctuations in a Boiling Water Reactor (BWR) heated channel is considered. For this purpose, a self-contained model of the two-phase flow regime is constructed which has quantitatively and qualitatively similar properties to those observed in real BWRs. The model is subsequently used to simulate the signals of neutron detectors induced by the corresponding perturbations in the flow density. The bubbles are generated randomly in both space and time using Monte-Carlo techniques. The axial distribution of the bubble production is chosen such that the mean axial void fraction and void velocity follow the actual values of BWRs. The induced neutron noise signals are calculated and then processed by the standard signal analysis methods such as Auto-Power Spectral Density (APSD) and Cross-Power Spectral Density (CPSD). Two methods for axial void and velocity profiles reconstruction are discussed: the first one is based on the change of the break frequency of the neutron auto-power spectrum with axial core elevation, while the second refers to the estimation of transit times of propagating steam fluctuations between different axial detector positions. This paper summarizes the principles of the model and presents a numerical testing of the qualitative applicability to estimate the required parameters for the reconstruction of the void fraction profile from the neutron noise measurements. (authors)

Dykin, V.; Pazsit, I. [Chalmers Univ. of Technology, Div. of Nuclear Engineering, Dept. of Applied Physics, SE-412 96 Gothenburg (Sweden)

2012-07-01

228

Design Study of Block-Pin Type Fuel for Experimental VHTR (EVHTR) Core.  

National Technical Information Service (NTIS)

In MARK-II core designs of EVHTR, the minimum Reynolds number in the core is about 2600 and is not satisfactory for the thermal performance. Different cores and fuels have been investigated to improve the thermal characteristics. The following were reveal...

T. Ikushima M. Hirano K. Suzuki T. Kurashige S. Kuroi

1976-01-01

229

Mechanical design considerations of a spherical torus volumetric neutron source  

SciTech Connect

The mechanical design of a spherical torus based volumetric neutron source (ST VNS) is being studied under the support of a DOE-SBIR funding. A device capable of staged operation from a neutron wall loading of 0.5-5.0 MW/m(2) has been scoped out, as the physics and engineering design assumptions are raised from modest to aggressive levels. Margins in the design are ensured since operation of the VNS will be adequate st a wall loading of 2 MW/m(2). The device has a naturally diverted plasma with major radius of 1.07 m, a minor radius of 0.77 m for an aspect ratio of 1.4, an elongation of 3 and triangularity of 0,6. In the neutral beam driven version, the plasma current is 11.1 MA and the toroidal field at the plasma major radius is 2.13 T, The baseline fusion power is 151 MW giving an average neutron wall loading of 2 MV/m(2) on the outboard side over an accessible area of over 15 m(2) for blanket testing. The device utilizes a normal Cu conducting bell jar as the return leg of the toroidal field current, a concept developed at the Oak Ridge National Laboratory. The current is carried by an unshielded single-turn center post (CP) made of dispersion strengthened Cu which is cooled by water in a single pass from top to bottom. A special sliding electrical interface between the CP and the bell jar is provided on the upper end to allow for differential expansion and to isolate the CP from tensile and torsional forces from the bell jar. The ohmic heating in the CP is 153 MW at the start of operation and increases to 178 MW after 3 full power years of operation. Over this period the maximum Cu temperature does not exceed 160 C. This report primarily deals with the design of the CP, one of the most challenging Issues of a low aspect ratio spherical torus. Maintenance approaches for the Or and the divertor assemblies have been determined and are addressed in the paper.

Sviatoslavky, I. N. [University of Wisconsin, Madison; Peng, Yueng Kay Martin [ORNL

1998-01-01

230

Modern sandwich core materials offer new attractive design possibilities  

Microsoft Academic Search

Activities in trying to make the airplane interiors more attractive to passengers increase the demand for complex, three-dimensional sandwich structural parts. The realization of three-dimensional contours often failed in the past, due to a lack of process ability or the enormous production costs caused by the processing of conventional phenolic cores. The new structural foam cores based on thermoplastic polytherimide

Bruno Imhof

1997-01-01

231

Core excitation contributions to the breakup of the one-neutron halo nucleus {sup 11}Be on a proton  

SciTech Connect

The effect of the core excitation in the breakup of a one-neutron halo nucleus is studied within two different reaction formalisms, namely, the core excited model and the single-scattering approximation of the three-body Faddeev-Alt-Grassberger-Sandhas equations with target-core potential allowing for the core excitation. As an example, we consider the breakup of {sup 11}Be on a proton target at 63.7 MeV/nucleon incident energy and calculate the semi-inclusive cross section in the excitation energy interval E{sub x}=3.0-5.5 MeV (E{sub rel}=2.5-5 MeV) containing the 3/2{sup +} resonance with dominant contribution of the {sup 10}Be(2{sup +}) core excited state. The effect of the core excitation to the breakup cross section integrated around this resonance is found to be very significant. Moreover, when resonant and nonresonant contributions are added, the resulting semi-inclusive cross section is in reasonable agreement with the existing data, demonstrating the relevance of the core excitation mechanism for this observable. The present calculations also show the importance of incorporating the energy dependence of the core-target transition operators in the reaction formalism.

Crespo, R. [Centro de Fisica Nuclear, Universidade de Lisboa, Av. Prof. Gama Pinto 2, PT-1649-003 Lisboa (Portugal); Departamento de Fisica, Instituto Superior Tecnico, Taguspark, Av. Prof. Cavaco Silva, Taguspark, PT-2780-990 Porto Salvo, Oeiras (Portugal); Deltuva, A. [Centro de Fisica Nuclear, Universidade de Lisboa, Av. Prof. Gama Pinto 2, PT-1649-003 Lisboa (Portugal); Moro, A. M. [Departamento de Fisica Atomica, Molecular e Nuclear, Universidad Seville, Universidad de Sevilla, Apartado 1065, ES-41080 Sevilla (Spain)

2011-04-15

232

Preliminary detector design ST862-prototype neutron detector.  

National Technical Information Service (NTIS)

The detection of fast neutrons has been accomplished with commercially available liquid scintillators in detectors. Liquid scintillators discriminate fast neutrons from gamma radiation by discarding pulses with short decay constants. However, pulse-timing...

S. D. Miller J. D. Affinito D. R. Sisk

1993-01-01

233

A new paradigm for local-global coupling in whole-core neutron transport.  

SciTech Connect

A new paradigm that increases the efficiency of whole-core neutron transport calculations without lattice homogenization is introduced. Quasi-reflected interface conditions are formulated to partially decouple periodic lattice effects from global flux gradients. The starting point is the finite subelement form of the variational nodal code VARIANT that eliminates fuel-coolant homogenization through the use of heterogeneous nodes. The interface spherical harmonics expansions that couple pin-cell-sized nodes are divided into low-order and high-order terms, and reflected interface conditions are applied to the high-order terms. Combined with an integral transport method within the node, the new approach dramatically reduces both the formation time and the dimensions of the nodal response matrices and leads to sharply reduced memory requirements and computational time. The method is applied to the two-dimensional C5G7 problem, an Organisation for Economic Co-operation and Development/Nuclear Energy Agency pressurized water reactor benchmark containing mixed oxide (MOX) and UO{sub 2} fuel assemblies, as well as to a three-dimensional MOX fuel assembly. Results indicate the new approach results in very little loss of accuracy relative to the corresponding full spherical harmonics expansions while reducing computational times by well over an order of magnitude.

Lewis, E.; Smith, M.; Palmiotti, G,; Nuclear Engineering Division; Northwestern Univ.; INL

2009-01-01

234

Flavor Evolution of the Neutronization Neutrino Burst From an O-Ne-Mg Core-Collapse Supernova  

SciTech Connect

We present results of 3-neutrino flavor evolution simulations for the neutronization burst from an O-Ne-Mg core-collapse supernova. We find that nonlinear neutrino self-coupling engineers a single spectral feature of stepwise conversion in the inverted neutrino mass hierarchy case and in the normal mass hierarchy case, a superposition of two such features corresponding to the vacuum neutrino mass-squared differences associated with solar and atmospheric neutrino oscillations. These neutrino spectral features offer a unique potential probe of the conditions in the supernova environment and may allow us to distinguish between O-Ne-Mg and Fe core-collapse supernovae.

Duan Huaiyu [Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195 (United States); Fuller, George M. [Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States); Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195 (United States); Carlson, J. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Qian Yongzhong [School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

2008-01-18

235

Fresh-Core Reload of the Neutron Radiography (NRAD) Reactor with Uranium(20)-Erbium-Zirconium-Hydride Fuel  

SciTech Connect

The neutron radiography (NRAD) reactor is a 250 kW TRIGA® (Training, Research, Isotopes, General Atomics) Mark II , tank-type research reactor currently located in the basement, below the main hot cell, of the Hot Fuel Examination Facility (HFEF) at the Idaho National Laboratory (INL). It is equipped with two beam tubes with separate radiography stations for the performance of neutron radiography irradiation on small test components. The 60-fuel-element operational core configuration of the NRAD LEU TRIGA reactor has been evaluated as an acceptable benchmark experiment. The initial critical configuration developed during the fuel loading process, which contains only 56 fuel elements, has not been evaluated as it is very similar to the evaluated core configuration. The benchmark eigenvalue is 1.0012 ± 0.0029. Calculated eigenvalues differ significantly (~±1%) from the benchmark eigenvalue and have demonstrated sensitivity to the thermal scattering treatment of hydrogen in the U-Er-Zr-H fuel.

John D. Bess; Thomas L. Maddock; Margaret A. Marshall; Leland M. Montierth

2011-03-01

236

Spallation neutron source cryomodule heat loads and thermal design  

SciTech Connect

When complete, the Spallation Neutron Source (SNS) will provide a 1 GeV, 2 MW beam for experiments. One portion of the machine's linac consists of over 80 Superconducting Radio Frequency (SRF) 805 MHz cavities housed in a minimum of 23 cryomodules operating at a saturation temperature of 2.1 K. Minimization of the total heat load is critical to machine performance and for efficient operation of the system. The total heat load of the cryomodules consists of the fixed static load and the dynamic load, which is proportional to the cavity performance. The helium refrigerator supports mainly the cryomodule loads and to a lesser extent the distribution system loads. The estimated heat loads and calculated thermal performance are discussed along with two unique features of this design: the helium heat exchanger housed in the cryomodule return end can and the helium gas cooled fundamental power coupler.

E. F. Daly; V. Ganni; C. H. Rode; W. J. Schneider; K. M. Wilson; M. A. Wiseman

2002-05-10

237

Conceptual design of air-core superconducting power transformer for cable transmission system  

Microsoft Academic Search

The air-core superconducting transformer, which has a large magnetizing current, has been proposed as a power transformer that has the function as a shunt reactor. In this paper, the basic design procedure for the air-core superconducting transformer is presented. By using this procedure, 500\\/â(3kV)--66\\/â(3kV)--300 MVA single phase air-core transformer is designed for a model cable transmission system. Then, the performance

Hiroshi Yamaguchi; Yukihiko Sato; Teruo Kataoka

1996-01-01

238

Direct access test scheme-design of block and core cells for embedded ASICs  

Microsoft Academic Search

Intel requires the use of a direct-access test scheme in embedded-core or block-based ASIC (application-specific integrated-circuit) designs. This scheme provides for separate testing of individual block or core cells using proven test vectors. The authors discuss the design modifications for block cells with low pin counts, user application blocks, and large cores with high pin counts. The implementation and verification

V. Immaneni; S. Raman

1990-01-01

239

Current directions in core-shell nanoparticle design  

Microsoft Academic Search

Ten years ago I wrote a review about the important field of core-shell nanoparticles, focussing mainly on our own work about tracer systems, and briefly addressing polymer-coated nanoparticles as fillers for homogeneous polymer-colloid composites. Since then, the potential use of core-shell nanoparticles as multifunctional sensors or potential smart drug-delivery vehicles in biology and medicine has gained more and more importance,

Wolfgang Schärtl

2010-01-01

240

Performance of truss panels with kagome cores and design of a high authority shape morphing structure  

Microsoft Academic Search

This dissertation includes two parts: First, the performance of a light weight truss panels with Kagome cores; Second, design of a high authority morphing structure for hinging and twisting. The performance characteristics of a truss core sandwich panel design based on the 3D Kagome are measured and compared with earlier numerical simulations and the consistency is demonstrated. Panels are fabricated

Ju Wang

2005-01-01

241

Design of an Aluminum Proton Beam Window for the Spallation Neutron Source  

SciTech Connect

An aluminum proton beam window design is being considered at the Spallation Neutron Source primarily to increase the lifetime of the window, with secondary advantages of higher beam transport efficiency and lower activation. The window separates the core vessel, the location of the mercury target, from the vacuum of the accelerator, while withstanding the pass through of a proton beam of up to 2 MW with 1.0 GeV proton energy. The current aluminum alloy being investigated for the window material is 6061-T651 due to its combination of high strength, high thermal conductivity, and good resistance to aqueous corrosion, as well as demonstrated dependability in previous high-radiation environments. The window design will feature a thin plate with closely spaced cross drilled cooling holes. An analytical approach was used to optimize the dimensions of the window before finite element analysis was used to simulate temperature profiles and stress fields resulting from thermal and static pressure loading. The resulting maximum temperature of 60 C and Von Mises stress of 71 MPa are very low compared to allowables for Al 6061-T651. A significant challenge in designing an aluminum proton beam window for SNS is integrating the window with the current 316L SS shield blocks. Explosion bonding was chosen as a joining technique because of the large bonding area required. A test program has commenced to prove explosion bonding can produce a robust vacuum joint. Pending successful explosion bond testing, the aluminum proton beam window design will be proven acceptable for service in the Spallation Neutron Source.

Janney, Jim G [ORNL; McClintock, David A [ORNL

2012-01-01

242

Modeling and analysis framework for core damage propagation during flow-blockage-initiated accidents in the Advanced Neutron Source reactor at Oak Ridge National Laboratory.  

National Technical Information Service (NTIS)

This paper describes modeling and analysis to evaluate the extent of core damage during flow blockage events in the Advanced Neutron Source (ANS) reactor planned to be built at ORNL. Damage propagation is postulated to occur from thermal conduction betwee...

S. H. Kim R. P. Taleyarkhan S. Navarro-Valenti V. Georgevich

1995-01-01

243

Results of a Neutronic Simulation of HTR-Proteus Core 4.2 using PEBBED and other INL Reactor Physics Tools: FY-09 Report  

SciTech Connect

The Idaho National Laboratory’s deterministic neutronics analysis codes and methods were applied to the computation of the core multiplication factor of the HTR-Proteus pebble bed reactor critical facility. A combination of unit cell calculations (COMBINE-PEBDAN), 1-D discrete ordinates transport (SCAMP), and nodal diffusion calculations (PEBBED) were employed to yield keff and flux profiles. Preliminary results indicate that these tools, as currently configured and used, do not yield satisfactory estimates of keff. If control rods are not modeled, these methods can deliver much better agreement with experimental core eigenvalues which suggests that development efforts should focus on modeling control rod and other absorber regions. Under some assumptions and in 1D subcore analyses, diffusion theory agrees well with transport. This suggests that developments in specific areas can produce a viable core simulation approach. Some corrections have been identified and can be further developed, specifically: treatment of the upper void region, treatment of inter-pebble streaming, and explicit (multiscale) transport modeling of TRISO fuel particles as a first step in cross section generation. Until corrections are made that yield better agreement with experiment, conclusions from core design and burnup analyses should be regarded as qualitative and not benchmark quality.

Hans D. Gougar

2009-08-01

244

Reducing Duration of Refueling Outage by Optimizing Core Design and Shuffling Sequence  

SciTech Connect

Reducing the duration of refueling outage is possible by optimizing the core design and the shuffling sequence. For both options software tools have been developed that have been applied to the three most recent cycles of the Borssele plant in the Netherlands. Applicability of the shuffling sequence optimization to boiling water reactors has been demonstrated by a comparison to a recent shuffle plan used in the Hatch plant located in the United States. Their uses have shown that both core design and shuffling sequence optimization can be exploited to reduce the time needed for reloading a core with an in-core shuffling scheme. Ex-core shuffling schemes for pressurized water reactors can still have substantial benefit from a core design using a minimized number of insert shuffles.

Wakker, P.H.; Verhagen, F.C.M.; Bloois, J.T. van; Sutton, W.R. III

2005-07-15

245

Investigation of primary cooling water chemistry following the partial meltdown of Pu–Be neutron source in Tehran Research Reactor Core (TRR)  

Microsoft Academic Search

Effect of Pu–Be neutron source meltdown in core on reactor water chemistry was main aim of this study. Leaving the neutron source in the core after reactor power exceeds a few hundred Watts was the main reason for its partial meltdown.Water chemistry of primary cooling before, during and after of above incident was compared. Activity of some radio-nuclides such as

Reza Gholizadeh Aghoyeh; Hossein Khalafi

2011-01-01

246

A Methodology for Selecting High Thermal-Hydraulic Performance Fuel Configurations for Tightly Packed Epithermal Core Designs  

SciTech Connect

Cylindrical fuel pins with wires are the design of choice for tightly packed fuel arrays. However, it is important to investigate novel fuel configurations in order to increase the thermal margins. Hence, new fuel designs have been studied for the epithermal option of the light water-cooled IRIS core. These designs are also of potential use in other tightly packed, epithermal advanced core designs.First, design equations have been used to determine number, height, and size of the principal features (clad, gap, fuel cross-sectional area) of the novel fuel configurations under investigation. Then, performance indices have been introduced to relate fuel geometrical characteristics to selected thermal-hydraulic parameters, such as pressure drop, critical heat flux (CHF), fuel centerline temperature, and clad surface temperature and stress distribution. Finally, variously shaped fuel configurations, including cylindrical, triangular, square, and hexagonal, have been ranked according to the performance indicators.The hexagonal fuel pins, both twisted and straight, proved to be good solutions for the epithermal tight core of the light water-cooled IRIS reactor, with performances comparable to those of the cylindrical fuel with wires. In particular, for water-to-fuel ratios {approx}0.33, the twisted hexagonal shape is the preferable design with a reduction of the total pressure drop by 16% and an increase of the CHF margin by 200%, compared to the traditional cylindrical pins with grids. Furthermore, the straight hexagonal shape allows flatter subchannel velocity profiles, wall shear stress, and wall temperature distributions. However, geometric constraints unfortunately do not allow application of the twisted hexagonal shape for smaller water-to-fuel ratios, which is a design regime of more favorable epithermal neutronics performance. In this regime, the cylindrical pins with wires are the solution of choice.

Romano, Antonino; Todreas, Neil E. [Massachusetts Institute of Technology (United States)

2002-07-15

247

Current directions in core-shell nanoparticle design  

NASA Astrophysics Data System (ADS)

Ten years ago I wrote a review about the important field of core-shell nanoparticles, focussing mainly on our own work about tracer systems, and briefly addressing polymer-coated nanoparticles as fillers for homogeneous polymer-colloid composites. Since then, the potential use of core-shell nanoparticles as multifunctional sensors or potential smart drug-delivery vehicles in biology and medicine has gained more and more importance, affording special types of multi-functionalized and bio-compatible nanoparticles. In this new review article, I try to address the most important developments during the last ten years. This overview is mainly based on frequently cited and more specialized recent review articles from leaders in their respective field. We will consider a variety of nanoscopic core-shell architectures from highly fluorescent nanoparticles (NPs), protected magnetic NPs, multifunctional NPs, thermoresponsive NPs and biocompatible systems to, finally, smart drug-delivery systems.Ten years ago I wrote a review about the important field of core-shell nanoparticles, focussing mainly on our own work about tracer systems, and briefly addressing polymer-coated nanoparticles as fillers for homogeneous polymer-colloid composites. Since then, the potential use of core-shell nanoparticles as multifunctional sensors or potential smart drug-delivery vehicles in biology and medicine has gained more and more importance, affording special types of multi-functionalized and bio-compatible nanoparticles. In this new review article, I try to address the most important developments during the last ten years. This overview is mainly based on frequently cited and more specialized recent review articles from leaders in their respective field. We will consider a variety of nanoscopic core-shell architectures from highly fluorescent nanoparticles (NPs), protected magnetic NPs, multifunctional NPs, thermoresponsive NPs and biocompatible systems to, finally, smart drug-delivery systems. Dedicated to Professor Manfred Schmidt on the occasion of his 60th birthday

Schärtl, Wolfgang

2010-06-01

248

Monte Carlo Calculation of Core Reactivity and Fluxes for the Development of the BNCT Neutron Source at the Kyiv Research Reactor  

NASA Astrophysics Data System (ADS)

The presented results show our consecutive steps in developing a neutron source with parameters required by Boron Neutron Capture Therapy (BNCT) at the Kyiv Research Reactor (KRR). The main goal of this work was to analyze the influence of installation of different types of uranium converters close to the reactor core on neutron beam characteristics and on level of reactor safety. The general Monte Carlo radiation transport code MCNP, version 4B, has been used for these calculations.

Gritzay, Olena; Kalchenko, Oleksandr; Klimova, Nataliya; Razbudey, Volodymyr; Sanzhur, Andriy; Binney, Stephen

2005-05-01

249

Monte Carlo Calculation of Core Reactivity and Fluxes for the Development of the BNCT Neutron Source at the Kyiv Research Reactor  

SciTech Connect

The presented results show our consecutive steps in developing a neutron source with parameters required by Boron Neutron Capture Therapy (BNCT) at the Kyiv Research Reactor (KRR). The main goal of this work was to analyze the influence of installation of different types of uranium converters close to the reactor core on neutron beam characteristics and on level of reactor safety. The general Monte Carlo radiation transport code MCNP, version 4B, has been used for these calculations.

Gritzay, Olena; Kalchenko, Oleksandr; Klimova, Nataliya; Razbudey, Volodymyr; Sanzhur, Andriy [Institute for Nuclear Research, Prospekt Nauky 47, Kyiv, 03680 (Ukraine); Binney, Stephen [Oregon State University, Corvallis, OR 97331-5902 (United States)

2005-05-24

250

Monte Carlo design for a new neutron collimator at the ENEA Casaccia TRIGA reactor.  

PubMed

The TRIGA RC-1 1MW reactor operating at ENEA Casaccia Center is currently being developed as a second neutron imaging facility that shall be devoted to computed tomography as well as neutron tomography. In order to reduce the gamma-ray content in the neutron beam, the reactor tangential piercing channel was selected. A set of Monte Carlo simulation was used to design the neutron collimator, to determine the preliminary choice of the materials to be employed in the collimator design. PMID:15246415

Burgio, N; Rosa, R

2004-10-01

251

Core Curriculum Analysis: A Tool for Educational Design  

ERIC Educational Resources Information Center

This paper examines the outcome of a dimensional core curriculum analysis. The analysis process was an integral part of an educational development project, which aimed to compact and clarify the curricula of the degree programmes. The task was also in line with the harmonising of the degree structures as part of the Bologna process within higher…

Levander, Lena M.; Mikkola, Minna

2009-01-01

252

Ferrite core loss for power magnetic components design  

Microsoft Academic Search

A practical method is presented for computing high-frequency ferrite core losses in the magnetic component for arbitrary voltage waveforms. The model presented requires only a few material parameters as input. To calculate ferrite hysteresis losses, a model based on empirical rules is employed. For high-frequency eddy current losses, a built phenomenon is assumed. It is demonstrated that the hysteresis model

Waseem Roshen

1991-01-01

253

Deterministic adjoint transport applications for He3 neutron detector design  

Microsoft Academic Search

This work focuses on the determination of predicted neutron detector response accomplished using neutron importance derived from an adjoint discrete ordinates (SN) transport calculation. A hypothetical detector apparatus, intended to detect fast neutrons, was modeled using He-3 tubes with graphite moderation using the PENTRAN™ 3-D multi-group discrete ordinates parallel transport code system. The detector geometry was modeled using z-axis symmetry

G. E Sjoden

2002-01-01

254

Design and simulation of neutron radiography system based on 241Am-Be source  

NASA Astrophysics Data System (ADS)

Neutron imaging is extended rapidly as a means of non-destructive testing (NDT) of materials. Various effective parameters on the image quality are needed to be studied for neutron radiography system with good resolution. In the present study a portable system of neutron radiography has been designed using 241Am-Be neutron source. The effective collimator parameters were calculated to obtain relatively pure, collimated and uniform neutron beam. All simulations were carried out in two stages using MCNPX Monte Carlo code. In the first stage, different collimator configurations were investigated and the appropriate design was selected based on maximum intensity and uniformity of neutron flux at the image plane in the outlet of collimator. Then, the overall system including source, collimator and sample was simulated for achieving radiographic images of standard samples. Normalized thermal neutron fluence of 2.61×10-5 cm-2 per source particle with n/? ratio of 1.92×105 cm-2 ?Sv-1 could be obtained at beam port of the designed collimator. Quality of images was assessed for two standard samples, using radiographic imaging capability in MCNPX. The collimated neutron beam in the designed system could be useful in a transportable exposure module for neutron radiography application.

Jafari, H.; Feghhi, S. A. H.

2012-05-01

255

Stress analysis, code evaluation, and design modification of a plate resulting from seismic loads and hypothetical core disruptive accident loads  

SciTech Connect

This study addresses the structural analysis and evaluation of a design modification for a plate in the Fast Flux Test Facility heat temperature control system. The plate being considered is near a fuel transfer port system. The plate is flat and is supported by six long studs, five of which are along one side of the plate. Their location makes the plate act as a cantilever.The plate itself provides support to three vertical neutron shields on its free edges. During service, a uranium shield ring under the fuel transfer port nozzle oxidized and expanded. To prevent this expansion from causing damage to the surrounding components, this ring was removed and replaced with lead blocks. Approximately one-fourth of the lead blocks rest on a free edge of the plate. This new configuration of the plate required updated seismic and hypothetical core disruptive accident analyses. Seismic and hypothetical core disruptive accident analyses were performed and checked against the requirements of the American Society of Mechanical Engineers Code. The result showed that the design of the existing plate supports (the six studs) was not adequate for the added weight of the lead blocks. The design was modified to restrain the lead blocks. When the final design with modified boundary conditions was reevaluated, the stress results satisfied the Code requirements.

Rezvani, M.A.; Ziada, H.H.

1992-01-01

256

Computational Benchmark Calculations Relevant to the Neutronic Design of the Spallation Neutron Source (SNS)  

Microsoft Academic Search

The Spallation Neutron Source (SNS) will provide an intense source of low-energy neutrons for experimental use. The low-energy neutrons are produced by the interaction of a high-energy (1.0 GeV) proton beam on a mercury (Hg) target and slowed down in liquid hydrogen or light water moderators. Computer codes and computational techniques are being benchmarked against relevant experimental data to validate

F. X. Gallmeier; D. C. Glasgow; E. A. Jerde; J. O. Johnson; J. J. Yugo

1999-01-01

257

The Effect of Quantized Magnetic Flux Lines on the Dynamics of Superfluid Neutron Star Cores  

Microsoft Academic Search

We investigate dynamical coupling timescales of a neutron star's superfluid\\u000acore, taking into account the interactions of quantized neutron vortices with\\u000aquantized flux lines of the proton superconductor in addition to the previously\\u000aconsidered scattering of the charged components against the spontaneous\\u000amagnetization of the neutron vortex line. We compare the cases where vortex\\u000amotion is constrained in different ways

T. Sidery; M. A. Alpar

2009-01-01

258

Design of core--shell-type nanoparticles carrying stable radicals in the core.  

PubMed

Utilizing the self-assembled core-shell-type polymeric micelle technique, high-performance nanoparticles possessing stable radicals in the core and reactive groups on the periphery were prepared. The anionic ring-opening polymerization of ethylene oxide (EO) was carried out using potassium 3,3-diethoxypropanolate as an initiator, followed by mesylation with methanesulfonyl chloride to obtain acetal-poly(ethylene glycol)-methanesulfonate (acetal-PEG-Ms; 1). Compound 1 was reacted with potassium O-ethyldithiocarbonate, followed by treatment with n-propylamine to obtain heterobifunctional PEG derivatives containing both sulfanyl and acetal terminal groups (acetal-PEG-SH) (2) in a highly selective and quantitative manner. Poly(ethylene glycol)-block-poly(chloromethylstyrene) (acetal-PEG-b-PCMS) (3) was synthesized by the free-radical telomerization of chloromethylstyrene (CMS) using 2 as a telogen. The chloromethyl groups in the PCMS segment of the block copolymer (3) were quantitatively converted to 2,2,6,6-tetramethylpiperidinyloxys (TEMPOs) via the amination of 3 with 4-amino-TEMPO to obtain acetal-PEG-b-PCMS containing TEMPO moieties (4). The obtained 4 formed core-shell-type nanoparticles in aqueous media when subjected to the dialysis method: the cumulant average diameter of the nanoparticles was about 40 nm, and the nanoparticles emitted intense electron paramagnetic resonance (EPR) signals. The TEMPO radicals in the core of the nanoparticles showed reduction resistance even in the presence of 3.5 mM ascorbic acid. This means that these nanoparticles are anticipated as high-performance bionanoparticles that can be used in vivo. PMID:19191564

Yoshitomi, Toru; Miyamoto, Daisuke; Nagasaki, Yukio

2009-03-01

259

Design review report for rotary mode core sample truck (RMCST) modifications for flammable gas tanks, preliminary design  

SciTech Connect

This report documents the completion of a preliminary design review for the Rotary Mode Core Sample Truck (RMCST) modifications for flammable gas tanks. The RMCST modifications are intended to support core sampling operations in waste tanks requiring flammable gas controls. The objective of this review was to validate basic design assumptions and concepts to support a path forward leading to a final design. The conclusion reached by the review committee was that the design was acceptable and efforts should continue toward a final design review.

Corbett, J.E.

1996-02-01

260

Heterogeneous Multi-core SoC Implementation with System-Level Design Methodology  

Microsoft Academic Search

The trend towards heterogeneous multi-core integration and higher communication bandwidth drastically increases the complexity of the SoC. Architecture design and system validation become extremely challenging. This paper presents a multi-core computing platform which consists of general-purpose microprocessor and dual programmable digital signal processor (DSP) cores for multimedia applications. To demonstrate its outstanding performance and energy efficiency, we develop multimedia and

Jen-Chieh Yeh; Kung-Ming Ji; Shing-Wu Tung; Shau-Yin Tseng

2011-01-01

261

Design of an asynchronous ring bus architecture for multi-core systems  

Microsoft Academic Search

In the multi-core systems, the data transfer between cores becomes a major challenge. An asynchronous ring bus, which is 33 bit width, adopting dual-rail single-track data protocol is proposed in this paper. Owning to asynchronous circuits design, there are different transfer times in different hop counts. For providing higher throughput, multiple cores which are able to access the bus simultaneously

Kai-ming Yang; Kin-fong Lei; Jih-ching Chiu

2010-01-01

262

Iron-core superconducting magnet design and test results for Maglev application  

Microsoft Academic Search

Design and test results are presented for a superconducting electromagnet for levitating and propelling Maglev vehicles at high velocities. A U-shaped iron core carries a superconducting magnet around its back leg and a normal control coil around each leg of the U-core. The open side of the U-core is bridged by an iron rail through a large airgap between the

S. Kalsi; M. Proise; T. Schultheiss; B. Dawkins; K. Herd

1995-01-01

263

ATR LEU Monothlic and Dispersed with 10B Loading Minimization DesignNeutronics Performance Analysis  

SciTech Connect

The Advanced Test Reactor (ATR), currently operating in the United States, is used for material testing at very high neutron fluxes. Powered with highly enriched uranium (HEU), the ATR has a maximum thermal power rating of 250 MWth. Because of the large test volumes located in high flux areas, the ATR is an ideal candidate for assessing the feasibility of converting HEU driven reactor cores to low-enriched uranium (LEU) cores. The present work investigates the optimized LEU Monolithic and Dispersed fuel with 10B loading minimization design and evaluates the subsequent neutronics operating effects of these optimized fuel designs. The MCNP ATR 1/8th core model was used to optimize the 235U and minimize the 10B loading in the LEU core, such that the differences in K-eff and heat flux profiles between the HEU and LEU cores were minimized. The fuel depletion methodology MCWO was used to calculate K eff versus effective full power days (EFPD) in this paper. The MCWO-calculated results for the optimized LEU Monolithic and Dispersed fuel cases demonstrated adequate excess reactivity such that the K-eff versus EFPD plot is similar to the ATR reference HEU case study. Each HEU fuel element contains 19 fuel plates with a fuel meat thickness of 0.508 mm (20 mil). In this work, the proposed LEU Monolithic (U-10Mo) core conversion case with nominal fuel meat thickness of 0.330 mm (13 mil) and 235U enrichment of 19.7 wt% is used to optimize the radial heat flux profile by varying the fuel meat thickness. The proposed LEU fuel meat varies from 0.203 mm (8.0 mil) to 0.254 mm (10.0 mil) at the inner four fuel plates (1-4) and outer four fuel plates (16-19). In addition, an optimized LEU dispersed (U7Mo) case with all the fuel meat thickness of 0.635 mm (25 mil) was also proposed. Then, for both Monolithic and dispersed cases, a burnable absorber – 10B, was added in the inner and outer plates to reduce the initial excess reactivity, and the higher to average ratio of the inner/outer heat flux more effectively. The final minimized 10B loading for LEU case studies will have 0.635 g in the LEU fuel meat at the inner 2 fuel plates (1-2) and outer 2 fuel plates (18-19), which can achieve peak to average ratios similar to those for the ATR reference HEU case study. The investigation of this paper shows the optimized LEU Monolithic (U-10Mo) and Dispersed (U7Mo) cases can all meet the LEU conversion objectives.

G. S. Chang

2001-10-01

264

Design studies for a high-resolution, transportable neutron radiography\\/radioscopy system  

Microsoft Academic Search

A preliminary design has been developed for a high-resolution, transportable neutron radiology system (TNRS) concept. The primary system requirement is taken to be a thermal neutron flux of 106 n\\/(cm2-sec) with a L\\/D ratio of 100. The approach is to use an accelerator-driven neutron source, with a radiofrequency quadrupole (RFQ) as the primary accelerator component. Initial concepts for all of

George H. Gillespie; Bradley J. Micklich; Gerry E. McMichael

1997-01-01

265

Design studies for a high-resolution, transportable neutron radiography\\/radioscopy system  

Microsoft Academic Search

A preliminary design has been developed for a high-resolution, transportable neutron radiology system (TNRS) concept. The primary system requirement is taken to be a thermal neutron flux of 10[sup 6] n\\/(cm[sup 2]-sec) with a L\\/D ratio of 100. The approach is to use an accelerator-driven neutron source, with a radiofrequency quadrupole (RFQ) as the primary accelerator component. Initial concepts for

G. H. Gillespie; B. J. Micklich; G. E. McMichael

1996-01-01

266

Double core evolution. 7: The infall of a neutron star through the envelope of its massive star companion  

NASA Astrophysics Data System (ADS)

Binary systems with properties similar to those of high-mass X-ray binaries are evolved through the common envelope phase. Three-dimensional simulations show that the timescale of the infall phase of the neutron star depends upon the evolutionary state of its massive companion. We find that tidal torques more effectively accelerate common envelope evolution for companions in their late core helium-burning stage and that the infall phase is rapid (approximately several initial orbital periods). For less evolved companions the decay of the orbit is longer; however, once the neutron star is deeply embedded within the companion's envelope the timescale for orbital decay decreases rapidly. As the neutron star encounters the high-density region surrounding the helium core of its massive companion, the rate of energy loss from the orbit increases dramatically leading to either partial or nearly total envelope ejection. The outcome of the common envelope phase depends upon the structure of the evolved companion. In particular, it is found that the entire common envelope can be ejected by the interaction of the neutron star with a red supergiant companion in binaries with orbital periods similar to those of long-period Be X-ray binaries. For orbital periods greater than or approximately equal to 0.8-2 yr (for companions of mass 12-24 solar mass) it is likely that a binary will survive the common envelope phase. For these systems, the structure of the progenitor star is characterized by a steep density gradient above the helium core, and the common envelope phase ends with a spin up of the envelope to within 50%-60% of corotation and with a slow mass outflow. The efficiency of mass ejection is found to be approximately 30%-40%. For less evolved companions, there is insufficient energy in the orbit to unbind the common envelope and only a fraction of it is ejected. Since the timescale for orbital decay is always shorter than the mass-loss timescale from the common envelope, the two cores will likely merge to form a Thorne-Zytkow object. Implications for the origin of Cyg X-3, an X-ray source consisting of a Wolf-Rayet star and a compact companion, and for the fate of the remnant binary consisting of a helium star and a neutron star are briefly discussed.

Terman, James L.; Taam, Ronald E.; Hernquist, Lars

1995-05-01

267

Design of neutron beams at the Argonne Continuous Wave Linac (ACWL) for boron neutron capture therapy and neutron radiography  

SciTech Connect

Neutron beams are designed for capture therapy based on p-Li and p-Sc reactions using the Argonne Continuous Wave Linac (ACWL). The p-Li beam will provide a 2.5 {times} 10{sup 9} n/cm{sup 2}s epithermal flux with 7 {times} 10{sup 5} {gamma}/cm{sup 2}s contamination. On a human brain phantom, this beam allows an advantage depth (AD) of 10 cm, an advantage depth dose rate (ADDR) of 78 cGy/min and an advantage ratio (AR) of 3.2. The p-Sc beam offers 5.9 {times} 10{sup 7} n/cm{sup 2}s and a dose performance of AD = 8 cm and AR = 3.5, suggesting the potential of near-threshold (p,n) reactions such as the p-Li reaction at E{sub p} = 1.92 MeV. A thermal radiography beam could also be obtained from ACWL.

Zhou, X.L. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Nuclear Engineering; McMichael, G.E. [Argonne National Lab., Idaho Falls, ID (United States). Technology Development Div.

1994-10-01

268

Refractory metal component technology for in-core sensor design  

Microsoft Academic Search

Recent advances in refractory metal technology have dramatically extended in the operating range of reactor in-core sensors. Temperatures as high as 2500°C in fuel\\/inert gas have been reliably measured during simulated accident conditions; sensors capable of service to 2200°C in accident water\\/steam environments now appear within reach. The accomplishments reflect an increased understanding of the physical and chemical properties of

1986-01-01

269

Design and optimization of a CCD-neutron radiography detector  

NASA Astrophysics Data System (ADS)

Radiography is a method to visualize the inner structure of macroscopic samples. It is based on the principle of the attenuation of radiation passing through matter, depending on the sample material and geometry. Besides the well-known radiographic examinations with X-rays and /?-rays, neutron radiography provides an important endorsement to radiographic examinations in the field of non-destructive testing (NDT), as contrary to X-rays, neutrons are attenuated by some light materials, as hydrogen, boron and lithium but penetrate many heavy materials. Neutrons are even able to distinguish between different isotopes and besides, neutron radiography is an important tool for the investigation of radioactive materials. One of the key components of a radiography facility is the detector. Usually, it is a two-dimensional, integrating imaging device. For neutron radiography applications requiring high quantitative precision as well as for neutron tomography investigations, a CCD-camera-based neutron radiography detector has been developed. It consists of a neutron sensitive scintillator screen, a nitrogen-cooled slow-scan CCD-camera and a mirror to reflect the light emitted by the scintillator to the CCD-camera. The whole assembly is placed in a light-tight enclosure. This paper presents the basic principle of this detector system, the strategy for the selection of the individual detector components, comparisons of the influence of the use of different components on the properties of the whole imaging device and results of the first test measurements.

Koerner, S.; Lehmann, E.; Vontobel, P.

2000-11-01

270

Power Distributions in Fresh and Depleted LEU and HEU Cores of the MITR Reactor.  

National Technical Information Service (NTIS)

The Massachusetts Institute of Technology Reactor (MITR-II) is a research reactor in Cambridge, Massachusetts designed primarily for experiments using neutron beam and in-core irradiation facilities. It delivers a neutron flux comparable to current LWR po...

E. H. Wilson J. G. Stevens L. Hu N. E. Horelik P. E. Dunn T. H. Newton

2012-01-01

271

Coded aperture Fast Neutron Analysis: Latest design advances  

NASA Astrophysics Data System (ADS)

Past studies have showed that materials of concern like explosives or narcotics can be identified in bulk from their atomic composition. Fast Neutron Analysis (FNA) is a nuclear method capable of providing this information even when considerable penetration is needed. Unfortunately, the cross sections of the nuclear phenomena and the solid angles involved are typically small, so that it is difficult to obtain high signal-to-noise ratios in short inspection times. CAFNA© aims at combining the compound specificity of FNA with the potentially high SNR of Coded Apertures, an imaging method successfully used in far-field 2D applications. The transition to a near-field, 3D and high-energy problem prevents a straightforward application of Coded Apertures and demands a thorough optimization of the system. In this paper, the considerations involved in the design of a practical CAFNA system for contraband inspection, its conclusions, and an estimate of the performance of such a system are presented as the evolution of the ideas presented in previous expositions of the CAFNA concept. .

Accorsi, Roberto; Lanza, Richard C.

2001-07-01

272

2ND Reactor Core of the NS Otto Hahn. Design, Operation Experience, Developments.  

National Technical Information Service (NTIS)

Details of the design of the 2nd reactor core are given, followed by a brief report summarising the operating experience gained with this 2nd core, as well as by an evaluation of measured data and statements concerning the usefulness of the knowledge gain...

H. J. Manthey H. Kracht

1979-01-01

273

Design of saturated iron core superconducting fault current limiter based on numerical calculation  

Microsoft Academic Search

The saturated iron core superconducting fault current limiter (SCFCL) utilizes the non-linear of ferromagnetic hysteresis to change its inductance. Its cores are saturated deeply under normal operation but driven out of saturation whenever fault occurs, so it is very difficult to design this SCFCL through theoretical calculation and there will be biggish error if deal the magnetization curve with subsection

Zhang Xuhong; Zhou Youqing; Zhang Zhifeng

2005-01-01

274

Neutron momentum distribution from ''core break-up'' reactions of halo nuclei.  

National Technical Information Service (NTIS)

Neutron angular distributions from violent break-up reactions of Li-11 and Be-11 have been measured at 28 MeV/u and 280 MeV/u and at 41 MeV/u and 460 MeV/u, respectively. The derived neutron momentum distributions show a narrow component in transverse mom...

T. Nilsson T. Blaich M. J. G. Borge L. V. Chulkov T. W. Elze

1995-01-01

275

DELAYED NEUTRON ECONOMY AND CONTROL IN A DIRECT CONTACT CORE LIQUID METAL FUELED REACTOR  

Microsoft Academic Search

Losses of delayed neutron precursors are estimated for liquid-metal-; fueled reactor models in which the coolant is in direct contact with the flowing ; fuel. It is shown that as much as 90% of the precursors may be extracted by the ; coolant before decaying to supply neutrons. As a result, the excess reactivity ; corresponding to prompt critical can

1961-01-01

276

Preliminary Neutronics Design and Analysis of D2O Cooled High Conversion PWRs  

SciTech Connect

This report presents a neutronics analysis of tight-pitch D2O-cooled PWRs loaded with MOX fuel and focuses essentially on the Pu breeding potential of such reactors as well as on an important safety parameter, the void coefficient, which has to be negative. It is well known that fast reactors have a better neutron economy and are better suited than thermal reactors to breed fissile material from neutron capture in fertile material. Such fast reactors (e.g. sodium-cooled reactors) usually rely on technologies that are very different from those of existing water-cooled reactors and are probably more expensive. This report investigates another possibility to obtain a fast neutron reactor while still relying mostly on a PWR technology by: (1) Tightening the lattice pitch to reduce the water-to-fuel volume ratio compared to that of a standard PWR. Water-to-fuel volume ratios of between 0.45 and 1 have been considered in this study while a value of about 2 is typical of standard PWRs, (2) Using D2O instead of H2O as a coolant. Indeed, because of its different neutron physics properties, the use of D2O hardens the neutron spectrum to an extent impossible with H2O when used in a tight-pitch lattice. The neutron spectra thus obtained are not as fast as those in sodium-cooled reactor but they can still be characterized as fast compared to that of standard PWR neutron spectra. In the phase space investigated in this study we did not find any configurations that would have, at the same time, a positive Pu mass balance (more Pu at the end than at the beginning of the irradiation) and a negative void coefficient. At this stage, the use of radial blankets has only been briefly addressed whereas the impact of axial blankets has been well defined. For example, with a D2O-to-fuel volume ratio of 0.45 and a core driver height of about 60 cm, the fissile Pu mass balance between the fresh fuel and the irradiated fuel (50 GWd/t) would be about -7.5% (i.e. there are 7.5% fewer fissile Pu isotopes at the end than at the beginning of the irradiation) and the void coefficient would be negative. The addition of 1 cm of U-238 blanket at the top and bottom of the fuel would bring the fissile Pu mass balance from -7.5% to -6.5% but would also impact the void coefficient in the wrong way. In fact, it turns out that the void coefficient is so sensitive to the presence of axial blanket that it limits its size to only a few cm for driver fuel height of about 50-60 cm. For reference, the fissile Pu mass balance is about -35% in a standard PWR MOX fuel such as those used in France. In order to reduce the fissile Pu deficit and potentially reach a true breeding regime (i.e. a positive Pu mass balance), it would be necessary to make extensive use of radial blankets, both internal and external. Even though this was not addressed in detail here, it is reasonable to believe that at least as much U-238 blanket subassemblies as MOX driver fuel subassemblies would be necessary to breed enough Pu to compensate for the Pu deficit in the driver fuel. Hence, whereas a relatively simple D2O-cooled PWR core design makes it possible to obtain a near-breeder core, it may be necessary to more than double the mass of heavy metal in the core as well as the mass of heavy metal to reprocess per unit of energy produced in order to breed the few percents of Pu missing to reach a true breeding regime. It may be interesting to quantify these aspects further in the future.

Hikaru Hiruta; Gilles Youinou

2012-09-01

277

NEUTRON PHYSICS CALCULATION METHODS IN THE PHYSICAL LEVELING DESIGN OF POWER REACTORS  

Microsoft Academic Search

In view of the lack of uniformity in spatial distribution of the fuel ; elements, the neutron flux of a reactor is uneven, causing different levels of ; heat distribution in various points of the core. Achievement of the highest ; average heat generation in a power reactor system is limited by the requirement ; of providing for the maximum

N. N. Ponomarev-Stepnoi; E. S. Glushkov

1961-01-01

278

Near-Core and In-Core Neutron Radiation Monitors for Real Time Neutron Flux Monitoring and Reactor Power Level Measurements  

SciTech Connect

MPFDs are a new class of detectors that utilize properties from existing radiation detector designs. A majority of these characteristics come from fission chamber designs. These include radiation hardness, gamma-ray background insensitivity, and large signal output.

Douglas S. McGregor; Marvin L. Adams; Igor Carron; Paul Nelson

2006-06-12

279

A Workshop on Methods for Neutron Scattering Instrument Design. Introduction and Summary  

SciTech Connect

The future of neutron and x-ray scattering instrument development and international cooperation was the focus of the workshop on ``Methods for Neutron Scattering Instrument Design`` September 23-25 at the E.O. Lawrence Berkeley National Laboratory. These proceedings are a collection of a portion of the invited and contributed presentations.

Hjelm, Rex P.

1996-12-31

280

The design, construction and performance of a variable collimator for epithermal neutron capture therapy beams  

Microsoft Academic Search

A patient collimator for the fission converter based epithermal neutron beam (FCB) at the Massachusetts Institute of Technology Research Reactor (MITR-II) was built for clinical trials of boron neutron capture therapy (BNCT). A design was optimized by Monte Carlo simulations of the entire beam line and incorporates a modular construction for easy modifications in the future. The device was formed

K J Riley; P J Binns; S J Ali; O K Harling

2004-01-01

281

Evidence of a core-shell structure in the antiferromagnetic La0.2Ce0.8CrO3 nanoparticles by neutron scattering  

NASA Astrophysics Data System (ADS)

We report the evidence of a core-shell structure in the antiferromagnetic La0.2Ce0.8CrO3 nanoparticles by using a combination of neutron diffraction, polarized neutron small angle scattering (SANSPOL), and dc magnetization techniques. The neutron diffraction study establishes that the present nanoparticles are antiferromagnetic in nature. The magnetic scattering in the SANSPOL study arises from the shell part of the nanoparticles due to the disordered surface spins. The analysis of the SANSPOL data shows that these nanoparticles have a mean core diameter of 12.3±1.1 nm, and a shell thickness of 2.8±0.4 nm, giving a core-shell structure with an antiferromagnetic core, and a shell with a net magnetic moment under an applied magnetic field.

Manna, P. K.; Yusuf, S. M.; Mukadam, M. D.; Kohlbrecher, J.

2012-11-01

282

Multipurpose Advanced 'inherently' Safe Reactor (MARS): Core design studies  

SciTech Connect

In the year 2005, in collaboration with CEA, the University of Rome 'La Sapienza' investigated a new core model with the aim at increasing the performances of the reference one, by extending the burn-up to 60 GWD/t in the case of multi-loading strategy and investigating the characteristics and limitations of a 'once-through' option, in order to enhance the proliferation resistance. In the first part of this paper, the objectives of this study and the methods of calculation are briefly described, while in the second part the calculation results are presented. (authors)

Golfier, H. [DM2S/SERMA/LCA, CEA Saclay, 91191 Gif-sur-Yvette Cedex (France); Caterino, S. [Univ. of Rome La Sapienza, Dept. of Nuclear Engineering and Energy Conversion, Corso Vittorio Emanuele II, 244 00186 Rome (Italy); Poinot, C.; Delpech, M.; Mignot, G. [DM2S/SERMA/LCA, CEA Saclay, 91191 Gif-sur-Yvette Cedex (France); Naviglio, A.; Gandini, A. [Univ. of Rome La Sapienza, Dept. of Nuclear Engineering and Energy Conversion, Corso Vittorio Emanuele II, 244 00186 Rome (Italy)

2006-07-01

283

Cylindrical detector and preamplifier design for detecting neutrons  

NASA Astrophysics Data System (ADS)

Tissue equivalent proportional counters are frequently used to measure dose and dose equivalent in mixed radiation fields that include neutrons; however, detectors simulating sites 1mum in diameter underestimate the quality factor, Q, for low energy neutrons because the recoil protons do not cross the detectors. Proportional counters simulating different site-sizes can be used to get a better neutron dose equivalent measurement since the range and stopping power of protons generated by neutrons in the tissue-equivalent walls depend on the energy of the primary neutrons. The differences in the spectra measured by different size detectors will provide additional information on the incident neutron energy. Monte Carlo N-particle extended (MCNPX) code was used to simulate neutron transportation in proportional counters of different simulated tissue diameter. These Monte Carlo results were tested using two solid walled tissue equivalent proportional counters, 2mm and 10mm in diameter, simulating tissue volumes 0.1mum and 0.5mum in diameter, housed in a single vacuum chamber. Both detectors are built with 3mm thick tissue equivalent plastic (A-150) walls and propane gas inside for dose measurement. Using these two detectors, the spectra were compared to determine the underestimation of y for large detector, and thereby obtain more information of the incident neutron particles. Based on the MCNPX simulation and experimental results, we can see that the smaller detector produces a larger average lineal energy than the larger detector, which means the larger detector (0.5mum diameter tissue equivalent size) underestimates the Q value for the low energy neutron, therefore underestimates the effective dose. These results confirm the results of the typical analysis of lineal energy as a function of site size.

Xia, Zhenghua

284

Considerations in the design of an improved transportable neutron spectrometer  

NASA Astrophysics Data System (ADS)

The Transportable Neutron Spectrometer (TNS) has been used by the Ministry of Defence for over 15 years to characterise neutron fields in workplace environments and provide local correction factors for both area and personal dosimeters. In light of advances in neutron spectrometry, a programme to evaluate and improve TNS has been initiated. This paper describes TNS, presents its operation in known radioisotope fields and in a reactor environment. Deficiencies in the operation of the instrument are highlighted, together with proposals for updating the response functions and spectrum unfolding methodologies.

Williams, A. M.; Spyrou, N. M.; Brushwood, J. M.; Beeley, P. A.

2002-01-01

285

76 FR 14825 - Core Principles and Other Requirements for Designated Contact Markets  

Federal Register 2010, 2011, 2012, 2013

...3038-AD09 Core Principles and Other Requirements for Designated Contact Markets AGENCY: Commodity Futures Trading Commission. ACTION...site at http://www.cftc.gov. FOR FURTHER INFORMATION CONTACT: Nancy Markowitz, Assistant Deputy Director,...

2011-03-18

286

Development and applications of methodologies for the neutronic design of the Pebble Bed Advanced High Temperature Reactor (PB-AHTR)  

NASA Astrophysics Data System (ADS)

This study investigated the neutronic characteristics of the Pebble Bed Advanced High Temperature Reactor (PB-AHTR), a novel nuclear reactor concept that combines liquid salt (7LiF-BeF2---flibe) cooling and TRISO coated-particle fuel technology. The use of flibe enables operation at high power density and atmospheric pressure and improves passive decay-heat removal capabilities, but flibe, unlike conventional helium coolant, is not transparent to neutrons. The flibe occupies 40% of the PB-AHTR core volume and absorbs ˜8% of the neutrons, but also acts as an effective neutron moderator. Two novel methodologies were developed for calculating the time dependent and equilibrium core composition: (1) a simplified single pebble model that is relatively fast; (2) a full 3D core model that is accurate and flexible but computationally intensive. A parametric analysis was performed spanning a wide range of fuel kernel diameters and graphite-to-heavy metal atom ratios to determine the attainable burnup and reactivity coefficients. Using 10% enriched uranium ˜130 GWd/tHM burnup was found to be attainable, when the graphite-to-heavy metal atom ratio (C/HM) is in the range of 300 to 400. At this or smaller C/HM ratio all reactivity coefficients examined---coolant temperature, coolant small and full void, fuel temperature, and moderator temperature, were found to be negative. The PB-AHTR performance was compared to that of alternative options for HTRs, including the helium-cooled pebble-bed reactor and prismatic fuel reactors, both gas-cooled and flibe-cooled. The attainable burnup of all designs was found to be similar. The PB-AHTR generates at least 30% more energy per pebble than the He-cooled pebble-bed reactor. Compared to LWRs the PB-AHTR requires 30% less natural uranium and 20% less separative work per unit of electricity generated. For deep burn TRU fuel made from recycled LWR spent fuel, it was found that in a single pass through the core ˜66% of the TRU can be transmuted; this burnup is slightly superior to that attainable in helium-cooled reactors. A preliminary analysis of the modular variant for the PB-AHTR investigated the triple heterogeneity of this design and determined its performance characteristics.

Fratoni, Massimiliano

287

A compact neutron beam generator system designed for prompt gamma nuclear activation analysis.  

PubMed

In this work a compact system was designed for bulk sample analysis using the technique of PGNAA. The system consists of (252)Cf fission neutron source, a moderator/reflector/filter assembly, and a suitable enclosure to delimit the resulting neutron beam. The moderator/reflector/filter arrangement has been optimised to maximise the thermal neutron component useful for samples analysis with a suitably low level of beam contamination. The neutron beam delivered by this compact system is used to irradiate the sample and the prompt gamma rays produced by neutron reactions within the sample elements are detected by appropriate gamma rays detector. Neutron and gamma rays transport calculations have been performed using the Monte Carlo N-Particle transport code (MCNP5). PMID:21129990

Ghassoun, J; Mostacci, D

2010-11-19

288

Legal Protection on IP Cores for System-on-Chip Designs  

NASA Astrophysics Data System (ADS)

The current semiconductor industry has shifted from vertical integrated model to horizontal specialization model in term of integrated circuit manufacturing. In this circumstance, IP cores as solutions for System-on-Chip (SoC) have become increasingly important for semiconductor business. This paper examines to what extent IP cores of SoC effectively can be protected by current intellectual property system including integrated circuit layout design law, patent law, design law, copyright law and unfair competition prevention act.

Kinoshita, Takahiko

289

Low Power Design for a Multi-core Multi-thread Microprocessor  

Microsoft Academic Search

Power efficiency of microprocessor is essential to green computing. As most microprocessors become multi-core and multi-thread, it's important to study low power design for them. The architecture of MCMT, a multi-core multi-thread microprocessor, is described briefly in this paper. Several low power design techniques, including fine-grained clock gating, instruction throttling and adaptive L2 cache are presented to reduce both the

Wang Yong-Wen; Zheng Qian-Bing; Dou Qiang; Zhang Min-Xuan

2010-01-01

290

Minimum copper and core losses power inductor design  

Microsoft Academic Search

A design procedure which allows for assembling power inductors with minimum overall power loss is given in this paper. The inductor design is carried out by using an iterative procedure where the operating flux density is increased from zero to the saturation value. For any given value of the flux density the winding resulting in the lower AC resistance is

M. Bartoli; A. Reatti; M. K. Kazimierczuk

1996-01-01

291

Characterization of core debris/concrete interactions for the Advanced Neutron Source. ANS Severe Accident Analysis Program  

SciTech Connect

This report provides the results of a recent study conducted to explore the molten core/concrete interaction (MCCI) issue for the Advanced Neutron Source (ANS). The need for such a study arises from the potential threats to reactor system integrity posed by MCCI. These threats include direct attack of the concrete basemat of the containment; generation and release of large quantities of gas that can pressurize the containment; the combustion threat of these gases; and the potential generation, release, and transport of radioactive aerosols to the environment.

Hyman, C.R.; Taleyarkhan, R.P.

1992-02-01

292

Design of large-core single-mode Yb3+-doped photonic crystal fiber  

NASA Astrophysics Data System (ADS)

The effective index of the cladding fundamental space-filling mode in photonic crystal fiber (PCF) is simulated by the effective index method. The variation of the effective index with the structure parameters of the fiber is achieved. For the first time, the relations of the V parameter of Yb3+-doped PCF with the refractive index of core and the structure parameters of the fiber are provided. The single-mode characteristics of large-core Yb3+-doped photonic crystal fibers with 7 and 19 missing air holes in the core are analyzed. The large-core single-mode Yb3+-doped photonic crystal fibers with core diameters of 50 ?m, 100 ?m and 150 ?m are designed. The results provide theory instruction for the design and fabrication of fiber.

Zhao, Xing-tao; Zheng, Yi; Liu, Xiao-xu; Zhou, Gui-yao; Liu, Zhaolun; Hou, Lan-tian

2012-05-01

293

Preliminary detector design ST862-prototype neutron detector  

NASA Astrophysics Data System (ADS)

The detection of fast neutrons has been accomplished with commercially available liquid scintillators in detectors. Liquid scintillators discriminate fast neutrons from gamma radiation by discarding pulses with short decay constants. However, pulse-timing methods require expensive, bulky equipment and a high degree of technical sophistication in the user. Researchers at Pacific Northwest Laboratory have developed a new class of scintillating material, polymerizing crystals of CaF2Eu and liquid acrylate monomers with matched indexes of refraction. The new detectors avoid the pulse-timing methods of liquid detectors and allow detectors to be large and relatively light. Fast neutrons can be discriminated from gamma radiation solely on the basis of pulse height (i.e., energy deposition). Using these detectors, a hand-held neutron detection instrument is proposed that can operate on battery power for 8 to 12 hours and be easily used in field conditions for surveying vehicles and structures.

Miller, S. D.; Affinito, J. D.; Sisk, D. R.

1993-12-01

294

Neutronic design studies for the MIT fission converter beam  

Microsoft Academic Search

Currently available epithermal neutron beams at the Massachusetts Institute of Technology (MIT) are not sufficiently intense to meet the anticipated demand for boron neutron capture therapy (BNCT) treatments if initial, currently in progress clinical trials of BNCT prove successful. Indeed, they are not really adequate for extensive (phase-III) clinical trials. To fulfill this need, a high-intensity, high-quality fission converter-based epithermal

W. S. Kiger; O. K. Harling

1996-01-01

295

Neutron Momentum Distributions from ``Core Break-Up'' Reactions of Halo Nuclei  

Microsoft Academic Search

Neutron angular distributions from violent break-up reactions of 11Li and 11Be have been measured at 28 MeV\\/u and 280 MeV\\/u and at 41 MeV\\/u and 460 MeV\\/u, respectively. The derived neutron momentum distributions show a narrow component in transverse momentum that is within uncertainties independent of beam energy and target charge. This component is suggested to be simply related to

T. Nilsson; Th. Blaich; M. J. G. Borge; L. V. Chulkov; Th. W. Elze; H. Emling; H. Geissel; K. Grimm; D. Guillemaud-Mueller; P. G. Hansen; R. Holzmann; P. Hornshøj; F. Humbert; H. Irnich; L. Johannsen; B. Jonson; M. Keim; J. G. Keller; H. Klingler; J. V. Kratz; R. Kulessa; D. Lambrecht; Y. Leifels; M. Lewitowicz; A. Magel; M. F. Mohar; A. C. Mueller; G. Münzenberg; R. Neugart; F. Nickel; G H Nyman; A. Richter; K. Riisager; M.-G. Saint-Laurent; C. Scheidenberger; G. Schrieder; W. Schwab; B. M. Sherrill; H. Simon; O. Sorlin; K. Stelzer; J. Stroth; O. Tengblad; E. Wajda; K. Wilhelmsen Rolander; M. Zinser; E. Zude

1995-01-01

296

Design Core Competence Diagnosis: A Case From the Automotive Industry  

Microsoft Academic Search

1990's have been marked by significant changes both in the strategic management field, with the development of competence-based management and the use of the concept of value-creating network, and in the design management field, with the diffusion of matrix-based tools that help to manage the interdependencies between three domains of design projects: product, process, and organization. Few researchers have helped

Éric Bonjour; Jean-Pierre Micaëlli

2010-01-01

297

PIUS Core Performance Analysis.  

National Technical Information Service (NTIS)

A detailed evaluation of the fuel burnup dependent power distribution and the scram reactivity for the PIUS reactor design has been performed. The analyses were carried out using the CPM lattice physics and NODE-P2 core neutronics/thermal-hydraulics codes...

J. F. Carew A. Aronson D. M. Cokinos A. Prince E. C. Selcow

1996-01-01

298

System design considerations for fast-neutron interrogation systems  

SciTech Connect

Nonintrusive interrogation techniques that employ fast neutrons are of interest because of their sensitivity to light elements such as carbon, nitrogen, and oxygen. The primary requirement of a fast-neutron inspection system is to determine the value of atomic densities, or their ratios, over a volumetric grid superimposed on the object being interrogated. There are a wide variety of fast-neutron techniques that can provide this information. The differences between the various nuclear systems can be considered in light of the trade-offs relative to the performance requirements for each system`s components. Given a set of performance criteria, the operational requirements of the proposed nuclear systems may also differ. For instance, resolution standards will drive scanning times and tomographic requirements, both of which vary for the different approaches. We are modelling a number of the fast-neutron interrogation techniques currently under consideration, to include Fast Neutron Transmission Spectroscopy (FNTS), Pulsed Fast Neutron Analysis (PFNA), and its variant, 14-MeV Associated Particle Imaging (API). The goals of this effort are to determine the component requirements for each technique, identify trade-offs that system performance standards impose upon those component requirements, and assess the relative advantages and disadvantages of the different approaches. In determining the component requirements, we will consider how they are driven by system performance standards, such as image resolution, scanning time, and statistical uncertainty. In considering the trade-offs between system components, we concentrate primarily on those which are common to all approaches, for example: source characteristics versus detector array requirements. We will then use the analysis to propose some figures-of-merit that enable performance comparisons between the various fast-neutron systems under consideration. The status of this ongoing effort is presented.

Micklich, B.J.; Curry, B.P.; Fink, C.L.; Smith, D.L.; Yule, T.J.

1993-10-01

299

Design of a compact high-power neutron source—The EURISOL converter target  

NASA Astrophysics Data System (ADS)

The EURISOL project, a multi-lateral initiative supported by the EU, aims to develop a facility to achieve high yields of isotopes in radioactive beams and extend the variety of these isotopes towards more exotic types. The neutron source at the heart of the projected facility is designed to generate isotopes by fissioning uranium carbide (UC) targets arranged around a 4 MW neutron source. For reasons of efficiency, it is essential that the neutron source be as compact as possible, to avoid losing neutrons by absorption whilst maximising the escaping neutron flux, thus increasing the number of fissions in the UC targets. The resulting configuration presents a challenge in terms of absorbing heat deposition rates of up to 8 kW/cm3 in the neutron source; it has led to the selection of liquid metal for the target material. The current paper presents the design of a compact high-power liquid-metal neutron source comprising a specially optimised beam window concept. The design is based on two-dimensional (2D) and three-dimensional (3D) computational fluid dynamics (CFD) numerical simulations for thermal hydraulics and hydraulic aspects, as well as finite-element method (FEM) for assessing thermo-mechanical stability. The resulting optimised design was validated by a dedicated hydraulic test under realistic flow conditions. A full-scale mock-up was built at the Paul Scherrer Institute (PSI) and was tested at the Institute of Physics of the University of Latvia (IPUL).

Samec, K.; Milenkovi?, R. Ž.; Dementjevs, S.; Ashrafi-Nik, M.; Kalt, A.

2009-07-01

300

Neutronic Analyses for HEU to LEU Fuel Conversion of the Massachusetts Institute of Technology.  

National Technical Information Service (NTIS)

The Massachusetts Institute of Technology (MIT) reactor (MITR-II), based in Cambridge, Massachusetts, is a research reactor designed primarily for experiments using neutron beam and in-core irradiation facilities. It delivers a neutron flux comparable to ...

A. Bergeron E. N. Wilson J. G. Stevens N. Horelik T. H. Newton

2011-01-01

301

Modified Y-TZP Core Design Improves All-ceramic Crown Reliability  

PubMed Central

This study tested the hypothesis that all-ceramic core-veneer system crown reliability is improved by modification of the core design. We modeled a tooth preparation by reducing the height of proximal walls by 1.5 mm and the occlusal surface by 2.0 mm. The CAD-based tooth preparation was replicated and positioned in a dental articulator for core and veneer fabrication. Standard (0.5 mm uniform thickness) and modified (2.5 mm height lingual and proximal cervical areas) core designs were produced, followed by the application of veneer porcelain for a total thickness of 1.5 mm. The crowns were cemented to 30-day-aged composite dies and were either single-load-to-failure or step-stress-accelerated fatigue-tested. Use of level probability plots showed significantly higher reliability for the modified core design group. The fatigue fracture modes were veneer chipping not exposing the core for the standard group, and exposing the veneer core interface for the modified group.

Silva, N.R.F.A.; Bonfante, E.A.; Rafferty, B.T.; Zavanelli, R.A.; Rekow, E.D.; Thompson, V.P.; Coelho, P.G.

2011-01-01

302

Design of radial neutron spectrometer array for the International Thermonuclear Experimental Reactor  

SciTech Connect

We designed the radial neutron spectrometer using a new type DT neutron spectrometer base on a recoil proton counter-telescope technique aiming ion temperature measurement for the International Thermonuclear Experimental Reactor (ITER). The neutron spectrometer will be installed on the well collimated neutron beam line. A large area recoil proton emitter is placed parallel to the incident neutron beam and microchannel collimating plates are inserted between the radiator and the recoil proton detectors away from the neutron beam in order to limit the scattering angle of protons to the proton detectors. Here a very thin polyethylene film and a silicon surface barrier detector are employed as the radiator and proton detector, respectively. The energy resolution and detection efficiency are estimated to be 2.5{percent} and 1{times}10{sup {minus}5} countsneutron{sup {minus}1}m{sup 2}, respectively, for the DT neutron through Monte Carlo calculations. Five units of the spectrometers will be installed just outside the biological shield, will include a fan array using penetrations inside the bioshield and a precollimator in the horizontal port. The lifetime of the proton detectors is estimated to be about one year in the basic performance phase of ITER by neutron transport calculations using the Monte Carlo neutron and photon transport code (MCNP). {copyright} {ital 1997 American Institute of Physics.}

Nishitani, T.; Kasai, S. [Japan Atomic Energy Research Institute, Naka-machi, Naka-gun, Ibaraki-ken 311-01 (Japan); Iguchi, T.; Takada, E. [University of Tokyo, Bunkyo-ku, Tokyo 113 (Japan); Ebisawa, K.; Kita, Y. [TOSHIBA Corporation, Chiyoda-ku, Tokyo 100 (Japan)

1997-01-01

303

Design of a laboratory for experiments with a pulsed neutron source.  

PubMed

We present the results of a neutron shielding design and optimisation study performed to reduce the exposure to radiological doses arising from a 14 MeV pulsed neutron generator (PNG) having a maximum emission strength of 2.0 x 10(8) neutrons s(-1). The source was intended to be used in a new irradiation facility for the realisation of an experiment on acoustical cavitation in liquids. This paper describes in detail how the facility was designed to reduce both neutron and gamma-ray dose rates to acceptable levels, taking into account the ALARP principle in following the steps of optimisation. In particular, this work compares two different methods of optimisation to assess neutron dose rates: the use of analytical methods and the use of Monte Carlo simulations (MCNPX 2.4). The activation of the surrounding materials during operation was estimated using the neutron spectra as input to the FISPACT 3.0 code. The limitations of a first-order analytical model to determine the neutron activation levels are highlighted. The impact that activation has on the choice of the materials to be used inside the laboratory and on the waiting time before anyone can safely enter the room after the neutron source is switched off is also discussed. PMID:19454793

Memoli, G; Trusler, J P M; Ziver, A K

2009-05-19

304

Multiangle simulation of flavor evolution in the neutronization neutrino burst from an O-Ne-Mg core-collapse supernova  

SciTech Connect

We report results of the first 3x3 'multiangle' simulation of the evolution of neutrino flavor in the core-collapse supernova environment. In particular, we follow neutrino flavor transformation in the neutronization neutrino burst of an O-Ne-Mg core-collapse event. Though in a qualitative sense our results are consistent with those obtained in 3x3 single-angle simulations, at least in terms of neutrino mass hierarchy dependence, performing multiangle calculations is found to reduce the adiabaticity of flavor evolution in the normal neutrino mass hierarchy, resulting in lower swap energies. Differences between single-angle and multiangle results are largest for the normal neutrino mass hierarchy. Our simulations also show that current uncertainties in the measured mass-squared and mixing angle parameters translate into uncertainties in neutrino swap energies. Our results show that at low {theta}{sub 13} it may be difficult to resolve the neutrino mass hierarchy using the O-Ne-Mg neutronization neutrino burst.

Cherry, John F.; Fuller, George M.; Carlson, J.; Duan Huaiyu; Qian Yongzhong [Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States); Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

2010-10-15

305

3He neutron detector design for active detection of cargo containers  

NASA Astrophysics Data System (ADS)

We report on the design of a neutron detector using industry standard 3He tubes to count delayed neutrons during the interrogation of cargo containers for the presence of Special Nuclear Material (SNM). Simulations of the detector design were run for delayed neutron spectra for a variety of cargos containing SNM using the Monte Carlo computer code COG. The simulations identified parameters crucial to optimize the detector design. These choices include moderating material type and thickness, tube spacing, tube pressure and number of tubes. An experimental prototype was also constructed based on the simulated design specifications. This paper discusses the parameters that lead up to the optimized detector design. It also compares the performance of the Monte Carlo simulated design and the experimental detector when exposed to a 239Pu-Be source.

McDevitt, Daniel B.; Eberhard, J. W.; Zelakiewicz, Scott; Maschinot, Aaron

2008-05-01

306

Large LOCA assessment of an early preconceptual design for the Advanced Neutron Source reactor.  

National Technical Information Service (NTIS)

Designing the Advanced Neutron Source (ANS) reactor at Oak Ridge National Laboratory (ORNL) draws on the set of prior experience, and uses the best expert judgment to arrive a a trial design. The trial design is subjected to various evaluations to detect ...

R. R. Fullwood

1991-01-01

307

Conceptual design and neutronics analyses of a fusion reactor blanket simulation facility  

Microsoft Academic Search

A new conceptual design of a fusion reactor blanket simulation facility has been developed. This design follows the principles that have been successfully employed in the Purdue Fast Breeder Blanket Facility (FBBF), where experiments have resulted in the discovery of substantial deficiencies in neutronics predictions. With this design, discrepancies between calculation and experimental data can be nearly fully attributed to

D. E. Beller; K. O. Ott; W. K. Terry

1987-01-01

308

Conceptual design and neutronics analyses of a fusion reactor blanket simulation facility  

Microsoft Academic Search

A new conceptual design of a fusion reactor blanket simulation facility was developed. This design follows the principles that have been successfully employed in the Purdue Fast Breeder Blanket Facility (FBBR), because experiments conducted in it have resulted in the discovery of deficiencies in neutronics prediction methods. With this design, discrepancies between calculation and experimental data can be fully attributed

Beller

1986-01-01

309

Conceptual design and neutronics analyses of a fusion-reactor blanket-simulation facility. Doctoral thesis  

Microsoft Academic Search

A new conceptual design of a fusion-reactor blanket-simulation facility was developed. This design follows the principles that have been successfully employed in the Purdue Fast Breeder Blanket Facility (FBBF), because experiments conducted in it have resulted in the discovery of deficiencies in neutronics prediction methods. With this design, discrepancies between calculation and experimental data can be fully attributed to calculation

Beller

1986-01-01

310

Large LOCA assessment of an early preconceptual design for the Advanced Neutron Source reactor  

Microsoft Academic Search

Designing the Advanced Neutron Source (ANS) reactor at Oak Ridge National Laboratory (ORNL) draws on the set of prior experience, and uses the best expert judgment to arrive a a trial design. The trial design is subjected to various evaluations to detect and eliminate weakness, thereby enhancing the operability and minimizing risk. This report provides a preliminary and somewhat qualitative

Fullwood

1991-01-01

311

Neutron capture on Pt isotopes in iron meteorites and the Hf-W chronology of core formation in planetesimals  

NASA Astrophysics Data System (ADS)

The short-lived 182Hf-182W isotope system can provide powerful constraints on the timescales of planetary core formation, but its application to iron meteorites is hampered by neutron capture reactions on W isotopes resulting from exposure to galactic cosmic rays. Here we show that Pt isotopes in magmatic iron meteorites are also affected by capture of (epi)thermal neutrons and that the Pt isotope variations are correlated with variations in 182W/184W. This makes Pt isotopes a sensitive neutron dosimeter for correcting cosmic ray-induced W isotope shifts. The pre-exposure 182W/184W derived from the Pt-W isotope correlations of the IID, IVA and IVB iron meteorites are higher than most previous estimates and are more radiogenic than the initial 182W/184W of Ca-Al-rich inclusions (CAI). The Hf-W model ages for core formation range from +1.6±1.0 million years (Ma; for the IVA irons) to +2.7±1.3 Ma after CAI formation (for the IID irons), indicating that there was a time gap of at least ˜1 Ma between CAI formation and metal segregation in the parent bodies of some iron meteorites. From the Hf-W ages a time limit of <1.5-2 Ma after CAI formation can be inferred for the accretion of the IID, IVA and IVB iron meteorite parent bodies, consistent with earlier conclusions that the accretion of differentiated planetesimals predated that of most chondrite parent bodies.

Kruijer, Thomas S.; Fischer-Gödde, Mario; Kleine, Thorsten; Sprung, Peter; Leya, Ingo; Wieler, Rainer

2013-01-01

312

Monte Carlo methods of neutron beam design for neutron capture therapy at the MIT Research Reactor (MITR-II).  

PubMed

Monte Carlo methods of coupled neutron/photon transport are being used in the design of filtered beams for Neutron Capture Therapy (NCT). This method of beam analysis provides segregation of each individual dose component, and thereby facilitates beam optimization. The Monte Carlo method is discussed in some detail in relation to NCT epithermal beam design. Ideal neutron beams (i.e., plane-wave monoenergetic neutron beams with no primary gamma-ray contamination) have been modeled both for comparison and to establish target conditions for a practical NCT epithermal beam design. Detailed models of the 5 MWt Massachusetts Institute of Technology Research Reactor (MITR-II) together with a polyethylene head phantom have been used to characterize approximately 100 beam filter and moderator configurations. Using the Monte Carlo methodology of beam design and benchmarking/calibrating our computations with measurements, has resulted in an epithermal beam design which is useful for therapy of deep-seated brain tumors. This beam is predicted to be capable of delivering a dose of 2000 RBE-cGy (cJ/kg) to a therapeutic advantage depth of 5.7 cm in polyethylene assuming 30 micrograms/g 10B in tumor with a ten-to-one tumor-to-blood ratio, and a beam diameter of 18.4 cm. The advantage ratio (AR) is predicted to be 2.2 with a total irradiation time of approximately 80 minutes. Further optimization work on the MITR-II epithermal beams is expected to improve the available beams. PMID:2268248

Clement, S D; Choi, J R; Zamenhof, R G; Yanch, J C; Harling, O K

1990-01-01

313

Monte Carlo methods of neutron beam design for neutron capture therapy at the MIT Research Reactor (MITR-II)  

SciTech Connect

Monte Carlo methods of coupled neutron/photon transport are being used in the design of filtered beams for Neutron Capture Therapy (NCT). This method of beam analysis provides segregation of each individual dose component, and thereby facilitates beam optimization. The Monte Carlo method is discussed in some detail in relation to NCT epithermal beam design. Ideal neutron beams (i.e., plane-wave monoenergetic neutron beams with no primary gamma-ray contamination) have been modeled both for comparison and to establish target conditions for a practical NCT epithermal beam design. Detailed models of the 5 MWt Massachusetts Institute of Technology Research Reactor (MITR-II) together with a polyethylene head phantom have been used to characterize approximately 100 beam filter and moderator configurations. Using the Monte Carlo methodology of beam design and benchmarking/calibrating our computations with measurements, has resulted in an epithermal beam design which is useful for therapy of deep-seated brain tumors. This beam is predicted to be capable of delivering a dose of 2000 RBE-cGy (cJ/kg) to a therapeutic advantage depth of 5.7 cm in polyethylene assuming 30 micrograms/g 10B in tumor with a ten-to-one tumor-to-blood ratio, and a beam diameter of 18.4 cm. The advantage ratio (AR) is predicted to be 2.2 with a total irradiation time of approximately 80 minutes. Further optimization work on the MITR-II epithermal beams is expected to improve the available beams. 20 references.

Clement, S.D.; Choi, J.R.; Zamenhof, R.G.; Yanch, J.C.; Harling, O.K. (Massachusetts Institute of Technology, Cambridge (USA))

1990-01-01

314

A review of irradiation effects on LWR core internal materials - neutron embrittlement.  

SciTech Connect

Austenitic stainless steels (SSs) are used extensively as structural alloys in the internal components of light water reactor (LWR) pressure vessels because of their relatively high strength, ductility, and fracture toughness. However, exposure to neutron irradiation for extended periods not only changes the microstructure and microchemistry of these steels, but also degrades their fracture properties. The existing data on irradiated austenitic SSs are reviewed to determine the effects of key parameters such as material type and condition and irradiation temperature, dose, and dose rate on neutron embrittlement. Differences in the radiation-induced degradation of fracture properties between LWR and fast-reactor irradiations are also discussed. The results are used to (a) define a threshold fluence above which irradiation effects on fracture toughness of the material are significant, (b) evaluate the potential of neutron embrittlement under LWR operating conditions, and (c) assess the potential effects of voids on fracture toughness.

Chopra, O. K.; Rao, A. S. (Environmental Science Division); (U.S NRC)

2011-05-01

315

Neutron Star Kicks Affected by Standing Accretion Shock Instability for Core-Collapse Supernovae  

NASA Astrophysics Data System (ADS)

We investigate a proto-neutron star kick velocity estimated from kinetic momentum of a flow around the proto-neutron star after the standing accretion shock instability grows. In this study, ten different types of random perturbations are imposed on the initial flow for each neutrino luminosity. We found that the kick velocities of proto-neutron star are widely distributed from 40 km s-1 to 180 km s-1 when the shock wave reaches 2000 km away from the center of the star. The average value of kick velocity is 115 km s-1, whose value is smaller than the observational ones. The kick velocities do not depend on the neutrino luminosity.

Nakano, Wakana Iwakami; Kotake, Kei; Ohnishi, Naofumi; Yamada, Shoichi; Sawada, Keisuke

2012-09-01

316

MLA fiber injection for a square core fiber optic beam delivery system: design versus prototype results  

NASA Astrophysics Data System (ADS)

The paper details a square core fiber beam delivery design utilizing a unique micro lens array launch method. The paper includes the resulting performance of a prototype created to verify the design and its stability with an emphasis on homogenization as the fiber is articulated.

Lizotte, Todd; Dickey, Fred

2010-07-01

317

Development of finite element design simulation tool for proximity sensor coils with ferrite cores  

Microsoft Academic Search

In the development of inductive proximity sensors, a great deal of time and effort is spent in the design of the sensor coil, which is typically used with a ferrite core for increased Q (Quality factor). Computer simulation of the sensor coil could shorten this design process by eliminating the need for extensive building and testing of prototypes. Analytical solutions

Frederick W. Hintz; James P. Bobis

1997-01-01

318

Design and experimental tests of a novel neutron spin analyzer for wide angle spin echo spectrometers  

SciTech Connect

This paper describes the design and experimental tests of a novel neutron spin analyzer optimized for wide angle spin echo spectrometers. The new design is based on nonremanent magnetic supermirrors, which are magnetized by vertical magnetic fields created by NdFeB high field permanent magnets. The solution presented here gives stable performance at moderate costs in contrast to designs invoking remanent supermirrors. In the experimental part of this paper we demonstrate that the new design performs well in terms of polarization, transmission, and that high quality neutron spin echo spectra can be measured.

Fouquet, Peter; Farago, Bela; Andersen, Ken H.; Bentley, Phillip M.; Pastrello, Gilles; Sutton, Iain; Thaveron, Eric; Thomas, Frederic [Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex 9 (France); Moskvin, Evgeny [Helmholtzzentrum Berlin, Glienicker Strasse 100, D-14109 Berlin (Germany); Pappas, Catherine [Helmholtzzentrum Berlin, Glienicker Strasse 100, D-14109 Berlin (Germany); Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands)

2009-09-15

319

Design and Rationale for an In Situ Cryogenic Deformation Capability at a Neutron Source  

SciTech Connect

When performed in conjunction with neutron diffraction, in situ loading offers unique insights on microstructural deformation mechanisms. This is by virtue of the penetration and phase sensitivity of neutrons. At Los Alamos National Laboratory room and high temperature (up to 1500 deg. C) polycrystalline constitutive response is modeled using finite element and self-consistent models. The models are compared to neutron diffraction measurements. In doing so the implications of slip and creep to microstructural response have been explored. Recently we have been considering low temperature phenomena. This includes changes in deformation mechanisms such as the increased predilection for twinning over slip. Since this is associated with measurable texture changes as well as microstructural strain effects, it is well suited for study using neutron diffraction. This paper outlines the design and rationale for a cryogenic loading capability that will be used on the Spectrometer for MAterials Research at Temperature and Stress (SMARTS) at the Los Alamos Neutron Science Center (LANSCE)

Livescu, V.; Clausen, B.; Sisneros, T.; Bourke, M.A.M. [Los Alamos National Laboratory, Los Alamos, New Mexico, 87545 (United States); Woodruff, T.R.; Vaidyanathan, R. [University of Central Florida, Orlando, Florida, 32816 (United States); Notardonato, W.U. [NASA Kennedy Space Center, Kennedy Space Center, Florida, 32899 (United States)

2004-06-28

320

Using Analytical Models to Efficiently Explore Hardware Transactional Memory and Multi-Core Co-Design  

Microsoft Academic Search

Transactional memory is emerging as a parallel programming paradigm for multi-core processors. Despite the recent interest in transactional memory, there has been no study to characterize the interaction between hardware transactional memory (HTM) design dimensions and multi-core microarchitecture configuration. In this paper, we investigate the use of analytical modeling techniques to build application-specific performance models for understanding the interaction between

James Poe; Chang-burm Cho; Tao Li

2008-01-01

321

Cyclic fatigue testing of five endodontic post designs supported by four core materials  

Microsoft Academic Search

Purpose. This pilot study examined the cyclic fatigue of five endodontic post systems (AccessPost, Flexi-Flange, Flexi-Post, ParaPost, and Vlock) with four core materials (Tytin silver amalgam, Ti-Core, Ketac-Silver and G-C Miracle Mix).Material and methods. In vitro cyclic fatigue was performed with a machine designed to simulate masticatory fatigue forces. An instantaneous force of 22.2 N (5 pounds) was applied to

Brett I. Cohen; Mark K. Pagnillo; Ira Newman; Barry Lee Musikant; Allan S. Deutsch

1997-01-01

322

Design of coupled power inductors with crossed anisotropy magnetic core for integrated power conversion  

Microsoft Academic Search

Design and partial microfabrication of a coupled power inductor is presented for use in high power-density integrated voltage regulators (IVR). The proposed inductor uses many laminations of uniaxial, high-permeability magnetic material where the orientation of anisotropy between successive laminations is rotated to provide an effectively isotropic core. The high permeability core allows for an inductance density of 200nH\\/mm2, while coupling

Noah Sturcken; Ryan Davies; Cheng Cheng; William E. Bailey; Kenneth L. Shepard

2012-01-01

323

Computational Benchmark Calculations Relevant to the Neutronic Design of the Spallation Neutron Source (SNS)  

SciTech Connect

The Spallation Neutron Source (SNS) will provide an intense source of low-energy neutrons for experimental use. The low-energy neutrons are produced by the interaction of a high-energy (1.0 GeV) proton beam on a mercury (Hg) target and slowed down in liquid hydrogen or light water moderators. Computer codes and computational techniques are being benchmarked against relevant experimental data to validate and verify the tools being used to predict the performance of the SNS. The LAHET Code System (LCS), which includes LAHET, HTAPE ad HMCNP (a modified version of MCNP version 3b), have been applied to the analysis of experiments that were conducted in the Alternating Gradient Synchrotron (AGS) facility at Brookhaven National Laboratory (BNL). In the AGS experiments, foils of various materials were placed around a mercury-filled stainless steel cylinder, which was bombarded with protons at 1.6 GeV. Neutrons created in the mercury target, activated the foils. Activities of the relevant isotopes were accurately measured and compared with calculated predictions. Measurements at BNL were provided in part by collaborating scientists from JAERI as part of the AGS Spallation Target Experiment (ASTE) collaboration. To date, calculations have shown good agreement with measurements.

Gallmeier, F.X.; Glasgow, D.C.; Jerde, E.A.; Johnson, J.O.; Yugo, J.J.

1999-11-14

324

Thermal neutron irradiation field design for boron neutron capture therapy of human explanted liver  

SciTech Connect

The selective uptake of boron by tumors compared to that by healthy tissue makes boron neutron capture therapy (BNCT) an extremely advantageous technique for the treatment of tumors that affect a whole vital organ. An example is represented by colon adenocarcinoma metastases invading the liver, often resulting in a fatal outcome, even if surgical resection of the primary tumor is successful. BNCT can be performed by irradiating the explanted organ in a suitable neutron field. In the thermal column of the Triga Mark II reactor at Pavia University, a facility was created for this purpose and used for the irradiation of explanted human livers. The neutron field distribution inside the organ was studied both experimentally and by means of the Monte Carlo N-particle transport code (MCNP). The liver was modeled as a spherical segment in MCNP and a hepatic-equivalent solution was used as an experimental phantom. In the as-built facility, the ratio between maximum and minimum flux values inside the phantom ({phi}{sub max}/{phi}{sub min}) was 3.8; this value can be lowered to 2.3 by rotating the liver during the irradiation. In this study, the authors proposed a new facility configuration to achieve a uniform thermal neutron flux distribution in the liver. They showed that a {phi}{sub max}/{phi}{sub min} ratio of 1.4 could be obtained without the need for organ rotation. Flux distributions and dose volume histograms were reported for different graphite configurations.

Bortolussi, S.; Altieri, S. [Department of Nuclear and Theoretical Physics, University of Pavia, INFN Section of Pavia, via Bassi 6, 27100 Pavia (Italy)

2007-12-15

325

Thermo-mechanical and neutron lifetime modelling and design of Be pebbles in the neutron multiplier for the LIFE engine  

NASA Astrophysics Data System (ADS)

Concept designs for the laser inertial fusion/fission energy (LIFE) engine include a neutron multiplication blanket containing Be pebbles flowing in a molten salt coolant. These pebbles must be designed to withstand the extreme irradiation and temperature conditions in the blanket to enable a reliable and cost-effective operation of LIFE. In this work, we develop design criteria for spherical Be pebbles on the basis of their thermo-mechanical behaviour under continued neutron exposure. We consider the effects of high fluence and fast fluxes on the elastic, thermal and mechanical properties of nuclear-grade Be. Our results suggest a maximum pebble diameter of 30 mm to avoid tensile failure, coated with an anti-corrosive, high-strength metallic shell to avoid failure by pebble contact. Moreover, we find that the operation temperature must always be kept above 450 °C to enable creep to relax the stresses induced by swelling. Under these circumstances, we estimate the pebble lifetime to be at least 16 months if uncoated, and up to six years when coated. We identify the sources of uncertainty on the properties used and discuss the advantages of new intermetallic beryllides and their use in LIFE's neutron multiplier. To establish Be-pebble lifetimes with improved confidence, reliable experiments to measure irradiation creep must be performed.

DeMange, P.; Marian, J.; Caro, M.; Caro, A.

2009-11-01

326

Thermo-mechanical and neutron lifetime modeling and design of Be pebbles in the neutron multiplier for the LIFE engine  

SciTech Connect

Concept designs for the laser-initiated fusion/fission engine (LIFE) include a neutron multiplication blanket containing Be pebbles flowing in a molten salt coolant. These pebbles must be designed to withstand the extreme irradiation and temperature conditions in the blanket to enable a safe and cost-effective operation of LIFE. In this work, we develop design criteria for spherical Be pebbles on the basis of their thermomechanical behavior under continued neutron exposure. We consider the effects of high fluence/fast flux on the elastic, thermal and mechanical properties of nuclear-grade Be. Our results suggest a maximum pebble diameter of 30 mm to avoid tensile failure, coated with an anti-corrosive, high-strength metallic shell to avoid failure by pebble contact. Moreover, we find that the operation temperature must always be kept above 450 C to enable creep to relax the stresses induced by swelling, which we estimate to be at least 16 months if uncoated and up to six years when coated. We identify the sources of uncertainty on the properties used and discuss the advantages of new intermetallic beryllides and their use in LIFE's neutron multiplier. To establish Be-pebble lifetimes with improved confidence, reliable experiments to measure irradiation creep must be performed.

DeMange, P; Marian, J; de Caro, M S; Caro, A

2009-03-16

327

A novel design approach for a neutron measurement station for burnt fuel  

NASA Astrophysics Data System (ADS)

The design and characterization of a passive neutron measurement station for highly burnt fuel has been undertaken at the Paul Scherrer Institute (PSI). The measurement station aims at the determination of the total neutron emission rate of full-length light water reactor (LWR) fuel rods, as also the corresponding axial distributions. It is intended that the measurement station be introduced into the hot cells available at PSI to allow measuring the neutron emission of spent fuel rods provided by the Swiss nuclear power plants. In addition, the neutron emission of a large set of burnt fuel samples that have been previously characterized by post-irradiation examination (PIE) will be measured, in order to relate neutron emission to the burnup and isotopic composition of different fuel types. The design of the measurement station is presented in this article. A post-processing algorithm is introduced to improve the spatial resolution of the “measured” axial profile. In order to quantify the accuracy of the reconstructed neutron source distribution, a figure-of-merit (FOM) is defined and adapted to the detection procedure. With the optimized measurement station and procedure, it is estimated that the neutron emission distribution of a highly burnt, full-length fuel rod would be measurable with acceptable accuracy in about 20 min.

Dietler, Rodolfo; Hursin, Mathieu; Perret, Gregory; Jordan, Kelly; Chawla, Rakesh

2012-11-01

328

Boiling water neutronic reactor incorporating a process inherent safety design  

DOEpatents

A boiling-water reactor core is positioned within a prestressed concrete reactor vessel of a size which will hold a supply of coolant water sufficient to submerge and cool the reactor core by boiling for a period of at least one week after shutdown. Separate volumes of hot, clean (non-borated) water for cooling during normal operation and cool highly borated water for emergency cooling and reactor shutdown are separated by an insulated wall during normal reactor operation with contact between the two water volumes being maintained at interfaces near the top and bottom ends of the reactor vessel. Means are provided for balancing the pressure of the two volumes at the lower interface zone during normal operation to prevent entry of the cool borated water into the reactor core region, for detecting the onset of excessive power to coolant flow conditions in the reactor core and for detecting low water levels of reactor coolant. Cool borated water is permitted to flow into the reactor core when low reactor coolant levels or excessive power to coolant flow conditions are encountered.

Forsberg, Charles W. (Kingston, TN)

1987-01-01

329

Boiling water neutronic reactor incorporating a process inherent safety design  

DOEpatents

A boiling-water reactor core is positioned within a prestressed concrete reactor vessel of a size which will hold a supply of coolant water sufficient to submerge and cool the reactor core by boiling for a period of at least one week after shutdown. Separate volumes of hot, clean (nonborated) water for cooling during normal operation and cool highly borated water for emergency cooling and reactor shutdown are separated by an insulated wall during normal reactor operation with contact between the two water volumes being maintained at interfaces near the top and bottom ends of the reactor vessel. Means are provided for balancing the pressure of the two water volumes at the lower interface zone during normal operation to prevent entry of the cool borated water into the reactor core region, for detecting the onset of excessive power to coolant flow conditions in the reactor core and for detecting low water levels of reactor coolant. Cool borated water is permitted to flow into the reactor core when low reactor coolant levels or excessive power to coolant flow conditions are encountered.

Forsberg, C.W.

1985-02-19

330

Design and realization of the IP control core in field controllers for LAMOST spectroscopes  

NASA Astrophysics Data System (ADS)

The China-made telescope, LAMOST, consists of 16 spectroscopes to detect stellar spectra via 4000 optical fibers. In each spectroscope, many movable parts work in phase. Those parts are real-time controlled and managed by field controllers based on FPGA. This paper mainly introduces how to use DSP Builder module library in MATLAB / Simulink to construct the IP control core on FPGA chip. This method can also be used to design the control core of PID arithmetic, to carry out arithmetic simulation and generate VHDL language file, as well as to integrate it into SOPC developing environment so as to repeatedly use. In this way, the design period of the control system may be shortened and design process simplified. Finally due to the reversibility and programmability of the IP control core ,a system on a chip for field controllers of spectroscope is realized, which meets astronomical control requirements, providing an effective scheme for embedded system in astronomical instrument applications.

Wang, Jianing; Han, Zhongyi; Zeng, Yizhong; Dai, Songxin; Hu, Zhongwen; Zhu, Yongtian; Wang, Lei; Hou, Yonghui

2010-07-01

331

Implementation of knowledge-based system for iron core inductor design  

Microsoft Academic Search

We describe the implementation of a knowledge-based system for designing iron core inductors. We identify the underlying issues related to the implementation of such a system. We employ a recursive design methodology based on imitating an expert human designer that is suitable for embedding in the knowledge-based system. A hybrid knowledge base, using both frame-based and rule-based paradigms, together with

A. Sadeghian; J. D. Lavers

2004-01-01

332

Design criteria for a self-actuated shutdown system to ensure limitation of core damage. [LMFBR  

SciTech Connect

Safety-based functional requirements and design criteria for a self-actuated shutdown system (SASS) are derived in accordance with LOA-2 success criteria and reliability goals. The design basis transients have been defined and evaluated for the CDS Phase II design, which is a 2550 MWt mixed oxide heterogeneous core reactor. A partial set of reactor responses for selected transients is provided as a function of SASS characteristics such as reactivity worth, trip points, and insertion times.

Deane, N.A.; Atcheson, D.B.

1981-09-01

333

Aperture design and numerical reconstruction technique requirements for high-resolution imaging of neutrons in inertial confinement fusion (ICF)  

Microsoft Academic Search

In Inertial Confinement Factor (ICF) experiments, radiation from compressed core is increasingly reabsorbed. For the largest experiments, the only radiation to escape is the 14 MeV fusion neutrons to which we must turn to learn of the physical processes taking place. The most important parameters are the shape and the size of the compressed core and this involves imaging the

Olivier Delage; Henri H. Arsenault

1998-01-01

334

Conceptual design of a reversed-field pinch fusion neutron source  

SciTech Connect

The conceptual design of an ohmically-heated, reversed-field pinch (RFP) operating with a 5-MWm/sup 2/ steady-state DT fusion neutron wall loading while generating /approximately/100-MW total fusion power is presented. These results are also useful in projecting the development of an economic source of DT neutrons for large-volume (/approximately/10 m/sup 3/) fusion nuclear testing. 6 refs., 4 figs., 5 tabs.

Bathke, C.G.; Krakowski, R.A.; Manzanares, R.G.; Miller, R.L.; Werley, K.A.

1988-01-01

335

Design and testing of a high pressure gas target for fast neutron resonance radiography  

Microsoft Academic Search

A high pressure deuterium gas target has been designed to provide high-flux fast neutrons using the D(d,n)3He reaction for use as a neutron source. The deuterium gas cell holds 4 atm D2 gas at 298 K and is projected to tolerate a beam current of ~50 muA of 3.0 MeV deuterons for 8 hours of continuous use. The high-pressure gas

Whitney L. Raas; Brandon W. Blackburn; Erin Boyd; J M Hall; G. Kohse; R. C. Lanza; B. Rusnak; J. I. W. Watterson

2005-01-01

336

Design of a compact high-power neutron source—The EURISOL converter target  

Microsoft Academic Search

The EURISOL project, a multi-lateral initiative supported by the EU, aims to develop a facility to achieve high yields of isotopes in radioactive beams and extend the variety of these isotopes towards more exotic types.The neutron source at the heart of the projected facility is designed to generate isotopes by fissioning uranium carbide (UC) targets arranged around a 4MW neutron

K. Samec; R. Ž. Milenkovi?; S. Dementjevs; M. Ashrafi-Nik; A. Kalt

2009-01-01

337

Reactor physics design for an epithermal neutron beam at the power burst reactor facility  

Microsoft Academic Search

An epithermal neutron beam facility has been designed for the Power Burst reactor Facility (PBF). The beam will have a broadband epithermal (1.0 eV - 10 keV) spectrum with extraordinary intensity and collimation with minimum fast neutron and gamma contamination. The PBF reactor is located at the Idaho National Engineering Laboratory (INEL) near Idaho Falls, Idaho, USA. This facility has

F. J. Wheeler; B. L. Rushton; D. K. Parsons; D. W. Nigg

1988-01-01

338

Design and optimization of a CCD-neutron radiography detector  

Microsoft Academic Search

Radiography is a method to visualize the inner structure of macroscopic samples. It is based on the principle of the attenuation of radiation passing through matter, depending on the sample material and geometry. Besides the well-known radiographic examinations with X-rays and ?-rays, neutron radiography provides an important endorsement to radiographic examinations in the field of non-destructive testing (NDT), as contrary

S. Koerner; E. Lehmann; P. Vontobel

2000-01-01

339

Flux distribution and core loss calculation for single phase and five limb three phase transformer core designs  

Microsoft Academic Search

This paper presents results of an analytical core loss calculation method developed for single phase and five limb three phase core types. Shown are calculation results of flux distributions, flux density waveshapes, spatial flux density curves and loss distributions in cores other than the 3 phase-3 limb core. The analytical results show that the flux distribution is essentially uniform in

E. G. teNyenhuis; G. F. Mechler; R. S. Girgis

2000-01-01

340

Designing an extended energy range single-sphere multi-detector neutron spectrometer  

NASA Astrophysics Data System (ADS)

This communication describes the design specifications for a neutron spectrometer consisting of 31 thermal neutron detectors, namely Dysprosium activation foils, embedded in a 25 cm diameter polyethylene sphere which includes a 1 cm thick lead shell insert that degrades the energy of neutrons through (n,xn) reactions, thus allowing to extension of the energy range of the response up to hundreds of MeV neutrons. The new spectrometer, called SP2 (SPherical SPectrometer), relies on the same detection mechanism as that of the Bonner Sphere Spectrometer, but with the advantage of determining the whole neutron spectrum in a single exposure. The Monte Carlo transport code MCNPX was used to design the spectrometer in terms of sphere diameter, number and position of the detectors, position and thickness of the lead shell, as well as to obtain the response matrix for the final configuration. This work focuses on evaluating the spectrometric capabilities of the SP2 design by simulating the exposure of SP2 in neutron fields representing different irradiation conditions (test spectra). The simulated SP2 readings were then unfolded with the FRUIT unfolding code, in the absence of detailed pre-information, and the unfolded spectra were compared with the known test spectra. The results are satisfactory and allowed approving the production of a prototypal spectrometer.

Gómez-Ros, J. M.; Bedogni, R.; Moraleda, M.; Esposito, A.; Pola, A.; Introini, M. V.; Mazzitelli, G.; Quintieri, L.; Buonomo, B.

2012-06-01

341

Design and Performance of South Ukraine Nuclear Power Plant Mixed Cores  

SciTech Connect

In 2010, 42 Westinghouse fuel assemblies (WFAs) were loaded into the core of South Ukraine Nuclear Power Plant (SUNPP) Unit 3 after four successful cycles with 6 Westinghouse Lead Test Assemblies. The scope of safety substantiating documents required for the regulatory approval of this mixed core was extended considerably, particularly with development and implementation of new methodologies and 3-D kinetic codes. Additional verification for all employed codes was also performed. Despite the inherent hydraulic non-uniformity of a mixed core, it was possible to demonstrate that all design and operating restrictions for three different types of fuel (TVS-M, TVSA and WFA) loaded in the core were conservatively met. This paper provides the main results from the first year of operation of the core loaded with 42 WFAs, the predicted parameters for the transition and equilibrium cycles with WFAs, comparisons of predicted versus measured core parameters, as well as the acceptable margin evaluation results for reactivity accidents using the 3-D kinetic codes. To date WFA design parameters have been confirmed by operation experience.

Abdullayev, A. M.; Baydulin, V.; Zhukov, A. I.; Latorre, Richard

2011-09-24

342

The design and performance of IceCube DeepCore  

NASA Astrophysics Data System (ADS)

The IceCube neutrino observatory in operation at the South Pole, Antarctica, comprises three distinct components: a large buried array for ultrahigh energy neutrino detection, a surface air shower array, and a new buried component called DeepCore. DeepCore was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking physics data in May 2010. Its location takes advantage of the exceptionally clear ice at those depths and allows it to use the surrounding IceCube detector as a highly efficient active veto against the principal background of downward-going muons produced in cosmic-ray air showers. DeepCore has a module density roughly five times higher than that of the standard IceCube array, and uses photomultiplier tubes with a new photocathode featuring a quantum efficiency about 35% higher than standard IceCube PMTs. Taken together, these features of DeepCore will increase IceCube's sensitivity to neutrinos from WIMP dark matter annihilations, atmospheric neutrino oscillations, galactic supernova neutrinos, and point sources of neutrinos in the northern and southern skies. In this paper we describe the design and initial performance of DeepCore.

Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Allen, M. M.; Altmann, D.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Bay, R.; Bazo Alba, J. L.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H.; Benabderrahmane, M. L.; BenZvi, S.; Berdermann, J.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blumenthal, J.; Boersma, D. J.; Bohm, C.; Bose, D.; Böser, S.; Botner, O.; Brown, A. M.; Buitink, S.; Caballero-Mora, K. S.; Carson, M.; Chirkin, D.; Christy, B.; Clevermann, F.; Cohen, S.; Colnard, C.; Cowen, D. F.; Cruz Silva, A. H.; D'Agostino, M. V.; Danninger, M.; Daughhetee, J.; Davis, J. C.; De Clercq, C.; Degner, T.; Demirörs, L.; Descamps, F.; Desiati, P.; de Vries-Uiterweerd, G.; DeYoung, T.; Díaz-Vélez, J. C.; Dierckxsens, M.; Dreyer, J.; Dumm, J. P.; Dunkman, M.; Eisch, J.; Ellsworth, R. W.; Engdegård, O.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Fedynitch, A.; Feintzeig, J.; Feusels, T.; Filimonov, K.; Finley, C.; Fischer-Wasels, T.; Fox, B. D.; Franckowiak, A.; Franke, R.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Goodman, J. A.; Góra, D.; Grant, D.; Griesel, T.; Groß, A.; Grullon, S.; Gurtner, M.; Ha, C.; Haj Ismail, A.; Hallgren, A.; Halzen, F.; Han, K.; Hanson, K.; Heinen, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Hoffmann, B.; Homeier, A.; Hoshina, K.; Huelsnitz, W.; Hülß, J.-P.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Ishihara, A.; Jacobi, E.; Jacobsen, J.; Japaridze, G. S.; Johansson, H.; Kampert, K.-H.; Kappes, A.; Karg, T.; Karle, A.; Kenny, P.; Kiryluk, J.; Kislat, F.; Klein, S. R.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Koskinen, D. J.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Kroll, G.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Laihem, K.; Landsman, H.; Larson, M. J.; Lauer, R.; Lünemann, J.; Madsen, J.; Marotta, A.; Maruyama, R.; Mase, K.; Matis, H. S.; Meagher, K.; Merck, M.; Mészáros, P.; Meures, T.; Miarecki, S.; Middell, E.; Milke, N.; Miller, J.; Montaruli, T.; Morse, R.; Movit, S. M.; Nahnhauer, R.; Nam, J. W.; Naumann, U.; Nygren, D. R.; Odrowski, S.; Olivas, A.; Olivo, M.; O'Murchadha, A.; Panknin, S.; Paul, L.; Pérez de los Heros, C.; Petrovic, J.; Piegsa, A.; Pieloth, D.; Porrata, R.; Posselt, J.; Price, P. B.; Przybylski, G. T.; Rawlins, K.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Richman, M.; Rodrigues, J. P.; Rothmaier, F.; Rott, C.; Ruhe, T.; Rutledge, D.; Ruzybayev, B.; Ryckbosch, D.; Sander, H.-G.; Santander, M.; Sarkar, S.; Schatto, K.; Schmidt, T.; Schönwald, A.; Schukraft, A.; Schultes, A.; Schulz, O.; Schunck, M.; Seckel, D.; Semburg, B.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Silvestri, A.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Strahler, E. A.; Ström, R.; Stüer, M.; Sullivan, G. W.; Swillens, Q.; Taavola, H.; Taboada, I.; Tamburro, A.; Tepe, A.; Ter-Antonyan, S.; Tilav, S.; Toale, P. A.; Toscano, S.; Tosi, D.; van Eijndhoven, N.; Vandenbroucke, J.; Van Overloop, A.; van Santen, J.; Vehring, M.; Voge, M.; Walck, C.; Waldenmaier, T.; Wallraff, M.; Walter, M.; Weaver, Ch.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebe, K.; Wiebusch, C. H.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Wolf, M.; Wood, T. R.; Woschnagg, K.; Xu, C.; Xu, D. L.; Xu, X. W.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.; Zoll, M.

2012-05-01

343

Probabilistic risk assessment in the design of the Advanced Neutron Source  

Microsoft Academic Search

Probabilistic risk assessment (PRA) has been used extensively in the design of the Advanced Neutron Source (ANS) reactor to safety risk and enhance availability. Design feautures incorporated to minimize risk include submerged primary coolant piping, circulation cooling capability, and dual independent and diverse shutdown systems. The recently completed Level I, Phase 1 PRA shows that the risk dominating event sequence

R. M. Harrington; C. T. Ramsey; R. R. Fullwood

1994-01-01

344

Designing with advanced composites; Report on the European Core Conference, 1st, Zurich, Switzerland, Oct. 20, 21, 1988, Conference Papers  

SciTech Connect

The present conference discusses the development history of sandwich panel construction, production methods and quality assurance for Nomex sandwich panel core papers, the manufacture of honeycomb cores, state-of-the-art design methods for honeycomb-core panels, the Airbus A320 airliner's CFRP rudder structure, and the design tradeoffs encountered in honeycomb-core structures' design. Also discussed are sandwich-construction aircraft cabin interiors meeting new FAA regulations, the use of Nomex honeycomb cores in composite structures, a low-cost manufacturing technique for sandwich structures, and the Starship sandwich panel-incorporating airframe primary structure.

Not Available

1988-01-01

345

Mechanical Design and Analysis of a 200 MHz, Bolt-Together RFQ for the Accelerator Driven Neutron Source.  

National Technical Information Service (NTIS)

A high-yield neutron source to screen sea-land cargo containers for shielded Special Nuclear Materials (SNM) has been designed at LBNL. The Accelerator-Driven Neutron Source (ADNS) uses the D(d,n)3He reaction to create a forward directed neutron beam. Key...

D. Li J. Staples M. Hoff R. Wells S. Virostek

2007-01-01

346

Turbulent Magnetic Field Amplification from Spiral SASI Modes: Implications for Core-Collapse Supernovae and Proto-Neutron Star Magnetization  

SciTech Connect

We extend our investigation of magnetic field evolution in three-dimensional flows driven by the stationary accretion shock instability (SASI) with a suite of higher-resolution idealized models of the post-bounce core-collapse supernova environment. Our magnetohydrodynamic simulations vary in initial magnetic field strength, rotation rate, and grid resolution. Vigorous SASI-driven turbulence inside the shock amplifies magnetic fields exponentially; but while the amplified fields reduce the kinetic energy of small-scale flows, they do not seem to affect the global shock dynamics. The growth rate and final magnitude of the magnetic energy are very sensitive to grid resolution, and both are underestimated by the simulations. Nevertheless our simulations suggest that neutron star magnetic fields exceeding $10^{14}$~G can result from dynamics driven by the SASI, \\emph{even for non-rotating progenitors}.

Endeve, Eirik [ORNL; Cardall, Christian Y [ORNL; Budiardja, Reuben D [ORNL; Beck, Sam [University of Tennessee, Knoxville (UTK); Bejnood, Alborz [ORNL; Toedte, Ross J [ORNL; Blondin, J. M. [North Carolina State University; Mezzacappa, Anthony [ORNL

2012-01-01

347

TURBULENT MAGNETIC FIELD AMPLIFICATION FROM SPIRAL SASI MODES: IMPLICATIONS FOR CORE-COLLAPSE SUPERNOVAE AND PROTO-NEUTRON STAR MAGNETIZATION  

SciTech Connect

We extend our investigation of magnetic field evolution in three-dimensional flows driven by the stationary accretion shock instability (SASI) with a suite of higher-resolution idealized models of the post-bounce core-collapse supernova environment. Our magnetohydrodynamic simulations vary in initial magnetic field strength, rotation rate, and grid resolution. Vigorous SASI-driven turbulence inside the shock amplifies magnetic fields exponentially; but while the amplified fields reduce the kinetic energy of small-scale flows, they do not seem to affect the global shock dynamics. The growth rate and final magnitude of the magnetic energy are very sensitive to grid resolution, and both are underestimated by the simulations. Nevertheless, our simulations suggest that neutron star magnetic fields exceeding 10{sup 14} G can result from dynamics driven by the SASI, even for non-rotating progenitors.

Endeve, Eirik; Mezzacappa, Anthony [Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6354 (United States); Cardall, Christian Y.; Budiardja, Reuben D. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6354 (United States); Beck, Samuel W.; Bejnood, Alborz [Joint Institute for Heavy Ion Research, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6374 (United States); Toedte, Ross J. [National Center for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6354 (United States); Blondin, John M., E-mail: endevee@ornl.gov [Physics Department, North Carolina State University, Raleigh, NC 27695-8202 (United States)

2012-05-20

348

Modeling and design of a reload PWR core for a 48-month fuel cycle  

SciTech Connect

The objective of this research was to use state-of-the-art nuclear and fuel performance packages to evaluate the feasibility and costs of a 48 calendar month core in existing pressurized water reactor (PWR) designs, considering the full range of practical design and economic considerations. The driving force behind this research is the desire to make nuclear power more economically competitive with fossil fuel options by expanding the scope for achievement of higher capacity factors. Using CASMO/SIMULATE, a core design with fuel enriched to 7{sup w}/{sub o} U{sup 235} for a single batch loaded, 48-month fuel cycle has been developed. This core achieves an ultra-long cycle length without exceeding current fuel burnup limits. The design uses two different types of burnable poisons. Gadolinium in the form of gadolinium oxide (Gd{sub 2}O{sub 3}) mixed with the UO{sub 2} of selected pins is sued to hold down initial reactivity and to control flux peaking throughout the life of the core. A zirconium di-boride (ZrB{sub 2}) integral fuel burnable absorber (IFBA) coating on the Gd{sub 2}O{sub 3}-UO{sub 2} fuel pellets is added to reduce the critical soluble boron concentration in the reactor coolant to within acceptable limits. Fuel performance issues of concern to this design are also outlined and areas which will require further research are highlighted.

McMahon, M.V.; Driscoll, M.J.; Todreas, N.E. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1997-05-01

349

Modeling and analysis of core debris recriticality during hypothetical severe accidents in the Advanced Neutron Source Reactor  

SciTech Connect

This paper discusses salient aspects of severe-accident-related recriticality modeling and analysis in the Advanced Neutron Source (ANS) reactor. The development of an analytical capability using the KENO V.A-SCALE system is described including evaluation of suitable nuclear cross-section sets to account for the effects of system geometry, mixture temperature, material dispersion and other thermal-hydraulic conditions. Benchmarking and validation efforts conducted with KENO V.A-SCALE and other neutronic codes against critical experiment data are described. Potential deviations and biases resulting from use of the 16-group Hansen-Roach library are shown. A comprehensive test matrix of calculations to evaluate the threat of a recriticality event in the ANS is described. Strong dependencies on geometry, material constituents, and thermal-hydraulic conditions are described. The introduction of designed mitigative features is described.

Taleyarkhan, R.P.; Kim, S.H.; Slater, C.O.; Moses, D.L.; Simpson, D.B.; Georgevich, V.

1993-05-01

350

Neutronics Analysis of an Open-Cycle High-Impulse Gas Core Reactor Concept.  

National Technical Information Service (NTIS)

A procedure was developed to calculate the critical fuel mass, including the effects of propellant pressure, for coaxial-flow gas-core reactors operating at 196,600 newtons thrust and 4400 seconds specific impulse. Data were generated for a range of cavit...

C. L. Whitmarsh

1972-01-01

351

What makes a protein a protein? Hydrophobic core designs that specify stability and structural properties.  

PubMed Central

Here we describe how the systematic redesign of a protein's hydrophobic core alters its structure and stability. We have repacked the hydrophobic core of the four-helix-bundle protein, Rop, with altered packing patterns and various side chain shapes and sizes. Several designs reproduce the structure and native-like properties of the wild-type, while increasing the thermal stability. Other designs, either with similar sizes but different shapes, or with decreased sizes of the packing residues, destabilize the protein. Finally, overpacking the core with the larger side chains causes a loss of native-like structure. These results allow us to further define the roles of tight residue packing and the burial of hydrophobic surface area in the construction of native-like proteins.

Munson, M.; Balasubramanian, S.; Fleming, K. G.; Nagi, A. D.; O'Brien, R.; Sturtevant, J. M.; Regan, L.

1996-01-01

352

Design study for MOX fuel rod scanner for ATR fuel fabrication. Phase I: Design of active neutron scanner. Phase II: Design of passive neutron scanner. Phase III: Design of passive gamma-ray scanner  

SciTech Connect

An active neutron fuel-rod scanner has been designed for the assay of fissile materials in mixed oxide fuel rods. A {sup 252}Cf source is located at the center of the scanner very near the through-hole for the fuel rods. Spontaneous fission neutrons from the californium are moderated and induce fissions within the passing fuel rod. The rod continues past a combined gamma-ray and neutron shield where delayed gamma rays above 1 MeV are detected. The authors used the Monte Carlo neutron-photon (MCNP) code to design the scanner and review optimum materials and geometries. Applications of the rod scanner include accountability of fissile material for safeguards applications, quality control of the fissile content in a fuel rod, and the verification of reactivity potential for mixed oxide fuels. A passive neutron fuel-rod scanner has been designed for the assay of the plutonium in mixed oxide fuel rods. The {sup 240}Pu-effective is measured by counting the spontaneous fission neutrons using a high-efficiency thermal-neutron detector. This passive neutron detector would be combined with a high-resolution gamma-ray system (HRGS) measurement to obtain the total plutonium from the plutonium isotopic ratios. A passive gamma-ray scanner has been designed for the measurement of the {sup 241}Am and plutonium uniformity in mixed oxide fuel rods. The passive gamma-ray emissions from {sup 241}Am (60 keV) and plutonium (150-400 keV) are used to verify the unformity of the fuel enrichment zones and to check for any pellets that are out of specification. The fuel rod is moved through the interior of an NaI(Tl) or a bismuth germanate detector to measure the passive gamma-ray emissions. A tungsten sleeve collimator is used in the through-hole to improve the pellet-to-pellet spatial resolution. The same detector is used to verify the plutonium uniformity in the pellets with a 13-mm tungsten collimator. The low-resolution passive gamma system would be used in the unattended mode.

Griffith, G.W.; Menlove, H.O.

1997-09-01

353

Production of gamma ray bursts from asymmetric core combustion of magnetized young neutron stars  

NASA Astrophysics Data System (ADS)

Many works in the past have explored the idea that the conversion of hadronic matter into strange quark matter in neutron stars may be an energy source for GRBs (see references in Lugones et al. 2002, Lugones and Horvath 2003). These models addressed essentially spherically symmetric conversions of the whole neutron star rendering isotropic gamma emission. Accumulating observational evidence suggests that at least ''long'' GRBs are strongly asymmetric, jet-like outflows. The ''short'' burst subclass is not obviously asymmetric, and they may actually be spherically symmetric if the sources are close enough. A new potentially important feature recently recognized (Lugones et al. 2002) is that if a conversion to strange quark matter actually begins near the center of a neutron star, the presence of a magnetic field with intensity B ˜ 1013 G (see also Ghezi, de Gouveia Dal Pino & Horvath 2004) will originate a prompt collimated gamma emission, which may be observed as a short, beamed GRB after the recovery of a fraction of the neutrino energy via ? {bar?} ? e+e- ? ??. The calculations show that the neutrino luminosity is ˜ 1053 erg/sec and that the e+e- luminosity is about two orders of magnitude smaller ( tet{Lugones2002grb}). We find that 90 % of the e+e- pairs are injected inside small cylinders located just above the polar caps (with radius ? and height 0.4 R) in a timescale of ?i ? 0.2 s almost independently of the initial temperature. This provides an interesting suitable explanation for the inner engine of short gamma ray bursts.

de Gouveia dal Pino, E. M.; Lugones, G.; Horvath, J. E.; Ghezzi, C. R.

2005-09-01

354

Preliminary shielding analysis in support of the CSNS target station shutter neutron beam stop design  

NASA Astrophysics Data System (ADS)

The construction of China Spallation Neutron Source (CSNS) has been initiated in Dongguan, Guangdong, China. Thus a detailed radiation transport analysis of the shutter neutron beam stop is of vital importance. The analyses are performed using the coupled Monte Carlo and multi-dimensional discrete ordinates method. The target of calculations is to optimize the neutron beamline shielding design to guarantee personal safety and minimize cost. Successful elimination of the primary ray effects via the two-dimensional uncollided flux and the first collision source methodology is also illustrated. Two-dimensional dose distribution is calculated. The dose at the end of the neutron beam line is less than 2.5 ?Sv/h. The models have ensured that the doses received by the hall staff members are below the standard limit required.

Zhang, Bin; Chen, Yi-Xue; Wang, Wei-Jin; Yang, Shou-Hai; Wu, Jun; Yin, Wen; Liang, Tian-Jiao; Jia, Xue-Jun

2011-08-01

355

Conceptual design of a scintillation fiber neutron detector for ? R measurements in ICF  

NASA Astrophysics Data System (ADS)

In implosion experiments at NIF, the areal density (? R) of maximum compression timing will be high ( ~ 1g/cm^2 ). For low temperature deuterium filled capsules, ? R measurements with ion spectroscopy will be difficult because ion stopping will be significant. A downshifted primary neutron counting method is a promising alternative. The neutron-scattering probability in the capsule is proportional to the ? R. The spectrum of neutrons scattered by the specific target nucleus has a characteristic low energy cut off. This enables separate, simultaneous measurements of fuel and pusher ? Rs. For this purpose, the detector should have sufficient sensitivity and dynamic range for low energy neutrons. A lithium-glass scintillation-fiber (LG-SCIFI) is a promising candidate. Details of the detector instrumentation and collimator design will be reported. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Izumi, N.; Lerche, R. A.; Phillips, T. W.; Schmid, G. J.; Moran, M. J.; Hatchett, S. P.; Sangster, T. C.

2001-10-01

356

Coarse-grained parallel genetic algorithm applied to a nuclear reactor core design optimization problem  

Microsoft Academic Search

This work extends the research related to genetic algorithms (GA) in core design optimization problems, which basic investigations were presented in previous work. Here we explore the use of the Island Genetic Algorithm (IGA), a coarse-grained parallel GA model, comparing its performance to that obtained by the application of a traditional non-parallel GA. The optimization problem consists on adjusting several

Cláudio M. N. A. Pereira; Celso M. F. Lapa

2003-01-01

357

Active Learning: Effects of Core Training Design Elements on Self-Regulatory Processes, Learning, and Adaptability  

Microsoft Academic Search

This research describes a comprehensive examination of the cognitive, motivational, and emotional processes underlying active learning approaches, their effects on learning and transfer, and the core training design elements (exploration, training frame, emotion-control) and individual differences (cognitive ability, trait goal orientation, trait anxiety) that shape these processes. Participants (N = 350) were trained to operate a complex computer-based simulation. Exploratory

Bradford S. Bell; Steve W. J. Kozlowski

2008-01-01

358

Design of a Nuclear Magnetic Resonance Fast Field Cycling Air Cored Magnet  

Microsoft Academic Search

A method for the design of a nuclear magnetic resonance fast field cycling air-cored magnet is presented in this paper. General analytic expressions relating the geometric parameters of the magnet with the flux density, the current density and the power losses were obtained. An optimization algorithm based on the thin circular loop coil model to determine the positions of the

Duarte M. Sousa; G. D. Marques; P. J. Sebastiao; A. C. Ribeiro

2007-01-01

359

Design of the Core Elements of the Digital Avionics Information System, Volume III.  

National Technical Information Service (NTIS)

This final technical report presents the design of the Core Elements of Digital Avionics Information System (DAIS). The report is in 10 sections, one for each of the major tasks defined in the contract statement of work. The report is divided into three v...

J. Early J. Hinderer L. A. Chamberlin T. Falconer V. Gylys

1974-01-01

360

Design of the Core Elements of the Digital Avionics Information System, Volume II.  

National Technical Information Service (NTIS)

This final technical report presents the design of the Core Elements of Digital Avionics Information System (DAIS). The report is in 10 sections, one for each of the major tasks defined in the contract statement of work. The report is divided into three v...

J. Early J. Hinderer L. A. Chamberlin T. Falconer V. Gylys

1974-01-01

361

Scan chain design for test time reduction in core-based ICs  

Microsoft Academic Search

The size of the test vector set forms a significant factor in the overall production costs of ICs, as it defines the test application time and the required pin memory size of the test equipment. Large core-based ICs often require a very large test vector set for a high test coverage. This paper deals with the design of scan chains

Joep Aerts; Erik Jan Marinissen

1998-01-01

362

Spring design for use in the core of a nuclear reactor  

DOEpatents

A spring design particularly suitable for use in the core of a nuclear reactor includes one surface having a first material oriented in a longitudinal direction, and another surface having a second material oriented in a transverse direction. The respective surfaces exhibit different amounts of irraditation induced strain.

Willard, Jr., H. James (Bethel Park, PA)

1993-01-01

363

An in vitro investigation of cast post and partial core design  

Microsoft Academic Search

Objectives: Following endodontic therapy, the provision of a cast post and core restoration may be indicated. Many authors advocate retaining sound coronal dentine where possible, improving the resistance to fracture of the endodontically treated tooth. However, there is little conclusive experimental evidence to support this recommendation. This laboratory study was designed to investigate the effect of retained sound coronal dentine

A. Patel; D. L. Gutteridge

1996-01-01

364

Optimized core design and fuel management of a pebble-bed type nuclear reactor  

Microsoft Academic Search

The core design of a pebble-bed type Very High Temperature Reactor (VHTR) is optimized, aiming for an increase of the coolant outlet temperature to 1000 C, while retaining its inherent safety features. The VHTR has been selected by the international Generation IV research initiative as one of the six most promising nuclear reactor concepts that are expected to enter service

B. Boer

2009-01-01

365

Enabling Programmers to Design Efficient Parallel Algorithms for Many-Core Processors  

Microsoft Academic Search

Since the inception of the desktop computer, performance of software has improved at an exponential rate, primarily driven by the steady technological improvements of microprocessors. Due to fundamental physical limitations and power constraints, we are now witnessing a radical change in commodity microprocessor architecture, to multi-core designs. Continued performance now requires the exploitation of concurrency at the algorithmic level. Automatic

David A. Bader

366

A design of ultrasonic compaction tools for metal powder magnetic core of motors  

Microsoft Academic Search

This report presents the metal powder compaction using ultrasonic vibration for the fabrication of a three-dimensionally-shaped magnetic core. First, we describe a design of ultrasonic compaction tools using FEM. Side wall of the sample was ultrasonically excited by a radial vibration of the die, while the upper and lower punches are driven by longitudinal vibrations. Second, we present the results

Shinichi Kikuchi; Daisuke Koyama; Kentaro Nakamura

2008-01-01

367

A Model Checking Approach for Multi-core Time Partitions Design  

Microsoft Academic Search

In many areas of safety-critical applications multiple applications must execute on a common machine without disturbing each other. Thus spatial and temporal isolation of each application must be guaranteed. In this paper we address the temporal isolation aspect which can be tackled using time partitioning. We propose a technique for automated design of multi-core time partitions based on characteristics of

Georgiana Macariu

2010-01-01

368

Game design principles for engaging cooperative play: core mechanics and interfaces for non-mimetic simulation of fire emergency response  

Microsoft Academic Search

Core mechanics are the activities that players repeat to play a game, the central aspects of play constrained by rules. Interfaces mediate play experiences, impacting engagement with core mechanics. We design core mechanics for gathering, integrating, and sharing information, based on team coordination practices of fire emergency responders. We connect these mechanics with interfaces that impact player engagement. Mechanics and

Zachary O. Toups; Andruid Kerne; William Hamilton

2009-01-01

369

Design solutions to minimize iron core loss in synchronous reluctance motor using Preisach model and FEM  

Microsoft Academic Search

This paper deals with an automatic design procedure for the minimization of iron core loss in a synchronous reluctance motor (SynRM). The focus of this paper is the design relative to hysteresis loss on the basis of rotor shape of a SynRM in the same torque density. The coupled finite-element analysis and Preisach model have been used to evaluate the

Jung Ho Lee

2002-01-01

370

Design and Simulation of a Rotating Aperture & Vacuum System for Neutron Imaging  

SciTech Connect

The development of a high-energy (10Mev) neutron imaging system at Lawrence Livermore National Laboratory (LLNL) depends on a precision engineered rotating aperture and vacuum system for generating neutrons that are used for imaging dense objects. This subsystem is part of a larger system which includes a linear accelerator that creates a deuteron beam, a scintillator detector, imaging optics and a high resolution CCD camera. The rotating aperture vacuum system has been successfully simulated and tested. Results show the feasibility of the design and point toward ways to improve the design by minimizing the rotating aperture gap.

Fitsos, P; Hall, J; Rusnak, B; Shen, S

2006-02-27

371

Force analysis of the Advanced Neutron Source control rod drive latch mechanism  

Microsoft Academic Search

The Advanced Neutron Source reactor (ANS), a proposed Department of Energy research reactor currently undergoing conceptual design, will generate a thermal neutron flux approximating 1020 m-2 -s-1. The compact core necessary to produce this flux provides little space for the shim\\/safety control rods, which are located in the central annulus of the core. Without proper control rod drive design, the

B. Damiano

1990-01-01

372

Mechanical design of the prototype H- ion source for the Spallation Neutron Source  

Microsoft Academic Search

The mechanical design of the prototype H- ion source for the Spallation Neutron Source (SNS) is presented. Experience obtained in the ongoing SNS R&D program is being utilized in the current design. The physics design parameters require a 2 MHz RF-driven multicusp ion source operated at 50kW, pulsed (6% duty factor) RF-power. The four major components (plasma-generator, cesium collar, outlet

S. K. Mukherjee; D. Cheng; M. A. Leitner; K. N. Leung; P. A. Luft; R. A. Gough; R. Keller; M. D. Williams

1999-01-01

373

Sensitivity Analysis of Neutron Cross-Sections Considered for Design and Safety Studies of Lfr and SFR Generation IV Systems  

NASA Astrophysics Data System (ADS)

We evaluated the sensitivity of several design and safety parameters with regard to five different nuclear data libraries, JEF2.2, JEFF3.0, ENDF/B-VI.8, JENDL3.2, and JENDL3.3. More specifically, the effective multiplication factor, burn-up reactivity swing and decay heat generation in available LFR and SFR designs were estimated. Monte Carlo codes MCNP and MCB were used in the analyses of the neutronic and burn-up performance of the systems. Thermo-hydraulic safety calculations were performed by the STAR-CD CFD code. For the LFR, ENDF/B-VI.8 and JEF2.2 showed to give a harder neutron spectrum than JEFF3.0, JENDL3.2, and JENDL3.3 data due to the lower inelastic scattering cross-section of lead in these libraries. Hence, the neutron economy of the system becomes more favourable and keff is higher when calculated with ENDF/B-VI.8 and JEF2.2 data. As for actinide cross-section data, the uncertainties in the keff values appeared to be mainly due to 239Pu, 240Pu and 241Am. Differences in the estimated burn-up reactivity swings proved to be significant, for an SFR as large as a factor of three (when comparing ENDF/B-VI.8 results to those of JENDL3.2). Uncertainties in the evaluation of short-term decay heat generation showed to be of the order of several per cent. Significant differences were, understandably, observed between decay heat generation data quoted in literature for LWR-UOX and those calculated for an LFR (U,TRU)O2 spent fuel. A corresponding difference in calculated core parameters (outlet coolant temperature) during protected total Loss-of-Power was evaluated.

Tucek, Kamil; Carlsson, Johan; Wider, Hartmut

2006-04-01

374

Design studies for a high-resolution, transportable neutron radiography/radioscopy system  

SciTech Connect

A preliminary design has been developed for a high-resolution, transportable neutron radiology system (TNRS) concept. The primary system requirement is taken to be a thermal neutron flux of 10[sup 6] n/(cm[sup 2]-sec) with a L/D ratio of 100. The approach is to use an accelerator-driven neutron source, with a radiofrequency quadrupole (RFQ) as the primary accelerator component. Initial concepts for all of the major components of the system have been developed,and selected key parts have been examined further. An overview of the system design is presented, together with brief summaries of the concepts for the ion source, low energy beam transport (LEBT), RFQ, high energy beam transport (HEBT), target, moderator, collimator, image collection, power, cooling, vacuum, structure, robotics, control system, data analysis, transport vehicle, and site support. The use of trade studies for optimizing the TNRS concept are also described.

Gillespie, G.H. [Gillespie (G.H.) and Associates, Inc., Del Mar, CA (United States); Micklich, B.J.; McMichael, G.E. [Argonne National Lab., IL (United States)

1996-09-30

375

Shielding design of a treatment room for an accelerator-based neutron source for BNCT  

SciTech Connect

For several years, research has been ongoing in the Ohio State University (OSU) Nuclear Engineering Program toward the development of an accelerator-based irradiation facility (ANIF) neutron source for boron neutron capture therapy (BNCT). The ANIF, which is planned to be built in a hospital, has been conceptually designed and analyzed. After Qu, an OSU researcher, determined that the shielding design of a 6-MV X-ray treatment room was inadequate to protect personnel from an accelerator neutron source operating at 30 mA, we decided to analyze and determine the shielding requirements of a treatment room for an ANIF. We determined the amount of shielding that would be sufficient to protect facility personnel from excessive radiation exposure caused by operation of the accelerator at 30 mA.

Evans, J.F.; Blue, T.E. [Ohio State Univ., Columbus, OH (United States)

1995-12-31

376

ESS-Bilbao light-ion linear accelerator and neutron source: design and applications  

NASA Astrophysics Data System (ADS)

The baseline design for the ESS-Bilbao light-ion linear accelerator and neutron source has been completed and the normal conducting section of the linac is at present under construction. The machine has been designed to be compliant with ESS specifications following the international guidelines of such project as described in Ref. [1]. The new accelerator facility in Bilbao will serve as a base for support of activities on accelerator physics carried out in Spain and southern Europe in the frame of different ongoing international collaborations. Also, a number of applications have been envisaged in the new Bilbao facility for the outgoing light ion beams as well as from fast neutrons produced by low-energy neutron-capture targets, which are briefly described.

Abad, E.; Arredondo, I.; Badillo, I.; Belver, D.; Bermejo, F. J.; Bustinduy, I.; Cano, D.; Cortazar, D.; de Cos, D.; Djekic, S.; Domingo, S.; Echevarria, P.; Eguiraun, M.; Etxebarria, V.; Fernandez, D.; Fernandez, F. J.; Feuchtwanger, J.; Garmendia, N.; Harper, G.; Hassanzadegan, H.; Jugo, J.; Legarda, F.; Magan, M.; Martinez, R.; Megia, A.; Muguira, L.; Mujika, G.; Muñoz, J. L.; Ortega, A.; Ortega, J.; Perlado, M.; Portilla, J.; Rueda, I.; Sordo, F.; Toyos, V.; Vizcaino, A.

2011-10-01

377

Design status of an intense 14MeV neutron source for cancer therapy  

NASA Astrophysics Data System (ADS)

Design and development of an intense 14MeV neutron source for cancer therapy is in progress at the Institute of Nuclear Research of Lanzhou University. The neutrons from the T(d,n)4He reaction are produced by bombarding a rotating titanium tritide target with a 40mA deuteron beam at 600keV. The designed neutron yield is 8×1012n/s and the maximum dose rate at a 100cm source-to-skin distance is 25cGy/min. The HV terminal, accelerating column and HV power supply are enclosed inside a stainless steel pressure vessel containing 6atm SF6 gas to provide the electrical insulation.

Yao, Ze-En; Su, Tong-Ling; Cheng, Shang-Wen; Jia, Wen-Bao

2002-09-01

378

Design studies for a high-resolution, transportable neutron radiography/radioscopy system  

SciTech Connect

A preliminary design has been developed for a high-resolution, transportable neutron radiology system (TNRS) concept. The primary system requirement is taken to be a thermal neutron flux of 10{sup 6}n/(cm{sup 2}-sec) with a L/D ratio of 100. The approach is to use an accelerator-driven neutron source, with a radiofrequency quadrupole (RFQ) as the primary accelerator component. Initial concepts for all of the major components of the system have been developed, and selected key parts have been examined further. An overview of the system design is presented, together with brief summaries of the concepts for the ion source, low energy beam transport (LEBT), RFQ, high energy beam transport (HEBT), target, moderator, collimator, image collection, power, cooling, vacuum, structure, robotics, control system, data analysis, transport vehicle, and site support. The use of trade studies for optimizing the TNRS concept are also described. {copyright} {ital 1997 American Institute of Physics.}

Gillespie, G.H. [G. H. Gillespie Associates, Inc., P.O. Box 2961, Del Mar, California 92014 (United States); Micklich, B.J.; McMichael, G.E. [Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439 (United States)

1997-02-01

379

Transport properties of degenerate electrons in neutron star envelopes and white dwarf cores  

Microsoft Academic Search

New calculations of the thermal and electrical electron conductivities are\\u000aperformed for a broad range of physical parameters typical for envelopes of\\u000aneutron stars and cores of white dwarfs. We consider stellar matter composed of\\u000aastrophysically important chemical elements from H to Fe in the density range\\u000afrom 10^2-10^4 g\\/ccm up to 10^7-10^{10} g\\/ccm, where atoms are fully ionized\\u000aand

A. Y. Potekhin; D. A. Baiko; P. Haensel; D. G. Yakovlev

1999-01-01

380

Design of an energy-independent spherical-type neutron dose monitor  

NASA Astrophysics Data System (ADS)

The thickness of a spherical-type neutron dose monitor has been optimized in order to obtain improved dose response compared to that of existing instruments. The monitor structure includes four layers of the spherical shell. The outermost layer is composed of a poly-methyl methacrylate (PMMA) shell. A boron nitride shell is used as the second layer while two polyethylene shells are used as the third and the core layers. Twelve radial directional thermo-luminescent detectors (TLD) detectors are arranged between the layers at two different depths and one in the center. Considering the reaction rate of 6Li(n,?) T for the TLD detectors, a series of calculations were performed using MCNP5 by varying the thickness of the layers. Neutron cross-section libraries based on JENDL-3.3 were applied for the calculations. To evaluate the dose response of the monitor, the spectrum of the D2O-moderated 252Cf source was used as mentioned in ISO 8529. The monitor is sensitive to measurements of three different energy groups at three depths of the moderator. The neutron dose was calculated from the responses of a linear combination of TLD group detectors. The dose response was improved and well agree with expected dose, H*(10), compared to that of existing instruments, especially for intermediate energies of neutrons. The total ambient dose equivalent was varied only 3% for two different incident directions, hence the direction distribution was found small for dose measurement.

Bhuiya, Sariful Haque; Yamanishi, Hirokuni; Uda, Tatsuhiko

2009-08-01

381

The design and installation of a core discharge monitor for CANDU-type reactors  

SciTech Connect

A new type of surveillance systems that monitors neutron and gamma radiation in a reactor containment is being installed at the Ontario Hydro Darlington Nuclear Generating Station A, Unit 2. Unlike video or film surveillance that monitors mechanical motion, this system measures fuel-specific radiation emanating from irradiated fuel as it is pushed from the core of CANDU-type reactors. Proof-of-principle measurements have been carried out at Bruce Nuclear Generating Station A, Unit 3. The system uses ({gamma},n) threshold detectors and ionization detectors. A microprocessor-based electronics package, GRAND-II (Gamma Ray and Neutron Detector electronics package), provides detector bias, preamplifier power, and signal processing. Firmware in the GRAND-2 controls the surveillance activities, including data acquisition and a level of detector authentication, and it handles authenticated communication with a central data logging computer. Data from the GRAND-II are transferred to an MS-DOS-compatible computer and stored. These data are collected and reviewed for fuel-specific radiation signatures from the primary detector and proper ratios of signals from secondary detectors. 5 figs.

Halbig, J.K. (Los Alamos National Lab., NM (USA)); Monticone, A.C.; Ksiezak, L. (International Atomic Energy Agency, Vienna (Austria)); Smiltnieks, V. (International Atomic Energy Agency, Toronto, ON (Canada). Regional Office)

1990-01-01

382

Age-dependent, probabilistic fracture mechanics estimate of ANS (advanced neutron source) large LOCAs for several design options  

Microsoft Academic Search

The advanced neutron source (ANS) research reactor being designed at Oak Ridge National Laboratory for the 1990s will be the world's best source of low-energy neutrons for materials studies, physics research, transplutonium production, and radiation effects. Probabilistic risk analysis (PRA) is being used as one of the tools for safe design optimization. One of the dominant accident initiators in the

Fullwood

1989-01-01

383

A low overhead design for testability and test generation technique for core-based systems-on-a-chip  

Microsoft Academic Search

In a fundamental paradigm shift in system design, entire systems are being built on a single chip, using multiple embedded cores. Though the newest system design methodology has several advantages in terms of time-to-market and system cost, testing such core-based systems is difficult, mainly due to the problem of justifying test sequences at the inputs of a core embedded deep

Indradeep Ghosh; Niraj K. Jha; Sujit Dey

1999-01-01

384

A CONCEPTUAL DESIGN STUDY OF SUPERCONDUCTING PROTON LINEAR ACCELERATOR FOR NEUTRON SCIENCE PROJECT  

Microsoft Academic Search

The Neutron Science Project (NSP) at Japan Atomic Energy Research Institute (JAERI) calls for an 8MW cw and pulsed proton linac. The current JAERI design proposes a superconducting proton linac for the energy range from 100MeV to 1.5GeV. Here, the present linac structure and the beam simulation are described.

Y. Honda; K. Hasegawa; N. Ouchi; J. Kusano; M. Mizumoto

385

Multipurpose Intense 14 MeV Neutron Source at Bratislava: Design Study.  

National Technical Information Service (NTIS)

The present state of design of the multipurpose intense 14 MeV neutron source based on a D exp + ion beam and a metal tritide target is reported. It is essentially a 300 keV electrostatic air insulated accelerator capable to accelerate a deuterium ion bea...

J. Pivarc S. Hlavac J. Kral P. Oblozinsky I. Ribansky

1980-01-01

386

Design of sample carrier for neutron irradiation facility at TRIGA MARK II nuclear reactor  

NASA Astrophysics Data System (ADS)

The objective of this work is to design a sample carrier for neutron irradiation experiment at beam ports of research nuclear reactor, the Reaktor TRIGA PUSPATI (RTP). The sample carrier was designed so that irradiation experiment can be performed safely by researchers. This development will resolve the transferring of sample issues faced by the researchers at the facility when performing neutron irradiation studies. The function of sample carrier is to ensure the sample for the irradiation process can be transferred into and out from the beam port of the reactor safely and effectively. The design model used was House of Quality Method (HOQ) which is usually used for developing specifications for product and develop numerical target to work towards and determining how well we can meet up to the needs. The chosen sample carrier (product) consists of cylindrical casing shape with hydraulic cylinders transportation method. The sample placing can be done manually, locomotion was by wheel while shielding used was made of boron materials. The sample carrier design can shield thermal neutron during irradiation of sample so that only low fluencies fast neutron irradiates the sample.

Abdullah, Y.; Hamid, N. A.; Mansor, M. A.; Ahmad, M. H. A. R. M.; Yusof, M. R.; Yazid, H.; Mohamed, A. A.

2013-06-01

387

Constraints on the design of core-shell resonators of locally resonant acoustic metamaterials  

NASA Astrophysics Data System (ADS)

We perform a parametric study of the analytic model of Liu [Z. Liu , Phys. Rev. B10.1103/PhysRevB.71.014103 71, 014103 (2005)] describing the mechanical response of a core-shell particle to an acoustic excitation in order to help in selecting the constitutive materials and in designing innovative processes of fabrication of downsized core-shell resonators, which are key constituents of locally resonant acoustic metamaterials. We show that the value of the first Lamé coefficient of the material constituting the shell has no marked influence on the value of the resonance frequency of the core-shell resonator, that is, it does not necessarily need to be small for satisfying the condition of subwavelength resonator dimension at resonance. Moreover, we show that the larger the density contrast between the core and the shell and the thinner the shell, the broader is the frequency band over which the effective density of the resonator suspension is negative, but that it is practically useless to decrease the dimensionless shell thickness below 0.6. Finally, we show that the dissipation is also less perceptible the thinner is the shell and the larger is the density contrast. The effect of the density contrast between the core and the shell and of the dissipation on the resonance width are explained by comparing with the harmonic oscillator and the mass-in-mass 1D lattice.

Bos, Lionel; Lukyanova, Lyubov; Wunenburger, Régis

2012-11-01

388

Effects of three bonding systems on the torsional resistance of titanium-reinforced composite cores supported by two post designs  

Microsoft Academic Search

Statement of problem. There are no studies that have investigated the effects of bonding agents on the resistance to torque of a composite core supported by a prefabricated post. Purpose. This study investigated the ability of bonding agents to resist rational forces applied to titanium-reinforced composite cores supported by 2 post designs. Material and methods. Two post designs (AccessPost and

Brett I. Cohen; Mark K. Pagnillo; Ira Newman; Barry Lee Musikant; Allan S. Deutsch

1999-01-01

389

Effects of post-core design and ferrule on fracture resistance of endodontically treated maxillary central incisors  

Microsoft Academic Search

Statement of Problem. Studies concerning the effects of post-core design and ferrule on the fracture resistance of endodontically treated teeth remain controversial. Purpose. The purpose of this study was to investigate in vitro the effects of post-core design and ferrule on the fracture resistance of root canal treated human maxillary central incisors restored with metal ceramic crowns. Material and Methods.

Lu Zhi-Yue; Zhang Yu-Xing

2003-01-01

390

Whole-core neutron transport calculations without fuel-coolant homogenization  

SciTech Connect

The variational nodal method implemented in the VARIANT code is generalized to perform full core transport calculations without spatial homogenization of cross sections at either the fuel-pin cell or fuel assembly level. The node size is chosen to correspond to one fuel-pin cell in the radial plane. Each node is divided into triangular finite subelements, with the interior spatial flux distribution represented by piecewise linear trial functions. The step change in the cross sections at the fuel-coolant interface can thus be represented explicitly in global calculations while retaining the fill spherical harmonics capability of VARIANT. The resulting method is applied to a two-dimensional seven-group representation of a LWR containing MOX fuel assemblies. Comparisons are made of the accuracy of various space-angle approximations and of the corresponding CPU times.

Smith, M. A.; Tsoulfanidis, N.; Lewis, E. E.; Palmiotti, G.; Taiwo, T. A.

2000-02-10

391

Probabilistic risk assessment in the design of the Advanced Neutron Source  

SciTech Connect

Probabilistic risk assessment (PRA) has been used extensively in the design of the Advanced Neutron Source (ANS) reactor to safety risk and enhance availability. Design feautures incorporated to minimize risk include submerged primary coolant piping, circulation cooling capability, and dual independent and diverse shutdown systems. The recently completed Level I, Phase 1 PRA shows that the risk dominating event sequence initiator is now blockage; a program to minimize this identified risk is described.

Harrington, R.M.; Ramsey, C.T. [Oak Ridge National Lab., TN (United States); Fullwood, R.R. [Brookhaven National Lab., Upton, NY (United States)

1994-09-01

392

Design and Operating Characteristics of a Lead-lined Hexagonal Neutron-Multiplicity Counter  

Microsoft Academic Search

A high-efficiency Hexagonal Neutron-Multiplicity Counter (HNMC) has been developed for measurement of non-contact handleable power plant decommissioning and dismantling wastes. The HNMC counter was originally designed for nuclear stockpile safeguards measurements, but the unique challenges of the present application required significant adaptations to the design. The counter consists of six detector modules, each containing two parallel rows of 11 He-3

W. F. Mueller; S. Croft; R. D. McElroy; R. Venkataraman; H. Zhu

2006-01-01

393

The reversed-field-pinch (RFP) fusion neutron source: A conceptual design  

SciTech Connect

The conceptual design of an ohmically heated, reversed-field pinch (RFP) operating at /approximately/5-MW/m/sup 2/ steady-state DT fusion neutron wall loading and /approximately/124-MW total fusion power is presented. These results are useful in projecting the development of a cost effective, low input power (/approximately/206 MW) source of DT neutrons for large-volume (/approximately/10 m/sup 3/), high-fluence (3.4 MW yr/m/sup 2/) fusion nuclear materials and technology testing. 19 refs., 15 figs., 9 tabs.

Bathke, C.G.; Krakowski, R.A.; Miller, R.L.; Werley, K.A.

1989-01-01

394

Physics Analyses in the Design of the HFIR Cold Neutron Source  

SciTech Connect

Physics analyses have been performed to characterize the performance of the cold neutron source to be installed in the High Flux Isotope Reactor at the Oak Ridge National Laboratory in the near future. This paper provides a description of the physics models developed, and the resulting analyses that have been performed to support the design of the cold source. These analyses have provided important parametric performance information, such as cold neutron brightness down the beam tube and the various component heat loads, that have been used to develop the reference cold source concept.

Bucholz, J.A.

1999-09-27

395

Hardware-Software Co-design of QRD-RLS Algorithm with Microblaze Soft Core Processor  

NASA Astrophysics Data System (ADS)

This paper presents the implementation of QR Decomposition based Recursive Least Square (QRD-RLS) algorithm on Field Programmable Gate Arrays (FPGA). The design is based on hardware-software co-design. The hardware part consists of a custom peripheral that solves the part of the algorithm with higher computational costs and the software part consists of an embedded soft core processor that manages the control functions and rest of the algorithm. The use of Givens Rotation and Systolic Arrays make this architecture suitable for FPGA implementation. Moreover, the speed and flexibility of FPGAs render them viable for such computationally intensive application. The system has been implemented on Xilinx Spartan 3E FPGA with Microblaze soft core processor using Embedded Development Kit (EDK). The paper also presents the implementation results and their analysis.

Lodha, Nupur; Rai, Nivesh; Dubey, Rahul; Venkataraman, Hrishikesh

396

Design and Calibration of a High-Precision Density Gauge for Firn and Ice Cores  

NASA Astrophysics Data System (ADS)

The Maine Automated Density Gauge Experiment (MADGE) is a field deployable gamma-ray density gauging instrument designed to provide high resolution (3.3 mm) and high precision (±0.004 g cm-3) density profiles of polar firn and ice cores at a typical throughput of 1.5 m h-1. The resulting density profiles are important in ice sheet mass balance and paleoclimate studies, as well as the modeling electromagnetic wave propagation in firn and ice for remote sensing and ground penetrating radar applications. This study describes the design (optimal gamma-ray energy selection, measurement uncertainty analysis, dead-time corrections) and calibration (mass-attenuation coefficient and absolute density calibrations) of the instrument, and discusses the results of additional experiments to verify the calculated measurement uncertainty. Data collected from firn cores drilled on the recent 2006-2007 U.S. Internation Trans-Antarctic Scientific Expedition are also shown and discussed.

Breton, Daniel; Hamilton, Gordon

2009-10-01

397

Design of broadband dispersion compensating fiber with the small core photonic crystal fiber  

NASA Astrophysics Data System (ADS)

This paper has presented a design of dispersion compensating fiber with small core photonic crystal fiber (PCF) based on pure silica. The designed small core PCF can be controlled the dispersion properties in terms of the structural parameters, the pitch ? and the air-filling fraction d/?. The negative chromatic dispersion coefficient can be achieved - 586.5ps/(nm.km) at ?=1550nm with ?=0.9?m and d/?=0.9. This kind of PCF can be used for broadband dispersion compensation in S+C+L band (1460-1565nm) and the chromatic dispersion coefficient is lower than -450ps/(nm.km) in S+C+L band. It can realize the dispersion slope compensation because that it exhibits a negative dispersion slope.

Wu, Ming; Liu, Hairong; Huang, Dexiu; Tong, Weijun; Wei, Huifeng

2007-11-01

398

Preliminary design report for SCDAP/RELAP5 lower core plate model  

SciTech Connect

The SCDAP/RELAP5 computer code is a best-estimate analysis tool for performing nuclear reactor severe accident simulations. Under primary sponsorship of the US Nuclear Regulatory Commission (NRC), Idaho National Engineering and Environmental Laboratory (INEEL) is responsible for overall maintenance of this code and for improvements for pressurized water reactor (PWR) applications. Since 1991, Oak Ridge National Laboratory (ORNL) has been improving SCDAP/RELAP5 for boiling water reactor (BWR) applications. The RELAP5 portion of the code performs the thermal-hydraulic calculations for both normal and severe accident conditions. The structures within the reactor vessel and coolant system can be represented with either RELAP5 heat structures or SCDAP/RELAP5 severe accident structures. The RELAP5 heat structures are limited to normal operating conditions (i.e., no structural oxidation, melting, or relocation), while the SCDAP portion of the code is capable of representing structural degradation and core damage progression that can occur under severe accident conditions. DCDAP/RELAP5 currently assumes that molten material which leaves the core region falls into the lower vessel head without interaction with structural materials. The objective of this design report is to describe the modifications required for SCDAP/RELAP5 to treat the thermal response of the structures in the core plate region as molten material relocates downward from the core, through the core plate region, and into the lower plenum. This has been a joint task between INEEL and ORNL, with INEEL focusing on PWR-specific design, and ORNL focusing upon the BWR-specific aspects. Chapter 2 describes the structures in the core plate region that must be represented by the proposed model. Chapter 3 presents the available information about the damage progression that is anticipated to occur in the core plate region during a severe accident, including typical SCDAP/RELAP5 simulation results. Chapter 4 provides a description of the implementation of the recommended model and Chapter 5 discusses the testing which could be done to verify the design and implementation of the model.

Coryell, E.W. [Lockheed Martin Idaho Technologies Co., Idaho Falls, ID (United States). Idaho National Engineering and Environmental Lab.; Griffin, F.P. [Oak Ridge National Lab., TN (United States)

1998-07-01

399

A new design of fission detector for prompt fission neutron investigation  

NASA Astrophysics Data System (ADS)

In this work we report recent achievements in design of twin back-to-back ionization chamber (TIC) for fission fragment (FF) mass and kinetic energy spectroscopy. Correlated FF kinetic energies, their masses and the angle of the fission axes in 3D Cartesian coordinates can be determined from analysis of the heights and shapes of the pulses induced by the fission fragments on the anodes of TIC. Anodes of TIC were designed as consisting of isolated strips each having independent electronic circuitry and special multi-channel pulse processing apparatus. Mathematical algorithms were provided along with formulae derived for fission axis angles determination. It was shown how the point of fission fragments origin on the target plane may be determined using the same measured data. The last feature made the TIC a rather powerful tool for prompt fission neutron (PFN) emission investigation in event by event analysis of individual fission reactions from non point fissile source. Position sensitive neutron induced fission detector for neutron imaging applications with both thermal and low energy neutrons was found as another possible implementation of the designed TIC.

Zeynalov, Sh.; Zeynalova, O.; Nazarenko, M. A.; Hambsch, F.-J.; Oberstedt, S.

2012-10-01

400

A Microwave Radiometer for Close Proximity Core Body Temperature Monitoring: Design, Development, and Experimentation  

Microsoft Academic Search

Presented is a radiometric sensor and associated electromagnetic propagation models, developed to facilitate non-invasive core body temperature extraction. The system has been designed as a close-proximity sensor to detect thermal emissions radiated from deep-seated tissue 1 cm – 3 cm inside the human body. The sensor is intended for close proximity health monitoring applications, with potential implications for deployment into

Quenton Bonds

2010-01-01

401

Design optimization of radially magnetized, iron-cored, tubular permanent-magnet machines and drive systems  

Microsoft Academic Search

In this paper we deduce, from analytical field solutions, the influence of leading design parameters on the performance of a radially magnetized, iron-cored, tubular permanent-magnet machine and its drive system. We derive analytical formulas for predicting the open-circuit electromotive force, the thrust force, the iron loss, and the winding resistance and inductances, as well as the converter losses. The force

Jiabin Wang; David Howe

2004-01-01

402

Test Planning and Design Space Exploration in a Core-Based Environment  

Microsoft Academic Search

This paper proposes a comprehensive model for testplanning in a core-based environment. The main contributionof this work is the use of several types of TAMs and theconsideration of different optimization factors (area, pinsand test time) during the global TAM and test schedule definition.This expansion of concerns makes possible an efficientyet fine-grained search in the huge design space ofa reuse-based environment.

Erika Cota; Luigi Carro; Marcelo Lubaszewski; Alex Orailoglu

2002-01-01

403

Conceptual Design Study of 180 MWt Small-Sized Reduced-Moderation Water Reactor Core  

Microsoft Academic Search

Conceptual design of a Small-sized Reduced-Moderation Water Reactor (S-RMWR) core, which has the thermal output of 180 MW, the conversion ratio of 1.0 and the void reactivity coefficient of negative value, has been constructed. S-RMWR is a technology demonstration reactor which also conducts material and fuel testing for commercial use of Reduced-Moderation Water Reactor (RMWR) in large-scale power plants. It

Yoshihiro NAKANO; Tsutomu OKUBO; Sadao UCHIKAWA

2006-01-01

404

Nuclear safety analyses and core design calculations to convert the Texas A & M University Nuclear Science Center reactor to low enrichment uranium fuel. Final report  

SciTech Connect

This project involved performing the nuclear design and safety analyses needed to modify the license issued by the Nuclear Regulatory Commission to allow operation of the Texas A& M University Nuclear Science Center Reactor (NSCR) with a core containing low enrichment uranium (LEU) fuel. The specific type of LEU fuel to be considered was the TRIGA 20-20 fuel produced by General Atomic. Computer codes for the neutronic analyses were provided by Argonne National Laboratory (ANL) and the assistance of William Woodruff of ANL in helping the NSCR staff to learn the proper use of the codes is gratefully acknowledged. The codes applied in the LEU analyses were WIMSd4/m, DIF3D, NCTRIGA and PARET. These codes allowed full three dimensional, temperature and burnup dependent calculations modelling the NSCR core to be performed for the first time. In addition, temperature coefficients of reactivity and pulsing calculations were carried out in-house, whereas in the past this modelling had been performed at General Atomic. In order to benchmark the newly acquired codes, modelling of the current NSCR core with highly enriched uranium fuel was also carried out. Calculated results were compared to both earlier licensing calculations and experimental data and the new methods were found to achieve excellent agreement with both. Therefore, even if an LEU core is never loaded at the NSCR, this project has resulted in a significant improvement in the nuclear safety analysis capabilities established and maintained at the NSCR.

Parish, T.A.

1995-03-02

405

Raman spectroscopic and statistical studies on natural clathrates from the Greenland Ice Core Project ice core, and neutron diffraction studies on synthetic nitrogen clathrates  

Microsoft Academic Search

We present the results of Raman spectroscopic experiments on air clathrates in the GReenland Ice Core Project (GRIP) deep ice core, which differ markedly from previous measurements on the Dye 3 ice core. The N2\\/O2 ratio we observe is much closer to the atmospheric value. This has new implications for the interpretation of gas distributions in ice sheets. Raman spectroscopic

Frank Pauer; Josef Kipfstuhl; Werner F. Kuhs

1997-01-01

406

Comments on ``design optimization of a small-angle neutron scattering spectrometer''  

NASA Astrophysics Data System (ADS)

Margaça, Falca~o, Salgado and Carvahlo [Nucl. Instr. and Meth. A274 (1989) 606, and Proc. Int. Conf. on Neutron Scattering, Grenoble, Physica B156/157 (1989) 608] have recently discussed the design parameters of a small-angle scattering spectrometer. They claim to have shown that the instrument can be optimized for constant angular resolution and a fixed neutron source area, such that the detector count rate is higher than that obtained with a spectrometer optimized for a fixed total length and having the same angular resolution. They also claim that the relative gain in intensity depends upon the size of the neutron emitting surface available to the spectrometer. The initial assumptions made by the authors are too constrained to be generally applicable and therefore misleading conclusions could be drawn, and in fact the equal path length arrangement is optimum.

Mildner, D. F. R.

1990-05-01

407

Design of the neutron imaging pinhole for use at the national ignition facility  

SciTech Connect

The Neutron Imaging (NI) diagnostic is designed to be used at the National Ignition Facility (NIF). This instrument will be used to image both primary (14MeV neutrons) and down scattered (6-8MeV neutrons). The pinhole body sits 225mm from the target, while the scintillator and recording systems are located 28m from the target. The diagnostic uses port 90, 315 and the recording system is located in a specifically built room located outside of switchyard I. The location of the pinhole and the recording system combine to give a magnification of 104. The recording of both the primary and downscattered image is done by recording the image from both the front and back side of the scintillator.

Fatherley, Valerie E [Los Alamos National Laboratory; Day, Robert D [Los Alamos National Laboratory; Garcia, Felix P [Los Alamos National Laboratory; Grim, Gary P [Los Alamos National Laboratory; Oertel, John A [Los Alamos National Laboratory; Wilde, Carl H [Los Alamos National Laboratory; Wilke, Mark D [Los Alamos National Laboratory

2010-01-01

408

Core-crust transition in neutron stars: Predictivity of density developments  

SciTech Connect

The possibility to draw links between the isospin properties of nuclei and the structure of compact stars is a stimulating perspective. In order to pursue this objective on a sound basis, the correlations from which such links can be deduced have to be carefully checked against model dependence. Using a variety of nuclear effective models and a microscopic approach, we study the relation between the predictions of a given model and those of a Taylor density development of the corresponding equation of state: this establishes to what extent a limited set of phenomenological constraints can determine the core-crust transition properties. From a correlation analysis, we show that (a) the transition density {rho}{sub t} is mainly correlated with the symmetry energy slope L, (b) the proton fraction Y{sub p,t} with the symmetry energy and symmetry energy slope (J,L) defined at saturation density, or, even better, with the same quantities defined at {rho}=0.1 fm{sup -3}, and (c) the transition pressure P{sub t} with the symmetry energy slope and curvature (L,K{sub sym}) defined at {rho}=0.1 fm{sup -3}.

Ducoin, Camille; Providencia, Constanca; Vidana, Isaac [CFC, Department of Physics, University of Coimbra, PT-3004-516, Coimbra (Portugal); Margueron, Jerome [Institut de Physique Nucleaire, Universite Paris-Sud, IN2P3-CNRS, FR-91406 Orsay Cedex (France)

2011-04-15

409

Core-crust transition in neutron stars: Predictivity of density developments  

NASA Astrophysics Data System (ADS)

The possibility to draw links between the isospin properties of nuclei and the structure of compact stars is a stimulating perspective. In order to pursue this objective on a sound basis, the correlations from which such links can be deduced have to be carefully checked against model dependence. Using a variety of nuclear effective models and a microscopic approach, we study the relation between the predictions of a given model and those of a Taylor density development of the corresponding equation of state: this establishes to what extent a limited set of phenomenological constraints can determine the core-crust transition properties. From a correlation analysis, we show that (a) the transition density ?t is mainly correlated with the symmetry energy slope L, (b) the proton fraction Yp,t with the symmetry energy and symmetry energy slope (J,L) defined at saturation density, or, even better, with the same quantities defined at ?=0.1 fm-3, and (c) the transition pressure Pt with the symmetry energy slope and curvature (L,Ksym) defined at ?=0.1 fm-3.

Ducoin, Camille; Margueron, Jérôme; Providência, Constança; Vidaña, Isaac

2011-04-01

410

Nuclear data development and shield design for neutrons below 60 MeV  

SciTech Connect

A nuclear data library was created for medium-energy-neutron-transport calculations. The 60-group library includes P/sub 5/ cross sections in standard LASL format for H, B, C, N, O, Si, Fe, and W. The 60-group structure was chosen from a sensitivity analysis of a thick iron shield calculated with a 50-MeV deuteron-on-beryllium neutron source spectrum and a 121-group cross-section set. The library combines processed ENDF/B-IV cross-section data below 20 MeV and higher-energy cross-section parameters calculated with the intranuclear-cascade and evaporation model. A 6-group version of the library is used in the design of a shield-collimator unit for fast-neutron radiotherapy. While the shield is specific for the 50-MeV d/sup +/--Be neutron source presently used in cancer therapy at Texas A and M University, the cross sections and methods developed are applicable to the problems of medium-energy-neutron shielding in general. 28 figures, 21 tables, 132 references.

Wilson, W.B.

1978-02-01

411

Verification of SMART Neutronics Design Methodology by the MCNAP Monte Carlo Code  

Microsoft Academic Search

SMART is a small advanced integral pressurized water reactor (PWR) of 330 MW(thermal) designed for both electricity generation and seawater desalinization. The CASMO-3\\/MASTER nuclear analysis system, a design-basis of Korean PWR plants, has been employed for the SMART core nuclear design and analysis because the fuel assembly (FA) characteristics and reactor operating conditions in temperature and pressure are similar to

Jong Sung Chung; Kyung Jin Shim; Chang Hyo Kim; Chungchan Lee; Sung Quun Zee

2000-01-01

412

General strategy for designing core-shell nanostructured materials for high-power lithium ion batteries.  

PubMed

Because of its extreme safety and outstanding cycle life, Li(4)Ti(5)O(12) has been regarded as one of the most promising anode materials for next-generation high-power lithium-ion batteries. Nevertheless, Li(4)Ti(5)O(12) suffers from poor electronic conductivity. Here, we develop a novel strategy for the fabrication of Li(4)Ti(5)O(12)/carbon core-shell electrodes using metal oxyacetyl acetonate as titania and single-source carbon. Importantly, this novel approach is simple and general, with which we have successfully produce nanosized particles of an olivine-type LiMPO(4) (M = Fe, Mn, and Co) core with a uniform carbon shell, one of the leading cathode materials for lithium-ion batteries. Metal acetylacetonates first decompose with carbon coating the particles, which is followed by a solid state reaction in the limited reaction area inside the carbon shell to produce the LTO/C (LMPO(4)/C) core-shell nanostructure. The optimum design of the core-shell nanostructures permits fast kinetics for both transported Li(+) ions and electrons, enabling high-power performance. PMID:23092272

Shen, Laifa; Li, Hongsen; Uchaker, Evan; Zhang, Xiaogang; Cao, Guozhong

2012-10-25

413

Status of axial heterogeneous liquid-metal fast breeder reactor core design studies and research and development  

SciTech Connect

The current status of axial heterogeneous core (AHC) design development in Japan, which consists of an AHC core design in a pool-type demonstration fast breeder reactor (DFBR) and research and development activities supporting AHC core design, is presented. The DFBR core design objectives developed by The Japan Atomic Power Company include (a) favorable core seismic response, (b) core compactness, (c) high availability, and (d) lower fuel cycle cost. The AHC concept was selected as a reference pool-type DFBR core because it met these objectives more suitably than the homogeneous core (HOC). The AHC core layouts were optimized emphasizing the reduction of the burnup reactivity swing, peak fast fluence, and power peaking. The key performance parameters resulting from the AHC, such as flat axial power/flux distribution, lower peak fast fluence, lower burnup reactivity swing, etc., were evaluated in comparison with the HOC. The critical experiments at the Japan Atomic Energy Research Institute's Fast Critical Assembly facility demonstrate the key AHC performance characteristics. The large AHC engineering benchmark experiments using the zero-power plutonium reactor and the AHC fuel pin irradiation test program using the JOYO reactor are also presented.

Nakagawa, H.; Inagaki, T.; Yoshimi, H.; Shirakata, K.; Watari, Y.; Suzuki, M.; Inoue, K.

1988-11-01

414

Neutron imaging with coded sources: design pitfalls and the implementation of a simultaneous iterative reconstruction technique  

NASA Astrophysics Data System (ADS)

The limitations in neutron flux and resolution (1/D) of current neutron imaging systems can be addressed with a Coded Source Imaging system with magnification (xCSI). More precisely, the multiple sources in an xCSI system can exceed the flux of a single pinhole system for several orders of magnitude, while maintaining a higher 1 / D with the small sources. Moreover, designing for an xCSI system reduces noise from neutron scattering, because the object is placed away from the detector to achieve magnification. However, xCSI systems are adversely affected by correlated noise such as non-uniform illumination of the neutron source, incorrect sampling of the coded radiograph, misalignment of the coded masks, mask transparency, and the imperfection of the system Point Spread Function (PSF). We argue that a model-based reconstruction algorithm can overcome these problems and describe the implementation of a Simultaneous Iterative Reconstruction Technique algorithm for coded sources. Design pitfalls that preclude a satisfactory reconstruction are documented.

Santos-Villalobos, Hector J.; Bingham, Philip R.; Gregor, Jens

2013-02-01

415

Design and operation of a passive neutron monitor for assaying the TRU content of solid wastes  

SciTech Connect

A passive neutron monitor has been designed and built for determining the residual transuranic (TRU) and plutonium content of chopped leached fuel hulls and other solid wastes from spent Fast Flux Test Facility (FFTF) fuel. The system was designed to measure as little as 8 g of plutonium or 88 mg of TRU in a waste package as large as a 208-l drum which could be emitting up to 220,000 R/hr of gamma radiation. For practical purposes, maximum assay times were chosen to be 10,000 sec. The monitor consists of 96 /sup 10/BF/sub 3/ neutron sensitive proportional counting tubes each 5.08 cm in diameter and 183 cm in active length. Tables of neutron emission rates from both spontaneous fission and (..cap alpha..,n) reactions on oxygen are given for all contributing isotopes expected to be present in spent FFTF fuel. Tables of neutron yeilds from isotopic compositions predicted for various exposures and cooling times are also given. Methods of data reduction and sources, magnitude, and control of errors are discussed. Backgrounds and efficiencies have been measured and are reported. A section describing step-by-step operational procedures is included. Guidelines and procedures for quality control and troubleshooting are also given. 13 references, 15 figures, 4 tables.

Brodzinski, R.L.; Brown, D.P.; Rieck, H.G. Jr.; Rogers, L.A.

1984-02-01

416

A new MCNPX PTRAC coincidence capture file capability: a tool for neutron detector design  

SciTech Connect

The existing MCNPX{trademark} PTRAC coincidence capture file allows a full list of neutron capture events to be recorded in any simulated detection medium. The originating event history number (e.g. spontaneous fission events), capture time, location and source particle number are tracked and output to file for post-processing. We have developed a new MCNPX PTRAC coincidence capture file capability to aid detector design studies. New features include the ability to track the isotopes that emitted the detected neutrons as well as induced fission chains in mixed samples before detection (both generation number and isotope). Here, the power of this tool is demonstrated using a detector design that has been developed for the non-destructive assay (NDA) of spent nuclear fuel. Individual capture time distributions have been generated for neutrons originating from Curium-244 source spontaneous fission events and induced fission events in fissile isotopes of interest: namely Plutonium-239, Plutonium-241, and Uranium-235. Through this capability, a full picture for the attribution of neutron capture events in the detector can be simulated.

Evans, Louise G [Los Alamos National Laboratory; Schear, Melissa A [Los Alamos National Laboratory; Hendricks, John S [Los Alamos National Laboratory; Swinhoe, Martyn T [Los Alamos National Laboratory; Tobin, Stephen J [Los Alamos National Laboratory; Croft, Stephen [Los Alamos National Laboratory

2010-12-14

417

A new NCNPX PTRAC coincidence capture file capability: a tool for neutron detector design  

SciTech Connect

The existing Monte Carlo N-Particle (MCNPX) particle tracking (PTRAC) coincidence capture file allows a full list of neutron capture events to be recorded in any simulated detection medium. The originating event history number (e.g. spontaneous fission events), capture time, location and source particle number are tracked and output to file for post-processing. We have developed a new MCNPX PTRAC coincidence capture file capability to aid detector design studies. New features include the ability to track the nuclides that emitted the detected neutrons as well as induced fission chains in mixed samples before detection (both generation number and nuclide that underwent induced fission). Here, the power of this tool is demonstrated using a detector design developed for the non-destructive assay (NDA) of spent nuclear fuel. Individual capture time distributions have been generated for neutrons originating from Curium-244 source spontaneous fission events and induced fission events in fissile nuclides of interest: namely Plutonium-239, Plutonium-241, and Uranium-235. Through this capability, a full picture for the attribution of neutron capture events in the detector can be simulated.

Evans, Louise G [Los Alamos National Laboratory; Schear, Melissa A [Los Alamos National Laboratory; Hendricks`, John S [Los Alamos National Laboratory; Swinhoe, Martyn T [Los Alamos National Laboratory; Tobin, Stephen J [Los Alamos National Laboratory; Croft, Stephen [Los Alamos National Laboratory

2011-01-13

418

A Los Alamos design study for a high-power spallation-neutron-source driver  

SciTech Connect

A design study for an accelerator-driven spallation-neutron source is underway at Los Alamos. The driver, based on the LAMPF facility, produces a 1-MW proton beam and is upgradable to 5 MW. After linear acceleration to full energy, an H-beam is accumulated for approximately I ms in a compressor ring and then extracted to produce an intense proton burst, less than 1 {mu}s long, onto a spallation target system with a 60-Hz cycle rate. The design uses existing infrastructure insofar as possible while maintaining project goals. This paper summarizes the system specifications and design status.

Jason, A.J.; Hardekopf, R.A.; Macek, R.W.; Schriber, S.O.; Thiessen, H.A.; Woods, R.

1993-06-01

419

A Los Alamos design study for a high-power spallation-neutron-source driver  

SciTech Connect

A design study for an accelerator-driven spallation-neutron source is underway at Los Alamos. The driver, based on the LAMPF facility, produces a 1-MW proton beam and is upgradable to 5 MW. After linear acceleration to full energy, an H-beam is accumulated for approximately I ms in a compressor ring and then extracted to produce an intense proton burst, less than 1 [mu]s long, onto a spallation target system with a 60-Hz cycle rate. The design uses existing infrastructure insofar as possible while maintaining project goals. This paper summarizes the system specifications and design status.

Jason, A.J.; Hardekopf, R.A.; Macek, R.W.; Schriber, S.O.; Thiessen, H.A.; Woods, R.

1993-01-01

420

Design of a new time-of-flight small-angle neutron scattering instrument at CPHS  

NASA Astrophysics Data System (ADS)

A new time-of-flight (TOF) small-angle neutron scattering (SANS) diffractometer is to be built at the Compact Pulsed Hadron Source (CPHS) of Tsinghua University, China. This SANS project strives to serve two purposes: its instrumental design, fabrication and optimization will help glean valuable scientific and engineering experiences; and its utilization will help promote fruitful domestic user programs on research of large structures in advanced materials using neutrons.The design draws experiences from other TOF SANS instruments, particularly that of the long-pulse LENS of Indiana University and also considers the source features at CPHS. The design team enjoyed the guidance and assistance from experts through international collaborations. For simultaneous collection of scattering data in the Q-range (˜7×10-3designed to use large area detector (1×1 m2) and broad wavelength bandwidth (1-10 Å) within the first frame. It also pays attention to possible use of optical devices such as neutron guides, focusing lenses and novel detectors.

Huang, T. C.; Gong, H.; Shao, B. B.; Wang, D.; Zhang, X. Z.; Zhang, K.; Wei, J.; Wang, X. W.; Guan, X. L.; Loong, C.-K.; Tao, J. Z.; Zhou, L.; Ke, Y. B.

2012-03-01

421

Session: ANALOG & ELECTRICAL DESIGN Guidelines for Designing Smart and Reusable Analog IP Cores  

Microsoft Academic Search

Every analog designer has to face with the legacy of the traditional analog development, an iterative con- ception process where a single computation loop can last a week. The tremendous gap between the analog and the digital world's methodology of conception is sharper than ever. The reasons should be found both in the lack of automated tools and in the

P. Nguyen Tuong; M.-M. Louerat; A. Greiner

422

Risk minimization using PRA (probabilistic risk analysis) in preconceptual design for the advanced neutron source reactor  

SciTech Connect

The advanced neutron source (ANS) reactor being designed at Oak Ridge National Laboratory (ORNL) for the 1990s will be the worlds best source of low-energy neutrons for materials studies, physics research, transplutonium production, and radiation effects. Probabilistic risk analysis (PRA) is one of the tools being used for safety and operational optimization. The ANS is currently in preconceptual design. This paper presents an overview of the risk based on the initial preconceptual design, which is being modified, based in part on these PRA results. This iterative process of design and PRA evaluation will continue until optimized, after which the US Department of Energy construction cycle may begin. PRA analysis is an important adjunct to the conventional reactor design process. It can provide an estimate of the fuel damage frequency being presented by a design, rank initiators and systems according to their contribution to risk, and identify areas where improvements would be most effective. The PRA is anticipated to continue providing risk-reduction guidance throughout design, construction, and operation.

Fullwood, R.; Shier, W. (Brookhaven National Lab., Upton, NY (USA))

1990-06-01

423

Differential cross section for neutron scattering from {sup 209}Bi at 37 MeV and the weak particle-core coupling  

SciTech Connect

Differential scattering cross-section data have been measured at 43 angles from 11 deg. to 160 deg. for 37-MeV neutrons incident on {sup 209}Bi. The primary motivation for the measurements is to address the scarcity of neutron scattering data above 30 MeV and to improve the accuracy of optical-model predictions at medium neutron energies. The high-statistics measurements were conducted at the China Institute of Atomic Energy using the {sup 3}H(d,n){sup 4}He reaction as the neutron source, a pulsed deuteron beam, and time-of-flight (TOF) techniques. Within the resolution of the TOF spectrometer, the measurements included inelastic scattering components. The sum of elastic and inelastic scattering cross sections was computed in joint optical-model and distorted-wave Born approximation calculations under the assumption of the weak particle-core coupling. The results challenge predictions from well-established spherical optical potentials. Good agreement between data and calculations is achieved at 37 MeV provided that the balance between surface and volume absorption in a recent successful model [A. J. Koning and J. P. Delaroche, Nucl. Phys. A 713, 231 (2003)] is modified, thus suggesting the need for global optical-model improvements at medium neutron energies.

Zhou Zuying; Ruan Xichao; Du Yanfeng; Qi Bujia; Tang Hongqing; Xia Haihong; Walter, R. L.; Braun, R. T.; Howell, C. R.; Tornow, W.; Weisel, G. J.; Dupuis, M.; Delaroche, J. P.; Chen Zemin; Chen Zhenpeng; Chen Yingtang [China Institute of Atomic Energy, P.O. Box 275-46, Beijing 102413 (China); Department of Physics, Duke University, Durham, North Carolina 27708 (United States) and Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708 (United States); CEA, DAM, DIF, F-91297 Arpajon (France); Department of Physics, Tsinghua University, Beijing 100084 (China)

2010-08-15

424

Design, Assembly, and Testing of the Neutron Imaging Lens for the National Ignition Facility  

SciTech Connect

The National Ignition Facility will begin testing DT fuel capsules yielding greater than 10^13 neutrons during 2010. Neutron imaging is an important diagnostic for understanding capsule behavior. Neutrons are imaged at a scintillator after passing through a pinhole. The pixelated, 160-mm square scintillator is made up of ¼ mm diameter rods 50 mm long. Shielding and distance (28 m) are used to preserve the recording diagnostic hardware. Neutron imaging is light starved. We designed a large nine-element collecting lens to relay as much scintillator light as reasonable onto a 75 mm gated microchannel plate (MCP) intensifier. The image from the intensifier’s phosphor passes through a fiber taper onto a CCD camera for digital storage. Alignment of the pinhole and tilting of the scintillator is performed before the relay lens and MCP can be aligned. Careful tilting of the scintillator is done so that each neutron only passes through one rod (no crosstalk allowed). The 3.2 ns decay time scintillator emits light in the deep blue, requiring special glass materials. The glass within the lens housing weighs 26 lbs, with the largest element being 7.7 inches in diameter. The distance between the scintillator and the MCP is only 27 inches. The scintillator emits light with 0.56 NA and the lens collects light at 0.15 NA. Thus, the MCP collects only 7% of the available light. Baffling the stray light is a major concern in the design of the optics. Glass cost considerations, tolerancing, and alignment of this lens system will be discussed.

Malone, Robert M; Fatherley, Valerie E; Frogget, Brent C; Grim, Gary P; Kaufman, Morris I; McGillivray, Kevin D; Oertel, John A; Palagi, Martin J; Skarda, William K; Tibbitts, Aric; Wilde, Carl H

2010-09-01

425

Design and performance of vacuum capable detector electronics for linear position sensitive neutron detectors  

NASA Astrophysics Data System (ADS)

We describe the design and performance of electronics for linear position sensitive neutron detectors. The eight tube assembly requires 10 W of power and can be controlled via digital communication links. The electronics can be used without modification in vacuum. Using a transimpedance amplifier and gated integration, we achieve a highly linear system with coefficient of determinations of 0.9999 or better. Typical resolution is one percent of tube length.

Riedel, R. A.; Cooper, R. G.; Funk, L. L.; Clonts, L. G.

2012-02-01

426

Shielding analysis and design of the KIPT experimental neutron source facility of Ukraine.  

SciTech Connect

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 experimental neutron source facility based on the use of an electron accelerator driven subcritical (ADS) facility [1]. The facility uses the existing electron accelerators of KIPT in Ukraine. The neutron source of the sub-critical 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 the electron energy in the range of 100 to 200 MeV, [2]. The main functions of the facility are the production of medical isotopes and the support of the Ukraine nuclear power industry. Reactor physics experiments and material performance characterization will also be carried out. The subcritical assembly is driven by neutrons generated by the electron beam interactions with the target material. A fraction of these neutrons has an energy above 50 MeV generated through the photo nuclear interactions. This neutron fraction is very small and it has an insignificant contribution to the subcritical assembly performance. However, these high energy neutrons are difficult to shield and they can be slowed down only through the inelastic scattering with heavy isotopes. Therefore the shielding design of this facility is more challenging relative to fission reactors. To attenuate these high energy neutrons, heavy metals (tungsten, iron, etc.) should be used. To reduce the construction cost, heavy concrete with 4.8 g/cm{sup 3} density is selected as a shielding material. The iron weight fraction in this concrete is about 0.6. The shape and thickness of the heavy concrete shield are defined to reduce the biological dose equivalent outside the shield to an acceptable level during operation. At the same time, special attention was give to reduce the total shield mass to reduce the construction cost. The shield design is configured to maintain the biological dose equivalent during operation {le} 0.5 mrem/h inside the subcritical hall, which is five times less than the allowable dose for working forty hours per week for 50 weeks per year. This study analyzed and designed the thickness and the shape of the radial and top shields of the neutron source based on the biological dose equivalent requirements inside the subcritical hall during operation. The Monte Carlo code MCNPX is selected because of its capabilities for transporting electrons, photons, and neutrons. Mesh based weight windows variance reduction technique is utilized to estimate the biological dose outside the shield with good statistics. A significant effort dedicated to the accurate prediction of the biological dose equivalent outside the shield boundary as a function of the shield thickness without geometrical approximations or material homogenization. The building wall was designed with ordinary concrete to reduce the biological dose equivalent to the public with a safety factor in the range of 5 to 20.

Zhong, Z.; Gohar, M. Y. A.; Naberezhnev, D.; Duo, J.; Nuclear Engineering Division

2008-10-31

427

Design of an RFQ-Based Neutron Source for Cargo ContainerInterrogation  

SciTech Connect

An RFQ-based neutron generator system is described that produces pulsed neutrons for the active screening of sea-land cargo containers for the detection of shielded special nuclear materials (SNM).A microwave-driven deuteron source is coupled to an electrostatic LEBT that injects a 40 mA D+ beam into a 6 MeV, 5.1 meter-long 200 MHz RFQ.The RFQ has a unique beam dynamics design and is capable of operating at duty factors of 5 to 10 percent accelerating a D+ time-averaged current of up to 1.5 mA at 5 percent duty factor, including species and transmission loss. The beam is transported through a specially-designed thin window into a 2.5-atmosphere deuterium gas target. A high-frequency dipole magnet is used to scan the beam over the long dimension of the 5by 35 cm target window. The source will deliver a neutron flux of 1 cdot107 n/(cm2s) to the center of an empty cargo container. Details of the ion source, LEBT, RFQ beam dynamics and gas target design are presented.

Staples, John W.; Hoff, M.D.; Kwan, J.W.; Li, D.; Ludewigt, B.A.; Ratti, A.; Virostek, S.P.; Wells, R.P.

2006-08-01

428

Preliminary core design studies for the advanced burner reactor over a wide range of conversion ratios.  

SciTech Connect

A consistent set of designs for 1000 MWt commercial-scale sodium-cooled Advance Burner Reactors (ABR) have been developed for both metal and oxide-fueled cores with conversion ratios from breakeven (CR=1.0) to fertile-free (CR=0.0). These designs are expected to satisfy thermal and irradiation damage limits based on the currently available data. The very low conversion ratio designs require fuel that is beyond the current fuel database, which is anticipated to be qualified by and for the Advanced Burned Test Reactor. Safety and kinetic parameters were calculated, but a safety analysis was not performed. Development of these designs was required to achieve the primary goal of this study, which was to generate representative fuel cycle mass flows for system studies of ABRs as part of the Global Nuclear Energy Partnership (GNEP). There are slight variations with conversion ratio but the basic ABR configuration consists of 144 fuel assemblies and between 9 and 22 primary control assemblies for both the metal and oxide-fueled cores. Preliminary design studies indicated that it is feasible to design the ABR to accommodate a wide range of conversion ratio by employing different assembly designs and including sufficient control assemblies to accommodate the large reactivity swing at low conversion ratios. The assemblies are designed to fit within the same geometry, but the size and number of fuel pins within each assembly are significantly different in order to achieve the target conversion ratio while still satisfying thermal limits. Current irradiation experience would allow for a conversion ratio of somewhat below 0.75. The fuel qualification for the first ABR should expand this experience to allow for much lower conversion ratios and higher bunrups. The current designs were based on assumptions about the performance of high and very high enrichment fuel, which results in significant uncertainty about the details of the designs. However, the basic fuel cycle performance trends such as conversion ratio and mass flow parameters are less sensitive to these parameters and the current results should provide a good basis for static and dynamic system analysis. The conversion ratio is fundamentally a ratio of the macroscopic cross section of U-238 capture to that of TRU fission. Since the microscopic cross sections only change moderately with fuel design and isotopic concentration for the fast reactor, a specific conversion ratio requires a specific enrichment. The approximate average charge enrichment (TRU/HM) is 14%, 21%, 33%, 56%, and 100% for conversion ratios of 1.0, 0.75, 0.50, 0.25, and 0.0 for the metal-fueled cores. The approximate average charge enrichment is 17%, 25%, 38%, 60%, and 100% for conversion ratios of 1.0, 0.75, 0.50, 0.25, and 0.0 for the oxide-fueled core. For the split batch cores, the maximum enrichment will be somewhat higher. For both the metal and oxide-fueled cores, the reactivity feedback coefficients and kinetics parameters seem reasonable. The maximum single control assembly reactivity faults may be too large for the low conversion ratio designs. The average reactivity of the primary control assemblies was increased, which may cause the maximum reactivity of the central control assembly to be excessive. The values of the reactivity coefficients and kinetics parameters show that some values appear to improve significantly at lower conversion ratios while others appear far less favorable. Detailed safety analysis is required to determine if these designs have adequate safety margins or if appropriate design modifications are required. Detailed system analysis data has been generated for both metal and oxide-fueled core designs over the entire range of potential burner reactors. Additional data has been calculated for a few alternative fuel cycles. The systems data has been summarized in this report and the detailed data will be provided to the systems analysis team so that static and dynamic system analyses can be performed.

Hoffman, E. A.; Yang, W. S.; Hill, R. N.; Nuclear Engineering Division

2008-05-05

429

Design and performance of horizontal-type neutron reflectometer SOFIA at J-PARC/MLF  

NASA Astrophysics Data System (ADS)

Neutron reflectometry is a powerful method for investigating the surface and interfacial structures of materials in the spatial range from nanometers to sub-micrometers. At the Japan Proton Accelerator Research Complex (J-PARC), a high-intensity pulsed neutron beam is produced with a proton accelerator at 220kW, which will be upgrad