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Sample records for ceramic pebble beds

  1. Experimental characterization of ceramic pebble beds

    NASA Astrophysics Data System (ADS)

    Zaccari, N.; Aquaro, D.

    2009-04-01

    Several materials have been developed in Europe and Japan for the DEMO reactor that will be tested in ITER. The paper describes a solid breeder for nuclear fusion reactor exploiting ceramic pebbles made of Lithium Orthosilicate (Li 4SiO 4) and Lithium metatinate (Li 2TiO 3), with a diameter ranging between 0.5 mm and 1 mm. The main advantages of the pebbles are resistance to thermal stresses and the possibility to easily fill the complex geometries of the blanket. The results of experimental tests are presented, which enable the determination of the behaviour of single pebbles under compression and the parameters of the pebble beds needed to define their constitutive equations. Several standard tests on samples of pebble beds were performed: triaxial, direct shear and compression. The parameters of the Cam-Clay model were obtained from these tests. This model is normally used to describe soil materials (clay, sand) but in our case was used to simulate the triaxial tests with a finite elements computer code. The numerical results show a good agreement with the theoretical ones. Therefore this model could be used to determine the mechanical behaviour of the solid breeding blanket under normal and accidental conditions.

  2. Preliminary experimental evaluation of thermal conductivity of ceramic pebble beds

    NASA Astrophysics Data System (ADS)

    Aquaro, D.; Lo Frano, R.

    2014-04-01

    This paper illustrates the preliminary experimental tests for determining the effective thermal conductivity of ceramic pebble beds versus temperature and compression strains. Ceramic pebble beds are promising candidates to be used in breeding blankets for nuclear fusion reactor as breeder and neutron multiplier. The tests were performed with an experimental rig, built at the DICI-University of Pisa, which permits to determine the thermal conductivity of pebble beds in steady state conditions, at several temperatures and compression forces. The values of thermal conductivity of pebble beds are obtained as function of a known conductivity of an alumina disc. The assessment of the method has been performed determining the effective thermal conductivity of alumina pebbles beds of different diameters. Void fraction and compression strains are the parameters that mainly influence the variability of the thermal conductivity of the beds.

  3. Characterization of the thermal conductivity for ceramic pebble beds

    NASA Astrophysics Data System (ADS)

    Lo Frano, R.; Aquaro, D.; Scaletti, L.; Olivi, N.

    2015-11-01

    The evaluation of the thermal conductivity of breeder materials is one of the main goals to find the best candidate material for the fusion reactor technology. The aim of this paper is to evaluate experimentally the thermal conductivity of a ceramic material by applying the hot wire method at different temperatures, ranging from 50 to about 800°C. The updated experimental facility, available at the Department of Civil and Industrial Engineering (DICI) of the University of Pisa, used to determine the thermal conductivity of a ceramic material (alumina), will be described along with the measurement acquisition system. Moreover it will be also provided an overview of the current state of art of the ceramic pebble bed breeder thermos-mechanics R&D (e.g. Lithium Orthosilicate (Li4SiO4) and Lithium Metatitanate (Li2TiO3)) focusing on the up-to-date analysis. The methodological approach adopted is articulated in two phase: the first one aimed at the experimental evaluation of thermal conductivity of a ceramic material by means of hot wire method, to be subsequently used in the second phase that is based on the test rig method, through which is measured the thermal conductivity of pebble bed material. In this framework, the experimental procedure and the measured results obtained varying the temperature, are presented and discussed.

  4. Thermo-mechanical testing of Li?ceramic for the helium cooled pebble bed (HCPB) breeding blanket

    NASA Astrophysics Data System (ADS)

    Dell'Orco, G.; Ancona, A.; DiMaio, A.; Simoncini, M.; Vella, G.

    2004-08-01

    The helium cooled pebble bed (HCPB) Test blanket module (TBM) for the DEMO Reactor foresees the utilization of lithiate ceramics as breeder in form of pebble beds. The pebbles are organized in several layers alternatively stacked among couples of cooling plates (CP). ENEA has launched an experimental programme for the out-of-pile thermo-mechanical testing of mock-ups simulating a portion of the HCPB-TBM. The programme foresees the fabrication and testing of different mock-ups, to be tested in the HE-FUS3 facility at ENEA Brasimone. The paper describes the HELICHETTA III campaign carried-out in 2003. In particular, the test section layout, the pebble filling procedure, the experimental set-up and the results of the relevant thermo-mechanical test are herewith presented.

  5. Pebble bed pebble motion: Simulation and Application

    NASA Astrophysics Data System (ADS)

    Cogliati, Joshua J.

    Pebble bed reactors (PBR) have moving graphite fuel pebbles. This unique feature provides advantages, but also means that simulation of the reactor requires understanding the typical motion and location of the granular flow of pebbles. This dissertation presents a method for simulation of motion of the pebbles in a PBR. A new mechanical motion simulator, PEBBLES, efficiently simulates the key elements of motion of the pebbles in a PBR. This model simulates gravitational force and contact forces including kinetic and true static friction. It's used for a variety of tasks including simulation of the effect of earthquakes on a PBR, calculation of packing fractions, Dancoff factors, pebble wear and the pebble force on the walls. The simulator includes a new differential static friction model for the varied geometries of PBRs. A new static friction benchmark was devised via analytically solving the mechanics equations to determine the minimum pebble-to-pebble friction and pebble-to-surface friction for a five pebble pyramid. This pyramid check as well as a comparison to the Janssen formula was used to test the new static friction equations. Because larger pebble bed simulations involve hundreds of thousands of pebbles and long periods of time, the PEBBLES code has been parallelized. PEBBLES runs on shared memory architectures and distributed memory architectures. For the shared memory architecture, the code uses a new O(n) lock-less parallel collision detection algorithm to determine which pebbles are likely to be in contact. The new collision detection algorithm improves on the traditional non-parallel O(n log(n)) collision detection algorithm. These features combine to form a fast parallel pebble motion simulation. The PEBBLES code provides new capabilities for understanding and optimizing PBRs. The PEBBLES code has provided the pebble motion data required to calculate the motion of pebbles during a simulated earthquake. The PEBBLES code provides the ability to

  6. Pebble bed conductors

    SciTech Connect

    Bromberg, L.; Sidorov, M.; Titus, P.

    1996-12-31

    A new type of magnet design is proposed, where the conductor is composed of conducting pebbles in a low-melting temperature conducting matrix. The magnet should have high radiation tolerance. At the end-of-life of the conductor, the pebbles can be circulated out of the magnet after the conducting matrix is molten. Application of this approach to the centerpost in the Low Aspect Ratio Device is discussed. 6 refs., 1 fig.

  7. Pebble-bed pebble motion: Simulation and Applications

    SciTech Connect

    Joshua J. Cogliati; Abderrafi M. Ougouag

    2011-11-01

    Pebble bed reactors (PBR) have moving graphite fuel pebbles. This unique feature provides advantages, but also means that simulation of the reactor requires understanding the typical motion and location of the granular flow of pebbles. This report presents a method for simulation of motion of the pebbles in a PBR. A new mechanical motion simulator, PEBBLES, efficiently simulates the key elements of motion of the pebbles in a PBR. This model simulates gravitational force and contact forces including kinetic and true static friction. It's used for a variety of tasks including simulation of the effect of earthquakes on a PBR, calculation of packing fractions, Dancoff factors, pebble wear and the pebble force on the walls. The simulator includes a new differential static friction model for the varied geometries of PBRs. A new static friction benchmark was devised via analytically solving the mechanics equations to determine the minimum pebble-to-pebble friction and pebble-to-surface friction for a five pebble pyramid. This pyramid check as well as a comparison to the Janssen formula was used to test the new static friction equations. Because larger pebble bed simulations involve hundreds of thousands of pebbles and long periods of time, the PEBBLES code has been parallelized. PEBBLES runs on shared memory architectures and distributed memory architectures. For the shared memory architecture, the code uses a new O(n) lock-less parallel collision detection algorithm to determine which pebbles are likely to be in contact. The new collision detection algorithm improves on the traditional non-parallel O(n log(n)) collision detection algorithm. These features combine to form a fast parallel pebble motion simulation. The PEBBLES code provides new capabilities for understanding and optimizing PBRs. The PEBBLES code has provided the pebble motion data required to calculate the motion of pebbles during a simulated earthquake. The PEBBLES code provides the ability to determine

  8. Preparation of Li2TiO3-Li4SiO4 core-shell ceramic pebbles with enhanced crush load by graphite bed process

    NASA Astrophysics Data System (ADS)

    Xiang, Maoqiao; Zhang, Yingchun; Zhang, Yun; Liu, Shuya; Liu, Hui; Wang, Chaofu; Gu, Cheng

    2015-11-01

    Li4SiO4 and Li2TiO3 have been regarded as the most favored ceramic breeders of the test blanket modules (TBMs). The lithium density of Li4SiO4 is higher than that of Li2TiO3; however, the thermo-mechanical stability of Li2TiO3 is better than that of Li4SiO4. Hence, the biphasic yLi2TiO3-(1-y)Li4SiO4 (y = 25%, 50%, 75%, molar ratio) pebbles were fabricated by a graphite bed process for the next generation of advanced tritium breeder materials. The pebbles with interesting core-shell structure (core: Li2TiO3 and Li4SiO4, shell: Li2TiO3) were fabricated for the first time. The thickness of Li2TiO3 shell can be controlled by sintering time. Crystal structure, microstructure, and mechanical properties of the biphasic pebbles were investigated. The experimental results showed that the core-shell structure improved the crush load dramatically. The average crush load of 50%Li2TiO3-50%Li4SiO4 pebbles sintered at 1100 °C for 5 h was up to104.79 N.

  9. PEBBLES: A COMPUTER CODE FOR MODELING PACKING, FLOW AND RECIRCULATIONOF PEBBLES IN A PEBBLE BED REACTOR

    SciTech Connect

    Joshua J. Cogliati; Abderrafi M. Ougouag

    2006-10-01

    A comprehensive, high fidelity model for pebble flow has been developed and embodied in the PEBBLES computer code. In this paper, a description of the physical artifacts included in the model is presented and some results from using the computer code for predicting the features of pebble flow and packing in a realistic pebble bed reactor design are shown. The sensitivity of models to various physical parameters is also discussed.

  10. Pebble Bed Reactor Dust Production Model

    SciTech Connect

    Abderrafi M. Ougouag; Joshua J. Cogliati

    2008-09-01

    The operation of pebble bed reactors, including fuel circulation, can generate graphite dust, which in turn could be a concern for internal components; and to the near field in the remote event of a break in the coolant circuits. The design of the reactor system must, therefore, take the dust into account and the operation must include contingencies for dust removal and for mitigation of potential releases. Such planning requires a proper assessment of the dust inventory. This paper presents a predictive model of dust generation in an operating pebble bed with recirculating fuel. In this preliminary work the production model is based on the use of the assumption of proportionality between the dust production and the normal force and distance traveled. The model developed in this work uses the slip distances and the inter-pebble forces computed by the authors’ PEBBLES. The code, based on the discrete element method, simulates the relevant static and kinetic friction interactions between the pebbles as well as the recirculation of the pebbles through the reactor vessel. The interaction between pebbles and walls of the reactor vat is treated using the same approach. The amount of dust produced is proportional to the wear coefficient for adhesive wear (taken from literature) and to the slip volume, the product of the contact area and the slip distance. The paper will compare the predicted volume with the measured production rates. The simulation tallies the dust production based on the location of creation. Two peak production zones from intra pebble forces are predicted within the bed. The first zone is located near the pebble inlet chute due to the speed of the dropping pebbles. The second peak zone occurs lower in the reactor with increased pebble contact force due to the weight of supported pebbles. This paper presents the first use of a Discrete Element Method simulation of pebble bed dust production.

  11. Reprocessing of lithium titanate pebbles by graphite bed method

    NASA Astrophysics Data System (ADS)

    Hong, Ming; Zhang, Yingchun; Xiang, Maoqiao; Zhang, Yun

    2015-04-01

    Lithium titanate enriched by 6Li isotope is considered as a candidate of tritium breeding materials for fusion reactors due to its excellent performance. The reuse of burned Li2TiO3 pebbles is an important issue because of the high costs of 6Li-enriched materials and waste considerations. For this purpose, reprocessing of Li2TiO3 pebbles by graphite bed method was developed. Simulative Li2TiO3 pebbles with low-lithium content according to the expected lithium burn-up were fabricated. After that, Li2TiO3 pebbles were re-fabricated with lithium carbonate as lithium additives, in order to gain the composition of lithium titanate with a Li/Ti ratio of 2. The process was optimized to obtain reprocessed Li2TiO3 pebbles that were suitable for reuse as ceramic breeder. Density, porosity, grain size and crushing load of the reprocessed pebbles were characterized. This process did not deteriorate the properties of the reprocessed pebbles and was almost no waste generation.

  12. South Africa slashes pebble-bed cash

    NASA Astrophysics Data System (ADS)

    Cartlidge, Edwin

    2010-04-01

    A novel modular technology that promised to make nuclear power cheaper and safer has suffered a serious blow following withdrawal of support from the South African government. It decided not to renew funding for the pebble-bed modular reactor beyond 31 March this year following a lack of interest from other investors and no customers for its product. The company developing the reactor concept - Pebble Bed Modular Reactor Ltd (PBMR) - is to axe three-quarters of its roughly 800 staff and its chief executive has resigned.

  13. Multiscale Analysis of Pebble Bed Reactors

    SciTech Connect

    Hans Gougar; Woo Yoon; Abderrafi Ougouag

    2010-10-01

    – The PEBBED code was developed at the Idaho National Laboratory for design and analysis of pebble-bed high temperature reactors. The diffusion-depletion-pebble-mixing algorithm of the original PEBBED code was enhanced through coupling with the THERMIX-KONVEK code for thermal fluid analysis and by the COMBINE code for online cross section generation. The COMBINE code solves the B-1 or B-3 approximations to the transport equation for neutron slowing down and resonance interactions in a homogeneous medium with simple corrections for shadowing and thermal self-shielding. The number densities of materials within specified regions of the core are averaged and transferred to COMBINE from PEBBED for updating during the burnup iteration. The simple treatment of self-shielding in previous versions of COMBINE led to inaccurate results for cross sections and unsatisfactory core performance calculations. A new version of COMBINE has been developed that treats all levels of heterogeneity using the 1D transport code ANISN. In a 3-stage calculation, slowing down is performed in 167 groups for each homogeneous subregion (kernel, particle layers, graphite shell, control rod absorber annulus, etc.) Particles in a local average pebble are homogenized using ANISN then passed to the next (pebble) stage. A 1D transport solution is again performed over the pebble geometry and the homogenized pebble cross sections are passed to a 1-d radial model of a wedge of the pebble bed core. This wedge may also include homogeneous reflector regions and a control rod region composed of annuli of different absorbing regions. Radial leakage effects are therefore captured with discrete ordinates transport while axial and azimuthal effects are captured with a transverse buckling term. In this paper, results of various PBR models will be compared with comparable models from literature. Performance of the code will be assessed.

  14. Li ceramic pebbles chemical compatibility with Eurofer samples in fusion relevant conditions

    NASA Astrophysics Data System (ADS)

    Alves, L. C.; Alves, E.; da Silva, M. R.; Paúl, A.; La Barbera, A.

    2004-08-01

    Information on the chemical compatibility between Li ceramic breeders and reactor structural materials is an important issue for fusion reactor technology. In this work, Eurofer samples were placed inside a Li ceramic pebble bed and kept at 600 °C under a reducing atmosphere obtained by the flow of a purging gas (He + 0.1vol.%H 2). Titanate and orthosilicate Li pebble beds were used in the experiments and exposure time ranged from 50 to 2000 h. Surface chemical reactions were investigated with nuclear microprobe techniques. The orthosilicate pebbles present chemical reactions even with the gas mixture, whereas for the samples in close contact with Eurofer there is evidence of Eurofer elemental diffusion into the pebbles and the formation of different types of compounds. Although the titanate pebbles used in the chemical compatibility experiments present surface alterations with increasing surface irregularities along the annealing time, there is no clear indication of Eurofer constituents diffusion.

  15. Characterization of Li2TiO3 pebbles by graphite bed process

    NASA Astrophysics Data System (ADS)

    Hong, Ming; Zhang, Yingchun; Mi, Yingying; Fu, Baojian

    2013-10-01

    Lithium titanate (Li2TiO3) is an important tritium breeder for fusion blanket concepts. In the present study, Li2TiO3 ceramic pebbles were successfully fabricated by a graphite bed process. In this process, graphite bed which had been engraved with spherical pits acted as a casting mould. Droplets of Li2TiO3 suspensions were dispersed into the spherical pits to form pebbles due to the hydrophobic nature of the graphite powder. After drying, green pebbles were sieved and sintered to produce Li2TiO3 pebbles. The fabrication process and properties of the pebbles have been investigated. The experimental results showed that the sphericity of Li2TiO3 pebbles was influenced by solid/liquid ratio and diameter. XRD results demonstrated that Li2TiO3 pebbles with high purity have been prepared by the graphite bed process. SEM revealed that the pebbles have uniform microstructure and adequate open porosity. The Li2TiO3 pebbles sintered at 1150 °C have optimal properties, such as high density (about 90% TD) and high crush load (about 40 N).

  16. Granular Dynamics in Pebble Bed Reactor Cores

    NASA Astrophysics Data System (ADS)

    Laufer, Michael Robert

    This study focused on developing a better understanding of granular dynamics in pebble bed reactor cores through experimental work and computer simulations. The work completed includes analysis of pebble motion data from three scaled experiments based on the annular core of the Pebble Bed Fluoride Salt-Cooled High- Temperature Reactor (PB-FHR). The experiments are accompanied by the development of a new discrete element simulation code, GRECO, which is designed to offer a simple user interface and simplified two-dimensional system that can be used for iterative purposes in the preliminary phases of core design. The results of this study are focused on the PB-FHR, but can easily be extended for gas-cooled reactor designs. Experimental results are presented for three Pebble Recirculation Experiments (PREX). PREX 2 and 3.0 are conventional gravity-dominated granular systems based on the annular PB-FHR core design for a 900 MWth commercial prototype plant and a 16 MWth test reactor, respectively. Detailed results are presented for the pebble velocity field, mixing at the radial zone interfaces, and pebble residence times. A new Monte Carlo algorithm was developed to study the residence time distributions of pebbles in different radial zones. These dry experiments demonstrated the basic viability of radial pebble zoning in cores with diverging geometry before pebbles reach the active core. Results are also presented from PREX 3.1, a scaled facility that uses simulant materials to evaluate the impact of coupled fluid drag forces on the granular dynamics in the PB-FHR core. PREX 3.1 was used to collect first of a kind pebble motion data in a multidimensional porous media flow field. Pebble motion data were collected for a range of axial and cross fluid flow configurations where the drag forces range from half the buoyancy force up to ten times greater than the buoyancy force. Detailed analysis is presented for the pebble velocity field, mixing behavior, and residence time

  17. Survey of Dust Production in Pebble Bed Reactors Cores

    SciTech Connect

    Joshua J. Cogliati; Abderafi M. Ougouag; Javier Ortensi

    2011-06-01

    Graphite dust produced via mechanical wear from the pebbles in a pebble bed reactor is an area of concern for licensing. Both the German pebble bed reactors produced graphite dust that contained activated elements. These activation products constitute an additional source term of radiation and must be taken under consideration during the conduct of accident analysis of the design. This paper discusses the available literature on graphite dust production and measurements in pebble bed reactors. Limited data is available on the graphite dust produced from the AVR and THTR-300 pebble bed reactors. Experiments that have been performed on wear of graphite in pebble-bed-like conditions are reviewed. The calculation of contact forces, which are a key driving mechanism for dust in the reactor, are also included. In addition, prior graphite dust predictions are examined, and future areas of research are identified.

  18. Granular flow in pebble bed reactors: Dust generation and scaling

    SciTech Connect

    Rycroft, C. H.; Lind, T.; Guentay, S.; Dehbi, A.

    2012-07-01

    In experimental prototypes of pebble bed reactors, significant quantities of graphite dust have been observed due to rubbing between pebbles as they flow through the core. At the high temperatures and pressures in these reactors, little data is available to understand the frictional properties of the pebble surfaces, and as a result, the Paul Scherrer Institut (Switzerland) proposes a conceptual design of a scaled-down version of a pebble bed reactor to investigate this issue in detail. In this paper, simulations of granular flow in pebble bed reactors using the discrete-element method are presented. Simulations in the full geometry (using 440,000 pebbles) are compared to those in geometries scaled down by 3:1 and 6:1. The simulations show complex behavior due to discrete pebble packing effects, meaning that pebble flow and dust generation in a scaled-down facility may be significantly different. The differences between velocity profiles, packing geometry, and pebble wear at the different scales are discussed. The results can aid in the design of the prototypical facility to more accurately reproduce the flow in a full-size reactor. (authors)

  19. Contact detection acceleration in pebble flow simulation for pebble bed reactor systems

    SciTech Connect

    Li, Y.; Ji, W.

    2013-07-01

    Pebble flow simulation plays an important role in the steady state and transient analysis of thermal-hydraulics and neutronics for Pebble Bed Reactors (PBR). The Discrete Element Method (DEM) and the modified Molecular Dynamics (MD) method are widely used to simulate the pebble motion to obtain the distribution of pebble concentration, velocity, and maximum contact stress. Although DEM and MD present high accuracy in the pebble flow simulation, they are quite computationally expensive due to the large quantity of pebbles to be simulated in a typical PBR and the ubiquitous contacts and collisions between neighboring pebbles that need to be detected frequently in the simulation, which greatly restricted their applicability for large scale PBR designs such as PBMR400. Since the contact detection accounts for more than 60% of the overall CPU time in the pebble flow simulation, the acceleration of the contact detection can greatly enhance the overall efficiency. In the present work, based on the design features of PBRs, two contact detection algorithms, the basic cell search algorithm and the bounding box search algorithm are investigated and applied to pebble contact detection. The influence from the PBR system size, core geometry and the searching cell size on the contact detection efficiency is presented. Our results suggest that for present PBR applications, the bounding box algorithm is less sensitive to the aforementioned effects and has superior performance in pebble contact detection compared with basic cell search algorithm. (authors)

  20. Experimental and computational investigation of flow of pebbles in a pebble bed nuclear reactor

    NASA Astrophysics Data System (ADS)

    Khane, Vaibhav B.

    The Pebble Bed Reactor (PBR) is a 4th generation nuclear reactor which is conceptually similar to moving bed reactors used in the chemical and petrochemical industries. In a PBR core, nuclear fuel in the form of pebbles moves slowly under the influence of gravity. Due to the dynamic nature of the core, a thorough understanding about slow and dense granular flow of pebbles is required from both a reactor safety and performance evaluation point of view. In this dissertation, a new integrated experimental and computational study of granular flow in a PBR has been performed. Continuous pebble re-circulation experimental set-up, mimicking flow of pebbles in a PBR, is designed and developed. Experimental investigation of the flow of pebbles in a mimicked test reactor was carried out for the first time using non-invasive radioactive particle tracking (RPT) and residence time distribution (RTD) techniques to measure the pebble trajectory, velocity, overall/zonal residence times, flow patterns etc. The tracer trajectory length and overall/zonal residence time is found to increase with change in pebble's initial seeding position from the center towards the wall of the test reactor. Overall and zonal average velocities of pebbles are found to decrease from the center towards the wall. Discrete element method (DEM) based simulations of test reactor geometry were also carried out using commercial code EDEM(TM) and simulation results were validated using the obtained benchmark experimental data. In addition, EDEM(TM) based parametric sensitivity study of interaction properties was carried out which suggests that static friction characteristics play an important role from a packed/pebble beds structural characterization point of view. To make the RPT technique viable for practical applications and to enhance its accuracy, a novel and dynamic technique for RPT calibration was designed and developed. Preliminary feasibility results suggest that it can be implemented as a non

  1. The effects of temperatures on the pebble flow in a pebble bed high temperature reactor

    SciTech Connect

    Sen, R. S.; Cogliati, J. J.; Gougar, H. D.

    2012-07-01

    The core of a pebble bed high temperature reactor (PBHTR) moves during operation, a feature which leads to better fuel economy (online refueling with no burnable poisons) and lower fuel stress. The pebbles are loaded at the top and trickle to the bottom of the core after which the burnup of each is measured. The pebbles that are not fully burned are recirculated through the core until the target burnup is achieved. The flow pattern of the pebbles through the core is of importance for core simulations because it couples the burnup distribution to the core temperature and power profiles, especially in cores with two or more radial burnup 'zones '. The pebble velocity profile is a strong function of the core geometry and the friction between the pebbles and the surrounding structures (other pebbles or graphite reflector blocks). The friction coefficient for graphite in a helium environment is inversely related to the temperature. The Thorium High Temperature Reactor (THTR) operated in Germany between 1983 and 1989. It featured a two-zone core, an inner core (IC) and outer core (OC), with different fuel mixtures loaded in each zone. The rate at which the IC was refueled relative to the OC in THTR was designed to be 0.56. During its operation, however, this ratio was measured to be 0.76, suggesting the pebbles in the inner core traveled faster than expected. It has been postulated that the positive feedback effect between inner core temperature, burnup, and pebble flow was underestimated in THTR. Because of the power shape, the center of the core in a typical cylindrical PBHTR operates at a higher temperature than the region next to the side reflector. The friction between pebbles in the IC is lower than that in the OC, perhaps causing a higher relative flow rate and lower average burnup, which in turn yield a higher local power density. Furthermore, the pebbles in the center region have higher velocities than the pebbles next to the side reflector due to the

  2. The challenges on uncertainty analysis for pebble bed HTGR

    SciTech Connect

    Hao, C.; Li, F.; Zhang, H.

    2012-07-01

    The uncertainty analysis is very popular and important, and many works have been done for Light Water Reactor (LWR), although the experience for the uncertainty analysis in High Temperature Gas cooled Reactor (HTGR) modeling is still in the primary stage. IAEA will launch a Coordination Research Project (CRP) on this topic soon. This paper addresses some challenges for the uncertainty analysis in HTGR modeling, based on the experience of OECD LWR Uncertainty Analysis in Modeling (UAM) activities, and taking into account the peculiarities of pebble bed HTGR designs. The main challenges for HTGR UAM are: the lack of experience, the totally different code packages, the coupling of power distribution, temperature distribution and burnup distribution through the temperature feedback and pebble flow. The most serious challenge is how to deal with the uncertainty in pebble flow, the uncertainty in pebble bed flow modeling, and their contribution to the uncertainty of maximum fuel temperature, which is the most interested parameter for the modular HTGR. (authors)

  3. Pebble Bed Reactor review update. Fiscal year 1979 annual report

    SciTech Connect

    Not Available

    1980-01-01

    Updated information is presented on the Pebble Bed Reactor (PBR) concept being developed in the Federal Republic of Germany for electricity generation and process heat applications. Information is presented concerning nuclear analysis and core performance, fuel cycle evaluation, reactor internals, and safety and availability.

  4. PEBBLE: a two-dimensional steady-state pebble bed reactor thermal hydraulics code

    SciTech Connect

    Vondy, D.R.

    1981-09-01

    This report documents the local implementation of the PEBBLE code to treat the two-dimensional steady-state pebble bed reactor thermal hydraulics problem. This code is implemented as a module of a computation system used for reactor core history calculations. Given power density data, the geometric description in (RZ), and basic heat removal conditions and thermal properties, the coolant properties, flow conditions, and temperature distributions in the pebble fuel elements are predicted. The calculation is oriented to the continuous fueling, steady state condition with consideration of the effect of the high energy neutron flux exposure and temperature history on the thermal conductivity. The coolant flow conditions are calculated for the same geometry as used in the neutronics calculation, power density and fluence data being used directly, and temperature results are made available for subsequent use.

  5. PEBBED ANALYSIS OF HOT SPOTS IN PEBBLE-BED REACTORS

    SciTech Connect

    Abderrafi M. Ougouag; Hans D. Gougar; William K. Terry; Frederik Reitsma; Wessel Joubert

    2005-09-01

    The Idaho National Laboratory’s PEBBED code and simple probability considerations are used to estimate the likelihood and consequences of the accumulation of highly reactive pebbles in the region of peak power in a pebble-bed reactor. The PEBBED code is briefly described, and the logic of the probability calculations is presented in detail. The results of the calculations appear to show that hot-spot formation produces only moderate increases in peak accident temperatures, and no increases at all in normal operating temperatures.

  6. Automated Design and Optimization of Pebble-bed Reactor Cores

    SciTech Connect

    Hans D. Gougar; Abderrafi M. Ougouag; William K. Terry

    2010-07-01

    We present a conceptual design approach for high-temperature gas-cooled reactors using recirculating pebble-bed cores. The design approach employs PEBBED, a reactor physics code specifically designed to solve for and analyze the asymptotic burnup state of pebble-bed reactors, in conjunction with a genetic algorithm to obtain a core that maximizes a fitness value that is a function of user-specified parameters. The uniqueness of the asymptotic core state and the small number of independent parameters that define it suggest that core geometry and fuel cycle can be efficiently optimized toward a specified objective. PEBBED exploits a novel representation of the distribution of pebbles that enables efficient coupling of the burnup and neutron diffusion solvers. With this method, even complex pebble recirculation schemes can be expressed in terms of a few parameters that are amenable to modern optimization techniques. With PEBBED, the user chooses the type and range of core physics parameters that represent the design space. A set of traits, each with acceptable and preferred values expressed by a simple fitness function, is used to evaluate the candidate reactor cores. The stochastic search algorithm automatically drives the generation of core parameters toward the optimal core as defined by the user. The optimized design can then be modeled and analyzed in greater detail using higher resolution and more computationally demanding tools to confirm the desired characteristics. For this study, the design of pebble-bed high temperature reactor concepts subjected to demanding physical constraints demonstrated the efficacy of the PEBBED algorithm.

  7. Nuclear Safeguards Considerations For The Pebble Bed Modular Reactor (PBMR)

    SciTech Connect

    Phillip Casey Durst; David Beddingfield; Brian Boyer; Robert Bean; Michael Collins; Michael Ehinger; David Hanks; David L. Moses; Lee Refalo

    2009-10-01

    High temperature reactors (HTRs) have been considered since the 1940s, and have been constructed and demonstrated in the United Kingdom (Dragon), United States (Peach Bottom and Fort Saint Vrain), Japan (HTTR), Germany (AVR and THTR-300), and have been the subject of conceptual studies in Russia (VGM). The attraction to these reactors is that they can use a variety of reactor fuels, including abundant thorium, which upon reprocessing of the spent fuel can produce fissile U-233. Hence, they could extend the stocks of available uranium, provided the fuel is reprocessed. Another attractive attribute is that HTRs typically operate at a much higher temperature than conventional light water reactors (LWRs), because of the use of pyrolytic carbon and silicon carbide coated (TRISO) fuel particles embedded in ceramic graphite. Rather than simply discharge most of the unused heat from the working fluid in the power plant to the environment, engineers have been designing reactors for 40 years to recover this heat and make it available for district heating or chemical conversion plants. Demonstrating high-temperature nuclear energy conversion was the purpose behind Fort Saint Vrain in the United States, THTR-300 in Germany, HTTR in Japan, and HTR-10 and HTR-PM, being built in China. This resulted in nuclear reactors at least 30% or more thermodynamically efficient than conventional LWRs, especially if the waste heat can be effectively utilized in chemical processing plants. A modern variant of high temperature reactors is the Pebble Bed Modular Reactor (PBMR). Originally developed in the United States and Germany, it is now being redesigned and marketed by the Republic of South Africa and China. The team examined historical high temperature and high temperature gas reactors (HTR and HTGR) and reviewed safeguards considerations for this reactor. The following is a preliminary report on this topic prepared under the ASA-100 Advanced Safeguards Project in support of the NNSA Next

  8. Core Optimization of a Deep-Burn Pebble Bed Reactor

    SciTech Connect

    Brian Boer; Abderrafi M. Ougouag

    2010-06-01

    Achieving a high fuel burnup in the Deep-Burn (DB) pebble bed reactor design, while remaining within the limits for fuel temperature, power peaking and temperature reactivity feedback, is challenging. The high content of Pu and Minor Actinides in the Deep-Burn fuel significantly impacts the thermal neutron energy spectrum as compared to a ’standard’ UO2 fueled core. This can result in power and temperature peaking in the pebble bed core in locally thermalized regions near the graphite reflectors. Furthermore, the interplay of the Pu resonances of the neutron absorption cross sections at low-lying energies can lead to a positive temperature reactivity coefficient for the graphite moderator at certain operating conditions. The DB concept focuses on the destruction of spent fuel transuranics in TRISO coated particle fueled gas-cooled reactors with the aim of a fractional fuel burnup of 60-70% in fissions per initial metal atom (FIMA), using a single-pass, multi in-core fuel (re)cycling scheme. In principle, the DB pebble bed concept employs the same reactor designs as the present low enriched uranium core designs, i.e. the 400 MWth Pebble Bed Modular Reactor (PBMR-400). A Pu and Minor Actinide fueled PBMR-400 design serves as the starting point for a core optimization study. The fuel temperature, power peak, temperature reactivity coefficients, and burnup capabilities of the modified designs are analyzed with the PEBBED code. A code-to-code coupling with the PASTA code allows for the analysis of the TRISO fuel performance for both normal and Loss Of Forced Cooling conditions. An improved core design is sought, maximizing the fuel discharge burnup, while retaining negative temperature reactivity feedback coefficients for the entire temperature range and avoiding high fuel temperatures (fuel failure probabilities).

  9. PEBBLES

    SciTech Connect

    Cogliati, Joshua J.

    2010-09-01

    The PEBBLES code is a computer program designed to simulate the motion, packing and vibration of spheres that undergo various mechanical forces including gravitation, Hooke's law force and various friction forces. The frictional forces include true static friction that allows non-zero angles of repose. Each pebble is individually simulated using the distinct element method. The program outputs various tallies as textual numbers. These tallies include pebble position, pebble angular and linear velocity, force on the wall and between pebbles, probabilities of pebbles moving between different locations, accumulated amount of linear motion between pebbles, and average velocity in different regions of the container.

  10. PEBBLES

    Energy Science and Technology Software Center (ESTSC)

    2010-09-01

    The PEBBLES code is a computer program designed to simulate the motion, packing and vibration of spheres that undergo various mechanical forces including gravitation, Hooke's law force and various friction forces. The frictional forces include true static friction that allows non-zero angles of repose. Each pebble is individually simulated using the distinct element method. The program outputs various tallies as textual numbers. These tallies include pebble position, pebble angular and linear velocity, force on themore » wall and between pebbles, probabilities of pebbles moving between different locations, accumulated amount of linear motion between pebbles, and average velocity in different regions of the container.« less

  11. Analysis of MHD Pressure Drop in the Packed Pebble Bed-Based Blanket for the Fds

    NASA Astrophysics Data System (ADS)

    Wang, Hongyan; Wu, Yican; He, Xiaoxiong

    2003-06-01

    The Fusion-Driven Sub-critical System as a multifunctional hybrid reactor has been investigated in ASIPP. The liquid metal LiPb flow through a packed pebble bed-based blanket is considered to be one of the blanket candidates. In this contribution, the MHD pressure drop of liquid metal flow through the packed pebble bed has been calculated and analyzed under various conditions including (a) the size of the packed pebbles; (b) the ratio of occupied room by the packed pebbles to that of liquid metal; and (c) whether the pebbles surface is insulated or not Furthermore, asymptotic techniques to analyze large Hartmann parameter flow and interaction parameter flow are employed and an analytical model has been developed for the calculations of MHD pressure drop of liquid metal flow in a packed pebble bed. The appropriate method for calculating the MHD effects on the pressure drop through the packed pebble bed-based blanket for the FDS has been presented.

  12. Computational fluid dynamics analysis of aerosol deposition in pebble beds

    NASA Astrophysics Data System (ADS)

    Mkhosi, Margaret Msongi

    2007-12-01

    The Pebble Bed Modular Reactor is a high temperature gas cooled reactor which uses helium gas as a coolant. The reactor uses spherical graphite pebbles as fuel. The fuel design is inherently resistant to the release of the radioactive material up to high temperatures; therefore, the plant can withstand a broad spectrum of accidents with limited release of radionuclides to the environment. Despite safety features of the concepts, these reactors still contain large inventories of radioactive materials. The transport of most of the radioactive materials in an accident occurs in the form of aerosol particles. In this dissertation, the limits of applicability of existing computational fluid dynamics code FLUENT to the prediction of aerosol transport have been explored. The code was run using the Reynolds Averaged Navier-Stokes turbulence models to determine the effects of different turbulence models on the prediction of aerosol particle deposition. Analyses were performed for up to three unit cells in the orthorhombic configuration. For low flow conditions representing natural circulation driven flow, the laminar flow model was used and the results were compared with existing experimental data for packed beds. The results compares well with experimental data in the low flow regime. For conditions corresponding to normal operating of the reactor, analyses were performed using the standard k-ɛ turbulence model. From the inertial deposition results, a correlation that can be used to estimate the deposition of aerosol particles within pebble beds given inlet flow conditions has been developed. These results were converted into a dimensionless form as a function of a modified Stokes number. Based on results obtained in the laminar regime and for individual pebbles, the correlation developed for the inertial impaction component of deposition is believed to be credible. The form of the correlation developed also allows these results to be applied to pebble beds of different

  13. Benchmark Evaluation of HTR-PROTEUS Pebble Bed Experimental Program

    SciTech Connect

    Bess, John D.; Montierth, Leland; Köberl, Oliver; Snoj, Luka

    2014-10-09

    Benchmark models were developed to evaluate 11 critical core configurations of the HTR-PROTEUS pebble bed experimental program. Various additional reactor physics measurements were performed as part of this program; currently only a total of 37 absorber rod worth measurements have been evaluated as acceptable benchmark experiments for Cores 4, 9, and 10. Dominant uncertainties in the experimental keff for all core configurations come from uncertainties in the ²³⁵U enrichment of the fuel, impurities in the moderator pebbles, and the density and impurity content of the radial reflector. Calculations of keff with MCNP5 and ENDF/B-VII.0 neutron nuclear data are greater than the benchmark values but within 1% and also within the 3σ uncertainty, except for Core 4, which is the only randomly packed pebble configuration. Repeated calculations of keff with MCNP6.1 and ENDF/B-VII.1 are lower than the benchmark values and within 1% (~3σ) except for Cores 5 and 9, which calculate lower than the benchmark eigenvalues within 4σ. The primary difference between the two nuclear data libraries is the adjustment of the absorption cross section of graphite. Simulations of the absorber rod worth measurements are within 3σ of the benchmark experiment values. The complete benchmark evaluation details are available in the 2014 edition of the International Handbook of Evaluated Reactor Physics Benchmark Experiments.

  14. Benchmark Evaluation of HTR-PROTEUS Pebble Bed Experimental Program

    DOE PAGESBeta

    Bess, John D.; Montierth, Leland; Köberl, Oliver; Snoj, Luka

    2014-10-09

    Benchmark models were developed to evaluate 11 critical core configurations of the HTR-PROTEUS pebble bed experimental program. Various additional reactor physics measurements were performed as part of this program; currently only a total of 37 absorber rod worth measurements have been evaluated as acceptable benchmark experiments for Cores 4, 9, and 10. Dominant uncertainties in the experimental keff for all core configurations come from uncertainties in the ²³⁵U enrichment of the fuel, impurities in the moderator pebbles, and the density and impurity content of the radial reflector. Calculations of keff with MCNP5 and ENDF/B-VII.0 neutron nuclear data are greatermore » than the benchmark values but within 1% and also within the 3σ uncertainty, except for Core 4, which is the only randomly packed pebble configuration. Repeated calculations of keff with MCNP6.1 and ENDF/B-VII.1 are lower than the benchmark values and within 1% (~3σ) except for Cores 5 and 9, which calculate lower than the benchmark eigenvalues within 4σ. The primary difference between the two nuclear data libraries is the adjustment of the absorption cross section of graphite. Simulations of the absorber rod worth measurements are within 3σ of the benchmark experiment values. The complete benchmark evaluation details are available in the 2014 edition of the International Handbook of Evaluated Reactor Physics Benchmark Experiments.« less

  15. From CANDLE reactor to pebble-bed reactor

    SciTech Connect

    Chen, X. N.; Maschek, W.

    2006-07-01

    This paper attempts to reveal theoretically, by studying a diffusion-burn-up coupled neutronic model, that a so-called CANDLE reactor and a pebble-bed type reactor have a common burn-up feature. As already known, a solitary burn-up wave that can develop in the common U-Pu and Th-U conversion processes is the basic mechanism of the CANDLE reactor. In this paper it is demonstrated that a family of burn-up wave solution exists in the boundary value problem characterizing a pebble bed reactor, in which the fuel is loaded from above into the core and unloaded from bottom. Among this solution family there is a particular case, namely, a partial solitary wave solution, which begins from the fuel entrance side and extends into infinity on the exit side, and has a maximal bum-up rate in this family. An example dealing with the {sup 232}Th-{sup 233}U conversion chain is studied and the solutions are presented in order to show the mechanism of the burn-up wave. (authors)

  16. Deleterious Thermal Effects Due To Randomized Flow Paths in Pebble Bed, and Particle Bed Style Reactors

    NASA Technical Reports Server (NTRS)

    Moran, Robert P.

    2013-01-01

    A review of literature associated with Pebble Bed and Particle Bed reactor core research has revealed a systemic problem inherent to reactor core concepts which utilize randomized rather than structured coolant channel flow paths. For both the Pebble Bed and Particle Bed Reactor designs; case studies reveal that for indeterminate reasons, regions within the core would suffer from excessive heating leading to thermal runaway and localized fuel melting. A thermal Computational Fluid Dynamics model was utilized to verify that In both the Pebble Bed and Particle Bed Reactor concepts randomized coolant channel pathways combined with localized high temperature regions would work together to resist the flow of coolant diverting it away from where it is needed the most to cooler less resistive pathways where it is needed the least. In other words given the choice via randomized coolant pathways the reactor coolant will take the path of least resistance, and hot zones offer the highest resistance. Having identified the relationship between randomized coolant channel pathways and localized fuel melting it is now safe to assume that other reactor concepts that utilize randomized coolant pathways such as the foam core reactor are also susceptible to this phenomenon.

  17. Calculational approach and results of the safe shutdown earthquake event for the pebble bed modular reactor

    SciTech Connect

    Van Heerden, G.; Sen, S.; Reitsma, F.

    2006-07-01

    The Pebble Bed Modular Reactor (PBMR) concept can be described as a high-temperature helium-cooled, graphite-moderated pebble-bed reactor with a multi-pass fuelling scheme. The fuel is contained in 6 cm diameter graphite spheres containing carbon-based coated UO{sub 2} kernels. An online fuel reload scheme is applied with the fuel spheres being circulated through the reactor. The pebble-bed reactor core thus consists of fuel pebbles packed in the core cavity in a random way. The packing densities and pebble flow is well known through analysis and tests done in the German experimental and development program. The pebble-bed typically has a packing fraction of 0.61. In the event of an earthquake this packing fraction may increase with the effect that the core geometry and core reactivity will change. The Safe Shutdown Earthquake (SSE) analysis performed for the PBMR 400 MW design is described in this paper, and it specifically covers SSE-induced pebble-bed packing fractions of 0.62 and 0.64. The main effects governing the addition of reactivity in the SSE event are the changes in core neutronic leakage due to the decreased core size and the decreased effectiveness of the control rods as the pebble-bed height decreases. This paper describes the models, methods and tools used to analyse the event, the results obtained for the different approaches and the consequences and safety implications of such an event. (authors)

  18. Proliferation resistant fuel for pebble bed modular reactors

    SciTech Connect

    Ronen, Y.; Aboudy, M.; Regev, D.; Gilad, E.

    2012-07-01

    We show that it is possible to denature the Plutonium produced in Pebble Bed Modular Reactors (PBMR) by doping the nuclear fuel with either 3050 ppm of {sup 237}Np or 2100 ppm of Am vector. A correct choice of these isotopes concentration yields denatured Plutonium with isotopic ratio {sup 238}Pu/Pu {>=} 6%, for the entire fuel burnup cycle. The penalty for introducing these isotopes into the nuclear fuel is a subsequent shortening of the fuel burnup cycle, with respect to a non-doped reference fuel, by 41.2 Full Power Days (FPDs) and 19.9 FPDs, respectively, which correspond to 4070 MWd/ton and 1965 MWd/ton reduction in fuel discharge burnup. (authors)

  19. Tightly Coupled Multiphysics Algorithm for Pebble Bed Reactors

    SciTech Connect

    HyeongKae Park; Dana Knoll; Derek Gaston; Richard Martineau

    2010-10-01

    We have developed a tightly coupled multiphysics simulation tool for the pebble-bed reactor (PBR) concept, a type of Very High-Temperature gas-cooled Reactor (VHTR). The simulation tool, PRONGHORN, takes advantages of the Multiphysics Object-Oriented Simulation Environment library, and is capable of solving multidimensional thermal-fluid and neutronics problems implicitly with a Newton-based approach. Expensive Jacobian matrix formation is alleviated via the Jacobian-free Newton-Krylov method, and physics-based preconditioning is applied to minimize Krylov iterations. Motivation for the work is provided via analysis and numerical experiments on simpler multiphysics reactor models. We then provide detail of the physical models and numerical methods in PRONGHORN. Finally, PRONGHORN's algorithmic capability is demonstrated on a number of PBR test cases.

  20. EVALUATION OF THE INITIAL CRITICAL CONFIGURATION OF THE HTR-10 PEBBLE-BED REACTOR

    SciTech Connect

    William K. Terry

    2005-11-01

    This report describes the evaluation of data from the initial criticality measurement of the HTR-10 pebble-bed reactor at the Institute of Nuclear Energy Technology in China to determine whether the data are of sufficient quality to use as benchmarks for reactor physics computer codes intended for pebble-bed reactor analysis. The evaluation applied the INL pebble-bed reactor physics code PEBBED to perform an uncertainty analysis on the core critical height. The overall uncertainty in k-effective was slightly over 0.5%, which is considered adequate for an experimental benchmark.

  1. Effective Thermal Property Estimation of Unitary Pebble Beds Based on a CFD-DEM Coupled Method for a Fusion Blanket

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Chen, Youhua; Huang, Kai; Liu, Songlin

    2015-12-01

    Lithium ceramic pebble beds have been considered in the solid blanket design for fusion reactors. To characterize the fusion solid blanket thermal performance, studies of the effective thermal properties, i.e. the effective thermal conductivity and heat transfer coefficient, of the pebble beds are necessary. In this paper, a 3D computational fluid dynamics discrete element method (CFD-DEM) coupled numerical model was proposed to simulate heat transfer and thereby estimate the effective thermal properties. The DEM was applied to produce a geometric topology of a prototypical blanket pebble bed by directly simulating the contact state of each individual particle using basic interaction laws. Based on this geometric topology, a CFD model was built to analyze the temperature distribution and obtain the effective thermal properties. The current numerical model was shown to be in good agreement with the existing experimental data for effective thermal conductivity available in the literature. supported by National Special Project for Magnetic Confined Nuclear Fusion Energy of China (Nos. 2013GB108004, 2015GB108002, 2014GB122000 and 2014GB119000), and National Natural Science Foundation of China (No. 11175207)

  2. Nonproliferation issue of the pebble bed high-temperature reactor

    SciTech Connect

    Teuchert, E.; Haas, K.A.

    1986-02-01

    The constraints of nonproliferation of weapons-grade fuel are most favorably observed in the medium enriched uranium (MEU) fuel cycle of the pebble bed high-temperature reactor, using 20% enriched uranium as feed and thorium as breed material. The cycle can be designed so that the uranium enrichment never exceeds the limitation defined for nonsensitive fuel. In the spent fuel, the amount of fissile plutonium is one order of magnitude lower than for the light water reactor and it is strongly denatured by the even-numbered plutonium isotopes. In the once-through option applied in the introductory phase of the reactor, the proliferation restraints of the plutonium are furnished by the choice of the carbon/heavy metal ratio higher than 450 and of the burnup of 100 MWd/kg heavy metal. The Pu/sub FISS/Pu/sub TOTAL/ is achieved as low as 37%, and the admixing of 8% of /sup 238/Pu would complicate its handling by the decay heat rating. In the closed MEU cycle, the /sup 238/U is continuously separated from the cycle by the use of two different types of fuel elements: Thorium and 20% enriched uranium are inserted into the feed elements, and the uranium recovered from the reprocessing is loaded into the burnup elements, without thorium. These elements are removed from the cycle without reprocessing. Again the proliferation risk of the fissile plutonium is minimized because of its very low quantity and high denaturization.

  3. Pebble Bed Reactors Design Optimization Methods and their Application to the Pebble Bed Fluoride Salt Cooled High Temperature Reactor (PB-FHR)

    NASA Astrophysics Data System (ADS)

    Cisneros, Anselmo Tomas, Jr.

    The Fluoride salt cooled High temperature Reactor (FHR) is a class of advanced nuclear reactors that combine the robust coated particle fuel form from high temperature gas cooled reactors, direct reactor auxillary cooling system (DRACS) passive decay removal of liquid metal fast reactors, and the transparent, high volumetric heat capacitance liquid fluoride salt working fluids---flibe (33%7Li2F-67%BeF)---from molten salt reactors. This combination of fuel and coolant enables FHRs to operate in a high-temperature low-pressure design space that has beneficial safety and economic implications. In 2012, UC Berkeley was charged with developing a pre-conceptual design of a commercial prototype FHR---the Pebble Bed- Fluoride Salt Cooled High Temperature Reactor (PB-FHR)---as part of the Nuclear Energy University Programs' (NEUP) integrated research project. The Mark 1 design of the PB-FHR (Mk1 PB-FHR) is 236 MWt flibe cooled pebble bed nuclear heat source that drives an open-air Brayton combine-cycle power conversion system. The PB-FHR's pebble bed consists of a 19.8% enriched uranium fuel core surrounded by an inert graphite pebble reflector that shields the outer solid graphite reflector, core barrel and reactor vessel. The fuel reaches an average burnup of 178000 MWt-d/MT. The Mk1 PB-FHR exhibits strong negative temperature reactivity feedback from the fuel, graphite moderator and the flibe coolant but a small positive temperature reactivity feedback of the inner reflector and from the outer graphite pebble reflector. A novel neutronics and depletion methodology---the multiple burnup state methodology was developed for an accurate and efficient search for the equilibrium composition of an arbitrary continuously refueled pebble bed reactor core. The Burnup Equilibrium Analysis Utility (BEAU) computer program was developed to implement this methodology. BEAU was successfully benchmarked against published results generated with existing equilibrium depletion codes VSOP

  4. Discrete Element Simulations of Granular Flow in a Pebble Bed Nuclear Reactor

    NASA Astrophysics Data System (ADS)

    Grest, Gary S.; Rycroft, Chris H.; Landry, James W.

    2005-03-01

    Pebble-bed reactor technology, which is currently being revived around the world, raises fundamental questions about granular flow in silos. The reactor core is composed of spherical billiard-ball sized (6cm diameter) graphite fuel pebbles containing sand-sized uranium fuel particles. The fuel pebbles drain very slowly through the core as a continuous refueling process. In some designs, a dynamical central column is formed from graphite moderator pebbles, physically identical to the fuel pebbles without any fuel. The total number of pebbles is of order 440,000 in a cell approximately 3.5m in diameter and 8.5m tall. Using discrete element (molecular dynamics) simulations we have studied a full scale model of the system. We find that the interface between the fuel and moderator particles remains sharp, as there is very little horizontal motion of the pebbles as they flow through the reactor. We measure mean velocity profiles and compare to various continuum models. We also investigated the feasibility of a bi-disperse core, containing smaller moderator pebbles, with the same size fuel pebbles, which could improve performance by focusing helium gas flow on the hotter fuel region. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04- 94AL85000.

  5. Experimental investigation of the pebble bed structure by using gamma ray tomography

    NASA Astrophysics Data System (ADS)

    Ahmed, Fadha Shakir

    Pebble Bed Reactors offer a future for new nuclear energy plants. They are small, inherently safe, and can be competitive with fossil fuels. The fuel forms a randomly stacked pebble with non-uniform fuel densities. The thermal-mechanical behavior of pebble bed reactor core is depends strongly on the spatial variation of packing fraction in the bed and in particular on the number of contacts between pebbles, and between the pebbles and the blanket walls. To investigate these effects, experimental data to characterize bed structure are needed along with other numerical simulation and computational tools for validation. In this study, a powerful technique of high-energy gamma-ray computed tomography (CT scanner system) is employed for the first time for the quantification of the structure of pebble bed in term of the cross-sectional time-averaged void and distributions, it radial profiles and the statistical analysis. The alternative minimization (AM) iteration algorithm is used for image reconstruction. The spatial resolution of the CT scan is about 2 mm with 100 x 100 pixel used to reconstruct the cross-sectional image. Results of tomography with this advanced technique on three different pebble sizes at different axial levels are presented. The bed consisted of a glass spheres (Marbles) with a diameter d1= 1.27 cm, d2= 2.54 cm and d3= 5 cm in a Plexiglas cylinder with diameter D = 30.48 cm (D/d1 = 24, D/d2 = 12 and D/d3 = 6), and had an average void fraction epsilon1= 0.389, epsilon2 = 0.40 and epsilon 3 =0.43, respectively. The radial void fraction profile showed large oscillations with the bigger pebble diameters and the void fraction is higher on the wall with a minimum void fraction of 0.33 at 0.68 pebble diameter away from the wall. It was found that the void distribution in random packed bed depends strongly on the pebble diameter with respect to the bed diameter (D/d p) and the packing mode. The oscillation is quiet large with the smaller aspect ratio (D

  6. METHODS FOR MODELING THE PACKING OF FUEL ELEMENTS IN PEBBLE BED REACTORS

    SciTech Connect

    Abderrafi M. Ougouag; Joshua J. Cogliati; Jan-Leen Kloosterman

    2005-09-01

    Two methods for the modeling of the packing of pebbles in the pebble bed reactors are presented and compared. The first method is based on random generation of potential centers for the pebbles, followed by rejection of points that are not compatible with the geometric constraint of no (or limited) pebbles overlap. The second method models the actual physical packing process, accounting for the dynamic of pebbles as they are dropped onto the pebble bed and as they settle therein. A simplification in the latter model is the assumption of a starting point with very dilute packing followed by settling. The results from the two models are compared and the properties of the second model and the dependence of its results on many of the modeling parameters are presented. The first model (with no overlap allowed) has been implemented into a code to compute Dancoff factors. The second model will soon be implemented into that same code and will also be used to model flow of pebbles in a reactor and core densification in the simulation of earthquakes. Both methods reproduce experimental values well, with the latter displaying a high level of fidelity.

  7. INVESTIGATION OF BOUNDS ON PARTICLE PACKING IN PEBBLE-BED HIGH TEMPERATURE REACTORS

    SciTech Connect

    Nuclear Engineering and Design; Jan Leen Kloosterman; Wilfred F.G. van Rooijen; Hans D. Gougar; William K. Terry

    2006-03-01

    Models and methods are presented for determining practical limits of the packing density of TRISO particles in fuel pebbles for a pebble-bed reactor (PBR). These models are devised for designing and interpreting fuel testing experiments. Two processes for particle failure are accounted for: failure of touching particles at the pressing stage in the pebble manufacturing process, and failure due to inner pressure buildup during irradiation. The second process gains importance with increasing fuel temperature, which limits the particle packing density and the corresponding fuel enrichment. Suggestions for improvements to the models are presented.

  8. A COMPARISON OF PEBBLE MIXING AND DEPLETION ALGORITHMS USED IN PEBBLE-BED REACTOR EQUILIBRIUM CYCLE SIMULATION

    SciTech Connect

    Hans D. Gougar; Frederik Reitsma; Wessel Joubert

    2009-05-01

    Recirculating pebble-bed reactors are distinguished from all other reactor types by the downward movement through and reinsertion of fuel into the core during operation. Core simulators must account for this movement and mixing in order to capture the physics of the equilibrium cycle core. VSOP and PEBBED are two codes used to perform such simulations, but they do so using different methods. In this study, a simplified pebble-bed core with a specified flux profile and cross sections is used as the model for conducting analyses of two types of burnup schemes. The differences between the codes are described and related to the differences observed in the nuclide densities in pebbles discharged from the core. Differences in the methods for computing fission product buildup and average number densities lead to significant differences in the computed core power and eigenvalue. These test models provide a key component of an overall equilibrium cycle benchmark involving neutron transport, cross section generation, and fuel circulation.

  9. Modular Pebble Bed Reactor Project, University Research Consortium Annual Report

    SciTech Connect

    Petti, David Andrew

    2000-07-01

    This project is developing a fundamental conceptual design for a gas-cooled, modular, pebble bed reactor. Key technology areas associated with this design are being investigated which intend to address issues concerning fuel performance, safety, core neutronics and proliferation resistance, economics and waste disposal. Research has been initiated in the following areas: · Improved fuel particle performance · Reactor physics · Economics · Proliferation resistance · Power conversion system modeling · Safety analysis · Regulatory and licensing strategy Recent accomplishments include: · Developed four conceptual models for fuel particle failures that are currently being evaluated by a series of ABAQUS analyses. Analytical fits to the results are being performed over a range of important parameters using statistical/factorial tools. The fits will be used in a Monte Carlo fuel performance code, which is under development. · A fracture mechanics approach has been used to develop a failure probability model for the fuel particle, which has resulted in significant improvement over earlier models. · Investigation of fuel particle physio-chemical behavior has been initiated which includes the development of a fission gas release model, particle temperature distributions, internal particle pressure, migration of fission products, and chemical attack of fuel particle layers. · A balance of plant, steady-state thermal hydraulics model has been developed to represent all major components of a MPBR. Component models are being refined to accurately reflect transient performance. · A comparison between air and helium for use in the energy-conversion cycle of the MPBR has been completed and formed the basis of a master’s degree thesis. · Safety issues associated with air ingress are being evaluated. · Post shutdown, reactor heat removal characteristics are being evaluated by the Heating-7 code. · PEBBED, a fast deterministic neutronic code package suitable for

  10. Computational and experimental prediction of dust production in pebble bed reactors, Part II

    SciTech Connect

    Mie Hiruta; Gannon Johnson; Maziar Rostamian; Gabriel P. Potirniche; Abderrafi M. Ougouag; Massimo Bertino; Louis Franzel; Akira Tokuhiro

    2013-10-01

    This paper is the continuation of Part I, which describes the high temperature and high pressure helium environment wear tests of graphite–graphite in frictional contact. In the present work, it has been attempted to simulate a Pebble Bed Reactor core environment as compared to Part I. The experimental apparatus, which is a custom-designed tribometer, is capable of performing wear tests at PBR relevant higher temperatures and pressures under a helium environment. This environment facilitates prediction of wear mass loss of graphite as dust particulates from the pebble bed. The experimental results of high temperature helium environment are used to anticipate the amount of wear mass produced in a pebble bed nuclear reactor.

  11. Waste characteristics of spent nuclear fuel from a pebble bed reactor

    SciTech Connect

    Owen, P.E.

    1999-06-01

    A preliminary comparative assessment is made of the spent fuel characteristics and disposal aspects between a high temperature, gas cooled, reactor with a pebble bed core (PBR) and a pressurized water reactor (PWR). There are three significant differences which impact the disposal characteristics of PBR spent pebble fuel from PWR spent fuel assemblies. Pebble bed fuel has burnup as high as 100,000 MWD(t)/MTHM and thus, there is significantly less activity and decay heat in the fuel when it is disposed. The large amount of graphite in the waste form leads to a low power density and more waste per unit volume than a typical PWR. Pebble Fuel contains a protective layer of Silicon Carbide. The theoretical spacing of waste packages of spent pebble fuel given its unique characteristics as applied to the conditions of Yucca Mountain is of major concern when determining the cost of disposing of the larger volumes of spent pebble fuel. Graphite is a unique waste form and atypical of waste designated for Yucca Mountain. The interactions of silicon carbide with uranium oxide fuel and its implications to long term storage at the repository are examined. There are three primary conclusions to this thesis. First, the area required to store pebble fuel is less than the area required to store light water reactor spent fuel. Second, graphite has excellent characteristics as a waste form. The waste form of the spent pebble fuel is more robust and will perform better than light water reactor fuel at the United States repository at Yucca Mountain. Third, a secondary phase forms between the layers of silicon carbide and the uranium oxide fuel. The secondary phase retards the release of radionuclides to the environment.

  12. The importance of the AVR pebble-bed reactor for the future of nuclear power

    SciTech Connect

    Pohl, P.

    2006-07-01

    The AVR pebble-bed high temperature gas-cooled reactor (HTGR) at Juelich (Germany)) operated from 1967 to 1988 and was certainly the most important HTGR project of the past. The reactor was the mass test bed for all development steps of HTGR pebble fuel. Some early fuel charges failed under high temperature conditions and contaminated the reactor. An accurate pebble measurement (Cs 137) allowed to clean the core from unwanted pebbles after 1981. The coolant activity went down and remained very low for the remaining reactor operation. A melt-wire experiment in 1986 revealed max. coolant temperatures of >1280 deg. C and fuel temperatures of >1350 deg. C, explained by under-estimated bypasses. The fuel still in the core achieved high burn-ups and showed under the extreme temperature conditions excellent fission product retention. Thus, the AVR operation qualified the HTGR fuel, and an average discharge burn-up of 112% fifa revealed an excellent fuel economy of the pebble-bed reactor. Furthermore, the AVR operation offers many meaningful data for code-to-experiment comparisons. (authors)

  13. Pebble Bed Reactors Design Optimization Methods and their Application to the Pebble Bed Fluoride Salt Cooled High Temperature Reactor (PB-FHR)

    NASA Astrophysics Data System (ADS)

    Cisneros, Anselmo Tomas, Jr.

    The Fluoride salt cooled High temperature Reactor (FHR) is a class of advanced nuclear reactors that combine the robust coated particle fuel form from high temperature gas cooled reactors, direct reactor auxillary cooling system (DRACS) passive decay removal of liquid metal fast reactors, and the transparent, high volumetric heat capacitance liquid fluoride salt working fluids---flibe (33%7Li2F-67%BeF)---from molten salt reactors. This combination of fuel and coolant enables FHRs to operate in a high-temperature low-pressure design space that has beneficial safety and economic implications. In 2012, UC Berkeley was charged with developing a pre-conceptual design of a commercial prototype FHR---the Pebble Bed- Fluoride Salt Cooled High Temperature Reactor (PB-FHR)---as part of the Nuclear Energy University Programs' (NEUP) integrated research project. The Mark 1 design of the PB-FHR (Mk1 PB-FHR) is 236 MWt flibe cooled pebble bed nuclear heat source that drives an open-air Brayton combine-cycle power conversion system. The PB-FHR's pebble bed consists of a 19.8% enriched uranium fuel core surrounded by an inert graphite pebble reflector that shields the outer solid graphite reflector, core barrel and reactor vessel. The fuel reaches an average burnup of 178000 MWt-d/MT. The Mk1 PB-FHR exhibits strong negative temperature reactivity feedback from the fuel, graphite moderator and the flibe coolant but a small positive temperature reactivity feedback of the inner reflector and from the outer graphite pebble reflector. A novel neutronics and depletion methodology---the multiple burnup state methodology was developed for an accurate and efficient search for the equilibrium composition of an arbitrary continuously refueled pebble bed reactor core. The Burnup Equilibrium Analysis Utility (BEAU) computer program was developed to implement this methodology. BEAU was successfully benchmarked against published results generated with existing equilibrium depletion codes VSOP

  14. CORE ANALYSIS, DESIGN AND OPTIMIZATION OF A DEEP-BURN PEBBLE BED REACTOR

    SciTech Connect

    B. Boer; A. M. Ougouag

    2010-05-01

    Achieving a high burnup in the Deep-Burn pebble bed reactor design, while remaining within the limits for fuel temperature, power peaking and temperature reactivity feedback, is challenging. The high content of Pu and Minor Actinides in the Deep-Burn fuel significantly impacts the thermal neutron energy spectrum. This can result in power and temperature peaking in the pebble bed core in locally thermalized regions near the graphite reflectors. Furthermore, the interplay of the Pu resonances of the neutron absorption cross sections at low-lying energies can lead to a positive temperature reactivity coefficient for the graphite moderator at certain operating conditions. To investigate the aforementioned effects a code system using existing codes has been developed for neutronic, thermal-hydraulic and fuel depletion analysis of Deep-Burn pebble bed reactors. A core analysis of a Deep-Burn Pebble Bed Modular Reactor (400 MWth) design has been performed for two Deep-Burn fuel types and possible improvements of the design with regard to power peaking and temperature reactivity feedback are identified.

  15. Stress Analysis of Coated Particle Fuel in the Deep-Burn Pebble Bed Reactor Design

    SciTech Connect

    B. Boer; A. M. Ougouag

    2010-05-01

    High fuel temperatures and resulting fuel particle coating stresses can be expected in a Pu and minor actinide fueled Pebble Bed Modular Reactor (400 MWth) design as compared to the ’standard’ UO2 fueled core. The high discharge burnup aimed for in this Deep-Burn design results in increased power and temperature peaking in the pebble bed near the inner and outer reflector. Furthermore, the pebble power in a multi-pass in-core pebble recycling scheme is relatively high for pebbles that make their first core pass. This might result in an increase of the mechanical failure of the coatings, which serve as the containment of radioactive fission products in the PBMR design. To investigate the integrity of the particle fuel coatings as a function of the irradiation time (i.e. burnup), core position and during a Loss Of Forced Cooling (LOFC) incident the PArticle STress Analysis code (PASTA) has been coupled to the PEBBED code for neutronics, thermal-hydraulics and depletion analysis of the core. Two deep burn fuel types (Pu with or without initial MA fuel content) have been investigated with the new code system for normal and transient conditions including the effect of the statistical variation of thickness of the coating layers.

  16. High efficiency power generation from coal and wastes utilizing high temperature air combustion technology (Part 1: Performance of pebble bed gasifier for coal and wastes)

    SciTech Connect

    Kosaka, Hitoshi; Iwahashi, Takashi; Yoshida, Nobuhiro; Tsuji, Kiyoshi; Yoshikawa, Kunio; Kiga, Takashi; Tamamushi, Fumihiro; Makino, Kenji; Oonish, Hiroshi

    1998-07-01

    A new concept of a gasifier for coal and wastes is proposed where entrained bed and fixed pebble bed are combined. Main features of this pebble bed gasifier are high efficiency molten slag capture, high efficiency gasification and compactness. Coal and RFD combustion experiments using the pebble bed gasifier demonstrated high efficiency capture and continuous extraction of molten slag as well as complete char combustion with extra ordinarily short residence time of pulverized coal and crushed RDF at the temperature level of about 1,500 C within the pebble bed. Durability tests using high temperature electric furnace has shown that high density alumna is a good candidate for pebble material.

  17. In-pile test of Li 2TiO 3 pebble bed with neutron pulse operation

    NASA Astrophysics Data System (ADS)

    Tsuchiya, K.; Nakamichi, M.; Kikukawa, A.; Nagao, Y.; Enoeda, M.; Osaki, T.; Ioki, K.; Kawamura, H.

    2002-12-01

    Lithium titanate (Li 2TiO 3) is one of the candidate materials as tritium breeder in the breeding blanket of fusion reactors, and it is necessary to show the tritium release behavior of Li 2TiO 3 pebble beds. Therefore, a blanket in-pile mockup was developed and in situ tritium release experiments with the Li 2TiO 3 pebble bed were carried out in the Japan Materials Testing Reactor. In this study, the relationship between tritium release behavior from Li 2TiO 3 pebble beds and effects of various parameters were evaluated. The ( R/ G) ratio of tritium release ( R) and tritium generation ( G) was saturated when the temperature at the outside edge of the Li 2TiO 3 pebble bed became 300 °C. The tritium release amount increased cycle by cycle and saturated after about 20 pulse operations.

  18. Fabrication and characterization of LiH ceramic pebbles by wet process

    NASA Astrophysics Data System (ADS)

    Xiang, Maoqiao; Zhang, Yingchun; Hong, Ming; Liu, Zhiang; Leng, Jiaxun; Zhang, Yun; Zhang, Jialiang; Wang, Wenchang

    2014-09-01

    Lithium hydride (LiH) ceramic pebbles, a new potential tritium breeding material in fusion-fission or fusion reactor blanket, were prepared by wet process for the first time. XRD results showed that LiOH, LiOH·H2O, Li2CO3 and Li2O were found in the surface of LiH pebbles. However, the pure phase of LiH pebbles without cracks could be obtained by paraffin wax coating technique. The average value (a.v.) of the sphericity and the diameter were 1.01 and 0.98 mm, respectively. The LiH pebbles sintered at 450 °C for 3 h under 80 ml/min flowing argon, reached ∼92.3% of the theoretical density, with the grain size of 5.59 μm (a.v.). And the crush load was measured to be 15 N on average. The described wet process exhibited multiple advantages for fabricating LiH pebbles.

  19. Conceptual Design of a Very High Temperature Pebble-Bed Reactor

    SciTech Connect

    Hans D. Gougar; A. M. Ougouag; Richard M. Moore; W. K. Terry

    2003-11-01

    Efficient electricity and hydrogen production distinguish the Very High Temperature Reactor as the leading Generation IV advanced concept. This graphite-moderated, helium-cooled reactor achieves a requisite high outlet temperature while retaining the passive safety and proliferation resistance required of Generation IV designs. Furthermore, a recirculating pebble-bed VHTR can operate with minimal excess reactivity to yield improved fuel economy and superior resistance to ingress events. Using the PEBBED code developed at the INEEL, conceptual designs of 300 megawatt and 600 megawatt (thermal) Very High Temperature Pebble-Bed Reactors have been developed. The fuel requirements of these compare favorably to the South African PBMR. Passive safety is confirmed with the MELCOR accident analysis code.

  20. Development of materials and fabrication of porous and pebble bed beryllium multipliers

    NASA Astrophysics Data System (ADS)

    Davydov, D. A.; Solonin, M. I.; Markushkin, Yu. E.; Gorokhov, V. A.; Gorlevsky, V. V.; Nikolaev, G. N.

    2000-12-01

    Beryllium is considered to be a neutron multiplier material for the reference ITER breeding blanket. The main requirements for the porous beryllium multiplier for the breeding blanket are: (1) inherently open porosity within 20 ± 2% for easy removal of radioactive gases; (2) high thermal conductivity; (3) close contact with a stainless steel (SS) shell to provide high heat transfer. A beryllium multiplier can be fabricated by two different techniques: by manufacturing porous or pebble bed beryllium. The method designed (patent 2106931 RU) in SSC RF-VNIINM (Russia) provides for the production of porous beryllium conforming to the requirements mentioned above. For comparative fission tests and the optimization of breeding zone functional capabilities, porous (21.9%) and binary pebble bed (density=78%) beryllium multipliers were fabricated. DEMO breeding blanket models and a mock-up of fission (IVV-2M reactor) tests have been manufactured at SSC RF-VNIINM.

  1. Modular Pebble-Bed Reactor Project: Laboratory-Directed Research and Development Program FY 2002 Annual Report

    SciTech Connect

    Petti, David Andrew; Dolan, Thomas James; Miller, Gregory Kent; Moore, Richard Leroy; Terry, William Knox; Ougouag, Abderrafi Mohammed-El-Ami; Oh, Chang H; Gougar, Hans D

    2002-11-01

    This report documents the results of our research in FY-02 on pebble-bed reactor technology under our Laboratory Directed Research and Development (LDRD) project entitled the Modular Pebble-Bed Reactor. The MPBR is an advanced reactor concept that can meet the energy and environmental needs of future generations under DOE’s Generation IV initiative. Our work is focused in three areas: neutronics, core design and fuel cycle; reactor safety and thermal hydraulics; and fuel performance.

  2. Advanced Core Design And Fuel Management For Pebble-Bed Reactors

    SciTech Connect

    Hans D. Gougar; Abderrafi M. Ougouag; William K. Terry

    2004-10-01

    A method for designing and optimizing recirculating pebble-bed reactor cores is presented. At the heart of the method is a new reactor physics computer code, PEBBED, which accurately and efficiently computes the neutronic and material properties of the asymptotic (equilibrium) fuel cycle. This core state is shown to be unique for a given core geometry, power level, discharge burnup, and fuel circulation policy. Fuel circulation in the pebble-bed can be described in terms of a few well?defined parameters and expressed as a recirculation matrix. The implementation of a few heat?transfer relations suitable for high-temperature gas-cooled reactors allows for the rapid estimation of thermal properties critical for safe operation. Thus, modeling and design optimization of a given pebble-bed core can be performed quickly and efficiently via the manipulation of a limited number key parameters. Automation of the optimization process is achieved by manipulation of these parameters using a genetic algorithm. The end result is an economical, passively safe, proliferation-resistant nuclear power plant.

  3. Advanced core design and fuel management for pebble-bed reactors

    NASA Astrophysics Data System (ADS)

    Gougar, Hans David

    A method for designing and optimizing recirculating pebble-bed reactor cores is presented. At the heart of the method is a new reactor physics computer code, PEBBED, which accurately and efficiently computes the neutronic and material properties of the asymptotic (equilibrium) fuel cycle. This core state is shown to be unique for a given core geometry, power level, discharge burnup, and fuel circulation policy. Fuel circulation in the pebble-bed can be described in terms of a few well-defined parameters and expressed as a recirculation matrix. The implementation of a few heat-transfer relations suitable for high-temperature gas-cooled reactors allows for the rapid estimation of thermal properties critical for safe operation. Thus, modeling and design optimization of a given pebble-bed core can be performed quickly and efficiently via the manipulation of a limited number key parameters. Automation of the optimization process is achieved by manipulation of these parameters using a genetic algorithm. The end result is an economical, passively safe, proliferation-resistant nuclear power plant.

  4. Fabrication and characterization of Li 3TaO 4 ceramic pebbles by wet process

    NASA Astrophysics Data System (ADS)

    Zhu, Deqiong; Peng, Shuming; Chen, Xiaojun; Gao, Xiaoling; Yang, Tongzai

    2010-01-01

    Lithium-containing ceramics have long been recognized as the tritium breeding materials in the fusion-fission or fusion reactor blanket. Li3TaO4 (lithium orthotantalate) pebbles, with high melting point (∼1406 °C), good thermal stability, and high thermal conductivity, were fabricated by wet process (freeze-drying) as a new potential candidate of tritium breeder. The diameter of ceramic pebbles is 0.7-1.0 mm, density is over 90% (TD), pore diameter is 1.86 μm (a.v), grain size is 15 μm (a.v), crush load is up to 46.7 N (a.v).

  5. HTR-PROTEUS Pebble Bed Experimental Program Cores 1, 1A, 2, and 3: Hexagonal Close Packing with a 1:2 Moderator-to-Fuel Pebble Ratio

    SciTech Connect

    John D. Bess; Barbara H. Dolphin; James W. Sterbentz; Luka Snoj; Igor Lengar; Oliver Köberl

    2012-03-01

    In its deployment as a pebble bed reactor (PBR) critical facility from 1992 to 1996, the PROTEUS facility was designated as HTR-PROTEUS. This experimental program was performed as part of an International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP) on the Validation of Safety Related Physics Calculations for Low Enriched HTGRs. Within this project, critical experiments were conducted for graphite moderated LEU systems to determine core reactivity, flux and power profiles, reaction-rate ratios, the worth of control rods, both in-core and reflector based, the worth of burnable poisons, kinetic parameters, and the effects of moisture ingress on these parameters. Four benchmark experiments were evaluated in this report: Cores 1, 1A, 2, and 3. These core configurations represent the hexagonal close packing (HCP) configurations of the HTR-PROTEUS experiment with a moderator-to-fuel pebble ratio of 1:2. Core 1 represents the only configuration utilizing ZEBRA control rods. Cores 1A, 2, and 3 use withdrawable, hollow, stainless steel control rods. Cores 1 and 1A are similar except for the use of different control rods; Core 1A also has one less layer of pebbles (21 layers instead of 22). Core 2 retains the first 16 layers of pebbles from Cores 1 and 1A and has 16 layers of moderator pebbles stacked above the fueled layers. Core 3 retains the first 17 layers of pebbles but has polyethylene rods inserted between pebbles to simulate water ingress. The additional partial pebble layer (layer 18) for Core 3 was not included as it was used for core operations and not the reported critical configuration. Cores 1, 1A, 2, and 3 were determined to be acceptable benchmark experiments.

  6. HTR-PROTEUS Pebble Bed Experimental Program Cores 1, 1A, 2, and 3: Hexagonal Close Packing with a 1:2 Moderator-to-Fuel Pebble Ratio

    SciTech Connect

    John D. Bess; Barbara H. Dolphin; James W. Sterbentz; Luka Snoj; Igor Lengar; Oliver Köberl

    2013-03-01

    In its deployment as a pebble bed reactor (PBR) critical facility from 1992 to 1996, the PROTEUS facility was designated as HTR-PROTEUS. This experimental program was performed as part of an International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP) on the Validation of Safety Related Physics Calculations for Low Enriched HTGRs. Within this project, critical experiments were conducted for graphite moderated LEU systems to determine core reactivity, flux and power profiles, reaction-rate ratios, the worth of control rods, both in-core and reflector based, the worth of burnable poisons, kinetic parameters, and the effects of moisture ingress on these parameters. Four benchmark experiments were evaluated in this report: Cores 1, 1A, 2, and 3. These core configurations represent the hexagonal close packing (HCP) configurations of the HTR-PROTEUS experiment with a moderator-to-fuel pebble ratio of 1:2. Core 1 represents the only configuration utilizing ZEBRA control rods. Cores 1A, 2, and 3 use withdrawable, hollow, stainless steel control rods. Cores 1 and 1A are similar except for the use of different control rods; Core 1A also has one less layer of pebbles (21 layers instead of 22). Core 2 retains the first 16 layers of pebbles from Cores 1 and 1A and has 16 layers of moderator pebbles stacked above the fueled layers. Core 3 retains the first 17 layers of pebbles but has polyethylene rods inserted between pebbles to simulate water ingress. The additional partial pebble layer (layer 18) for Core 3 was not included as it was used for core operations and not the reported critical configuration. Cores 1, 1A, 2, and 3 were determined to be acceptable benchmark experiments.

  7. Analysis of granular flow in a pebble-bed nuclear reactor

    NASA Astrophysics Data System (ADS)

    Rycroft, Chris H.; Grest, Gary S.; Landry, James W.; Bazant, Martin Z.

    2006-08-01

    Pebble-bed nuclear reactor technology, which is currently being revived around the world, raises fundamental questions about dense granular flow in silos. A typical reactor core is composed of graphite fuel pebbles, which drain very slowly in a continuous refueling process. Pebble flow is poorly understood and not easily accessible to experiments, and yet it has a major impact on reactor physics. To address this problem, we perform full-scale, discrete-element simulations in realistic geometries, with up to 440000 frictional, viscoelastic 6-cm-diam spheres draining in a cylindrical vessel of diameter 3.5m and height 10m with bottom funnels angled at 30° or 60°. We also simulate a bidisperse core with a dynamic central column of smaller graphite moderator pebbles and show that little mixing occurs down to a 1:2 diameter ratio. We analyze the mean velocity, diffusion and mixing, local ordering and porosity (from Voronoi volumes), the residence-time distribution, and the effects of wall friction and discuss implications for reactor design and the basic physics of granular flow.

  8. A simplified DEM-CFD approach for pebble bed reactor simulations

    SciTech Connect

    Li, Y.; Ji, W.

    2012-07-01

    In pebble bed reactors (PBR's), the pebble flow and the coolant flow are coupled with each other through coolant-pebble interactions. Approaches with different fidelities have been proposed to simulate similar phenomena. Coupled Discrete Element Method-Computational Fluid Dynamics (DEM-CFD) approaches are widely studied and applied in these problems due to its good balance between efficiency and accuracy. In this work, based on the symmetry of the PBR geometry, a simplified 3D-DEM/2D-CFD approach is proposed to speed up the DEM-CFD simulation without significant loss of accuracy. Pebble flow is simulated by a full 3-D DEM, while the coolant flow field is calculated with a 2-D CFD simulation by averaging variables along the annular direction in the cylindrical geometry. Results show that this simplification can greatly enhance the efficiency for cylindrical core, which enables further inclusion of other physics such as thermal and neutronic effect in the multi-physics simulations for PBR's. (authors)

  9. Analysis of granular flow in a pebble-bed nuclear reactor

    SciTech Connect

    Rycroft, C H; Grest, Gary S; Landry, James W; Bazant, Martin Z

    2006-04-17

    Pebble-bed nuclear reactor technology, which is currently being revived around the world, raises fundamental questions about dense granular flow in silos. A typical reactor core is composed of graphite fuel pebbles, which drain very slowly in a continuous refueling process. Pebble flow is poorly understood and not easily accessible to experiments, and yet it has a ma jor impact on reactor physics. To address this problem, we perform full-scale, discrete-element simulations in realistic geometries, with up to 440,000 frictional, viscoelastic 6cm-diameter spheres draining in a cylindrical vessel of diameter 3.5m and height 10m with bottom funnels angled at 30° or 60° . We also simulate a bidisperse core with a dynamic central column of smaller graphite moderator pebbles and show that little mixing occurs down to a 1:2 diameter ratio. We analyze the mean velocity, diffusion and mixing, local ordering and porosity (from Voronoi volumes), the residence-time distribution, and the effects of wall friction and discuss implications for reactor design and the basic physics of granular flow.

  10. Computational and experimental prediction of dust production in pebble bed reactors -- Part I

    SciTech Connect

    Maziar Rostamian; Gannon Johnson; Mie Hiruta; Gabriel P. Potirniche; Abderrafi M. Ougouag; Joshua J. Cogliati; Akira Tokuhiro

    2013-10-01

    This paper describes the computational modeling and simulation, and experimental testing of graphite moderators in frictional contacts as anticipated in a pebble bed reactor. The potential of carbonaceous particulate generation due to frictional contact at the surface of pebbles and the ensuing entrainment and transport into the gas coolant are safety concerns at elevated temperatures under accident scenarios such as air ingress in the high temperature gas-cooled reactor. The safety concerns are due to the documented ability of carbonaceous particulates to adsorb fission products and transport them in the primary circuit of the pebble bed reactor, thus potentially giving rise to a relevant source term under accident scenarios. Here, a finite element approach is implemented to develop a nonlinear wear model in air environment. In this model, material wear coefficient is related to the changes in asperity height during wear. The present work reports a comparison between the finite element simulations and the experimental results obtained using a custom-designed tribometer. The experimental and computational results are used to estimate the quantity of nuclear grade graphite dust produced from a typical anticipated configuration. In Part II, results from a helium environment at higher temperatures and pressures are experimentally studied.

  11. Investigation on using neutron counting techniques for online burnup monitoring of pebble bed reactor fuels

    NASA Astrophysics Data System (ADS)

    Zhao, Zhongxiang

    Modular Pebble Bed Reactor (MPBR) is a high temperature gas-cooled nuclear power reactor. This project investigated the feasibility of using the passive neutron counting and active neutron/gamma counting for the on line fuel burnup measurement for MPBR. To investigate whether there is a correlation between neutron emission and fuel burnup, the MPBR fuel depletion was simulated under different irradiation conditions by ORIGEN2. It was found that the neutron emission from an irradiated pebble increases with burnup super-linearly and reaches to 104 neutron/sec/pebble at the discharge burnup. The photon emission from an irradiated pebble was found to be in the order of 1013 photon/sec/pebble at all burnup levels. Analysis shows that the neutron emission rate of an irradiated pebble is sensitive to its burnup history and the spectral-averaged one-group cross sections used in the depletion calculations, which consequently leads to large uncertainty in the correlation between neutron emission and burnup. At low burnup levels, the uncertainty in the neutron emission/burnup correlation is too high and the neutron emission rate is too low so that it is impossible to determine a pebble's burnup by on-line neutron counting at low burnup levels. At high burnup levels, the uncertainty in the neutron emission rate becomes less but is still large in quantity. However, considering the super-linear feature of the correlation, the uncertainty in burnup determination was found to be ˜7% at the discharge burnup, which is acceptable. Therefore, total neutron emission rate of a pebble can be used as a burnup indicator to determine whether a pebble should be discharged or not. The feasibility of using passive neutron counting methods for the on-line burnup measurement was investigated by using a general Monte Carlo code, MCNP, to assess the detectability of the neutron emission and the capability to discriminate gamma noise by commonly used neutron detectors. It was found that both He-3

  12. Computational prediction of dust production in graphite moderated pebble bed reactors

    NASA Astrophysics Data System (ADS)

    Rostamian, Maziar

    The scope of the work reported here, which is the computational study of graphite wear behavior, supports the Nuclear Engineering University Programs project "Experimental Study and Computational Simulations of Key Pebble Bed Thermomechanics Issues for Design and Safety" funded by the US Department of Energy. In this work, modeling and simulating the contact mechanics, as anticipated in a PBR configuration, is carried out for the purpose of assessing the amount of dust generated during a full power operation year of a PBR. A methodology that encompasses finite element analysis (FEA) and micromechanics of wear is developed to address the issue of dust production and its quantification. Particularly, the phenomenon of wear and change of its rate with sliding length is the main focus of this dissertation. This work studies the wear properties of graphite by simulating pebble motion and interactions of a specific type of nuclear grade graphite, IG-11. This study consists of two perspectives: macroscale stress analysis and microscale analysis of wear mechanisms. The first is a set of FEA simulations considering pebble-pebble frictional contact. In these simulations, the mass of generated graphite particulates due to frictional contact is calculated by incorporating FEA results into Archard's equation, which is a linear correlation between wear mass and wear length. However, the experimental data by Johnson, University of Idaho, revealed that the wear rate of graphite decreases with sliding length. This is because the surfaces of the graphite pebbles become smoother over time, which results in a gradual decrease in wear rate. In order to address the change in wear rate, a more detailed analysis of wear mechanisms at room temperature is presented. In this microscale study, the wear behavior of graphite at the asperity level is studied by simulating the contact between asperities of facing surfaces. By introducing the effect of asperity removal on wear rate, a nonlinear

  13. HTR-PROTEUS PEBBLE BED EXPERIMENTAL PROGRAM CORE 4: RANDOM PACKING WITH A 1:1 MODERATOR-TO-FUEL PEBBLE RATIO

    SciTech Connect

    John D. Bess; Leland M. Montierth

    2013-03-01

    In its deployment as a pebble bed reactor (PBR) critical facility from 1992 to 1996, the PROTEUS facility was designated as HTR-PROTEUS. This experimental program was performed as part of an International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP) on the Validation of Safety Related Physics Calculations for Low Enriched HTGRs. Within this project, critical experiments were conducted for graphite moderated LEU systems to determine core reactivity, flux and power profiles, reaction-rate ratios, the worth of control rods, both in-core and reflector based, the worth of burnable poisons, kinetic parameters, and the effects of moisture ingress on these parameters. One benchmark experiment was evaluated in this report: Core 4. Core 4 represents the only configuration with random pebble packing in the HTR-PROTEUS series of experiments, and has a moderator-to-fuel pebble ratio of 1:1. Three random configurations were performed. The initial configuration, Core 4.1, was rejected because the method for pebble loading, separate delivery tubes for the moderator and fuel pebbles, may not have been completely random; this core loading was rejected by the experimenters. Cores 4.2 and 4.3 were loaded using a single delivery tube, eliminating the possibility for systematic ordering effects. The second and third cores differed slightly in the quantity of pebbles loaded (40 each of moderator and fuel pebbles), stacked height of the pebbles in the core cavity (0.02 m), withdrawn distance of the stainless steel control rods (20 mm), and withdrawn distance of the autorod (30 mm). The 34 coolant channels in the upper axial reflector and the 33 coolant channels in the lower axial reflector were open. Additionally, the axial graphite fillers used in all other HTR-PROTEUS configurations to create a 12-sided core cavity were not used in the randomly packed cores. Instead, graphite fillers were placed on the cavity floor, creating a funnel-like base, to discourage ordering

  14. HTR-PROTEUS PEBBLE BED EXPERIMENTAL PROGRAM CORE 4: RANDOM PACKING WITH A 1:1 MODERATOR-TO-FUEL PEBBLE RATIO

    SciTech Connect

    John D. Bess; Leland M. Montierth

    2014-03-01

    In its deployment as a pebble bed reactor (PBR) critical facility from 1992 to 1996, the PROTEUS facility was designated as HTR-PROTEUS. This experimental program was performed as part of an International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP) on the Validation of Safety Related Physics Calculations for Low Enriched HTGRs. Within this project, critical experiments were conducted for graphite moderated LEU systems to determine core reactivity, flux and power profiles, reaction-rate ratios, the worth of control rods, both in-core and reflector based, the worth of burnable poisons, kinetic parameters, and the effects of moisture ingress on these parameters. One benchmark experiment was evaluated in this report: Core 4. Core 4 represents the only configuration with random pebble packing in the HTR-PROTEUS series of experiments, and has a moderator-to-fuel pebble ratio of 1:1. Three random configurations were performed. The initial configuration, Core 4.1, was rejected because the method for pebble loading, separate delivery tubes for the moderator and fuel pebbles, may not have been completely random; this core loading was rejected by the experimenters. Cores 4.2 and 4.3 were loaded using a single delivery tube, eliminating the possibility for systematic ordering effects. The second and third cores differed slightly in the quantity of pebbles loaded (40 each of moderator and fuel pebbles), stacked height of the pebbles in the core cavity (0.02 m), withdrawn distance of the stainless steel control rods (20 mm), and withdrawn distance of the autorod (30 mm). The 34 coolant channels in the upper axial reflector and the 33 coolant channels in the lower axial reflector were open. Additionally, the axial graphite fillers used in all other HTR-PROTEUS configurations to create a 12-sided core cavity were not used in the randomly packed cores. Instead, graphite fillers were placed on the cavity floor, creating a funnel-like base, to discourage ordering

  15. Feasibility of Burning First- and Second-Generation Plutonium in Pebble Bed High-Temperature Reactors

    SciTech Connect

    Haas, J.B.M. de; Kuijper, J.C

    2005-08-15

    The core physics investigations at the Nuclear Research Consultancy Group in the Netherlands, as part of the activities within the HTR-N project of the European Fifth Framework Program, are focused on the incineration of pure (first- and second-generation) Pu fuels in the reference pebble bed high-temperature gas-cooled reactor (HTR) HTR-MODUL with a continuous reload [MEDUL, (MEhrfach DUrchLauf, multipass)] fueling strategy in which the spherical fuel elements, or pebbles, pass through the core a number of times before being permanently discharged. For pebbles fueled with different loadings of plutonium, the feasibility of a sustained fuel cycle under nominal reactor conditions was investigated by means of the reactivity and temperature coefficients of the reactor. The HTR-MODUL was found to be a very effective reactor to reduce the stockpile of first-generation plutonium. It reduces the amount of plutonium to about one-sixth of the original and reduces the risk of proliferation by denaturing the plutonium vector. For second-generation plutonium the incineration is less favorable, as the amount of plutonium is only halved.

  16. 60Co as AN On-Line Burnup Indicator for Multi-Pass Pebble Bed Reactors

    NASA Astrophysics Data System (ADS)

    Hawari, Ayman I.; Chen, Jianwei

    2003-06-01

    Multi-pass pebble bed reactor concepts are characterized by circulating fuel systems that cycle the pebbles in and out of the core until the burnup limit is reached. Currently modular designs of such reactors, with nominal powers of approximately 300 MW-thermal, are under consideration for deployment internationally. A concern of the proposed designs is the ability to perform online measurements of the fuel burnup to determine whether a pebble has reached its end-of-life burnup limit (~ 80,000 MWD/MTU). In this work, computational simulations were performed to assess the utilization of a passive gamma ray spectrometric approach to perform this task. However, in addition to using the inherent signatures of the irradiated fuel, the use of the 59Co(n,γ)60Co reaction as a burnup indicator is considered. The results show that the activity ratio of 134Cs/60Co can provide an indicator that is accurate to within 5% at burnup greater than 20,000 MWD/MTU as the power is varied between 50% and 200% of the reactor's thermal power.

  17. AN EXPERIMENT TO STUDY PEBBLE BED LIQUID-FLUORIDE-SALT HEAT TRANSFER

    SciTech Connect

    Yoder Jr, Graydon L; Aaron, Adam M; Heatherly, Dennis Wayne; Holcomb, David Eugene; Kisner, Roger A; McCarthy, Mike; Peretz, Fred J; Wilgen, John B; Wilson, Dane F

    2011-01-01

    A forced-convection liquid-fluoride-salt loop is being constructed at Oak Ridge National Laboratory (ORNL). This loop was designed as a versatile experimental facility capable of supporting general thermal/fluid/corrosion testing of liquid fluoride salts. The initial test configuration is designed to support the Pebble Bed Advanced High-Temperature Reactor and incorporates a test section designed to examine the heat transfer behavior of FLiNaK salt in a heated pebble bed. The loop is constructed of Inconel 600 and is capable of operating at up to 700oC. It contains a total of 72 kg of FLiNaK salt and uses an overhung impeller centrifugal sump pump that can provide FLiNaK flow at 4.5 kg/s with a head of 0.125 MPa. The test section is made of silicon carbide (SiC) and contains approximately 600 graphite spheres, 3 cm in diameter. The pebble bed is heated using a unique inductive technique. A forced induction air cooler removes the heat added to the pebble bed. The salt level within the loop is maintained by controlling an argon cover gas pressure. Salt purification is performed in batch mode by transferring the salt from the loop into a specially made nickel crucible system designed to remove oxygen, moisture and other salt impurities. Materials selection for the loop and test section material was informed by 3 months of Inconel 600 and SiC corrosion testing as well as tests examining subcomponent performance in the salt. Several SiC-to-Inconel 600 mechanical joint designs were considered before final salt and gas seals were chosen. Structural calculations of the SiC test section were performed to arrive at a satisfactory test section configuration. Several pump vendors provided potential loop pump designs; however, because of cost, the pump was designed and fabricated in-house. The pump includes a commercial rotating dry gas shaft seal to maintain loop cover gas inventory. The primary instrumentation on the loop includes temperature, pressure, and loop flow rate

  18. Effects of Spatial Variations in Packing Fraction on Reactor Physics Parameters in Pebble-Bed Reactors

    SciTech Connect

    William K. Terry; A. M. Ougouag; Farzad Rahnema; Michael Scott McKinley

    2003-04-01

    The well-known spatial variation of packing fraction near the outer boundary of a pebble-bed reactor core is cited. The ramifications of this variation are explored with the MCNP computer code. It is found that the variation has negligible effects on the global reactor physics parameters extracted from the MCNP calculations for use in analysis by diffusion-theory codes, but for local reaction rates the effects of the variation are naturally important. Included is some preliminary work in using first-order perturbation theory for estimating the effect of the spatial variation of packing fraction on the core eigenvalue and the fision density distribution.

  19. On-line interrogation of pebble bed reactor fuel using passive gamma-ray spectrometry

    NASA Astrophysics Data System (ADS)

    Chen, Jianwei

    The Pebble Bed Reactor (PBR) is a helium-cooled, graphite-moderated high temperature nuclear power reactor. In addition to its inherently safe design, a unique feature of this reactor is its multipass fuel cycle in which graphite fuel pebbles (of varying enrichment) are randomly loaded and continuously circulated through the core until they reach their prescribed end-of-life burnup limit (˜80,000--100,000 MWD/MTU). Unlike the situation with conventional light water reactors (LWRs), depending solely on computational methods to perform in-core fuel management will be highly inaccurate. As a result, an on-line measurement approach becomes the only accurate method to assess whether a particular pebble has reached its end-of-life burnup limit. In this work, an investigation was performed to assess the feasibility of passive gamma-ray spectrometry assay as an approach for on-line interrogation of PBR fuel for the simultaneous determination of burnup and enrichment on a pebble-by-pebble basis. Due to the unavailability of irradiated or fresh pebbles, Monte Carlo simulations were used to study the gamma-ray spectra of the PBR fuel at various levels of burnup. A pebble depletion calculation was performed using the ORIGEN code, which yielded the gamma-ray source term that was introduced into the input of an MCNP simulation. The MCNP simulation assumed the use of a high-purity coaxial germanium detector. Due to the lack of one-group high temperature reactor cross sections for ORIGEN, a heterogeneous MCNP model was developed to describe a typical PBR core. Subsequently, the code MONTEBURNS was used to couple the MCNP model and ORIGEN. This approach allowed the development of the burnup-dependent, one-group spectral-averaged PBR cross sections to be used in the ORIGEN pebble depletion calculation. Based on the above studies, a relative approach for performing the measurements was established. The approach is based on using the relative activities of Np-239/I-132 in combination

  20. Very High Temperature Reactor (VHTR) Deep Burn Core and Fuel Analysis -- Complete Design Selection for the Pebble Bed Reactor

    SciTech Connect

    B. Boer; A. M. Ougouag

    2010-09-01

    The Deep-Burn (DB) concept focuses on the destruction of transuranic nuclides from used light water reactor fuel. These transuranic nuclides are incorporated into TRISO coated fuel particles and used in gas-cooled reactors with the aim of a fractional fuel burnup of 60 to 70% in fissions per initial metal atom (FIMA). This high performance is expected through the use of multiple recirculation passes of the fuel in pebble form without any physical or chemical changes between passes. In particular, the concept does not call for reprocessing of the fuel between passes. In principle, the DB pebble bed concept employs the same reactor designs as the presently envisioned low-enriched uranium core designs, such as the 400 MWth Pebble Bed Modular Reactor (PBMR-400). Although it has been shown in the previous Fiscal Year (2009) that a PuO2 fueled pebble bed reactor concept is viable, achieving a high fuel burnup, while remaining within safety-imposed prescribed operational limits for fuel temperature, power peaking and temperature reactivity feedback coefficients for the entire temperature range, is challenging. The presence of the isotopes 239-Pu, 240-Pu and 241-Pu that have resonances in the thermal energy range significantly modifies the neutron thermal energy spectrum as compared to a ”standard,” UO2-fueled core. Therefore, the DB pebble bed core exhibits a relatively hard neutron energy spectrum. However, regions within the pebble bed that are near the graphite reflectors experience a locally softer spectrum. This can lead to power and temperature peaking in these regions. Furthermore, a shift of the thermal energy spectrum with increasing temperature can lead to increased absorption in the resonances of the fissile Pu isotopes. This can lead to a positive temperature reactivity coefficient for the graphite moderator under certain operating conditions. The effort of this task in FY 2010 has focused on the optimization of the core to maximize the pebble discharge

  1. Estimating anisotropic diffusion of neutrons near the boundary of a pebble bed random system

    SciTech Connect

    Vasques, R.

    2013-07-01

    Due to the arrangement of the pebbles in a Pebble Bed Reactor (PBR) core, if a neutron is located close to a boundary wall, its path length probability distribution function in directions of flight parallel to the wall is significantly different than in other directions. Hence, anisotropic diffusion of neutrons near the boundaries arises. We describe an analysis of neutron transport in a simplified 3-D pebble bed random system, in which we investigate the anisotropic diffusion of neutrons born near one of the system's boundary walls. While this simplified system does not model the actual physical process that takes place near the boundaries of a PBR core, the present work paves the road to a formulation that may enable more accurate diffusion simulations of such problems to be performed in the future. Monte Carlo codes have been developed for (i) deriving realizations of the 3-D random system, and (ii) performing 3-D neutron transport inside the heterogeneous model; numerical results are presented for three different choices of parameters. These numerical results are used to assess the accuracy of estimates for the mean-squared displacement of neutrons obtained with the diffusion approximations of the Atomic Mix Model and of the recently introduced [1] Non-Classical Theory with angular-dependent path length distribution. The Non-Classical Theory makes use of a Generalized Linear Boltzmann Equation in which the locations of the scattering centers in the system are correlated and the distance to collision is not exponentially distributed. We show that the results predicted using the Non-Classical Theory successfully model the anisotropic behavior of the neutrons in the random system, and more closely agree with experiment than the results predicted by the Atomic Mix Model. (authors)

  2. Supplemental Report on Nuclear Safeguards Considerations for the Pebble Bed Modular Reactor (PBMR)

    SciTech Connect

    Moses, David Lewis; Ehinger, Michael H

    2010-05-01

    Recent reports by Department of Energy National Laboratories have discussed safeguards considerations for the low enriched uranium (LEU) fueled Pebble Bed Modular Reactor (PBMR) and the need for bulk accountancy of the plutonium in used fuel. These reports fail to account effectively for the degree of plutonium dilution in the graphitized-carbon pebbles that is sufficient to meet the International Atomic Energy Agency's (IAEA's) 'provisional' guidelines for termination of safeguards on 'measured discards.' The thrust of this finding is not to terminate safeguards but to limit the need for specific accountancy of plutonium in stored used fuel. While the residual uranium in the used fuel may not be judged sufficiently diluted to meet the IAEA provisional guidelines for termination of safeguards, the estimated quantities of {sup 232}U and {sup 236}U in the used fuel at the target burn-up of {approx}91 GWD/MT exceed specification limits for reprocessed uranium (ASTM C787) and will require extensive blending with either natural uranium or uranium enrichment tails to dilute the {sup 236}U content to fall within specification thus making the PBMR used fuel less desirable for commercial reprocessing and reuse than that from light water reactors. Also the PBMR specific activity of reprocessed uranium isotopic mixture and its A{sub 2} values for effective dose limit if released in a dispersible form during a transportation accident are more limiting than the equivalent values for light water reactor spent fuel at 55 GWD/MT without accounting for the presence of the principal carry-over fission product ({sup 99}Tc) and any possible plutonium contamination that may be present from attempted covert reprocessing. Thus, the potentially recoverable uranium from PBMR used fuel carries reactivity penalties and radiological penalties likely greater than those for reprocessed uranium from light water reactors. These factors impact the economics of reprocessing, but a more significant

  3. On the evaluation of pebble bed reactor critical experiments using the PEBBED code

    SciTech Connect

    Hans D. Gougar; R. Sonat Sen

    2001-10-01

    The PEBBED pebble bed reactor fuel management code under development at the Idaho National Laboratory is designed for rapid design and analysis of pebble bed high temperature reactors (PBRs). Embedded within the code are the THERMIX-KONVEK thermal fluid solver and the COMBINE-7 spectrum generation code for inline cross section homogenization. Because 1D symmetry can be found at each stage of core heterogeneity; spherical at TRISO and pebble levels, and cylindrical at the control rod and core levels, the 1-D transport capability of ANISN is assumed to be sufficient in most cases for generating flux solutions for cross section homogenization. Furthermore, it is fast enough to be executed during the analysis or the equilibrium core. Multi-group diffusion-based design codes such as PEBBED and VSOP are not expected to yield the accuracy and resolution of continuous energy Monte Carlo codes for evaluation of critical experiments. Nonetheless, if the preparation of multigroup cross sections can adequately capture the physics of the mixing of PBR fuel elements and leakage from the core, reasonable results may be obtained. In this paper, results of the application of PEBBED to two critical experiments (HTR Proteus and HTR-10) and associated computational models are presented. The embedded 1-D transport solver is shown to capture the double heterogeneity of the pebble fuel in unit cell calculations. Eigenvalue calculations of a whole core are more challenging, particularly if the boron concentration is uncertain. The sensitivity of major safety parameters to variations in modeling assumptions, however, is shown to be minimal. The embedded transport solver can also be used to obtain control rod worths but only with adjustment of the local spectrum. Results are compared to those of other codes as well as Core 4 of the HTR-Proteus experiment which contains partially inserted rods. They indicate the need for a reference solution to adjust the radius of the graphite in the

  4. Pebble bed modular reactor safeguards: developing new approaches and implementing safeguards by design

    SciTech Connect

    Beyer, Brian David; Beddingfield, David H; Durst, Philip; Bean, Robert

    2010-01-01

    The design of the Pebble Bed Modular Reactor (PBMR) does not fit or seem appropriate to the IAEA safeguards approach under the categories of light water reactor (LWR), on-load refueled reactor (OLR, i.e. CANDU), or Other (prismatic HTGR) because the fuel is in a bulk form, rather than discrete items. Because the nuclear fuel is a collection of nuclear material inserted in tennis-ball sized spheres containing structural and moderating material and a PBMR core will contain a bulk load on the order of 500,000 spheres, it could be classified as a 'Bulk-Fuel Reactor.' Hence, the IAEA should develop unique safeguards criteria. In a multi-lab DOE study, it was found that an optimized blend of: (i) developing techniques to verify the plutonium content in spent fuel pebbles, (ii) improving burn-up computer codes for PBMR spent fuel to provide better understanding of the core and spent fuel makeup, and (iii) utilizing bulk verification techniques for PBMR spent fuel storage bins should be combined with the historic IAEA and South African approaches of containment and surveillance to verify and maintain continuity of knowledge of PBMR fuel. For all of these techniques to work the design of the reactor will need to accommodate safeguards and material accountancy measures to a far greater extent than has thus far been the case. The implementation of Safeguards-by-Design as the PBMR design progresses provides an approach to meets these safeguards and accountancy needs.

  5. Plutonium and minor actinide utilisation in a pebble-bed high temperature reactor

    SciTech Connect

    Petrov, B. Y.; Kuijper, J. C.; Oppe, J.; De Haas, J. B. M.

    2012-07-01

    This paper contains results of the analysis of the pebble-bed high temperature gas-cooled PUMA reactor loaded with plutonium and minor actinide (Pu/MA) fuel. Starting from knowledge and experience gained in the Euratom FP5 projects HTR-N and HTR-N1, this study aims at demonstrating the potential of high temperature reactors to utilize or transmute Pu/MA fuel. The work has been performed within the Euratom FP6 project PUMA. A number of different fuel types and fuel configurations have been analyzed and compared with respect to incineration performance and safety-related reactor parameters. The results show the excellent plutonium and minor actinide burning capabilities of the high temperature reactor. The largest degree of incineration is attained in the case of an HTR fuelled by pure plutonium fuel as it remains critical at very deep burnup of the discharged pebbles. Addition of minor actinides to the fuel leads to decrease of the achievable discharge burnup and therefore smaller fraction of actinides incinerated during reactor operation. The inert-matrix fuel design improves the transmutation performance of the reactor, while the 'wallpaper' fuel does not have advantage over the standard fuel design in this respect. After 100 years of decay following the fuel discharge, the total amount of actinides remains almost unchanged for all of the fuel types considered. Among the plutonium isotopes, only the amount of Pu-241 is reduced significantly due to its relatively short half-life. (authors)

  6. Gamma-ray spectrometry analysis of pebble bed reactor fuel using Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Chen, Jianwei; Hawari, Ayman I.; Zhao, Zhongxiang; Su, Bingjing

    2003-06-01

    Monte Carlo simulations were used to study the gamma-ray spectra of pebble bed reactor fuel at various levels of burnup. A fuel depletion calculation was performed using the ORIGEN2.1 code, which yielded the gamma-ray source term that was introduced into the input of an MCNP4C simulation. The simulation assumed the use of a 100% efficient high-purity coaxial germanium (HPGe) detector, a pebble placed at a distance of 100 cm from the detector, and accounted for Gaussian broadening of the gamma-ray peaks. Previously, it was shown that 137Cs, 60Co (introduced as a dopant), and 134Cs are the relevant burnup indicators. The results show that the 662 keV line of 137Cs lies in close proximity to the intense 658 keV of 197Nb, which results in spectral interference between the lines. However, the 1333 keV line of 60Co, and selected 134Cs lines (e.g., at 605 keV) are free from spectral interference, which enhances the possibility of their utilization as relative burnup indicators.

  7. Safeguards Challenges for Pebble-Bed Reactors (PBRs):Peoples Republic of China (PRC)

    SciTech Connect

    Forsberg, Charles W.; Moses, David Lewis

    2009-11-01

    The Peoples Republic of China (PRC) is operating the HTR-10 pebble-bed reactor (PBR) and is in the process of building a prototype PBR plant with two modular reactors (250-MW(t) per reactor) feeding steam to a single turbine-generator. It is likely to be the first modular hightemperature reactor to be ready for commercial deployment in the world because it is a highpriority project for the PRC. The plant design features multiple modular reactors feeding steam to a single turbine generator where the number of modules determines the plant output. The design and commercialization strategy are based on PRC strengths: (1) a rapidly growing electric market that will support low-cost mass production of modular reactor units and (2) a balance of plant system based on economics of scale that uses the same mass-produced turbine-generator systems used in PRC coal plants. If successful, in addition to supplying the PRC market, this strategy could enable China to be the leading exporter of nuclear reactors to developing countries. The modular characteristics of the reactor match much of the need elsewhere in the world. PBRs have major safety advantages and a radically different fuel. The fuel, not the plant systems, is the primary safety system to prevent and mitigate the release of radionuclides under accident conditions. The fuel consists of small (6-cm) pebbles (spheres) containing coatedparticle fuel in a graphitized carbon matrix. The fuel loading per pebble is small (~9 grams of low-enriched uranium) and hundreds of thousands of pebbles are required to fuel a nuclear plant. The uranium concentration in the fuel is an order of magnitude less than in traditional nuclear fuels. These characteristics make the fuel significantly less attractive for illicit use (weapons production or dirty bomb); but, its unusual physical form may require changes in the tools used for safeguards. This report describes PBRs, what is different, and the safeguards challenges. A series of

  8. Reactor Pressure Vessel Temperature Analysis for Prismatic and Pebble-Bed VHTR Designs

    SciTech Connect

    H. D. Gougar; C. B. Davis

    2006-04-01

    Analyses were performed to determine maximum temperatures in the reactor pressure vessel for two potential Very-High Temperature Reactor (VHTR) designs during normal operation and during a depressurized conduction cooldown accident. The purpose of the analyses was to aid in the determination of appropriate reactor vessel materials for the VHTR. The designs evaluated utilized both prismatic and pebble-bed cores that generated 600 MW of thermal power. Calculations were performed for fluid outlet temperatures of 900 and 950 °C, corresponding to the expected range for the VHTR. The analyses were performed using the RELAP5-3D and PEBBED-THERMIX computer codes. Results of the calculations were compared with preliminary temperature limits derived from the ASME pressure vessel code.

  9. Comparative evaluation of pebble-bed and prismatic fueled high-temperature gas-cooled reactors

    SciTech Connect

    Kasten, P.R.; Bartine, D.E.

    1981-01-01

    A comparative evaluation has been performed of the HTGR and the Federal Republic of Germany's Pebble Bed Reactor (PBR) for potential commercial applications in the US. The evaluation considered two reactor sizes (1000 and 3000 MW(t)) and three process applications (steam cycle, direct cycle, and process heat, with outlet coolant temperatures of 750, 850, and 950/sup 0/C, respectively). The primary criterion for the comparison was the levelized (15-year) cost of producing electricity or process heat. Emphasis was placed on the cost impact of differences between the prismatic-type HTGR core, which requires periodic refuelings during reactor shutdowns, and the pebble bed PBR core, which is refueled continuously during reactor operations. Detailed studies of key technical issues using reference HTGR and PBR designs revealed that two cost components contributing to the levelized power costs are higher for the PBR: capital costs and operation and maintenance costs. A third cost component, associated with nonavailability penalties, tended to be higher for the PBR except for the process heat application, for which there is a large uncertainty in the HTGR nonavailability penalty at the 950/sup 0/C outlet coolant temperature. A fourth cost component, fuel cycle costs, is lower for the PBR, but not sufficiently lower to offset the capital cost component. Thus the HTGR appears to be slightly superior to the PBR in economic performance. Because of the advanced development of the HTGR concept, large HTGRs could also be commercialized in the US with lower R and D costs and shorter lead times than could large PBRs. It is recommended that the US gas-cooled thermal reactor program continue giving primary support to the HTGR, while also maintaining its cooperative PBR program with FRG.

  10. In situ tritium recovery behavior from Li 2TiO 3 pebble bed under neutron pulse operation

    NASA Astrophysics Data System (ADS)

    Tsuchiya, K.; Kikukawa, A.; Hoshino, T.; Nakamichi, M.; Yamada, H.; Yamaki, D.; Enoeda, M.; Ishitsuka, E.; Kawamura, H.; Ito, H.; Hayashi, K.

    2004-08-01

    A binary pebble bed of lithium titanate (Li 2TiO 3) was irradiated in the Japan Materials Testing Reactor (JMTR), and its tritium recovery characteristics bed was studied under pulsed neutron operations. The temperature at the outside edge of the pebble bed increased from 300 to 350 °C immediately after the window of hafnium (Hf) neutron absorber was turned toward the reactor core, while the tritium recovery rate increased gradually. The ratio of tritium recovery rate to generation rate at the high-power, ( R/ G) high, approached the saturated value of unity at about 20 h of operation. Overall tritium recovery behavior under the pulsed operation was similar to that under the steady state power operation. An estimated time constant of about 3 h for the tritium recovery was much longer than the thermal time constant of about 100 s.

  11. Final Report on Utilization of TRU TRISO Fuel as Applied to HTR Systems Part I: Pebble Bed Reactors

    SciTech Connect

    Brian Boer; Abderrafi M. Ougouag

    2011-03-01

    The Deep-Burn (DB) concept [ ] focuses on the destruction of transuranic nuclides from used light water reactor (LWR) fuel. These transuranic nuclides are incorporated into tri-isotopic (TRISO) coated fuel particles and used in gas-cooled reactors with the aim of a fractional fuel burnup of 60 to 70% in fissions per initial metal atom (FIMA). This high performance is expected through the use of multiple recirculation passes of the fuel in pebble form without any physical or chemical changes between passes. In particular, the concept does not call for reprocessing of the fuel between passes. In principle, the DB pebble bed concept employs the same reactor designs as the presently envisioned low-enriched uranium core designs, such as the 400 MWth Pebble Bed Modular Reactor (PBMR-400) [ ]. Although it has been shown in the previous Fiscal Year (FY) (2009) that a PuO2 fueled pebble bed reactor concept is viable, achieving a high fuel burnup while remaining within safety-imposed prescribed operational limits for fuel temperature, power peaking, and temperature reactivity feedback coefficients for the entire temperature range, is challenging. The presence of the isotopes 239Pu, 240Pu, and 241Pu that have resonances in the thermal energy range significantly modifies the neutron thermal energy spectrum as compared to a standard, UO2-fueled core. Therefore, the DB pebble bed core exhibits a relatively hard neutron energy spectrum. However, regions within the pebble bed that are near the graphite reflectors experience a locally softer spectrum. This can lead to power and temperature peaking in these regions. Furthermore, a shift of the thermal energy spectrum with increasing temperature can lead to increased absorption in the resonances of the fissile Pu isotopes. This can lead to a positive temperature reactivity coefficient for the graphite moderator under certain operating conditions. Regarding the coated particle performance, the FY 2009 investigations showed that no

  12. Disposition of weapon-grade plutonium with pebble bed type HTGRs using Pu burner balls and Th breeder balls

    SciTech Connect

    Yamashita, Kiyonobu; Tokuhara, Kazumi; Fujimoto, Nozomu; Kunitomi, Kazuhiko

    1996-08-01

    A concept of reactor system was developed with which weapons-grade plutonium could be made perfectly worthless in use for weapons. It is a pebble bed type HTGR using Pu burner ball fuels and Th breeder ball fuels. The residual amounts of {sup 239}Pu in spent Pu balls become less than 1% of the initial loading. Furthermore, a method was found that the power coefficient could be made negative by heavy Pu loading in the Pu burner ball fuels.

  13. TINTE Uncertainty Analysis of the Maximum Fuel Temperature During a DLOFC Event for the 400 MW Pebble Bed Modular Reactor

    SciTech Connect

    Strydom, Gerhard

    2004-07-01

    The Pebble Bed Modular Reactor (PBMR) is a high temperature, helium cooled, graphite moderated pebbled bed reactor, using a multi-pass fuelling scheme. The aim of this paper is to quantify the effects of uncertainties inherent to various reactor and material parameters on the maximum fuel temperature during a De-pressurized Loss of Forced Cooling (DLOFC) event. The data is obtained by using the transient computer code TINTE, which was specifically developed to assess the nuclear and thermal-hydraulic transient behavior of pebble bed high temperature reactor designs. TINTE calculates time-dependent neutron fluxes, heat source distributions and heat transfer rates between solids and gasses in a 2- D r-z geometry to obtain the global transient core temperature behavior. This study is based on the 400 MW PBMR core design status as at April 2003, and includes DLOFC calculations over a wide range of reactor and material parameters. Some of the parameters investigated for their effect on the fuel temperature during the DLOFC are: reactor fission power and decay heat, control rod movements and scram scenarios, coolant mass flow rates and helium coolant and graphite reflector properties (conductivity, emissivity and specific heat capacity). The results of this study indicate that the current estimates for the total DLOFC maximum fuel temperature, for a 400 MW PBMR reactor operating at 105% power, are within an uncertainty band of {+-}107 deg. C for a DLOFC with scram. The three most important parameters influencing the maximum fuel temperatures during a DLOFC are (in sequence of importance): the reactor power level, the amount of decay heat generated by the nuclear fuel after shutdown, and the thermal conductivity of the pebble bed fuel spheres. (author)

  14. Thermo-mechanical Modelling of Pebble Beds in Fusion Blankets and its Implementation by a Return-Mapping Algorithm

    SciTech Connect

    Gan, Yixiang; Kamlah, Marc

    2008-07-01

    In this investigation, a thermo-mechanical model of pebble beds is adopted and developed based on experiments by Dr. Reimann at Forschungszentrum Karlsruhe (FZK). The framework of the present material model is composed of a non-linear elastic law, the Drucker-Prager-Cap theory, and a modified creep law. Furthermore, the volumetric inelastic strain dependent thermal conductivity of beryllium pebble beds is taken into account and full thermo-mechanical coupling is considered. Investigation showed that the Drucker-Prager-Cap model implemented in ABAQUS can not fulfill the requirements of both the prediction of large creep strains and the hardening behaviour caused by creep, which are of importance with respect to the application of pebble beds in fusion blankets. Therefore, UMAT (user defined material's mechanical behaviour) and UMATHT (user defined material's thermal behaviour) routines are used to re-implement the present thermo-mechanical model in ABAQUS. An elastic predictor radial return mapping algorithm is used to solve the non-associated plasticity iteratively, and a proper tangent stiffness matrix is obtained for cost-efficiency in the calculation. An explicit creep mechanism is adopted for the prediction of time-dependent behaviour in order to represent large creep strains in high temperature. Finally, the thermo-mechanical interactions are implemented in a UMATHT routine for the coupled analysis. The oedometric compression tests and creep tests of pebble beds at different temperatures are simulated with the help of the present UMAT and UMATHT routines, and the comparison between the simulation and the experiments is made. (authors)

  15. Performance of a Li 2TiO 3 pebble-bed in the CRITIC-III irradiation

    NASA Astrophysics Data System (ADS)

    Verrall, R. A.; Miller, J. M.; Gierszewski, P.

    2000-09-01

    Lithium metatitanate (Li 2TiO 3) is a candidate material for tritium breeding in fusion reactor pebble-bed blankets. 173 g of Li 2TiO 3 pebbles were irradiated for 334 full power days (FPD) to a burnup of 0.9% 6Li in the CRITIC-III experiment in AECL's NRU reactor. A key objective was to determine tritium release over a wide temperature band from 200°C to 900°C. On-line release and temperature measurements are reported in this paper. New analytical methods led to calculated inventories ranging from 15 wppm average at the lowest temperature of operation (200°C outer surface to 700°C inner surface) to less than 1.2 wppm average at 375°C outer-surface temperature and 875°C inner-surface temperature. The thermocouples indicated that the bed remained stable during the irradiation, which included thermal shocks from 90 reactor shutdowns. From this swept-capsule irradiation, Li 2TiO 3 appears to be a good candidate for fusion blanket pebble-beds.

  16. Preliminary Study of Burnup Characteristics for a Simplified Small Pebble Bed Reactor

    SciTech Connect

    Irwanto, Dwi; Kato, Yukikata; Obara, Toru; Yamanaka, Ichiro

    2010-06-22

    Simplification of the pebble bed reactor by removing the unloading device from the system was peformed. For this reactor design, a suitable fuel-loading scheme is the Peu a Peu (little by little) fueling scheme. In the Peu a Peu modus, there is no unloading device; as such, the fuels are never discharged and remain at the bottom of the core during reactor operation. This means that the burnup cycle and reactivity is controlled by the addition of fuel. The objectives of the the present study were to find a means of carrying out the exact calculations needed to analyze the Peu a Peu fuel-loading scheme and to optimize the fuel composition, and fuel-loading scheme to achieve better burnup characteristics. The Monte Carlo method is used to perform calculations with high accuracy. Before the calculation of the whole core, the analysis for the infinite geometry was performed. The power generated per mass consumed for each combination of the uranium enrichment and packing fraction was analyzed from the parametric survey. By using the optimal value obtained, a whole-core calculation for the small 20 MWth reactor was performed and the criticality and burnup of this design was analyzed.

  17. Preliminary Study of Burnup Characteristics for a Simplified Small Pebble Bed Reactor

    NASA Astrophysics Data System (ADS)

    Irwanto, Dwi; Kato, Yukikata; Yamanaka, Ichiro; Obara, Toru

    2010-06-01

    Simplification of the pebble bed reactor by removing the unloading device from the system was peformed. For this reactor design, a suitable fuel-loading scheme is the Peu à Peu (little by little) fueling scheme. In the Peu à Peu modus, there is no unloading device; as such, the fuels are never discharged and remain at the bottom of the core during reactor operation. This means that the burnup cycle and reactivity is controlled by the addition of fuel. The objectives of the the present study were to find a means of carrying out the exact calculations needed to analyze the Peu à Peu fuel-loading scheme and to optimize the fuel composition, and fuel-loading scheme to achieve better burnup characteristics. The Monte Carlo method is used to perform calculations with high accuracy. Before the calculation of the whole core, the analysis for the infinite geometry was performed. The power generated per mass consumed for each combination of the uranium enrichment and packing fraction was analyzed from the parametric survey. By using the optimal value obtained, a whole-core calculation for the small 20 MWth reactor was performed and the criticality and burnup of this design was analyzed.

  18. Uncertainty and Sensitivity Analyses of a Pebble Bed HTGR Loss of Cooling Event

    DOE PAGESBeta

    Strydom, Gerhard

    2013-01-01

    The Very High Temperature Reactor Methods Development group at the Idaho National Laboratory identified the need for a defensible and systematic uncertainty and sensitivity approach in 2009. This paper summarizes the results of an uncertainty and sensitivity quantification investigation performed with the SUSA code, utilizing the International Atomic Energy Agency CRP 5 Pebble Bed Modular Reactor benchmark and the INL code suite PEBBED-THERMIX. Eight model input parameters were selected for inclusion in this study, and after the input parameters variations and probability density functions were specified, a total of 800 steady state and depressurized loss of forced cooling (DLOFC) transientmore » PEBBED-THERMIX calculations were performed. The six data sets were statistically analyzed to determine the 5% and 95% DLOFC peak fuel temperature tolerance intervals with 95% confidence levels. It was found that the uncertainties in the decay heat and graphite thermal conductivities were the most significant contributors to the propagated DLOFC peak fuel temperature uncertainty. No significant differences were observed between the results of Simple Random Sampling (SRS) or Latin Hypercube Sampling (LHS) data sets, and use of uniform or normal input parameter distributions also did not lead to any significant differences between these data sets.« less

  19. A Preliminary Study of the Effect of Shifts in Packing Fraction on k-effective in Pebble-Bed Reactors

    SciTech Connect

    Ougouag, Abderrafi Mohammed-El-Ami; Terry, William Knox

    2001-09-01

    A preliminary examination of the effect of pebble packing changes on the reactivity of a pebble-bed reactor (PBR) is performed. As a first step, using the MCNP code, the modeling of a PBR core as a continuous and homogenous region is compared to the modeling as a collection of discrete pebbles of equal average fuel density. It is shown that the two modeling approaches give the same trends inasmuch as changes in keff are concerned. It is thus shown that for the purpose of identifying trends in keff changes, the use of a homogeneous model is sufficient. A homogenous model is then used to assess the effect of pebble packing arrangement changes on the reactivity of a PBR core. It is shown that the changes can be large enough to result in prompt criticality. It is shown that for uranium fueled PBRs, thermal feedback could have the potential to offset the increase in activity, whereas for plutonium fueled systems, thermal feedback may not be sufficient for totally offsetting the packing-increase reactivity insertion and could even exacerbate the initial response. It is thus shown that a full study, including reactor kinetics, thermal feedback, and the dynamics of energy deposition and removal is warranted to fully characterize the potential consequences of packing shifts.

  20. Design of Complex Systems to Achieve Passive Safety: Natural Circulation Cooling of Liquid Salt Pebble Bed Reactors

    NASA Astrophysics Data System (ADS)

    Scarlat, Raluca Olga

    This dissertation treats system design, modeling of transient system response, and characterization of individual phenomena and demonstrates a framework for integration of these three activities early in the design process of a complex engineered system. A system analysis framework for prioritization of experiments, modeling, and development of detailed design is proposed. Two fundamental topics in thermal-hydraulics are discussed, which illustrate the integration of modeling and experimentation with nuclear reactor design and safety analysis: thermal-hydraulic modeling of heat generating pebble bed cores, and scaled experiments for natural circulation heat removal with Boussinesq liquids. The case studies used in this dissertation are derived from the design and safety analysis of a pebble bed fluoride salt cooled high temperature nuclear reactor (PB-FHR), currently under development in the United States at the university and national laboratories level. In the context of the phenomena identification and ranking table (PIRT) methodology, new tools and approaches are proposed and demonstrated here, which are specifically relevant to technology in the early stages of development, and to analysis of passive safety features. A system decomposition approach is proposed. Definition of system functional requirements complements identification and compilation of the current knowledge base for the behavior of the system. Two new graphical tools are developed for ranking of phenomena importance: a phenomena ranking map, and a phenomena identification and ranking matrix (PIRM). The functional requirements established through this methodology were used for the design and optimization of the reactor core, and for the transient analysis and design of the passive natural circulation driven decay heat removal system for the PB-FHR. A numerical modeling approach for heat-generating porous media, with multi-dimensional fluid flow is presented. The application of this modeling

  1. Analysis of the impact of random summing on passive assay of pebble bed reactor fuel using gamma-ray spectrometry

    NASA Astrophysics Data System (ADS)

    Chen, J.; Hawari, A. I.

    2007-08-01

    Pebble bed reactors (PBR) are characterized by multi-pass fuel systems in which spherical fuel pebbles are circulated through the core until they reach a proposed burnup limit. The fuel is assayed on-line to ensure that the burnup limit is not breached. However, random summing effects can impact the response of the burnup measurement system and result in distortions that degrade the accuracy of the assay results. Monte Carlo analysis was performed to estimate the magnitude and effect of random summing on the absolute and relative indicators that have been identified as usable in on-line assay. For a throughput rate of 10 5 counts/s and trapezoidal pulse shaping of the signals, the results show that absolute indicators suffer from severe distortions due to this effect. Relative indicators are found to be resistant to random summing with the deviation in the ratio of peak areas remaining less than 5-15% depending on pulse width.

  2. Irradiation of lithium zirconate pebble-bed in BEATRIX-II Phase II

    NASA Astrophysics Data System (ADS)

    Verrall, R. A.; Slagle, O. D.; Hollenberg, G. W.; Kurasawa, T.; Sullivan, J. D.

    1994-09-01

    BEATRIX-II was an in-situ tritium recovery experiment that was designed to characterize the behavior of lithium ceramics irradiated to a high burnup, and to assess their suitability for use in a fusion reactor blanket. This paper describes the results from the vented canister containing 29.47 g of lithium zirconate spheres packed in a bed 13.2 mm OD, 2.3 mm ID and 103 mm long. The enriched lithium spheres (85% 6Li) were irradiated to a burnup of 5.2% (total lithium) in a steep temperature profile -400°C edge, 1100°C center. The sweep gas was He-O.1% H 2, with systematic tests using alternate compositions: He-0.01% H 2 and pure He (maximum duration 8 days). Tritium recovery decreased slightly at lower H 2 concentrations; for example, the buildup of inventory during a 4-day test in pure He was 0.8 Ci, approximately 6.5% of the tritium generated in the lithium zirconate during that period. The steadiness of the bed central temperature and the tritium release rate, together with low moisture release indicate good performance of the zirconate bed.

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

    NASA Astrophysics Data System (ADS)

    Fratoni, Massimiliano

    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

  4. PEBBLES Mechanics Simulation Speedup

    SciTech Connect

    Joshua J. Cogliati; Abderrafi M. Ougouag

    2010-05-01

    Pebble bed reactors contain large numbers of spherical fuel elements arranged randomly. Determining the motion and location of these fuel elements is required for calculating certain parameters of pebble bed reactor operation. These simulations involve hundreds of thousands of pebbles and involve determining the entire core motion as pebbles are recirculated. Single processor algorithms for this are insufficient since they would take decades to centuries of wall-clock time. This paper describes the process of parallelizing and speeding up the PEBBLES pebble mechanics simulation code. Both shared memory programming with the Open Multi-Processing API and distributed memory programming with the Message Passing Interface API are used in simultaneously in this process. A new shared memory lock-less linear time collision detection algorithm is described. This method allows faster detection of pebbles in contact than generic methods. These combine to make full recirculations on AVR sized reactors possible in months of wall clock time.

  5. The correction of pebble bed reactor nodal cross sections for the effects of leakage and depletion history

    NASA Astrophysics Data System (ADS)

    Hudson, Nathanael Harrison

    An accurate and computationally fast method to generate nodal cross sections for the Pebble Bed Reactor (PBR) was presented. In this method, named Spectral History Correction (SHC), a set of fine group microscopic cross section libraries, pre-computed at specified depletion and moderation states, was coupled with the nodal nuclide densities and group bucklings to compute the new fine group spectrum for each node. The relevant fine group cross-section library was then recollapsed to the local broad group cross-section structure with this new fine group spectrum. This library set was tracked in terms of fuel isotopic densities. Fine group modulation factors (to correct the homogeneous flux for heterogeneous effects) and fission spectra were also stored with the cross section library. As the PBR simulation converges to a steady state fuel cycle, the initial nodal cross section library becomes inaccurate due to the burnup of the fuel and the neutron leakage into and out of the node. Because of the recirculation of discharged fuel pebbles with fresh fuel pebbles, a node can consist of a collection of pebbles at various burnup stages. To account for the nodal burnup, the microscopic cross sections were combined with nodal averaged atom densities to approximate the fine group macroscopic cross-sections for that node. These constructed, homogeneous macroscopic cross sections within the node were used to calculate a numerical solution for the fine group spectrum with B1 theory. This new fine spectrum was used to collapse the pre-computed microscopic cross section library to the broad group structure employed by the fuel cycle code. This SHC technique was developed and practically implemented as a subroutine within the PBR fuel cycle code PEBBED. The SHC subroutine was called to recalculate the broad group cross sections during the code convergence. The result was a fast method that compared favorably to the benchmark scheme of cross section calculation with the lattice

  6. Direct Deterministic Method for Neutronics Analysis and Computation of Asymptotic Burnup Distribution in a Recirculating Pebble-Bed Reactor

    SciTech Connect

    Terry, William Knox; Gougar, Hans D; Ougouag, Abderrafi Mohammed-El-Ami

    2002-07-01

    A new deterministic method has been developed for the neutronics analysis of a pebble-bed reactor (PBR). The method accounts for the flow of pebbles explicitly and couples the flow to the neutronics. The method allows modeling of once-through cycles as well as cycles in which pebbles are recirculated through the core an arbitrary number of times. This new work is distinguished from older methods by the systematically semi-analytical approach it takes. In particular, whereas older methods use the finite-difference approach (or an equivalent one) for the discretization and the solution of the burnup equation, the present work integrates the relevant differential equation analytically in discrete and complementary sub-domains of the reactor. Like some of the finite-difference codes, the new method obtains the asymptotic fuel-loading pattern directly, without modeling any intermediate loading pattern. This is a significant advantage for the design and optimization of the asymptotic fuel-loading pattern. The new method is capable of modeling directly both the once-through-then-out fuel cycle and the pebble recirculating fuel cycle. Although it currently includes a finite-difference neutronics solver, the new method has been implemented into a modular code that incorporates the framework for the future coupling to an efficient solver such as a nodal method and to modern cross section preparation capabilities. In its current state, the deterministic method presented here is capable of quick and efficient design and optimization calculations for the in-core PBR fuel cycle. The method can also be used as a practical "scoping" tool. It could, for example, be applied to determine the potential of the PBR for resisting nuclear-weapons proliferation and to optimize proliferation-resistant features. However, the purpose of this paper is to show that the method itself is viable. Refinements to the code are under way, with the objective of producing a powerful reactor physics

  7. Automated spectral zones selection methodology for diffusion theory data preparation for pebble bed reactor analysis

    NASA Astrophysics Data System (ADS)

    Mphahlele, Ramatsemela

    A methodology is developed for the determination of the optimum spectral zones in Pebble Bed Reactors (PBR). In this work a spectral zone is defined as a zone made up of a number of nodes whose characteristics are collectively similar and that are assigned the same few-group diffusion constants. In other words the spectral zones are the regions over which the few-group diffusion parameters are generated. The identification of spectral boundaries is treated as an optimization problem. It is solved by systematically and simultaneously repositioning all zone boundaries to achieve the global minimum error between the reference transport solution (MCNP) and the diffusion code solution (NEM). The objective function for the optimization algorithm is the total reaction rate error, which is defined as the sum of the leakage, absorption and fission reaction rates error in each zone. An iterative determination of group-dependent bucklings is incorporated into the methodology to properly account for spectral effects of neighboring zones. A preferred energy group structure has also been chosen. This optimization approach with the reference transport solution has proved to be accurate and consistent, however the computational effort required to complete the optimization process is significant. Thus a more practical methodology is also developed for the determination of the spectral zones in PBRs. The reactor physics characteristics of the spectral zones have been studied to understand the nature of the spectral zone boundaries. The practical tool involves the use of spectral indices based on few-group diffusion theory whole core calculations. With this methodology, there is no need to first have a reference transport solution. It is shown that the diffusion-theory coarse group fluxes and the effective multiplication factor computed using zones based on the practical index agrees within a narrow tolerance with those of the reference approach. Therefore the "practical" index

  8. An earthquake transient method for pebble-bed reactors and a fuel temperature model for TRISO fueled reactors

    NASA Astrophysics Data System (ADS)

    Ortensi, Javier

    This investigation is divided into two general topics: (1) a new method for analyzing the safe shutdown earthquake event in a pebble bed reactor core, and (2) the development of an explicit tristructural-isotropic fuel model for high temperature reactors. The safe shutdown earthquake event is one of the design basis accidents for the pebble bed reactor. The new method captures the dynamic geometric compaction of the pebble bed core. The neutronic and thermal-fluids grids are dynamically re-meshed to simulate the re-arrangement of the pebbles in the reactor during the earthquake. Results are shown for the PBMR-400 assuming it is subjected to the Idaho National Laboratory's design basis earthquake. The study concludes that the PBMR-400 can safely withstand the reactivity insertions induced by the slumping of the core and the resulting relative withdrawal of the control rods. This characteristic stems from the large negative Doppler feedback of the fuel. This Doppler feedback mechanism is a major contributor to the passive safety of gas-cooled, graphite-moderated, high-temperature reactors that use fuel based on TRISO particles. The correct prediction of the magnitude and time-dependence of this feedback effect is essential to the conduct of safety analyses for these reactors. An explicit TRISO fuel temperature model named THETRIS has been developed in this work and incorporated in the CYNOD-THERMIX-KONVEK suite of coupled codes. The new model yields similar results to those obtained with more complex methods, requiring multi-TRISO calculations within one control volume. The performance of the code during fast and moderately-slow transients is verified. These analyses show how explicit TRISO models improve the predictions of the fuel temperature, and consequently, of the power escalation. In addition, a brief study of the potential effects on the transient behavior of high-temperature reactors due to the presence of a gap inside the TRISO particles is included

  9. Characteristics of Li 2O pebbles fabricated by the melting granulation method

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Kunihiko; Kawamura, Hiroshi; Nakamichi, Masaru; Imaizumi, Hideki; Saito, Minoru; Kanzawa, Tohru; Nagakura, Masaaki

    1995-03-01

    Lithium ceramics have been considered as candidates for solid breeder materials for fusion reactors. In lithium ceramics, lithium oxide (Li 2O) is one of the best tritium breeders from the standpoint of high lithium density and high thermal conductivity. Recently, several studies have been carried out on the fabrication of small, spherical Li 2O forms to reduce the induced thermal stress in the breeder. A mass-production process for making small pebbles was developed using the melting granulation method. In the present work, the characteristics of Li 2O pebbles fabricated by this method, and mass transfer properties within a Li 2O pebble bed, are discussed.

  10. Design of Complex Systems to Achieve Passive Safety: Natural Circulation Cooling of Liquid Salt Pebble Bed Reactors

    NASA Astrophysics Data System (ADS)

    Scarlat, Raluca Olga

    This dissertation treats system design, modeling of transient system response, and characterization of individual phenomena and demonstrates a framework for integration of these three activities early in the design process of a complex engineered system. A system analysis framework for prioritization of experiments, modeling, and development of detailed design is proposed. Two fundamental topics in thermal-hydraulics are discussed, which illustrate the integration of modeling and experimentation with nuclear reactor design and safety analysis: thermal-hydraulic modeling of heat generating pebble bed cores, and scaled experiments for natural circulation heat removal with Boussinesq liquids. The case studies used in this dissertation are derived from the design and safety analysis of a pebble bed fluoride salt cooled high temperature nuclear reactor (PB-FHR), currently under development in the United States at the university and national laboratories level. In the context of the phenomena identification and ranking table (PIRT) methodology, new tools and approaches are proposed and demonstrated here, which are specifically relevant to technology in the early stages of development, and to analysis of passive safety features. A system decomposition approach is proposed. Definition of system functional requirements complements identification and compilation of the current knowledge base for the behavior of the system. Two new graphical tools are developed for ranking of phenomena importance: a phenomena ranking map, and a phenomena identification and ranking matrix (PIRM). The functional requirements established through this methodology were used for the design and optimization of the reactor core, and for the transient analysis and design of the passive natural circulation driven decay heat removal system for the PB-FHR. A numerical modeling approach for heat-generating porous media, with multi-dimensional fluid flow is presented. The application of this modeling

  11. Optimization of coupled multiphysics methodology for safety analysis of pebble bed modular reactor

    NASA Astrophysics Data System (ADS)

    Mkhabela, Peter Tshepo

    The research conducted within the framework of this PhD thesis is devoted to the high-fidelity multi-physics (based on neutronics/thermal-hydraulics coupling) analysis of Pebble Bed Modular Reactor (PBMR), which is a High Temperature Reactor (HTR). The Next Generation Nuclear Plant (NGNP) will be a HTR design. The core design and safety analysis methods are considerably less developed and mature for HTR analysis than those currently used for Light Water Reactors (LWRs). Compared to LWRs, the HTR transient analysis is more demanding since it requires proper treatment of both slower and much longer transients (of time scale in hours and days) and fast and short transients (of time scale in minutes and seconds). There is limited operation and experimental data available for HTRs for validation of coupled multi-physics methodologies. This PhD work developed and verified reliable high fidelity coupled multi-physics models subsequently implemented in robust, efficient, and accurate computational tools to analyse the neutronics and thermal-hydraulic behaviour for design optimization and safety evaluation of PBMR concept The study provided a contribution to a greater accuracy of neutronics calculations by including the feedback from thermal hydraulics driven temperature calculation and various multi-physics effects that can influence it. Consideration of the feedback due to the influence of leakage was taken into account by development and implementation of improved buckling feedback models. Modifications were made in the calculation procedure to ensure that the xenon depletion models were accurate for proper interpolation from cross section tables. To achieve this, the NEM/THERMIX coupled code system was developed to create the system that is efficient and stable over the duration of transient calculations that last over several tens of hours. Another achievement of the PhD thesis was development and demonstration of full-physics, three-dimensional safety analysis

  12. Cynod: A Neutronics Code for Pebble Bed Modular Reactor Coupled Transient Analysis

    SciTech Connect

    Hikaru Hiruta; Abderrafi M. Ougouag; Hans D. Gougar; Javier Ortensi

    2008-09-01

    The Pebble Bed Reactor (PBR) is one of the two concepts currently considered for development into the Next Generation Nuclear Plant (NGNP). This interest is due, in particular, to the concept’s inherent safety characteristics. In order to verify and confirm the design safety characteristics of the PBR computational tools must be developed that treat the range of phenomena that are expected to be important for this type of reactors. This paper presents a recently developed 2D R-Z cylindrical nodal kinetics code and shows some of its capabilities by applying it to a set of known and relevant benchmarks. The new code has been coupled to the thermal hydraulics code THERMIX/KONVEK[1] for application to the simulation of very fast transients in PBRs. The new code, CYNOD, has been written starting with a fixed source solver extracted from the nodal cylindrical geometry solver contained within the PEBBED code. The fixed source solver was then incorporated into a kinetic solver.. The new code inherits the spatial solver characteristics of the nodal solver within PEBBED. Thus, the time-dependent neutron diffusion equation expressed analytically in each node of the R-Z cylindrical geometry sub-domain (or node) is transformed into one-dimensional equations by means of the usual transverse integration procedure. The one-dimensional diffusion equations in each of the directions are then solved using the analytic Green’s function method. The resulting equations for the entire domain are then re-cast in the form of the Direct Coarse Mesh Finite Difference (D-CMFD) for convenience of solution. The implicit Euler method is used for the time variable discretization. In order to correctly treat the cusping effect for nodes that contain a partially inserted control rod a method is used that takes advantage of the Green’s function solution available in the intrinsic method. In this corrected treatment, the nodes are re-homogenized using axial flux shapes reconstructed based on the

  13. HTR-PROTEUS PEBBLE BED EXPERIMENTAL PROGRAM CORES 9 & 10: COLUMNAR HEXAGONAL POINT-ON-POINT PACKING WITH A 1:1 MODERATOR-TO-FUEL PEBBLE RATIO

    SciTech Connect

    John D. Bess

    2013-03-01

    PROTEUS is a zero-power research reactor based on a cylindrical graphite annulus with a central cylindrical cavity. The graphite annulus remains basically the same for all experimental programs, but the contents of the central cavity are changed according to the type of reactor being investigated. Through most of its service history, PROTEUS has represented light-water reactors, but from 1992 to 1996 PROTEUS was configured as a pebble-bed reactor (PBR) critical facility and designated as HTR-PROTEUS. The nomenclature was used to indicate that this series consisted of High Temperature Reactor experiments performed in the PROTEUS assembly. During this period, seventeen critical configurations were assembled and various reactor physics experiments were conducted. These experiments included measurements of criticality, differential and integral control rod and safety rod worths, kinetics, reaction rates, water ingress effects, and small sample reactivity effects (Ref. 3). HTR-PROTEUS was constructed, and the experimental program was conducted, for the purpose of providing experimental benchmark data for assessment of reactor physics computer codes. Considerable effort was devoted to benchmark calculations as a part of the HTR-PROTEUS program. References 1 and 2 provide detailed data for use in constructing models for codes to be assessed. Reference 3 is a comprehensive summary of the HTR-PROTEUS experiments and the associated benchmark program. This document draws freely from these references. Only Cores 9 and 10 are evaluated in this benchmark report due to similarities in their construction. The other core configurations of the HTR-PROTEUS program are evaluated in their respective reports as outlined in Section 1.0. Cores 9 and 10 were evaluated and determined to be acceptable benchmark experiments.

  14. HTR-PROTEUS PEBBLE BED EXPERIMENTAL PROGRAM CORES 9 & 10: COLUMNAR HEXAGONAL POINT-ON-POINT PACKING WITH A 1:1 MODERATOR-TO-FUEL PEBBLE RATIO

    SciTech Connect

    John D. Bess

    2014-03-01

    PROTEUS is a zero-power research reactor based on a cylindrical graphite annulus with a central cylindrical cavity. The graphite annulus remains basically the same for all experimental programs, but the contents of the central cavity are changed according to the type of reactor being investigated. Through most of its service history, PROTEUS has represented light-water reactors, but from 1992 to 1996 PROTEUS was configured as a pebble-bed reactor (PBR) critical facility and designated as HTR-PROTEUS. The nomenclature was used to indicate that this series consisted of High Temperature Reactor experiments performed in the PROTEUS assembly. During this period, seventeen critical configurations were assembled and various reactor physics experiments were conducted. These experiments included measurements of criticality, differential and integral control rod and safety rod worths, kinetics, reaction rates, water ingress effects, and small sample reactivity effects (Ref. 3). HTR-PROTEUS was constructed, and the experimental program was conducted, for the purpose of providing experimental benchmark data for assessment of reactor physics computer codes. Considerable effort was devoted to benchmark calculations as a part of the HTR-PROTEUS program. References 1 and 2 provide detailed data for use in constructing models for codes to be assessed. Reference 3 is a comprehensive summary of the HTR-PROTEUS experiments and the associated benchmark program. This document draws freely from these references. Only Cores 9 and 10 are evaluated in this benchmark report due to similarities in their construction. The other core configurations of the HTR-PROTEUS program are evaluated in their respective reports as outlined in Section 1.0. Cores 9 and 10 were evaluated and determined to be acceptable benchmark experiments.

  15. A uranium bed with ceramic body for tritium storage

    SciTech Connect

    Khapov, A.S.; Grishechkin, S.K.; Kiselev, V.G.

    2015-03-15

    It is widely recognized that ceramic coatings provide an attractive solution to lower tritium permeation in structural materials. Alumina based ceramic coatings have the highest permeation reduction factor for hydrogen. For this reason an attempt was made to apply crack-free low porous ceramics as a structural material of a bed body for tritium storage in a setup used for hydrogenating neutron tube targets at VNIIA. The present article introduces the design of the bed. This bed possesses essentially a lower hydrogen permeation factor than traditionally beds with stainless steel body. Bed heating in order to recover hydrogen from the bed is suggested to be implemented by high frequency induction means. Inductive heating allows decreasing the time necessary for tritium release from the bed as well as power consumption. Both of these factors mean less thermal power release into glove box where a setup for tritium handling is installed and thus causes fewer problems with pressure regulations inside the glove box. Inductive heating allows raising tritium sorbent material temperature up to melting point. The latter allows achieving nearly full tritium recovery.

  16. KUGEL: a thermal, hydraulic, fuel performance, and gaseous fission product release code for pebble bed reactor core analysis

    SciTech Connect

    Shamasundar, B.I.; Fehrenbach, M.E.

    1981-05-01

    The KUGEL computer code is designed to perform thermal/hydraulic analysis and coated-fuel particle performance calculations for axisymmetric pebble bed reactor (PBR) cores. This computer code was developed as part of a Department of Energy (DOE)-funded study designed to verify the published core performance data on PBRs. The KUGEL code is designed to interface directly with the 2DB code, a two-dimensional neutron diffusion code, to obtain distributions of thermal power, fission rate, fuel burnup, and fast neutron fluence, which are needed for thermal/hydraulic and fuel performance calculations. The code is variably dimensioned so that problem size can be easily varied. An interpolation routine allows variable mesh size to be used between the 2DB output and the two-dimensional thermal/hydraulic calculations.

  17. Experimental Study and Computational Simulations of Key Pebble Bed Thermo-mechanics Issues for Design and Safety

    SciTech Connect

    Tokuhiro, Akira; Potirniche, Gabriel; Cogliati, Joshua; Ougouag, Abderrafi

    2014-07-08

    An experimental and computational study, consisting of modeling and simulation (M&S), of key thermal-mechanical issues affecting the design and safety of pebble-bed (PB) reactors was conducted. The objective was to broaden understanding and experimentally validate thermal-mechanic phenomena of nuclear grade graphite, specifically, spheres in frictional contact as anticipated in the bed under reactor relevant pressures and temperatures. The contact generates graphite dust particulates that can subsequently be transported into the flowing gaseous coolent. Under postulated depressurization transients and with the potential for leaked fission products to be adsorbed onto graphite 'dust', there is the potential for fission products to escape from the primary volume. This is a design safety concern. Furthermore, earlier safety assessment identified the distinct possibility for the dispersed dust to combust in contact with air if sufficient conditions are met. Both of these phenomena were noted as important to design review and containing uncertainty to warrant study. The team designed and conducted two separate effects tests to study and benchmark the potential dust-generation rate, as well as study the conditions under which a dust explosion may occure in a standardized, instrumented explosion chamber.

  18. Porous Structure Analysis of the Packed Beds in a High-Temperature Reactor Pebble Bed Modules Heat Transfer Test Facility

    NASA Astrophysics Data System (ADS)

    Ren, Cheng; Yang, Xing-Tuan; Sun, Yan-Fei

    2013-02-01

    We analyse the porous structure of the packed beds in the heat transfer test facility built for high temperature gas cooled reactors from several aspects, such as oscillatory porosity, average porosity, thickness effect, coordination number and contact angle. An understanding and comparison of the porous structure of the facility bed and the real reactor core are developed to make recommendations for the design and analysis of the heat transfer test facility. The results show that there is very little difference between the porous characteristics of the two packed beds of spheres.

  19. Aerobic degradation of a mixture of azo dyes in a packed bed reactor having bacteria-coated laterite pebbles.

    PubMed

    Senan, Resmi C; Shaffiqu, T S; Roy, J Jegan; Abraham, T Emilia

    2003-01-01

    A microbial consortium capable of aerobic degradation of a mixture of azo dyes consisting of two isolated strains (RRL,TVM) and one known strain of Pseudomonas putida (MTCC 1194) was immobilized on laterite stones. The amount of bacterial biomass attached to the laterite stones was 8.64 g per 100 g of the stone on a dry weight basis. The packed bed reactor was filled with these stones and had a total capacity of 850 mL and a void volume of 210 mL. The feed consisted of an equal mixture of seven azo dyes both in water as well as in a simulated textile effluent, at a pH of 9.0 and a salinity of 900 mg/L. The dye concentrations of influent were 25, 50, and 100 microg/mL. The residence time was varied between 0.78 and 6.23 h. It was found that at the lowest residence time 23.55, 45.73, and 79.95 microg of dye was degraded per hour at an initial dye concentration of 25, 50, and 100 microg, respectively. The pH was reduced from 9.0 to 7.0. Simulated textile effluent containing 50 microg/mL dye was degraded by 61.7%. Analysis of degradation products by TLC and HPLC showed that the dye mixture was degraded to nontoxic smaller molecules. The bacteria-coated pebbles were stable, there was no washout even after 2 months, and the reactor was found to be suitable for the aerobic degradation of azo dyes. PMID:12675610

  20. PEBBLES Simulation of Static Friction and New Static Friction Benchmark

    SciTech Connect

    Joshua J. Cogliati; Abderrafi M. Ougouag

    2010-05-01

    Pebble bed reactors contain large numbers of spherical fuel elements arranged randomly. Determining the motion and location of these fuel elements is required for calculating certain parameters of pebble bed reactor operation. This paper documents the PEBBLES static friction model. This model uses a three dimensional differential static friction approximation extended from the two dimensional Cundall and Strack model. The derivation of determining the rotational transformation of pebble to pebble static friction force is provided. A new implementation for a differential rotation method for pebble to container static friction force has been created. Previous published methods are insufficient for pebble bed reactor geometries. A new analytical static friction benchmark is documented that can be used to verify key static friction simulation parameters. This benchmark is based on determining the exact pebble to pebble and pebble to container static friction coefficients required to maintain a stable five sphere pyramid.

  1. Experimental Determination of the Ratio of {sup 238}U Capture to {sup 235}U Fission in LEU-HTR Pebble-Bed Configurations

    SciTech Connect

    Koeberl, O.; Chawla, R.

    2004-01-15

    The shift toward low-enrichment uranium (LEU) fuel for gas-cooled high-temperature reactors (HTRs) has revealed a lack of experimental data for validating neutronics codes that are used for the design and licensing of such systems. In the framework of the LEU-HTR experimental program at the PROTEUS critical facility, the safety-related effects of accidental moderation increase (ingress of water or other hydrogeneous compounds) in pebble-bed HTR core configurations employing low-enriched (16.7%) fuel were investigated. An important neutron balance component in this context is the integral reaction rate ratio of {sup 238}U capture (C{sub 8}) relative to {sup 235}U fission (F{sub 5}).It was necessary to develop new experimental techniques for the accurate measurement of C{sub 8}/F{sub 5} in the doubly heterogeneous fuel pebbles. These have involved the utilization of specially prepared particle foils on the one hand and the counting of whole fuel pebbles on the other. Core-center measurements employing both experimental methods have been carried out in two different HTR-PROTEUS configurations (with and without accidental moderation increase simulation, respectively). In each case, satisfactory agreement was obtained between the experimental results based on the two techniques. By carrying out a comparison of particle-foil C{sub 8}/F{sub 5} measurements in the PROTEUS reactor's thermal column with the results of standard foil-activation measurement techniques, the systematic uncertainty (1{sigma}) of the core-center measurements could be reduced by {approx}0.6%, yielding a net experimental error of {+-}1% with either of the new methods. A comparison of the experimental results with calculations based on the MICROX-2/TWODANT codes in conjunction with JEF-1 cross sections has indicated that this calculational route overpredicts the core-center C{sub 8}/F{sub 5} value by {approx}2.5% in both the investigated configurations.

  2. The Transient 3-D Transport Coupled Code TORT-TD/ATTICA3D for High-Fidelity Pebble-Bed HTGR Analyses

    NASA Astrophysics Data System (ADS)

    Seubert, Armin; Sureda, Antonio; Lapins, Janis; Bader, Johannes; Laurien, Eckart

    2012-01-01

    This article describes the 3D discrete ordinates-based coupled code system TORT-TD/ATTICA3D that aims at steady state and transient analyses of pebble-bed high-temperature gas cooled reactors. In view of increasing computing power, the application of time-dependent neutron transport methods becomes feasible for best estimate evaluations of safety margins. The calculation capabilities of TORT-TD/ATTICA3D are presented along with the coupling approach, with focus on the time-dependent neutron transport features of TORT-TD. Results obtained for the OECD/NEA/NSC PBMR-400 benchmark demonstrate the transient capabilities of TORT-TD/ATTICA3D.

  3. Analytical Solution of Fick's Law of the TRISO-Coated Fuel Particles and Fuel Elements in Pebble-Bed High Temperature Gas-Cooled Reactors

    NASA Astrophysics Data System (ADS)

    Cao, Jian-Zhu; Fang, Chao; Sun, Li-Feng

    2011-05-01

    Two kinds of approaches are built to solve the fission products diffusion models (Fick's equation) based on sphere fuel particles and sphere fuel elements exactly. Two models for homogenous TRISO-coated fuel particles and fuel elements used in pebble-bed high temperature gas-cooled reactors are presented, respectively. The analytical solution of Fick's equation for fission products diffusion in fuel particles is derived by variables separation. In the fuel element system, a modification of the diffusion coefficient from D to D/r is made to characterize the difference of diffusion rates in distinct areas and it is shown that the Laplace and Hankel transformations are effective as the diffusion coefficient in Fick's equation is dependant on the radius of the fuel element. Both the solutions are useful for the prediction of the fission product behaviors and could be programmed in the corresponding engineering calculations.

  4. MHD oxidant intermediate temperature ceramic heater study

    NASA Technical Reports Server (NTRS)

    Carlson, A. W.; Chait, I. L.; Saari, D. P.; Marksberry, C. L.

    1981-01-01

    The use of three types of directly fired ceramic heaters for preheating oxygen enriched air to an intermediate temperature of 1144K was investigated. The three types of ceramic heaters are: (1) a fixed bed, periodic flow ceramic brick regenerative heater; (2) a ceramic pebble regenerative heater. The heater design, performance and operating characteristics under conditions in which the particulate matter is not solidified are evaluated. A comparison and overall evaluation of the three types of ceramic heaters and temperature range determination at which the particulate matter in the MHD exhaust gas is estimated to be a dry powder are presented.

  5. Fabrication of Li2TiO3 pebbles using PVA-boric acid reaction for solid breeding materials

    NASA Astrophysics Data System (ADS)

    Park, Yi-Hyun; Cho, Seungyon; Ahn, Mu-Young

    2014-12-01

    Lithium metatitanate (Li2TiO3) is a candidate breeding material of the Helium Cooled Ceramic Reflector (HCCR) Test Blanket Module (TBM). The breeding material is used in pebble-bed form to reduce the uncertainty of the interface thermal conductance. In this study, Li2TiO3 pebbles were successfully fabricated by the slurry droplet wetting method using the cross-linking reaction between polyvinyl alcohol (PVA) and boric acid. The effects of fabrication parameters on the shaping of Li2TiO3 green body were investigated. In addition, the basic characteristics of the sintered pebble were also evaluated. The shape of Li2TiO3 green bodies was affected by slurry viscosity, PVA content and boric acid content. The grain size and average crush load of sintered Li2TiO3 pebble were controlled by the sintering time. The boron was completely removed during the final sintering process.

  6. A Hydrodynamic Investigation of Instream Pebble Clusters in Gravel-Bed Rivers With Implications for Fish Habitat

    NASA Astrophysics Data System (ADS)

    Lacey, R. J.; Roy, A. G.

    2006-05-01

    There does not appear to be a straight forward relationship between fish behaviour and in-stream large roughness elements such as boulders and pebble clusters. Studies have found increased salmonid densities following the placement of boulder clusters attributed to increased habitat complexity - variability in depth, cover, and current velocity. Yet laboratory bioenergetics studies have indicated that the complex environment induced by added boulders and cobbles reduces drift feeding and increases energy expenditure in juvenile salmon. These somewhat conflicting results may be related to an inadequate representation of the hydrodynamics associated with the large roughness elements in the studies. Most ecological fish habitat studies do not include a full or even a partial characterization of the turbulent flow dynamics even though positive relationships have been found between the swimming costs of salmonids and flow turbulence. This study provides a spatial description of the turbulent flow field associated with a naturally formed instream pebble cluster with a relative roughness of 0.3. The mean streamwise velocity and water depth at the time of measurement were 73 cm/s, and 35 cm, respectively. The hydrodynamic characterization presented here may aid in understanding the mechanisms involved in the linkage between large roughness elements and salmon productivity. Instantaneous high frequency velocities were measured using the simultaneous deployment of four acoustic Doppler velocimeters. Streamwise component mean velocities are reduced to near zero values in the near wake of the pebble cluster while turbulent kinetic energy values increase by a factor of approximately 2.0 compared with velocities outside the wake. The vertical velocity spectra estimated from measurements within the wake zone contain a marked peak at approximately 1.5 Hz associated with eddies shedding from the shear layer in the lee of the cluster. Turbulent events detected using the U

  7. HTR-PROTEUS PEBBLE BED EXPERIMENTAL PROGRAM CORES 5, 6, 7, & 8: COLUMNAR HEXAGONAL POINT-ON-POINT PACKING WITH A 1:2 MODERATOR-TO-FUEL PEBBLE RATIO

    SciTech Connect

    John D. Bess

    2013-03-01

    PROTEUS is a zero-power research reactor based on a cylindrical graphite annulus with a central cylindrical cavity. The graphite annulus remains basically the same for all experimental programs, but the contents of the central cavity are changed according to the type of reactor being investigated. Through most of its service history, PROTEUS has represented light-water reactors, but from 1992 to 1996 PROTEUS was configured as a pebble-bed reactor (PBR) critical facility and designated as HTR-PROTEUS. The nomenclature was used to indicate that this series consisted of High Temperature Reactor experiments performed in the PROTEUS assembly. During this period, seventeen critical configurations were assembled and various reactor physics experiments were conducted. These experiments included measurements of criticality, differential and integral control rod and safety rod worths, kinetics, reaction rates, water ingress effects, and small sample reactivity effects (Ref. 3). HTR-PROTEUS was constructed, and the experimental program was conducted, for the purpose of providing experimental benchmark data for assessment of reactor physics computer codes. Considerable effort was devoted to benchmark calculations as a part of the HTR-PROTEUS program. References 1 and 2 provide detailed data for use in constructing models for codes to be assessed. Reference 3 is a comprehensive summary of the HTR-PROTEUS experiments and the associated benchmark program. This document draws freely from these references. Only Cores 9 and 10 are evaluated in this benchmark report due to similarities in their construction. The other core configurations of the HTR-PROTEUS program are evaluated in their respective reports as outlined in Section 1.0. Cores 9 and 10 were evaluated and determined to be acceptable benchmark experiments.

  8. HTR-Proteus Pebble Bed Experimental Program Cores 5,6,7,&8: Columnar Hexagonal Point-on-Point Packing with a 1:2 Moderator-to-Fuel Pebble Ratio

    SciTech Connect

    Bess, John D.; Sterbentz, James W.; Snoj, Luka; Lengar, Igor; Koberl, Oliver

    2015-03-01

    PROTEUS is a zero-power research reactor based on a cylindrical graphite annulus with a central cylindrical cavity. The graphite annulus remains basically the same for all experimental programs, but the contents of the central cavity are changed according to the type of reactor being investigated. Through most of its service history, PROTEUS has represented light-water reactors, but from 1992 to 1996 PROTEUS was configured as a pebble-bed reactor (PBR) critical facility and designated as HTR-PROTEUS. The nomenclature was used to indicate that this series consisted of High Temperature Reactor experiments performed in the PROTEUS assembly. During this period, seventeen critical configurations were assembled and various reactor physics experiments were conducted. These experiments included measurements of criticality, differential and integral control rod and safety rod worths, kinetics, reaction rates, water ingress effects, and small sample reactivity effects (Ref. 3). HTR-PROTEUS was constructed, and the experimental program was conducted, for the purpose of providing experimental benchmark data for assessment of reactor physics computer codes. Considerable effort was devoted to benchmark calculations as a part of the HTR-PROTEUS program. References 1 and 2 provide detailed data for use in constructing models for codes to be assessed. Reference 3 is a comprehensive summary of the HTR-PROTEUS experiments and the associated benchmark program. This document draws freely from these references. Only Cores 9 and 10 are evaluated in this benchmark report due to similarities in their construction. The other core configurations of the HTR-PROTEUS program are evaluated in their respective reports as outlined in Section 1.0. Cores 9 and 10 were evaluated and determined to be acceptable benchmark experiments.

  9. CERAMIC FILTER TESTS AT THE EPA/EXXON PFBC (PRESSURIZED FLUIDIZED BED COAL COMBUSTION) MINIPLANT

    EPA Science Inventory

    The paper describes the performance of the Acurex ceramic bag filter operating at temperatures up to 880C and pressures up to 930 kPa on particulate-laden flue gas from a pressurized fluidized-bed coal combustion (PFBC) unit on a slipstream of gas taken after the second stage cyc...

  10. Correlation between the processes of water desorption and tritium release from Li4SiO4 ceramic pebbles

    NASA Astrophysics Data System (ADS)

    Ran, Guangming; Xiao, Chengjian; Chen, Xiaojun; Gong, Yu; Kang, Chunmei; Wang, Xiaolin

    2015-11-01

    The correlation between water desorption and tritium release from Li4SiO4 pebbles was studied by temperature programmed desorption. The released water and tritium from irradiated samples were monitored simultaneously. The main peak for tritium release from the irradiated samples that were exposed to air for more than a month, was shifted from 500 to about 250 °C, as compared to that from the unexposed samples. The peak temperatures for water desorption and tritium release overlapped very well, suggesting a strong correlation between the two processes. Accordingly, a two-step mechanism, involving isotope exchange between the tritium trapped on the grain surface and the surface hydroxyls (-OH), and subsequent desorption of tritiated water through recombination of the -OH/-OT groups, was proposed to explain the tritium release behavior for the air-exposed samples. It is believed that the formation and desorption of surface hydroxyl groups at 200-300 °C can affect the behavior of tritium release from Li4SiO4 significantly.

  11. Status and perspective of the R&D on ceramic breeder materials for testing in ITER

    NASA Astrophysics Data System (ADS)

    Ying, A.; Akiba, M.; Boccaccini, L. V.; Casadio, S.; Dell'Orco, G.; Enoeda, M.; Hayashi, K.; Hegeman, J. B.; Knitter, R.; van der Laan, J.; Lulewicz, J. D.; Wen, Z. Y.

    2007-08-01

    The main line of ceramic breeder materials research and development is based on the use of the breeder material in the form of pebble beds. At present, there are three candidate pebble materials (Li 4SiO 4, and two forms of Li 2TiO 3) for DEMO reactors that will be used for testing in ITER. This paper reviews the R&D of as-fabricated pebble materials against the blanket performance requirements and makes recommendations on necessary steps toward the qualification of these materials for testing in ITER.

  12. Pebble Bed Reactor Power Systems for Lunar Outposts: Long Operation Life and End-of Life Storage

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

    The Pellet Bed Reactor(PeBR) and power system for supporting future lunar outposts offer many desirable design, operation and safety features and address post operation storage of spent nuclear fuel. In addition to its long, full power operation life of 66 year, the PeBR is launched without fuel and loaded after placement below grade on the lunar surface with spherical fuel pellets, designed to fully contain fission products. The fuel pellets(~1.0 cm dia.) are launched separately in subcritical canisters. The post-operation PeBR is stored below grade for > 300 year to allow the radioactivity in the spent fuel to decay to a sufficiently low level. The PeBR power system, designed for avoidance of single point failures in reactor cooling and energy conversion, nominally generates ~100 kWe at a thermal efficiency of ~ 21%. In addition to the sectored reactor core, it uses three Closed Brayton Cycle loops with centrifugal flow turbo-machines for energy conversion and He-Xe(40 g/mol) binary gas mixture working fluid and reactor coolant.

  13. Development Status of the PEBBLES Code for Pebble Mechanics: Improved Physical Models and Speed-up

    SciTech Connect

    Joshua J. Cogliati; Abderrafi M. Ougouag

    2009-09-01

    PEBBLES is a code for simulating the motion of all the pebbles in a pebble bed reactor. Since pebble bed reactors are packed randomly and not precisely placed, the location of the fuel elements in the reactor is not deterministically known. Instead, when determining operating parameters the motion of the pebbles can be simulated and stochastic locations can be found. The PEBBLES code can output information relevant for other simulations of the pebble bed reactors such as the positions of the pebbles in the reactor, packing fraction change in an earthquake, and velocity profiles created by recirculation. The goal for this level three milestone was to speedup the PEBBLES code through implementation on massively parallel computer. Work on this goal has resulted in speeding up both the single processor version and creation of a new parallel version of PEBBLES. Both the single processor version and the parallel running capability of the PEBBLES code have improved since the fiscal year start. The hybrid MPI/OpenMP PEBBLES version was created this year to run on the increasingly common cluster hardware profile that combines nodes with multiple processors that share memory and a cluster of nodes that are networked together. The OpenMP portions use the Open Multi-Processing shared memory parallel processing model to split the task across processors in a single node that shares memory. The Message Passing Interface (MPI) portion uses messages to communicate between different nodes over a network. The following are wall clock speed up for simulating an NGNP-600 sized reactor. The single processor version runs 1.5 times faster compared to the single processor version at the beginning of the fiscal year. This speedup is primarily due to the improved static friction model described in the report. When running on 64 processors, the new MPI/OpenMP hybrid version has a wall clock speed up of 22 times compared to the current single processor version. When using 88 processors, a

  14. Development Status of the PEBBLES Code for Pebble Mechanics: Improved Physical Models and Speed-up

    SciTech Connect

    Joshua J. Cogliati; Abderrafi M. Ougouag

    2009-12-01

    PEBBLES is a code for simulating the motion of all the pebbles in a pebble bed reactor. Since pebble bed reactors are packed randomly and not precisely placed, the location of the fuel elements in the reactor is not deterministically known. Instead, when determining operating parameters the motion of the pebbles can be simulated and stochastic locations can be found. The PEBBLES code can output information relevant for other simulations of the pebble bed reactors such as the positions of the pebbles in the reactor, packing fraction change in an earthquake, and velocity profiles created by recirculation. The goal for this level three milestone was to speedup the PEBBLES code through implementation on massively parallel computer. Work on this goal has resulted in speeding up both the single processor version and creation of a new parallel version of PEBBLES. Both the single processor version and the parallel running capability of the PEBBLES code have improved since the fiscal year start. The hybrid MPI/OpenMP PEBBLES version was created this year to run on the increasingly common cluster hardware profile that combines nodes with multiple processors that share memory and a cluster of nodes that are networked together. The OpenMP portions use the Open Multi-Processing shared memory parallel processing model to split the task across processors in a single node that shares memory. The Message Passing Interface (MPI) portion uses messages to communicate between different nodes over a network. The following are wall clock speed up for simulating an NGNP-600 sized reactor. The single processor version runs 1.5 times faster compared to the single processor version at the beginning of the fiscal year. This speedup is primarily due to the improved static friction model described in the report. When running on 64 processors, the new MPI/OpenMP hybrid version has a wall clock speed up of 22 times compared to the current single processor version. When using 88 processors, a

  15. Granular-bed and ceramic candle filters in commercial plants: A comparison

    SciTech Connect

    Wilson, K.B.; Haas, J.C.; Eshelman, M.B.

    1993-04-01

    Advanced coal fired power cycles require the removal of coal ash at high temperature and pressure. Granular-bed and ceramic candle filters can be used for this service. Conceptual designs for commercial size applications are made for each type of filter. The filters are incorporated in the design of a Foster Wheeler 450 MWe second generation pressurized fluidized bed combustion plant which contains a pressurized fluidized combustor and carbonizer. In a second application, the inters are incorporated in the design of a 100 MWe KRW (air) gasifier based power plant. The candle filter design is state of the art as determined from the open literature with an effort to minimize the cost. The granular-bed filter design is based on test work performed at high temperature and low pressure, tests at New York University performed at high pressure and temperate, and new analysis used to simplify the scale up of the filter and reduce overall cost. The incorporation of chemically reactive granites in the granular-bed filter for the removal of additional coal derived contaminants such as alkali or sulfur is considered. The conceptual designs of the granular-bed inter and the ceramic candle filter are compared in terms of the cost of electricity, capital cost, and operating and maintenance costs for each application.

  16. Image reconstruction of single photon emission computed tomography (SPECT) on a pebble bed reactor (PBR) using expectation maximization and exact inversion algorithms: Comparison study by means of numerical phantom

    SciTech Connect

    Razali, Azhani Mohd Abdullah, Jaafar

    2015-04-29

    Single Photon Emission Computed Tomography (SPECT) is a well-known imaging technique used in medical application, and it is part of medical imaging modalities that made the diagnosis and treatment of disease possible. However, SPECT technique is not only limited to the medical sector. Many works are carried out to adapt the same concept by using high-energy photon emission to diagnose process malfunctions in critical industrial systems such as in chemical reaction engineering research laboratories, as well as in oil and gas, petrochemical and petrochemical refining industries. Motivated by vast applications of SPECT technique, this work attempts to study the application of SPECT on a Pebble Bed Reactor (PBR) using numerical phantom of pebbles inside the PBR core. From the cross-sectional images obtained from SPECT, the behavior of pebbles inside the core can be analyzed for further improvement of the PBR design. As the quality of the reconstructed image is largely dependent on the algorithm used, this work aims to compare two image reconstruction algorithms for SPECT, namely the Expectation Maximization Algorithm and the Exact Inversion Formula. The results obtained from the Exact Inversion Formula showed better image contrast and sharpness, and shorter computational time compared to the Expectation Maximization Algorithm.

  17. Image reconstruction of single photon emission computed tomography (SPECT) on a pebble bed reactor (PBR) using expectation maximization and exact inversion algorithms: Comparison study by means of numerical phantom

    NASA Astrophysics Data System (ADS)

    Razali, Azhani Mohd; Abdullah, Jaafar

    2015-04-01

    Single Photon Emission Computed Tomography (SPECT) is a well-known imaging technique used in medical application, and it is part of medical imaging modalities that made the diagnosis and treatment of disease possible. However, SPECT technique is not only limited to the medical sector. Many works are carried out to adapt the same concept by using high-energy photon emission to diagnose process malfunctions in critical industrial systems such as in chemical reaction engineering research laboratories, as well as in oil and gas, petrochemical and petrochemical refining industries. Motivated by vast applications of SPECT technique, this work attempts to study the application of SPECT on a Pebble Bed Reactor (PBR) using numerical phantom of pebbles inside the PBR core. From the cross-sectional images obtained from SPECT, the behavior of pebbles inside the core can be analyzed for further improvement of the PBR design. As the quality of the reconstructed image is largely dependent on the algorithm used, this work aims to compare two image reconstruction algorithms for SPECT, namely the Expectation Maximization Algorithm and the Exact Inversion Formula. The results obtained from the Exact Inversion Formula showed better image contrast and sharpness, and shorter computational time compared to the Expectation Maximization Algorithm.

  18. Formation and accumulation of radiation-induced defects and radiolysis products in modified lithium orthosilicate pebbles with additions of titanium dioxide

    NASA Astrophysics Data System (ADS)

    Zarins, Arturs; Valtenbergs, Oskars; Kizane, Gunta; Supe, Arnis; Knitter, Regina; Kolb, Matthias H. H.; Leys, Oliver; Baumane, Larisa; Conka, Davis

    2016-03-01

    Lithium orthosilicate (Li4SiO4) pebbles with 2.5 wt.% excess of silicon dioxide (SiO2) are the European Union's designated reference tritium breeding ceramics for the Helium Cooled Pebble Bed (HCPB) Test Blanket Module (TBM). However, the latest irradiation experiments showed that the reference Li4SiO4 pebbles may crack and form fragments under operation conditions as expected in the HCPB TBM. Therefore, it has been suggested to change the chemical composition of the reference Li4SiO4 pebbles and to add titanium dioxide (TiO2), to obtain lithium metatitanate (Li2TiO3) as a second phase. The aim of this research was to investigate the formation and accumulation of radiation-induced defects (RD) and radiolysis products (RP) in the modified Li4SiO4 pebbles with different contents of TiO2 for the first time, in order to estimate and compare radiation stability. The reference and the modified Li4SiO4 pebbles were irradiated with accelerated electrons (E = 5 MeV) up to 5000 MGy absorbed dose at 300-990 K in a dry argon atmosphere. By using electron spin resonance (ESR) spectroscopy it was determined that in the modified Li4SiO4 pebbles, several paramagnetic RD and RP are formed and accumulated, like, E' centres (SiO33-/TiO33-), HC2 centres (SiO43-/TiO3-) etc. On the basis of the obtained results, it is concluded that the modified Li4SiO4 pebbles with TiO2 additions have comparable radiation stability with the reference pebbles.

  19. Integrated low emissions cleanup system for direct coal fueled turbines (moving bed, fluid bed contactor/ceramic filter)

    SciTech Connect

    Newby, R.A.; Alvin, M.A.; Bachovchin, D.M.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1992-10-20

    The United States Department of Energy, Morgantown Energy Research Center (DOE/METC), is sponsoring the development of direct coal-fired turbine power plants as part of their Heat Engines program. A major technical challenge remaining for the development of the direct coal-fired turbine is high-temperature combustion gas cleaning to meet environmental standards for sulfur oxides and particulate emissions, as well as to provide acceptable turbine life. The Westinghouse Electric Corporation, Science Technology Center, is evaluating two Integrated Low Emissions Cleanup (ILEC) concepts that have been configured to meat this technical challenge: a baseline ceramic barrier filter ILEC concept, and a fluidized bed ILEC concept. These ILEC concepts simultaneously control sulfur, particulate, and alkali contaminants in the high-pressure combustion gases at turbine inlet temperatures up to 2300[degree]F. This document reports the status of a program in the nineteenth quarter to develop this ILEC technology for direct coal-fired turbine power plants.

  20. Integrated low emissions cleanup system for direct coal fueled turbines (Moving bed, fluid bed contactor/ceramic filter)

    SciTech Connect

    Newby, R.A.; Alvin, M.A.; Bachovchin, D.M.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1992-01-20

    The United States Department of Energy, Morgantown Energy Research Center (DOE/METC), is sponsoring the development of direct coal-fired turbine power plants as part of their Heat Engines program. A major technical challenge remaining for the development of the direct coal-fired turbine is high-temperature combustion gas cleaning to meet environmental standards for sulfur oxides and particulate emissions, as well as to provide acceptable turbine life. The Westinghouse Electric Corporation, Science Technology Center, is evaluating two Integrated Low Emissions Cleanup (ILEC) concepts that have been configured to meet this technical challenge: a baseline ceramic barrier filter ILEC concept, and a fluidized bed ILEC concept. These ILEC concepts simultaneously control sulfur, particulate, and alkali contaminants in the high-pressure combustion gases at turbine inlet temperatures up to 2300{degrees}F. This document reports the status of a program in the seventeenth quarter to develop this ILEC technology for direct coal-fired turbine power plants.

  1. Mechanisms of flow through compressible porous beds in sedimentation, centrifugation, deliquoring, and ceramic processing

    SciTech Connect

    1996-01-25

    The major topics covered in the investigation include: centrifugation; cake filtration; sedimentation and thickening; capillary suction operations; ceramics, slip casting; optimization studies; and wastewater. The research program was aimed at the specific areas of solid/liquid separation including sedimentation, thickening, cake filtration, centrifugation, expression, washing, deep-bed filtration, screening, and membrane separation. Unification of the theoretical approaches to the various solid/liquid separation operations was the principle objective of the research. Exploring new aspects of basic separation mechanisms, verification of theory with experiment, development of laboratory procedures for obtaining data for design, optimizing operational methods, and transferring the results to industry were part of the program.

  2. Oxidation/corrosion of metallic and ceramic materials in an aluminum remelt furnace. [For fluidized bed waste heat recovery systems

    SciTech Connect

    Federer, J.I.; Jones, P.J.

    1985-12-01

    Both metallic alloys and ceramic materials are candidates for the distributor plate and other components of fluidized bed waste heat recovery (FBWHR) systems. Eleven Fe-, Ni-, and Co-base alloys were exposed to air at elevated temperatures in laboratory furnaces and to flue gases in an aluminum remelt furnace to assess their resistance to oxidation and corrosion. Four SiC ceramics and two oxide ceramics were also tested in the aluminum remelt furnace. Some alloys were coated with aluminum or SiO2 by commercial processes in an effort to enhance their oxidation and corrosion resistance.

  3. Integrated low emissions cleanup system for direct coal fueled turbines (moving bed, fluid bed contactor/ceramic filter)

    SciTech Connect

    Newby, R.A.; Alvin, M.A.; Bachovchin, D.M.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1992-04-20

    The United States Department of Energy, Morgantown Energy Research Center (DOE/METC), is sponsoring the development of direct coal-fired turbine power plants as part of their Heat Engines program. A major technical challenge remaining for the development of the direct coal-fired turbine is high-temperature combustion gas cleaning to meet environmental standards for sulfur oxides and particulate emissions, as well as to provide acceptable turbine life. The Westinghouse Electric Corporation, Science Technology Center, is evaluating two Integrated Low Emissions Cleanup (ILEC) concepts that have been configured to meet this technical challenge: a baseline ceramic barrier filter nEC concept, and a fluidized bed ILEC concept. These ILEC concepts simultaneously control sulfur, particulate, and alkali contaminants in the high-pressure combustion gases at turbine inlet temperatures up to 2300[degrees]F. This document reports the status of a program in the eighteenth quarter to develop this ILEC technology for direct coal-fired turbine power plants.

  4. "Smart pebble" designs for sediment transport monitoring

    NASA Astrophysics Data System (ADS)

    Valyrakis, Manousos; Alexakis, Athanasios; Pavlovskis, Edgars

    2015-04-01

    Sediment transport, due to primarily the action of water, wind and ice, is one of the most significant geomorphic processes responsible for shaping Earth's surface. It involves entrainment of sediment grains in rivers and estuaries due to the violently fluctuating hydrodynamic forces near the bed. Here an instrumented particle, namely a "smart pebble", is developed to investigate the exact flow conditions under which individual grains may be entrained from the surface of a gravel bed. This could lead in developing a better understanding of the processes involved, focusing on the response of the particle during a variety of flow entrainment events. The "smart pebble" is a particle instrumented with MEMS sensors appropriate for capturing the hydrodynamic forces a coarse particle might experience during its entrainment from the river bed. A 3-axial gyroscope and accelerometer registers data to a memory card via a microcontroller, embedded in a 3D-printed waterproof hollow spherical particle. The instrumented board is appropriately fit and centred into the shell of the pebble, so as to achieve a nearly uniform distribution of the mass which could otherwise bias its motion. The "smart pebble" is powered by an independent power to ensure autonomy and sufficiently long periods of operation appropriate for deployment in the field. Post-processing and analysis of the acquired data is currently performed offline, using scientific programming software. The performance of the instrumented particle is validated, conducting a series of calibration experiments under well-controlled laboratory conditions.

  5. Two-Player Graph Pebbling

    NASA Astrophysics Data System (ADS)

    Prudente, Matthew James

    Given a graph G with pebbles on the vertices, we define a pebbling move as removing two pebbles from a vertex u, placing one pebble on a neighbor v, and discarding the other pebble, like a toll. The pebbling number pi( G) is the least number of pebbles needed so that every arrangement of pi(G) pebbles can place a pebble on any vertex through a sequence of pebbling moves. We introduce a new variation on graph pebbling called two-player pebbling. In this, players called the mover and the defender alternate moves, with the stipulation that the defender cannot reverse the previous move. The mover wins only if they can place a pebble on a specified vertex and the defender wins if the mover cannot. We define η(G), analogously, as the minimum number of pebbles such that given every configuration of the η( G) pebbles and every specified vertex r, the mover has a winning strategy. First, we will investigate upper bounds for η( G) on various classes of graphs and find a certain structure for which the defender has a winning strategy, no matter how many pebbles are in a configuration. Then, we characterize winning configurations for both players on a special class of diameter 2 graphs. Finally, we show winning configurations for the mover on paths using a recursive argument.

  6. "Smart pebble" design for environmental monitoring applications

    NASA Astrophysics Data System (ADS)

    Valyrakis, Manousos; Pavlovskis, Edgars

    2014-05-01

    Sediment transport, due to primarily the action of water, wind and ice, is one of the most significant geomorphic processes responsible for shaping Earth's surface. It involves entrainment of sediment grains in rivers and estuaries due to the violently fluctuating hydrodynamic forces near the bed. Here an instrumented particle, namely a "smart pebble", is developed to investigate the exact flow conditions under which individual grains may be entrained from the surface of a gravel bed. This could lead in developing a better understanding of the processes involved, while focusing on the response of the particle during a variety of flow entrainment events. The "smart pebble" is a particle instrumented with MEMS sensors appropriate for capturing the hydrodynamic forces a coarse particle might experience during its entrainment from the river bed. A 3-axial gyroscope and accelerometer registers data to a memory card via a microcontroller, embedded in a 3D-printed waterproof hollow spherical particle. The instrumented board is appropriately fit and centred into the shell of the pebble, so as to achieve a nearly uniform distribution of the mass which could otherwise bias its motion. The "smart pebble" is powered by an independent power to ensure autonomy and sufficiently long periods of operation appropriate for deployment in the field. Post-processing and analysis of the acquired data is currently performed offline, using scientific programming software. The performance of the instrumented particle is validated, conducting a series of calibration experiments under well-controlled laboratory conditions. "Smart pebble" allows for a wider range of environmental sensors (e.g. for environmental/pollutant monitoring) to be incorporated so as to extend the range of its application, enabling accurate environmental monitoring which is required to ensure infrastructure resilience and preservation of ecological health.

  7. Ceramic candle filter performance at the Grimethorpe (UK) Pressurized Fluidized Bed Combustor

    SciTech Connect

    Stringer, J. ); Leitch, A.J. )

    1992-04-01

    A pilot hot-gas particulate removal system, based on positive porous ceramic filters, has been tested on the Grimethorpe Pressurized Fluidized Bed Combustor facility. The filters are in the form of closed-ended tubes, 1.5 m long: These are generally called candles. The dust accumulates on the outside of the cradles, and is periodically removed by a pulse of air into the candle interior, which then flows outward through the candle wall in the reverse direction to the normal flow of the combustion gas. The EPRI system contained a maximum of 130 candles, which is approximately equivalent to the requirement for 7 MW(e) capacity, depending on the filter-operating parameters. The filter unit operated for a total of 860 h under PFBC conditions, of which 790 h were at defined process conditions, typically 850{degrees}C and 10 bar. The amount of gas flowing through each filter element was varied, and the time between cleaning pulses also was varied. The pressure drop through each filter element rose as the dust accumulated on the outer wall, and recovered after the cleaning pulse.

  8. Mechanisms of flow through compressible porous beds in sedimentation, filtration, centrifugation, deliquoring, and ceramic processing

    SciTech Connect

    Tiller, F.M.

    1992-06-01

    The University of Houston research program is aimed at the specific area of solid/liquid separation including sedimentation, thickening, cake filtration, centrifugation, expression, washing, deep-bed filtration, screening, and membrane separation. Unification of the theoretical approaches to the various solid/liquid separation operations is the principle objective of the research. Exploring new aspects of basic separation mechanisms, verification of theory with experiment, development of laboratory procedures for obtaining data for design, optimizing operational methods, and transferring the results to industry are a part of the Houston program. New methodology developed in our program now permits an engineer or scientist to handle thickening, cake filtration, centrigual filtration, and expression in a unified manner. The same fundamental equations are simply adapted to the differing parameters and conditions related to the various modes of separation. As the system is flexible and adaptable to computational software, new developments can continually be added. Discussions of the various research projects in this report have been kept to a minimum and are principally qualitative. The length of the report would be excessive if each topic were covered in depth. Although the number of research topics may appear larger than one would expect, many are closely interconnected and reflect our philosophy of working in apparently diverse fields such as ceramics, mining, wastewater, food, chemical processing, and oil well operations.

  9. Process for preparing crystalline ceramic superconductor materials by fluidized-bed calcination

    SciTech Connect

    Mihalich, H.C.

    1990-06-05

    This patent describes the process for preparing crystalline ceramic superconductor materials from a mixture of ceramic superconductor precursors selected to form upon heat processing a crystalline ceramic superconductor material. It comprises: preparing the mixture from solid particulate ceramic superconductor precursors; subjecting the mixture to calcination at an elevated reaction temperature sufficient to form a crystalline material while entraining and fluidizing the mixture in a flow of hot calcining gas; quenching the crystalline ceramic material to below calcination temperature; and annealing and cooling the crystalline ceramic material obtained after quenching in the presence of oxygen to form a superconducting a crystalline structure.

  10. PEBBLES Operation and Theory Manual

    SciTech Connect

    Joshua J. Cogliati

    2010-09-01

    The PEBBLES manual describes the PEBBLES code. The PEBBLES code is a computer program designed to simulation the motion, packing and vibration of spheres that undergo various mechanical forces including gravitation, Hooke’s law force and various friction forces. The frictional forces include true static friction that allows non-zero angles of repose. Each pebble is individually simulated using the distinct element method.

  11. PEBBLES Operation and Theory Manual

    SciTech Connect

    Joshua J. Cogliati

    2011-02-01

    The PEBBLES manual describes the PEBBLES code. The PEBBLES code is a computer program designed to simulation the motion, packing and vibration of spheres that undergo various mechanical forces including gravitation, Hooke’s law force and various friction forces. The frictional forces include true static friction that allows non-zero angles of repose. Each pebble is individually simulated using the distinct element method.

  12. Matrix Formulation of Pebble Circulation in the PEBBED Code

    SciTech Connect

    Gougar, Hans D; Terry, William Knox; Ougouag, Abderrafi Mohammed-El-Ami

    2002-04-01

    The PEBBED technique provides a foundation for equilibrium fuel-cycle analysis and optimization in pebble-bed cores in which the fuel elements are continuously flowing and, if desired, recirculating. In addition to the modern analysis techniques used in, or being developed for, the code, PEBBED incorporates a novel nuclide-mixing algorithm that allows for sophisticated recirculation patterns using a matrix generated from basic core parameters. Derived from a simple partitioning of the pebble flow, the elements of the recirculation matrix are used to compute the spatially averaged density of each nuclide at the entry plane from the nuclide densities of pebbles emerging from the discharge conus. The order of the recirculation matrix is a function of the flexibility and sophistication of the fuel handling mechanism. This formulation for coupling pebble flow and neutronics enables core design and fuel cycle optimization to be performed by manipulating a few key core parameters. The formulation is amenable to modern optimization techniques.

  13. Pebble Puzzle Solved

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Figure 1 In the quest to determine if a pebble was jamming the rock abrasion tool on NASA's Mars Exploration Rover Opportunity, scientists and engineers examined this up-close, approximate true-color image of the tool. The picture was taken by the rover's panoramic camera, using filters centered at 601, 535, and 482 nanometers, at 12:47 local solar time on sol 200 (August 16, 2004).

    Colored spots have been drawn on this image corresponding to regions where panoramic camera reflectance spectra were acquired (see chart in Figure 1). Those regions are: the grinding wheel heads (yellow); the rock abrasion tool magnets (green); the supposed pebble (red); a sunlit portion of the aluminum rock abrasion tool housing (purple); and a shadowed portion of the rock abrasion tool housing (brown). These spectra demonstrated that the composition of the supposed pebble was clearly different from that of the sunlit and shadowed portions of the rock abrasion tool, while similar to that of the dust-coated rock abrasion tool magnets and grinding heads. This led the team to conclude that the object disabling the rock abrasion tool was indeed a martian pebble.

  14. OPERATION PEBBLE. SUMMARY REPORT.

    ERIC Educational Resources Information Center

    NORRED, ROBERT B.

    A COMPREHENSIVE EVALUATION OF OPERATION PEBBLE'S 3 YEAR SUMMER PROGRAM FOR ECONOMICALLY AND EDUCATIONALLY DEPRIVED CHILDREN OF THE UPPER CUMBERLAND REGION OF TENNESSEE IS PRESENTED. THE INTENT OF THE PROJECT WAS TO INVOLVE THE CHILDREN IN EXPERIENCES THAT MIGHT EXPAND THE HORIZONS OF THEIR STAGNANT, HIGHLY STRUCTURED CULTURAL ENVIRONMENT, WITHOUT…

  15. Integrated Low Emissions Cleanup system for direct coal fueled turbines, (moving bed, fluid bed contactor/ceramic filter). Twenty-fourth quarterly status report, July--September 1993

    SciTech Connect

    Newby, R.A.; Alvin, M.A.; Bachovchin, D.M.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1993-12-31

    The United States Department of Energy, Morgantown Energy Research Center (DOE/METC), is sponsoring the development of direct coal-fired turbine power plants as part of their Heat Engines program. A major technical challenge remaining for the development of the direct coal-fired turbine is high-temperature combustion gas cleaning to meet environmental standards for sulfur oxides and particulate emissions, as well as to provide acceptable turbine life. The Westinghouse Electric Corporation, Science & Technology Center, is evaluating two Integrated Low Emissions Cleanup (ILEC) concepts that have been configured to meet this technical challenge: a baseline ceramic barrier filter ILEC concept, and a fluidized bed ILEC concept. These ILEC concepts simultaneously control sulfur, particulate, and alkali contaminants in the high-pressure combustion gases at turbine inlet temperatures up to 2300{degree}F. This document reports the status of a program in the nineteenth quarter to develop this ILEC technology for direct coal-fired turbine power plants.

  16. Integrated low emissions cleanup system for direct coal fueled turbines (moving bed, fluid bed contactor/ceramic filter). Twentieth quarterly status report, July--September 1992

    SciTech Connect

    Newby, R.A.; Alvin, M.A.; Bachovchin, D.M.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1992-10-20

    The United States Department of Energy, Morgantown Energy Research Center (DOE/METC), is sponsoring the development of direct coal-fired turbine power plants as part of their Heat Engines program. A major technical challenge remaining for the development of the direct coal-fired turbine is high-temperature combustion gas cleaning to meet environmental standards for sulfur oxides and particulate emissions, as well as to provide acceptable turbine life. The Westinghouse Electric Corporation, Science & Technology Center, is evaluating two Integrated Low Emissions Cleanup (ILEC) concepts that have been configured to meat this technical challenge: a baseline ceramic barrier filter ILEC concept, and a fluidized bed ILEC concept. These ILEC concepts simultaneously control sulfur, particulate, and alkali contaminants in the high-pressure combustion gases at turbine inlet temperatures up to 2300{degree}F. This document reports the status of a program in the nineteenth quarter to develop this ILEC technology for direct coal-fired turbine power plants.

  17. Integrated low emissions cleanup system for direct coal fueled turbines (moving bed, fluid bed contactor/ceramic filter). Twenty-third quarterly status report, April--June 1993

    SciTech Connect

    Newby, R.A.; Alvin, M.A.; Bachovchin, D.M.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1993-07-19

    The United States Department of Energy, Morgantown Energy Research Center (DOE/METC), is sponsoring the development of direct coal-fired turbine power plants as part of their Heat Engines program. A major technical challenge remaining for the development of the direct coal-fired turbine is high-temperature combustion gas cleaning to meet environmental standards for sulfur oxides and particulate emissions, as well as to provide acceptable turbine life. The Westinghouse Electric Corporation, Science & Technology Center, is evaluating two Integrated Low Emissions Cleanup (ILEC) concepts that have been configured to meet this technical challenge: A baseline ceramic barrier filter ILEC concept, and a fluidized bed ILEC concept. These ILEC concepts simultaneously control sulfur, particulate, and alkali contaminants in the high-pressure combustion gases at turbine inlet temperatures up to 2300{degrees}F. This document reports the status of a program in the nineteenth quarter to develop this ILEC technology for direct coal-fired turbine power plants.

  18. Integrated low emissions cleanup system for direct coal fueled turbines (Moving bed, fluid bed contactor/ceramic filter). Seventeenth quarterly status report, October--December 1991

    SciTech Connect

    Newby, R.A.; Alvin, M.A.; Bachovchin, D.M.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1992-01-20

    The United States Department of Energy, Morgantown Energy Research Center (DOE/METC), is sponsoring the development of direct coal-fired turbine power plants as part of their Heat Engines program. A major technical challenge remaining for the development of the direct coal-fired turbine is high-temperature combustion gas cleaning to meet environmental standards for sulfur oxides and particulate emissions, as well as to provide acceptable turbine life. The Westinghouse Electric Corporation, Science & Technology Center, is evaluating two Integrated Low Emissions Cleanup (ILEC) concepts that have been configured to meet this technical challenge: a baseline ceramic barrier filter ILEC concept, and a fluidized bed ILEC concept. These ILEC concepts simultaneously control sulfur, particulate, and alkali contaminants in the high-pressure combustion gases at turbine inlet temperatures up to 2300{degrees}F. This document reports the status of a program in the seventeenth quarter to develop this ILEC technology for direct coal-fired turbine power plants.

  19. Reconstructing the transport history of pebbles on Mars.

    PubMed

    Szabó, Tímea; Domokos, Gábor; Grotzinger, John P; Jerolmack, Douglas J

    2015-01-01

    The discovery of remarkably rounded pebbles by the rover Curiosity, within an exhumed alluvial fan complex in Gale Crater, presents some of the most compelling evidence yet for sustained fluvial activity on Mars. While rounding is known to result from abrasion by inter-particle collisions, geologic interpretations of sediment shape have been qualitative. Here we show how quantitative information on the transport distance of river pebbles can be extracted from their shape alone, using a combination of theory, laboratory experiments and terrestrial field data. We determine that the Martian basalt pebbles have been carried tens of kilometres from their source, by bed-load transport on an alluvial fan. In contrast, angular clasts strewn about the surface of the Curiosity traverse are indicative of later emplacement by rock fragmentation processes. The proposed method for decoding transport history from particle shape provides a new tool for terrestrial and planetary sedimentology. PMID:26460507

  20. Reconstructing the transport history of pebbles on Mars

    PubMed Central

    Szabó, Tímea; Domokos, Gábor; Grotzinger, John P.; Jerolmack, Douglas J.

    2015-01-01

    The discovery of remarkably rounded pebbles by the rover Curiosity, within an exhumed alluvial fan complex in Gale Crater, presents some of the most compelling evidence yet for sustained fluvial activity on Mars. While rounding is known to result from abrasion by inter-particle collisions, geologic interpretations of sediment shape have been qualitative. Here we show how quantitative information on the transport distance of river pebbles can be extracted from their shape alone, using a combination of theory, laboratory experiments and terrestrial field data. We determine that the Martian basalt pebbles have been carried tens of kilometres from their source, by bed-load transport on an alluvial fan. In contrast, angular clasts strewn about the surface of the Curiosity traverse are indicative of later emplacement by rock fragmentation processes. The proposed method for decoding transport history from particle shape provides a new tool for terrestrial and planetary sedimentology. PMID:26460507

  1. Reconstructing the transport history of pebbles on Mars

    NASA Astrophysics Data System (ADS)

    Szabó, Tímea; Domokos, Gábor; Grotzinger, John P.; Jerolmack, Douglas J.

    2015-10-01

    The discovery of remarkably rounded pebbles by the rover Curiosity, within an exhumed alluvial fan complex in Gale Crater, presents some of the most compelling evidence yet for sustained fluvial activity on Mars. While rounding is known to result from abrasion by inter-particle collisions, geologic interpretations of sediment shape have been qualitative. Here we show how quantitative information on the transport distance of river pebbles can be extracted from their shape alone, using a combination of theory, laboratory experiments and terrestrial field data. We determine that the Martian basalt pebbles have been carried tens of kilometres from their source, by bed-load transport on an alluvial fan. In contrast, angular clasts strewn about the surface of the Curiosity traverse are indicative of later emplacement by rock fragmentation processes. The proposed method for decoding transport history from particle shape provides a new tool for terrestrial and planetary sedimentology.

  2. Integrated low emissions cleanup system for direct coal fueled turbines (moving bed, fluid bed contactor/ceramic filter). Eighteenth quarterly status report, January--March 1992

    SciTech Connect

    Newby, R.A.; Alvin, M.A.; Bachovchin, D.M.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1992-04-20

    The United States Department of Energy, Morgantown Energy Research Center (DOE/METC), is sponsoring the development of direct coal-fired turbine power plants as part of their Heat Engines program. A major technical challenge remaining for the development of the direct coal-fired turbine is high-temperature combustion gas cleaning to meet environmental standards for sulfur oxides and particulate emissions, as well as to provide acceptable turbine life. The Westinghouse Electric Corporation, Science & Technology Center, is evaluating two Integrated Low Emissions Cleanup (ILEC) concepts that have been configured to meet this technical challenge: a baseline ceramic barrier filter nEC concept, and a fluidized bed ILEC concept. These ILEC concepts simultaneously control sulfur, particulate, and alkali contaminants in the high-pressure combustion gases at turbine inlet temperatures up to 2300{degrees}F. This document reports the status of a program in the eighteenth quarter to develop this ILEC technology for direct coal-fired turbine power plants.

  3. Integrated Low Emissions Cleanup system for direct coal fueled turbines (moving bed, fluid bed contactor/ceramic filter). Twenty-fifth quarterly report, October--December 1993

    SciTech Connect

    Newby, R.A.; Alvin, M.A.; Bachovchin, D.M.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1993-12-31

    The United States Department of Energy, Morgantown Energy Research Center (DOE/METC), is sponsoring the development of direct coal-fired turbine power plants as part of their Heat Engines program. A major technical challenge remaining for the development of the direct coal-fired turbine is high-temperature combustion gas cleaning to meet environmental standards for sulfur oxides and particulate emissions, as well as to provide acceptable turbine life. The Westinghouse Electric Corporation, Science & Technology Center, is evaluating two Integrated Low Emissions Cleanup (ILEC) concepts that have been reconfigured to meet this technical challenge: a baseline ceramic barrier filter ILEC concept, and a fluidized bed ILEC concept. These ILEC concepts simultaneously control sulfur, particulate, and alkali contaminants in the high-pressure combustion gases at turbine inlet temperatures up to 2300{degree}F. This document reports the status of a program in the twenty-fifth quarter to develop this ILEC technology for direct coal-fired turbine power plants.

  4. Ceramics

    NASA Astrophysics Data System (ADS)

    Yao, Lichun; Yang, Jian; Qiu, Tai

    2014-09-01

    The effects of CuO addition on phase composition, microstructure, sintering behavior, and microwave dielectric properties of 0.80Sm(Mg0.5Ti0.5)O3-0.20 Ca0.8Sr0.2TiO3(8SMT-2CST) ceramics prepared by a conventional solid-state ceramic route have been studied. CuO addition shows no obvious influence on the phase of the 8SMT-2CST ceramics and all the samples exhibit pure perovskite structure. Appropriate CuO addition can effectively promote sintering and grain growth, and consequently improve the dielectric properties of the ceramics. The sintering temperature of the ceramics decreases by 50°C by adding 1.00 wt.%CuO. Superior microwave dielectric properties with a ɛ r of 29.8, Q × f of 85,500 GHz, and τ f of 2.4 ppm/°C are obtained for 1.00 wt.%CuO doped 8SMT-2CST ceramics sintered at 1500°C, which shows dense and uniform microstructure as well as well-developed grain growth.

  5. High temperature gas-cooled reactor (HTGR) graphite pebble fuel: Review of technologies for reprocessing

    SciTech Connect

    Mcwilliams, A. J.

    2015-09-08

    This report reviews literature on reprocessing high temperature gas-cooled reactor graphite fuel components. A basic review of the various fuel components used in the pebble bed type reactors is provided along with a survey of synthesis methods for the fabrication of the fuel components. Several disposal options are considered for the graphite pebble fuel elements including the storage of intact pebbles, volume reduction by separating the graphite from fuel kernels, and complete processing of the pebbles for waste storage. Existing methods for graphite removal are presented and generally consist of mechanical separation techniques such as crushing and grinding chemical techniques through the use of acid digestion and oxidation. Potential methods for reprocessing the graphite pebbles include improvements to existing methods and novel technologies that have not previously been investigated for nuclear graphite waste applications. The best overall method will be dependent on the desired final waste form and needs to factor in the technical efficiency, political concerns, cost, and implementation.

  6. Ceramic breeder research and development: progress and focus

    NASA Astrophysics Data System (ADS)

    van der Laan, J. G.; Kawamura, H.; Roux, N.; Yamaki, D.

    2000-12-01

    The world-wide efforts on ceramic breeder materials in the last two years concerned Li2O, Li4SiO4, Li2TiO3 and Li2ZrO3, with a clear emphasis on the development of Li2TiO3. Pebble-manufacturing processes have been developed up to a 10 kg scale. Characterisation of materials has advanced. A jump-wise progress is observed in the characterisation of pebble-beds, in particular of their thermo-mechanical behaviour. Thermal property data are still limited. A number of breeder materials have been or are being irradiated in material test reactors like HFR and JMTR. The EXOTIC-8 series of in-pile experiments is a major source of tritium release data. This paper discusses the technical advancements and proposes a focus for further research and development (R&D) : pebble-bed mechanical and thermal behaviour and its interactions with the blanket structure as a function of temperature, burn-up, irradiation dose and time; tritium release and retention properties; determination of the key factors limiting blanket life.

  7. TEM study of impurity segregations in beryllium pebbles

    NASA Astrophysics Data System (ADS)

    Klimenkov, M.; Chakin, V.; Moeslang, A.; Rolli, R.

    2014-12-01

    Beryllium is planned to be used as a neutron multiplier in the Helium-cooled Pebble Bed European concept of a breeding blanket of demonstration power reactor DEMO. In order to evaluate the irradiation performance, individual pebbles and constrained pebble beds were neutron-irradiated at temperatures typical of fusion blankets. Beryllium pebbles 1 mm in diameter produced by the rotating electrode method were subjected to a TEM study before and after irradiation at High Flux Reactor, Petten, Netherlands at 861 K. The grain size varied in a wide range from sub-micron size up to several tens of micrometers, which indicated formation bimodal grain size distribution. Based on the application of combined electron energy loss spectroscopy and energy dispersive X-ray spectroscopy methods, we suggest that impurity precipitates play an important role in controlling the mechanical properties of beryllium. The impurity elements were present in beryllium at a sub-percent concentration form beryllide particles of a complex (Fe/Al/Mn/Cr)B composition. These particles are often ordered along dislocations lines, forming several micron-long chains. It can be suggested that fracture surfaces often extended along these chains in irradiated material.

  8. Ceramics

    NASA Astrophysics Data System (ADS)

    Chen, Song; Zhu, De-Gui; Cai, Xu-Sheng

    2014-08-01

    The dense monoclinic-SrAl2Si2O8 ceramics have been prepared by a two-step sintering process at a sintering temperature of 1173 K (900 °C). Firstly, the pre-sintered monoclinic-SrAl2Si2O8 powders containing small SiO2·Al2O3 crystal phases were obtained by continuously sintering a powder mixture of SrCO3 and kaolin at 1223 K (950 °C) for 6 hours and 1673 K (1400 °C) for 4 hours, respectively. Subsequently, by the combination of the pre-sintered ceramic powders with the composite flux agents, which are composed of a SrO·3B2O3 flux agent and α-Al2O3, the low-temperature densification sintering of the monoclinic-SrAl2Si2O8 ceramics was accomplished at 1173 K (900 °C). The low-temperature sintering behavior and microstructure evolvement of the monoclinic-SrAl2Si2O8 ceramics have been investigated in terms of Al2O3 in addition to the composite flux agents. It shows that due to the low-meting characteristics, the SrO·3B2O3 flux agent can urge the dense microstructure formation of the monoclinic-SrAl2Si2O8 ceramics and the re-crystallization of the grains via a liquid-phase sintering. The introduction of α-Al2O3 to the SrO·3B2O3 flux agent can apparently lead to more dense microstructures for the monoclinic-SrAl2Si2O8 ceramics but also cause the re-precipitation of SiO2·Al2O3 compounds because of an excessive Al2O3 content in the SrO·3B2O3 flux agent.

  9. Pebble Fuel Handling and Reactivity Control for Salt-Cooled High Temperature Reactors

    SciTech Connect

    Peterson, Per; Greenspan, Ehud

    2015-02-09

    This report documents the work completed on the X-PREX facility under NEUP Project 11- 3172. This project seeks to demonstrate the viability of pebble fuel handling and reactivity control for fluoride salt-cooled high-temperature reactors (FHRs). The research results also improve the understanding of pebble motion in helium-cooled reactors, as well as the general, fundamental understanding of low-velocity granular flows. Successful use of pebble fuels in with salt coolants would bring major benefits for high-temperature reactor technology. Pebble fuels enable on-line refueling and operation with low excess reactivity, and thus simpler reactivity control and improved fuel utilization. If fixed fuel designs are used, the power density of salt- cooled reactors is limited to 10 MW/m3 to obtain adequate duration between refueling, but pebble fuels allow power densities in the range of 20 to 30 MW/m3. This can be compared to the typical modular helium reactor power density of 5 MW/m3. Pebble fuels also permit radial zoning in annular cores and use of thorium or graphite pebble blankets to reduce neutron fluences to outer radial reflectors and increase total power production. Combined with high power conversion efficiency, compact low-pressure primary and containment systems, and unique safety characteristics including very large thermal margins (>500°C) to fuel damage during transients and accidents, salt-cooled pebble fuel cores offer the potential to meet the major goals of the Advanced Reactor Concepts Development program to provide electricity at lower cost than light water reactors with improved safety and system performance.This report presents the facility description, experimental results, and supporting simulation methods of the new X-Ray Pebble Recirculation Experiment (X-PREX), which is now operational and being used to collect data on the behavior of slow dense granular flows relevant to pebble bed reactor core designs. The X

  10. Ceramics

    NASA Astrophysics Data System (ADS)

    Bin, Tang; Feng, Si; Ying-xiang, Li; He-tuo, Chen; Xiao, Zhang; Shu-ren, Zhang

    2014-11-01

    The effects of Ta2O5/Y2O3 codoping on the microstructure and microwave dielectric properties of Ba(Co0.56Zn0.40)1/3Nb2/3O3- xA- xB (A = 0.045 wt.% Ta2O5; B = 0.113 wt.% Y2O3) ceramics ( x = 0, 1, 2, 4, 8, 16, 32) prepared according to the conventional solid-state reaction technique were investigated. The x-ray diffraction (XRD) results showed that the main crystal phase in the sintered ceramics was BaZn0.33Nb0.67O3-Ba3CoNb2O9. The additional surface phase of Ba8CoNb6O24 and trace amounts of Ba5Nb4O15 second phase were present when Ta2O5/Y2O3 was added to the ceramics. The 1:2 B-site cation ordering was affected by the substitution of Ta5+ and Y3+ in the crystal lattice, especially for x = 4. Scanning electron microscopy (SEM) images of the optimally doped ceramics sintered at 1340°C for 20 h showed a compact microstructure with crystal grains in dense contact. Though the dielectric constant increased with the x value, appropriate addition would result in a tremendous modification of the Q × f and τ f values. Excellent microwave dielectric properties ( ɛ r = 35.4, Q × f = 62,993 GHz, and τ f = 2.6 ppm/°C) were obtained for the ceramic with x = 0.4 sintered in air at 1340°C for 20 h.

  11. Characteristics of pebble packing and evaluation of sweep gas pressure drop into the in-pile mock-up on fusion blanket

    NASA Astrophysics Data System (ADS)

    Ishitsuka, Etsuo; Nakamichi, Masaru; Kawamura, Hiroshi; Sagawa, Hisashi; Kanzawa, Toru; Suzuki, Tatsushi; Saito, Minoru

    1994-09-01

    The characteristics of pebble packing and the sweep gas pressure drop have been investigated for the design of the in-pile mock-up in Japan Materials Testing Reactor, and the results obtained are the following. The packing fraction of single diameter pebbles is kept at constant, i.e., about 63%, under the condition that the ratio of tube inside diameter to pebble diameter is above 10. The pebble distribution in the bed is not homogeneous, i.e., the mixture of close packing and loose packing zones both in the middle of bed and near wall. The packing fraction is about 77% for two-size pebble packing consisting of Ø1 and 5 mm pebbles. The measured pressure drops agree with those predicted by the Kozeny-Carman equation within the range of (+25)-(-60)%. The pressure drop is not affected by moisture concentration (< 100 ppm) and does not change for tests lasting as long as 300 hours.

  12. Ceramics

    NASA Astrophysics Data System (ADS)

    Li, Enzhu; Zou, Mengying; Duan, Shuxin; Xu, Ning; Yuan, Ying; Zhou, Xiaohua

    2014-11-01

    The effects of excess Li content on the phase structure and microwave dielectric properties, especially on the temperature coefficient, of LiNb0.6 Ti0.5O3 (LNT) ceramics were studied. The results show that small amounts of Li effectively enhanced the sintering process due to the compensation of high volatility of Li, leading to a densification and homogenous microstructure, and therefore enhanced the dielectric properties. However, too much Li leads to a secondary phase and cause abnormal grain growth. The LNT + 5 wt.% Li ceramic sintered at 1075°C in the air shows the best properties of ɛ r = 69.73, Q × f = 5543 GHz, and τ f = -4.4 ppm/°C.

  13. Formation of pebble-pile planetesimals

    NASA Astrophysics Data System (ADS)

    Wahlberg Jansson, Karl; Johansen, Anders

    2014-10-01

    Asteroids and Kuiper belt objects are remnant planetesimals from the epoch of planet formation. The first stage of planet formation is the accumulation of dust and ice grains into mm- and cm-sized pebbles. These pebbles can clump together through the streaming instability and form gravitationally bound pebble clouds. Pebbles inside such a cloud will undergo mutual collisions, dissipating energy into heat. As the cloud loses energy, it gradually contracts towards solid density. We model this process and investigate two important properties of the collapse: (i) the collapse timescale and (ii) the temporal evolution of the pebble size distribution. Our numerical model of the pebble cloud is zero-dimensional and treats collisions with a statistical method. We find that planetesimals with radii larger than ~100 km collapse on the free-fall timescale of ~25 years. Lower-mass clouds have longer pebble collision timescales and collapse much more slowly, with collapse times of a few hundred years for 10 km scale planetesimals and a few thousand years for 1 km scale planetesimals. The mass of the pebble cloud also determines the interior structure of the resulting planetesimal. The pebble collision speeds in low-mass clouds are below the threshold for fragmentation, forming pebble-pile planetesimals consisting of the primordial pebbles from the protoplanetary disk. Planetesimals above 100 km in radius, on the other hand, consist of mixtures of dust (pebble fragments) and pebbles which have undergone substantial collisions with dust and other pebbles. The Rosetta mission to the comet 67P/Churyumov-Gerasimenko and the New Horizons mission to Pluto will provide valuable information about the structure of planetesimals in the solar system. Our model predicts that 67P is a pebble-pile planetesimal consisting of primordial pebbles from the solar nebula, while the pebbles in the cloud which contracted to form Pluto must have been ground down substantially during the collapse.

  14. Postirradiation examination of beryllium pebbles

    SciTech Connect

    Gelles, D.S.

    1998-03-01

    Postirradiation examinations of COBRA-1A beryllium pebbles irradiated in the EBR-II fast reactor at neutron fluences which generated 2700--3700 appm helium have been performed. Measurements included density change, optical microscopy, scanning electron microscopy, and transmission electron microscopy. The major change in microstructure is development of unusually shaped helium bubbles forming as highly non-equiaxed thin platelet-like cavities on the basal plane. Measurement of the swelling due to cavity formation was in good agreement with density change measurements.

  15. Integrated Low Emissions Cleanup system for direct coal fueled turbines (moving bed, fluid contactor/ceramic filter). Twenty-second quarterly status report, January--March 1993

    SciTech Connect

    Newby, R.A.; Alvin, M.A.; Bachovchin, D.M.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1993-10-01

    The United States Department of Energy, Morgantown Energy Research Center (DOE/METC), is sponsoring the development of direct coal-fired turbine power plants as part of their Heat Engines program. A major technical challenge remaining for the development of the direct coal-fired turbine is high-temperature combustion gas cleaning to meet environmental standards for sulfur oxides and particulate emissions, as well as to provide acceptable turbine life. The Westinghouse Electric Corporation, Science & Technology Center, is evaluating two Integrated Low Emissions Cleanup (ILEC) concepts that have been configured to meet this technical challenge: A baseline ceramic barrier filter ILEC concept, and a fluidized bed ILEC concept. These ILEC concepts simultaneously control sulfur, particulate, and alkali contaminants in the high-pressure combustion gases at turbine inlet temperatures up to 2300{degrees}F. This document reports the status of a program in the nineteenth quarter to develop this ILEC technology for direct coal-fired turbine power plants.

  16. Integrated low emissions cleanup system for direct coal fueled turbines (moving bed, fluid bed contactor/ceramic filter). Twenty-ninth quarterly status report, October--December 1994

    SciTech Connect

    Newby, R.A.; Alvin, M.A.; Bachovchin, D.M.

    1996-02-01

    The United States Department of Energy, Morgantown Energy Research Center (DOE/METC), is sponsoring the development of advanced, coal-fueled turbine power plants such as pressurized fluid bed combustion and coal gasification combined cycles. A major technical challenge remaining for the development of the coal-fueled turbine is high-temperature gas cleaning to meet environmental standards for sulfur oxides and particulate emissions, as well as to provide acceptable turbine life. The Westinghouse Electric Corporation, Science & Technology Center, is evaluating Integrated Low Emissions Cleanup (ILEC) concepts that have been configured to meet this technical challenge. These ILEC concepts simultaneously control sulfur, particulate, and alkali contaminants in the high-pressure process gases. This document reports the status of a program in the twenty-seventh quarter to develop this ILEC technology.

  17. Integrated low emissions cleanup system for direct coal fueled turbines (moving bed, fluid bed contactor/ceramic filter). Twenty-seventh quarterly status report, April--June 1994

    SciTech Connect

    Newby, R.A.; Alvin, M.A.; Bachovchin, D.M.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1994-10-01

    The United States Department of Energy, Morgantown Energy Research Center (DOE/METC), is sponsoring the development of advanced, coal-fueled turbine power plants such as pressurized fluid bed combustion and coal gasification combined cycles. A major technical challenge remaining for the development of the coal-fueled turbine is high-temperature gas cleaning to meet environmental standards for sulfur oxides and particulate emissions, as well as to provide acceptable turbine life. The Westinghouse Electric Corporation, Science & Technology Center, is evaluating Integrated Low Emissions Cleanup (ILEC) concepts that have been configured to meet this technical challenge. These ILEC concepts simultaneously control sulfur, particulate, and alkali contaminants in the high-pressure process gases. This document reports the status of a program in the twenty-seventh quarter to develop this ILEC technology.

  18. Stability and convergence analysis of the quasi-dynamics method for the initial pebble packing

    SciTech Connect

    Li, Y.; Ji, W.

    2012-07-01

    The simulation for the pebble flow recirculation within Pebble Bed Reactors (PBRs) requires an efficient algorithm to generate an initial overlap-free pebble configuration within the reactor core. In the previous work, a dynamics-based approach, the Quasi-Dynamics Method (QDM), has been proposed to generate densely distributed pebbles in PBRs with cylindrical and annular core geometries. However, the stability and the efficiency of the QDM were not fully addressed. In this work, the algorithm is reformulated with two control parameters and the impact of these parameters on the algorithm performance is investigated. Firstly, the theoretical analysis for a 1-D packing system is conducted and the range of the parameter in which the algorithm is convergent is estimated. Then, this estimation is verified numerically for a 3-D packing system. Finally, the algorithm is applied to modeling the PBR fuel loading configuration and the convergence performance at different packing fractions is presented. Results show that the QDM is efficient in packing pebbles within the realistic range of the packing fraction in PBRs, and it is capable in handling cylindrical geometry with packing fractions up to 63.5%. (authors)

  19. Formation of planetesimals in collapsing pebble clouds

    NASA Astrophysics Data System (ADS)

    Wahlberg Jansson, K.; Johansen, A.

    2014-07-01

    Asteroids and Kuiper belt objects are remnant planetesimals from the epoch of planet formation. Their physical properties hold important clues to understanding how minor bodies formed in the Solar Nebula. The first stage of the planet formation process is the accumulation of dust and ice grains into mm-cm-sized pebbles. Due to the interaction with the gas in the protoplanetary disk, these pebbles can clump together through the streaming instability and form gravitationally bound particle pebble 'clouds'. Pebbles in the cloud collide with each other, dissipating energy into heat. As the cloud loses energy, it contracts, and one would expect the particles to move faster and faster due to the negative heat capacity nature of self-gravitating systems. However, for high-mass clouds, the collapse is limited by free-fall and the cloud does not have time to virialize. This in turn leads to lower collision speeds but thanks to increased density also to increased collision rates and a runaway collapse. We investigate three important properties of the collapse: (i) the time-scale to collapse to solid density, (ii) the temporal evolution of the size spectrum of the pebbles, and (iii) the multiplicity of the resulting planetesimals. We find that planetesimals larger than 100 km in radius collapse on the free-fall time-scale of about 25 years. Lower-mass clouds have longer pebble collision time-scales and hence collapse much more slowly, with collapse times of a few hundred years for 10-km-scale planetesimals and a few thousand years for 1-km-scale planetesimals. The mass of the pebble cloud also determines the structure of the resulting planetesimal. The collision speed among the pebbles in low- mass clouds is below the threshold for fragmentation, forming pebble- pile planetesimals consisting of the primordial pebbles from the nebula. Planetesimals above 100 km in radius, on the other hand, consist of mixtures of dust (pebble fragments) and pebbles which have undergone

  20. Planetary growth by the accretion of pebbles

    NASA Astrophysics Data System (ADS)

    Lambrechts, Michiel; Johansen, Anders; Bitsch, Bertram; Morbidelli, Alessandro

    2015-11-01

    Pebbles, approximately cm-sized solids that drift through a protoplanetary disc, provide a reservoir of material that can be efficiently accreted by planetary embryos due to the dissipating effect of gas drag (Lambrechts & Johansen, 2012).Here, we will highlight the robust implications of pebble accretion on the formation of planets throughout the protoplanetary disc.In the outer disc, icy pebbles form by coagulation and consequently start drifting inwards. Nevertheless, we find that the pebble surface densities are sufficiently high to form giant planets on wide orbits, before the gas disc disperses after a few Myr (Lambrechts & Johansen, 2014). Growth is only halted when cores reach sizes of around 10 Earth masses, when their gravity creates pressure bumps trapping the inwards drifting pebbles.This accretion cutoff triggers the attraction of a massive gaseous envelope. Additionally, the fast growth of giant planets prevents the loss of the cores by type-I migration (Lambrechts et al 2014, Bitsch et al 2015).Closer to the star, interior to the ice line, pebble accretion takes on a different form. There, chondrule-sized particles lead to the formation of much smaller, Mars-sized embryos, before the pebble flux is terminated by the growth of the gas giants (Morbidelli et al, 2015). We will also discuss ongoing work on the conditions under which much larger Super-Earths can form.

  1. Integrated low emissions cleanup system for direct coal fueled turbines: (moving bed, fluid bed contactor/ceramic filter). Thirtieth quarterly report for the period January--March 1995

    SciTech Connect

    Newby, R.A.; Alvin, M.A.; Bachovchin, D.M.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1995-10-01

    The United States Department of Energy, Morgantown Energy Research Center (DOE/METC), is sponsoring the development of advanced, coal-fueled turbine power plants such as pressurized fluid bed combustion and coal gasification combined cycles. A major technical challenge remaining for the development of the coal-fueled turbine is high-temperature gas cleaning to meet environmental standards for sulfur oxides and particulate emissions, as well as to provide acceptable turbine life. The Westinghouse Electric Corporation, Science & Technology Center, is evaluating Integrated Low Emissions Cleanup (ILEC) concepts that have been configured to meet this technical challenge. These UEC concepts simultaneously control sulfur, particulate, and alkali contaminants in the high-pressure process gases. This document reports the status of a program in the thirtieth quarter to develop this ILEC technology. During this Quarter of the program, the Phase In bench-scale, high-temperature, high-pressure (HTHP) testing of PFBC fly ashes was continued. Tests have been completed to characterize the filter cake pulse cleaning, as a function of temperature. The behavior trends are consistent with field unit observations. Sulfur removal tests, looking at the influence of SO{sub 2} on filter cake permeability, as well as the ability to remove sulfur by injecting dolomite into the filter, have been completed. Alkali removal tests were initiated this quarter injecting emathlite into the filter. A complete summary of the test procedures; tests completed and test results is presented in Appendices A, B and C. Preparation has been made to prepare the Phase III final report.

  2. Fabrication of Li2TiO3 pebbles with small grain size via hydrothermal and improved dry-rolling methods

    NASA Astrophysics Data System (ADS)

    Zhang, Wen; Zhou, Qilai; Xue, Lihong; Yan, Youwei

    2015-09-01

    Lithium titanate (Li2TiO3) ceramic pebbles were successfully fabricated by using hydrothermal and improved dry-rolling method. In the present work, ultra-fine Li2TiO3 powder of high reactivity was prepared via hydrothermal reaction, using anatase titania and lithium hydroxide as raw materials. The as-synthesized Li2TiO3 powder exhibits an average crystalline size as small as 100 nm. Improved dry-rolling method was employed to fabricate Li2TiO3 pebbles. The green pebbles can be well-sintered (81% T.D.) at a temperature as low as 850 °C for 3 h. The pebbles have good sphericity (1.08) and narrow diameter distribution (1.0-1.2 mm) with a crush load of 35 N. Scanning electron microscope (SEM) observations of pebbles showed that the ceramic grain size was below 1 μm and atomic emission spectrometer fitted with inductively coupled plasma (ICP-AES) results confirmed that atomic ratio of Li to Ti in the fabricated pebbles was 1.97.

  3. Mechanisms of flow through compressible porous beds in sedimentation, filtration, centrifugation, deliquoring, and ceramic processing. [Annual report], February 1, 1991--January 31, 1992

    SciTech Connect

    Tiller, F.M.

    1992-06-01

    The University of Houston research program is aimed at the specific area of solid/liquid separation including sedimentation, thickening, cake filtration, centrifugation, expression, washing, deep-bed filtration, screening, and membrane separation. Unification of the theoretical approaches to the various solid/liquid separation operations is the principle objective of the research. Exploring new aspects of basic separation mechanisms, verification of theory with experiment, development of laboratory procedures for obtaining data for design, optimizing operational methods, and transferring the results to industry are a part of the Houston program. New methodology developed in our program now permits an engineer or scientist to handle thickening, cake filtration, centrigual filtration, and expression in a unified manner. The same fundamental equations are simply adapted to the differing parameters and conditions related to the various modes of separation. As the system is flexible and adaptable to computational software, new developments can continually be added. Discussions of the various research projects in this report have been kept to a minimum and are principally qualitative. The length of the report would be excessive if each topic were covered in depth. Although the number of research topics may appear larger than one would expect, many are closely interconnected and reflect our philosophy of working in apparently diverse fields such as ceramics, mining, wastewater, food, chemical processing, and oil well operations.

  4. Ceramic fiber ceramic matrix filter development

    SciTech Connect

    Judkins, R.R.; Stinton, D.P.; Smith, R.G.; Fischer, E.M.

    1994-09-01

    The objectives of this project were to develop a novel type of candle filter based on a ceramic fiber-ceramic matrix composite material, and to extend the development to full-size, 60-mm OD by 1-meter-long candle filters. The goal is to develop a ceramic filter suitable for use in a variety of fossil energy system environments such as integrated coal gasification combined cycles (IGCC), pressurized fluidized-bed combustion (PFBC), and other advanced coal combustion environments. Further, the ceramic fiber ceramic matrix composite filter, hereinafter referred to as the ceramic composite filter, was to be inherently crack resistant, a property not found in conventional monolithic ceramic candle filters, such as those fabricated from clay-bonded silicon carbide. Finally, the adequacy of the filters in the fossil energy system environments is to be proven through simulated and in-plant tests.

  5. Pebble bed reactor fiscal year 1980: review summary report

    SciTech Connect

    Not Available

    1980-07-01

    Information on high-temperature reactor development is presented concerning reactor operating experience; core performance assessment; core control and shutdown; reflector and core support; maintenance and availability; safety aspects of PBR and prismatic comparison; PCRV dimensions; and fuel reprocessing cost estimate.

  6. Forming the Solar System from Pebbles

    NASA Astrophysics Data System (ADS)

    Kretke, Katherine A.; Levison, H. F.

    2015-12-01

    In recent years, theories surrounding the formation of small-bodies and planets have been undergoing a radical shift. Particles with stopping times comparable to their orbital times, often called "pebbles" (although they range from sub-centimeter to meter sizes), interact with gaseous protoplanetary disks in very special ways. This allows them to be not only be concentrated, allowing them to gravitationally collapse and directly produce the planetesimal building blocks of planetary systems, but also later be efficiently accreted on to these planetesimals, rapidly producing larger planets. Here we present simulations using the planet formation code LIPAD, which can follow the dynamical evolution of planetary system all the way from pebbles and planetesimals to mature planetary systems. We show how pebble accretion can explain the observed structure of our Solar System, by forming a system of giant planets, ice giants, and a system of terrestrial planets; even providing an explanation the for the low mass of Mars and of the Asteroid Belt.

  7. Pebble Jammed in Rock Abrasion Tool

    NASA Technical Reports Server (NTRS)

    2004-01-01

    After the rock abrasion tool on NASA's Mars Exploration Rover Opportunity stopped working on sol 199 (Aug. 15, 2004), rover operators used the panoramic camera to take this image the next day for help in diagnosing the problem. The tool was closer than the camera could focus on sharply, but the image does show a dark spot just left of center, which engineers have determined is likely to be a pebble jammed between the cutting-blade rotor and the wire-brush rotor. If that diagnosis is confirmed by further analysis, the tool will likely be commanded to turn the rotors in reverse to release the pebble.

  8. Pebble Accretion and the Diversity of Planetary Systems

    NASA Astrophysics Data System (ADS)

    Chambers, J. E.

    2016-07-01

    This paper examines the standard model of planet formation, including pebble accretion, using numerical simulations. Planetary embryos that are large enough to become giant planets do not form beyond the ice line within a typical disk lifetime unless icy pebbles stick at higher speeds than in experiments using rocky pebbles. Systems like the solar system (small inner planets and giant outer planets) can form if icy pebbles are stickier than rocky pebbles, and if the planetesimal formation efficiency increases with pebble size, which prevents the formation of massive terrestrial planets. Growth beyond the ice line is dominated by pebble accretion. Most growth occurs early, when the surface density of the pebbles is high due to inward drift of the pebbles from the outer disk. Growth is much slower after the outer disk is depleted. The outcome is sensitive to the disk radius and turbulence level, which control the lifetime and maximum size of pebbles. The outcome is sensitive to the size of the largest planetesimals because there is a threshold mass for the onset of pebble accretion. The planetesimal formation rate is unimportant, provided that some large planetesimals form while the pebbles remain abundant. Two outcomes are seen, depending on whether pebble accretion begins while the pebbles are still abundant. Either multiple gas-giant planets form beyond the ice line, small planets form close to the star, and a Kuiper-belt-like disk of bodies is scattered outward by the giant planets; or no giants form and the bodies remain an Earth-mass or smaller.

  9. Pebbles and Cobbles at MPF Site

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Pebbles are seen in lander images, along with cobbles. For example, in this picture, we see the same pebbles that were visible in the Sojourner rover image of the 'Cabbage Patch' (PIA00984). In addition, a cobble within the rock 'Lamb' (upper left) is apparent. This indicates that Lamb may be a conglomerate (Lamb is 0.32 m x 0.15 m).

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

  10. Pebble fuel design for the PB-FHR

    SciTech Connect

    Cisneros, A. T.; Scarlat, R. O.; Laufer, M. R.; Greenspan, E.; Peterson, P. F.

    2012-07-01

    This paper presents the results of parametric studies of pebble fuel that can guide the design of future PB-FHR cores. The pebble fuel designs are assessed using the following performance characteristics: burnup, reactivity feedback, transient response, timescale to reach equilibrium cycle, and protection of structural components. The performance of a thorium pebble blanket is assessed by comparing against a seed-only system and system that utilizes a graphite pebble reflector instead of a thorium blanket. This paper presents the functional requirements and a methodology to assess these fuel pebble designs. This paper identifies a feasible design space for low enriched uranium pebbles and selected a baseline pebble design for safe, economic energy generation. Furthermore, this study finds a thorium blanket does not increase the performance of the system significantly with respect to a graphite pebble reflector. Therefore, a graphite pebble reflector is recommended in the baseline full-core design to extend the lifetime of the outer solid graphite reflector to the life of plant. (authors)

  11. Tritium analyses of COBRA-1A2 beryllium pebbles

    SciTech Connect

    Baldwin, D.L.

    1998-03-01

    Selected tritium measurements have been completed for the COBRA-1A2 experiment C03 and D03 beryllium pebbles. The completed results, shown in Tables 1, 2, and 3, include the tritium assay results for the 1-mm and 3-mm C03 pebbles, and the 1-mm D03 pebbles, stepped anneal test results for both types of 1-mm pebbles, and the residual analyses for the stepped-anneal specimens. All results have been reported with date-of-count and are not corrected for decay. Stepped-anneal tritium release response is provided in addenda.

  12. Deleterious Thermal Effects due to Randomized Flow Paths in Pebble Bed, and Particle Bed Style Reactors

    NASA Technical Reports Server (NTRS)

    Moran, Robert P.

    2013-01-01

    Reactor fuel rod surface area that is perpendicular to coolant flow direction (+S) i.e. perpendicular to the P creates areas of coolant stagnation leading to increased coolant temperatures resulting in localized changes in fluid properties. Changes in coolant fluid properties caused by minor increases in temperature lead to localized reductions in coolant mass flow rates leading to localized thermal instabilities. Reductions in coolant mass flow rates result in further increases in local temperatures exacerbating changes to coolant fluid properties leading to localized thermal runaway. Unchecked localized thermal runaway leads to localized fuel melting. Reactor designs with randomized flow paths are vulnerable to localized thermal instabilities, localized thermal runaway, and localized fuel melting.

  13. Particle fuel bed tests

    SciTech Connect

    Horn, F.L.; Powell, J.R.; Savino, J.M.

    1985-01-01

    Gas-cooled reactors, using packed beds of small diameter coated fuel particles have been proposed for compact, high-power systems. The particulate fuel used in the tests was 800 microns in diameter, consisting of a thoria kernel coated with 200 microns of pyrocarbon. Typically, the bed of fuel particles was contained in a ceramic cylinder with porous metallic frits at each end. A dc voltage was applied to the metallic frits and the resulting electric current heated the bed. Heat was removed by passing coolant (helium or hydrogen) through the bed. Candidate frit materials, rhenium, nickel, zirconium carbide, and zirconium oxide were unaffected, while tungsten and tungsten-rhenium lost weight and strength. Zirconium-carbide particles were tested at 2000 K in H/sub 2/ for 12 hours with no visible reaction or weight loss.

  14. Mechanics, kinematics and geometry of pebble abrasion from binary collisions

    NASA Astrophysics Data System (ADS)

    Miller, K. L.; Jerolmack, D. J.

    2014-12-01

    As sediment is transported downstream as bedload, it collides with the bed causing sharp edges to chip and wear away, rounding the rock through the process of abrasion. Previous work has linked abrasion to downstream fining and rounding of grains, however, there has been little attempt to understand the underlying kinematics of abrasion. Furthermore, most studies neglect the fine particle produced during the abrasion process, as the initial grain gets smaller and rounder. In this research, we preform well-controlled laboratory experiments to determine the functional dependence between impact energy and mass lost from abrasion. We use a double-pendulum "Newton's Cradle" set-up to examine the abrasion between two grains and with a high-speed camera, we can quantify the impact energies during collision. Results from experiments verify that mass loss is proportional to kinetic energy. We define a material parameter that incorporates material density, Young's modulus, and tensile stress and show that this parameter is directly related to the proportionality between mass loss and energy. We identify an initial region of the mass loss curves in which abrasion is independent of energy and material properties; results suggest this region is determined by shape. We show that grain size distributions of daughter products are universal and independent of material; they follow a Weibull distribution, which is expected distribution from brittle fracture theory. Finally, scanning electron microscope (SEM) images show a thin damage zone near the surface, suggesting that collision energy is attenuated over some small skin depth. Overall, we find that pebble abrasion by collision can be characterized by two universal scaling relations - the mass loss versus energy curves and the size distribution of daughter products. Results will be useful for estimating expected abrasion rates in the field, and additionally demonstrate that low-energy collisions produce large quantities of sand

  15. Mechanisms of flow through compressible porous beds in sedimentation, filtration, centrifugation, deliquoring, and ceramic processing. Progress report, January 1993--November 1993

    SciTech Connect

    Tiller, F.M.

    1993-11-01

    The research program is involved with the area of solid/liquid separation including sedimentation, thickening, cake filtration, centrifugation, expression, washing, deep-bed filtration, screening, and membrane separation. Objective is the unification of theoretical approaches to solid/liquid separations. The research is divided according to: Centrifugation, cake filtration, sedimentation/thickening, and optimization studies (tubular arrangements in candle filters; maximizing filtration rates with filter aids).

  16. Ceramic fiber filter technology

    SciTech Connect

    Holmes, B.L.; Janney, M.A.

    1996-06-01

    Fibrous filters have been used for centuries to protect individuals from dust, disease, smoke, and other gases or particulates. In the 1970s and 1980s ceramic filters were developed for filtration of hot exhaust gases from diesel engines. Tubular, or candle, filters have been made to remove particles from gases in pressurized fluidized-bed combustion and gasification-combined-cycle power plants. Very efficient filtration is necessary in power plants to protect the turbine blades. The limited lifespan of ceramic candle filters has been a major obstacle in their development. The present work is focused on forming fibrous ceramic filters using a papermaking technique. These filters are highly porous and therefore very lightweight. The papermaking process consists of filtering a slurry of ceramic fibers through a steel screen to form paper. Papermaking and the selection of materials will be discussed, as well as preliminary results describing the geometry of papers and relative strengths.

  17. The cause of advective slowdown of tracer pebbles in rivers: Implementation of Exner-Based Master Equation for coevolving streamwise and vertical dispersion

    NASA Astrophysics Data System (ADS)

    Pelosi, A.; Schumer, R.; Parker, G.; Ferguson, R. I.

    2016-03-01

    Tracer pebbles are often used to study bed load transport processes in gravel bed rivers. Models have been proposed for their downstream dispersion, and also for vertical dispersion, but not for the combined effects of downstream and vertical movement. Here we use the Exner-Based Master Equation to characterize the transient coevolution of streamwise and vertical advection-diffusion of tracer pebbles under equilibrium transport conditions (no net aggradation or degradation). The coevolution of streamwise and vertical dispersion gives rise to behavior that can differ markedly from that associated with purely streamwise processes with no vertical exchange. One example is streamwise advective slowdown. Particles that are advected downward into zones where the probability of reentrainment becomes asymptotically small are essentially trapped and can no longer participate in streamwise advection. As a result, the mean streamwise velocity of the tracer plume declines in time. Qualitative and quantitative comparisons with two field experiments show encouraging agreement despite the simplified boundary conditions in the model.

  18. Portfolio: Ceramics.

    ERIC Educational Resources Information Center

    Hardy, Jane; And Others

    1982-01-01

    Describes eight art activities using ceramics. Elementary students created ceramic tiles to depict ancient Egyptian and medieval European art, made ceramic cookie stamps, traced bisque plates on sketch paper, constructed clay room-tableaus, and designed clay relief masks. Secondary students pit-fired ceramic pots and designed ceramic Victorian…

  19. Feasibility studies on the burnup measurement of fuel pebbles with HPGe gamma spectrometer

    NASA Astrophysics Data System (ADS)

    Yan, Wei-Hua; Zhang, Li-Guo; Zhang, Zhao; Xiao, Zhi-Gang

    2013-06-01

    The feasibility of utilizing a High Purity Germanium (HPGe) detector for the fuel element burnup measurement in a future Modular Pebble Bed Reactor (MPBR) was studied. First, the HPGe spectrometer was set-up for running the detector at high count rates while keeping the energy resolution adequately high to discriminate the Cs-137 peak from other interfering peaks. Based on these settings, the geometrical conditions are settled. Next, experiments were performed with Co-60 and Cs-137 sources to mimic the counting rates in real applications. With the aid of KORIGEN and MCNP/G4 simulations, it was demonstrated that the uncertainty of the Cs-137 counting rate can be well controlled within 3.5%. Finally, a full size prototype was tested in comparison with detailed Monte Carlo simulation and the efficiency transfer method was further utilized for efficiency calibration. To reduce the uncertainty in the efficiency transfer process, a standard point source embedded in a graphite sphere was used for efficiency calibration. The correction factor due to pebble self-attenuation was carefully studied.

  20. On the growth of pebble-accreting planetesimals

    NASA Astrophysics Data System (ADS)

    Visser, Rico G.; Ormel, Chris W.

    2016-02-01

    Context. Pebble accretion is a newly discovered mechanism to quickly grow the cores of planets. In pebble accretion, gravity and gas drag conspire to yield large collisional cross sections for small particles in protoplanetary disks. However, before pebble accretion commences, aerodynamic deflection may act to prevent planetesimals from becoming large, because particles tend to follow gas streamlines. Aims: We derive the planetesimal radius where pebble accretion is initiated and determine the growth timescales of planetesimals by sweep-up of small particles. Methods: The equation of motion for a pebble, including gas drag and gravitational interactions, was integrated in three dimensions at distances of 1, 3, and 10 AU from the star. We obtained the collision efficiency factor as the ratio of the numerically obtained collisional cross section to the planetesimal surface area, from which we obtained the growth timescales. Integrations were conducted in the potential flow limit (steady, inviscid) and in the Stokes flow regime (steady, viscid). Results: Only particles of stopping time ts ≪ tX where tX ≈ 103 s experience aerodynamic deflection. Even in this case, the planetesimal's gravity always ensures positive collision factors. The planetesimal radius where growth proceeds slowest is ≈ 100 km (less for colder disks) corresponding to interactions shifting from the geometric to the Safronov focusing regime. For particles ts ≫ tX pebble accretion only commences after this phase and is characterized by a steep drop in growth timescales. At 1 AU, growth timescales are shorter than the disk lifetime for pebbles larger than 0.03 cm. The planetesimal radius RPA where pebble accretion commences increases with disk orbital radius. At distances beyond ~ 10 AU, sweep-up growth times are always longer than 10 Myr, while in the inner disk (≲3 AU) the viability of the sweep-up scenario is determined by the outcome of pebble-planetesimal collisions in the geometric

  1. Recovery and recycling of lithium value from spent lithium titanate (Li2TiO3) pebbles

    NASA Astrophysics Data System (ADS)

    Mandal, D.

    2013-09-01

    In the first generation fusion reactors the fusion of deuterium (D) and tritium (T) is considered to produce energy to meet the future energy demand. Deuterium is available in nature whereas, tritium is not. Lithium-6 (Li6) isotope has the ability to produce tritium in the n, α nuclear reaction with neutrons. Thus lithium-based ceramics enriched by Li6 isotope are considered for the tritium generation for its use in future fusion reactors. Lithium titanate is one such Li-based ceramic material being considered for its some attractive properties viz., high thermal and chemical stability, high thermal conductivity, and low tritium solubility. It is reported in the literature, that the burn up of these pebbles in the fusion reactor will be limited to only 15-17 atomic percentage. At the end of life, the pebbles will contain more than 45% unused Li6 isotope. Due to the high cost of enriched Li6 and the waste disposal considerations, it is necessary to recover the unused Li from the spent lithium titanate pebbles. Till date, only the feasibilities of different processes are reported, but no process details are available. Experiments were carried out for the recovery of Li from simulated Li2TiO3 pebbles and to reuse of lithium in lithium titanate pebble fabrication. The details of the experiments and results are discussed in this paper. Simulated lithium titanate (Li2TiO3) pebbles. The objective of the study is to develop a process which can be used to recover lithium value form the spent Li2TiO3 pebbles from future fusion reactor. The Li2TiO3 pebbles used in the study were synthesized and fabricated by the solid state reaction process developed by Mandal et al. described in details somewhere else [1,2]. Spherical Li2TiO3 pebbles of size 1.0 mm were used and the properties of the Li2TiO3 pebbles used in the study are shown in Table 1. Hydrochloric acid (HCl), of 99.8% purity, purchased from Merck and Loba Chemicals, Mumbai, India. To leach lithium from Li2TiO3

  2. A method for estimating maximum static rainfall retention in pebble mulches used for soil moisture conservation

    NASA Astrophysics Data System (ADS)

    Peng, Hongtao; Lei, Tingwu; Jiang, Zhiyun; Horton, Robert

    2016-06-01

    Mulching of agricultural fields and gardens with pebbles has long been practiced to conserve soil moisture in some semi-arid regions with low precipitation. Rainfall interception by the pebble mulch itself is an important part of the computation of the water balance for the pebble mulched fields and gardens. The mean equivalent diameter (MED) was used to characterize the pebble size. The maximum static rainfall retention in pebble mulch is based on the water penetrating into the pores of pebbles, the water adhering to the outside surfaces of pebbles and the water held between pebbles of the mulch. Equations describing the water penetrating into the pores of pebbles and the water adhering to the outside surface of pebbles are constructed based on the physical properties of water and the pebble characteristics. The model for the water between pebbles of the mulch is based on the basic equation to calculate the water bridge volume and the basic coordination number model. A method to calculate the maximum static rainfall retention in the pebble mulch is presented. Laboratory rain simulation experiments were performed to test the model with measured data. Paired sample t-tests showed no significant differences between the values calculated with the method and the measured data. The model is ready for testing on field mulches.

  3. A novel reusable nanocomposite for complete removal of dyes, heavy metals and microbial load from water based on nanocellulose and silver nano-embedded pebbles.

    PubMed

    Suman; Kardam, Abhishek; Gera, Meeta; Jain, V K

    2015-01-01

    The present work proposed a nanocellulose (NC)-silver nanoparticles (AgNPs) embedded pebbles-based composite material as a novel reusable cost-effective water purification device for complete removal of dyes, heavy metals and microbes. NC was prepared using acid hydrolysis of cellulose. The AgNPs were generated in situ using glucose and embedded within the porous concrete pebbles by the technique of inter-diffusion of ion, providing a very strong binding of nanoparticles within the porous pebbles and thus preventing any nanomaterials leaching. Fabrication of a continual running water purifier was achieved by making different layering of NC and Ag nano-embedded pebbles in a glass column. The water purifier exhibited not only excellent dye and heavy metal adsorption capacity, but also long-term antibacterial activity against pathogenic and non-pathogenic bacterial strains. The adsorption mainly occurred through electrostatic interaction and pore diffusion also contributed to the process. The bed column purifier has shown 99.48% Pb(II) and 98.30% Cr(III) removal efficiency along with 99% decontamination of microbial load at an optimum working pH of 6.0. The high adsorption capacity and reusability, with complete removal of dyes, heavy metals and Escherichia coli from the simulated contaminated water of composite material, will provide new opportunities to develop a cost-effective and eco-friendly water purifier for commercial application. PMID:25243917

  4. Bed bugs.

    PubMed

    Foulke, Galen T; Anderson, Bryan E

    2014-09-01

    The term bed bug is applied to 2 species of genus Cimex: lectularius describes the common or temperate bed bug, and hemipterus its tropical cousin. Cimex lectularius is aptly named; its genus and species derive from the Latin words for bug and bed, respectively. Though the tiny pest is receiving increased public attention and scrutiny, the bed bug is hardly a new problem. PMID:25577850

  5. Tracer-pebble movement along a concave river profile: Virtual velocity in relation to grain size and shear stress

    NASA Astrophysics Data System (ADS)

    Ferguson, R. I.; Wathen, S. J.

    1998-08-01

    Over 1400 tracer pebbles 16-256 mm in diameter were tracked for 2 years in six reaches of Allt Dubhaig, Scotland, a small gravel-bed river along which shear stress and bed surface grain size decrease toward a local base level. Pebble movement was size-selective both within and between reaches. Within reaches the decrease in mean travel distance with increasing grain size is strongest in the coarse tail of the size distribution. Particle shape has a minor secondary effect. A nondimensional grain velocity, averaged over the duration of competent flow, is used to compare different size classes and reaches. Over 90% of its variance is explained by relative grain size and reach Shields stress. The pattern of size selectivity is consistent with single-event tracer results elsewhere, bedload trap data from our distal reach, and the concept of partial mobility. It provides a mechanism for strong downstream fining by selective transport and deposition along rivers in which stress declines toward base level. The nondimensional prediction equation for grain velocity may be of use in other rivers but requires testing.

  6. Comparison of the pebbles of the Shinarump and Moss Back members of the Chinle formation

    USGS Publications Warehouse

    Albee, Howard Franklin

    1956-01-01

    Lithology, color, size, sphericity, and roundness of pebbles from the Shinarurnp and Moss Back members of the Chinle formation were analyzed and compared. The difference in the quartz:quartzite:chert ratios of the pebbles, the presence of limestone and siltstone pebbles, and to a lesser degree,the difference in color of pebbles serve to distinguish the Moss Back from the Shinarump. In areas where both the Moss Back and Shinarump are present, the average ratios of quartz, quartzite, a.nd chert are respectively about 12:37:51 and 82:16:2. Limestone and siltstone pebbles are commonly found in the Moss Back, whereas they are rarely found in the Shinarump. The colors of the Moss Back pebbles are generally darker than those of the Shinarump pebbles. The Moss Back contains more gray to black pebbles and fewer light-colored pebbles, such as red, orange, and white, than the Shinarump. Size, sphericity, and roundness of pebbles do not show a significant difference between the two units. Fossiliferous pebbles in the Moss Back and Shinarump were derived chiefly from sediments of Carboniferous and Permian ages and could have had common sources.

  7. Hoop tensile strength testing of small diameter ceramic particles

    NASA Astrophysics Data System (ADS)

    Wereszczak, A. A.; Jadaan, O. M.; Lin, H.-T.; Champoux, G. J.; Ryan, D. P.

    2007-03-01

    A method to measure hoop tensile strength of 1-mm-diameter brittle ceramic spheres was demonstrated through the use of a 'C-sphere' flexure strength specimen. This innovative specimen geometry was chosen because a simple, monotonically increasing uniaxial compressive force produces a hoop tensile stress at the C-sphere's outer surface that ultimately initiates fracture. This enables strength quantification and strength-limiting-flaw identification of the sphere itself. Such strength information is relevant to design optimization and durability assessments of ceramic fuel particles and breeder/multiplier pebbles for fusion when particle surfaces are subjected to tensile stresses during their manufacturing or service.

  8. On Ceramics.

    ERIC Educational Resources Information Center

    School Arts, 1982

    1982-01-01

    Presents four ceramics activities for secondary-level art classes. Included are directions for primitive kiln construction and glaze making. Two ceramics design activities are described in which students make bizarrely-shaped lidded jars, feet, and footwear. (AM)

  9. Fluidized bed regenerators for Brayton cycles

    NASA Technical Reports Server (NTRS)

    Nichols, L. D.

    1975-01-01

    A recuperator consisting of two fluidized bed regenerators with circulating solid particles is considered for use in a Brayton cycle. These fluidized beds offer the possibility of high temperature operation if ceramic particles are used. Calculations of the efficiency and size of fluidized bed regenerators for typical values of operating parameters were made and compared to a shell and tube recuperator. The calculations indicate that the fluidized beds will be more compact than the shell and tube as well as offering a high temperature operating capability.

  10. Fluidized bed regenerators for Brayton cycles

    NASA Technical Reports Server (NTRS)

    Nichols, L. D.

    1975-01-01

    A recuperator consisting of two fluidized bed regenerators with circulating solid particles is considered for use in a Brayton cycle. These fluidized beds offer the possibility of high temperature operation if ceramic particles are used. Calculations of the efficiency and size of fluidized bed regenerators for typical values of operating parameters have been made and compared to a shell and tube recuperator. The calculations indicate that the fluidized beds will be more compact than the shell and tube as well as offering a high temperature operating capability.

  11. Structural Ceramics

    NASA Technical Reports Server (NTRS)

    1986-01-01

    This publication is a compilation of abstracts and slides of papers presented at the NASA Lewis Structural Ceramics Workshop. Collectively, these papers depict the scope of NASA Lewis' structural ceramics program. The technical areas include monolithic SiC and Si3N4 development, ceramic matrix composites, tribology, design methodology, nondestructive evaluation (NDE), fracture mechanics, and corrosion.

  12. First-order control of surface roughness at three scales: boundary layer dynamics, tracer dispersion and pebble abrasion

    NASA Astrophysics Data System (ADS)

    Jerolmack, D. J.; Litwin, K. L.; Phillips, C. B.; Martin, R. L.

    2012-12-01

    In many situations it may be appropriate to treat surfaces as smooth and particles as spherical, however here we focus on scenarios in which the roughness of the surface exerts a first-order control on flow and transport dynamics. We describe three vignettes at three different scales: (1) roughness transitions and resulting sediment transport dynamics over ~10-km distance in a desert dune field; (2) reach-scale river bed roughness and its influence on dispersion of tracer particles in bed load; and (3) the control of particle surface roughness on the nature and rate of pebble abrasion. For (1), we show how the abrupt transition from a flat surface to a dune field may be treated as a step increase in the aerodynamic roughness parameter - so long as the spatial scale considered is significantly larger than that of an individual dune. This increase causes a spatial decline in the boundary stress downwind that may be understood using simple boundary layer theory, resulting in a factor of three decrease in the sand flux over a distance of kilometers. For (2), laboratory and field studies of tracer particles in bed load indicate that they undergo short flights separated by long rest periods having a power-law tail - even in steady flows. We hypothesize that for near-threshold transport - which predominates is coarse-grained rivers - particles become trapped in 'wells' produced by surface roughness, and their rest time is controlled by the time for the surface to scour down and release them. Laboratory observations support this hypothesis, while comparison to non-geophysical 'flows' indicates that these dynamics are generic to transport in disordered systems. Finally, for (3) we report laboratory experiments by our group and others showing how abrasion rate decreases with decreasing particle roughness. Geometric models quantitatively support the intuition that locations of high positive curvature on pebble surfaces are more susceptible to abrasion; as they are

  13. Universal scaling relations for pebble abrasion

    NASA Astrophysics Data System (ADS)

    Litwin, K. L.; Jerolmack, D. J.

    2012-12-01

    The process of abrasion of gravel in bed load transport results from particle-to-particle collisions, where the energy involved is sufficient to cause chipping and spallation but not fragmentation of parent grains. The removed rock material is not infinitesimal; daughter products as large as coarse sand can be produced. Although previous work has shown that lithology, grain shape, and energy of collision are contributing factors that control abrasion rates of river-bed material, little is known regarding the relationship between these factors and diminution rates. Here we explicitly isolate and investigate how these three factors influence rates of abrasion and the size distribution of daughter products, with laboratory experiments. The apparatus is a double pendulum (Newton's cradle) that produces well-controlled binary collisions. A high-speed camera precisely measures collision energy, while mass of parent rocks. and the size and shape distributions of daughter products, are measured periodically. We examined abrasion of initially square-cut 'rocks' as they underwent successive collisions in the binary collision apparatus. We have examined mass loss rate for varied lithologies, and observe a similar power-law relationship between impact energy and mass abraded. When normalized by sensible material properties, mass loss curves for all materials collapse onto a single curve, suggesting that the underlying mechanics of abrasion for different materials are the same. The relationship does not display the linear trend expected from pure energetics, and we suggest that this is a shape effect as protruding - and hence easily eroded - corners are worn away. Analysis of daughter-product particle size distributions for different lithology fragments - including natural rocks and also bricks - show the same functional form. Surprisingly, it is the power-law relation expected for brittle materials undergoing fragmentation. This suggests that brittle fracture theory also

  14. Fluorescent nano-PEBBLE sensors designed for intracellular glucose imaging.

    PubMed

    Xu, Hao; Aylott, Jonathan W; Kopelman, Raoul

    2002-11-01

    Polyacrylamide-based, ratiometric, spherical, optical nanosensors, or polyacrylamide PEBBLEs (Probes Encapsulated By Biologically Localized Embedding), have been fabricated, aimed at real-time glucose imaging in intact biological systems, i.e. living cells. These nanosensors are prepared using a microemulsion polymerization process, and their average size is about 45 nm in diameter. The sensors incorporate glucose oxidase (GOx), an oxygen sensitive fluorescent indicator (Ru[dpp(SO3Na)2]3)Cl2, and an oxygen insensitive fluorescent dye, Oregon Green 488-dextran or Texas Red-dextran, as a reference for the purpose of ratiometric intensity measurements. The enzymatic oxidation of glucose to gluconic acid results in the local depletion of oxygen, which is measured by the oxygen sensitive ruthenium dye. The small size and inert matrix of these sensors allows them to be inserted into living cells with minimal physical and chemical perturbations to their biological functions. The PEBBLE matrix protects the enzyme and fluorescent dyes from interference by proteins in cells, enabling reliable in vivo chemical analysis. Conversely, the matrix also significantly reduces the toxicity of the indicator and reference dyes to the cells, so that a larger variety of dyes can be used in optimal fashion. Furthermore, the PEBBLE matrix enables the synergistic approach in which there is a steady state of local oxygen consumption, and this cannot be achieved by separately introducing free enzyme and dyes into a cell. The work presented here describes the production and characterization of glucose sensitive PEBBLEs, and their potential for intracellular glucose measurements. The sensor response is determined in terms of the linear range, ratiometric operation, response time, sensor stability, reversibility and immunity to interferences. PMID:12475037

  15. Uranium assessment for the Precambrian pebble conglomerates in southeastern Wyoming

    SciTech Connect

    Borgman, L.E.; Sever, C.; Quimby, W.F.; Andrew, M.E.; Karlstrom, K.E.; Houston, R.S.

    1981-03-01

    This volume is a geostatistical resource estimate of uranium and thorium in quartz-pebble conglomerates, and is a companion to Volume 1: The Geology and Uranium Potential to Precambrian Conglomerates in the Medicine Bow Mountains and Sierra Madre of Southeastern Wyoming; and to Volume 2: Drill-Hole Data, Drill-Site Geology, and Geochemical Data from the Study of Precambrian Uraniferous Conglomerates of the Medicine Bow Mountains and the Sierra Madre of Southeastern Wyoming.

  16. Pebble orientation on large, experimental debris-flow deposits

    USGS Publications Warehouse

    Major, J.J.

    1998-01-01

    Replicable, pronounced orientation of discoid pebbles (??? 8 mm) embedded on surfaces of large (??? 10 m3) experimental debris-flow deposits reveals that strongly aligned, imbricate fabric can develop rapidly over short distances in mass flows. Pebble long axes aligned subparallel to deposit margins as well as subparallel to margins of surge waves arrested within the deposits. Pebble alignment exhibited modes both parallel to (a(p)), and normal to (a(t)), the primary flow direction; intermediate axes dipped preferentially inward from surge-wave margins (b(i) orientation). Repetitive development of margin-parallel, imbricate fabric distributed across deposit surfaces provides compelling evidence that deposits formed dominantly through progressive incremental accretion rather than through simple en masse emplacement. Pronounced fabric along deposit and arrested surge-wave margins reflects significant grain interaction along flow margins. This sedimentological evidence for significant marginal grain interaction complements theoretical analyses (Iverson, 1997) and other experimental data (Major, 1996: Iverson, 1997) that indicate that resistance along flow margins is an important factor affecting debris-flow deposition. The fabric on the experimental deposits demonstrates that debris flows can develop strongly imbricate particle orientation that mimics fabric developed during fluvial deposition. Particle shape and local stress fields appear to have more control over fabric development than does general depositional process. Other criteria in addition to particle orientation are needed to discriminate mass flow from fluvial gravel deposits and to unravel depositional history. ?? 1998 Elsevier Science B.V. All rights reserved.

  17. Evaluation of the Accumulation of Trace Metals (as, U, CR, CU, PB, Zn) on Iron-Manganese Coatings on in Situ Stream Pebbles and Emplaced Substrates

    NASA Astrophysics Data System (ADS)

    Turpin, M. M.; Blake, J.; Crossey, L. J.; Ali, A.; Hansson, L.

    2015-12-01

    Exposure to trace metals (As, U, Cr, Cu, Pb, Zn) has potential negative health effects on human populations and wildlife. Geothermal waters often have elevated concentrations of trace elements and understanding the geochemical cycling of these elements can be challenging. Previous studies have utilized in situ stream pebbles and glass or ceramic substrates with iron-manganese oxide coatings to understand contamination and or chemical cycling. This project's main focus is to develop an ideal tracing method using adsorption onto substrate surfaces and to define key parameters that are necessary for the phenomenon of adsorption between trace metals and these surface coatings to occur. Sampling locations include the Jemez River and Rio San Antonio in the Jemez mountains, northern New Mexico. Both streams have significant geothermal inputs. Pebbles and cobbles were gathered from the active stream channel and 6mm glass beads and 2 X1 in. ceramic plates were placed in streams for three weeks to allow for coating accumulation. Factors such as leachate type, water pH, substrate type, coating accumulation period and leach time were all considered in this experiment. It was found that of the three leachates (aqua regia, 10% aqua regia and hydroxylamine), hydroxylamine was the most effective at leaching coatings without dissolving substrates. Samples leached with aqua regia and 10% aqua regia were found to lose weight and mass over the following 5, 7, and 10 day measurements. Glass beads were determined to be more effective than in stream pebbles as an accumulation substrate: coatings were more easily controlled and monitored. Samples leached with hydroxylamine for 5 hours and 72 hours showed little difference in their leachate concentrations, suggesting that leach time has little impact on the concentration of leachate samples. This research aims to find the best method for trace metal accumulation in streams to aid in understanding geochemical cycling.

  18. Ceramic burner

    SciTech Connect

    Laux, W.; Hebel, R.; Artelt, P.; Esfeld, G.; Jacob, A.

    1981-03-31

    Improvements in the mixing body and supporting structure of a molded-ceramic-brick burner enable the burner to withstand the vibrations induced during its operation. Designed for the combustion chambers of air heaters, the burner has a mixing body composed of layers of shaped ceramic bricks that interlock and are held together vertically by a ceramic holding bar. The mixing body is shaped like a mushroom - the upper layers have a larger radius than the lower ones.

  19. Ceramic Processing

    SciTech Connect

    EWSUK,KEVIN G.

    1999-11-24

    Ceramics represent a unique class of materials that are distinguished from common metals and plastics by their: (1) high hardness, stiffness, and good wear properties (i.e., abrasion resistance); (2) ability to withstand high temperatures (i.e., refractoriness); (3) chemical durability; and (4) electrical properties that allow them to be electrical insulators, semiconductors, or ionic conductors. Ceramics can be broken down into two general categories, traditional and advanced ceramics. Traditional ceramics include common household products such as clay pots, tiles, pipe, and bricks, porcelain china, sinks, and electrical insulators, and thermally insulating refractory bricks for ovens and fireplaces. Advanced ceramics, also referred to as ''high-tech'' ceramics, include products such as spark plug bodies, piston rings, catalyst supports, and water pump seals for automobiles, thermally insulating tiles for the space shuttle, sodium vapor lamp tubes in streetlights, and the capacitors, resistors, transducers, and varistors in the solid-state electronics we use daily. The major differences between traditional and advanced ceramics are in the processing tolerances and cost. Traditional ceramics are manufactured with inexpensive raw materials, are relatively tolerant of minor process deviations, and are relatively inexpensive. Advanced ceramics are typically made with more refined raw materials and processing to optimize a given property or combination of properties (e.g., mechanical, electrical, dielectric, optical, thermal, physical, and/or magnetic) for a given application. Advanced ceramics generally have improved performance and reliability over traditional ceramics, but are typically more expensive. Additionally, advanced ceramics are typically more sensitive to the chemical and physical defects present in the starting raw materials, or those that are introduced during manufacturing.

  20. Ceramic joining

    SciTech Connect

    Loehman, R.E.

    1996-04-01

    This paper describes the relation between reactions at ceramic-metal interfaces and the development of strong interfacial bonds in ceramic joining. Studies on a number of systems are described, including silicon nitrides, aluminium nitrides, mullite, and aluminium oxides. Joints can be weakened by stresses such as thermal expansion mismatch. Ceramic joining is used in a variety of applications such as solid oxide fuel cells.

  1. Ceramic filters

    SciTech Connect

    Holmes, B.L.; Janney, M.A.

    1995-12-31

    Filters were formed from ceramic fibers, organic fibers, and a ceramic bond phase using a papermaking technique. The distribution of particulate ceramic bond phase was determined using a model silicon carbide system. As the ceramic fiber increased in length and diameter the distance between particles decreased. The calculated number of particles per area showed good agreement with the observed value. After firing, the papers were characterized using a biaxial load test. The strength of papers was proportional to the amount of bond phase included in the paper. All samples exhibited strain-tolerant behavior.

  2. Stepped-anneal helium release in 1-mm beryllium pebbles from COBRA-1A2

    SciTech Connect

    Oliver, B.M.

    1998-03-01

    Stepped-anneal helium release measurements on two sets of fifteen beryllium pebbles irradiated in the Experimental Breeder Reactor-II (EBR-II) at Argonne National Laboratory-West (ANL-w), are reported. The purpose of the measurements was to determine the helium release characteristics of the beryllium using larger sample sizes and longer anneal times relative to earlier measurements. Sequential helium analyses were conducted over a narrower temperature range from approximately 800 C to 1100 C in 100 C increments, but with longer anneal time periods. To allow for overnight and unattended operation, a temperature controller and associated circuitry were added to the experimental setup. Observed helium release was nonlinear with time at each temperature interval, with each step being generally characterized by an initial release rate followed by a slowing of the rate over time. Sample Be-C03 showed a leveling off in the helium release after approximately 3 hours at a temperature of 890 C. Sample Be-D03, on the other hand, showed a leveling off only after {approximately}12 to 24 hours at a temperature of 1100 C. This trend is consistent with that observed in earlier measurements on single microspheres from the same two beryllium lots. None of the lower temperature steps showed any leveling off of the helium release. Relative to the total helium concentrations measured earlier, the total helium releases observed here represent approximately 80% and 92% of the estimated total helium in the C03 and D03 samples, respectively.

  3. High temperature chemical compatibility between SiC composites and Be pebbles

    NASA Astrophysics Data System (ADS)

    Alves, L. C.; Paúl, A.; da Silva, M. R.; Alves, E.; Riccardi, B.; Soares, J. C.

    2003-09-01

    SiC composite reinforced fibres are still considered to be an important material to be used in nuclear fusion reactors due to their high temperature and low neutron activation properties. Two different kinds of SiC/SiC f composite were manufactured, one of them presenting an extra SiC coating obtained by chemical vapour deposition technique. Several samples of both materials were placed inside a Be pebble bed and the whole set-up annealed at 800 °C for 550 h in a reducing atmosphere, simulating fusion reactor conditions. Surface chemical reactions were investigated with nuclear microprobe analyses techniques and complemented with SEM analysis. For the uncoated samples, surface oxidation is accompanied by a strong C depletion and a Be diffusion. Two different behaviours were found for the coated samples. One of those samples showed extended regions where surface was left almost unaltered. The general behaviour, however, was an increase in the number and extension of the cracks already observed at the surface of the coated virgin samples.

  4. Advanced multi-dimensional deterministic transport computational capability for safety analysis of pebble-bed reactors

    NASA Astrophysics Data System (ADS)

    Tyobeka, Bismark Mzubanzi

    A coupled neutron transport thermal-hydraulics code system with both diffusion and transport theory capabilities is presented. At the heart of the coupled code is a powerful neutronics solver, based on a neutron transport theory approach, powered by the time-dependent extension of the well known DORT code, DORT-TD. DORT-TD uses a fully implicit time integration scheme and is coupled via a general interface to the thermal-hydraulics code THERMIX-DIREKT, an HTR-specific two dimensional core thermal-hydraulics code. Feedback is accounted for by interpolating multigroup cross sections from pre-generated libraries which are structured for user specified discrete sets of thermal-hydraulic parameters e.g. fuel and moderator temperatures. The coupled code system is applied to two HTGR designs, the PBMR 400MW and the PBMR 268MW. Steady-state and several design basis transients are modeled in an effort to discern with the adequacy of using neutron diffusion theory as against the more accurate but yet computationally expensive neutron transport theory. It turns out that there are small but significant differences in the results from using either of the two theories. It is concluded that diffusion theory can be used with a higher degree of confidence in the PBMR as long as more than two energy groups are used and that the result must be checked against lower order transport solution, especially for safety analysis purposes. The end product of this thesis is a high fidelity, state-of-the-art computer code system, with multiple capabilities to analyze all PBMR safety related transients in an accurate and efficient manner.

  5. 3-D transient analysis of pebble-bed HTGR by TORT-TD/ATTICA3D

    SciTech Connect

    Seubert, A.; Sureda, A.; Lapins, J.; Buck, M.; Bader, J.; Laurien, E.

    2012-07-01

    As most of the acceptance criteria are local core parameters, application of transient 3-D fine mesh neutron transport and thermal hydraulics coupled codes is mandatory for best estimate evaluations of safety margins. This also applies to high-temperature gas cooled reactors (HTGR). Application of 3-D fine-mesh transient transport codes using few energy groups coupled with 3-D thermal hydraulics codes becomes feasible in view of increasing computing power. This paper describes the discrete ordinates based coupled code system TORT-TD/ATTICA3D that has recently been extended by a fine-mesh diffusion solver. Based on transient analyses for the PBMR-400 design, the transport/diffusion capabilities are demonstrated and 3-D local flux and power redistribution effects during a partial control rod withdrawal are shown. (authors)

  6. Study of Li 2TiO 3 + 5 mol% TiO 2 lithium ceramics after long-term neutron irradiation

    NASA Astrophysics Data System (ADS)

    Chikhray, Y.; Shestakov, V.; Maksimkin, O.; Turubarova, L.; Osipov, I.; Kulsartov, T.; Kuykabayeba, A.; Tazhibayeva, I.; Kawamura, H.; Tsuchiya, K.

    2009-04-01

    Given work presents the results of complex material-science studies of 1 mm diameter ceramic pebbles manufactured of Li 2TiO 3 + 5 mol% TiO 2 ceramics before and after long-time neutron irradiation. Ceramic samples were placed in specially ampoules (six items) made of stainless steel Cr18Ni10Ti which were vacuumized and filled with helium. Irradiation of ampoules was carried out in the loop channel of WWRK reactor (Almaty, Kazakhstan) during 223 days at 6 MW power. After irradiation light-colored pebbles became grey-colored due to structure changes which generation of grey-colored inclusions (lithium oxide) with low density and microhardness. There is a radiation softening of lithium ceramic and that effect is higher for lower irradiation temperature 760 K than for 920 K. The value of maximum permissible load (pebble crash limit) at that is low and comprises ˜37.9 N. The content of residual tritium is higher for ceramic irradiated at 760 K (6.6 ± 0.6 × 10 11 Bq/kg) than for ceramic irradiated at 920 K (17 ± 3 × 10 10 Bq/kg). The size change indicates that pebble increase more after irradiation at 760 K than at 920 K where the bigger portion of tritium leaves the pebble. X-ray analysis shows radiation modification of Li 2TiO 3 + 5 mol% TiO 2 phase composition and generation of new phases: LiTi 2O 4, LiTiO 2 and Li 4Ti 5O 12.

  7. PUCs move to halt Pebble Springs, Limerick nukes

    SciTech Connect

    Not Available

    1982-06-01

    Public utility commission (PUC) opposition to nuclear-power-plant construction in Oregon and Pennsylvania indicates a new trend for PUCs to take the initiative against nuclear projects. By not allowing utilities to finance new plants with construction work in progress (CWIP) costs added to the rate base, the Pennsylvania PUC essentially cancelled the Limerick units in accordance with the sentiment of the state legislature. The Oregon PUC ordered Pacific Power and Light Co. to write off investments in two Pebble Springs units and retire the financial liability. Both issues will be settled in the courts. (DCK)

  8. Solar heated fluidized bed gasification system

    NASA Technical Reports Server (NTRS)

    Qader, S. A. (Inventor)

    1981-01-01

    A solar-powered fluidized bed gasification system for gasifying carbonaceous material is presented. The system includes a solar gasifier which is heated by fluidizing gas and steam. Energy to heat the gas and steam is supplied by a high heat capacity refractory honeycomb which surrounds the fluid bed reactor zone. The high heat capacity refractory honeycomb is heated by solar energy focused on the honeycomb by solar concentrator through solar window. The fluid bed reaction zone is also heated directly and uniformly by thermal contact of the high heat capacity ceramic honeycomb with the walls of the fluidized bed reactor. Provisions are also made for recovering and recycling catalysts used in the gasification process. Back-up furnace is provided for start-up procedures and for supplying heat to the fluid bed reaction zone when adequate supplies of solar energy are not available.

  9. Ceramic Powders

    NASA Technical Reports Server (NTRS)

    1984-01-01

    In developing its product line of specialty ceramic powders and related products for government and industrial customers, including companies in the oil, automotive, electronics and nuclear industries, Advanced Refractory Technologies sought technical assistance from NERAC, Inc. in specific areas of ceramic materials and silicon technology, and for assistance in identifying possible applications of these materials in government programs and in the automotive and electronics industry. NERAC conducted a computerized search of several data bases and provided extensive information in the subject areas requested. NERAC's assistance resulted in transfer of technologies that helped ART staff develop a unique method for manufacture of ceramic materials to precise customer specifications.

  10. Processing ceramics

    NASA Technical Reports Server (NTRS)

    Moritoki, M.; Fujikawa, T.; Miyanaga, J.

    1984-01-01

    A method of hot hydrostatic pressing of ceramics is described. A detailed description of the invention is given. The invention is explained through an example, and a figure illustrates the temperature and pressure during the hot hydrostatic pressing treatment.

  11. Bed Bugs FAQs

    MedlinePlus

    ... Tropical Diseases Laboratory Diagnostic Assistance [DPDx] Parasites Home Bed Bugs FAQs Recommend on Facebook Tweet Share Compartir On ... are bed bugs treated and prevented? What are bed bugs? Bed bugs ( Cimex lectularius ) are small, flat, parasitic ...

  12. The Formation of Terrestrial Planets from the Direct Accretion of Pebbles

    NASA Astrophysics Data System (ADS)

    Levison, Harold F.; Kretke, Katherine; Walsh, Kevin

    2014-11-01

    A radical new scenario has recently been suggested for the formation of giant planet cores that reports to solve this long-standing problem. This scenario, known as pebble accretion, envisions: 1) Planetesimals form directly from millimeter- to meter-sized objects (the pebbles) that are concentrated by turbulent eddies and then gravitationally collapse to form 100 — 1000 km objects (Cuzzi+ 2008, AJ 687, 1432; Johansen+ 2007, Nature 448, 1022). 2) These planetesimals quickly sweep up the remaining pebbles because their capture cross sections are significantly enhanced by aerodynamic drag (Lambrechts & Johansen 2012, A&A 544, A32; Ormel & Klahr (2010) A&A Volume 520, id.A43). Calculations show that a single 1000 km object embedded in a swarm of pebbles can grow to ~10 Earth-masses in less than 10,000 years. These short timescales present a problem in the terrestrial planet region because it took many tens of millions of years for the Earth to form (Touboul+ 2007, Nature 450, 1206). However, recent full-scale simulations of core formation have shown that the only way to grow a small number of giant planets in the Solar System is for the pebbles to form over a long period of time (Kretke & Levison 2014, AJ, submitted; Levison & Kretke in prep.) in a process we call 'Slow Pebble Accretion'. Thus, here we will present preliminary results of a study of slow pebble accretion in the terrestrial planet zone.

  13. Support services for ceramic fiber-ceramic matrix composites. Annual technical progress report

    SciTech Connect

    Hurley, J.P.; Nowok, J.W.

    1996-12-27

    Ceramic and advanced alloy corrosion in fossil energy systems is being investigated. During 1995-6, ash was collected for testing corrosion resistance of materials in air-blown fluidized-bed gasification systems. Descriptions of the activities are presented in this report, which is an extension of a technical paper on testing corrosion rates of ceramics in coal gasification systems. A section of this report covers factors affecting the composition of ash deposits.

  14. Structural Ceramics Database

    National Institute of Standards and Technology Data Gateway

    SRD 30 NIST Structural Ceramics Database (Web, free access)   The NIST Structural Ceramics Database (WebSCD) provides evaluated materials property data for a wide range of advanced ceramics known variously as structural ceramics, engineering ceramics, and fine ceramics.

  15. The colloidal chemistry of ceramic clays

    NASA Technical Reports Server (NTRS)

    Phelps, G. W.

    1984-01-01

    The colloidal chemistry and mineralogy of two argil minerals were studied. Deposits of kaolin and of ceramic clays in the United States and England are discussed for the probable mechanism of formation. The structural modifications of the bed, original material associated with the clays and the proper use of flocculants are discussed.

  16. Nanoparticle PEBBLE sensors in live cells and in vivo

    PubMed Central

    Smith, Ron

    2009-01-01

    Nanoparticle sensors have been developed for imaging and dynamic monitoring, in live cells and in vivo, of the molecular or ionic components, constructs, forces and dynamics, all in real time, during biological/chemical/physical processes. With their biocompatible small size and inert matrix, nanoparticle sensors have been successfully applied for non-invasive real-time measurements of analytes and fields in cells and rodents, with spatial, temporal, physical and chemical resolution. This review describes the diverse designs of nanoparticle sensors for ions and small molecules, physical fields and biological features, as well as the characterization, properties, and applications of these nanosensors to in vitro and in vivo measurements. Their floating as well as localization ability in biological media is captured by the acronym PEBBLE: photonic explorer for bioanalysis with biologically localized embedding. PMID:20098636

  17. Ceramics Analysis

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Lewis Research Center developed the CARES/LIFE software, which predicts the performance of brittle structures over time, such as ceramic compounds. Over 300 companies have used a version of the code, including Philips Display Components Company, AlliedSignal, Solar Turbines Incorporated, and TRW, Inc. for everything from engines to television tubes. The software enables a designer to test a variety of configurations for probability of failure and to adjust the structure's geometry to minimize the predicted failure or maximize durability for the lifetime of the ceramic component.

  18. Moving granular-bed filter development program. Topical report

    SciTech Connect

    Newby, R.A.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1994-04-01

    Advanced, coal-based, power plants, such as IGCC and Advanced-PFBC, are currently nearing commercial demonstration. These power plant technologies require hot gas filtration as part of their gas cleaning trains. Ceramic barrier filters are the major filter candidates being developed for these hot gas cleaning applications. While ceramic barrier filters achieve high levels of particle removal, concerns exist for their reliability and operability in these applications. An alternative hot gas filtration technology is the moving granular bed filter. An advanced, moving granular bed filter has been conceived, and early development activities performed by the Westinghouse Electric Corporation, Science and Technology Center. This document reports on the Base Contract tasks performed to resolve the barrier technical issues for this technology. The concept, the Standleg Moving Granular Bed Filter (SMGBF) has a concurrent downward, gas and bed media flow configuration that results in simplified features and improved scaleup feasibility compared to alternative designs. Two modes of bed media operation were assessed in the program: once-through using pelletized power plant waste as bed media, and recycle of bed media via standleg and pneumatic transport techniques. Cold Model testing; high-temperature, high-pressure testing; and pelletization testing using advanced power plant wastes, have been conducted in the program. A commercial, economic assessment of the SMGBF technology was performed for IGCC and Advanced-PFBC applications. The evaluation shows that the barrier technical issues can be resolved, and that the technology is potentially competitive with ceramic barrier filters.

  19. Forming Giant Planet Cores by Pebble Accretion -- Why Slow and Steady wins the Race

    NASA Astrophysics Data System (ADS)

    Kretke, Katherine A.; Levison, Harold F.

    2014-05-01

    In recent years there has been a radical new solution proposed to solve the problem of giant planet core formation. "Pebbles", particles ranging from centimeters to meters in size, have been shown to accrete extremely efficiently due to aerodynamic drag. Large capture cross-sections combined with fast pebble drift rates can allow a single planetesimal to grow from Ceres size to 10s of Earth masses well within the lifetime of gaseous circumstellar disks. However, at large sizes, the the capture-cross section of pebbles goes with the Hill sphere, forcing pebble accretion to becomes a fundamentally "oligarchic-like" process. This makes it difficult to form a few giant planet cores; instead a more generic result is many 10s to 100s of competing oligarchs. In this work, we present a way to get around this oligarchic dilemma If pebbles are assumed to form slowly over a long period of time, then the planetesimal growth rates are slow enough for the planetesimals to dynamically excite each other. As the larger planetisimals/proto-planets stir their smaller companions, these smaller bodies are excited to such a degree that they spend only a small fraction of their orbits embedded in the cooler pebble disk. This allows the larger bodies to starve their neighbors and maintain a relative runaway growth rate to high mass, effectively forming the cores of giant planets.

  20. ATTAP/AGT101 - Year 2 progress in ceramic technology development

    NASA Technical Reports Server (NTRS)

    Kidwell, J. R.; Lindberg, L. J.; Morey, R. E.

    1990-01-01

    The progress made by the Advanced Turbine Technology Applications Project (ATTAP) is summarized, with emphasis on the following areas: ceramic materials assessment and characterization, ceramic impact damage assessment, ceramic combustor evaluation, turbine inlet particle separator development, impact-tolerant turbine designs, and net-shape ceramic component fabrications. In the evolutionary ceramics development in the Automotive Gas Turbine (AGT101) and ATTAP programs initial designs were conceived to reduce stresses by using well-established criteria: bodies of revolution were preferred over nonaxisymmetric geometries, sharp corners were avoided, the contact area between components was kept as large as possible, and small parts were preferred over large when feasible. Projects discussed include: initial ceramic component fabrication by ceramic suppliers in 1990, engine test to 1371 C in 1991, 100-hr test bed engine durability test in 1991, and 300-hr test bed engine durability in 1992.

  1. Performance of ceramic membrane filters

    SciTech Connect

    Ahluwalia, R.K.; Im, K.H.; Geyer, H.K.; Shelleman, D.L.; Tressler, R.E.

    1996-08-01

    CeraMem Corp.`s ceramic-membrane coated, dead-end ceramic filters offer a promising alternative to ceramic candle filters providing long-term operational and reliability issues are resolved: regenerability of filter passages by back pulse cleaning, tolerance to alkali-containing combustion gas and thermal/chemical aging. ANL is responsible for analytical modeling of filtration and pulse cleaning operations, flow-through testing, and prediction of filter response to thermal cycling under realistic service conditions. A test apparatus was built to expose ceramic filter specimens to chemical environments simulating operation of pressurized fluidized bed and integrated gasification combined cycle plants. Four long-duration tests have been conducted in which 100-cpsi channel filters were exposed to ash collected downstream of the cyclone separator at the PFBC plant at Tidd. Results are discussed. Focus has now shifted to exposing the advanced candle filter specimens to reducing gas environments containing NaCl, H{sub 2}S, H{sub 2}O, and gasification ash.

  2. Packed Bed Reactor Experiment

    NASA Video Gallery

    The purpose of the Packed Bed Reactor Experiment in low gravity is to determine how a mixture of gas and liquid flows through a packed bed in reduced gravity. A packed bed consists of a metal pipe ...

  3. The radial dependence of pebble accretion rates: A source of diversity in planetary systems. I. Analytical formulation

    NASA Astrophysics Data System (ADS)

    Ida, S.; Guillot, T.; Morbidelli, A.

    2016-06-01

    Context. The classical planetesimal accretion scenario for the formation of planets has recently evolved with the idea that pebbles, centimeter- to meter-sized icy grains migrating in protoplanetary disks, can control planetesimal and/or planetary growth. Aims: We investigate how pebble accretion depends on disk properties and affects the formation of planetary systems. Methods: We construct analytical models of pebble accretion onto planetary embryos that consistently account for the mass and orbital evolution of the pebble flow and reflect disk structure. Results: We derive simple formulas for pebble accretion rates in the so-called settling regime for planetary embryos that are more than 100 km in size. For relatively smaller embryos or in outer disk regions, the accretion mode is three-dimensional (3D), meaning that the thickness of the pebble flow must be taken into account, and resulting in an accretion rate that is independent of the embryo mass. For larger embryos or in inner regions, the accretion is in a two-dimensional (2D) mode, i.e., the pebble disk may be considered infinitely thin. We show that the radial dependence of the pebble accretion rate is different (even the sign of the power-law exponent changes) for different disk conditions such as the disk heating source (viscous heating or stellar irradiation), drag law (Stokes or Epstein, and weak or strong coupling), and in the 2D or 3D accretion modes. We also discuss the effect of the sublimation and destruction of icy pebbles inside the snow line. Conclusions: Pebble accretion easily produces a large diversity of planetary systems. In other words, to infer the results of planet formation through pebble accretion correctly, detailed prescriptions of disk evolution and pebble growth, sublimation, destruction and migration are required.

  4. Microwave processing of ceramics

    SciTech Connect

    Katz, J.D.

    1989-01-01

    This paper discusses the following topics on microwave processing of ceramics: Microwave-material interactions; anticipated advantage of microwave sintering; ceramic sintering; and ceramic joining. 24 refs., 4 figs. (LSP)

  5. Penn State geoPebble system: Design,Implementation, and Initial Results

    NASA Astrophysics Data System (ADS)

    Urbina, J. V.; Anandakrishnan, S.; Bilen, S. G.; Fleishman, A.; Burkett, P.

    2014-12-01

    The Penn State geoPebble system is a new network of wirelessly interconnected seismic and GPS sensor nodes with flexible architecture. This network will be used for studies of ice sheets in Antarctica and Greenland, as well as to investigate mountain glaciers. The network will consist of ˜150 geoPebbles that can be deployed in a user-defined spatial geometry. We present our design methodology, which has enabled us to develop these state-of- the art sensors using commercial-off-the-shelf hardware combined with custom-designed hardware and software. Each geoPebble is a self- contained, wirelessly connected sensor for collecting seismic measurements and position information. Key elements of each node encompasses a three-component seismic recorder, which includes an amplifier, filter, and 24- bit analog-to-digital converter that can sample up to 10 kHz. Each unit also includes a microphone channel to record the ground-coupled airwave. The timing for each node is available from GPS measurements and a local precision oscillator that is conditioned by the GPS timing pulses. In addition, we record the carrier-phase measurement of the L1 GPS signal in order to determine location at sub-decimeter accuracy (relative to other geoPebbles within a few kilometers radius). Each geoPebble includes 16 GB of solid-state storage, wireless communications capability to a central supervisory unit, and auxiliary measurements capability (including tilt from accelerometers, absolute orientation from magnetometers and temperature). A novel aspect of the geoPebble is a wireless charging system for the internal battery (using inductive coupling techniques). The geoPebbles include all the sensors (geophones, GPS, microphone), communications (WiFi), and power (battery and charging) internally, so the geoPebble system can operate without any cabling connections (though we do provide an external connector so that different geophones can be used). We report initial field-deployment results and

  6. Spatial Distribution of Bed Particles in Natural Boulder-Bed Streams

    NASA Astrophysics Data System (ADS)

    Clancy, K. F.; Prestegaard, K. L.

    2001-12-01

    The Wolman pebble count is used to obtain the size distribution of bed particles in natural streams. Statistics such as median particle size (D50) are used in resistance calculations. Additional information such as bed particle heterogeneity may also be obtained from the particle distribution, which is used to predict sediment transport rates (Hey, 1979), (Ferguson, Prestegaard, Ashworth, 1989). Boulder-bed streams have an extreme range of particles in the particle size distribution ranging from sand size particles to particles larger than 0.5-m. A study of a natural boulder-bed reach demonstrated that the spatial distribution of the particles is a significant factor in predicting sediment transport and stream bed and bank stability. Further experiments were performed to test the limits of the spatial distribution's effect on sediment transport. Three stream reaches 40-m in length were selected with similar hydrologic characteristics and spatial distributions but varying average size particles. We used a grid 0.5 by 0.5-m and measured four particles within each grid cell. Digital photographs of the streambed were taken in each grid cell. The photographs were examined using image analysis software to obtain particle size and position of the largest particles (D84) within the reach's particle distribution. Cross section, topography and stream depth were surveyed. Velocity and velocity profiles were measured and recorded. With these data and additional surveys of bankfull floods, we tested the significance of the spatial distributions as average particle size decreases. The spatial distribution of streambed particles may provide information about stream valley formation, bank stability, sediment transport, and the growth rate of riparian vegetation.

  7. A panoptic model for planetesimal formation and pebble delivery

    NASA Astrophysics Data System (ADS)

    Krijt, S.; Ormel, C. W.; Dominik, C.; Tielens, A. G. G. M.

    2016-02-01

    Context. The journey from dust particle to planetesimal involves physical processes acting on scales ranging from micrometers (the sticking and restructuring of aggregates) to hundreds of astronomical units (the size of the turbulent protoplanetary nebula). Considering these processes simultaneously is essential when studying planetesimal formation. Aims: The goal of this work is to quantify where and when planetesimal formation can occur as the result of porous coagulation of icy grains and to understand how the process is influenced by the properties of the protoplanetary disk. Methods: We develop a novel, global, semi-analytical model for the evolution of the mass-dominating dust particles in a turbulent protoplanetary disk that takes into account the evolution of the dust surface density while preserving the essential characteristics of the porous coagulation process. This panoptic model is used to study the growth from sub-micron to planetesimal sizes in disks around Sun-like stars. Results: For highly porous ices, unaffected by collisional fragmentation and erosion, rapid growth to planetesimal sizes is possible in a zone stretching out to ~10 AU for massive disks. When porous coagulation is limited by erosive collisions, the formation of planetesimals through direct coagulation is not possible, but the creation of a large population of aggregates with Stokes numbers close to unity might trigger the streaming instability (SI). However, we find that reaching conditions necessary for SI is difficult and limited to dust-rich disks, (very) cold disks, or disks with weak turbulence. Conclusions: Behind the snow-line, porosity-driven aggregation of icy grains results in rapid (~104 yr) formation of planetesimals. If erosive collisions prevent this, SI might be triggered for specific disk conditions. The numerical approach introduced in this work is ideally suited for studying planetesimal formation and pebble delivery simultaneously and will help build a coherent

  8. Ceramic stove

    SciTech Connect

    Goetz, M.

    1984-12-24

    A ceramic stove that may be supplied in kit form includes a base frame, a cast iron firebox secured on the base frame, a top frame attached to and surrounding the top of the firebox, and ceramic panels extending between and held by the frames in spaced relation from the firebox. The ceramic panels are ''ship-lapped'' relative to each other and are not cemented or otherwise positively attached to each other. Logs may be fed as fuel into the fire box door from one side of the stove allowing longer logs to be burned. The logs rest on a grate which includes a ''shakable'' portion for shaking ashes onto an ash pan located below the grate. A separate, small door into the firebox is provided for starting the fire and that door is covered by another, safety door which also closes the scape through whic the ash pan is removed for emptying. An outer screen gate is provided to overlie the firebox doors and the entire side of the firebos. Products of combustion rise in the firebox and are guided by a baffle in a desired serpentine path prolonging their containment, until they reach an outlet at the top of the fire box where they are then carried downwardly by a flue formed in part by a portion of the back wall of the firebox. A heat shield covers the back wall of the firebox including the flue whose outlet extends through the heat shield at mid elevation. Other features and advantages are also disclosed.

  9. Monolithic ceramics

    NASA Technical Reports Server (NTRS)

    Herbell, Thomas P.; Sanders, William A.

    1992-01-01

    A development history and current development status evaluation are presented for SiC and Si3N4 monolithic ceramics. In the absence of widely sought improvements in these materials' toughness, and associated reliability in structural applications, uses will remain restricted to components in noncritical, nonman-rated aerospace applications such as cruise missile and drone gas turbine engine components. In such high temperature engine-section components, projected costs lie below those associated with superalloy-based short-life/expendable engines. Advancements are required in processing technology for the sake of fewer and smaller microstructural flaws.

  10. The giant Pebble Cu-Au-Mo deposit and surrounding region, southwest Alaska: introduction

    USGS Publications Warehouse

    Kelley, Karen D.; Lang, James R.; Eppinger, Robert G.

    2013-01-01

    The Pebble deposit is located about 320 km southwest of and 27 km northwest of the village of Iliamna in Alaska (Fig. 1A). It is one of the largest porphyry deposits in terms of contained Cu (Fig. 2A) and it has the largest Au endowment of any porphyry deposit in the world (Fig. 2B). The deposit comprises the Pebble West and Pebble East zones that represent two coeval hydrothermal centers within a single system (Lang et al., 2013). Together the measured and indicated resources total 5,942 million metric tons (Mt) at 0.42% Cu, 0.35 g/t Au, and 250 ppm Mo with an inferred resource of 4,835 Mt at 0.24% Cu, 0.26 g/t Au, and 215 ppm Mo. In addition, the deposit contains significant concentrations of Ag, Pd, and Re (Northern Dynasty Minerals, 2011).

  11. Pebble Accretion Rates for Planetesimals: Hydrodynamics Calculations with Direct Particle Integration

    NASA Astrophysics Data System (ADS)

    Hughes, Anna; Boley, Aaron

    2015-12-01

    The formation and growth of planetesimals are fundamental to planet building. However, in our understanding of planet formation, there are a number of processes that limit the formation of planetesimals such as particle bouncing, fragmentation, and inward radial drift due to gas drag. Such processes seemingly make growth beyond mm to cm sizes difficult. In this case, the protoplanetary disk may become rich in pebble-sized solids as opposed to km-sized planetesimals. If a small number of large planetesimals do manage to form, then gas-drag effects can allow those seeds to efficiently accrete the abundant pebbles from the nebula and grow to planet sizes. We present self-consistent hydrodynamic simulations with direct particle integration and gas-drag coupling to evaluate the rate of planetesimal growth due to pebble accretion. We explore a range of particle sizes and nebular conditions using wind tunnel numerical experiments.

  12. Challenges in forming the solar system's giant planet cores via pebble accretion

    SciTech Connect

    Kretke, K. A.; Levison, H. F.

    2014-12-01

    Though ∼10 M {sub ⊕} mass rocky/icy cores are commonly held as a prerequisite for the formation of gas giants, theoretical models still struggle to explain how these embryos can form within the lifetimes of gaseous circumstellar disks. In recent years, aerodynamic-aided accretion of 'pebbles', objects ranging from centimeters to meters in size, has been suggested as a potential solution to this long-standing problem. While pebble accretion has been demonstrated to be extremely effective in local simulations that look at the detailed behavior of these pebbles in the vicinity of a single planetary embryo, to date there have been no global simulations demonstrating the effectiveness of pebble accretion in a more complicated, multi-planet environment. Therefore, we have incorporated the aerodynamic-aided accretion physics into LIPAD, a Lagrangian code that can follow the collisional/accretional/dynamical evolution of a protoplanetary system, to investigate how pebble accretion manifests itself in the larger planet formation picture. We find that under generic circumstances, pebble accretion naturally leads to an 'oligarchic' type of growth in which a large number of planetesimals grow to similar-sized planets. In particular, our simulations tend to form hundreds of Mars- and Earth-mass objects between 4 and 10 AU. While merging of some oligarchs may grow massive enough to form giant planet cores, leftover oligarchs lead to planetary systems that cannot be consistent with our own solar system. We investigate various ideas presented in the literature (including evaporation fronts and planet traps) and find that none easily overcome this tendency toward oligarchic growth.

  13. Pebble shale (Early Cretaceous) depositional environments in National Petroleum Reserve in Alaska (NPRA)

    SciTech Connect

    Blanchard, D.C.; Tailleur, I.L.

    1983-03-01

    A pebble shale of Lower Cretaceous age occurs across the North Slope and continues into northwestern Canada. This organic shale (1 to 5% organic carbon) is possibly the source for the Prudhoe Bay hydrocarbons and includes localized well-developed sand bodies such as those in the giant Kuparuk oil field. The inferred rifting of the Arctic basin, subsequent subsidence of a northern source area, and the southern orogeny during the Late Jurassic and Early Cretaceous contributed to the unique lithology and regional setting of the pebble shale. Overlying the uppermost unconformity on the Barrow arch a pebbly mudstone 3 to 8-m (10 to 26 ft) thick, of Hauterivian-Barremian age contains well-rounded sand grains, pebbles and cobbles, pelletal glaunconite, shell fragments, wood chips, and burrows. The pebbly mudstone facies, derived from a northerly source, is interpreted as a lowstand and subaqueous delta environment formed as the northern provenance was uplifted during Valanginian time. Rapid subsidence of this basin margin was related to the inferred Atlantic margin type downfaulting north of the Barrow arch. The subsequent deposits produced a blanket of sediment 300,000 mi/sup 2/ (482,700 km/sup 2/) in areal extent. This (2 to 9 ft, 0.8 m), fine-grained sands occur within the pebble shale of the Barremian silty shale facies and are restricted to the Barrow area. These sands have an average combined thickness of 45 ft (15 m) and contain traces of oil. Paleogeographic considerations imply better reservoir and coalescing of these sands to the north toward the paleoshoreline and suggest potential for discovery of hydrocarbon reserves from drilling locations on the northern barrier island systems and offshore.

  14. 7 CFR 3201.15 - Bedding, bed linens, and towels.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 15 2012-01-01 2012-01-01 false Bedding, bed linens, and towels. 3201.15 Section 3201... PROCUREMENT Designated Items § 3201.15 Bedding, bed linens, and towels. (a) Definition. (1) Bedding is that..., bedspreads, comforters, and quilts. (2) Bed linens are woven cloth sheets and pillowcases used in bedding....

  15. 7 CFR 3201.15 - Bedding, bed linens, and towels.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 15 2013-01-01 2013-01-01 false Bedding, bed linens, and towels. 3201.15 Section 3201... PROCUREMENT Designated Items § 3201.15 Bedding, bed linens, and towels. (a) Definition. (1) Bedding is that..., bedspreads, comforters, and quilts. (2) Bed linens are woven cloth sheets and pillowcases used in bedding....

  16. 7 CFR 2902.15 - Bedding, bed linens, and towels.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 15 2010-01-01 2010-01-01 false Bedding, bed linens, and towels. 2902.15 Section 2902... PROCUREMENT Designated Items § 2902.15 Bedding, bed linens, and towels. (a) Definition. (1) Bedding is that..., bedspreads, comforters, and quilts. (2) Bed linens are woven cloth sheets and pillowcases used in bedding....

  17. 7 CFR 2902.15 - Bedding, bed linens, and towels.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 15 2011-01-01 2011-01-01 false Bedding, bed linens, and towels. 2902.15 Section 2902... PROCUREMENT Designated Items § 2902.15 Bedding, bed linens, and towels. (a) Definition. (1) Bedding is that..., bedspreads, comforters, and quilts. (2) Bed linens are woven cloth sheets and pillowcases used in bedding....

  18. 7 CFR 3201.15 - Bedding, bed linens, and towels.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 15 2014-01-01 2014-01-01 false Bedding, bed linens, and towels. 3201.15 Section 3201... PROCUREMENT Designated Items § 3201.15 Bedding, bed linens, and towels. (a) Definition. (1) Bedding is that..., bedspreads, comforters, and quilts. (2) Bed linens are woven cloth sheets and pillowcases used in bedding....

  19. Environmental durability of ceramics and ceramic composites

    NASA Technical Reports Server (NTRS)

    Fox, Dennis S.

    1992-01-01

    An account is given of the current understanding of the environmental durability of both monolithic ceramics and ceramic-matrix composites, with a view to the prospective development of methods for the characterization, prediction, and improvement of ceramics' environmental durability. Attention is given to the environmental degradation behaviors of SiC, Si3N4, Al2O3, and glass-ceramic matrix compositions. The focus of corrosion prevention in Si-based ceramics such as SiC and Si3N4 is on the high and low sulfur fuel combustion-product effects encountered in heat engine applications of these ceramics; sintering additives and raw material impurities are noted to play a decisive role in ceramics' high temperature environmental response.

  20. Bed disturbance patterns in two mediterranean impounded rivers

    NASA Astrophysics Data System (ADS)

    Lobera, Gemma; López-Tarazón, José A.; Vericat, Damià; Batalla, Ramon J.; Andrés-Doménech, Ignacio; Millán-Romero, Pedro; Vallés, Francisco

    2015-04-01

    ) characterisation of grain size distribution by means of pebble counts and bulk samples; 4) bed mobility by tracers (i.e. painted bed areas and tagged particles using radiofrequency techniques).

  1. Hybrid fluidized bed combuster

    DOEpatents

    Kantesaria, Prabhudas P.; Matthews, Francis T.

    1982-01-01

    A first atmospheric bubbling fluidized bed furnace is combined with a second turbulent, circulating fluidized bed furnace to produce heat efficiently from crushed solid fuel. The bed of the second furnace receives the smaller sizes of crushed solid fuel, unreacted limestone from the first bed, and elutriated solids extracted from the flu gases of the first bed. The two-stage combustion of crushed solid fuel provides a system with an efficiency greater than available with use of a single furnace of a fluidized bed.

  2. Moving Granular Bed Filter Development Program

    SciTech Connect

    Wilson, K.B.; Haas, J.C.; Eshelman, M.B.

    1992-01-01

    The granular bed filter was developed through low pressure, high temperature (1600[degrees]F) testing in the late 1970's and early 1980's'. Collection efficiencies over 99% were obtained. In 1988, high pressure, high temperature testing was completed at New York University, Westbury, N.Y., utilizing a coal-fired pressurized, fluidized bed combustor. High particulate removal efficiencies were confirmed as it was shown that both New Source Performance Standards and turbine tolerance limits could be met. The early scale-up work of the granular bed filter indicated potential limitations due to size, cost, and mechanical complexity. These limitations were addressed in the present program by utilizing the information gained from the filter development up through the NYU test program to reassess the commercial approach. Two studies were chosen for developing conceptual designs and cost estimates of the commercial sized filters. One is the economic study of the 250 MWe, second generation pressurized fluidized bed combustion plant defined by Foster Wheeler. This plant originally included cross-flow filters for hot gas cleanup. The other plant under study is a 100 MWe, airblown KRW gasifier. A cross-flow inter was utilized for gas stream cleanup in this study also. Granular bed and ceramic candle filters were substituted for the cross-flow filters in both these plants, and the resulting cost of electricity (COE) is compared.

  3. Moving Granular Bed Filter Development Program

    SciTech Connect

    Wilson, K.B.; Haas, J.C.; Eshelman, M.B.

    1992-11-01

    The granular bed filter was developed through low pressure, high temperature (1600{degrees}F) testing in the late 1970`s and early 1980`s`. Collection efficiencies over 99% were obtained. In 1988, high pressure, high temperature testing was completed at New York University, Westbury, N.Y., utilizing a coal-fired pressurized, fluidized bed combustor. High particulate removal efficiencies were confirmed as it was shown that both New Source Performance Standards and turbine tolerance limits could be met. The early scale-up work of the granular bed filter indicated potential limitations due to size, cost, and mechanical complexity. These limitations were addressed in the present program by utilizing the information gained from the filter development up through the NYU test program to reassess the commercial approach. Two studies were chosen for developing conceptual designs and cost estimates of the commercial sized filters. One is the economic study of the 250 MWe, second generation pressurized fluidized bed combustion plant defined by Foster Wheeler. This plant originally included cross-flow filters for hot gas cleanup. The other plant under study is a 100 MWe, airblown KRW gasifier. A cross-flow inter was utilized for gas stream cleanup in this study also. Granular bed and ceramic candle filters were substituted for the cross-flow filters in both these plants, and the resulting cost of electricity (COE) is compared.

  4. Bed material agglomeration during fluidized bed combustion

    SciTech Connect

    Brown, R.C.; Dawson, M.R.; Noble, S.

    1993-02-01

    The purpose of this project is to determine the physical and chemical reactions which led to the undesired agglomeration of bed material during fluidized bed combustion and to relate these reactions to specific causes. Survey of industrial-scale fluidized bed combustors is being conducted to determine the occurrence of bed agglomeration and the circumstances under which agglomeration took place. This task should be finished by the end of February. Samples of bed material, agglomerate material, and boiler deposits are being requested from boiler operators as part of the survey. Once received, these sample will be analyzed to determine chemical and mineralogic composition. The bulk chemical determination will be performed using x-ray fluorescence and inductively coupled plasma-optical emission (ICP). Mineralogy will be detected by x-ray diffraction (XRD). Chemical and mineral reactions will be determined by scanning electron microscopy, optical microscopy, and electron microprobe.

  5. Practice Hospital Bed Safety

    MedlinePlus

    ... Bed? Todd says that there is no standard definition for hospital beds, a fact that consumers shopping ... in retail stores that don’t meet the definition of medical devices under the law, but which ...

  6. Fluidized bed combustion

    SciTech Connect

    Sowards, N.K.; Murphy, M.L.

    1992-04-07

    This patent describes a method of incinerating a fuel containing difficult to remove tramp comprising wire. It comprises placing of a fluid bed within a downwardly and inwardly tapered centrally hollow air distributor disposed within a lower portion of a vessel; introducing fuel comprising combustible material and tramp comprising wire into the fluid bed; incinerating the combustible material in the fluid bed accommodating downward migration within the fluid bed of the wire without a central obstruction to such migration; in the course of performing the incinerating step, fluidizing the bed solely by introducing inwardly at several tiered locations directed air into the bed only around the tapered periphery along the lower portion of the vessel from a plurality of inwardly and downwardly parallel sites as causing the bed material and tramp to migrate downwardly and inwardly without central bed obstruction toward a discharge site.

  7. Enuresis (Bed-Wetting)

    MedlinePlus

    ... their development. Bed-wetting is more common among boys than girls. What causes bed-wetting? A number of things ... valves in boys or in the ureter in girls or boys Abnormalities in the spinal cord A small bladder ...

  8. Catalyst functionalized buffer sorbent pebbles for rapid separation of carbon dioxide from gas mixtures

    SciTech Connect

    Aines, Roger D

    2015-03-31

    A method for separating CO.sub.2 from gas mixtures uses a slurried media impregnated with buffer compounds and coating the solid media with a catalyst or enzyme that promotes the transformation of CO.sub.2 to carbonic acid. Buffer sorbent pebbles with a catalyst or enzyme coating are provided for rapid separation of CO.sub.2 from gas mixtures.

  9. Catalyst functionalized buffer sorbent pebbles for rapid separation of carbon dioxide from gas mixtures

    DOEpatents

    Aines, Roger D.

    2013-03-12

    A method for separating CO.sub.2 from gas mixtures uses a slurried media impregnated with buffer compounds and coating the solid media with a catalyst or enzyme that promotes the transformation of CO.sub.2 to carbonic acid. Buffer sorbent pebbles with a catalyst or enzyme coating are provided for rapid separation of CO.sub.2 from gas mixtures.

  10. Nanoparticle PEBBLE Sensors for Quantitative Nanomolar Imaging of Intracellular Free Calcium Ions

    PubMed Central

    Si, Di; Epstein, Tamir; Lee, Yong-Eun Koo; Kopelman, Raoul

    2011-01-01

    Ca2+ is a universal second messenger and plays a major role in intracellular signaling, metabolism and a wide range of cellular processes. To date, one of the most successful approaches for intracellular Ca2+ measurement involves introduction of optically sensitive Ca2+ indicators into living cells, combined with digital imaging microscopy. However, the use of free Ca2+ indicators for intracellular sensing and imaging has several limitations, such as nonratiometric measurement for the most sensitive indicators, cytotoxicity of the indicators, interference from non-specific binding caused by cellular biomacromolecules, challenging calibration and unwanted sequestration of the indicator molecules. These problems are minimized when the Ca2+ indicators are encapsulated inside porous and inert polyacrylamide nanoparticles. We present PEBBLE nanosensors encapsulated with rhodamine based Ca2+ fluorescence indicators. The here presented rhod-2 containing PEBBLEs show a stable sensing range at near-neutral pH (pH 6–9). Due to the protection of the PEBBLE matrix, the interference of protein non-specific binding to the indicator is minimal. The rhod-2 PEBBLEs give a nanomolar dynamic sensing range for both in-solution (Kd = 478 nM) and intracellular (Kd = 293 nM) measurements. These nanosensors are a useful quantitative tool for the measurement and imaging of the cytosolic nanomolar free Ca2+ levels. PMID:22122409

  11. Thermal ramp tritium release in COBRA-1A2 C03 beryllium pebbles

    SciTech Connect

    Baldwin, D.L.

    1998-03-01

    Tritium release kinetics, using the method of thermal ramp heating at three linear ramp rates, were measured on the COBRA-1A2 C03 1-mm beryllium pebbles. This report includes a brief discussion of the test, and the test data in graph format.

  12. Growing Pebbles and Conceptual Prisms - Understanding the Source of Student Misconceptions about Rock Formation.

    ERIC Educational Resources Information Center

    Kusnick, Judi

    2002-01-01

    Analyzes narrative essays--stories of rock formation--written by pre-service elementary school teachers. Reports startling misconceptions among preservice teachers on pebbles that grow, human involvement in rock formation, and sedimentary rocks forming as puddles as dry up, even though these students had completed a college level course on Earth…

  13. The impact of ellipsoidal particle shape on pebble breakage in gravel

    PubMed Central

    Tuitz, Christoph; Exner, Ulrike; Frehner, Marcel; Grasemann, Bernhard

    2012-01-01

    We have studied the influence of particle shape and consequently loading configuration on the breakage load of fluvial pebbles. Unfortunately, physical strength tests on pebbles, i.e., point-load tests, can only be conducted under one specific stable loading configuration. Therefore, the physical uniaxial strength tests performed in this study were extended by a two-dimensional finite-element stress analysis, which is capable of investigating those scenarios that are not possible in physical tests. Breakage load, equivalent to that measured in unidirectional physical tests, was determined from the results of the stress analysis by a maximum tensile stress-based failure criterion. Using this assumption, allows the determination of breakage load for a range of different kind of synthetic loading configurations and its comparison with the natural breakage load distribution of the physical strength tests. The results of numerical modelling indicated that the configuration that required the least breakage load corresponded with the minor principal axis of the ellipsoidal pebbles. In addition, most of the simulated gravel-hosted loading configurations exceeded the natural breakage load distribution of fluvial pebbles obtained from the physical strength tests. PMID:26321870

  14. Time for Bed Game

    MedlinePlus

    ... a Friend Who Cuts? Babysitting: Time for Bed Game KidsHealth > For Teens > Babysitting: Time for Bed Game Print A A A Text Size What Kids ... kids to bed can be tough sometimes! This game introduces children to the concept of getting enough ...

  15. Making a Bed

    ERIC Educational Resources Information Center

    Wexler, Anthony; Stein, Sherman

    2005-01-01

    The origins of this paper lay in making beds by putting pieces of plywood on a frame: If beds need to be 4 feet 6 inches by 6 feet 3 inches, and plywood comes in 4-foot by 8-foot sheets, how should one cut the plywood to minimize waste (and have stable beds)? The problem is of course generalized.

  16. Fluidized bed quenching technology

    SciTech Connect

    Reynoldson, R.

    1996-12-31

    The use of fluidized beds for quenching ferrous materials is outlined and compared with the more traditional techniques commonly used in the heat treatment industry. The use of fluidized bed quenching to control distortion of metal parts is also discussed. A case study is provided to illustrate a practical application of fluidized bed quenching.

  17. On the water delivery to terrestrial embryos by ice pebble accretion

    NASA Astrophysics Data System (ADS)

    Sato, Takao; Okuzumi, Satoshi; Ida, Shigeru

    2016-04-01

    Standard accretion disk models suggest that the snow line in the solar nebula migrated interior to the Earth's orbit in a late stage of nebula evolution. In this late stage, a significant amount of ice could have been delivered to 1 AU from outer regions in the form of mm to dm-sized pebbles. This raises the question why the present Earth is so depleted of water (with the ocean mass being as small as 0.023% of the Earth mass). Here we quantify the amount of icy pebbles accreted by terrestrial embryos after the migration of the snow line assuming that no mechanism halts the pebble flow in outer disk regions. We use a simplified version of the coagulation equation to calculate the formation and radial inward drift of icy pebbles in a protoplanetary disk. The pebble accretion cross section of an embryo is calculated using analytic expressions presented by recent studies. We find that the final mass and water content of terrestrial embryos strongly depends on the radial extent of the gas disk, the strength of disk turbulence, and the time at which the snow lines arrives at 1 AU. The disk's radial extent sets the lifetime of the pebble flow, while turbulence determines the density of pebbles at the midplane where the embryos reside. We find that the final water content of the embryos falls below 0.023 wt% only if the disk is compact (<100 AU), turbulence is strong at 1 AU, and the snow line arrives at 1 AU later than 2-4 Myr after disk formation. If the solar nebula extended to 300 AU, initially rocky embryos would have evolved into icy planets of 1-10 Earth masses unless the snow-line migration was slow. If the proto-Earth contained water of ~1 wt% as might be suggested by the density deficit of the Earth's outer core, the formation of the proto-Earth was possible with weaker turbulence and with earlier (>0.5-2 Myr) snow-line migration.

  18. On the water delivery to terrestrial embryos by ice pebble accretion

    NASA Astrophysics Data System (ADS)

    Sato, Takao; Okuzumi, Satoshi; Ida, Shigeru

    2016-05-01

    Standard accretion disk models suggest that the snow line in the solar nebula migrated interior to the Earth's orbit in a late stage of nebula evolution. In this late stage, a significant amount of ice could have been delivered to 1 AU from outer regions in the form of mm to dm-sized pebbles. This raises the question why the present Earth is so depleted of water (with the ocean mass being as small as 0.023% of the Earth mass). Here we quantify the amount of icy pebbles accreted by terrestrial embryos after the migration of the snow line assuming that no mechanism halts the pebble flow in outer disk regions. We use a simplified version of the coagulation equation to calculate the formation and radial inward drift of icy pebbles in a protoplanetary disk. The pebble accretion cross section of an embryo is calculated using analytic expressions presented by recent studies. We find that the final mass and water content of terrestrial embryos strongly depends on the radial extent of the gas disk, the strength of disk turbulence, and the time at which the snow lines arrives at 1 AU. The disk's radial extent sets the lifetime of the pebble flow, while turbulence determines the density of pebbles at the midplane where the embryos reside. We find that the final water content of the embryos falls below 0.023 wt% only if the disk is compact (<100 AU), turbulence is strong at 1 AU, and the snow line arrives at 1 AU later than 2-4 Myr after disk formation. If the solar nebula extended to 300 AU, initially rocky embryos would have evolved into icy planets of 1-10 Earth masses unless the snow-line migration was slow. If the proto-Earth contained water of ~1 wt% as might be suggested by the density deficit of the Earth's outer core, the formation of the proto-Earth was possible with weaker turbulence and with earlier (>0.5-2 Myr) snow-line migration.

  19. Dental ceramics: An update

    PubMed Central

    Shenoy, Arvind; Shenoy, Nina

    2010-01-01

    In the last few decades, there have been tremendous advances in the mechanical properties and methods of fabrication of ceramic materials. While porcelain-based materials are still a major component of the market, there have been moves to replace metal ceramics systems with all ceramic systems. Advances in bonding techniques have increased the range and scope for use of ceramics in dentistry. In this brief review, we will discuss advances in ceramic materials and fabrication techniques. Examples of the microstructure property relationships for these ceramic materials will also be addressed. PMID:21217946

  20. Ceramic inspection system

    DOEpatents

    Werve, Michael E.

    2006-05-16

    A system for inspecting a ceramic component. The ceramic component is positioned on a first rotary table. The first rotary table rotates the ceramic component. Light is directed toward the first rotary table and the rotating ceramic component. A detector is located on a second rotary table. The second rotary table is operably connected to the first rotary table and the rotating ceramic component. The second rotary table is used to move the detector at an angle to the first rotary table and the rotating ceramic component.

  1. Growing the gas-giant planets by the gradual accumulation of pebbles.

    PubMed

    Levison, Harold F; Kretke, Katherine A; Duncan, Martin J

    2015-08-20

    It is widely held that the first step in forming gas-giant planets, such as Jupiter and Saturn, was the production of solid 'cores' each with a mass roughly ten times that of the Earth. Getting the cores to form before the solar nebula dissipates (in about one to ten million years; ref. 3) has been a major challenge for planet formation models. Recently models have emerged in which 'pebbles' (centimetre-to-metre-sized objects) are first concentrated by aerodynamic drag and then gravitationally collapse to form objects 100 to 1,000 kilometres in size. These 'planetesimals' can then efficiently accrete left-over pebbles and directly form the cores of giant planets. This model is known as 'pebble accretion'; theoretically, it can produce cores of ten Earth masses in only a few thousand years. Unfortunately, full simulations of this process show that, rather than creating a few such cores, it produces a population of hundreds of Earth-mass objects that are inconsistent with the structure of the Solar System. Here we report that this difficulty can be overcome if pebbles form slowly enough to allow the planetesimals to gravitationally interact with one another. In this situation, the largest planetesimals have time to scatter their smaller siblings out of the disk of pebbles, thereby stifling their growth. Our models show that, for a large and physically reasonable region of parameter space, this typically leads to the formation of one to four gas giants between 5 and 15 astronomical units from the Sun, in agreement with the observed structure of the Solar System. PMID:26289203

  2. The growth of planets by pebble accretion in evolving protoplanetary discs

    NASA Astrophysics Data System (ADS)

    Bitsch, Bertram; Lambrechts, Michiel; Johansen, Anders

    2015-10-01

    The formation of planets depends on the underlying protoplanetary disc structure, which in turn influences both the accretion and migration rates of embedded planets. The disc itself evolves on time scales of several Myr, during which both temperature and density profiles change as matter accretes onto the central star. Here we used a detailed model of an evolving disc to determine the growth of planets by pebble accretion and their migration through the disc. Cores that reach their pebble isolation mass accrete gas to finally form giant planets with extensive gas envelopes, while planets that do not reach pebble isolation mass are stranded as ice giants and ice planets containing only minor amounts of gas in their envelopes. Unlike earlier population synthesis models, our model works without any artificial reductions in migration speed and for protoplanetary discs with gas and dust column densities similar to those inferred from observations. We find that in our nominal disc model, the emergence of planetary embryos preferably should occur after approximately 2 Myr in order to not exclusively form gas giants, but also ice giants and smaller planets. The high pebble accretion rates ensure that critical core masses for gas accretion can be reached at all orbital distances. Gas giant planets nevertheless experience significant reduction in semi-major axes by migration. Considering instead planetesimal accretion for planetary growth, we show that formation time scales are too long to compete with the migration time scales and the dissipation time of the protoplanetary disc. All in all, we find that pebble accretion overcomes many of the challenges in the formation of ice and gas giants in evolving protoplanetary discs. Appendices are available in electronic form at http://www.aanda.org

  3. Growing the gas-giant planets by the gradual accumulation of pebbles

    NASA Astrophysics Data System (ADS)

    Levison, Harold F.; Kretke, Katherine A.; Duncan, Martin J.

    2015-08-01

    It is widely held that the first step in forming gas-giant planets, such as Jupiter and Saturn, was the production of solid `cores' each with a mass roughly ten times that of the Earth. Getting the cores to form before the solar nebula dissipates (in about one to ten million years; ref. 3) has been a major challenge for planet formation models. Recently models have emerged in which `pebbles' (centimetre-to-metre-sized objects) are first concentrated by aerodynamic drag and then gravitationally collapse to form objects 100 to 1,000 kilometres in size. These `planetesimals' can then efficiently accrete left-over pebbles and directly form the cores of giant planets. This model is known as `pebble accretion' theoretically, it can produce cores of ten Earth masses in only a few thousand years. Unfortunately, full simulations of this process show that, rather than creating a few such cores, it produces a population of hundreds of Earth-mass objects that are inconsistent with the structure of the Solar System. Here we report that this difficulty can be overcome if pebbles form slowly enough to allow the planetesimals to gravitationally interact with one another. In this situation, the largest planetesimals have time to scatter their smaller siblings out of the disk of pebbles, thereby stifling their growth. Our models show that, for a large and physically reasonable region of parameter space, this typically leads to the formation of one to four gas giants between 5 and 15 astronomical units from the Sun, in agreement with the observed structure of the Solar System.

  4. Getting Rid of Bed Bugs

    MedlinePlus

    ... Bed Bugs — Do-it-yourself Bed Bug Control — Pesticides to Control Bed Bugs Bed Bug Information Clearinghouse ... Greener Living Health and Safety Land and Cleanup Pesticides Waste Water Science & Technology Air Climate Change Ecosystems ...

  5. Joining Ceramics By Brazing

    NASA Technical Reports Server (NTRS)

    Chiaramonte, Francis P.; Sudsina, Michael W.

    1992-01-01

    Certain ceramic materials tightly bond together by brazing with suitable alloys. Enables fabrication of parts of wide variety of shapes from smaller initial pieces of ceramics produced directly in only limited variety of shapes.

  6. Ceramic electrolyte coating methods

    DOEpatents

    Seabaugh, Matthew M.; Swartz, Scott L.; Dawson, William J.; McCormick, Buddy E.

    2004-10-12

    Processes for preparing aqueous suspensions of a nanoscale ceramic electrolyte material such as yttrium-stabilized zirconia. The invention also includes a process for preparing an aqueous coating slurry of a nanoscale ceramic electrolyte material. The invention further includes a process for depositing an aqueous spray coating slurry including a ceramic electrolyte material on pre-sintered, partially sintered, and unsintered ceramic substrates and products made by this process.

  7. Westinghouse standleg moving granular bed filter development program

    SciTech Connect

    Newby, R.A.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.

    1994-10-01

    Advanced, coal-based, power plants, such as IGCC and Advanced-PFBC, are currently nearing commercial demonstration. These power plant technologies require hot gas filtration as part of their gas cleaning trains. Ceramic barrier filters are the major filter candidates being developed for these hot gas cleaning applications. While ceramic barrier filters achieve high levels of particle removal, there are concerns for their reliability and operability. An alternative hot gas filtration technology is the moving granular bed filter. These systems are at a lower state of development than ceramic barrier filters, and their effectiveness as filters is still in question. Their apparent attributes, result from their much less severe mechanical design and materials constraints, and the potential for more reliable, failure-free particle removal operation. The standleg moving granular-bed filter (SMGBF) system, is a compact unit that uses cocurrent gas-pellet contacting in an arrangement that greatly simplifies and enhances the distribution of dirty, process gas to the moving bed and allows effective disengagement of clean gas from the moving bed. This paper describes the equipment and process test results.

  8. Brittleness of ceramics

    NASA Technical Reports Server (NTRS)

    Kroupa, F.

    1984-01-01

    The main characteristics of mechanical properties of ceramics are summarized and the causes of their brittleness, especially the limited mobility of dislocations, are discussed. The possibility of improving the fracture toughness of ceramics and the basic research needs relating to technology, structure and mechanical properties of ceramics are stressed in connection with their possible applications in engineering at high temperature.

  9. Ceramic to metal seal

    DOEpatents

    Snow, Gary S.; Wilcox, Paul D.

    1976-01-01

    Providing a high strength, hermetic ceramic to metal seal by essentially heating a wire-like metal gasket and a ceramic member, which have been chemically cleaned, while simultaneously deforming from about 50 to 95 percent the metal gasket against the ceramic member at a temperature of about 30 to 75 percent of the melting temperature of the metal gasket.

  10. Gas dynamics and heat transfer in a packed pebble-bed reactor for the 4th generation nuclear energy

    NASA Astrophysics Data System (ADS)

    Abdulmohsin, Rahman

    For over three decades, the presence of magnetic flux noise with a power spectral density scaling roughly as S phi ( f) ∝ 1/falpha where a≲1, has been known to limit the low-frequency performance of dc superconducting quantum interference devices (SQUIDs). In recent years, experiments indicate that this same noise persists to frequencies up to 1 GHz and is a dominant source of dephasing in flux-sensitive superconducting quantum bits (qubits). Thus, the reduction of flux noise presents a major hurdle towards the successful realization of scalable quantum computers that are based on flux-based qubits. In this thesis, we present experimental measurements, theoretical analyses, and numerical simulations that support a more detailed understanding of both the microscopic and macroscopic properties of flux n. Our experimental work begins with flux noise measurements of a large number of SQUIDs in the temperature range from 0.1 K to 4 K. We report on measurements of ten SQUIDs with systematically varied geometries and show that alpha increases as the temperature is lowered; in so doing, each spectrum pivots about a nearly constant frequency. The mean square flux noise, inferred by integrating the power spectra, grows rapidly with temperature and at a given temperature is approximately independent of the outer dimension of a given SQUID washer. We show that these results are incompatible with a model based on the random reversal of independent, spins that are located at the surface of the SQUID washer. In the course of our flux noise measurements, we became aware of a spurious contribution to low-frequency critical current noise in Josephson junctions normally attributed to charge trapping in the barrier arising from temperature instabilities inherent in cryogenic systems. These temperature fluctuations modify the critical current via its temperature dependence. By computing cross-correlations between measured temperature and critical current noise in Al-AlOx-Al junctions, we show that, despite excellent temperature stability, temperature fluctuations induce observable critical current fluctuations. Particularly, becuase 1/ f critical current noise has decreased with improved fabrication techniques in recent years, it is important to understand and eliminate this additional noise source. Next, we introduce a numerical method of calculating the mean square flux noise F2 from independently fluctuating spins on the surface of thin-film loops of arbitrary geometry. By reciprocity, F2 is proportional to Br2 , where B(r) is the magnetic field generated by a circulating current around the loop and r varies over the loop surface. By discretizing the loop nonuniformly, we efficiently and accurately compute the current distribution and resulting magnetic field, which may vary rapidly across the loop. We use this method to compute F2 in a number of scenarios in which we systematically vary physical parameters of the loop. We compare our simulations to an earlier analytic result predicting that F2 ∝ R/W in the limit where the loop radius R is much greater than the linewidth W. We further show that the previously neglected contribution of edge spins to F2 is significant---even dominant---in narrow-linewidth loops. To calculate theoretical dephasing rates in qubits, we consider flux noise with a spectral density Sphi( f) = A2/ (f/1 Hz) alpha, where A is of the order of 1 muphi 0 Hz--1/2 and 0.6 ≤ alpha ≤ 1.2; applied flux, our calculations of the dependence of the pure dephasing time tau φ Ramsey and echo pulse sequences on alpha for fixed A show that tauφ decreases rapidly as alpha is reduced. We find that tauφ is relatively insensitive to the noise bandwidth, f1 ≤ f ≤ f2 for all alpha provided the ultraviolet cutoff frequency f2 > 1/tauφ. We calculate the ratio tauφ,E/tau φ, R of the echo (E) and Ramsey (R) sequences, and the dependence of the decay function on alpha and f2. We investigate the case in which S phi(f0) is fixed at the "pivot frequency" f0 ≠ 1 Hz while alpha is varied, and find that the choice of f 0 can greatly influence the sensitivity of tauφ, E and tauφ, R to the value of alpha. Finally, we conclude with a brief review of our principal results and conclusions. We also comment on promising avenues of future research.

  11. Uncovering East Antarctic Bedrock using detrital zircon geochronology and pebble lithologies from Mount Howe, Scott Glacier

    NASA Astrophysics Data System (ADS)

    Dits, T.; Licht, K.; Bader, N.; Kaplan, M. R.; Schaefer, J. M.; Winckler, G.

    2012-12-01

    Till from the flanks of Mount Howe, the southernmost outcrop in the world at the head of the Scott Glacier, Antarctica, offers an exclusive view of East Antarctic bedrock through analysis of detrital zircon geochronology and pebble lithology. With no outcrops upstream of the Mount Howe nunatak, detrital zircons and pebbles incorporated in the supraglacial till place direct new age and lithologic constraints on unmapped, ice covered bedrock in the Scott Glacier catchment. Nine moraine crests were sampled along a 2 km transect from the modern ice edge toward exposed Beacon Supergroup bedrock, where rock weathering increases away from the ice margin. Preliminary cosmogenic ages on boulders on the same crests as the provenance study indicate most of the moraine complex formed over the last 100 ka, but some ridges close to the headwall may be much older. Pebble lithologies across the transect show minimal statistical variation, averaging 60% mafic igneous, 30% metamorphic, and 10% sedimentary lithologies dominantly from the Ferrar and Beacon Supergroups. Observations of faceting and striations on pebble surfaces reveal that up to 40-50% of the pebble fraction of the till was subglacially transported, and a minimum of 15% are exotic lithologies. Nearly 80% of cobbles collected from a non-random survey reveal the presence of several exotic rock types, including vesicular olivine basalt, quartzite, and four different compositions of granite. Guided by backscatter electron imagery of detrital zircons, 385 ages from U-Pb isotopes of detrital zircons from 8 sequential moraine crests were determined by laser ablation-inductively coupled plasma mass spectroscopy (LA-ICPMS). Distinct age populations were identified at 185-190 Ma, 255-270 Ma, 355-365 Ma, 550-580 Ma, and 2740 Ma. Four samples in the middle of the transect all display a similar 1010-1040 Ma peak that is statistically different from the remaining samples. The 185 Ma population differs from the typical East Antarctic

  12. Thin film ceramic thermocouples

    NASA Technical Reports Server (NTRS)

    Gregory, Otto (Inventor); Fralick, Gustave (Inventor); Wrbanek, John (Inventor); You, Tao (Inventor)

    2011-01-01

    A thin film ceramic thermocouple (10) having two ceramic thermocouple (12, 14) that are in contact with each other in at least on point to form a junction, and wherein each element was prepared in a different oxygen/nitrogen/argon plasma. Since each element is prepared under different plasma conditions, they have different electrical conductivity and different charge carrier concentration. The thin film thermocouple (10) can be transparent. A versatile ceramic sensor system having an RTD heat flux sensor can be combined with a thermocouple and a strain sensor to yield a multifunctional ceramic sensor array. The transparent ceramic temperature sensor that could ultimately be used for calibration of optical sensors.

  13. Ceramic gas turbine shroud

    DOEpatents

    Shi, Jun; Green, Kevin E.

    2014-07-22

    An example gas turbine engine shroud includes a first annular ceramic wall having an inner side for resisting high temperature turbine engine gasses and an outer side with a plurality of radial slots. A second annular metallic wall is positioned radially outwardly of and enclosing the first annular ceramic wall and has a plurality of tabs in communication with the slot of the first annular ceramic wall. The tabs of the second annular metallic wall and slots of the first annular ceramic wall are in communication such that the first annular ceramic wall and second annular metallic wall are affixed.

  14. Fluidized bed combustor modeling

    NASA Technical Reports Server (NTRS)

    Horio, M.; Rengarajan, P.; Krishnan, R.; Wen, C. Y.

    1977-01-01

    A general mathematical model for the prediction of performance of a fluidized bed coal combustor (FBC) is developed. The basic elements of the model consist of: (1) hydrodynamics of gas and solids in the combustor; (2) description of gas and solids contacting pattern; (3) kinetics of combustion; and (4) absorption of SO2 by limestone in the bed. The model is capable of calculating the combustion efficiency, axial bed temperature profile, carbon hold-up in the bed, oxygen and SO2 concentrations in the bubble and emulsion phases, sulfur retention efficiency and particulate carry over by elutriation. The effects of bed geometry, excess air, location of heat transfer coils in the bed, calcium to sulfur ratio in the feeds, etc. are examined. The calculated results are compared with experimental data. Agreement between the calculated results and the observed data are satisfactory in most cases. Recommendations to enhance the accuracy of prediction of the model are suggested.

  15. Fluidized bed combustion

    SciTech Connect

    Sowards, N.K.; Murphy, M.L.

    1991-10-29

    This patent describes a vessel. It comprises a fluid bed for continuously incinerating fuel comprising tire segments and the like which comprise metallic wire tramp and for concurrently removing tramp and bed materials at a bottom effluent exit means of the vessel, the vessel further comprising static air distributor means at the periphery of the bed comprising a substantially centrally unobstructed relatively large central region in which the fluid bed and fuel only are disposed and through which bed material and tramp migrate without obstruction to and through the effluent exit means, downwardly and inwardly stepped lower vessel wall means and a plurality of peripherally located centrally directed vertically and horizontally offset spaced air influent means surrounding the central region and associated with the stepped lower vessel wall means by which the bed is supported and fluidized.

  16. Fabrication and characterization of Li2TiO3 core-shell pebbles with enhanced lithium density

    NASA Astrophysics Data System (ADS)

    Hong, Ming; Zhang, Yingchun; Mi, Yingying; Xiang, Maoqiao; Zhang, Yun

    2014-02-01

    In order to increase the lithium density and control the lithium mass loss at elevated temperature, development of Li2TiO3 pebbles with excess Li is needed. In this paper, Li2TiO3 core-shell pebbles with different Li/Ti molar ratios were fabricated by a gel-casting method using Li2TiO3 and Li2CO3 as starting materials. Differential thermal analysis appending a thermogravimetric analyzer (DTA-TG) and X-ray diffraction (XRD) were employed to understand the solid-state reactions. And then the calcining and sintering processes were optimized. Microstructure, element distribution, crush load and density of the pebbles were also investigated. The experimental results showed that the pebble had a Li2TiO3-Li4TiO4 complex phase core and a tunable thickness Li2TiO3 shell, and the lithium density of the pebbles significantly increased with the increasing of the Li/Ti ratio. The optimum Li/Ti ratio was 2.7, and the pebbles displayed a good crush load (about 32 N) when sintered at 950 °C for 2 h in N2 atmosphere.

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

    SciTech Connect

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

    2009-03-16

    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.

  18. 3D inversion of SPECTREM and ZTEM airborne electromagnetic data from the Pebble Cu-Au-Mo porphyry deposit, Alaska

    NASA Astrophysics Data System (ADS)

    Pare, Pascal; Gribenko, Alexander V.; Cox, Leif H.; Čuma, Martin; Wilson, Glenn A.; Zhdanov, Michael S.; Legault, Jean; Smit, Jaco; Polome, Louis

    2012-04-01

    Geological, geochemical, and geophysical surveys have been conducted in the area of the Pebble Cu-Au-Mo porphyry deposit in south-west Alaska since 1985. This case study compares three-dimensional (3D) inversion results from Anglo American's proprietary SPECTREM 2000 fixed-wing time-domain airborne electromagnetic (AEM) and Geotech's ZTEM airborne audio-frequency magnetics (AFMAG) systems flown over the Pebble deposit. Within the commonality of their physics, 3D inversions of both SPECTREM and ZTEM recover conductivity models consistent with each other and the known geology. Both 3D inversions recover conductors coincident with alteration associated with both Pebble East and Pebble West. The high grade CuEqn 0.6% ore shell is not consistently following the high conductive trend, suggesting that the SPECTREM and ZTEM responses correspond in part to the sulphide distribution, but not directly with the ore mineralization. As in any exploration project, interpretation of both surveys has yielded an improved understanding of the geology, alteration and mineralization of the Pebble system and this will serve well for on-going exploration activities. There are distinct practical advantages to the use of both SPECTREM and ZTEM, so we draw no recommendation for either system. We can conclude however, that 3D inversion of both AEM and ZTEM surveys is now a practical consideration and that it has added value to exploration at Pebble.

  19. Studies on crude oil removal from pebbles by the application of biodiesel.

    PubMed

    Xia, Wen-xiang; Xia, Yan; Li, Jin-cheng; Zhang, Dan-feng; Zhou, Qing; Wang, Xin-ping

    2015-02-15

    Oil residues along shorelines are hard to remove after an oil spill. The effect of biodiesel to eliminate crude oil from pebbles alone and in combination with petroleum degrading bacteria was investigated in simulated systems. Adding biodiesel made oil detach from pebbles and formed oil-biodiesel mixtures, most of which remained on top of seawater. The total petroleum hydrocarbon (TPH) removal efficiency increased with biodiesel quantities but the magnitude of augment decreased gradually. When used with petroleum degrading bacteria, the addition of biodiesel (BD), nutrients (NUT) and BD+NUT increased the dehydrogenase activity and decreased the biodegradation half lives. When BD and NUT were replenished at the same time, the TPH removal efficiency was 7.4% higher compared to the total improvement of efficiency when BD and NUT was added separately, indicating an additive effect of biodiesel and nutrients on oil biodegradation. PMID:25510547

  20. BRILLIANT PEBBLES: A METHOD FOR DETECTION OF VERY LARGE INTERSTELLAR GRAINS

    SciTech Connect

    Socrates, Aristotle; Draine, Bruce T. E-mail: draine@astro.princeton.edu

    2009-09-01

    A photon of wavelength {lambda} {approx} 1 {mu}m interacting with a dust grain of radius a{sub p} {approx} 1 mm (a 'pebble') undergoes scattering in the forward direction, largely within a small characteristic diffraction angle {theta}{sub s} {approx} {lambda}/a{sub p} {approx} 100''. Though millimeter-size dust grains contribute negligibly to the interstellar medium's visual extinction, the signal they produce in scattered light may be detectable, especially for variable sources. Observations of light scattered at small angles allow for the direct measurement of the large grain population; variable sources can also yield tomographic information of the interstellar medium's mass distribution. The ability to detect brilliant pebble halos requires a careful understanding of the instrument point-spread function.

  1. Sojourner Rover View of Well-Rounded Pebbles in Cabbage Patch

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Sojourner Rover image of rounded 4-cm-wide pebble (lower center) and excavation of cloddy deposit of Cabbage Patch at lower left. Note the bright wind tails of drift material extending from small rocks and the wheel track from upper right to lower left.

    Well-rounded objects, like the one in this image, were not seen at the Viking sites. These are thought to be pebbles liberated from sedimentary rocks composed of cemented silts, sands and rounded fragments; such rocks are called conglomerates.

    NOTE: original caption as published in Science Magazine

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  2. Applications of moving granular-bed filters to advanced systems

    SciTech Connect

    Wilson, K.W.; Haas, J.C.; Eshelman, M.B.

    1993-09-01

    The contract is arranged as a base contract with three options. The objective of the base contract is to develop conceptual design(s) of moving granular bed filter and ceramic candle filter technology for control of particles from integrated gasification combined cycle (IGCC) systems, pressurized fluidized-bed combustors (PFBC), and direct coal fueled turbine (DCFT) environments. The conceptual design(s) of these filter technologies are compared, primarily from an economic perspective. The granular bed filter was developed through low pressure, high temperature (1600{degree}F) testing in the late 1970`s and early 1980`s. Collection efficiencies over 99% were obtained. In 1988, high pressure, high temperature testing was completed at New York University, Westbury, N.Y., utilizing a two advanced power generating plants were chosen for developing conceptual designs and cost estimates of the commercial sized filters. One is the 450 MWe, second generation pressurized fluidized bed combustion plant defined by Foster Wheeler. This plant originally included cross-flow filters for hot gas cleanup. The other plant under study is a 100 MWe, KRW air blown gasifier. A cross-flow filter was utilized for gas stream cleanup in this study also. Granular bed and ceramic candle filters were substituted for the cross-flow filters in both these plants, and the resulting costs were compared.

  3. The Formation of Terrestrial Planets from the Direct Accretion of Pebbles

    NASA Astrophysics Data System (ADS)

    Levison, Harold F.; Kretke, Katherine A.; Walsh, Kevin J.

    2015-05-01

    Building the terrestrial planets has been a challenge for planetformation models. In particular, classical theories have been unable to reproduce the small mass of Mars and instead predict that a planet near 1.5 AU should roughly be the same mass as the Earth (Chambers 2001, icarus 152,205). Recently, a new model, known as 'slow pebble accretion', has been developed that can explain the formation of the gas giants (Levison+ 2015, Nature submitted). This model envisions that the cores of the giant planets formed from 100 to 1000 km bodies that directly accreted a population of pebbles (Lambrechts & Johansen 2012, A&A 544, A32) - centimeter- to meter-sized objects that slowly grew in the protoplanetary disk. Here we apply this model to the terrestrial planet region and find that it can reproduce the basic structure of the inner Solar System, including a small Mars and a low-mass asteroid belt. In particular, our models show that for an initial population of planetesimals with sizes similar to those of the main belt asteroids, slow pebble accretion becomes inefficient beyond ~1.5 AU. As a result, Mars's growth is stunted and nothing large in the asteroid belt can accumulate.

  4. Thermo-mechanical analyses of HELICA and HEXCALIBER mock-ups

    NASA Astrophysics Data System (ADS)

    Gan, Yixiang; Kamlah, Marc

    2009-04-01

    As benchmark exercises, HELICA and HEXCALIBER mock-ups have been launched in the HE-FUS 3 facility at ENEA Brasimone for investigating the thermo-mechanical behaviour of pebble beds. The present material model of pebble beds, based on the modified Drucker-Prager-Cap model, has been implemented in the commercial finite element package, ABAQUS. The overall behaviour of the lithium orthosilicate cassette (HELICA) and the interactions of ceramic breeder pebble beds and beryllium pebble beds (HEXCALIBER) are studied numerically. The finite element analyses show the temperature distribution of the mock-up experiments, as well as the stress-strain fields. The predictions of HELICA mock-up are compared with the experiments, including the temperature measured by thermo-couples located inside the pebble beds and the lateral deformation of the cell.

  5. Fluidized bed calciner apparatus

    DOEpatents

    Owen, Thomas J.; Klem, Jr., Michael J.; Cash, Robert J.

    1988-01-01

    An apparatus for remotely calcining a slurry or solution feed stream of toxic or hazardous material, such as ammonium diurante slurry or uranyl nitrate solution, is disclosed. The calcining apparatus includes a vertical substantially cylindrical inner shell disposed in a vertical substantially cylindrical outer shell, in which inner shell is disposed a fluidized bed comprising the feed stream material to be calcined and spherical beads to aid in heat transfer. Extending through the outer and inner shells is a feed nozzle for delivering feed material or a cleaning chemical to the beads. Disposed in and extending across the lower portion of the inner shell and upstream of the fluidized bed is a support member for supporting the fluidized bed, the support member having uniform slots for directing uniform gas flow to the fluidized bed from a fluidizing gas orifice disposed upstream of the support member. Disposed in the lower portion of the inner shell are a plurality of internal electric resistance heaters for heating the fluidized bed. Disposed circumferentially about the outside length of the inner shell are a plurality of external heaters for heating the inner shell thereby heating the fluidized bed. Further, connected to the internal and external heaters is a means for maintaining the fluidized bed temperature to within plus or minus approximately 25.degree. C. of a predetermined bed temperature. Disposed about the external heaters is the outer shell for providing radiative heat reflection back to the inner shell.

  6. Volunteer Shelter Bed Programs.

    ERIC Educational Resources Information Center

    Little (Arthur D.), Inc., Washington, DC.

    The volunteer shelter bed program development guidelines in this booklet are offered as a community-based alternative to the institutionalization of status offenders. The volunteer shelter bed program is described as a nonsecure residential alternative for status offenders, which can be implemented without the creation of new facilities or the…

  7. The friction and wear of ceramic/ceramic and ceramic/metal combinations in sliding contact

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.; Dellacorte, Christopher

    1994-01-01

    The tribological characteristics of ceramics sliding on ceramics are compared to those of ceramics sliding on a nickel-based turbine alloy. The friction and wear of oxide ceramics and silicon-based ceramics in air at temperatures from room ambient to 900 C (in a few cases to 1200 C) were measured for a hemispherically-tipped pin on a flat sliding contact geometry. In general, especially at high temperature, friction and wear were lower for ceramic/metal combinations than for ceramic/ceramic combinations. The better tribological performance for ceramic/metal combinations is attributed primarily to the lubricious nature of the oxidized surface of the metal.

  8. The friction and wear of ceramic/ceramic and ceramic/metal combinations in sliding contact

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.; Dellacorte, Christopher

    1993-01-01

    The tribological characteristics of ceramics sliding on ceramics are compared to those of ceramics sliding on a nickel based turbine alloy. The friction and wear of oxide ceramics and silicon-based ceramics in air at temperatures from room ambient to 900 C (in a few cases to 1200 C) were measured for a hemispherically-tipped pin on a flat sliding contact geometry. In general, especially at high temperature, friction and wear were lower for ceramic/metal combinations than for ceramic/ceramic combinations. The better tribological performance for ceramic/metal combinations is attributed primarily to the lubricious nature of the oxidized surface of the metal.

  9. Ceramic tamper-revealing seals

    DOEpatents

    Kupperman, David S.; Raptis, Apostolos C.; Sheen, Shuh-Haw

    1992-01-01

    A flexible metal or ceramic cable with composite ceramic ends, or a u-shaped ceramic connecting element attached to a binding element plate or block cast from alumina or zirconium, and connected to the connecting element by shrink fitting.

  10. Analyses of fine paste ceramics

    SciTech Connect

    Sabloff, J A

    1980-01-01

    Four chapters are included: history of Brookhaven fine paste ceramics project, chemical and mathematical procedures employed in Mayan fine paste ceramics project, and compositional and archaeological perspectives on the Mayan fine paste ceramics. (DLC)

  11. Validation of In-Situ Iron-Manganese Oxide Coated Stream Pebbles as Sensors for Arsenic Source Monitoring

    NASA Astrophysics Data System (ADS)

    Blake, J.; Peters, S. C.; Casteel, A.

    2013-12-01

    Locating nonpoint source contaminant fluxes can be challenging due to the inherent heterogeneity of source and of the subsurface. Contaminants such as arsenic are a concern for drinking water quality and ecosystem health. Arsenic contamination can be the result of several natural and anthropogenic sources, and therefore it can be difficult to trace and identify major areas of arsenic in natural systems. Identifying a useful source indicator for arsenic is a crucial step for environmental remediation efforts. Previous studies have found iron-manganese oxide coated streambed pebbles as useful source indicators due to their high attraction for heavy metals in water. In this study, pebbles, surface water at baseflow and nearby rocks were sampled from the Pennypack Creek and its tributaries, in southwestern Pennsylvania, to test the ability of coated streambed pebbles as environmental source indicators for arsenic. Quartz pebbles, 5-7 cm in diameter, were sampled to minimize elemental contamination from rock chemistry. In addition, quartz provides an excellent substrate for iron and manganese coatings to form. These coatings were leached from pebbles using 4M nitric acid with 0.1% concentrated hydrochloric acid. Following sample processing, analyses were performed using an ICP-MS and the resulting data were spatially organized using ArcGIS software. Arsenic, iron and manganese concentrations in the leachate are normalized to pebble surface area and each location is reported as a ratio of arsenic to iron and manganese. Results suggest that iron-manganese coated stream pebbles are useful indicators of arsenic location within a watershed.

  12. Thermal/chemical degradation of ceramic cross-flow filter materials

    SciTech Connect

    Alvin, M.A.; Lane, J.E.; Lippert, T.E.

    1989-11-01

    This report summarizes the 14-month, Phase 1 effort conducted by Westinghouse on the Thermal/Chemical Degradation of Ceramic Cross-Flow Filter Materials program. In Phase 1 expected filter process conditions were identified for a fixed-bed, fluid-bed, and entrained-bed gasification, direct coal fired turbine, and pressurized fluidized-bed combustion system. Ceramic cross-flow filter materials were also selected, procured, and subjected to chemical and physical characterization. The stability of each of the ceramic cross-flow materials was assessed in terms of potential reactions or phase change as a result of process temperature, and effluent gas compositions containing alkali and fines. In addition chemical and physical characterization was conducted on cross-flow filters that were exposed to the METC fluid-bed gasifier and the New York University pressurized fluidized-bed combustor. Long-term high temperature degradation mechanisms were proposed for each ceramic cross-flow material at process operating conditions. An experimental bench-scale test program is recommended to be conducted in Phase 2, generating data that support the proposed cross-flow filter material thermal/chemical degradation mechanisms. Papers on the individual subtasks have been processed separately for inclusion on the data base.

  13. Superconductive ceramic oxide combination

    SciTech Connect

    Chatterjee, D.K.; Mehrotra, A.K.; Mir, J.M.

    1991-03-05

    This patent describes the combination of a superconductive ceramic oxide which degrades in conductivity upon contact of ambient air with its surface and, interposed between the ceramic oxide surface and ambient air in the amount of at least 1 mg per square meter of surface area of the superconductive ceramic oxide, a passivant polymer selected from the group consisting of a polyester ionomer and an alkyl cellulose.

  14. Ceramic Electron Multiplier

    DOE PAGESBeta

    Comby, G.

    1996-10-01

    The Ceramic Electron Multipliers (CEM) is a compact, robust, linear and fast multi-channel electron multiplier. The Multi Layer Ceramic Technique (MLCT) allows to build metallic dynodes inside a compact ceramic block. The activation of the metallic dynodes enhances their secondary electron emission (SEE). The CEM can be used in multi-channel photomultipliers, multi-channel light intensifiers, ion detection, spectroscopy, analysis of time of flight events, particle detection or Cherenkov imaging detectors. (auth)

  15. Continuous Fiber Ceramic Composites

    SciTech Connect

    2002-09-01

    Fiber-reinforced ceramic composites demonstrate the high-temperature stability of ceramics--with an increased fracture toughness resulting from the fiber reinforcement of the composite. The material optimization performed under the continuous fiber ceramic composites (CFCC) included a series of systematic optimizations. The overall goals were to define the processing window, to increase the robustinous of the process, to increase process yield while reducing costs, and to define the complexity of parts that could be fabricated.

  16. Alumina-based ceramic composite

    DOEpatents

    Alexander, Kathleen B.; Tiegs, Terry N.; Becher, Paul F.; Waters, Shirley B.

    1996-01-01

    An improved ceramic composite comprising oxide ceramic particulates, nonoxide ceramic particulates selected from the group consisting of carbides, borides, nitrides of silicon and transition metals and mixtures thereof, and a ductile binder selected from the group consisting of metallic, intermetallic alloys and mixtures thereof is described. The ceramic composite is made by blending powders of the ceramic particulates and the ductile to form a mixture and consolidating the mixture of under conditions of temperature and pressure sufficient to produce a densified ceramic composite.

  17. Method of sintering ceramic materials

    DOEpatents

    Holcombe, Cressie E.; Dykes, Norman L.

    1992-01-01

    A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density.

  18. Method of sintering ceramic materials

    DOEpatents

    Holcombe, C.E.; Dykes, N.L.

    1992-11-17

    A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density. 2 figs.

  19. Measuring Fracture Times Of Ceramics

    NASA Technical Reports Server (NTRS)

    Shlichta, Paul J.; Bister, Leo; Bickler, Donald G.

    1989-01-01

    Electrical measurements complement or replace fast cinematography. Electronic system measures microsecond time intervals between impacts of projectiles on ceramic tiles and fracture tiles. Used in research on ceramics and ceramic-based composite materials such as armor. Hardness and low density of ceramics enable them to disintegrate projectiles more efficiently than metals. Projectile approaches ceramic tile specimen. Penetrating foil squares of triggering device activate display and recording instruments. As ceramic and resistive film break oscilloscope plots increase in electrical resistance of film.

  20. Ceramic brush seals development

    NASA Technical Reports Server (NTRS)

    Howe, Harold

    1994-01-01

    The following topics are discussed in this viewgraph presentation: ceramic brush seals, research and development, manufacturing, brazed assembly development, controlling braze flow, fiber selection, and braze results.

  1. Corrosion of Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Jacobson, Nathan S.

    1999-01-01

    Non-oxide ceramics are promising materials for a range of high temperature applications. Selected current and future applications are listed. In all such applications, the ceramics are exposed to high temperature gases. Therefore it is critical to understand the response of these materials to their environment. The variables to be considered here include both the type of ceramic and the environment to which it is exposed. Non-oxide ceramics include borides, nitrides, and carbides. Most high temperature corrosion environments contain oxygen and hence the emphasis of this chapter will be on oxidation processes.

  2. Dry pressing technical ceramics

    SciTech Connect

    Lewis, W.A. Jr.

    1996-04-01

    Dry pressing of technical ceramics is a fundamental method of producing high-quality ceramic components. The goals of dry pressing technical ceramics are uniform compact size and green density, consistent part-to-part green density and defect-free compact. Dry pressing is the axial compaction of loosely granulated dry ceramic powders (< 3% free moisture) within a die/punch arrangement. The powder, under pressure, conforms to the specific shape of the punch faces and die. Powder compaction occurs within a rigid-walled die and usually between a top and bottom punch. Press configurations include anvil, rotary, multiple-punch and multiple-action.

  3. Defect production in ceramics

    SciTech Connect

    Zinkle, S.J.; Kinoshita, C.

    1997-08-01

    A review is given of several important defect production and accumulation parameters for irradiated ceramics. Materials covered in this review include alumina, magnesia, spinel silicon carbide, silicon nitride, aluminum nitride and diamond. Whereas threshold displacement energies for many ceramics are known within a reasonable level of uncertainty (with notable exceptions being AIN and Si{sub 3}N{sub 4}), relatively little information exists on the equally important parameters of surviving defect fraction (defect production efficiency) and point defect migration energies for most ceramics. Very little fundamental displacement damage information is available for nitride ceramics. The role of subthreshold irradiation on defect migration and microstructural evolution is also briefly discussed.

  4. Status of the fluidized bed unit

    SciTech Connect

    Williams, P.M.; Wade, J.F.

    1994-06-01

    Rocky Flats has a serious mixed waste problem. No technology or company has a license and available facilities to remedy this dilemma. One solution under study is to use a catalytic fluidized bed unit to destroy the combustible portion of the mixed waste. The fluidized bed thermal treatment program at Rocky Flats is building on knowledge gained over twenty years of successful development activity. The FBU has numerous technical advantages over other thermal technologies to treat Rocky Flats` mixed waste, the largest being the lower temperature (700{degrees}C versus 1000{degrees}C) which reduces acid corrosion and mechanical failures and obviates the need for ceramic lining. Successful demonstrations have taken place on bench, pilot, and full-scale tests using radioactive mixed wastes. The program is approaching implementation and licensing of a production-scale fluidized bed system for the safe treatment of mixed waste. The measure for success on this project is the ability to work closely with the community to jointly solve problems and respond to concerns of mixed waste treatment at Rocky Flats.

  5. Air gasification of rice husk in bubbling fluidized bed reactor with bed heating by conventional charcoal.

    PubMed

    Makwana, J P; Joshi, Asim Kumar; Athawale, Gaurav; Singh, Dharminder; Mohanty, Pravakar

    2015-02-01

    An experimental study of air gasification of rice husk was conducted in a bench-scale fluidized bed gasifier (FBG) having 210 mm diameter and 1600 mm height. Heating of sand bed material was performed using conventional charcoal fuel. Different operating conditions like bed temperature, feeding rate and equivalence ratio (ER) varied in the range of 750-850 °C, 25-31.3 kg/h, and 0.3-0.38, respectively. Flow rate of air was kept constant (37 m(3)/h) during FBG experiments. The carbon conversion efficiencies (CCE), cold gas efficiency, and thermal efficiency were evaluated, where maximum CCE was found as 91%. By increasing ER, the carbon conversion efficiency was decreased. Drastic reduction in electric consumption for initial heating of gasifier bed with charcoal compared to ceramic heater was ∼45%. Hence rice husk is found as a potential candidate to use directly (without any processing) in FBG as an alternative renewable energy source from agricultural field. PMID:25446789

  6. Ceramic Technology Project

    SciTech Connect

    Not Available

    1992-03-01

    The Ceramic Technology Project was developed by the USDOE Office of Transportation Systems (OTS) in Conservation and Renewable Energy. This project, part of the OTS's Materials Development Program, was developed to meet the ceramic technology requirements of the OTS's automotive technology programs. Significant accomplishments in fabricating ceramic components for the USDOE and NASA advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. These programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and data base and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. A five-year project plan was developed with extensive input from private industry. In July 1990 the original plan was updated through the estimated completion of development in 1993. The objective is to develop the industrial technology base required for reliable ceramics for application in advanced automotive heat engines. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on the structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines. To facilitate the rapid transfer of this technology to US industry, the major portion of the work is being done in the ceramic industry, with technological support from government laboratories, other industrial laboratories, and universities.

  7. Out-of-pile tritium release study on Li 4SiO 4 pebbles from TRINPC-I experiments

    NASA Astrophysics Data System (ADS)

    Kang, Chunmei; Wang, Xiaolin; Xiao, Chengjian; Gao, Xiaoling; Gu, Mei; Liu, Jun; Wang, Heyi; Peng, Shuming; Chen, Xiaojun

    2011-05-01

    Out-of-pile tritium release examinations of irradiated Li 4SiO 4 pebbles were performed in TRINPC-I experiments for evaluating material performance and verifying the system design. To generate tritium the specimens were irradiated with neutrons. Li 4SiO 4 pebbles were made by a freeze-drying method. In the experiments, concentrations of tritium in the form of tritium gas (HT + T 2) and tritiated water (HTO + T 2O) in the outlet streams of a reactor tube were measured separately with an ionization chamber and a liquid scintillation radiometer. The results show that the percentage of tritium gas (HT + T 2) and tritiated water trapped by the breeder pebbles were about 72% and 19% of totally released tritium, respectively. Thus, more tritium was released in the form of tritium gas in this work. In addition to tritium trapped by the breeder pebbles, the amount of free tritium was also measured by breaking on-line a quartz capsule containing Li 4SiO 4 pebbles, the percentage of which was 9% of totally released tritium. The temperature peaks of tritium gas mainly appeared at about 477 °C and 654 °C, while the temperature peak of tritiated water appeared at about 402 °C, under which most of tritiated water released.

  8. Bed rest during pregnancy

    MedlinePlus

    ... provider before you start any activity: Squeezing stress balls Pressing your hands and feet against the bed ... limit yourself from doing any of these: Cooking Light chores Walking Bathing or showering Driving Having sex ...

  9. Tapered bed bioreactor

    DOEpatents

    Scott, Charles D.; Hancher, Charles W.

    1977-01-01

    A vertically oriented conically shaped column is used as a fluidized bed bioreactor wherein biologically catalyzed reactions are conducted in a continuous manner. The column utilizes a packing material a support having attached thereto a biologically active catalytic material.

  10. Test Bed For Telerobots

    NASA Technical Reports Server (NTRS)

    Matijevic, Jacob R.; Zimmerman, Wayne F.; Dolinsky, Shlomo

    1990-01-01

    Assembly of electromechanical and electronic equipment (including computers) constitutes test bed for development of advanced robotic systems for remote manipulation. Combines features not found in commercial systems. Its architecture allows easy growth in complexity and level of automation. System national resource for validation of new telerobotic technology. Intended primarily for robots used in outer space, test bed adapted to development of advanced terrestrial telerobotic systems for handling radioactive materials, dangerous chemicals, and explosives.

  11. Robocasting of Ceramics and Composites Using Fine Particle Suspensions

    SciTech Connect

    CESARANO III,JOSEPH

    1999-10-28

    Solid freeform fabrication is the near-net-shape manufacturing of components by sequentially stacking thin layers of material until complicated three dimensional shapes are produced. The operation is computer controlled and requires no molds. This exciting new field of technology provides engineers with the ability to rapidly produce prototype parts directly from CAD drawings and oftentimes little or no machining is necessary after fabrication. Techniques for freeform fabrication with several types of plastics and metals are already quite advanced and maybe reviewed in references 1 and 2. Very complicated plastic models can be fabricated by stereolithography, selective laser sintering, fused deposition modeling, or three-dimensional ink jet printing. Metals may be freeformed by the LENS{trademark} technique and porous ceramic bodies by three dimensional printing into a porous powder bed. However, methods for freeform fabrication that utilize particulate slurries to build dense ceramics and composites are not as well developed. The techniques that are being developed for the freeform fabrication of dense structural ceramics primarily revolve around the sequential layering of ceramic loaded polymers or waxes. Laminated Object Manufacturing and CAM-LEM processing use controlled stacking and laser cutting of ceramic tapes [2,3]. Similar to fused deposition modeling, ceramic loaded polymer/wax filaments are being used for the fused deposition of ceramics [2,4]. Extrusion freeform fabrication uses high pressure extrusion to deposit layers of ceramic loaded polymer/wax systems[1]. Modified stereolithographic techniques are also being developed using ceramic loaded ultraviolet curable resins [2]. Pre-sintered parts made with any of these techniques typically have 40-55 vol.% polymeric binder. In this regard, these techniques are analogous to powder injection molding of ceramics. Very long and complicated burnout heat treatments are necessary to produce a dense ceramic

  12. Ceramics for engines

    NASA Technical Reports Server (NTRS)

    Kiser, James D.; Levine, Stanley R.; Dicarlo, James A.

    1990-01-01

    The NASA Lewis Research Center's Ceramic Technology Program is focused on aerospace propulsion and power needs. Thus, emphasis is on high-temperature ceramics and their structural and environmental durability and reliability. The program is interdisciplinary in nature with major emphasis on materials and processing, but with significant efforts in design methodology and life prediction.

  13. Fabrication Of Ceramic Mats

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr.

    1991-01-01

    Process to make mats of fine zirconia filaments proposed. Ceramic mats formed by sintering mats of partially dried filaments extruded from slurry of ceramic powder, binder, and solvent. Mats of fine zirconia fibers easier to ball-mill than commercially available zirconia powder.

  14. Industrial Ceramics: Secondary Schools.

    ERIC Educational Resources Information Center

    New York City Board of Education, Brooklyn, NY. Bureau of Curriculum Development.

    The expanding use of ceramic products in today's world can be seen in the areas of communications, construction, aerospace, textiles, metallurgy, atomic energy, and electronics. The demands of science have brought ceramics from an art to an industry using mass production and automated processes which requires the services of great numbers as the…

  15. Bed rest and immunity

    NASA Astrophysics Data System (ADS)

    Sonnenfeld, Gerald; Aviles, Hernan; Butel, Janet S.; Shearer, William T.; Niesel, David; Pandya, Utpal; Allen, Christopher; Ochs, Hans D.; Blancher, Antoine; Abbal, Michel

    2007-02-01

    Space flight has been shown to result in altered immune responses. The current study was designed to investigate this possibility by using the bed rest model of some space flight conditions. A large number of women are included as subjects in the study. The hypothesis being tested is: 60 days head-down tilt bed rest of humans will affect the immune system and resistance to infection. Blood, urine and saliva samples will be obtained from bed rest subjects prior to, at intervals during, and after completion of 60 days of head-down tilt bed rest. Leukocyte blastogenesis, cytokine production and virus reactivation will be assessed. The ability of the subjects to respond appropriately to immunization with the neoantigen bacteriophage φX-174 will also be determined. Bed rest is being carried out at MEDES, Toulouse France, and the University of Texas Medical Branch, Galveston, TX. The studies to be carried out in France will also allow assessment of the effects of muscle/bone exercise and nutritional countermeasures on the immune system in addition to the effects of bed rest.

  16. Method of making a modified ceramic-ceramic composite

    DOEpatents

    Weaver, Billy L.; McLaughlin, Jerry C.; Stinton, David P.

    1995-01-01

    The present invention provides a method of making a shaped ceramic-ceramic composite articles, such as gas-fired radiant heat burner tubes, heat exchangers, flame dispersers, and other furnace elements, having a formed-on ceramic-ceramic composite thereon.

  17. Ceramic heat exchanger

    DOEpatents

    LaHaye, P.G.; Rahman, F.H.; Lebeau, T.P.; Severin, B.K.

    1998-06-16

    A tube containment system is disclosed. The tube containment system does not significantly reduce heat transfer through the tube wall. The contained tube is internally pressurized, and is formed from a ceramic material having high strength, high thermal conductivity, and good thermal shock resistance. The tube containment system includes at least one ceramic fiber braid material disposed about the internally pressurized tube. The material is disposed about the tube in a predetermined axial spacing arrangement. The ceramic fiber braid is present in an amount sufficient to contain the tube if the tube becomes fractured. The tube containment system can also include a plurality of ceramic ring-shaped structures, in contact with the outer surface of the tube, and positioned between the tube and the ceramic fiber braid material, and/or at least one transducer positioned within tube for reducing the internal volume and, therefore, the energy of any shrapnel resulting from a tube fracture. 6 figs.

  18. Ceramic heat exchanger

    DOEpatents

    LaHaye, Paul G.; Rahman, Faress H.; Lebeau, Thomas P. E.; Severin, Barbara K.

    1998-01-01

    A tube containment system. The tube containment system does not significantly reduce heat transfer through the tube wall. The contained tube is internally pressurized, and is formed from a ceramic material having high strength, high thermal conductivity, and good thermal shock resistance. The tube containment system includes at least one ceramic fiber braid material disposed about the internally pressurized tube. The material is disposed about the tube in a predetermined axial spacing arrangement. The ceramic fiber braid is present in an amount sufficient to contain the tube if the tube becomes fractured. The tube containment system can also include a plurality of ceramic ring-shaped structures, in contact with the outer surface of the tube, and positioned between the tube and the ceramic fiber braid material, and/or at least one transducer positioned within tube for reducing the internal volume and, therefore, the energy of any shrapnel resulting from a tube fracture.

  19. Mounting for ceramic scroll

    DOEpatents

    Petty, Jack D.

    1993-01-01

    A mounting for a ceramic scroll on a metal engine block of a gas turbine engine includes a first ceramic ring and a pair of cross key connections between the first ceramic ring, the ceramic scroll, and the engine block. The cross key connections support the scroll on the engine block independent of relative radial thermal growth and for bodily movement toward an annular mounting shoulder on the engine. The scroll has an uninterrupted annular shoulder facing the mounting shoulder on the engine block. A second ceramic ring is captured between mounting shoulder and the uninterrupted shoulder on the scroll when the latter is bodily shifted toward the mouting shoulder to define a gas seal between the scroll and the engine block.

  20. Strain isolated ceramic coatings

    NASA Technical Reports Server (NTRS)

    Tolokan, R. P.; Brady, J. B.; Jarrabet, G. P.

    1985-01-01

    Plasma sprayed ceramic coatings are used in gas turbine engines to improve component temperature capability and cooling air efficiency. A compliant metal fiber strain isolator between a plasma sprayed ceramic coating and a metal substrate improves ceramic durability while allowing thicker coatings for better insulation. Development of strain isolated coatings has concentrated on design and fabrication of coatings and coating evaluation via thermal shock testing. In thermal shock testing, five types of failure are possible: buckling failure im compression on heat up, bimetal type failure, isothermal expansion mismatch failure, mudflat cracking during cool down, and long term fatigue. A primary failure mode for thermally cycled coatings is designated bimetal type failure. Bimetal failure is tensile failure in the ceramic near the ceramic-metal interface. One of the significant benefits of the strain isolator is an insulating layer protecting the metal substrate from heat deformation and thereby preventing bimetal type failure.

  1. Control of bed height in a fluidized bed gasification system

    DOEpatents

    Mehta, Gautam I.; Rogers, Lynn M.

    1983-12-20

    In a fluidized bed apparatus a method for controlling the height of the fdized bed, taking into account variations in the density of the bed. The method comprises taking simultaneous differential pressure measurements at different vertical elevations within the vessel, averaging the differential pressures, determining an average fluidized bed density, then periodically calculating a weighting factor. The weighting factor is used in the determination of the actual bed height which is used in controlling the fluidizing means.

  2. Jumping the gap: the formation conditions and mass function of `pebble-pile' planetesimals

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.

    2016-03-01

    In a turbulent proto-planetary disc, dust grains undergo large-density fluctuations and under the right circumstances, grain overdensities can collapse under self-gravity (forming a `pebble-pile' planetesimal). Using a simple model for fluctuations predicted in simulations, we estimate the rate of formation and mass function of self-gravitating planetesimal-mass bodies formed by this mechanism. This depends sensitively on the grain size, disc surface density, and turbulent Mach numbers. However, when it occurs, the resulting planetesimal mass function is broad and quasi-universal, with a slope dN/dM ∝ M-(1-2), spanning size/mass range ˜10-104 km (˜10-9-5 M⊕). Collapse to planetesimal through super-Earth masses is possible. The key condition is that grain density fluctuations reach large amplitudes on large scales, where gravitational instability proceeds most easily (collapse of small grains is suppressed by turbulence). This leads to a new criterion for `pebble-pile' formation: τs ≳ 0.05 ln (Q1/2/Zd)/ln (1 + 10 α1/4) ˜ 0.3 ψ(Q, Z, α) where τs = ts Ω is the dimensionless particle stopping time. In a minimum-mass solar nebula, this requires grains larger than a = (50, 1, 0.1) cm at r=(1, 30, 100) au}. This may easily occur beyond the ice line, but at small radii would depend on the existence of large boulders. Because density fluctuations depend strongly on τs (inversely proportional to disc surface density), lower density discs are more unstable. Conditions for pebble-pile formation also become more favourable around lower mass, cooler stars.

  3. Accretion of Cometary Nuclei in the Solar Nebula: Boulders, Not Pebbles

    NASA Astrophysics Data System (ADS)

    Weissman, Paul R.; A'Hearn, Michael

    2015-11-01

    Comets are the most primitive bodies in the solar system. They retain a largely unprocessed record of conditions in the primordial solar nebula 4.56 Gyr ago, including the initial accretion of dust and ice particles into macroscopic bodies. Current accretion theory suggests that ice and dust aggregates grew to pebble (cm) sizes before streaming instabilities and gravitational collapse brought these pebble swarms together as km-sized (or larger) bodies. Recent imaging of the nucleus of comet 67P/Churyumov-Gerasimenko by the Rosetta OSIRIS camera team has revealed the existence of “goose bump” terrain on the nucleus surface and lining the interior walls of large, ~200 m diameter and 180 m deep cylindrical pits. These pits are believed to be sinkholes, formed when near-surface materials collapse into voids within the nucleus, revealing the fresh comet interior on the walls of the pits. The goose bump terrain consists of 3-4 m diameter “boulders” randomly stacked one on top of another. We propose that these boulders, likely with an icy-conglomerate composition, are the basic building blocks of cometary nuclei. This is the first observational confirmation of current accretion theories, with the caveat that rather than pebbles, the preferred size range is 3-4 m boulders for objects formed in the giant planets region of the solar system. The presence of icy grains beyond the solar nebula snow-line and the large heliocentric range of the giant planets region likely contribute to the formation of these larger boulders, before they are incorporated into cometary nuclei. This work was supported by NASA through the U.S. Rosetta Project.

  4. Making Planet Nine: Pebble Accretion at 250–750 AU in a Gravitationally Unstable Ring

    NASA Astrophysics Data System (ADS)

    Kenyon, Scott J.; Bromley, Benjamin C.

    2016-07-01

    We investigate the formation of icy super-Earth mass planets within a gravitationally unstable ring of solids orbiting at 250–750 AU around a 1 {M}ȯ star. Coagulation calculations demonstrate that a system of a few large oligarchs and a swarm of pebbles generates a super-Earth within 100–200 Myr at 250 AU and within 1–2 Gyr at 750 AU. Systems with more than ten oligarchs fail to yield super-Earths over the age of the solar system. As these systems evolve, destructive collisions produce detectable debris disks with luminosities of {10}-5{--}{10}-3 relative to the central star.

  5. Geology and uranium evaluation of the precambrian quartz-pebble conglomerates of the Needle Mountains, Southwest Colorado. Final report

    SciTech Connect

    Burns, L.K.; Ethridge, F.G.; Tyler, N.; Gross, A.S.; Campo, A.M.

    1980-05-01

    Precambrian quartz-pebble conglomerates of the Needle Mountains of southwest Colorado are present in the Vallecito Conglomerate and the basal conglomerate of Uncompahgre Formation. Three conglomerates have lithologic, sedimentologic and mineralogic characteristics that are similar to those of the Precambrian uranium-bearing fossil placer deposits of the Witwatersrand in South Africa and the Blind River Elliot Lake district in Ontario, Canada. However, the Precambrian quartz-pebble conglomerates of Colorado do not contain the key indicator minerals of primary detrital pyrite, uraninite, and other uranium mineral species. The absence of these minerals and the structural and stratigraphic relations of these two formations suggest that they were deposited between 1780 and 1460 million years ago. These formations are, therefore, not old enough to have been deposited under the reducing atmospheric conditions thought to be necessary for the formation of placer uranium deposits. The average uranium content of the Precambrian quartz-pebble conglomerates sampled is 2.9 ppM based on analyses of 502 rock samples. Maximum values for uranium (total by neutron activation are 11 ppM for the Vallecito Conglomerate and 5.0 ppM for the basal part of the Uncompahgre Formation. The Vallecito Conglomerate contains on the average 1.2 ppM total uranium and the Uncompahgre Formation contains 1.2 ppM total uranium. These low values further indicate the low potential of these quartz-pebble conglomerates as fossil-placer uranium deposit. Uranium contents of up to 330 ppM were found in dark slates of the Uncompahgre Formation; however, these units were not closely associated with the pebble conglomerates. Some potential uranium targets of vein type and in black pelitic units are found in the Uncompahgre Formation, but these are not the fossil-placer quartz-pebble conglomerate type of deposits.

  6. Tracing bed load sediment using PIT tags in a steep headwater channel.

    NASA Astrophysics Data System (ADS)

    Kubo, Y.; Hiraoka, M.; Gomi, T.; Nidaira, K.; Uchiyama, Y.

    2015-12-01

    Bed load transport in steep headwater channels is complex because of the particle size distribution, topography, channel roughness, and sediment supply from adjacent hillslope. We monitored movement bed load sediment using PIT tags in a steep headwater channel segments. Study area is located in 7.0ha Oobora-sawa observatory from 50km west of Tokyo metropolitan. Annual precipitation is 3000mm and mean temperature is 10°. Annual bed load sediment yields in the study catchment was from 6.5 to 7.6 t/ha/yr. Mean channel gradient is 24° with 0.5m low flow width. The channel is consisted by 0.2 to 1.6m interval of step-pool sequences. Based on pebble count method, D10, D50 and D90 of channel substrate were 8, 28 and 206mm respectively. We deployed 134 bed load tracers with five classes of diameter ranges (Class1:17.7, Class2:24.8, Class3:35.8, Class4:54.1 and Class5:83.8mm). Selected tracers represented from D20 to D77 of channel bed substrates. PIT tags (diameter 2mm, length 9mm and weight 0.1g) were placed into the particles by drilling and refilled with non-corrosive epoxy. We investigated the movement of bed load tracers every major storm event since February 2015. Channel morphology was measured using photographic survey and topographic model was developed using software of Surface from motion (PhotoScan). Mean bed load movement in the 5 storm event with 438 mm total and 33 mm maximum intensity was 168 mm. Then 51 mm of bed load movement occurred in 43 mm total and 16 mm intensity of rainfall. Recurrence interval of the two storm event was 1 and 4 year respectively. Receivable rates of bed load tracers was 70 and 74 % in the two events. Mobilized bed load (7 to 18%) deposited at cascade, pool and riffle, and among step clusters. Mobilized bed load tracers is rather random and we do not find any patterns for particle size for the movement and distance. Our field monitoring showed that bed load tracers were not mobilized for storm events with 10.5mm/h intensity of

  7. Additive Manufacturing of SiC Based Ceramics and Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Halbig, Michael Charles; Singh, Mrityunjay

    2015-01-01

    Silicon carbide (SiC) ceramics and SiC fiber reinforcedSiC ceramic matrix composites (SiCSiC CMCs) offer high payoff as replacements for metals in turbine engine applications due to their lighter weight, higher temperature capability, and lower cooling requirements. Additive manufacturing approaches can offer game changing technologies for the quick and low cost fabrication of parts with much greater design freedom and geometric complexity. Four approaches for developing these materials are presented. The first two utilize low cost 3D printers. The first uses pre-ceramic pastes developed as feed materials which are converted to SiC after firing. The second uses wood containing filament to print a carbonaceous preform which is infiltrated with a pre-ceramic polymer and converted to SiC. The other two approaches pursue the AM of CMCs. The first is binder jet SiC powder processing in collaboration with rp+m (Rapid Prototyping+Manufacturing). Processing optimization was pursued through SiC powder blending, infiltration with and without SiC nano powder loading, and integration of nanofibers into the powder bed. The second approach was laminated object manufacturing (LOM) in which fiber prepregs and laminates are cut to shape by a laser and stacked to form the desired part. Scanning electron microscopy was conducted on materials from all approaches with select approaches also characterized with XRD, TGA, and bend testing.

  8. Driftwood dropstones in mid-Miocene shallow marine strata (Calvert Cliffs, Maryland Coastal Plain): An erratic lithic pebble des not necessarily a cold paleoclimate make

    NASA Astrophysics Data System (ADS)

    Vogt, P. R.; Parrish, M.

    2009-12-01

    Erratic lithic pebbles recovered from marine sediments are routinely identified as Ice-Rafted Debris (IRD), transported by icebergs, sea ice, or river ice discharged into the sea. We suggest this is not always the transport mechanism--especially when other paleoclimatologic proxies indicate relatively warm climates and extensive forests in the pebble provenance regions. Rivers could transport significant amounts of pebbbles as driftwood dropstones, trapped in the roots of trees and later uprooted in floods and carried out to sea. To illustrate a likely example of Tree-Rafted Detritus (TRD), we analyzed a collection of lithic erratics collected from three beds in eroding (5-10 cm/a) mid-Miocene (Serravalian)shallow marine deposits (upper Calvert Formation,Chesapeake Bay, southern Maryland), which predate the ca. 13.9 Ma global cooling and expansion of the East Antarctic Ice Sheet. The ca. 220 specimens (1-10 cm in diameter) are extremely variable in lithology and degree of roundness. The great majority are evidently of Piedmont provenance and were probably rafted ca. 120 km to the collection site from the paleo-mouth of the Susquehanna River, floated out to sea and carried south by the Miocene Coastal Current. River ice can probably be ruled out as the transport mechanism, given the prevailing warm temperate to subtropical climates. Common carbonized wood fragments (typically 2 x 10 cm in outcrop dimensions) in the same strata containing the erratics support driftwood transport. The lithic erratics may serve as independent tracers for terrestrial vertebrate fossils, transported into the Calvert Sea (Atlantic Ocean) by the 'float and bloat' mechanism.(Allowance has to be made for ca. 20 m/Ma post-middle Miocene source region denudation). However,only 3% of the clasts (mostly quartz diorite gneiss)could be readily related to a specific outcrop--the Port Deposit Gneiss near the modern mouth of the Susquehanna River. We suggest that driftwood transport be considered as

  9. Transport of marked pebbles in short periods of time on a coarse clastic beach (Marina di Pisa, Italy)

    NASA Astrophysics Data System (ADS)

    Bertoni, D.; Ciavola, P.; Grottoli, E.; Sarti, G.

    2012-04-01

    Transport of coarse sediments on coarse clastic beaches still presents aspects that are not fully understood. For instance, there is a generally perceived notion that during fair-weather periods coarse grains hardly move, if not at all. The aim of this experiment is to prove that sediments such as pebbles are subject to significant shift in very short lapses of time and under low energy waves. An artificial coarse clastic beach at Marina di Pisa (Tuscany, Italy) was chosen as study site: Barbarossa beach is 110 m long and is bounded by two groynes. The mean grain size is about 40-to-50 mm. About 80 pebbles were marked by means of the RFID technology, which enables to univocally identify the tracers. The marked pebbles were released along cross-shore transects (one pebble each on the fair-weather berm, on the beachface and on the step crest) on the morning of September 15th, and two recovery campaigns were carried out after 6 and 24 hours from the injection. No particular wave activity was recorded during the time frame of the experiment. After the first recovery campaign, which was performed 6 hours later than the injection, about 94% of the pebbles were detected. After the second recovery campaign, 24 hours later, the recovery rate decreased to 89%. Considering that the technique provides for detection of tracers within 50 cm, the resulting loss of pebbles after so brief spans of time is remarkable. The lack of detection of few tracers implies that the transport rate that they experienced is not negligible. The highest rate of losses was recorded on the beachface, the zone that is subjected the most to waves even under calm conditions. Pebble movement is also confirmed by the fact that tracers detected after the first recovery campaign were not detected once again after the second recovery campaign, and vice versa. The results of the experiment are useful to better define the transport of coarse sediments, verifying that pebbles have to be expected be moving even

  10. High pressure ceramic joint

    DOEpatents

    Ward, M.E.; Harkins, B.D.

    1993-11-30

    Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present joint when used with recuperators increases the use of ceramic components which do not react to highly corrosive gases. Thus, the present joint used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present joint is comprised of a first ceramic member, a second ceramic member, a mechanical locking device having a groove defined in one of the first ceramic member and the second ceramic member. The joint and the mechanical locking device is further comprised of a refractory material disposed in the groove and contacting the first ceramic member and the second ceramic member. The present joint mechanically provides a high strength load bearing joint having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures. 4 figures.

  11. High pressure ceramic joint

    DOEpatents

    Ward, Michael E.; Harkins, Bruce D.

    1993-01-01

    Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present joint when used with recuperators increases the use of ceramic components which do not react to highly corrosive gases. Thus, the present joint used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present joint is comprised of a first ceramic member, a second ceramic member, a mechanical locking device having a groove defined in one of the first ceramic member and the second ceramic member. The joint and the mechanical locking device is further comprised of a refractory material disposed in the groove and contacting the first ceramic member and the second ceramic member. The present joint mechanically provides a high strength load bearing joint having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

  12. All-ceramic crowns.

    PubMed

    Lehner, C R; Schärer, P

    1992-06-01

    Despite the good appearance and biocompatibility of dental porcelains, failures are still of considerable concern because of some limited properties common to all-ceramic crown systems. As in the years before, pertinent scientific articles published between November 1990 and December 1991 focused on strengthening mechanisms and compared fracture toughness for different ceramic systems by using various test methods. Some evaluated the clinical implications thereon for seating and loading crowns and measured wear against different ceramic surface conditions. Recently introduced with pleasing aesthetic qualities, IPS-Empress (Ivoclar, Schaan, Liechtenstein), a new European leucite-reinforced glass-ceramic, has finally drawn attention in some journals and has been reviewed with promising in vitro test results. Using a simple press-molding technique, well-fitting crowns, inlays, and veneers can be fabricated without an additional ceramming procedure. Again, only long-term clinical trials will validate achievements compared with other all-ceramic systems and with well-established metal ceramics. PMID:1325848

  13. Ceramic-silicide composites

    SciTech Connect

    Petrovic, J.J.

    1998-12-01

    The area of ceramic-silicide composites represents a merging of structural ceramics and structural silicides. Such ceramic-silicide composites can possess the desirable characteristics of both classes of compounds. Important structural ceramics are materials such as Si{sub 3}N{sub 4}, SiC, Al{sub 2}O{sub 3}, and ZrO{sub 2}, which possess covalent, ionic, or mixed covalent-ionic atomic bonding. An important structural silicide is MoSi{sub 2}, which possesses mixed covalent-metallic bonding. The arena of ceramic-silicide composites encompasses both composites where the structural silicide is the matrix and the structural ceramic is the reinforcement, and composites where the structural ceramic is the matrix and the structural silicide is the reinforcement. In the former area, MoSi{sub 2}-SiC, MoSi{sub 2}-ZrO{sub 2}, and MoSi{sub 2}-Al{sub 2}O{sub 3} composites are discussed. In the latter area, Si{sub 3}N{sub 4}-MoSi{sub 2} composites are described.

  14. Spacecraft ceramic protective shield

    NASA Technical Reports Server (NTRS)

    Larriva, Rene F. (Inventor); Nelson, Anne (M.); Czechanski, James G. (Inventor); Poff, Ray E. (Inventor)

    1995-01-01

    A low areal density protective shield apparatus, and method for making same, for protecting spacecraft structures from impact with hypervelocity objects, including a bumper member comprising a bumper ceramic layer, a bumper shock attenuator layer, and a bumper confining layer. The bumper ceramic layer can be SiC or B.sub.4 C; the bumper shock attenuator layer can be zirconia felt; and the bumper confining layer can be aluminum. A base armor member can be spaced from the bumper member and a ceramic fiber-based curtain can be positioned between the bumper and base armor members.

  15. Microdischarges in ceramic foams and honeycombs

    NASA Astrophysics Data System (ADS)

    Hensel, K.

    2009-08-01

    Microdischarges in spatially confined geometries, such as microcavities and micropores of various materials, present a promising method for the generation and maintenance of stable discharges at atmospheric pressure. They have been successfully used in many biomedical, environmental and industrial applications. The paper presents two relatively new types of discharges in confined volumes - a capillary microdischarge in ceramic foams and a sliding discharge inside the capillaries of ceramic honeycombs - and describes their basic physical properties and mechanisms. Microdischarges inside the microporous ceramic foams develop from the surface barrier discharge if the amplitude of the applied voltage reaches given threshold, but only for a specific pore size. Sliding discharge inside the honeycomb capillaries is produced by a combination of AC barrier discharge inside catalytic pellet bed coupled in series with DC powered honeycomb monolith. Both discharges produce relatively cold microplasmas with high level of non-equilibrium. The basic characteristics of the microdischarges, addressing the effects of the applied voltage, discharge power, pore size, length and diameter of the capillaries are discussed.

  16. Evidence of fast pebble growth near condensation fronts in the HL Tau protoplanetary disk

    NASA Astrophysics Data System (ADS)

    Zhang, Ke; Blake, Geoffrey; Bergin, Edwin

    2015-08-01

    Water and simple organic molecular ice dominates the mass of solid materials available for planetesimal and planet formation beyond the water snow line. Around the condensation fronts of these most abundant volatile species, rapid pebble growth is predicted to occur based on recent numerical simulations of dust coagulation and settling. Here we propose that the dips in interferometric images of the HL Tau protoplanetary disk are due to rapid pebble growth around condensation fronts. HL Tau, a young star in Taurus molecular cloud, was observed by ALMA at 110, 233 and 343GHz continuum bands with spatial resolution as good as 3 AU. We show that the three dips at distances of 13, 32 and 63 AU are spatially resolved and that their center radii are coincident with the expected mid-plane condensation fronts of water ice, ammonia or water-ammonia hydrates, and water-clatherates (with CO2, methane, CO and N2). The 63 AU dip is much wider than the first two and the full extent of the dip also covers the condensation front of pure CO2. The spectral index map of HL Tau between 233 and 343 GHz shows that the flux ratios inside the dip regions are statistically larger than that of nearby regions in the disk. The variation can be explained by a model with two dust populations where most of dust mass resides in the population which has grown into decimeter size scales inside the dips.

  17. Treatment bed microbiological control

    NASA Technical Reports Server (NTRS)

    Janauer, Gilbert E.; Fitzpatrick, Timothy W.; Kril, Michael B.; Wilber, Georgia A.; Sauer, Richard L.

    1987-01-01

    The effects of microbial fouling on treatment bed (TB) performance are being studied. Fouling of activated carbon (AC) and ion exchange resins (IEX) by live and devitalized bacteria can cause decreased capacity for selected sorbates with AC and IEX TB. More data are needed on organic species removal in the trace region of solute sorption isotherms. TB colonization was prevented by nonclassical chemical disinfectant compositions (quaternary ammonium resins) applied in suitable configurations. Recently, the protection of carbon beds via direct disinfectant impregnation has shown promise. Effects (of impregnation) upon bed sorption/removal characteristics are to be studied with representative contaminants. The potential need to remove solutes added or produced during water disinfection and/or TB microbiological control must be investigated.

  18. Fluidized bed coal desulfurization

    NASA Technical Reports Server (NTRS)

    Ravindram, M.

    1983-01-01

    Laboratory scale experiments were conducted on two high volatile bituminous coals in a bench scale batch fluidized bed reactor. Chemical pretreatment and posttreatment of coals were tried as a means of enhancing desulfurization. Sequential chlorination and dechlorination cum hydrodesulfurization under modest conditions relative to the water slurry process were found to result in substantial sulfur reductions of about 80%. Sulfur forms as well as proximate and ultimate analyses of the processed coals are included. These studies indicate that a fluidized bed reactor process has considerable potential for being developed into a simple and economic process for coal desulfurization.

  19. Rancho flotation bed.

    PubMed

    Reswick, J B; Nickel, V L; Simoes, N

    1977-04-01

    The Rancho Flotation Bed provides hydrostatic support with maximum pressures over bony prominences of 15 to 25 mm Hg (measured with a pneumatic pressure transducer). This is generally below the levels normally quoted as conducive to the development of ischaemia. Clinical experience has shown the bed to be a successful aid to nursing by eliminating the need to turn the patients for pressure reasons, allowing patients with pressure sores to remain in a position which is more comfortable and more suitable for other nursing care. It also makes it easier for nurses to handle patients in order to care for the pressure sores. PMID:615987

  20. Staged fluidized bed

    DOEpatents

    Mallon, R.G.

    1983-05-13

    The invention relates to oil shale retorting and more particularly to staged fluidized bed oil shale retorting. Method and apparatus are disclosed for narrowing the distribution of residence times of any size particle and equalizing the residence times of large and small particles in fluidized beds. Particles are moved up one fluidized column and down a second fluidized column with the relative heights selected to equalize residence times of large and small particles. Additional pairs of columns are staged to narrow the distribution of residence times and provide complete processing of the material.

  1. Acoustic bed velocity and bed load dynamics in a large sand bed river

    USGS Publications Warehouse

    Gaeuman, D.; Jacobson, R.B.

    2006-01-01

    Development of a practical technology for rapid quantification of bed load transport in large rivers would represent a revolutionary advance for sediment monitoring and the investigation of fluvial dynamics. Measurement of bed load motion with acoustic Doppler current profiles (ADCPs) has emerged as a promising approach for evaluating bed load transport. However, a better understanding of how ADCP data relate to conditions near the stream bed is necessary to make the method practical for quantitative applications. In this paper, we discuss the response of ADCP bed velocity measurements, defined as the near-bed sediment velocity detected by the instrument's bottom-tracking feature, to changing sediment-transporting conditions in the lower Missouri River. Bed velocity represents a weighted average of backscatter from moving bed load particles and spectral reflections from the immobile bed. The ratio of bed velocity to mean bed load particle velocity depends on the concentration of the particles moving in the bed load layer, the bed load layer thickness, and the backscatter strength from a unit area of moving particles relative to the echo strength from a unit area of unobstructed bed. A model based on existing bed load transport theory predicted measured bed velocities from hydraulic and grain size measurements with reasonable success. Bed velocities become more variable and increase more rapidly with shear stress when the transport stage, defined as the ratio of skin friction to the critical shear stress for particle entrainment, exceeds a threshold of about 17. This transition in bed velocity response appears to be associated with the appearance of longer, flatter bed forms at high transport stages.

  2. Ceramic Solar Receiver

    NASA Technical Reports Server (NTRS)

    Robertson, C., Jr.

    1984-01-01

    Solar receiver uses ceramic honeycomb matrix to absorb heat from Sun and transfer it to working fluid at temperatures of 1,095 degrees and 1,650 degrees C. Drives gas turbine engine or provides heat for industrial processes.

  3. Light emitting ceramic device

    DOEpatents

    Valentine, Paul; Edwards, Doreen D.; Walker, Jr., William John; Slack, Lyle H.; Brown, Wayne Douglas; Osborne, Cathy; Norton, Michael; Begley, Richard

    2010-05-18

    A light-emitting ceramic based panel, hereafter termed "electroceramescent" panel, is herein claimed. The electroceramescent panel is formed on a substrate providing mechanical support as well as serving as the base electrode for the device. One or more semiconductive ceramic layers directly overlay the substrate, and electrical conductivity and ionic diffusion are controlled. Light emitting regions overlay the semiconductive ceramic layers, and said regions consist sequentially of a layer of a ceramic insulation layer and an electroluminescent layer, comprised of doped phosphors or the equivalent. One or more conductive top electrode layers having optically transmissive areas overlay the light emitting regions, and a multi-layered top barrier cover comprising one or more optically transmissive non-combustible insulation layers overlay said top electrode regions.

  4. Ceramic breeder materials

    SciTech Connect

    Johnson, C.E.

    1990-01-01

    The breeding blanket is a key component of the fusion reactor because it directly involves tritium breeding and energy extraction, both of which are critical to development of fusion power. The lithium ceramics continue to show promise as candidate breeder materials. This promise was recognized by the International Thermonuclear Reactor (ITER) design team in its selection of ceramics as the first option for the ITER breeder material. Blanket design studies have indicated properties in the candidate materials data base that need further investigation. Current studies are focusing on tritium release behavior at high burnup, changes in thermophysical properties with burnup, compatibility between the ceramic breeder and beryllium multiplier, and phase changes with burnup. Laboratory and in-reactor tests, some as part of an international collaboration for development of ceramic breeder materials, are underway. 32 refs., 1 fig., 1 tab.

  5. Corrosion resistant ceramic materials

    DOEpatents

    Kaun, Thomas D.

    1995-01-01

    Ceramic materials which exhibit stability in severely-corrosive environments having high alkali-metal activity, high sulfur/sulfide activity and/or molten halides at temperatures of 200.degree.-550.degree. C. or organic salt (including SO.sub.2 and SO.sub.2 Cl.sub.2) at temperatures of 25.degree.-200.degree. C. These sulfide ceramics form stoichiometric (single-phase) compounds with sulfides of Ca, Li, Na, K, Al, Mg, Si, Y, La, Ce, Ga, Ba, Zr and Sr and show melting-points that are sufficiently low and have excellent wettability with many metals (Fe, Ni, Mo) to easily form metal/ceramic seals. Ceramic compositions are also formulated to adequately match thermal expansion coefficient of adjacent metal components.

  6. Corrosion resistant ceramic materials

    DOEpatents

    Kaun, T.D.

    1996-07-23

    Ceramic materials are disclosed which exhibit stability in severely-corrosive environments having high alkali-metal activity, high sulfur/sulfide activity and/or molten halides at temperatures of 200--550 C or organic salt (including SO{sub 2} and SO{sub 2}Cl{sub 2}) at temperatures of 25--200 C. These sulfide ceramics form stoichiometric (single-phase) compounds with sulfides of Ca, Li, Na, K, Al, Mg, Si, Y, La, Ce, Ga, Ba, Zr and Sr and show melting-points that are sufficiently low and have excellent wettability with many metals (Fe, Ni, Mo) to easily form metal/ceramic seals. Ceramic compositions are also formulated to adequately match thermal expansion coefficient of adjacent metal components. 1 fig.

  7. Corrosion resistant ceramic materials

    DOEpatents

    Kaun, Thomas D.

    1996-01-01

    Ceramic materials which exhibit stability in severely-corrosive environments having high alkali-metal activity, high sulfur/sulfide activity and/or molten halides at temperatures of 200.degree.-550.degree. C. or organic salt (including SO.sub.2 and SO.sub.2 Cl.sub.2) at temperatures of 25.degree.-200.degree. C. These sulfide ceramics form stoichiometric (single-phase) compounds with sulfides of Ca, Li, Na, K, Al, Mg, Si, Y, La, Ce, Ga, Ba, Zr and Sr and show melting-points that are sufficiently low and have excellent wettability with many metals (Fe, Ni, Mo) to easily form metal/ceramic seals. Ceramic compositions are also formulated to adequately match thermal expansion coefficient of adjacent metal components.

  8. Super Thin Ceramic Coatings

    NASA Video Gallery

    New technology being developed at NASA's Glenn Research Center creates super thin ceramic coatings on engine components. The Plasma Spray – Physical Vapor Deposition (PS-PVD) rig uses a powerful ...

  9. Advanced Ceramics Property Measurements

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan; Helfinstine, John; Quinn, George; Gonczy, Stephen

    2013-01-01

    Mechanical and physical properties of ceramic bodies can be difficult to measure correctly unless the proper techniques are used. The Advanced Ceramics Committee of ASTM, C-28, has developed dozens of consensus test standards and practices to measure various properties of a ceramic monolith, composite, or coating. The standards give the "what, how, how not, and why" for measurement of many mechanical, physical, thermal, and performance properties. Using these standards will provide accurate, reliable, and complete data for rigorous comparisons with other test results from your test lab, or another. The C-28 Committee has involved academics, producers, and users of ceramics to write and continually update more than 45 standards since the committee's inception in 1986. Included in this poster is a pictogram of the C-28 standards and information on how to obtain individual copies with full details or the complete collection of standards in one volume.

  10. Making Ceramic Cameras

    ERIC Educational Resources Information Center

    Squibb, Matt

    2009-01-01

    This article describes how to make a clay camera. This idea of creating functional cameras from clay allows students to experience ceramics, photography, and painting all in one unit. (Contains 1 resource and 3 online resources.)

  11. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2002-04-01

    This report covers the following tasks: Task 1--Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints; Task 2--Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability; Task 3--Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres; Task 4--Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures; Task 5--Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability; and Task 6--Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  12. Apparatus for controlling fluidized beds

    DOEpatents

    Rehmat, A.G.; Patel, J.G.

    1987-05-12

    An apparatus and process are disclosed for control and maintenance of fluidized beds under non-steady state conditions. An ash removal conduit is provided for removing solid particulates from a fluidized bed separate from an ash discharge conduit in the lower portion of the grate supporting such a bed. The apparatus and process of this invention is particularly suitable for use in ash agglomerating fluidized beds and provides control of the fluidized bed before ash agglomeration is initiated and during upset conditions resulting in stable, sinter-free fluidized bed maintenance. 2 figs.

  13. Apparatus for controlling fluidized beds

    DOEpatents

    Rehmat, Amirali G.; Patel, Jitendra G.

    1987-05-12

    An apparatus and process for control and maintenance of fluidized beds under non-steady state conditions. An ash removal conduit is provided for removing solid particulates from a fluidized bed separate from an ash discharge conduit in the lower portion of the grate supporting such a bed. The apparatus and process of this invention is particularly suitable for use in ash agglomerating fluidized beds and provides control of the fluidized bed before ash agglomeration is initiated and during upset conditions resulting in stable, sinter-free fluidized bed maintenance.

  14. Fluid bed material transfer method

    DOEpatents

    Pinske, Jr., Edward E.

    1994-01-01

    A fluidized bed apparatus comprising a pair of separated fluid bed enclosures, each enclosing a fluid bed carried on an air distributor plate supplied with fluidizing air from below the plate. At least one equalizing duct extending through sidewalls of both fluid bed enclosures and flexibly engaged therewith to communicate the fluid beds with each other. The equalizing duct being surrounded by insulation which is in turn encased by an outer duct having expansion means and being fixed between the sidewalls of the fluid bed enclosures.

  15. Distributor for multistage fluidized beds

    SciTech Connect

    Wormser, A.

    1992-06-16

    This patent describes a multibed fluidized bed system. It comprises a fluidized bed vessel having a casing surrounding a first distributor and a second distributor downstream from the first distributor; a first bed material placed on the first distributor and a second bed material placed on the second distributor; each of the bed materials having an angle of repose; and wherein the angle formed by the substantially straight elongated tubular passages and the upper surface is less than the angle of repose of the second bed material.

  16. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-07-01

    This is the fourth quarterly report on a new study to develop a ceramic membrane/metal joint. The first experiments using the La-Sr-Fe-O ceramic are reported. Some of the analysis performed on the samples obtained are commented upon. A set of experiments to characterize the mechanical strength and thermal fatigue properties of the joints has been designed and begun. Finite element models of joints used to model residual stresses are described.

  17. Battery utilizing ceramic membranes

    DOEpatents

    Yahnke, Mark S.; Shlomo, Golan; Anderson, Marc A.

    1994-01-01

    A thin film battery is disclosed based on the use of ceramic membrane technology. The battery includes a pair of conductive collectors on which the materials for the anode and the cathode may be spin coated. The separator is formed of a porous metal oxide ceramic membrane impregnated with electrolyte so that electrical separation is maintained while ion mobility is also maintained. The entire battery can be made less than 10 microns thick while generating a potential in the 1 volt range.

  18. Technology test bed review

    NASA Astrophysics Data System (ADS)

    McConnaughey, H. V.

    1992-07-01

    The topics are presented in viewgraph form and include the following: (1) Space Shuttle Main Engine (SSME) technology test bed (TTB) history; (2) TTB objectives; (3) TTB major accomplishments; (4) TTB contributions to SSME; (5) major impacts of 3001 testing; (6) some challenges to computational fluid dynamics (CFD); (7) the high pressure fuel turbopump (HPFTP); and (8) 3001 lessons learned in design and operations.

  19. Bed rest during pregnancy

    MedlinePlus

    ... groups, bulletin boards, and chat rooms online for moms-to-be who are also on bed rest. Expect emotional ups and downs. Share your hopes and worries with your partner. Let each other vent if needed. If sex is not allowed, look for other ways to ...

  20. EXPANDED BED BIOLOGICAL TREATMENT

    EPA Science Inventory

    A three-year pilot-scale research investigation at the EPA Lebanon Pilot Plant was conducted to evaluate the feasibility of a unique biological secondary treatment process, designated the Expanded Bed Biological Treatment Process (EBBT). The EBBT process is a three-phase (oxygen/...

  1. Alumina-based ceramic composite

    DOEpatents

    Alexander, K.B.; Tiegs, T.N.; Becher, P.F.; Waters, S.B.

    1996-07-23

    An improved ceramic composite comprising oxide ceramic particulates, nonoxide ceramic particulates selected from the group consisting of carbides, borides, nitrides of silicon and transition metals and mixtures thereof, and a ductile binder selected from the group consisting of metallic, intermetallic alloys and mixtures thereof is described. The ceramic composite is made by blending powders of the ceramic particulates and the ductile to form a mixture and consolidating the mixture of under conditions of temperature and pressure sufficient to produce a densified ceramic composite. 5 figs.

  2. Ceramic electrolyte coating and methods

    DOEpatents

    Seabaugh, Matthew M.; Swartz, Scott L.; Dawson, William J.; McCormick, Buddy E.

    2007-08-28

    Aqueous coating slurries useful in depositing a dense coating of a ceramic electrolyte material (e.g., yttrium-stabilized zirconia) onto a porous substrate of a ceramic electrode material (e.g., lanthanum strontium manganite or nickel/zirconia) and processes for preparing an aqueous suspension of a ceramic electrolyte material and an aqueous spray coating slurry including a ceramic electrolyte material. The invention also includes processes for depositing an aqueous spray coating slurry including a ceramic electrolyte material onto pre-sintered, partially sintered, and unsintered ceramic substrates and products made by this process.

  3. Clinical application of bio ceramics

    NASA Astrophysics Data System (ADS)

    Anu, Sharma; Gayatri, Sharma

    2016-05-01

    Ceramics are the inorganic crystalline material. These are used in various field such as biomedical, electrical, electronics, aerospace, automotive and optical etc. Bio ceramics are the one of the most active areas of research. Bio ceramics are the ceramics which are biocompatible. The unique properties of bio ceramics make them an attractive option for medical applications and offer some potential advantages over other materials. During the past three decades, a number of major advances have been made in the field of bio ceramics. This review focuses on the use of these materials in variety of clinical scenarios.

  4. Moving Granular Bed Filter Development Program

    SciTech Connect

    Wilson, K.B.; Haas, J.C.; Gupta, R.P.; Turk, B.S.

    1996-12-31

    For coal-fired power plants utilizing a gas turbine, the removal of ash particles is necessary to protect the turbine and to meet emission standards. Advantages are also evident for a filter system that can remove other coal-derived contaminants such as alkali, halogens, and ammonia. With most particulates and other contaminants removed, erosion and corrosion of turbine materials, as well as deposition of particles within the turbine, are reduced to acceptable levels. The granular bed filter is suitable for this task in a pressurized gasification or combustion environment. The objective of the base contract was to develop conceptual designs of moving granular bed filter (GBF) and ceramic candle filter technologies for control of particles from integrated gasification combined cycle (IGCC), pressurized fluidized-bed combustion (PFBC), and direct coal-fueled turbine (DCFT) systems. The results of this study showed that the GBF design compared favorably with the candle filter. Three program options followed the base contract. The objective of Option I, Component Testing, was to identify and resolve technical issues regarding GBF development for IGCC and PFBC environments. This program was recently completed. The objective of Option II, Filter Proof Tests, is to test and evaluate the moving GBF system at a government-furnished hot-gas cleanup test facility. This facility is located at Southern Company Services (SCS), Inc., Wilsonville, Alabama. The objective of Option III, Multicontaminant Control Using a GBF, is to develop a chemically reactive filter material that will remove particulates plus one or more of the following coal-derived contaminants: alkali, halogens, and ammonia.

  5. [Ceramic-on-ceramic bearings in total hip arthroplasty (THA)].

    PubMed

    Sentürk, U; Perka, C

    2015-04-01

    The main reason for total hip arthroplasty (THA) revision is the wear-related aseptic loosening. Younger and active patients after total joint replacement create high demands, in particular, on the bearings. The progress, especially for alumina ceramic-on-ceramic bearings and mixed ceramics have solved many problems of the past and lead to good in vitro results. Modern ceramics (alumina or mixed ceramics containing alumina) are extremely hard, scratch-resistant, biocompatible, offer a low coefficient of friction, superior lubrication and have the lowest wear rates in comparison to all other bearings in THA. The disadvantage of ceramic is the risk of material failure, i.e., of ceramic fracture. The new generation of mixed ceramics (delta ceramic), has reduced the risk of head fractures to 0.03-0.05 %, but the risk for liner fractures remains unchanged at about 0.02 %. Assuming a non-impinging component implantation, ceramic-on-ceramic bearings have substantial advantages over all other bearings in THA. Due to the superior hardness, ceramic bearings produce less third body wear and are virtually impervious to damage from instruments during the implantation process. A specific complication for ceramic-on-ceramic bearings is "squeaking". The high rate of reported squeaking (0.45 to 10.7 %) highlights the importance of precise implant positioning and the stem and patient selection. With precise implant positioning this problem is rare with many implant designs and without clinical relevance. The improved tribology and the presumable resulting implant longevity make ceramic-on-ceramic the bearing of choice for young and active patients. PMID:25874400

  6. An orientation soil survey at the Pebble Cu-Au-Mo porphyry deposit, Alaska

    USGS Publications Warehouse

    Smith, Steven M.; Eppinger, Robert G.; Fey, David L.; Kelley, Karen D., (Edited By); Giles, S.A.

    2009-01-01

    Soil samples were collected in 2007 and 2008 along three traverses across the giant Pebble Cu-Au-Mo porphyry deposit. Within each soil pit, four subsamples were collected following recommended protocols for each of ten commonly-used and proprietary leach/digestion techniques. The significance of geochemical patterns generated by these techniques was classified by visual inspection of plots showing individual element concentration by each analytical method along the 2007 traverse. A simple matrix by element versus method, populated with a value based on the significance classification, provides a method for ranking the utility of methods and elements at this deposit. The interpretation of a complex multi-element dataset derived from multiple analytical techniques is challenging. An example of vanadium results from a single leach technique is used to illustrate the several possible interpretations of the data.

  7. Building massive, tightly packed planetary systems by in-situ accretion of pebbles

    NASA Astrophysics Data System (ADS)

    Moriarty, John; Fischer, Debra

    2015-01-01

    The distribution of mass in planetary systems is one of the most important constraints available for understanding the process of planet formation. One particularly interesting observation is the large number of super-Earth sized planets in short period orbits and tightly packed systems. The amount of mass in these systems is about ten times what would be expected if they had surface density disributions similar to the solar system (i.e. the minimum mass solar nebula) extrapolated inwards of half an AU. This observation raises the question: how and when did all that mass get there? In this work we explore the idea that the radial drift and eventual accretion of small, centimeter sized pebbles leads to massive inner planetary systems.

  8. Piezoelectric Ceramics and Their Applications

    ERIC Educational Resources Information Center

    Flinn, I.

    1975-01-01

    Describes the piezoelectric effect in ceramics and presents a quantitative representation of this effect. Explains the processes involved in the manufacture of piezoelectric ceramics, the materials used, and the situations in which they are applied. (GS)

  9. Fundamental tribological properties of ceramics

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.; Miyoshi, K.

    1985-01-01

    When a ceramic is brought into contact with itself, another ceramic, or a metal, strong bond forces can develop between the materials. Adhesion between a ceramic and itself or another solid are discussed from a theoretical consideration of the nature of the surfaces and experimentally by relating bond forces to the interface resulting from solid state contact. Elastic, plastic, and fracture behavior of ceramics in solid-state contact are discussed as they relate to friction and wear. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as with metals. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Lubrication is found to increase the critical load necessary to initiate fracture of ceramics with sliding or rubbing contact.

  10. Microstructure and properties of ceramics

    NASA Technical Reports Server (NTRS)

    Hamano, K.

    1984-01-01

    The history of research into the microstructure and properties of ceramic ware is discussed; methods of producing ceramics with particular characteristics are investigated. Bubbles, sintering, cracks, and electron microscopy are discussed.

  11. Ceramic microstructure and adhesion

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1984-01-01

    When a ceramic is brought into contact with a ceramic, a polymer, or a metal, strong bond forces can develop between the materials. The bonding forces will depend upon the state of the surfaces, cleanliness and the fundamental properties of the two solids, both surface and bulk. Adhesion between a ceramic and another solid are discussed from a theoretical consideration of the nature of the surfaces and experimentally by relating bond forces to interface resulting from solid state contact. Surface properties of ceramics correlated with adhesion include, orientation, reconstruction and diffusion as well as the chemistry of the surface specie. Where a ceramic is in contact with a metal their interactive chemistry and bond strength is considered. Bulk properties examined include elastic and plastic behavior in the surficial regions, cohesive binding energies, crystal structures and crystallographic orientation. Materials examined with respect to interfacial adhesive interactions include silicon carbide, nickel zinc ferrite, manganese zinc ferrite, and aluminum oxide. The surfaces of the contacting solids are studied both in the atomic or molecularly clean state and in the presence of selected surface contaminants.

  12. Ceramic impregnated superabrasives

    DOEpatents

    Radtke, Robert P.; Sherman, Andrew

    2009-02-10

    A superabrasive fracture resistant compact is formed by depositing successive layers of ceramic throughout the network of open pores in a thermally stable self-bonded polycrystalline diamond or cubic boron nitride preform. The void volume in the preform is from approximately 2 to 10 percent of the volume of the preform, and the average pore size is below approximately 3000 nanometers. The preform is evacuated and infiltrated under at least about 1500 pounds per square inch pressure with a liquid pre-ceramic polymerizable precursor. The precursor is infiltrated into the preform at or below the boiling point of the precursor. The precursor is polymerized into a solid phase material. The excess is removed from the outside of the preform, and the polymer is pyrolized to form a ceramic. The process is repeated at least once more so as to achieve upwards of 90 percent filling of the original void volume. When the remaining void volume drops below about 1 percent the physical properties of the compact, such as fracture resistance, improve substantially. Multiple infiltration cycles result in the deposition of sufficient ceramic to reduce the void volume to below 0.5 percent. The fracture resistance of the compacts in which the pores are lined with formed in situ ceramic is generally at least one and one-half times that of the starting preforms.

  13. Ceramic combustor mounting

    DOEpatents

    Hoffman, Melvin G.; Janneck, Frank W.

    1982-01-01

    A combustor for a gas turbine engine includes a metal engine block including a wall portion defining a housing for a combustor having ceramic liner components. A ceramic outlet duct is supported by a compliant seal on the metal block and a reaction chamber liner is stacked thereon and partly closed at one end by a ceramic bypass swirl plate which is spring loaded by a plurality of circumferentially spaced, spring loaded guide rods and wherein each of the guide rods has one end thereof directed exteriorly of a metal cover plate on the engine block to react against externally located biasing springs cooled by ambient air and wherein the rod spring support arrangement maintains the stacked ceramic components together so that a normal force is maintained on the seal between the outlet duct and the engine block under all operating conditions. The support arrangement also is operative to accommodate a substantial difference in thermal expansion between the ceramic liner components of the combustor and the metal material of the engine block.

  14. FATIGUE OF DENTAL CERAMICS

    PubMed Central

    Zhang, Yu; Sailer, Irena; Lawn, Brian R

    2013-01-01

    Objectives Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics. Data/sources The nature of various fatigue modes is elucidated using fracture test data on ceramic layer specimens from the dental and biomechanics literature. Conclusions Failure modes can change over a lifetime, depending on restoration geometry, loading conditions and material properties. Modes that operate in single-cycle loading may be dominated by alternative modes in multi-cycle loading. While post-mortem examination of failed prostheses can determine the sources of certain fractures, the evolution of these fractures en route to failure remains poorly understood. Whereas it is commonly held that loss of load-bearing capacity of dental ceramics in repetitive loading is attributable to chemically-assisted 'slow crack growth' in the presence of water, we demonstrate the existence of more deleterious fatigue mechanisms, mechanical rather than chemical in nature. Neglecting to account for mechanical fatigue can lead to gross overestimates in predicted survival rates. Clinical significance Strategies for prolonging the clinical lifetimes of ceramic restorations are proposed based on a crack-containment philosophy. PMID:24135295

  15. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-10-01

    This is the third quarterly report on oxygen Transport Ceramic Membranes. In the following, the report describes the progress made by our university partners in Tasks 1 through 6, experimental apparatus that was designed and built for various tasks of this project, thermodynamic calculations, where applicable and work planned for the future. (Task 1) Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. (Task 2) Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. (Task 3) Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. (Task 4) Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. (Task 5) Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. (Task 6) Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  16. Capture of alkali during pressurized fluidized-bed combustion using in-bed sorbents

    SciTech Connect

    Mann, M.D.; Ludlow, D.K.

    1997-12-31

    The primary focus of this research was the removal of alkali from PFBC flue gases to a level specified by turbine manufactures. The target level was less than 24 ppbw. Several of the aluminosilicate minerals have the potential to capture alkalis, especially sodium and potassium, under conditions typical of fluid-bed operation. Other goals of this work were to investigate the potential for simultaneously removing SO{sub 2} and Cl from the PFBC gas stream. The initial work focused primarily on one class of sorbents, sodalites, with the goal of determining whether sodalites can be used as an in-bed sorbent to simultaneously remove alkali and sulfur. Thermo gravimetric analysis (TGA) was used to study the mechanism of alkali capture using sodalite. Further testing was performed on a 7.6 cm (3-in.)-diameter pressurized fluid-bed reactor (PFBR). Early results indicated that simultaneous removal of alkali and sulfur and/or chlorine was not practical under the conditions for commercial PFBC operations. Therefore, the focus of the latter part of this work was on sorbents that have been shown to capture alkali in other systems. The effectiveness of bauxite and kaolinite to reduce vapor-phase alkali concentrations was determined. In addition to studying the gettering capability of the sorbent, the impact of the getter on operational performance was evaluated. This evaluation included examining potential agglomeration of bed particles, deposition on heat-transfer surfaces, and the bridging and blinding of ceramic candle filters. The focus of this paper is on the work performed on the PFBR.

  17. Fluidized-bed combustion

    SciTech Connect

    Botros, P E

    1990-04-01

    This report describes the activities of the Morgantown Energy Technology Center's research and development program in fluidized-bed combustion from October 1, 1987, to September 30, 1989. The Department of Energy program involves atmospheric and pressurized systems. Demonstrations of industrial-scale atmospheric systems are being completed, and smaller boilers are being explored. These systems include vortex, multi-solid, spouted, dual-sided, air-cooled, pulsed, and waste-fired fluidized-beds. Combustion of low-rank coal, components, and erosion are being studied. In pressurized combustion, first-generation, combined-cycle power plants are being tested, and second-generation, advanced-cycle systems are being designed and cost evaluated. Research in coal devolatilization, metal wastage, tube corrosion, and fluidization also supports this area. 52 refs., 24 figs., 3 tabs.

  18. Lightweight ceramic insulation and method

    NASA Technical Reports Server (NTRS)

    Green, David J. (Inventor)

    1990-01-01

    A process is disclosed for manufacturing a low density ceramic powder which can be formed to make a lightweight material for insulation or other construction. The ceramic product made from the process has a final density of less than 25 to about 1 percent of the theoretical weight of the ceramic powder. The ceramic product is lightweight and can be made to withstand high temperatures greater than 1400 C.

  19. Nondestructive evaluation of advanced ceramics

    NASA Technical Reports Server (NTRS)

    Klima, Stanley J.; Kautz, Harold E.

    1988-01-01

    A review is presented of Lewis Research Center efforts to develop nondestructive evaluation techniques for characterizing advanced ceramic materials. Various approaches involved the use of analytical ultrasonics to characterize monolythic ceramic microstructures, acousto-ultrasonics for characterizing ceramic matrix composites, damage monitoring in impact specimens by microfocus X-ray radiography and scanning ultrasonics, and high resolution computed X-ray tomography to identify structural features in fiber reinforced ceramics.

  20. Ceramic Automotive Stirling Engine Program

    SciTech Connect

    Not Available

    1986-08-01

    The Ceramic Automotive Stirling Engine Program evaluated the application of advanced ceramic materials to an automotive Stirling engine. The objective of the program was to evaluate the technical feasibility of utilizing advanced ceramics to increase peak engine operating temperature, and to evaluate the performance benefits of such an increase. Manufacturing cost estimates were also developed for various ceramic engine components and compared with conventional metallic engine component costs.

  1. Ceramic automotive Stirling engine program

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The Ceramic Automotive Stirling Engine Program evaluated the application of advanced ceramic materials to an automotive Stirling engine. The objective of the program was to evaluate the technical feasibility of utilizing advanced ceramics to increase peak engine operating temperature, and to evaluate the performance benefits of such an increase. Manufacturing cost estimates were also developed for various ceramic engine components and compared with conventional metallic engine component costs.

  2. Combustion in fluidized beds

    SciTech Connect

    Dry, F.J.; La Nauze, R.D. )

    1990-07-01

    Circulating fluidized-bed (CFB) combustion systems have become popular since the late 1970s, and, given the current level of activity in the area,it is clear that this technology has a stable future in the boiler market. For standard coal combustion applications, competition is fierce with mature pulverized-fuel-based (PF) technology set to maintain a strong profile. CFB systems, however, can be more cost effective than PF systems when emission control is considered, and, as CFB technology matures, it is expected that an ever-increasing proportion of boiler installations will utilize the CFB concept. CFB systems have advantages in the combustion of low-grade fuels such as coal waste and biomass. In competition with conventional bubbling beds, the CFB boiler often demonstrates superior carbon burn-out efficiency. The key to this combustion technique is the hydrodynamic behavior of the fluidized bed. This article begins with a description of the fundamental fluid dynamic behavior of the CFB system. This is followed by an examination of the combustion process in such an environment and a discussion of the current status of the major CFB technologies.

  3. Ceramic tamper-revealing seals

    DOEpatents

    Kupperman, D.S.; Raptis, A.C.; Sheen, S.H.

    1992-12-08

    A flexible metal or ceramic cable is described with composite ceramic ends, or a U-shaped ceramic connecting element attached to a binding element plate or block cast from alumina or zirconium, and connected to the connecting element by shrink fitting. 7 figs.

  4. Assessment of ceramic membrane filters

    SciTech Connect

    Ahluwalia, R.K.; Geyer, H.K.; Im, K.H.

    1995-08-01

    The objectives of this project include the development of analytical models for evaluating the fluid mechanics of membrane coated, dead-end ceramic filters, and to determine the effects of thermal and thermo-chemical aging on the material properties of emerging ceramic hot gas filters. A honeycomb cordierite monolith with a thin ceramic coating and a rigid candle filter were evaluated.

  5. Ceramic coatings on smooth surfaces

    NASA Technical Reports Server (NTRS)

    Miller, R. A. (Inventor); Brindley, W. J. (Inventor); Rouge, C. J. (Inventor)

    1991-01-01

    A metallic coating is plasma sprayed onto a smooth surface of a metal alloy substitute or on a bond coating. An initial thin ceramic layer is low pressure sprayed onto the smooth surface of the substrate or bond coating. Another ceramic layer is atmospheric plasma sprayed onto the initial ceramic layer.

  6. Ceramic regenerator program

    NASA Technical Reports Server (NTRS)

    Franklin, Jerrold E.

    1991-01-01

    The feasibility of fabricating an Air Turbo Ramjet (ATR) regenerator containing intricate hydraulic passages from a ceramic material in order to allow operation with high temperature combustion gas and to reduce weight as compared with metallic materials was demonstrated. Platelet technology, ceramic tape casting, and multilayer ceramic packaging techniques were used in this fabrication of subscale silicon nitride components. Proof-of-concept demonstrations were performed to simulate a methane cooled regenerator for an ATR engine. The regenerator vane was designed to operate at realistic service conditions, i.e., 600 psi in a 3500 R (3040 F), 500 fps combustion gas environment. A total of six regenerators were fabricated and tested. The regenerators were shown to be able to withstand internal pressurization to 1575 psi. They were subjected to testing in 500 fps, 3560 R (3100 F) air/propane combustion products and were operated satisfactorily for an excess of 100 hr and 40 thermal cycles which exceeded 2460 R (2000 F).

  7. Whisker reinforced glass ceramic

    SciTech Connect

    Hirschfeld, D.A.; Brown, J.J. Jr.

    1996-06-03

    The process for making an in-situ whisker reinforced glass-ceramic that is up to 1.5 times as strong as conventional glass-ceramics was developed at Virginia Tech and patented in 1993. This technology has been identified as having commercial potential for use in high temperature heat exchanger applications for the electric power generation field by the National Center for Appropriate Technology (NCAT). This technology was licensed by MATVA, Inc., a small Virginia business, for further development. In particular, the goal of this project was to develop a property database and conduct initial testing of heat exchanger prototypes to demonstrate its potential application. This final report describes how the glass precursor was formed, physical properties of the glass-ceramic, techniques for making heat exchanger prototypes.

  8. Erosion of composite ceramics

    SciTech Connect

    Routbort, J.L.

    1992-08-01

    The theoretical basis to describe solid-particle erosion of monolithic ceramics is well developed. In many cases, the models can account for the impact velocity, impact angle and erodent-size dependencies of the steady-state erosion rate. In addition, the models account for effects of materials parameters such as fracture toughness and hardness. Steady-state erosion measurements on a wide variety of composite ceramics, including SiC whisker-reinforced Al{sub 2}O{sub 3}, Si{sub 3}N{sub 4} containing Si{sub 3}N{sub 4} or SiC whiskers, Y{sub 2}O{sub 3}-stabilized ZrO{sub 2} reinforced with SiC whiskers, and duplex-microstructure Si{sub 3}N{sub 4} have been reported. The theories developed for monolithic ceramics are, however, less successful in describing the results for composites.

  9. Erosion of composite ceramics

    SciTech Connect

    Routbort, J.L.

    1992-08-01

    The theoretical basis to describe solid-particle erosion of monolithic ceramics is well developed. In many cases, the models can account for the impact velocity, impact angle and erodent-size dependencies of the steady-state erosion rate. In addition, the models account for effects of materials parameters such as fracture toughness and hardness. Steady-state erosion measurements on a wide variety of composite ceramics, including SiC whisker-reinforced Al[sub 2]O[sub 3], Si[sub 3]N[sub 4] containing Si[sub 3]N[sub 4] or SiC whiskers, Y[sub 2]O[sub 3]-stabilized ZrO[sub 2] reinforced with SiC whiskers, and duplex-microstructure Si[sub 3]N[sub 4] have been reported. The theories developed for monolithic ceramics are, however, less successful in describing the results for composites.

  10. Ceramic vane drive joint

    DOEpatents

    Smale, Charles H.

    1981-01-01

    A variable geometry gas turbine has an array of ceramic composition vanes positioned by an actuating ring coupled through a plurality of circumferentially spaced turbine vane levers to the outer end of a metallic vane drive shaft at each of the ceramic vanes. Each of the ceramic vanes has an end slot of bow tie configuration including flared end segments and a center slot therebetween. Each of the vane drive shafts has a cross head with ends thereof spaced with respect to the sides of the end slot to define clearance for free expansion of the cross head with respect to the vane and the cross head being configured to uniformly distribute drive loads across bearing surfaces of the vane slot.

  11. Moving Bed Granular Bed Filter Development Program. Topical report, September 1994

    SciTech Connect

    Haas, J.C.; Prudhomme, J.W.; Wilson, K.W.

    1994-09-01

    Five test arrangements have been designed to support the Granular Bed Filter Development Program as defined in the Test Plan. The first arrangement is a 3.6 ft. diameter half filter, with a glass covering along the cross section to allow visual examination of the granular alumina material passing through the filter. The second test arrangement is a 3.6 ft diameter full size filter having refractory lining to simulate actual surface roughness conditions. The third test arrangement will examine filter geometry scale up by testing a 6.0 ft. diameter full size filter. The fourth Test Arrangement consists of a small 12 inch diameter fluidizer to measure the minimum fluidization velocity of the 7 m (approx. size) alumina material to be used in the filter assemblies. The last Test Unit is used to evaluation relative abrasion characteristics of potential refractory and ceramic materials to be installed in high abrasion areas in the pneumatic transport piping.

  12. Supported microporous ceramic membranes

    DOEpatents

    Webster, E.; Anderson, M.

    1993-12-14

    A method for the formation of microporous ceramic membranes onto a porous support includes placing a colloidal suspension of metal or metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane useful for ultrafiltration, reverse osmosis, or molecular sieving having mean pore sizes less than 100 Angstroms. 4 figures.

  13. Supported microporous ceramic membranes

    DOEpatents

    Webster, Elizabeth; Anderson, Marc

    1993-01-01

    A method for permformation of microporous ceramic membranes onto a porous support includes placing a colloidal suspension of metal or metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane useful for ultrafiltration, reverse osmosis, or molecular sieving having mean pore sizes less than 100 Angstroms.

  14. Performance of Dental Ceramics

    PubMed Central

    Rekow, E.D.; Silva, N.R.F.A.; Coelho, P.G.; Zhang, Y.; Guess, P.; Thompson, V.P.

    2011-01-01

    The clinical success of modern dental ceramics depends on an array of factors, ranging from initial physical properties of the material itself, to the fabrication and clinical procedures that inevitably damage these brittle materials, and the oral environment. Understanding the influence of these factors on clinical performance has engaged the dental, ceramics, and engineering communities alike. The objective of this review is to first summarize clinical, experimental, and analytic results reported in the recent literature. Additionally, it seeks to address how this new information adds insight into predictive test procedures and reveals challenges for future improvements. PMID:21224408

  15. Environment Conscious Ceramics (Ecoceramics)

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay; Levine, Stanley R. (Technical Monitor)

    2000-01-01

    Environment conscious ceramics (Ecoceramics) are a new class of materials, which can be produced with renewable natural resources (wood) or wood wastes (wood sawdust). Silicon carbide-based ecoceramics have been fabricated by reactive infiltration of carbonaceous preforms by molten silicon or silicon-refractory metal alloys. These carbonaceous preforms have been fabricated by pyrolysis of solid wood bodies at 1000 C. The fabrication approach, microstructure, and mechanical properties of SiC-based ecoceramics are presented. Ecoceramics have tailorable properties and behave like ceramic materials manufactured by conventional approaches.

  16. Ceramic component for electrodes

    DOEpatents

    Marchant, David D.

    1979-01-01

    A ceramic component suitable for preparing MHD generator electrodes consists of HfO.sub.2 and sufficient Tb.sub.4 O.sub.7 to stabilize at least 60 volume percent of the HfO.sub.2 into the cubic structure. The ceramic component may also contain a small amount of PrO.sub.2, Yb.sub.2 O.sub.3 or a mixture of both to improve stability and electronic conductivity of the electrode. The component is highly resistant to corrosion by molten potassium seed and molten coal slag in the MHD fluid and exhibits both ionic and electronic conductivity.

  17. Ceramic powder compaction

    SciTech Connect

    Glass, S.J.; Ewsuk, K.G.; Mahoney, F.M.

    1995-12-31

    With the objective of developing a predictive model for ceramic powder compaction we have investigated methods for characterizing density gradients in ceramic powder compacts, reviewed and compared existing compaction models, conducted compaction experiments on a spray dried alumina powder, and conducted mechanical tests and compaction experiments on model granular materials. Die filling and particle packing, and the behavior of individual granules play an important role in determining compaction behavior and should be incorporated into realistic compaction models. These results support the use of discrete element modeling techniques and statistical mechanics principals to develop a comprehensive model for compaction, something that should be achievable with computers with parallel processing capabilities.

  18. Ceramic breeder materials

    SciTech Connect

    Johnson, C.E.; Kummerer, K.R.; Roth, E.

    1987-01-01

    Ceramic materials are under investigation as potential breeder material in fusion reactors. This paper will review candidate materials with respect to fabrication routes and characterization, properties in as-fabricated and irradiated condition, and experimental results from laboratory and inpile investigations on tritium transport and release. Also discussed are the resources of beryllium, which is being considered as a neutron multiplier. The comparison of ceramic properties that is attempted here aims at the identification of the most-promising material for use in a tritium breeding blanket. 82 refs., 12 figs., 5 tabs.

  19. Battery utilizing ceramic membranes

    DOEpatents

    Yahnke, M.S.; Shlomo, G.; Anderson, M.A.

    1994-08-30

    A thin film battery is disclosed based on the use of ceramic membrane technology. The battery includes a pair of conductive collectors on which the materials for the anode and the cathode may be spin coated. The separator is formed of a porous metal oxide ceramic membrane impregnated with electrolyte so that electrical separation is maintained while ion mobility is also maintained. The entire battery can be made less than 10 microns thick while generating a potential in the 1 volt range. 2 figs.

  20. Microwave sintering of ceramics

    SciTech Connect

    Snyder, W.B.

    1989-01-01

    Successful adaptation of microwave heating to the densification of ceramic materials require a marriage of microwave and materials technologies. Using an interdisciplinary team of microwave and materials engineers, we have successfully demonstrated the ability to density ceramic materials over a wide range of temperatures. Microstructural evolution during microwave sintering has been found to be significantly different from that observed in conventional sintering. Our results and those of others indicate that microwave sintering has the potential to fabricate components to near net shape with mechanical properties equivalent to hot pressed or hot isostatically pressed material. 6 refs., 11 figs.

  1. High power density reactors based on direct cooled particle beds

    SciTech Connect

    Powell, J.R.; Horn, F.L.

    1985-01-01

    Reactors based on direct cooled HTGR type particle fuel are described. The small diameter particle fuel is packed between concentric porous cylinders to make annular fuel elements, with the inlet coolant gas flowing inwards. Hot exit gas flows out long the central channel of each element. Because of the very large heat transfer area in the packed beds, power densities in particle bed reactors (PBR's) are extremely high resulting in compact, lightweight systems. Coolant exit temperatures are high, because of the ceramic fuel temperature capabilities, and the reactors can be ramped to full power and temperature very rapidly. PBR systems can generate very high burst power levels using open cycle hydrogen coolant, or high continuous powers using closed cycle helium coolant. PBR technology is described and development requirements assessed. 12 figs.

  2. FILTER COMPONENT ASSESSMENT--CERAMIC CANDLES--

    SciTech Connect

    M.A. Alvin

    2004-04-23

    Efforts at Siemens Westinghouse Power Corporation (SWPC) have been focused on development of hot gas filter systems as an enabling technology for advanced coal and biomass-based gas turbine power generation applications. SWPC has been actively involved in the development of advanced filter materials and component configuration, has participated in numerous surveillance programs characterizing the material properties and microstructure of field tested filter elements, and has undertaken extended, accelerated filter life testing programs. This report summarizes the results of SWPC's filter component assessment efforts, identifying the performance and stability of porous monolithic, fiber reinforced, and filament wound ceramic hot gas candle filters, potentially for {ge}3 years of viable pressurized fluidized-bed combustion (PFBC) service operating life.

  3. Dimensionless critical shear stress in gravel-bed rivers

    NASA Astrophysics Data System (ADS)

    Petit, François; Houbrechts, Geoffrey; Peeters, Alexandre; Hallot, Eric; Van Campenhout, Jean; Denis, Anne-Cécile

    2015-12-01

    This paper first compiles critical shear stress values from 26 studies of gravel-bed rivers (GBRs) worldwide. The most frequently proposed value of the Shields criterion (θc) is 0.045, but three major groups with θc values ranging from < 0.030 to > 0.100 were identified. Second, dimensionless critical shear stresses (the Shields criterion) were evaluated for 14 GBRs (18 sites) with watershed areas ranging from 12 to 3000 km2. Different approaches were used to identify the initial movement of the bed material: painted and PIT-tag pebbles, sediment traps, and bedload samplers. The Shields criterion (θc) was estimated using the total shear stress (τ) and the grain shear stress (τ‧). Several shear stresses were also estimated using shear velocities. For bedload transport, we obtained an average Shields criterion (θc) of 0.040. The values were higher in small rivers (> 0.050) than larger rivers (< 0.030) because of more significant bedform shear stresses. The Shields criterion (θ‧c) was lower when the grain shear stress (τ‧) was used and only reached 0.019. Different values are also proposed in relation to the type of mobilization: the θc value for partial transport was ~ 0.025 and exceeded 0.040 for full transport (usually reached in association with discharges with a 10-year return period). The values based on the results of sediment traps and a bedload sampler were greater than those obtained using tracers, but these differences are smaller than those usually reported in the literature.

  4. Ceramic/ceramic total hip arthroplasty.

    PubMed

    Bizot, P; Nizard, R; Lerouge, S; Prudhommeaux, F; Sedel, L

    2000-01-01

    Alumina-on-alumina total hip arthroplasty has been used for 30 years, mainly in Europe. The theoretical advantages of this combination are represented by its remarkable sliding characteristics, its very low wear debris generation, and its sufficient fracture toughness. These advantages are achieved if the material is properly controlled with high density, high purity, and small grains. The authors summarize the results obtained with ceramic/ceramic total hip arthroplasty. Information is provided about in vivo behavior regarding wear debris characterization and quantification, and histological tissue examinations for inflammatory reactions, which were not encountered except when alumina debris was mixed with metal or cement. Modification of socket fixation resulted in improved clinical outcomes. With a press-fit metal shell and an alumina liner utilized for 10 years, the results are excellent especially in a young and active population. Alumina-on-alumina seems at the moment to be one of the best choices when a total hip arthroplasty has to be performed in young and active patients. PMID:11180930

  5. Tribological properties of structural ceramics

    NASA Technical Reports Server (NTRS)

    Buckley, Donald H.; Miyoshi, Kazuhisa

    1989-01-01

    The tribological and lubricated behavior of both oxide and nonoxide ceramics are reviewed in this chapter. Ceramics are examined in contact with themselves, other harder materials and metals. Elastic, plastic and fracture behavior of ceramics in solid state contact is discussed. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as has been observed with metals. Grit size effects in two and three body abrasive wear are observed for ceramics. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Surface contaminants affect friction and adhesive wear. For example, carbon on silicon carbide and chlorine on aluminum oxide reduce friction while oxygen on metal surfaces in contact with ceramics increases friction. Lubrication increases the critical load necessary to initiate fracture of ceramics both in indentation and with sliding or rubbing. Ceramics compositions both as coatings and in composites are described for the high temperature lubrication of both alloys and ceramics.

  6. Tribological properties of structural ceramics

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.; Miyoshi, K.

    1985-01-01

    The tribological and lubricated behavior of both oxide and nonoxide ceramics are reviewed in this chapter. Ceramics are examined in contact with themselves, other harder materials and metals. Elastic, plastic and fracture behavior of ceramics in solid state contact is discussed. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as has been observed with metals. Grit size effects in two and three body abrasive wear are observed for ceramics. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Surface contaminants affect friction and adhesive wear. For example, carbon on silicon carbide and chlorine on aluminum oxide reduce friction while oxygen on metal surfaces in contact with ceramics increases friction. Lubrication increases the critical load necessary to initiate fracture of ceramics both in indentation and with sliding or rubbing. Ceramics compositions both as coatings and in composites are described for the high temperature lubrication of both alloys and ceramics.

  7. Bed drain cover assembly for a fluidized bed

    DOEpatents

    Comparato, Joseph R.; Jacobs, Martin

    1982-01-01

    A loose fitting movable cover plate (36), suitable for the severe service encountered in a fluidized bed combustor (10), restricts the flow of solids into the combustor drain lines (30) during shutdown of the bed. This cover makes it possible to empty spent solids from the bed drain lines which would otherwise plug the piping between the drain and the downstream metering device. This enables use of multiple drain lines each with a separate metering device for the control of solids flow rate.

  8. Light-weight ceramic insulation

    NASA Technical Reports Server (NTRS)

    Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    2002-01-01

    Ultra-high temperature, light-weight, ceramic insulation such as ceramic tile is obtained by pyrolyzing a siloxane gel derived from the reaction of at least one organo dialkoxy silane and at least one tetralkoxy silane in an acid or base liquid medium. The reaction mixture of the tetra- and dialkoxy silanes may contain also an effective amount of a mono- or trialkoxy silane to obtain the siloxane gel. The siloxane gel is dried at ambient pressures to form a siloxane ceramic precursor without significant shrinkage. The siloxane ceramic precursor is subsequently pyrolyzed, in an inert atmosphere, to form the black ceramic insulation comprising atoms of silicon, carbon and oxygen. The ceramic insulation, can be characterized as a porous, uniform ceramic tile resistant to oxidation at temperatures ranging as high as 1700.degree. C. and is particularly useful as lightweight tiles for spacecraft and other high-temperature insulation applications.

  9. Metal to ceramic sealed joint

    DOEpatents

    Lasecki, J.V.; Novak, R.F.; McBride, J.R.

    1991-08-27

    A metal to ceramic sealed joint which can withstand wide variations in temperature and maintain a good seal is provided for use in a device adapted to withstand thermal cycling from about 20 to about 1000 degrees C. The sealed joint includes a metal member, a ceramic member having an end portion, and an active metal braze forming a joint to seal the metal member to the ceramic member. The joint is positioned remote from the end portion of the ceramic member to avoid stresses at the ends or edges of the ceramic member. The sealed joint is particularly suited for use to form sealed metal to ceramic joints in a thermoelectric generator such as a sodium heat engine where a solid ceramic electrolyte is joined to metal parts in the system. 11 figures.

  10. Metal to ceramic sealed joint

    DOEpatents

    Lasecki, John V.; Novak, Robert F.; McBride, James R.

    1991-01-01

    A metal to ceramic sealed joint which can withstand wide variations in temperature and maintain a good seal is provided for use in a device adapted to withstand thermal cycling from about 20 to about 1000 degrees C. The sealed joint includes a metal member, a ceramic member having an end portion, and an active metal braze forming a joint to seal the metal member to the ceramic member. The joint is positioned remote from the end portion of the ceramic member to avoid stresses at the ends or edges of the ceramic member. The sealed joint is particularly suited for use to form sealed metal to ceramic joints in a thermoelectric generator such as a sodium heat engine where a solid ceramic electrolyte is joined to metal parts in the system.

  11. Bed Rest Muscular Atrophy

    NASA Technical Reports Server (NTRS)

    Greenleaf, John E.

    2000-01-01

    A major debilitating response from prolonged bed rest (BR) is muscle atrophy, defined as a "decrease in size of a part of tissue after full development has been attained: a wasting away of tissue as from disuse, old age, injury or disease". Part of the complicated mechanism for the dizziness, increased body instability, and exaggerated gait in patients who arise immediately after BR may be a result of not only foot pain, but also of muscular atrophy and associated reduction in lower limb strength. Also, there seems to be a close association between muscle atrophy and bone atrophy. A discussion of many facets of the total BR homeostatic syndrome has been published. The old adage that use determines form which promotes function of bone (Wolff's law) also applies to those people exposed to prolonged BR (without exercise training) in whom muscle atrophy is a consistent finding. An extreme case involved a 16-year-old boy who was ordered to bed by his mother in 1932: after 50 years in bed he had "a lily-white frame with limbs as thin as the legs of a ladder-back chair". These findings emphasize the close relationship between muscle atrophy and bone atrophy. In addition to loss of muscle mass during deconditioning, there is a significant loss of muscle strength and a decrease in protein synthesis. Because the decreases in force (strength) are proportionately greater than those in fiber size or muscle cross-sectional area, other contributory factors must be involved; muscle fiber dehydration may be important.

  12. Coal Bed Methane Primer

    SciTech Connect

    Dan Arthur; Bruce Langhus; Jon Seekins

    2005-05-25

    During the second half of the 1990's Coal Bed Methane (CBM) production increased dramatically nationwide to represent a significant new source of income and natural gas for many independent and established producers. Matching these soaring production rates during this period was a heightened public awareness of environmental concerns. These concerns left unexplained and under-addressed have created a significant growth in public involvement generating literally thousands of unfocused project comments for various regional NEPA efforts resulting in the delayed development of public and fee lands. The accelerating interest in CBM development coupled to the growth in public involvement has prompted the conceptualization of this project for the development of a CBM Primer. The Primer is designed to serve as a summary document, which introduces and encapsulates information pertinent to the development of Coal Bed Methane (CBM), including focused discussions of coal deposits, methane as a natural formed gas, split mineral estates, development techniques, operational issues, producing methods, applicable regulatory frameworks, land and resource management, mitigation measures, preparation of project plans, data availability, Indian Trust issues and relevant environmental technologies. An important aspect of gaining access to federal, state, tribal, or fee lands involves education of a broad array of stakeholders, including land and mineral owners, regulators, conservationists, tribal governments, special interest groups, and numerous others that could be impacted by the development of coal bed methane. Perhaps the most crucial aspect of successfully developing CBM resources is stakeholder education. Currently, an inconsistent picture of CBM exists. There is a significant lack of understanding on the parts of nearly all stakeholders, including industry, government, special interest groups, and land owners. It is envisioned the Primer would being used by a variety of

  13. Biparticle fluidized bed reactor

    DOEpatents

    Scott, C.D.; Marasco, J.A.

    1995-04-25

    A fluidized bed reactor system utilizes a fluid phase, a retained fluidized primary particulate phase, and a migratory second particulate phase. The primary particulate phase is a particle such as a gel bead containing an immobilized biocatalyst. The secondary particulate phase, continuously introduced and removed in either cocurrent or countercurrent mode, acts in a secondary role such as a sorbent to continuously remove a product or by-product constituent from the fluid phase. Introduction and removal of the sorbent phase is accomplished through the use of feed screw mechanisms and multivane slurry valves. 3 figs.

  14. Biparticle fluidized bed reactor

    DOEpatents

    Scott, Charles D.; Marasco, Joseph A.

    1995-01-01

    A fluidized bed reactor system utilizes a fluid phase, a retained fluidized primary particulate phase, and a migratory second particulate phase. The primary particulate phase is a particle such as a gel bead containing an immobilized biocatalyst. The secondary particulate phase, continuously introduced and removed in either cocurrent or countercurrent mode, acts in a secondary role such as a sorbent to continuously remove a product or by-product constituent from the fluid phase. Introduction and removal of the sorbent phase is accomplished through the use of feed screw mechanisms and multivane slurry valves.

  15. Biparticle fluidized bed reactor

    DOEpatents

    Scott, Charles D.; Marasco, Joseph A.

    1996-01-01

    A fluidized bed reactor system which utilizes a fluid phase, a retained fluidized primary particulate phase, and a migratory second particulate phase. The primary particulate phase is a particle such as a gel bead containing an immobilized biocatalyst. The secondary and tertiary particulate phases, continuously introduced and removed simultaneously in the cocurrent and countercurrent mode, act in a role such as a sorbent to continuously remove a product or by-product constituent from the fluid phase. Means for introducing and removing the sorbent phases include feed screw mechanisms and multivane slurry valves.

  16. Biparticle fluidized bed reactor

    DOEpatents

    Scott, Charles D.

    1993-01-01

    A fluidized bed reactor system which utilizes a fluid phase, a retained fluidized primary particulate phase, and a migratory second particulate phase. The primary particulate phase is a particle such as a gel bead containing an immobilized biocatalyst. The secondary particulate phase, continuously introduced and removed in either cocurrent or countercurrent mode, acts in a secondary role such as a sorbent to continuously remove a product or by-product constituent from the fluid phase. Introduction and removal of the sorbent phase is accomplished through the use of feed screw mechanisms and multivane slurry valves.

  17. Biparticle fluidized bed reactor

    DOEpatents

    Scott, C.D.; Marasco, J.A.

    1996-02-27

    A fluidized bed reactor system is described which utilizes a fluid phase, a retained fluidized primary particulate phase, and a migratory second particulate phase. The primary particulate phase is a particle such as a gel bead containing an immobilized biocatalyst. The secondary and tertiary particulate phases, continuously introduced and removed simultaneously in the cocurrent and countercurrent mode, act in a role such as a sorbent to continuously remove a product or by-product constituent from the fluid phase. Means for introducing and removing the sorbent phases include feed screw mechanisms and multivane slurry valves. 3 figs.

  18. Particle bed reactor modeling

    NASA Technical Reports Server (NTRS)

    Sapyta, Joe; Reid, Hank; Walton, Lew

    1993-01-01

    The topics are presented in viewgraph form and include the following: particle bed reactor (PBR) core cross section; PBR bleed cycle; fuel and moderator flow paths; PBR modeling requirements; characteristics of PBR and nuclear thermal propulsion (NTP) modeling; challenges for PBR and NTP modeling; thermal hydraulic computer codes; capabilities for PBR/reactor application; thermal/hydralic codes; limitations; physical correlations; comparison of predicted friction factor and experimental data; frit pressure drop testing; cold frit mask factor; decay heat flow rate; startup transient simulation; and philosophy of systems modeling.

  19. Biparticle fluidized bed reactor

    DOEpatents

    Scott, C.D.

    1993-12-14

    A fluidized bed reactor system which utilizes a fluid phase, a retained fluidized primary particulate phase, and a migratory second particulate phase is described. The primary particulate phase is a particle such as a gel bead containing an immobilized biocatalyst. The secondary particulate phase, continuously introduced and removed in either cocurrent or countercurrent mode, acts in a secondary role such as a sorbent to continuously remove a product or by-product constituent from the fluid phase. Introduction and removal of the sorbent phase is accomplished through the use of feed screw mechanisms and multivane slurry valves. 3 figures.

  20. Coated ceramic breeder materials

    DOEpatents

    Tam, Shiu-Wing; Johnson, Carl E.

    1987-04-07

    A breeder material for use in a breeder blanket of a nuclear reactor is disclosed. The breeder material comprises a core material of lithium containing ceramic particles which has been coated with a neutron multiplier such as Be or BeO, which coating has a higher thermal conductivity than the core material.

  1. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2001-05-01

    The mechanical properties of model systems were analyzed. A reasonably accurate finite element model was implemented and a rational metric to predict the strength of ceramic/metal concentrical joints was developed. The mode of failure of the ceramic/metal joints was determined and the importance of the mechanical properties of the braze material was assessed. Thermal cycling experiments were performed on the model systems and the results were discussed. Additionally, experiments using the concept of placing diffusion barriers on the ceramic surface to limit the extent of the reaction with the braze were performed. It was also observed that the nature and morphology of the reaction zone depends greatly on the nature of the perovskite structure being used. From the experiments, it is observed that the presence of Cr in the Fe-occupied sites decreases the tendency of Fe to segregate and to precipitate out of the lattice. In these new experiments, Ni was observed to play a major role in the decomposition of the ceramic substrate.

  2. Refractory ceramic fibers

    Integrated Risk Information System (IRIS)

    Refractory ceramic fibers ; CASRN Not found Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcino

  3. Microwave processing of ceramics

    SciTech Connect

    Katz, J.D.

    1993-01-01

    Recent work in the areas of microwave processing and joining of ceramics is briefly reviewed. Advantages and disadvantages of microwave processing as well as some of the current issues in the field are discussed. Current state and potential for future commercialization of this technology is also addressed.

  4. Microwave processing of ceramics

    SciTech Connect

    Katz, J.D.

    1993-04-01

    Recent work in the areas of microwave processing and joining of ceramics is briefly reviewed. Advantages and disadvantages of microwave processing as well as some of the current issues in the field are discussed. Current state and potential for future commercialization of this technology is also addressed.

  5. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, M.A.; Guangyao Sheng.

    1993-05-04

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  6. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  7. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendfra Nagabhushana

    2001-07-01

    The mechanical properties of model systems were analyzed. A reasonably accurate finite element model was implemented and a rational metric to predict the strength of ceramic/metal concentrical joints was developed. The mode of failure of the ceramic/metal joints was determined and the importance of the mechanical properties of the braze material was assessed. Thermal cycling experiments were performed on the model systems and the results were discussed. Additionally, experiments using the concept of placing diffusion barriers on the ceramic surface to limit the extent of the reaction with the braze were performed. It was also observed that the nature and morphology of the reaction zone depends greatly on the nature of the perovskite structure being used. From the experiments, it is observed that the presence of Cr in the Fe-occupied sites decreases the tendency of Fe to segregate and to precipitate out of the lattice. In these new experiments, Ni was observed to play a major role in the decomposition of the ceramic substrate.

  8. Silicon carbide ceramic production

    NASA Technical Reports Server (NTRS)

    Suzuki, K.; Shinohara, N.

    1984-01-01

    A method to produce sintered silicon carbide ceramics in which powdery carbonaceous components with a dispersant are mixed with silicon carbide powder, shaped as required with or without drying, and fired in nonoxidation atmosphere is described. Carbon black is used as the carbonaceous component.

  9. USGS exploration geochemistry studies at the Pebble porphyry Cu-Au-Mo deposit, Alaska-pdf of presentation

    USGS Publications Warehouse

    Eppinger, Robert G.; Kelley, Karen D.; Fey, David L.; Giles, Stuart A.; Minsley, Burke J.; Smith, Steven M.

    2010-01-01

    From 2007 through 2010, scientists in the U.S. Geological Survey (USGS) have been conducting exploration-oriented geochemical and geophysical studies in the region surrounding the giant Pebble porphyry Cu-Au-Mo deposit in southwestern Alaska. The Cretaceous Pebble deposit is concealed under tundra, glacial till, and Tertiary cover rocks, and is undisturbed except for numerous exploration drill holes. These USGS studies are part of a nation-wide research project on evaluating and detecting concealed mineral resources. This report focuses on exploration geochemistry and comprises illustrations and associated notes that were presented as a case study in a workshop on this topic. The workshop, organized by L.G. Closs and R. Glanzman, is called 'Geochemistry in Mineral Exploration and Development,' presented by the Society of Economic Geologists at a technical conference entitled 'The Challenge of Finding New Mineral Resources: Global Metallogeny, Integrative Exploration and New Discoveries,' held at Keystone, Colorado, October 2-5, 2010.

  10. Granulometry of pebble beach ridges in Fort Williams Point, Greenwich Island, Antarctic Peninsula; a possible result from Holocene climate fluctuations

    USGS Publications Warehouse

    Santana, E.; Dumont, J.F.

    2007-01-01

    We present a granulometric study of emerged pebble beach ridges in the Fort Williams Point, Greenwich Island, Antarctic Peninsula. We studied 8 beach ridges from the shore up to 13.5 m above current sea level. The beach ridges are made of volcanic material from the surrounding relief, but also include glacially transported gneiss and granodiorite pebble and cobble. Based on granulometric distribution analysis of 2100 samples from 39 locations we identified evidence of 4 sequences of 1 to 3 ridges. Most of the material seems to be reworked from a till. Pavement formation by iceberg between the sequences of beach ridges suggests periods of lower temperature. The interpretation suggests that sequences of beach ridge construction formed during warmer periods of the late Holocene. This occurs in the framework of an isostatic postglacial uplift allowing the progressive mobilization of periglaciar material.

  11. Moving granular-bed filter development program option I -- Component test facilities technical tradeoffs and issues. Topical report

    SciTech Connect

    Newby, R.A.; Yang, W.C.; Smeltzer, E.E.; Lippert, T.E.; Gasparovic, A.C.; Kittle, W.F.; Schneider, G.N.; Fellers, A.W.

    1994-06-01

    Advanced, coal-based, power plants, such as IGCC and Advanced-PFBC, are currently nearing commercial demonstration. These power plant technologies require hot gas filtration as part of their gas cleaning trains. Ceramic barrier filters are the major filter candidates being developed for these hot gas cleaning applications. While ceramic barrier filters achieve high levels of particle removal, there are concerns for their reliability and operability in these applications. An alternative hot gas filtration technology is the moving granular bed filter. These systems are at a lower state of development than ceramic barrier filters, and the current, moving granular-bed filter technologies are relatively large, complex, and costly systems in terms of their capital investment, their operating and maintenance cost, and their impact on the power plant efficiency. In addition, their effectiveness as filters is still in question. Their apparent attributes, relative to ceramic barrier filter systems, result from their much less severe mechanical design and materials constraints, and the potential for more reliable, failure-free particle removal operation. The Westinghouse Science & Technology Center has proposed a novel moving granular-bed filter concept, the Standleg Moving Granular-Bed Filter (SMGBF) system, that may overcome the inherent deficiencies of the current state-of-the-art moving granular-bed filter technology. The SMGBF is a compact unit that uses cocurrent gas-pellet contacting in an arrangement that greatly simplifies and enhances the distribution of dirty, process gas to the moving bed and allows effective disengagement of clean gas from the moving bed.

  12. Fast fluidized bed steam generator

    DOEpatents

    Bryers, Richard W.; Taylor, Thomas E.

    1980-01-01

    A steam generator in which a high-velocity, combustion-supporting gas is passed through a bed of particulate material to provide a fluidized bed having a dense-phase portion and an entrained-phase portion for the combustion of fuel material. A first set of heat transfer elements connected to a steam drum is vertically disposed above the dense-phase fluidized bed to form a first flow circuit for heat transfer fluid which is heated primarily by the entrained-phase fluidized bed. A second set of heat transfer elements connected to the steam drum and forming the wall structure of the furnace provides a second flow circuit for the heat transfer fluid, the lower portion of which is heated by the dense-phase fluidized bed and the upper portion by the entrained-phase fluidized bed.

  13. Tritium release kinetics from Li 2TiO 3 pebbles as prepared by soft-wet-chemistry

    NASA Astrophysics Data System (ADS)

    Casadio, S.; van der Laan, J. G.; Alvani, C.; Magielsen, A. J.; Stijkel, M. P.

    2004-08-01

    Lithium meta titanate pebbles has been prepared from agglomeration-sintering powders which were obtained by Li-Ti-peroxo-complex solution precursor (Li 2TiO 3 dissolved at room temperature in H 2O + 40% H 2O 2 and stabilized with citric acid). Through this wet route Li 2TiO 3 pebbles with high density(˜92% of T.D.) has been obtained and the tritium release behavior has been tested `in-pile' by the EXOTIC-8.9 experiment (˜440 days of irradiation at full power in the high neutron flux of HFR-Petten). Tritium residence times ( τ) in the pebbles has been measured during irradiation between 550 and 400 °C and He + 0.1%H 2 purge gas composition. By a thermally activated process (activation energy=111 kJ/mol) with 410 °C as minimum temperature the tritium residence time is found to be about 1 day, which places this specimen in a good ranking position among those tested by the EXOTIC-series. A clear increase of the tritium release rate has been observed by increased H 2 concentration (up to 1%) in the He purge. Out-of-pile ramp-annealing tritium desorption (TPD) tests on short-time irradiated pebbles has been also performed by various devices and conditions. The kinetic parameters from the TPD investigation gave consistent results with those characterizing the equilibrium times of tritium release rate after the gas composition and temperature transients imposed on the specimen during the in-pile experiment.

  14. Ceramic Laser Materials

    SciTech Connect

    Soules, T F; Clapsaddle, B J; Landingham, R L; Schaffers, K I

    2005-02-15

    Transparent ceramic materials have several major advantages over single crystals in laser applications, not the least of which is the ability to make large aperture parts in a robust manufacturing process. After more than a decade of working on making transparent YAG:Nd, Japanese workers have recently succeeded in demonstrating samples that performed as laser gain media as well as their single crystal counterparts. Since then several laser materials have been made and evaluated. For these reasons, developing ceramic laser materials is the most exciting and futuristic materials topic in today's major solid-state laser conferences. We have established a good working relationship with Konoshima Ltd., the Japanese producer of the best ceramic laser materials, and have procured and evaluated slabs designed by us for use in our high-powered SSHCL. Our measurements indicate that these materials will work in the SSHCL, and we have nearly completed retrofitting the SSHCL with four of the largest transparent ceramic YAG:Nd slabs in existence. We have also begun our own effort to make this material and have produced samples with various degrees of transparency/translucency. We are in the process of carrying out an extensive design-of-experiments to establish the significant process variables for making transparent YAG. Finally because transparent ceramics afford much greater flexibility in the design of lasers, we have been exploring the potential for much larger apertures, new materials, for example for the Mercury laser, other designs for SSHL, such as, edge pumping designs, slabs with built in ASE suppression, etc. This work has just beginning.

  15. Ceramic tubesheet design analysis

    SciTech Connect

    Mallett, R.H.; Swindeman, R.W.

    1996-06-01

    A transport combustor is being commissioned at the Southern Services facility in Wilsonville, Alabama to provide a gaseous product for the assessment of hot-gas filtering systems. One of the barrier filters incorporates a ceramic tubesheet to support candle filters. The ceramic tubesheet, designed and manufactured by Industrial Filter and Pump Manufacturing Company (EF&PM), is unique and offers distinct advantages over metallic systems in terms of density, resistance to corrosion, and resistance to creep at operating temperatures above 815{degrees}C (1500{degrees}F). Nevertheless, the operational requirements of the ceramic tubesheet are severe. The tubesheet is almost 1.5 m in (55 in.) in diameter, has many penetrations, and must support the weight of the ceramic filters, coal ash accumulation, and a pressure drop (one atmosphere). Further, thermal stresses related to steady state and transient conditions will occur. To gain a better understanding of the structural performance limitations, a contract was placed with Mallett Technology, Inc. to perform a thermal and structural analysis of the tubesheet design. The design analysis specification and a preliminary design analysis were completed in the early part of 1995. The analyses indicated that modifications to the design were necessary to reduce thermal stress, and it was necessary to complete the redesign before the final thermal/mechanical analysis could be undertaken. The preliminary analysis identified the need to confirm that the physical and mechanical properties data used in the design were representative of the material in the tubesheet. Subsequently, few exploratory tests were performed at ORNL to evaluate the ceramic structural material.

  16. Fluidized Bed Steam Reformer (FBSR) monolith formation

    SciTech Connect

    Jantzen, C.M.

    2007-07-01

    Fluidized Bed Steam Reforming (FBSR) is being considered as an alternative technology for the immobilization of a wide variety of aqueous high sodium containing radioactive wastes at various DOE facilities in the United States. The addition of clay, charcoal, and a catalyst as co-reactants converts aqueous Low Activity Wastes (LAW) to a granular or 'mineralized' waste form while converting organic components to CO{sub 2} and steam, and nitrate/nitrite components, if any, to N{sub 2}. The waste form produced is a multiphase mineral assemblage of Na-Al-Si (NAS) feldspathoid minerals with cage-like structures that atomically bond radionuclides like Tc-99 and anions such as SO{sub 4}, I, F, and Cl. The granular product has been shown to be as durable as LAW glass. Shallow land burial requires that the mineralized waste form be able to sustain the weight of soil overburden and potential intrusion by future generations. The strength requirement necessitates binding the granular product into a monolith. FBSR mineral products were formulated into a variety of monoliths including various cements, Ceramicrete, and hydro-ceramics. All but one of the nine monoliths tested met the <2 g/m{sup 2} durability specification for Na and Re (simulant for Tc-99) when tested using the Product Consistency Test (PCT; ASTM C1285). Of the nine monoliths tested the cements produced with 80-87 wt% FBSR product, the Ceramicrete, and the hydro-ceramic produced with 83.3 wt% FBSR product, met the compressive strength and durability requirements for an LAW waste form. (authors)

  17. Capacitively-Heated Fluidized Bed

    NASA Technical Reports Server (NTRS)

    Mchale, E. J.

    1982-01-01

    Fluidized-bed chamber in which particles in bed are capacitively heated produces high yields of polycrystalline silicon for semiconductor devices. Deposition of unrecoverable silicon on chamber wall is reduced, and amount of recoverable silicon depositing on seed particles in bed is increased. Particles also have a size and density suitable for direct handling without consolidation, unlike silicon dust produced in heated-wall chambers.

  18. Fluidized bed boiler feed system

    DOEpatents

    Jones, Brian C.

    1981-01-01

    A fluidized bed boiler feed system for the combustion of pulverized coal. Coal is first screened to separate large from small particles. Large particles of coal are fed directly to the top of the fluidized bed while fine particles are first mixed with recycled char, preheated, and then fed into the interior of the fluidized bed to promote char burnout and to avoid elutriation and carryover.

  19. Pressurized fluidized bed reactor

    DOEpatents

    Isaksson, J.

    1996-03-19

    A pressurized fluid bed reactor power plant includes a fluidized bed reactor contained within a pressure vessel with a pressurized gas volume between the reactor and the vessel. A first conduit supplies primary gas from the gas volume to the reactor, passing outside the pressure vessel and then returning through the pressure vessel to the reactor, and pressurized gas is supplied from a compressor through a second conduit to the gas volume. A third conduit, comprising a hot gas discharge, carries gases from the reactor, through a filter, and ultimately to a turbine. During normal operation of the plant, pressurized gas is withdrawn from the gas volume through the first conduit and introduced into the reactor at a substantially continuously controlled rate as the primary gas to the reactor. In response to an operational disturbance of the plant, the flow of gas in the first, second, and third conduits is terminated, and thereafter the pressure in the gas volume and in the reactor is substantially simultaneously reduced by opening pressure relief valves in the first and third conduits, and optionally by passing air directly from the second conduit to the turbine. 1 fig.

  20. Pressurized fluidized bed reactor

    DOEpatents

    Isaksson, Juhani

    1996-01-01

    A pressurized fluid bed reactor power plant includes a fluidized bed reactor contained within a pressure vessel with a pressurized gas volume between the reactor and the vessel. A first conduit supplies primary gas from the gas volume to the reactor, passing outside the pressure vessel and then returning through the pressure vessel to the reactor, and pressurized gas is supplied from a compressor through a second conduit to the gas volume. A third conduit, comprising a hot gas discharge, carries gases from the reactor, through a filter, and ultimately to a turbine. During normal operation of the plant, pressurized gas is withdrawn from the gas volume through the first conduit and introduced into the reactor at a substantially continuously controlled rate as the primary gas to the reactor. In response to an operational disturbance of the plant, the flow of gas in the first, second, and third conduits is terminated, and thereafter the pressure in the gas volume and in the reactor is substantially simultaneously reduced by opening pressure relief valves in the first and third conduits, and optionally by passing air directly from the second conduit to the turbine.

  1. Debris-bed friction of hard-bedded glaciers

    USGS Publications Warehouse

    Cohen, D.; Iverson, N.R.; Hooyer, T.S.; Fischer, U.H.; Jackson, M.; Moore, P.L.

    2005-01-01

    [1] Field measurements of debris-bed friction on a smooth rock tablet at the bed of Engabreen, a hard-bedded, temperate glacier in northern Norway, indicated that basal ice containing 10% debris by volume exerted local shear traction of up to 500 kPa. The corresponding bulk friction coefficient between the dirty basal ice and the tablet was between 0.05 and 0.08. A model of friction in which nonrotating spherical rock particles are held in frictional contact with the bed by bed-normal ice flow can account for these measurements if the power law exponent for ice flowing past large clasts is 1. A small exponent (n < 2) is likely because stresses in ice are small and flow is transient. Numerical calculations of the bed-normal drag force on a sphere in contact with a flat bed using n = 1 show that this force can reach values several hundred times that on a sphere isolated from the bed, thus drastically increasing frictional resistance. Various estimates of basal friction are obtained from this model. For example, the shear traction at the bed of a glacier sliding at 20 m a-1 with a geothermally induced melt rate of 0.006 m a-1 and an effective pressure of 300 kPa can exceed 100 kPa. Debris-bed friction can therefore be a major component of sliding resistance, contradicting the common assumption that debris-bed friction is negligible. Copyright 2005 by the American Geophysical Union.

  2. Fluidized bed deposition of diamond

    DOEpatents

    Laia, Jr., Joseph R.; Carroll, David W.; Trkula, Mitchell; Anderson, Wallace E.; Valone, Steven M.

    1998-01-01

    A process for coating a substrate with diamond or diamond-like material including maintaining a substrate within a bed of particles capable of being fluidized, the particles having substantially uniform dimensions and the substrate characterized as having different dimensions than the bed particles, fluidizing the bed of particles, and depositing a coating of diamond or diamond-like material upon the substrate by chemical vapor deposition of a carbon-containing precursor gas mixture, the precursor gas mixture introduced into the fluidized bed under conditions resulting in excitation mechanisms sufficient to form the diamond coating.

  3. Method for packing chromatographic beds

    DOEpatents

    Freeman, David H.; Angeles, Rosalie M.; Keller, Suzanne

    1991-01-01

    Column chromatography beds are packed through the application of static force. A slurry of the chromatography bed material and a non-viscous liquid is filled into the column plugged at one end, and allowed to settle. The column is transferred to a centrifuge, and centrifuged for a brief period of time to achieve a predetermined packing level, at a range generally of 100-5,000 gravities. Thereafter, the plug is removed, other fixtures may be secured, and the liquid is allowed to flow out through the bed. This results in an evenly packed bed, with no channeling or preferential flow characteristics.

  4. Ceramic oxide powders and the formation thereof

    DOEpatents

    Katz, J.L.; Chenghung Hung.

    1993-12-07

    Ceramic oxide powders and a method for their preparation. Ceramic oxide powders are obtained using a flame process whereby two or more precursors of ceramic oxides are introduced into a counterflow diffusion flame burner wherein said precursors are converted into ceramic oxide powders. The morphology, particle size, and crystalline form of the ceramic oxide powders are determined by process conditions. 14 figures.

  5. Ceramic oxide powders and the formation thereof

    DOEpatents

    Katz, Joseph L.; Hung, Cheng-Hung

    1993-01-01

    Ceramic oxide powders and a method for their preparation. Ceramic oxide powders are obtained using a flame process whereby two or more precursors of ceramic oxides are introduced into a counterflow diffusion flame burner wherein said precursors are converted into ceramic oxide powders. The morphology, particle size, and crystalline form of the ceramic oxide powders are determined by process conditions.

  6. Oxidation and Corrosion of Ceramics and Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Opila, Elizabeth J.; Lee, Kang N.

    2000-01-01

    Ceramics and ceramic matrix composites are candidates for numerous applications in high temperature environments with aggressive gases and possible corrosive deposits. There is a growing realization that high temperature oxidation and corrosion issues must be considered. There are many facets to these studies, which have been extensively covered in some recent reviews. The focus of this paper is on current research, over the past two years. In the authors' view, the most important oxidation and corrosion studies have focused on four major areas during this time frame. These are; (I) Oxidation of precursor-based ceramics; (II) Studies of the interphase material in ceramic matrix composites; (III) Water vapor interactions with ceramics, particularly in combustion environments; and (IV) Development of refractory oxide coatings for silicon-based ceramics. In this paper, we shall explore the most current work in each of these areas.

  7. Variability of bed drag on cohesive beds under wave action

    USGS Publications Warehouse

    Safak, Ilgar

    2016-01-01

    Drag force at the bed acting on water flow is a major control on water circulation and sediment transport. Bed drag has been thoroughly studied in sandy waters, but less so in muddy coastal waters. The variation of bed drag on a muddy shelf is investigated here using field observations of currents, waves, and sediment concentration collected during moderate wind and wave events. To estimate bottom shear stress and the bed drag coefficient, an indirect empirical method of logarithmic fitting to current velocity profiles (log-law), a bottom boundary layer model for combined wave-current flow, and a direct method that uses turbulent fluctuations of velocity are used. The overestimation by the log-law is significantly reduced by taking turbulence suppression due to sediment-induced stratification into account. The best agreement between the model and the direct estimates is obtained by using a hydraulic roughness of 10  m in the model. Direct estimate of bed drag on the muddy bed is found to have a decreasing trend with increasing current speed, and is estimated to be around 0.0025 in conditions where wave-induced flow is relatively weak. Bed drag shows an increase (up to fourfold) with increasing wave energy. These findings can be used to test the bed drag parameterizations in hydrodynamic and sediment transport models and the skills of these models in predicting flows in muddy environments.

  8. Ceramic process and plant design for high-level nuclear waste immobilization

    SciTech Connect

    Grantham, L.F.; McKisson, R.L.; De Wames, R.E.; Guon, J.; Flintoff, J.F.; McKenzie, D.E.

    1983-01-01

    In the last 3 years, significant advances in ceramic technology for high-level nuclear waste solidification have been made. Product quality in terms of leach-resistance, compositional uniformity, structural integrity, and thermal stability promises to be superior to borosilicate glass. This paper addresses the process effectiveness and preliminary designs for glass and ceramic immobilization plants. The reference two-step ceramic process utilizes fluid-bed calcination (FBC) and hot isostatic press (HIP) consolidation. Full-scale demonstration of these well-developed processing steps has been established at DOE and/or commercial facilities for processing radioactive materials. Based on Savannah River-type waste, our model predicts that the capital and operating cost for the solidification of high-level nuclear waste is about the same for the ceramic and glass options. However, when repository costs are included, the ceramic option potentially offers significantly better economics due to its high waste loading and volume reduction. Volume reduction impacts several figures of merit in addition to cost such as system logistics, storage, transportation, and risk. The study concludes that the ceramic product/process has many potential advantages, and rapid deployment of the technology could be realized due to full-scale demonstrations of FBC and HIP technology in radioactive environments. Based on our finding and those of others, the ceramic innovation not only offers a viable backup to the glass reference process but promises to be a viable future option for new high-level nuclear waste management opportunities.

  9. Ceramic heat-exchanger applications study

    SciTech Connect

    McFarlin, D.J.; Sgamboti, C.T.; Lessard, R.D.

    1982-10-01

    To put the potential benefits of ceramic heat exchangers (CHX) applications into quantitative perspective, several industrial cogeneration and electric utiity power generation systems were surveyed and evaluated. This study was focused on coal-based fuel fired applications, for which system performance and economic assessments were made. Seven CHX applications in the industrial cogeneration sector were selected for evaluation. These include (1) Gasified Coal-Fired Gas Turbine, (2) Pressurized Fluidized Bed Combustor (PFBC)-Gas Turbine, (3) Atmospheric Fluidized Bed Combustor (AFBC)-Gas Turbine, (4 and 5) AFBC Combined Cycle with and without reheat and (6 and 7) Indirect Coal-Fired Gas Turbine and Combined Cycle. The performance and economics of these cogeneration systems were evaluated and compared with other competing systems (both advanced and State-of-the-Art). For the electric utility power generation sector five applications utilizing a CHX were selected and evaluated; their performance and cost factors were compared to those of a reference pulverized coal-fired steam plant with flue gas desulfurization. These five applications included (1) PFBC-Combined Cycle, (2) AFBC-Combined Cycle, (3) Industrial Coal Gasifier-Combined Cycle, (4) Indirect Coal-Fired Combined Cycle, and (5) Indirect Coal-Fired Simple Cycle. Of the five CHX applications evaluated in the power generation sector, only the AFBC system showed a clear gain over the reference pulverized coal system.

  10. Ceramic Stereolithography: Additive Manufacturing for Ceramics by Photopolymerization

    NASA Astrophysics Data System (ADS)

    Halloran, John W.

    2016-07-01

    Ceramic stereolithography and related additive manufacturing methods involving photopolymerization of ceramic powder suspensions are reviewed in terms of the capabilities of current devices. The practical fundamentals of the cure depth, cure width, and cure profile are related to the optical properties of the monomer, ceramic, and photo-active components. Postpolymerization steps, including harvesting and cleaning the objects, binder burnout, and sintering, are discussed and compared with conventional methods. The prospects for practical manufacturing are discussed.

  11. Integrally cored ceramic investment casting mold fabricated by ceramic stereolithography

    NASA Astrophysics Data System (ADS)

    Bae, Chang-Jun

    Superalloy airfoils are produced by investment casting (IC), which uses ceramic cores and wax patterns with ceramic shell molds. Hollow cored superalloy airfoils in a gas turbine engine are an example of complex IC parts. The complex internal hollow cavities of the airfoil are designed to conduct cooling air through one or more passageways. These complex internal passageways have been fabricated by a lost wax process requiring several processing steps; core preparation, injection molding for wax pattern, and dipping process for ceramic shell molds. Several steps generate problems such as high cost and decreased accuracy of the ceramic mold. For example, costly tooling and production delay are required to produce mold dies for complex cores and wax patterns used in injection molding, resulting in a big obstacle for prototypes and smaller production runs. Rather than using separate cores, patterns, and shell molds, it would be advantageous to directly produce a mold that has the casting cavity and the ceramic core by one process. Ceramic stereolithography (CerSLA) can be used to directly fabricate the integrally cored ceramic casting mold (ICCM). CerSLA builds ceramic green objects from CAD files from many thin liquid layers of powder in monomer, which are solidified by polymerization with a UV laser, thereby "writing" the design for each slice. This dissertation addresses the integrally cored casting ceramic mold (ICCM), the ceramic core with a ceramic mold shell in a single patternless construction, fabricated by ceramic stereolithography (CerSLA). CerSLA is considered as an alternative method to replace lost wax processes, for small production runs or designs too complex for conventional cores and patterns. The main topic is the development of methods to successfully fabricate an ICCM by CerSLA from refractory silica, as well as related issues. The related issues are the segregation of coarse fused silica powders in a layer, the degree of segregation parameter to

  12. Development of ceramic composite hot-gas filters

    SciTech Connect

    Judkins, R.R.; Stinton, D.P.; Smith, R.G.; Fischer, E.M.; Eaton, J.H.; Weaver, B.L.; Kahnke, J.L.; Pysher, D.J.

    1995-04-01

    A novel type of hot-gas filter based on a ceramic fiber-reinforced ceramic matrix was developed and extended to fullsize, 60-mm OD by 1.5-meter-long, candle filters. A commercially viable process for producing the filters was developed, and the filters are undergoing testing and demonstration throughout the world for applications in pressurized fluidized-bed combustion (PFBC) and integrated gasification combined cycle (IGCC) plants. Development activities at Oak Ridge National Laboratory (ORNL) and at the 3M Company, and testing at the Westinghouse Science and Technology Center (STC) are presented. Demonstration tests at the Tidd PFBC are underway. Issues identified during the testing and demonstration phases of the development are discussed. Resolution of the issues and the status of commercialization of the filters are described.

  13. Using Kinect to analyze pebble to block-sized clasts in sedimentology

    NASA Astrophysics Data System (ADS)

    Moreno Chávez, G.; Sarocchi, D.; Arce Santana, E.; Borselli, L.; Rodríguez-Sedano, L. A.

    2014-11-01

    In this paper, we propose a new system for automatically measuring grain sizes in a range from pebbles to blocks. The system is based on use of the Microsoft Kinect device and a novel software developed by the authors which enables a tridimensional digital model of a selected area of an outcrop to be captured. With the tridimensional model, clasts are stacked using new segmentation algorithms based on level sets and Fourier analysis. The resulting binary image (clasts and matrix) is analyzed by means of the Rosiwal stereological method. The granulometric Cumulative Distribution Function (CDF), obtained automatically by this new methodology, was compared to the granulometric CDF, obtained manually by the Rosiwal technique, by means of a Kolmogorov-Smirnov test. The comparison showed good agreement between the methods and demonstrated that this inexpensive system (already used in several scientific fields) with great potential can also be used to obtain fast, automatic and accurate grain size distributions of sedimentary deposits. The software tools used to control the Kinect device, which provide the three-dimensional elevation models of the outcrops and allows its analysis, are freely available from the author.

  14. The orbital evolution of asteroids, pebbles and planets from giant branch stellar radiation and winds

    NASA Astrophysics Data System (ADS)

    Veras, Dimitri; Eggl, Siegfried; Gänsicke, Boris T.

    2015-08-01

    The discovery of over 50 planets around evolved stars and more than 35 debris discs orbiting white dwarfs highlight the increasing need to understand small body evolution around both early and asymptotic giant branch (GB) stars. Pebbles and asteroids are susceptible to strong accelerations from the intense luminosity and winds of GB stars. Here, we establish equations that can model time-varying GB stellar radiation, wind drag and mass-loss. We derive the complete three-dimensional equations of motion in orbital elements due to (1) the Epstein and Stokes regimes of stellar wind drag, (2) Poynting-Robertson drag, and (3) the Yarkovsky drift with seasonal and diurnal components. We prove through averaging that the potential secular eccentricity and inclination excitation due to Yarkovsky drift can exceed that from Poynting-Robertson drag and radiation pressure by at least three orders of magnitude, possibly flinging asteroids which survive YORP spin-up into a widely dispersed cloud around the resulting white dwarf. The GB Yarkovsky effect alone may change an asteroid's orbital eccentricity by 10 per cent in just 1 Myr. Damping perturbations from stellar wind drag can be just as extreme, but are strongly dependent on the highly uncertain local gas density and mean free path length. We conclude that GB radiative and wind effects must be considered when modelling the post-main-sequence evolution of bodies smaller than about 1000 km.

  15. Pebble treatment and use at Cleveland-Cliffs` autogenous milling operations

    SciTech Connect

    Greenwood, B.R.; McIvor, R.E.

    1996-12-31

    Subsidiaries of Cleveland-Cliffs Inc. operate seven iron mining operations worldwide. Of these seven operations, four North American facilities employ autogenous milling. Two of these autogenous milling circuits are in northern Michigan, the Tilden and Empire Mines, one is in northern Minnesota, Hibbing Taconite, and the fourth is the Wabush Mine in Labrador. The original autogenous milling circuit developed by Cleveland-Cliffs was at the Empire Mine. Extensive laboratory, pilot plant and full-scale testing was conducted prior to commissioning this first iron ore autogenous circuit in 1963. Since the original circuits were installed at the four mines, modifications have been made based on pilot plant and full-scale plant tests that have resulted in significant improvements in primary mill throughputs. The following is a discussion of the autogenous milling circuits at Empire, Tilden and Hibtac and the changes to the circuits related to pebble treatment and use that have been and are scheduled to be made to increase feed rates and/or improve efficiency.

  16. Evidence of Fast Pebble Growth Near Condensation Fronts in the HL Tau Protoplanetary Disk

    NASA Astrophysics Data System (ADS)

    Zhang, Ke; Blake, Geoffrey A.; Bergin, Edwin A.

    2015-06-01

    Water and simple organic molecular ices dominate the mass of solid materials available for planetesimal and planet formation beyond the water snow line. Here we analyze ALMA long baseline 2.9, 1.3 and 0.87 mm continuum images of the young star HL Tau, and suggest that the emission dips observed are due to rapid pebble growth around the condensation fronts of abundant volatile species. Specifically, we show that the prominent innermost dip at 13 AU is spatially resolved in the 0.87 mm image, and its center radius is coincident with the expected mid-plane condensation front of water ice. In addition, two other prominent dips, at distances of 32 and 63 AU, cover the mid-plane condensation fronts of pure ammonia or ammonia hydrates and clathrate hydrates (especially with CO and N2) formed from amorphous water ice. The spectral index map of HL Tau between 1.3 and 0.87 mm shows that the flux ratios inside the dips are statistically larger than those of nearby regions in the disk. This variation can be explained by a model with two dust populations, where most of the solid mass resides in a component that has grown to decimeter size scales inside the dips. Such growth is in accord with recent numerical simulations of volatile condensation, dust coagulation, and settling.

  17. Applying Pebble-Rotating Game to enhance the robustness of DHTs.

    PubMed

    Ren, Liyong; Nie, Xiaowen; Dong, Yuchi

    2013-01-01

    Distributed hash tables (DHTs) are usually used in the open networking environment, where they are vulnerable to Sybil attacks. Pebble-Rotating Game (PRG) mixes the nodes of the honest and the adversarial randomly, and can resist the Sybil attack efficiently. However, the adversary may have some tricks to corrupt the rule of PRG. This paper proposes a set of mechanisms to make the rule of PRG be obliged to obey. A new joining node must ask the Certificate Authority (CA) for its signature and certificate, which records the complete process on how a node joins the network and obtains the legitimacy of the node. Then, to prevent the adversary from accumulating identifiers, any node can make use of the latest certificate to judge whether one identifier is expired with the help of the replacement property of RPG. This paper analyzes in details the number of expired certificates which are needed to store in every node, and gives asymptotic solution of this problem. The analysis and simulations show that the mean number of the certificates stored in each node are [Formula: see text], where n is the size of the network. PMID:23776485

  18. Spin Dynamics of Kelvin's Pebbles, Jellett's Eggs, and Shiva's Lingam Stones

    NASA Astrophysics Data System (ADS)

    Brecher, Kenneth

    2015-04-01

    Study of the problem of the rise of the center of mass (COM) of spinning objects is said to have begun in the late nineteenth century. These early mathematical treatments aimed to explain the motion of the newly invented and patented ``tippe top.'' This semi-spheroidal top will invert when spun on a smooth surface while raising its COM. Because of the importance of friction in their dynamics, such non-holonomic systems are not readily amenable to analytic treatment, or of intuitive understanding. In notes written in 1844 - before the invention of the tippe top - Lord Kelvin (William Thomson) discussed the problem of the rising COM of spinning objects. He experimented with both oblate and prolate ellipsoidal pebbles, but did not publish a complete theoretical treatment of the problem. J. H. Jellett, in his 1872 book ``Theory of Friction,'' provided a partial account of the related problem of the rise of the COM for an egg-shaped (ovoid) object, making use of a new (adiabatic) invariant of the motion that he devised. Naturally occurring prolate ellipsoidal ``Lingam stones'' from the Narmada River in India exhibit similar counter-intuitive dynamical behavior. When spun around its minor axis in a horizontal plane, a Lingam stone will stand erect and spin around its major axis in a vertical position. This presentation will explore the history and some of the experimental facts and theoretical ideas about the rotational dynamics of such physical objects.

  19. Applying Pebble-Rotating Game to Enhance the Robustness of DHTs

    PubMed Central

    Ren, LiYong; Nie, XiaoWen; Dong, YuChi

    2013-01-01

    Distributed hash tables (DHTs) are usually used in the open networking environment, where they are vulnerable to Sybil attacks. Pebble-Rotating Game (PRG) mixes the nodes of the honest and the adversarial randomly, and can resist the Sybil attack efficiently. However, the adversary may have some tricks to corrupt the rule of PRG. This paper proposes a set of mechanisms to make the rule of PRG be obliged to obey. A new joining node must ask the Certificate Authority (CA) for its signature and certificate, which records the complete process on how a node joins the network and obtains the legitimacy of the node. Then, to prevent the adversary from accumulating identifiers, any node can make use of the latest certificate to judge whether one identifier is expired with the help of the replacement property of RPG. This paper analyzes in details the number of expired certificates which are needed to store in every node, and gives asymptotic solution of this problem. The analysis and simulations show that the mean number of the certificates stored in each node are , where n is the size of the network. PMID:23776485

  20. Dynamic bed reactor

    DOEpatents

    Stormo, Keith E.

    1996-07-02

    A dynamic bed reactor is disclosed in which a compressible open cell foam matrix is periodically compressed and expanded to move a liquid or fluid through the matrix. In preferred embodiments, the matrix contains an active material such as an enzyme, biological cell, chelating agent, oligonucleotide, adsorbent or other material that acts upon the liquid or fluid passing through the matrix. The active material may be physically immobilized in the matrix, or attached by covalent or ionic bonds. Microbeads, substantially all of which have diameters less than 50 microns, can be used to immobilize the active material in the matrix and further improve reactor efficiency. A particularly preferred matrix is made of open cell polyurethane foam, which adsorbs pollutants such as polychlorophenol or o-nitrophenol. The reactors of the present invention allow unidirectional non-laminar flow through the matrix, and promote intimate exposure of liquid reactants to active agents such as microorganisms immobilized in the matrix.

  1. Dynamic bed reactor

    SciTech Connect

    Stormo, K.E.

    1996-07-02

    A dynamic bed reactor is disclosed in which a compressible open cell foam matrix is periodically compressed and expanded to move a liquid or fluid through the matrix. In preferred embodiments, the matrix contains an active material such as an enzyme, biological cell, chelating agent, oligonucleotide, adsorbent or other material that acts upon the liquid or fluid passing through the matrix. The active material may be physically immobilized in the matrix, or attached by covalent or ionic bonds. Microbeads, substantially all of which have diameters less than 50 microns, can be used to immobilize the active material in the matrix and further improve reactor efficiency. A particularly preferred matrix is made of open cell polyurethane foam, which adsorbs pollutants such as polychlorophenol or o-nitrophenol. The reactors of the present invention allow unidirectional non-laminar flow through the matrix, and promote intimate exposure of liquid reactants to active agents such as microorganisms immobilized in the matrix. 27 figs.

  2. Positron annihilation in transparent ceramics

    NASA Astrophysics Data System (ADS)

    Husband, P.; Bartošová, I.; Slugeň, V.; Selim, F. A.

    2016-01-01

    Transparent ceramics are emerging as excellent candidates for many photonic applications including laser, scintillation and illumination. However achieving perfect transparency is essential in these applications and requires high technology processing and complete understanding for the ceramic microstructure and its effect on the optical properties. Positron annihilation spectroscopy (PAS) is the perfect tool to study porosity and defects. It has been applied to investigate many ceramic structures; and transparent ceramics field may be greatly advanced by applying PAS. In this work positron lifetime (PLT) measurements were carried out in parallel with optical studies on yttrium aluminum garnet transparent ceramics in order to gain an understanding for their structure at the atomic level and its effect on the transparency and light scattering. The study confirmed that PAS can provide useful information on their microstructure and guide the technology of manufacturing and advancing transparent ceramics.

  3. Ceramic hot-gas filter

    DOEpatents

    Connolly, E.S.; Forsythe, G.D.; Domanski, D.M.; Chambers, J.A.; Rajendran, G.P.

    1999-05-11

    A ceramic hot-gas candle filter is described having a porous support of filament-wound oxide ceramic yarn at least partially surrounded by a porous refractory oxide ceramic matrix, and a membrane layer on at least one surface thereof. The membrane layer may be on the outer surface, the inner surface, or both the outer and inner surface of the porous support. The membrane layer may be formed of an ordered arrangement of circularly wound, continuous filament oxide ceramic yarn, a ceramic filler material which is less permeable than the filament-wound support structure, or some combination of continuous filament and filler material. A particularly effective membrane layer features circularly wound filament with gaps intentionally placed between adjacent windings, and a filler material of ceramic particulates uniformly distributed throughout the gap region. The filter can withstand thermal cycling during back pulse cleaning and is resistant to chemical degradation at high temperatures.

  4. Ceramic hot-gas filter

    DOEpatents

    Connolly, Elizabeth Sokolinski; Forsythe, George Daniel; Domanski, Daniel Matthew; Chambers, Jeffrey Allen; Rajendran, Govindasamy Paramasivam

    1999-01-01

    A ceramic hot-gas candle filter having a porous support of filament-wound oxide ceramic yarn at least partially surrounded by a porous refractory oxide ceramic matrix, and a membrane layer on at least one surface thereof. The membrane layer may be on the outer surface, the inner surface, or both the outer and inner surface of the porous support. The membrane layer may be formed of an ordered arrangement of circularly wound, continuous filament oxide ceramic yarn, a ceramic filler material which is less permeable than the filament-wound support structure, or some combination of continuous filament and filler material. A particularly effective membrane layer features circularly wound filament with gaps intentionally placed between adjacent windings, and a filler material of ceramic particulates uniformly distributed throughout the gap region. The filter can withstand thermal cycling during backpulse cleaning and is resistant to chemical degradation at high temperatures.

  5. Ability of bed bug-detecting canines to locate live bed bugs and viable bed bug eggs.

    PubMed

    Pfiester, Margie; Koehler, Philip G; Pereira, Roberto M

    2008-08-01

    The bed bug, Cimex lectularius L., like other bed bug species, is difficult to visually locate because it is cryptic. Detector dogs are useful for locating bed bugs because they use olfaction rather than vision. Dogs were trained to detect the bed bug (as few as one adult male or female) and viable bed bug eggs (five, collected 5-6 d after feeding) by using a modified food and verbal reward system. Their efficacy was tested with bed bugs and viable bed bug eggs placed in vented polyvinyl chloride containers. Dogs were able to discriminate bed bugs from Camponotus floridanus Buckley, Blattella germanica (L.), and Reticulitermes flavipes (Kollar), with a 97.5% positive indication rate (correct indication of bed bugs when present) and 0% false positives (incorrect indication of bed bugs when not present). Dogs also were able to discriminate live bed bugs and viable bed bug eggs from dead bed bugs, cast skins, and feces, with a 95% positive indication rate and a 3% false positive rate on bed bug feces. In a controlled experiment in hotel rooms, dogs were 98% accurate in locating live bed bugs. A pseudoscent prepared from pentane extraction of bed bugs was recognized by trained dogs as bed bug scent (100% indication). The pseudoscent could be used to facilitate detector dog training and quality assurance programs. If trained properly, dogs can be used effectively to locate live bed bugs and viable bed bug eggs. PMID:18767752

  6. Laser machining of ceramic

    SciTech Connect

    Laudel, A.

    1980-01-01

    The Kansas City Division of The Bendix Corporation manufactures hybrid microcircuits (HMCs) using both thin film and thick film technologies. Laser machining is used to contour the ceramic substrates and to drill holes in the ceramic for frontside-backside interconnections (vias) and holes for mounting components. A 1000 W CO/sub 2/ type laser is used. The laser machining process, and methods used for removing protruding debris and debris from holes, for cleaning the machined surfaces, and for refiring are described. The laser machining process described consistently produces vias, component holes and contours with acceptable surface quality, hole locations, diameter, flatness and metallization adhesion. There are no cracks indicated by dipping in fluorescent dye penetrant and the substances are resistant to repeated thermal shock.

  7. Ceramic composite coating

    DOEpatents

    Wicks, George G.

    1997-01-01

    A thin, room-temperature-curing, ceramic composite for coating and patching etal substrates comprises a sol gel silica glass matrix filled with finely ground particles or fibers, preferably alumina. The sol gel glass is made by adding ethanol to water to form a first mixture, then separately adding ethanol to tetraethyl orthosilicate to form a second mixture, then slowly adding the first to the second mixture to make a third mixture, and making a slurry by adding the finely ground particles or fibers to the third mixture. The composite can be applied by spraying, brushing or trowelling. If applied to patch fine cracks, densification of the ceramic composite may be obtained to enhance sealing by applying heat during curing.

  8. Ceramic composite coating

    DOEpatents

    Wicks, G.G.

    1997-01-21

    A thin, room-temperature-curing, ceramic composite for coating and patching metal substrates comprises a sol gel silica glass matrix filled with finely ground particles or fibers, preferably alumina. The sol gel glass is made by adding ethanol to water to form a first mixture, then separately adding ethanol to tetraethyl orthosilicate to form a second mixture, then slowly adding the first to the second mixture to make a third mixture, and making a slurry by adding the finely ground particles or fibers to the third mixture. The composite can be applied by spraying, brushing or trowelling. If applied to patch fine cracks, densification of the ceramic composite may be obtained to enhance sealing by applying heat during curing.

  9. Laser in Ceramics Processing

    NASA Astrophysics Data System (ADS)

    Lal, Bajrang; Jain, Pankaj

    LASER, an acronym for Light Amplification by Stimulated Emission of Radiation have unique properties, Which make it differ from ordinary light such as it is highly coherent, monochromatic, negligible divergence and scattering loss and a intense beam of electromagnetic radiation or light. It also occur in a wide range of wavelength/frequency (from Ultraviolet to Infrared), energy/power and beam-mode/configurations ; Due to these unique properties, it have use in wide application of ceramic processing for industrial manufacturing, fabrication of electronic circuit such as marking, serializing, engraving, cutting, micro-structuring because laser only produces localized heating, without any contact and thermal stress on the any part during processing. So there is no risk of fracturing that occurs during mechanical sawing and also reduce Cost of processing. The discussion in this paper highlight the application of laser in ceramics processing.

  10. Ceramics for fusion applications

    SciTech Connect

    Clinard, F.W. Jr.

    1986-01-01

    Ceramics are required for a variety of uses in both near-term fusion devices and in commercial powerplants. These materials must retain adequate structural and electrical properties under conditions of neutron, particle, and ionizing irradiation; thermal and applied stresses; and physical and chemical sputtering. Ceramics such as Al/sub 2/O/sub 3/, MgAl/sub 2/O/sub 4/, BeO, Si/sub 3/N/sub 4/ and SiC are currently under study for fusion applications, and results to date show widely-varying response to the fusion environment. Materials can be identified today which will meet initial operating requirements, but improvements in physical properties are needed to achieve satisfactory lifetimes for critical applications.

  11. Ceramic Composite Thin Films

    NASA Technical Reports Server (NTRS)

    Ruoff, Rodney S. (Inventor); Stankovich, Sasha (Inventor); Dikin, Dmitriy A. (Inventor); Nguyen, SonBinh T. (Inventor)

    2013-01-01

    A ceramic composite thin film or layer includes individual graphene oxide and/or electrically conductive graphene sheets dispersed in a ceramic (e.g. silica) matrix. The thin film or layer can be electrically conductive film or layer depending the amount of graphene sheets present. The composite films or layers are transparent, chemically inert and compatible with both glass and hydrophilic SiOx/silicon substrates. The composite film or layer can be produced by making a suspension of graphene oxide sheet fragments, introducing a silica-precursor or silica to the suspension to form a sol, depositing the sol on a substrate as thin film or layer, at least partially reducing the graphene oxide sheets to conductive graphene sheets, and thermally consolidating the thin film or layer to form a silica matrix in which the graphene oxide and/or graphene sheets are dispersed.

  12. Pulsed atmospheric fluidized bed combustion

    SciTech Connect

    Not Available

    1992-08-01

    The general specifications for a Pulsed Atmospheric Fluidized Bed Combustor Design Report (PAFBC) plant are presented. The design tasks for the PAFBC are described in the following areas: Coal/Limestone preparation and feed system; pulse combustor; fluidized bed; boiler parts; and ash handling system.

  13. LSP Composite Test Bed Design

    NASA Technical Reports Server (NTRS)

    Day, Arthur C.; Griess, Kenneth H.

    2013-01-01

    This document provides standalone information for the Lightning Strike Protection (LSP) Composite Substrate Test Bed Design. A six-sheet drawing set is reproduced for reference, as is some additional descriptive information on suitable sensors and use of the test bed.

  14. Seal between metal and ceramic conduits

    DOEpatents

    Underwood, Richard Paul; Tentarelli, Stephen Clyde

    2015-02-03

    A seal between a ceramic conduit and a metal conduit of an ion transport membrane device consisting of a sealing surface of ceramic conduit, a sealing surface of ceramic conduit, a single gasket body, and a single compliant interlayer.

  15. Multifracture of ceramic composites

    SciTech Connect

    Weitsman, Y.J.; Zhu, H.

    1992-03-01

    This work presents a mechanistic model for the multifracture process of uniaxially reinforced fibrous ceramic composites under monotonically increasing tension parallel to the fiber direction. The model employs an energy criterion to account for the progression of matrix cracks, bridged by intact fibers, and Weibull failure statistics to relate the failure of the fibers. Consideration is given to the interactions between the foregoing failure processes as well as to the effects of various material parameters on the response of the composite.

  16. Microprobes aluminosilicate ceramic membranes

    DOEpatents

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

    Methods have been developed to make mixed alumina-silicate and aluminosilicate particulate microporous ceramic membranes. One method involves the making of separate alumina and silica sols which are then mixed. Another method involves the creation of a combined sol with aluminosilicate particles. The resulting combined alumina and silica membranes have high surface area, a very small pore size, and a very good temperature stability.

  17. Miniature ceramic fuel cell

    DOEpatents

    Lessing, Paul A.; Zuppero, Anthony C.

    1997-06-24

    A miniature power source assembly capable of providing portable electricity is provided. A preferred embodiment of the power source assembly employing a fuel tank, fuel pump and control, air pump, heat management system, power chamber, power conditioning and power storage. The power chamber utilizes a ceramic fuel cell to produce the electricity. Incoming hydro carbon fuel is automatically reformed within the power chamber. Electrochemical combustion of hydrogen then produces electricity.

  18. Joined ceramic product

    DOEpatents

    Henager, Jr., Charles W [Kennewick, WA; Brimhall, John L [West Richland, WA

    2001-08-21

    According to the present invention, a joined product is at least two ceramic parts, specifically bi-element carbide parts with a bond joint therebetween, wherein the bond joint has a metal silicon phase. The bi-element carbide refers to compounds of MC, M.sub.2 C, M.sub.4 C and combinations thereof, where M is a first element and C is carbon. The metal silicon phase may be a metal silicon carbide ternary phase, or a metal silicide.

  19. Superplastic forging nitride ceramics

    DOEpatents

    Panda, Prakash C.; Seydel, Edgar R.; Raj, Rishi

    1988-03-22

    The invention relates to producing relatively flaw free silicon nitride ceramic shapes requiring little or no machining by superplastic forging This invention herein was made in part under Department of Energy Grant DE-AC01-84ER80167, creating certain rights in the United States Government. The invention was also made in part under New York State Science and Technology Grant SB1R 1985-10.

  20. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2001-12-01

    Conversion of natural gas to liquid fuels and chemicals is a major goal for the Nation as it enters the 21st Century. Technically robust and economically viable processes are needed to capture the value of the vast reserves of natural gas on Alaska's North Slope, and wean the Nation from dependence on foreign petroleum sources. Technologies that are emerging to fulfill this need are all based syngas as an intermediate. Syngas (a mixture of hydrogen and carbon monoxide) is a fundamental building block from which chemicals and fuels can be derived. Lower cost syngas translates directly into more cost-competitive fuels and chemicals. The currently practiced commercial technology for making syngas is either steam methane reforming (SMR) or a two-step process involving cryogenic oxygen separation followed by natural gas partial oxidation (POX). These high-energy, capital-intensive processes do not always produce syngas at a cost that makes its derivatives competitive with current petroleum-based fuels and chemicals. This project has the following 6 main tasks: Task 1--Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. Task 2--Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. Task 3--Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. Task 4--Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. Task 5--Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. Task 6--Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.