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Neutronic data in support of space nuclear propulsion

Description: The thermophysical properties of lithium hydride ({sup 7}LiH), particularly small density (0.775 gm/cc), high melting point (688 C) and relatively high hydrogen atomic number density makes it an attractive material for use as a neutron moderator and shield (for LiH) in space nuclear thermal propulsion. However, the unavailability of neutronic cross section data in the thermal energy range for {sup 7}LiH in the ENDF/B library necessitated the generation of the relevant data which is required in criticality studies and for the determination of temperature-dependent feedback coefficients in the moderator and fuel regions. Here, the scattering kernel data for {sup 7}LiH have been generated for the first time in the temperature range 50--1,000 K. This is based on a phonon distribution function derived from both experimental data and theoretical calculations. A detailed study of the variation of the moderator temperature coefficient {alpha}{sub m}(T) with temperature, T, is carried out for a typical space nuclear reactor of the particle bed type. It is established that the moderator temperature coefficient is proportional to T{sup {minus}1.65} where T is the moderator temperature in Kelvin units.
Date: July 1, 1997
Creator: Mughabghab, S.; Schmidt, E. & Ludewig, H.
Partner: UNT Libraries Government Documents Department

Milliwatt Generator Project: April 1988--September 1996. Progress report

Description: This report covers progress on the Milliwatt Generator (MWG) Project from April 1988 to September 1996. Manufacturing of heat sources for the project ended by September 1990. Beginning in October 1990, the major activities of the project have been surveillance and testing of MWGs, disposal of excess MWGs, and reclamation of the PuO{sub 2} from excess MWG heat sources. Reported activities include fuel processing and characterization, production of heat sources, compatibility studies, impact testing, examination and electrical testing of surveillance units, and recovery of PuO{sub 2} from heat sources.
Date: July 1, 1997
Creator: Latimer, T.W.
Partner: UNT Libraries Government Documents Department

Human factors aspects of the major upgrade to control systems at the Los Alamos National Laboratory Plutonium Facility

Description: The Plutonium Facility (TA-55) at Los Alamos National Laboratory (LANL) has been in operation for over 15 years. It handles projects such as: stockpile maintenance, surveillance, and dismantlement; pit rebuild; plutonium power source fabrication for long duration spacecraft missions (e.g., Cassini); nuclear materials technology research; nuclear materials storage; and remediation of nuclear waste. The Operations Center of TA-55 is the nerve center of the facility where operators are on duty around the clock and monitor several thousand data points using the Facility Control System (FCS). The FCS monitors, displays, alarms, and provides some limited control of the following systems; HVAC, fire detection and suppression, radiation detection, electrical, and other miscellaneous systems. The FCS was originally based on late 1970s digital technology, which is not longer supported by the vendors. Additionally, the equipment failure rates increased notably in the 1990s. Thus, plans were put into place to upgrade and replace the FCS hardware, software, and display components with modernized equipment. The process was complicated by the facts that: the facility was operational and could not be totally closed for the modifications; complete documentation was not available for the existing system; the Safety Analyses for the facility were in the process of being upgraded at the same time; and of course limited time and budgets. This paper will discuss the human factors aspects of the design, installation, and testing of the new FCS within the above noted constraints. Particular items to be discussed include the functional requirements definition, operating experience review, screen designs, test program, operator training, and phased activation of the new circuits in an operational facility.
Date: June 1, 1997
Creator: Higgins, J. & Pope, N.
Partner: UNT Libraries Government Documents Department

FRG sealed isotopic heat sources project (C-229) project management plan

Description: This Project Management Plan defines the cost, scope, schedule, organizational responsibilities, and work breakdown structure for the removal of the Federal Republic of Germany (FRG) Sealed Isotopic Heat Sources from the 324 Building and placed in interim storage at the Central Waste Complex (CWC).
Date: May 16, 1997
Creator: Metcalf, I.L.
Partner: UNT Libraries Government Documents Department

Fuel elements of thermionic converters

Description: Work on thermionic nuclear power systems has been performed in Russia within the framework of the TOPAZ reactor program since the early 1960s. In the TOPAZ in-core thermionic convertor reactor design, the fuel element`s cladding is also the thermionic convertor`s emitter. Deformation of the emitter can lead to short-circuiting and is the primary cause of premature TRC failure. Such deformation can be the result of fuel swelling, thermocycling, or increased unilateral pressure on the emitter due to the release of gaseous fission products. Much of the work on TRCs has concentrated on preventing or mitigating emitter deformation by improving the following materials and structures: nuclear fuel; emitter materials; electrical insulators; moderator and reflector materials; and gas-exhaust device. In addition, considerable effort has been directed toward the development of experimental techniques that accurately mimic operational conditions and toward the creation of analytical and numerical models that allow operational conditions and behavior to be predicted without the expense and time demands of in-pile tests. New and modified materials and structures for the cores of thermionic NPSs and new fabrication processes for the materials have ensured the possibility of creating thermionic NPSs for a wide range of powers, from tens to several hundreds of kilowatts, with life spans of 5 to 10 years.
Date: January 1, 1997
Creator: Hunter, R.L.; Gontar, A.S.; Nelidov, M.V.; Nikolaev, Yu.V. & Schulepov, L.N.
Partner: UNT Libraries Government Documents Department

FSAR fire accident analysis for a plutonium facility

Description: The Final Safety Analysis Report (FSAR) for a plutonium facility as required by DOE Orders 5480.23 and 5480.22 has recently been completed and approved. The facility processes and stores radionuclides such as Pu-238, Pu-239, enriched uranium, and to a lesser degree other actinides. This facility produces heat sources. DOE Order 5480.23 and DOE-STD-3009-94 require analysis of different types of accidents (operational accidents such as fires, explosions, spills, criticality events, and natural phenomena such as earthquakes). The accidents that were analyzed quantitatively, or the Evaluation Basis Accidents (EBAs), were selected based on a multi-step screening process that utilizes extensively the Hazards Analysis (HA) performed for the facility. In the HA, specific accident scenarios, with estimated frequency and consequences, were developed for each identified hazard associated with facility operations and activities. Analysis of the EBAs and comparison of their consequences to the evaluation guidelines established the safety envelope for the facility and identified the safety-class structures, systems, and components. This paper discusses the analysis of the fire EBA. This fire accident was analyzed in relatively great detail in the FSAR because of its potential off-site consequences are more severe compared to other events. In the following, a description of the scenario is first given, followed by a brief summary of the methodology for calculating the source term. Finally, the author discuss how a key parameter affecting the source term, the leakpath factor, was determined, which is the focus of this paper.
Date: June 1, 1997
Creator: Lam, K.
Partner: UNT Libraries Government Documents Department

NET-1.2 post-irradiation examination report

Description: The post-irradiation examination (PIE) of the NET-1.2 fuel element was completed in December, 1993. The goal of the PIE work was to gather data regarding the fracture of the hot frit during the experiment. Five cracks were observed in the hot frit at various locations although only two were believed to have initiated the overall component failure. These two cracks were complete circumferential failures and were located near the open and closed ends of the frit within the active flow region. The location and orientation of these fractures suggested that failure was the result of thermally-induced stresses that exceeded pre-test predictions. The cause of the failure was the temperature difference between the coolant flowing through the hot frit and the thermally massive end fittings. The resulting axial temperature gradients in the hot frit imposed thermal stresses that exceeded failure in the frit coating material. This coating fracture then propagated through the graphite substrate. Post-test analyses of the frit response based on measured data from the experiment verified that the frit coating failure stresses were exceeded. Additionally, the cold frit behaved unexpectedly. The PIE inspection of this component showed that a majority of the compliant panels were permanently deformed against the cold frit inner wall even though the transients that the bed was exposed to were not thought to be capable of creating this magnitude of bed expansion. No evidence of bed locking was observed. A calculational error in the prediction of the total bed expansion was found (post-PIE) which certainly contributed to the underestimation of the bed displacement. Additionally, temperature differences between the bulk of the frit and the panels created a bowing force which may have allowed some amount of bed settling at relatively low temperatures while particle thermal expansion was minimal.
Date: June 1, 1997
Creator: Rightley, M.; Ales, M. & Bourcier, S.
Partner: UNT Libraries Government Documents Department

Exposure calculations for the FRG isotopic heat source projectenvironmental assessment

Description: The report documents the maximum exposure for transfer of the Federal Republic of Germany (FRG) Isotopic Heat Sources from the 324 Building and placed in interim storage at the Central Waste Complex (CWC). These results are to be reported in the Environmental Assessment DOE-EA- 1 21 1.
Date: June 17, 1997
Creator: Metcalf, I.L.
Partner: UNT Libraries Government Documents Department

Heatpipe power system and heatpipe bimodal system design and development options

Description: The Heatpipe Power System (HPS) is a potential, near-term, low-cost space fission power system. The Heatpipe Bimodal System (HBS) is a potential, near-term, low-cost space fission power and/or propulsion system. Both systems will be composed of independent modules, and all components operate within the existing databases. The HPS and HBS have relatively few system integration issues; thus, the successful development of a module is a significant step toward verifying system feasibility and performance estimates. A prototypic HPS module is being fabricated, and testing is scheduled to begin in November 1996. A successful test will provide high confidence that the HPS can achieve its predicted performance.
Date: February 1, 1997
Creator: Houts, M.G.; Poston, D.I. & Emrich, W.J. Jr.
Partner: UNT Libraries Government Documents Department

The Tower Shielding Facility: Its glorious past

Description: The Tower Shielding Facility (TSF) is the only reactor facility in the US that was designed and built for radiation-shielding studies in which both the reactor source and shield samples could be raised into the air to allow measurements to be made without interference from ground scattering or other spurious effects. The TSF proved its usefulness as many different programs were successfully completed. It became active in work for the Defense Atomic Support Agency (DASA) Space Nuclear Auxiliary Power, Defense Nuclear Agency, Liquid Metal Fast Breeder Reactor Program, the Gas-Cooled and High-Temperature Gas-Cooled Reactor programs, and the Japanese-American Shielding Program of Experimental Research, just to mention a few of the more extensive ones. The history of the TSF as presented in this report describes the various experiments that were performed using the different reactors. The experiments are categorized as to the programs which they supported and placed in corresponding chapters. The experiments are described in modest detail, along with their purpose when appropriate. Discussion of the results is minimal, but references are given to more extensive topical reports.
Date: May 7, 1997
Creator: Muckenthaler, F.J.
Partner: UNT Libraries Government Documents Department

GPHS-RTGs in support of the Cassini Mission. Semi annual technical report, 30 September 1996--30 March 1997

Description: The technical progress achieved during the period 27 January through 30 September 1996 through 30 March 1997 on Contract DE-AC03-91SF18852 Radioisotope Thermoelectric Generators and Ancillary Activities is described. This report is organized by program task structure: spacecraft integration and liaison; engineering support; safety; qualified unicouple production; ETG fabrication, assembly, and test; ground support equipment (GSE); RTG shipping and launch support; designs, reviews, and mission applications; project management, quality assurance, reliability, contract changes, CAGO acquisition (operating funds), and CAGO maintenance and repair; and CAGO acquisition (capital funds).
Date: April 20, 1997
Partner: UNT Libraries Government Documents Department

High-silicon {sup 238}PuO{sub 2} fuel characterization study: Half module impact tests

Description: The General-Purpose Heat Source (GPHS) provides power for space missions by transmitting the heat of [sup 238]Pu decay to an array of thermoelectric elements. The modular GPHS design was developed to address both survivability during launch abort and return from orbit. Previous testing conducted in support of the Galileo and Ulysses missions documented the response of GPHSs to a variety of fragment- impact, aging, atmospheric reentry, and Earth-impact conditions. The evaluations documented in this report are part of an ongoing program to determine the effect of fuel impurities on the response of the heat source to conditions baselined during the Galileo/Ulysses test program. In the first two tests in this series, encapsulated GPHS fuel pellets containing high levels of silicon were aged, loaded into GPHS module halves, and impacted against steel plates. The results show no significant differences between the response of these capsules and the behavior of relatively low-silicon fuel pellets tested previously.
Date: January 1, 1997
Creator: Reimus, M.A.H.
Partner: UNT Libraries Government Documents Department

Balance-of-plant options for the Heat-Pipe Power System

Description: The Heat-Pipe Power System (HPS) is a near-term, low-cost space fission power system with the potential for utilizing various option for balance-of-plant options. The following options have been studied: a low-power thermoelectric design (14-kWe output), a small Brayton cycle system (60--75 kWe), and a large Brayton cycle system (250 kWe). These systems were analyzed on a preliminary basis, including mass, volume, and structure calculations. These analyses have shown that the HPS system can provide power outputs from 10--250 kWe with specific powers of {approximately} 14 W/kg for a 14-kWe model to {approximately} 100 W/kg for a 250-kWe model. The system designs considered in this study utilize a common component base to permit easy expansion and development.
Date: September 1, 1997
Creator: Berte, M. & Capell, B.
Partner: UNT Libraries Government Documents Department

Light weight radioisotope heater unit (LWRHU) production for the Cassini mission

Description: The Light-Weight Radioisotope Heater Unit (LWRHU) is a [sup 238]PuO[sub 2] fueled heat source designed to provide one thermal watt in each of various locations on a spacecraft. The heat sources are required to maintain the temperature of specific components within normal operating ranges. The heat source consists of a hot- pressed [sup 238]PuO[sub 2] fuel pellet, a Pt-3ORh vented capsule, a pyrolytic graphite insulator, and a woven graphite aeroshell assembly. Los Alamos National Laboratory has fabricated 180 heat sources, 157 of which will be used on the Cassini mission.
Date: January 1, 1997
Creator: Rinehart, G.H.
Partner: UNT Libraries Government Documents Department

Cassini RTG acceptance test results and RTG performance on Galileo and Ulysses

Description: Flight acceptance testing has been completed for the RTGs to be used on the Cassini spacecraft which is scheduled for an October 6, 1997 launch to Saturn. The acceptance test program includes vibration tests, magnetic field measurements, properties (weight and c.g.) and thermal vacuum test. This paper presents The thermal vacuum test results. Three RTGs are to be used, F-2, F-6, and F-7. F-5 is tile back-up RTG, as it was for the Galileo and Ulysses missions launched in 1989 and 1990, respectively. RTG performance measured during the thermal vacuum tests carried out at die Mound Laboratory facility met all specification requirements. Beginning of mission (BOM) and end of mission (EOM) power predictions have been made based on than tests results. BOM power is predicted to be 888 watts compared to the minimum requirement of 826 watts. Degradation models predict the EOM power after 16 years is to be 640 watts compared to a minimum requirement of 596 watts. Results of small scale module tests are also showing. The modules contain couples from the qualification and flight production runs. The tests have exceeded 28,000 hours (3.2 years) and are continuing to provide increased confidence in the predicted long term performance of the Cassini RTGs. All test results indicate that the power requirements of the Cassini spacecraft will be met. BOM and EOM power margins of over five percent are predicted. Power output from telemetry for the two Galileo RTGs are shown from the 1989 launch to the recent Jupiter encounter. Comparisons of predicted, measured and required performance are shown. Telemetry data are also shown for the RTG on the Ulysses spacecraft which completed its planned mission in 1995 and is now in the extended mission.
Date: June 1, 1997
Creator: Kelly, C.E. & Klee, P.M.
Partner: UNT Libraries Government Documents Department

Nuclear thermal rocket plume interactions with spacecraft. Final report

Description: This is the first study that has treated the Nuclear Thermal Rocket (NTR) effluent problem in its entirety, beginning with the reactor core, through the nozzle flow, to the plume backflow. The summary of major accomplishments is given below: (1) Determined the NTR effluents that include neutral, ionized and radioactive species, under typical NTR chamber conditions. Applied an NTR chamber chemistry model that includes conditions and used nozzle geometries and chamber conditions typical of NTR configurations. (2) Performed NTR nozzle flow simulations using a Navier-Stokes solver. We assumed frozen chemistry at the chamber conditions and used nozzle geometries and chamber conditions typical of NTR configurations. (3) Performed plume simulations using a Direct Simulation Monte Carlo (DSMC) code with chemistry. In order to account for radioactive trace species that may be important for contamination purposes we developed a multi-weighted DSMC methodology. The domain in our simulations included large regions downstream and upstream of the exit. Inputs were taken from the Navier-Stokes solutions.
Date: May 1, 1997
Creator: Mauk, B. H.; Gatsonis, N. A.; Buzby, J. & Yin, X.
Partner: UNT Libraries Government Documents Department

The Cassini project: Lessons learned through operations

Description: The Cassini space probe requires 180 {sup 238}Pu Light-weight Radioisotopic Heater Units (LWRHU) and 216 {sup 238}Pu General Purpose Heat Source (GPHS) pellets. Additional LWRHU and GPHS pellets required for non-destructive (NDA) and destructive assay purposes were fabricated bringing the original pellet requirement to 224 LWRHU and 252 GPHS. Due to rejection of pellets resulting from chemical impurities in the fuel and/or failure to meet dimensional specifications a total of 320 GPHS pellets were fabricated for the mission. Initial plans called for LANL to process a total of 30 kg of oxide powder for pressing into monolithic ceramic pellets. The original 30 kg commitment was processed within the time frame allotted; an additional 8 kg were required to replace fuel lost due to failure to meet Quality Assurance specifications for impurities and dimensions. During the time frame allotted for pellet production, operations were impacted by equipment failure, unacceptable fuel impurities levels, and periods of extended down time, > 30 working days during which little or no processing occurred. Throughout and production process, the reality of operations requirements varied from the theory upon which production schedules were based.
Date: December 31, 1997
Creator: McCormick, E.D.
Partner: UNT Libraries Government Documents Department

RSMASS-D models: An improved method for estimating reactor and shield mass for space reactor applications

Description: Three relatively simple mathematical models have been developed to estimate minimum reactor and radiation shield masses for liquid-metal-cooled reactors (LMRs), in-core thermionic fuel element (TFE) reactors, and out-of-core thermionic reactors (OTRs). The approach was based on much of the methodology developed for the Reactor/Shield Mass (RSMASS) model. Like the original RSMASS models, the new RSMASS-derivative (RSMASS-D) models use a combination of simple equations derived from reactor physics and other fundamental considerations, along with tabulations of data from more detailed neutron and gamma transport theory computations. All three models vary basic design parameters within a range specified by the user to achieve a parameter choice that yields a minimum mass for the power level and operational time of interest. The impact of critical mass, fuel damage, and thermal limitations are accounted for to determine the required fuel mass. The effect of thermionic limitations are also taken into account for the thermionic reactor models. All major reactor component masses are estimated, as well as instrumentation and control (I&C), boom, and safety system masses. A new shield model was developed and incorporated into all three reactor concept models. The new shield model is more accurate and simpler to use than the approach used in the original RSMASS model. The estimated reactor and shield masses agree with the mass predictions from separate detailed calculations within 15 percent for all three models.
Date: October 1, 1997
Creator: Marshall, A.C.
Partner: UNT Libraries Government Documents Department

Cassini RTG program. Monthly technical progress report, September 29, 1997--October 26, 1997

Description: This report describes work on the contract to provide Radioisotope Thermoelectric Generators (RTG) and Ancillary Activities in support of the Cassini Spacecraft launch. The craft was successfully launched on October 15, 1997. Early telemetry results show excellent performance from the three launched RTG modules. A major share of this report describes safety analyses for contamination radii in the event of launch failures and generator destruction, as well as launch related activities.
Date: November 24, 1997
Partner: UNT Libraries Government Documents Department

Design and operation of the Rover vacuum system

Description: The Rover process for recovering unused uranium from graphite fuels was operated during 1983 and 1984, and then shut down in 1984. The first steps of the process used fluidized alumina beds to burn away the graphite and produce a uranium bearing ash. The ash was then transferred to a different process cell for acid dissolution. At the time of shutdown, a significant, but unmeasureable, quantity of highly enriched uranium was left in the process vessels. Normal decontamination procedures could not be used due to plugged process lines and the exclusion of moderator materials (water or finely divided organic substances) for criticality safety. The presence of highly enriched uranium in poorly defined quantity and configuration led to concerns for criticality safety, nuclear materials accountability, and physical security. A project was established to eliminate these concerns by cleaning and/or removing the process vessels, piping, and cells and sending the recovered Uranium Bearing Material (UBM) to secure storage. A key element of this project was the design of a system for collecting and transporting dry solids to a location where they could be loaded into critically favorable storage cans.
Date: August 1, 1997
Creator: Wagner, E.P. Jr.; Griffith, D.L. & Rivera, J.M.
Partner: UNT Libraries Government Documents Department

Light-Weight Radioisotope Heater Unit (LWRHU) sequential impact tests

Description: The light-weight radioisotope heater unit (LWRHU) is a {sup 238}PuO{sub 2}-fueled heat source designed to provide one thermal watt in each of various locations on a spacecraft. Los Alamos National Laboratory designed, fabricated, and safety tested the LWRHU. The heat source consists of a hot-pressed {sup 238}PuO{sub 2} fuel pellet, a Pt-30Rh vented capsule, a pyrolytic graphite insulator, and a fineweave-pierced fabric graphite aeroshell assembly. A series of sequential impacts tests using simulant-fueled LWRHU capsules was recently conducted to determine a failure threshold. Sequential impacting, in both end-on and side-on orientations, resulted in increased damage with each subsequent impact. Although the tests were conducted until the aeroshells were sufficiently distorted to be out of dimensional specification, the simulant-fueled capsules used in these tests were not severely deformed. Sequential impacting of the LWRHU appears to result in slightly greater damage than a single impact at the final impact velocity of 50 m/s. Postimpact examination revealed that the sequentially impacted capsules were slightly more deformed and were outside of dimensional specifications.
Date: August 1, 1997
Creator: Reimus, M.A.H. & Rinehart, G.H.
Partner: UNT Libraries Government Documents Department

End-on radioisotope thermoelectric generator impact tests

Description: The General-Purpose Heat Source (GPHS) provides power for space missions by transmitting the heat of [sup 238]Pu decay to an array of thermoelectric elements in a radioisotope thermoelectric generator (RTG). The modular GPHS design was developed to address both survivability during launch abort and return from orbit. The first two RTG Impact Tests were designed to provide information on the response of a fully loaded RTG to end-on impact against a concrete target. The results of these tests indicated that at impact velocities up to 57 m/s the converter shell and internal components protect the GPHS capsules from excessive deformation. At higher velocities, some of the internal components of the RTG interact with the GPHS capsules to cause excessive localized deformation and failure.
Date: January 1, 1997
Creator: Reimus, M.A.H. & Hhinckley, J.E.
Partner: UNT Libraries Government Documents Department

A graded approach to safety analysis for Rover Processing Facility deactivation

Description: The Rover Fuels Processing Facility operated in the early 1980`s, recovering uranium from graphite fuels. In 1996 clean-out began of uranium bearing material remaining in the Rover cells where combustion processes had occurred. Success of the Rover Deactivation Project depends on the safe, timely, and cost-effective repackaging and removal of the uranium bearing material. Due to a number of issues which could not be resolved prior to clean-out, and consideration of cost and schedule objectives, a graded approach was taken to projected design and criticality safety analysis. The safety authorization basis was upgraded primarily by a specific Deactivation addendum, instead of being completely rewritten to current format and content standards. In place of having all design activities completed prior to the start of the Deactivation, the project design and accompanying safety documentation evolved as the project progressed. The Unreviewed Safety Question determination process was used to ensure that new project activities were within the safety envelope. This graded approach allowed operational flexibility while maintaining a critically safe work environment.
Date: August 1, 1997
Creator: Henrikson, D.J.
Partner: UNT Libraries Government Documents Department