9 Matching Results

Search Results

Advanced search parameters have been applied.

Post-Irradiation Examination of Array Targets - Part I

Description: During FY 2001, two arrays, each containing seven neptunium-loaded targets, were irradiated at the Advanced Test Reactor in Idaho to examine the influence of multi-target self-shielding on {sup 236}Pu content and to evaluate fission product release data. One array consisted of seven targets that contained 10 vol% NpO{sub 2} pellets, while the other array consisted of seven targets that contained 20 vol % NpO{sub 2} pellets. The arrays were located in the same irradiation facility but were axially separated to minimize the influence of one array on the other. Each target also contained a dosimeter package, which consisted of a small NpO{sub 2} wire that was inside a vanadium container. After completion of irradiation and shipment back to the Oak Ridge National Laboratory, nine of the targets (four from the 10 vol% array and five from the 20 vol% array) were punctured for pressure measurement and measurement of {sup 85}Kr. These nine targets and the associated dosimeters were then chemically processed to measure the residual neptunium, total plutonium production, {sup 238}Pu production, and {sup 236}Pu concentration at discharge. The amount and isotopic composition of fission products were also measured. This report provides the results of the processing and analysis of the nine targets.
Date: January 23, 2004
Creator: Icenhour, A.S.
Partner: UNT Libraries Government Documents Department

Low work function material development for the microminiature thermionic converter.

Description: Thermionic energy conversion in a miniature format shows potential as a viable, high efficiency, micro to macro-scale power source. A microminiature thermionic converter (MTC) with inter-electrode spacings on the order of microns has been prototyped and evaluated at Sandia. The remaining enabling technology is the development of low work function materials and processes that can be integrated into these converters to increase power production at modest temperatures (800 - 1300 K). The electrode materials are not well understood and the electrode thermionic properties are highly sensitive to manufacturing processes. Advanced theoretical, modeling, and fabrication capabilities are required to achieve optimum performance for MTC diodes. This report describes the modeling and fabrication efforts performed to develop micro dispenser cathodes for use in the MTC.
Date: March 1, 2004
Creator: Zavadil, Kevin Robert; Battaile, Corbett Chandler; Marshall, Albert Christian; King, Donald Bryan & Jennison, Dwight Richard
Partner: UNT Libraries Government Documents Department

Ground Test Facility for Propulsion and Power Modes of Nuclear Engine Operation

Description: Existing DOE Ground Test Facilities have not been used to support nuclear propulsion testing since the Rover/NERVA programs of the 1960's. Unlike the Rover/NERVA programs, DOE Ground Test facilities for space exploration enabling nuclear technologies can no longer be vented to the open atmosphere. The optimal selection of DOE facilities and accompanying modifications for confinement and treatment of exhaust gases will permit the safe testing of NASA Nuclear Propulsion and Power devices involving variable size and source nuclear engines for NASA Jupiter Icy Moon Orbiter (JIMO) and Commercial Space Exploration Missions with minimal cost, schedule and environmental impact. NASA site selection criteria and testing requirements are presented.
Date: November 22, 2004
Creator: Michael, WILLIAMS
Partner: UNT Libraries Government Documents Department

Dissolution of Neptunium and Plutonium Oxides Using a Catalyzed Electrolytic Process

Description: This report discusses the scoping study performed to evaluate the use of a catalyzed electrolytic process for dissolving {sup 237}Np oxide targets that had been irradiated to produce {sup 238}Pu oxide. Historically, these compounds have been difficult to dissolve, and complete dissolution was obtained only by adding hydrofluoric acid to the nitric acid solvent. The presence of fluoride in the mixture is undesired because the fluoride ions are corrosive to tank and piping systems and the fluoride ions cause interferences in the spectrophotometric analyses. The goal is to find a dissolution method that will eliminate these issues and that can be incorporated into a processing system to support the domestic production and purification of {sup 238}Pu. This study evaluated the potential of cerium(IV) ions, a strong oxidant, to attack and dissolve the oxide compounds. In the dissolution process, the cerium(IV) ions are reduced to cerium(III) ions, which are not oxidants. Therefore, an electrolytic process was incorporated to continuously convert cerium(III) ions back to cerium(IV) ions so that they can dissolve more of the oxide compounds. This study showed that the neptunium and plutonium oxides were successfully dissolved and that more development work should be performed to optimize the procedure.
Date: October 25, 2004
Creator: Hylton, TD
Partner: UNT Libraries Government Documents Department

Development of a Robust Tri-Carbide Fueled Reactor for Multimegawatt Space Power and Propulsion Applications

Description: An innovative reactor core design based on advanced, mixed carbide fuels was analyzed for nuclear space power applications. Solid solution, mixed carbide fuels such as (U,Zr,Nb)c and (U,Zr, Ta)C offer great promise as an advanced high temperature fuel for space power reactors.
Date: August 11, 2004
Creator: Anghaie, Samim; Knight, Travis W.; Plancher, Johann & Gouw, Reza
Partner: UNT Libraries Government Documents Department

Annual Technical Progress Report of Radioisotope Power System Materials Production and Technology Program Tasks for October 1, 2002 Through September 30, 2003

Description: The Office of Space and Defense Power Systems of the Department of Energy (DOE) provides Radioisotope Power Systems (RPS) for applications where conventional power systems are not feasible. For example, radioisotope thermoelectric generators were supplied by the DOE to the National Aeronautics and Space Administration for deep space missions including the Cassini Mission launched in October of 1997 to study the planet Saturn. The Oak Ridge National Laboratory (ORNL) has been involved in developing materials and technology and producing components for the DOE for more than three decades. For the Cassini Mission, for example, ORNL was involved in the production of carbon-bonded carbon fiber (CBCF) insulator sets, iridium alloy blanks and foil, and clad vent sets (CVS). This report has been divided into three sections to reflect program guidance from the Office of Space and Defense Power Systems for fiscal year (FY) 2003. The first section deals primarily with maintenance of the capability to produce flight quality (FQ) CBCF insulator sets, iridium alloy blanks and foil, and CVS. In all three cases, production maintenance is assured by the manufacture of limited quantities of FQ components. The second section deals with several technology activities to improve the manufacturing processes, characterize materials, or to develop technologies for new radioisotope power systems. The last section is dedicated to studies related to the production of {sup 238}Pu.
Date: May 18, 2004
Creator: King, J.F.
Partner: UNT Libraries Government Documents Department

Technical Analysis of OnSite Disposal of Space Grade Plutonium Waste

Description: The Risk Based End State Vision Report for the Savannah River Site includes a variance that proposes on-site near surface disposal of waste from the program to produce Pu-238 heat sources for deep space probes. On-site disposal would greatly reduce the risk to workers by eliminating the need to repackage the waste in order to characterize it and ship it to the Waste Isolation Pilot Plant. Significant cost savings can also be realized. A legacy inventory of 6145 m3 containing 590,000 curies of Heat Source plutonium exists at the Savannah River Site. Our plan is to ship as much of this material as possible to the Waste Isolation Pilot Plant using currently available facilities and equipment. We estimate that most of the volume can be safely packaged and transported to WIPP. The remainder, 1813 m3 containing 280,000 curies, is proposed to be disposed of at the SRS after demonstrating that all applicable environmental protection regulations can be met. A technical analysis has been done u sing the overall methodology developed for low-level waste disposal performance assessments. The results to date show that groundwater protection will be maintained, but that enhanced engineering measures are needed to meet the performance measures for protection of inadvertent intruders. The release criterion from 40 CFR 191 is achievable. This analysis provides a means of demonstrating the technical basis on-site disposal of Heat Source plutonium to management, stakeholders and regulators.
Date: December 20, 2004
Creator: James, COOK
Partner: UNT Libraries Government Documents Department

Water Sorption and Radiolysis Studies for Neptunium Oxides

Description: Plans are to convert the {sup 237}Np that is currently stored as a nitrate solution at the Savannah River Site to NpO{sub 2} and then ship it to the Y-12 National Security Complex in Oak Ridge for interim storage. This material will serve as feedstock for the {sup 238}Pu production program, and some will be periodically shipped to the Oak Ridge National Laboratory (ORNL) for fabrication into targets. The safe storage of this material requires an understanding of the radiolysis of moisture that is sorbed on the oxides, which, in turn, provides a basis for storage criteria (namely, moisture content). A two-component experimental program has been undertaken at ORNL to evaluate the radiolytic effects on NpO{sub 2}: (1) moisture uptake experiments and (2) radiolysis experiments using both gamma and alpha radiation. These experiments have produced two key results. First, the water uptake experiments demonstrated that the 0.5 wt % moisture limit that has been typically established for similar materials (e.g., uranium and plutonium oxides) cannot be obtained in a practical environment. In fact, the uptake in a typical environment can be expected to be at least an order of magnitude lower than the limit. The second key result is the establishment of steady-state pressure plateaus as a result of the radiolysis of sorbed moisture. These plateaus are the result of back reactions that limit the overall pressure increase and H{sub 2} production. These results clearly demonstrate that 0.5 wt % H{sub 2}O on NpO{sub 2} is safe for long-term storage--if such a moisture content could even be practically reached.
Date: February 3, 2004
Creator: Icenhour, A.S.
Partner: UNT Libraries Government Documents Department

Design Optimization of Radionuclide Nano-Scale Batteries

Description: Radioisotopes have been used for power sources in heart pacemakers and space applications dating back to the 50's. Two key properties of radioisotope power sources are high energy density and long half-life compared to chemical batteries. The tritium battery used in heart pacemakers exceeds 500 mW-hr, and is being evaluated by the University of Florida for feasibility as a MEMS (MicroElectroMechanical Systems) power source. Conversion of radioisotope sources into electrical power within the constraints of nano-scale dimensions requires cutting-edge technologies and novel approaches. Some advances evolving in the III-V and II-IV semiconductor families have led to a broader consideration of radioisotopes rather free of radiation damage limitations. Their properties can lead to novel battery configurations designed to convert externally located emissions from a highly radioactive environment. This paper presents results for the analytical computational assisted design and modeling of semiconductor prototype nano-scale radioisotope nuclear batteries from MCNP and EGS programs. The analysis evaluated proposed designs and was used to guide the selection of appropriate geometries, material properties, and specific activities to attain power requirements for the MEMS batteries. Plans utilizing high specific activity radioisotopes were assessed in the investigation of designs employing multiple conversion cells and graded junctions with varying band gap properties. Voltage increases sought by serial combination of VOC s are proposed to overcome some of the limitations of a low power density. The power density is directly dependent on the total active areas.
Date: October 6, 2004
Creator: Schoenfeld, D.W.; Tulenko, J.S.; Wang, J. & Smith, B.
Partner: UNT Libraries Government Documents Department