Low enriched uranium

Supply Projections. Additional supphes are expected to be necessary to meet the projected production shortfall. A significant contribution is likely to come from uranium production centers such as Eastern Europe and Asia, which are not included in the capabihty projections (27). The remaining shortfall between fresh production and reactor requirements is expected to be filled by several alternative sources, including excess inventory drawdown. These shortfalls could also be met by the utili2ation of low cost resources that could become available as a result of technical developments or pohcy changes, production from either low or higher cost resources not identified in production capabihty projections, recycled material such as spent fuel, and low enriched uranium converted from the high enriched uranium (HEU) found in warheads (28). 

An agreement between the United States and Russia led to a commitment in 1994 by the United States to buy 500 metric tons of Russian HEU, which has been converted to low enriched uranium (LEU). The HEU must come from dismanded nuclear weapons before it is converted to LEU. The sale of converted HEU to the United States is to be carried out on a timetable in which no less than 10 t are to be converted in each of the first five years of the agreement and no less than 30 t in each year thereafter (35). In all, the agreement would last for 20 years if only these minimums were sold each year. 

Democratic Republic of Congo. It contained low-enriched uranium with a U-235 content of 19.9% —just below the 20% threshold defining highly enriched uranium. It is uncertain whether the rod was ever recovered. 

LDH LEU LIBD LAW LET LILW LIP LLNL LLW LMA LMFBR LOI LREE L/S LTA LWR Layered double hydroxide Low enriched uranium Laser-induced breakdown detection Low-activity waste Linear energy transfer Low- and intermediate-level nuclear waste Lead-iron phosphate Lawrence Livermore National Laboratory Low-level nuclear waste Law of mass action Liquid-metal-cooled fast-breeder reactor Loss on ignition Light rare earth elements (La-Sm) Liquid-to-solid ratio (leachates) Low-temperature ashing Light water reactor... 

Indirect-use material Low-enriched uranium 75 kg uranium-235 12 months... 

Japan s nuclear source materials and nuclear fuel materials, which support this nuclear power generation, are all subject to safeguards under the Nuclear Regulation Law and the NPT. At the end of 1992, Japan held roughly 35001 of natural and depleted uranium, about 94001 of low enriched uranium (LEU) and 33.5 t of plutonium. Figure... 

Table 12.5 shows expected isotopic uranium contents which might be expected as product from cascade type (gaseous diffusion or gas centrifuge) enrichment facilities. While the highly enriched U is actually the target of these efforts one should also be able to verify the production of low enriched uranium. Columns 5 and 6 of Table 12.5 show the isotopic enrichments which would result from a 1000-1 mixture of namral U and low or high enriched U. Table 12.6 shows the ratios of the isotopes U and U relative to the in each mixture. The 0.6% isotopic shift in the ratio in the case of LEU-MIX should be detectable by today s technology. The 0.13% in ratio... 

A low-enriched uranium reactor fuel containing 6.8% B5U (approximately 10 times as much as natural uranium). It has sufficient neutron density to yield plutonium. 

Relative capacity for processing low-enrichment uranium fuels, per unit of equipment Relative capacity for processing enriched fuels in critically safe design Amount of shielding per unit capacity Flexibility Reliability in plant service... 

Pu. The isotope Pu results from neutron capture in followed by two beta decays. It is the principal isotopic constituent of plutonium formed by the irradiation of low-enrichment uranium. It is the principal flssile corrstituent in plutonium fuel used in thermal and fast reactors. Pu alpha decays, with a half-life of 24,400 years, to form the U parent of the An+3 decay series discussed in Chap. 5. Relatively pure Pu can be made by the short-term low-exposure inadiation of natural uranium. Plutonium containing more than 99 percent Pu results from the irradiation of uranium at fuel exposures of less than 0.7 MWd/kg [K2]. Because of the hi ... 

In the Aquafluor process [G4] developed by the General Electric Company, most of the plutonium and fission products in irradiated light-water reactor (LWR) fuel are separated from uranium by aqueous solvent extraction and anion exchange. Final uranium separation and purification is by conversion of impure uranyl nitrate to UFg, followed by removal of small amounts of PuF , NpFg, and other volatile fluorides by adsorption on beds of NaF and Mgp2 and a final fractional distillation. A plant to process 1 MT/day of irradiated low-enriched uranium fuel was built at Morris, Illinois, but was never used for irradiated fuel because of inability to maintain on-stream, continuous operation even in runs on unirradiated fuel. The difficulties at the Morris plant are considered more the fault of design details than inherent in the process. They are attributed to the attempt to carry out aqueous primary decontamination, denitration, fluorination, and distillation of intensely radioactive materials in a close-coupled, continuous process, without adequate surge capacity between the different steps and without sufficient spare, readily maintainable equipment [G5, R8]. 

The Idaho Chemical Processing Plant is a versatile, multipurpose facility used for recovering highly enriched uranium from a variety of fuels in naval propulsion, research, and test reactors. Materials processed [Al] include aluminum-alloyed, zirconium-alloyed, stainless steel-based, and graphite-based fuels. The West Valley plant, although designed primarily for low-enriched uranium fuel from power reactors, also processed plutonium-enriched and thorium-based fuels. It is the only U.S. plant to have reprocessed fuel from commercial nuclear power plants. 

Ensuring that the mass is always below the critical level by limiting the quantity present this may be as small as a few tens of kilograms for low enriched uranium. Such a system has the disadvantage of requiring an elaborate system of managerial control combined with a system of mechanical interlocks to ensure that specified quantities never are exceeded. 

The first set of experiments, started in 1959, included simple sub-assemblies with uranium solutions in spheres, cylinders, and parallelepipeds. After that, models of real installations were studied. Then there were experiments with subassemblies with regular cylinders filled with uranium dioxide of high enrichment, with inserts filled with low-enriched uranium with H/U=7.8 with solution devices in the form of a parallelepiped which interacted, for example, through brick, water, and polyethylene and with solutions poisoned with gadolinium. 

Bulanenko, V.I., Frolov, V.V., Charychansky, V.V. (1984), Neutron Control of Low-enriched Uranium Dioxide Humidity, Atomnaya Energiya 155-157. 

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