Plutonium conversion

At any stage of nuclear material management (closure of plutonium facilities, vitrification processes, fabrication of MOX fuel, metallic plutonium conversion into oxide, etc.), the long-lived radionuclides appearing in case of any deviation from the standard process can be reliably isolated from the environment only by their final disposal in geologic formations. 

J. H. Devan, J. R. Distefano, W. P. Eartherly, J. R. Reiser, and R. L. Klueh, Materials Considerations for Molten Salt Accelerator-Based Plutonium Conversion Systems, published in the Proc. International Conference on Accelerator-Driven Transmutation Technologies and Applications, Las Vegas, NV. July 1994, AlP Conference Proceedings 346, LA-UR-95-1792, Woodbury, New York (1995). 

The Plutonium Conversion Development Facility (PCDF) (conversion capacity 10 kg MOX/d), designed for demonstration of the co-conversion technology by MH method, was completed in February 1983. By the end of March 1994, it produced about... 

Note that the initial reactivity difference from pitch 26 cm to pitch 24 cm for an enrichment of 3 g/kg is 16.6 mk if that difference was due to poisoning, the decrease of average bum-up would be about 1700 MWd/t. Actually, it is only half of this value this is because the reactivity loss is due mainly to the factor p, and there is therefore an improvement in plutonium conversion. In other words, a fairly high bum-up leads to a smaller penalty of undermoderation. 

H. De Van, et al.. Materials considerations for molten salt accelerator based plutonium conversion system, in Proceedings of the Global 93 International Conference. Las Vegas,... 

This untimely polymer formation is understood to be caused by the very rapid hydrolysis and aggregation of monomeric Pu(IV) species (at the region of condensate reentry into the hot plutonium solution) to produce hydrous polymers that are not readily depolymerized. At high temperatures such as found under reflux conditions, the polymer rapidly ages through the conversion of hydroxyl- to oxo-bridges ... 

The complete chemistry of plutonium 1 iquid-to-solid conversion processes, especially peroxide and oxalate precipitation, should be further studied. Research and development of direct thermal denitration methods should also be pursued. 

Standifer, R. L. "Conversion of Plutonium Oxide to Plutonium Tetrafluoride with Fluorine in a Fluid Bed Reactor -Part I, Development Studies," U.S. AEC Rept. RFP-1889, Dow Chemical Company, Golden, Colorado, August 23, 1972. 

The following pages will describe several examples of pyrochemical processing as applied to the recycle of plutonium, and will briefly review the fundamental chemistry of these processes. We shall review the conversion of plutonium oxide to plutonium metal by the direct oxide reduction process (DOR),the removal of americium from metallic plutonium by molten salt extraction (MSE), and the purification of metallic... 

A. Process Schematic. A schematic of the main process sequence for the conversion of plutonia scrap to high-purity metal is shown in Figure 2. Plutonia scrap is fed to both the direct oxide reduction (DOR) process and the plutonium tetrafluoride production/ reduction process. 

Another example of the use of carbon tetrachloride for chlorination is the conversion of plutonium dioxide to plutonium trichloride according to the reactions... 

The conversion of plutonium dioxide to plutonium trichloride has often been carried out by using phosgene (COCl2) instead of carbon tetrachloride or carbon and chlorine ... 

Aloy, A. S., Kovarskaya, E. N., Koltsova, T. I., Samoylov, S. E Rovny, S. I. Medvedev, G. M. 2002. Immobilization of Am-241 formed under plutonium metal conversion into monazite-type ceramic. In Lardine, L. J. Borisov, G. B. (eds) Review of Excess Weapons Plutonium Disposition. LLNL Contract Work in Russia, UCRL-ID-149341, 141-145. 

FUEL. In the conventional sense, a fuel is a material or combination of materials which, when burned with air, produces heal. This heat, in turn, can he used in numerous ways—as in the conversion of water lo steam. The steam, in turn, can be used in many ways—as in a steam turbine to produce electricity, Fuels also are burned to oblain explosive or mechanical energy—as in an internal combustion engine where heal per se is an inevitable, bul undesired byproduct. The term fuel is also used in connection with nuclear reactions—as the material, such as uranium and plutonium isotopes, which undergoes fission and. in so doing, yields heat energy, Fuel also appears in the term fuel cell, in which chemical reactions other than what may be considered as conventional combustion are carried out 10 yield electrical energy. 

Step 13. Add 5 mL of concentrated HN03 to the 100 mL beaker, swirl to mix, and gently heat on the hot plate to evaporate to a small liquid residue to remove the iodine. Complete the conversion of the plutonium to the nitrate form by two additional treatments with 5 mL portions of concentrated HN03. Evaporate to near dryness each time, but do not dry. 

Figure 2. Integrated flowsheet used at the ALKEM plant for plutonium nitrate conversion combined with 241 Am separation and conversion...

Gray, L. W., "Rapid Dissolution of Plutonium Metal in Sulfamic Acid Followed by Conversion to a Nitric Acid Medium," accepted for publication in Nucl. Technol., MS. 

Plutonium is subsequently stripped to an aqueous phase containing NH20H HN03 in the CC Column. In order to increase the plutonium concentration of the CC Column product, a portion of this stream (CAIS) is recycled to the CA Column after adjustment with HNO3. The remainder of the stream (CCP) is routed to the product concentrator. The resulting concentrated and purified plutonium nitrate solution is suitable feed to other processes for conversion to the desired product form (e.g., metal or plutonium dioxide). The remainder of the PRF solvent extraction system consists of a series of columns to wash the TBP-CCI4 solvent and prepare it for reuse. 

Plutonium-239. Plutonium-239 represents a fortuitous phenomenon. Whereas U-235 is the only significant fissile nuclide in nature, its major isotope, U-238, captures a neutron to produce another fissile nuclide, plutonium-239. A substantial amount of the energy produced during the life of uranium fuel is produced by the conversion of U-238 to Pu-239 which subsequently fissions. This process provides the basis for the nuclear breeding cycle. 

Plutonium-239 and tritium for use as military explosives are the two major transmutation products. The nuclear process for Pu-239 production is the same as for energy generation, but there are some differences (a) metallic natural uranium clad with aluminum facilitates later dissolution for plutonium recovery, and the reactor operates at a relatively low temperature because of the aluminum clad and better heat transfer (due to the metallic natural uranium) (b) the irradiation cycle is limited to a few months to minimize the Pu-239 conversion to Pu-240 and Pu-241 and (c) a carbon or a heavy water moderator is used to increase the neutron efficiency. 

Two engineering system demonstrations were performed to reduce the uranium-from-ore requirements of LWRs recycle of the plutonium and conversion to the thorium-uranium cycle to achieve thermal breeding. The demonstration phase of the plutonium recycle development was carried out in seven power reactors. Several LWRs originally were started up on the thorium-uranium cycle, and a light... 

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