Plutonium enrichment

Zinc Distillation Process ( 3, 4 ). A zinc distillation process was selected as a reference pyrochemical process that would have a sufficient degree of proliferation resistance that it could be used by nonweapons nations to reprocess spent fuel without significantly increasing their weapons production capability. The process has the inherent proliferation-resistant advantages of being a low decontamination process with limited plutonium enrichment in uranium-plutonium-zinc mixtures. The process chemistry flow sheet for this process is shown in Figure 1. 

The plutonium/uranium ratio may be adjusted to the desired plutonium enrichment by the addition of the appropriate amount of uranium. 

Plutonium enrichment in mixed oxide product must be sufficient for recycle to the reactor. 

Although these studies are not complete, it appears that molten alkali metal nitrates will react with mixed uranium-plutonium dioxide material of varying composition. Higher melt temperatures and longer reaction times are required, however, as the plutonium enrichment is increased. The insolubility of plutonium dioxide must certainly be investigated further since its solubility in the molten phase upon addition of nitric acid vapor has been claimed in various patents (8, 10). It should... 

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. 

Plutonium enrichment (inner core / outer core)... 

In first case the introduction, of minor actinides doesn t influence on core physical parameters and efficiency of its burning is 30 kg/TW hour. When we use the core with increased plutonium enrichment the efficiency can be increased up to 32 kg/TW hour. 

The 600 MWe high plutonium enriched, steel reflected NEA-Benchmark was evaluated by several institutions. Multiplicationsfactors, Sodium-Void-Coefficient, Doppler-Coefficient and Bumup-Defect were compared. As the table in figure 1 is showing the agreement on the reactivities is not satisfactory. Much worse however is the comparison on the Sodium-Void-Coefficients. The second table in figure 1 shows that a part of the difference is due to different calculmed leakage effects. 

CriUcaiity calculations have been performed for various hexagonal lattices of rods with a plutonium enrichment of 2 wt% in UOt (natural), isotopic ratios of 8 to 26% at moderator/fuel volume ratios of 1.5 to 9.8. The calculations, utilizing the FORM-TEAM-TEMPEST LASER, and THERMOPILE programs have been compared with data obtained from subcritical experiments at the Battelle Northwest Laboratory. ... 

L. BINDLER, L. LEENDERS and H. VAN DEN BROECK, Experimental and Theoretical Physics Work on Plutonium Enriched LWR Lattices, BLG 440/BN7006-03/ EUR 4034 (June 1970). 

Although the data have been generated in support of the LMFBR program, the experimental results on the 7.89 wt% Pu-enriched fuel will be of use to the li t-water reactor community. The plutonium enrichment range applicable to the LWR fuels is between 3 and 8 wt%, but experimental criticality data on homogeneous mixtures have been unavailable for these low enrichment systems. 

V. O. UOTINEN, J. H. LAUBY, L. C. SCHMID, and W. P. STINSON, Lattices of Plutonium-Enriched Rods in Liglit Water-Part I Experimental Results," AhrcA Jechnol., IS,. 257(1972). 

Water Moderated Triangle Lattices of Plutonium enriched ... 

It contains two kinds of fuel assemblies with different plutonium enrichments, the more highly enriched core fuel assemblies being located on the outside to levelize the output power (Fig. 3.4). The initial bum-up will be 80,000 MWd/t (average for discharged fuel assemblies). 

While oxide fuel is favoured in most countries for breeders it may not be the optimum for burners. If burning of plutonium acquires high priority nitride fuel may be needed. This is compatible with Purex reprocessing but allows much higher plutonium enrichment, and therefore burning rates, than oxide. It would probably require the use of nitrogen enriched in N-15, to avoid the production of C-14 (an unwanted radioactive waste product) by the (n,p) reaction in N-14. This in turn may require a modification of the reprocessing route to avoid loss ofN-15. 

To limit the plutonium enrichment in fresh fuel to the allowable level in Japan, the Clean Burn concept employs Pu02 in an inert YSZ microsphere kernel. It avoids mixing with uranium so that no additional plutonimn is generated during a fuel bumup... 

A homogeneous core is shown in Fig. 5.1(a). The core fuel region is surrounded by axial and radial blanket fuels so that the leaking neutrons from the core fuel region can be captured efficiently by the blanket fuels. The core fuel region consists of a few (two in most cases) types of fuel with different plutonium enrichments. The outer core fuel has higher plutonium enrichment than that of inner core fuel to flatten the radial power distribution. 

Mixed-oxide fuel (MOX Pu02 + UO2) has been used as fuel material for the fuel design of the Super FR. The plutonium nuclide amounts used in this study are shown in Table 7.3 [1]. Fissile plutonium ( Pu and " Pu) occupies about 57.8 wt%. The plutonium enrichment is controlled by adjusting the weight fraction of plutonium oxide and uranium oxide. In general, depleted uranium having content of 0.2% is used for making MOX fuel. 

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