Mixed actinide fuel cycles

GT-MHR Mixed Actinide Fuel Cycles 5.5.4.1 Deep-Burn MHR (DB MHR)... 

Grandjean, S., Arab-Chapelet, B., Robinsson, A-C. et al. 2007. Synthesis of mixed actinide compounds by hydrometallurgical co-conversion methods. In Advanced Nuclear Fuel Cycles and Systems. Global 2007, Boise, ID, September 9-13, pp. 98-105. 

The used fiiel elemmts may later be reprocessed to recover the remaining amount of fissile material as well as any fertile material or regarded as waste fertile atoms are those which can be transformed into fissile ones, i.e. " Th and U, which through neutron capture and jS-decays form fissile and Pu, respectively. The chemical reprocessing removes the fission products and actinides other than U and Pu. Some of the removed elements might be valuable enough to be isolated although this is seldom done. The mixed fission products and waste actinides are stored as radioactive waste. The recovered fissile materials may be refabricated (the U may require re-enrichment) into new elements for reuse. This "back-end" of the nuclear fuel cycle is discussed in Chapter 21. 

This fuel cycle s sole fuel source uses reprocessed transmanic waste discharged from LWRs. The fissile plutonium (obtained after a AFCI-UREX or other similar process) becomes the main driver fuel for this cycle. Fortunately, the core neutron spectrum allows for significant neutron capture in the resonance region by several minor actinides mixed in with the plutonium. As a result, this design provides its own negative reactivity control without the need for burnable poisons. Over 96% of the initial Pu-239, including over 60% of the initial actinide nuclides, can be destroyed in this cycle. 

This fuel cycle combined discharged and recycled TRU waste from an LEU or mixed LEU/Thorium (LEU/Th) fuel cycle with the fresh fuel. The mixed-core fuel is composed of 80% fresh fuel and 20% discharged and recycled TRU waste. This is therefore essentially a closed-cycle LEU or LEU/Th fuel cycle. Through recycling-bred fissile and minor actinide nuclides from a cycle discharge, very high actinide destruction is possible, approximately >80%. 

A large size (600—1500 MWei) loop-type reactor with mixed uranium—plutonium oxide fuel and potentially minor actinides, supported by a fuel cycle based upon advanced aqueous processing at a central location serving a number of reactors ... 

Hydroxides. Pure and mixed metal actinide hydroxides have been studied for their potential utility in nuclear fuel processing. At the other end of the nuclear cycle, the hydroxides are important in spent fuel aging and dissolution, and environmental contamination. Tetravalent actinides hydrolyze readily, with Th more resistant and Pu more likely to undergo hydrolysis than and Np. All of these ions hydrolyze in a stepwise marmer to yield monomeric products of formula An(OH) with = 1,2,3 and 4, in addition to a number of polymeric species. The most prevalent and well characterized are the mono- and tetra-hydroxides, An(OH) and An(OH)4. Characterization of isolated bis and tri-hydroxides is frustrated by the propensity of hydroxide to bridge actinide centers to yield polymers. For example, for thorium, other hydroxides include the dimers. 

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