Chapter 2. Fuel Choice for Actinide Transmutation in LWRs An LWR fuel cycle aiming at the reduction of waste burden must take advantage of innovative fuel materials capable of producing less TRU than currently employed UO2 fuel. Pu and MA are products of the neutron capture reactions in uranium. Naturally, to facilitate the objective of improving the long term characteristics of the nuclear waste, the amount of uranium present in the fuel has to be minimized. However, in addition to reduced TRU generation, the innovative fuel materials have to fulfill several other requirements. -
Be able to provide high burnup. Thus, new fuel materials should have better or comparable to UO2 performance under irradiation.
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The properties of new fuel materials should be such that the fuel design will have adequate heat removal capabilities in order to maintain or improve the thermal margin of the existing LWRs operating at their nominal power and during accident conditions.
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If recycling of the TRU is considered, the fuel matrix should be relatively easy to handle in order to reduce reprocessing costs. On the other hand, if the once-through TRU burning strategy is employed, the fuel matrix should provide good capabilities for fission product and actinide retention for a very long term.
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Innovative fuel materials must be chemically compatible with light water coolant and the cladding and have acceptable performance under irradiation with respect to the release of fission gas, swelling, and degradation of their thermal and mechanical properties. In light of these considerations, we examine two base fuel matrix materials: thorium dioxide
(ThO2 – thoria) and neutronicaly inert fertile free matrices. Capabilities of both fuel options with respect to TRU destruction efficiencies and rates were evaluated along with some feasibility assessment of practical designs. Finally, both fuel matrix material options are compared to each other and to the conventional way of burning TRUs which is based on the existing uraniumplutonium mixed oxide (MOX) technology.
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