The Role of Plutonium-238 in Nuclear Fuel Cycles

The use of a ²³⁸Pu “heat spike” has been proposed to render reactor-grade plutonium unattractive as a weapons material The technical feasibility of nuclear fuel cycles with plutonium containing 5 to 8% ²³⁸Pu was studied by investigating the production of ²³⁸Pu and its precursors (²³⁶U, ²³⁷Np, ²⁴¹Am, and ²⁴²Cm) in light water reactors (LWRs) and in liquid-metal fast breeder reactors (LMFBRs). The effects of ²³⁸Pu and its precursors on reactor core behavior and fuel cycle operations were also analyzed. Modified LWR fuel management schemes allow the ²³⁸Pu content to build up to 5% in three reactor-fuel cycles and sufficient excess neptunium is generated for the concept to be expanded to all reactors in the fuel cycle in a timely manner. The production of ²³⁸Pu in LMFBRs is not self-sufficient. Tandem LWR-LMFBR fuel cycles (four LWRs to one LMFBR) are required to maintain a sufficient ²³⁸Pu level and a neptunium balance. The concept required small, but significant, increases in the initial fissile content of LWR fuel. Other LWR and all LMFBR core physics and reactivity parameters were not adversely affected. Required modifications to fuel cycle industries are within the present state of technology. An economic evaluation showed heat-spiked fuel cycles to be more costly than normal recycle fuel cycles (∼10 to 15% for LWRs and ∼30% for LMFBRs), but to be 10 to 15% less expensive than the LWR throwaway fuel cycle. In summary, the heat spike concept was found to be technically and economically feasible, but its adoption for LMFBRs might retard breeder introduction and growth schedules.