Design Study of Small Pb-Bi Cooled Non-Refueling Nuclear Power Reactors (SPINNORs)

Abstract

Small Pb-Bi Cooled Non-refueling Nuclear Power Reactors(SPINNORs) are small lead-bismuth cooled nuclear power reactors with fast neutron spectrum that could be operated for 20 years without on-site refuelling. In this study the results of neutronic design for 62.5-250MWt NPPs are discussed. The reactor cores are designed to have near zero (less then one effective delayed neutron fraction) burn-up reactivity swing during the burn-up period to avoid a possibility of super-prompt critical accident. The basic concept is that the reactor core is adjusted so that its internal conversion ratio is nearly one. During the reactor operation fissile material accumulates in this central region, which helps to compensate fissile material loss in the peripheral core region and also contributes to negative coolant loss reactivity effect. In general higher fuel volume fraction is needed for smaller core.