Study of thoria-urania fuel during accidents

Abstract

In this investigation, nuclear fuel based on mixed ceramic oxides, using (Th–U)O2 as nuclear fuel and zirconium-based alloy as cladding, was simulated. This strategic configuration can achieve improved safety margins because of an enhanced set of thermal and mechanical properties. The Experimental Breeder Reactor built in the 1950s in Idaho introduced the concept that a reactor can generate more fissile material than it consumes. The thorium fuels have a lower cost and should decrease weapon-grade plutonium compared with conventional fuel, UO2. The nuclear characteristic of thorium-232 or U-238 can make a converter into U-233 or Pu-239. However, using thoria fuels can avoid weapon proliferation by reducing plutonium, and it also should reduce radionuclides such as (Np, Am, Cm). This study uses an optimized composition of Th-75% wt and U-25% wt with an enrichment of 19.5%. We studied the behavior using the fuel licensing codes FRAPCON and FRAPTRAN, including many adaptations for the mixed composition choice. The results prove that thoria–urania fuel has a higher performance than pure uranium dioxide fuel during accidents.