Reactor Physics Parameters of Alternate Fueled Fast Breeder Reactor Core Designs

Nuclear nonproliferation considerations have resulted in renewed interest in the thorium fuel cycle. Reactor physics parameters of a typical 1200-MW(electric) fast breeder reactor design were compared for the cases when ²³³U is substituted for plutonium as a fissile fuel and when ²³²Th is substituted for ²³⁸U as a fertile fuel When the ²³⁸U in the blanket is replaced with ²³²Th, the reactor physics parameters are relatively unchanged. However, replacing ²³⁸U in the core with ²³²Th increases the critical mass by 11 to 15% and decreases the breeding ratio by 0.13 to 0.16. In addition, replacing the plutonium in the core with ²³³U decreases the critical mass by 4 to 6% and decreases the breeding ratio by 0.13 to 0.16. Both of the changes in the core make the sodium void coefficient more negative.