Study of a BWR core fuel design concept optimized for plutonium utilization during the transition to fast reactors

Before a fast-reactor-based closed fuel cycle is realized, reducing the inventory of spent fuel from light water reactors through reprocessing and ensuring that recovered plutonium (Pu) does not accumulate as surplus are key priorities. To address these needs, a BWR fuel concept with increased Pu loading was proposed and evaluated. To minimize development requirements, the fuel assembly was based on commercially deployed 10 × 10 lattice fuel. A water-rod-free configuration was adopted to increase the Pu loading per assembly and reduce spent mixed-oxide (MOX) fuel generation by increasing the assembly-average Pu content. The partial-length rod arrangement was optimized to improve reactivity characteristics while maintaining a fuel-assembly pressure drop comparable to that of current BWR fuel. For a full-MOX core design using Pu recovered from spent UO2 fuel after 30 years of cooling, the analysis predicted a discharge burnup of 45 GWd/t, a 24-month cycle length, and an annual Pu loading of 3.3 t-Pu/year. The resulting spent MOX fuel maintains a TRU-equivalent fissile fraction of 0.44 for about 100 years, which is considered favorable for future reuse in fast reactors. Combined with the higher assembly-average Pu content, this characteristic is expected to reduce the reprocessing throughput required for fast-reactor deployment.