Safety Aspects of Thorium Fuel in Sodium-Cooled Fast Reactors

Conclusions: ● Thorium fuel significantly reduces void positive reactivity insertion − ~2$ reduction for the ARR burner design (oxide fuel); − ~6$ reduction for the ARR breakeven design (nitride Th vs. U metal). ● ~ 1m$/K more negative Doppler for the Th breakeven design. ● Effects on transients need to be assessed (underway). ● Larger blankets, higher fuel manufacturing/reprocessing and larger reactivity swing in Th-breakeven. ● Comparable long-term capability to withstand double-fault accidents. → Thorium can be appealing for TRU burning and/or decreasing void reactivity keeping a simple design (e.g. axially homogeneous). ● Very high sources requiring remote fuel manufacturing for all cases (U and Th). ● Long term options with substantial developments/additional costs when full actinide recycle is pursued in U and for all cases in Th