SFR with once-through depleted uranium breed & burn blanket

•Depleted uranium blanket driven by SFR with a wide range of conversion ratio.•The fraction of power generated by the blanket arrived at so far is between 40% and 50%.•The economic is expected to be improved.

This paper assesses the feasibility of Sodium-cooled Fast Reactor (SFR) cores that have TRU recycled seeds and once-through depleted uranium blankets. The design objective of these Seed-and-Blanket (S&B) cores is to maximize the power generated by the blanket. As the blanket fuel cost is significantly lower than the cost of the seed fuel and does not need reprocessing, increasing the fraction of reactor power generated by the blanket will reduce the total fuel cycle cost and the fuel reprocessing capacity required per unit of electricity generated. The S&B core is designed to have a prolate (“cigar”) shape seed (“driver”) to maximize the fraction of neutrons that radially leak into the subcritical blanket and reduce neutron loss via axial leakage. Both seed and blanket contain multiple batches; the blanket batches are gradually shuffled inward, while one third of the fuel batches in the seed are recycled. The preliminary study found that it is possible to design the seed to accommodate a wide range of TRU conversion ratios (CR) without significantly penalizing the burnup reactivity swing. The relatively small burnup reactivity swing enables to design the S&B core to operate at longer cycles and discharge its fuel at a higher burnup relative to conventional TRU transmutation cores with identical CR. The S&B cores can generate 1000 MWth and fit within the S-PRISM reactor vessel. The fraction of core power generated by the blanket is between 40% and 50% without exceeding the radiation damage constraint of 200 Displacements per Atom (DPA); this fraction increases when the seed is designed to have a smaller CR. These features are expected to improve the economics of SFR.