Assessing fuel cycle design options for advanced microreactors

Microreactor (MR) technology has recently gained traction due to the reduced construction cost of MRs as compared to traditional large reactors. Their small physical geometry causes increased neutron leakage and deteriorated neutron economy, limiting the achievable burnup for MR fuel. The refueling strategy currently being discussed within the MR design community is battery-like refueling, which involves replacing the entire reactor core at the end of its operational cycle. This paper investigates partial core refueling as a means to increase MR fuel burnup and thereby improve fuel cycle economy. Two fuel cycle design strategies have been successfully demonstrated: (1) partial core refueling and (2) partial core refueling combined with assembly rotation. Both strategies were modeled based on a heatpipe-cooled MR, referred to herein as the reference core, for 72 Effective Full Power Months (EFPMs). Partial core refueling was shown to reduce the refueling requirements by 18.0% compared to the battery-like refueling strategy. This corresponds to a 10.5% reduction in the Net Present Value (NPV) of fuel cost over the 72 EFPMs of operation. On the other hand, partial core refueling combined with rotation reduced the refueling requirements by 23.6% (corresponding to a 12.6% reduction in the NPV of fuel cost) in comparison to the battery-like refueling strategy.