Strategy of nuclear material accountancy of maritime molten salt reactor for safeguards by design

The Republic of Korea is developing a chloride-salts-based molten salt reactor (MSR) as a carbon-neutral power source for ship propulsion. MSRs are characterized by their mobility, liquid fuel (i.e., bulk handling facility), capability to operate without refueling, and long service life. A new approach to MSR safeguards is required, one that is distinct from that used for conventional light water reactors, which are classified as item counting facilities. This paper proposes a safeguards by design (SBD)-based nuclear material accountancy (NMA) framework designed specifically for maritime MSR. To this end, we analyzed the entire nuclear material flow (from fresh fuel receipt through operation to shutdown) to define the optimal material balance area (MBA) and key measurement point (KMP) configuration. Considering the facilities' conditions, including the simple fuel cycle and limited infrastructure, among others, a single MBA with five KMPs was determined to be the best option. For each KMP, accountancy and verification methods for the facility operator and IAEA, respectively, are additionally proposed. This work presents a preliminary framework to inform and initiate discussions on safeguards implementation under challenging environmental conditions. It aims to support ongoing efforts to ensure the exclusively peaceful use of nuclear material.