Framework of Nuclear Material Accountancy for Safeguards of Domestic High-Temperature Gas-Cooled Reactor

Background: High-temperature gas-cooled reactors (HTGRs) are being developed as Generation IV systems due to their favorable safety characteristics, high-temperature process heat capacity, and relatively high resistance to nuclear material diversion.Because the domestic blocktype HTGR, under development in the Republic of Korea, uses nuclear energy, an appropriate nuclear material accountancy (NMA) framework is required to support the implementation of International Atomic Energy Agency (IAEA) safeguards and domestic regulations. Materials and Methods:In order to establish a material balance area (MBA)/key measurement point (KMP) configuration along with an NMA strategy for the domestic block-type HTGR, the fuel characteristics and anticipated nuclear material flow were analyzed.A feasible safeguards approach was developed by benchmarking the established safeguards framework for light-water reactors and adapting it to the item-based characteristics of HTGR fuel blocks.Results and Discussion: The entire HTGR facility was conceived as a single MBA comprising four inventory KMPs and three flow KMPs.Operator' s accountancy methods and corresponding IAEA' s verification activities were proposed for each KMP.Fresh fuel accountancy was based on the shipper' s declared values, with IAEA verification through item counting, identification verification, and attribute verification.For in-core fuel, continuity of knowledge was maintained through seals applied to the fuel-handling system and transportation paths.For spent fuel, accountancy was based on code-calculated values, while verification measures were proposed for an underground dry-storage concept.This storage concept requires specialized attribute verification equipment and the incorporation of dedicated verification tubes into the storage design. Conclusion:The proposed safeguards approach indicates that nuclear material in the domestic block-type HTGR can be effectively accounted for and verified within a single MBA.Early application of safeguards by design would support the effective integration of safeguards requirements into HTGR facility development.