Experimental measurement and theoretical calculation of Ar-41 radioactivity in the primary coolant of HTR-10

Ar-41 is a key activation product in the primary circuit of the high-temperature gas-cooled reactor (HTGR) and a concern for reactor radiation safety, impacting doses for nuclear power plant staff and nearby residents. Currently, the source of Ar-40 in pebble-bed HTGRs is unclear, and systematic research is lacking. In this study, the Ar-41 source term of the 10 MW high-temperature gas-cooled experimental reactor (HTR-10) was determined based on the operating status. The Ar-41 source term calculation model for HTGRs was established with three-types Ar-41 source term: pulse, short-time constant, and constant sources. The accuracy of the calculation model for the Ar-41 source term was confirmed by comparing the theoretical and experimental radioactivities of Ar-41 in the primary circuit, both of which varied in 10⁷–10⁸ Bq during normal operation and exhibited consistent trends. Finally, we proposed reducing radioactivity in the primary circuit by controlling the entry of Ar-40 or increasing the HPS's flow rate while maintaining purification efficiency. Current research fills a gap in the Ar-41 source term study in the primary circuit and systematically constructs a framework and methodology for calculating the Ar-41 source term in HTGRs, which provides strong support for the safe operation of HTGRs.