Tritium release scenarios in the IRPR system of DEMO: Safety assessment and mitigation strategies

This study investigates potential tritium release scenarios in the Isotope Rebalancing and Protium Removal (IRPR) system of DEMO fuel cycle, focusing on failures in the Temperature Swing Absorption (TSA) unit, including its feed tank. Two accident cases are considered, based on the postulated initiating events identified by the FFMEA: (1) a guillotine break in the pipeline supplying the IRPR system and (2) a pipe rupture in the TSA unit. MELCOR 1.8.6 for fusion is used to simulate the dynamics of the gases (hydrogen, air, inert gases), the resulting pressurization of the enclosure volumes, and the accumulation of hydrogen isotopes. A parametric study evaluates the impact of design choices like feed tank configuration and glovebox volume, informing the design of the system to enhance safety. The analysis includes cases where safety systems such as detritiation or isolation fail to operate correctly. The findings support ongoing safety assessments for DEMO and inform strategies to improve safety in fusion power plants. • Failures in DEMO IRPR system based on TSA technology are modeled with MELCOR to assess tritium releases. • Multiple cases are analyzed to optimize preventive and mitigation measures. • Increasing the glovebox size can prevent hydrogen concentration to reach the flammability limit even in worst-case scenarios (no inert atmosphere). • The nominal detritiation flow rate (0.1 vol/h) is sufficient to capture nearly all the tritium released during the worst failures. • Hydrogen stratification in the building does not lead to hydrogen bubbles with concentration above the flammability limit.