Thermal-hydraulic pre-test analysis of the WCLL BB TBM mock-up in view of the experimental campaign to be performed in Water Loop facility

The Breeding Blanket is a key component of a fusion reactor, responsible for shielding structures outside the plasma chamber, closing the fuel cycle by producing tritium, and removing the heat generated by the fusion reaction. Among the designs proposed for the EUropean DEMOnstration fusion power plant (EU-DEMO) aimed at bridging current research and industrial-scale fusion, the Water-Cooled Lithium Lead (WCLL) concept represents one of the main options. This concept will be tested in ITER, the international experimental reactor built to validate technologies under relevant fusion conditions, as a Test Blanket Module (TBM). Within this framework, the W-HYDRA experimental platform is being developed at ENEA Brasimone research center to investigate the WCLL technology in its various aspects. Among the planned tests, a full-scale 1:1 WCLL TBM mock-up will be studied under nominal fusion reactor operating conditions and in accidental scenarios, such as Loss Of Flow Accidents (LOFA). To support these experimental campaigns, pre-test thermal-hydraulic analyses were performed using the system code RELAP5/Mod3.3. This paper focuses on these pre-test simulations for both nominal operation and LOFA scenarios. The analyses aim to assess the facility’s capability to manage transients and to investigate the mock-up response under both standard and off-normal conditions. Sensitivity studies on key design parameters and control system settings were also conducted to evaluate their impact and ensure the integrity of the mock-up during testing.