Thermal-hydraulic modeling and analysis of the Water Cooling System for the ITER Test Blanket Module

•A pre-conceptual design of the ITER WCLL-TBM Water Cooling System was developed.•A full model of the WCS loop and TBM set was prepared with RELAP5/Mod3.3 code.•Full plasma power condition was simulated to verify the input.•The system behavior during ITER NOS operating state was studied.•A solution was found to guarantee the WCS stable operation during NOS operating state. The Water Cooled Lithium Lead (WCLL) is one of the selected breeding blanket (BB) concepts to be investigated in the EUROfusion Breeding Blanket Project (WPBB), and it was also recently chosen as one of the mock-up for ITER Test Blanket Module (TBM) program. The program foresees the test of different BB mock-ups, called Test Blanket Modules, with all the related ancillary systems. A pre-conceptual design of the Water Cooling System (WCS) of the ITER WCLL-TBM was developed considering the same cooling function of the EU-DEMO WCLL-BB primary heat transfer system (PHTS), but matching different boundary conditions: a scaled source power and far lower heat sink temperatures. A complete thermal-hydraulic (TH) model of the WCS loop and TBM set was developed using a modified version of RELAP5/Mod3.3 system code to verify component sizing and to investigate the system behavior during steady-state and transient conditions. The full plasma power scenario was simulated and used as an initial condition for transient calculations. ITER Normal Operational State (NOS) was studied to evaluate the system response. Simulation results highlighted the need for an electric heater to keep the WCS system in stable operation. A sensitivity analysis was carried out to optimize the heater duty cycle.