Preliminary analysis of an in-box LOCA in the breeding unit of the WCLL TBM for the ITER reactor with SIMMER-IV code

The in-box LOCA (Loss of Coolant Accident) represents a major safety concern to be addressed in the design of the WCLL-BB (Water-Cooled Lead-Lithium Breeding Blanket) that will be tested in the Test Blanket Module of the ITER reactor. In this accident, a tube rupture in the coolant circuit would cause a potential disruptive exothermic chemical reaction between the water (the primary coolant) and the Lead-Lithium. This paper presents the development of numerical tools for the analysis of the in-box LOCA consequences in the breeding unit of the blanket. In this work a simplified computational model of the breeding unit was created by SIMMER-IV which includes the lead lithium and water systems and the internal solid structures. The simulation is set up at the foreseen nominal working conditions of the units and involves a small rupture of the cooling tube, with the consequent propagation of high pressure waves on the breeder side and the fast evolution of the chemical reaction. It is shown here that the code is capable of correctly predicting both these events, from a qualitative point of view, thus providing a highly valuable insight of the whole scenario. These preliminary results will provide a crucial base for further development of this computational tool and the simulation of the whole Test Blanket Module.