Validation of SIMMER-Ⅲ code for in-box LOCA of WCLL BB: Pre-test numerical analysis of Test D1.1 in LIFUS5/Mod3 facility

摘要

One of the four breeding blanket concepts for European DEMO nuclear fusion reactor is the Water-Cooled Lithium Lead Breeding Blanket (WCLL BB). The WCLL in-box LOCA (Loss Of Coolant Accident) is a major safety concern of this component, therefore transient behavior shall be investigated to support the design, to evaluate the consequences and to adopt mitigating countermeasures. To fulfill this objective, at first, SIMMER-III code was improved by implementing the chemical reaction model between PbLi and water. Then, SIMMER-III Verification and Validation (V&V) procedures have been established and conducted to obtain a qualified code for deterministic safety analysis. The verification activity was successfully completed, while the validation activity requires further effort according to the R&D plan set up in the framework of the EUROfusion Project. In view of this, an experimental campaign and a test matrix has been designed in LIFUS5/Mod3 facility performing pre-test analyses of Test D1.1.The preliminarily-defined test matrix will be used for the validation SIMMER-III according to a standard procedure. At the present stage, a pre-test numerical analysis was performed to support future experimental tests. The presented work aims to support the upcoming experimental activity in terms of setting up Boundary & Initial condition, specifying the most important parameters to be measured during tests and calculated by SIMMER-III code during transient and obtaining the best nodalization for the post-testing simulation. In particular, a qualitative analysis of obtained results was performed according to the available data time trends and based on engineering considerations. It aims to interpret the resulting sequence of main events and the identification of phenomenological windows and aspects, relevant to pressure transient and hydrogen production due to the chemical reaction between heavy liquid metal and water.