Design, Numerical, and Experimental Studies for In-Box LOCA Scenario in the Integral Test Facility Supporting the WCLL-TBS

A critical safety concern with the WCLL configuration involves the potential interaction between PbLi (Lithium-Lead) and water, which may occur in the event of a tube rupture within the breeding zone, specifically referred to as an in-box Loss of Coolant Accident (LOCA) scenario. In this framework, the ENEA Brasimone Research Centre collects essential data on the chemical interaction between PbLi and water under WCLL blanket breeding accident conditions by building and operating the LIFUS5/Mod3 SET facility. SIMMER-III and -IV codes have been chosen to develop predictive tools for the simulation of all tests of the LIFUS5/Mod3 series E experimental campaign. Experimental activities conducted with the LIFUS5/Mod3 facility have significantly contributed to validating the SIMMER code, both in terms of chemical models and thermal-hydraulic performance. However, simulating the entire facility solely with the SIMMER codes is impractical due to the complex geometries involved, which include long pipelines of the injection line. Therefore, SIMMER is coupled with the RELAP5/Mod 3.3 STH code. The primary objective of this endeavor is to construct a facility, the LIFUS5/Mod4, which replicates the WCLL BB elementary cell, and to conduct experimental activities involving PbLi-water reactions, simulating the WCLL BB in-box LOCA. LIFUS5/Mod4 together with the Water Loop (WL) will be part of the Water thermal-HYDRAulic (W-HYDRA) experimental platform, which is being built at the ENEA Brasimone Research Centre. The coupling scheme developed for the simulation of LIFUS5/Mod3 is then adopted for the full-scale facility reproducing the geometries of the WL and LIFUS5/Mod4 facilities. The computational domain is divided into three regions. WL and LIFUS5/Mod4 are each represented as separate nodalized domains in RELAP5/Mod3.3, and are interconnected via four MATLAB interfaces, representing inlet and outlet connections for both loops, within a detailed model of the Test Section in the SIMMER-IV domain. The primary objective of this study is to evaluate the impact of system compressibility on pressure wave propagation originating within the SIMMER-IV domain and transmitted to the two connected loops. These insights are essential for developing an effective control logic aimed at mitigating the consequences of the accident scenario.