Design of Lithium-Lead/Water interaction experiments relevant to WCLL breeding blanket in-box LOCA

The present thesis work was performed during an internship of six months at ENEA Brasimone Research Center. The objective has been focused on the design of the experiments relevant for the validation of SIMMER-III code, and in particular of the lithium lead water reaction chemical model implemented in the code. Lithium lead alloy is used in Water-Cooled Lithium-Lead Breeding Blanket, which is a candidate for DEMO fusion power plant. The conceptual design of the DEMO is developed under the supervision and coordination of the EUROfusion Consortium Agreement. The water coolant system is characterized by horizontal tubes placed in the liquid Lithium Lead. Notwithstanding these are double walled, the probability of a water tube rupture is not negligible, thus the “in box LOCA” accident is of major relevance. Indeed, this implies the interaction between high temperature (about 300°C) and high pressure (15.5MPa) coolant water and high temperature PbLi (> 330 °C), which will cause release of energy in the breeding zone, due to the thermal and chemical reaction and the hydrogen generation. The review of past R&D activities has highlighted that no code is capable to perform a deterministic analysis of the “in box LOCA” postulated accident. Analogously past experimental activities are not suitable to validate predictive computational tools. In view of this, ENEA has proposed a R&D activity, lasting five years, aimed at setting-up a computer code suitable to simulate the phenomena relevant to safety occurring during the lithium lead water interaction; and at designing and executing the experimental campaign to generate data for code validation in the LIFUS5/Mod3 facility. The activity has been pursued working on the implementation of the experiment and design of as well as on the numerical simulations with SIMMER-III code, making pre-test calculations, to support the design of the test matrix and the testing procedures. At the end of the activity, the conceptual design of test section B has been developed, the hydrogen extraction line and analysis system have been designed by means of SIMMER-III and RELAP5/Mod3.3 codes and the SIMMER-III nodalization of LIFUS5/Mod3 test section was used to make pre-test calculation to determine test conditions for two experimental campaigns: the former campaign is aimed to validate the SIMMER-III chemical interaction model, the latest is focused on validating the global reaction/interaction model