• LBE
• LIFUS5
• interaction
• SIMMER
• RELAP

The present thesis work has been carried out during an internship at ENEA Brasimone Research Centre (Italy). The technical activity was conducted in the framework of LEADER project (European Lead-cooled advanced Demonstration Reactor), launched from EURATOM under the 7th Framework Programme. This work contributes to the research and development activities focused on safety of Gen. IV reactors employing as primary coolant Heavy Liquid Metal (HLM). For these reactors a pool-type configuration in which the steam generators are inside the reactor vessel is provided. Therefore, the interaction between the secondary side coolant (water) and the HLM (e.g. steam generator tube rupture) has to be considered as challenging safety issue in the design and also in the preliminary safety analysis of these reactor types. In this framework, the experimental separate effect facility LIFUS5/Mod2, installed at ENEA Research Center, was modified (i.e. top flange, test section and, partially the instrumentation and control system), installing a new test section having a geometry representatives of the tube bundle of ELSY steam generator. Tests were executed to study the interaction between LBE and water, with boundary and initial conditions relevant for the first seconds of the SGTR accident, as well as to demonstrate the reliability of computer codes in simulating the phenomena of interest.
The activity can be divided into two main parts: one experimental and the second based on code application. The former has been employed for supporting the preparation of LIFUS5/Mod2 facility, the assembling of LEADER test section, the documentation of the facility configuration and instrumentation, the execution of the preparatory (i.e. protective cap pressure tests) and commissioning (i.e. tests procedures and acquisition system) tests. The experimental work was completed with the design, execution, analysis and documentation of two tests, B1.1 and B1.2. These experiments provided pressure, temperature and strain trends versus time at an acquisition frequency up to 10 kHz, suitable for the analysis of interaction phenomena and the code validation. The pressure trends have been highlighted a remarkable damping of pressure wave propagation generated. This is caused by the impact with the tube bundle (that was not damaged) and also by the forced passage through the lateral surface of the test section. This observation is also supported by the strain gage signal trends.
The second part of the activity has been focussed on the use of codes for supporting the experimental campaign, the design of experiments and for the experimental data analysis. RELAP5/MOD3.3 has been used to perform the analysis of the facility water injection line and to simulate the conditions reached by water before the interaction phase for test B1.1. This was aimed at improving the understanding of the experiments as well as to improve the SIMMER-III code post-test activity. Indeed, the new configuration of LIFUS5/Mod2 facility was modelled by SIMMER-III code. The simulation of the first test (B1.1) was carried out. The post-test was mainly based on the comparisons of the experimental and calculated pressure trends. The analysis has shown results excellent simulation of the first pressure peak resulting from the rupture of the injector. Instead, the increase in pressure due to the evaporation of water injected was slightly overestimated by the code, due to geometrical approximations of SIMMER-III model.