THALLIUM: An experimental facility for simulation of HCLL In-box LOCA and validation of RELAP5-3D system code

The experimental facility THALLIUM (Test HAmmer in Lead LithIUM) was designed to reproduce the hydraulic transient in the HCLL TBS (Helium Cooled Lithium Lead Test Blanket System) breeder loop following the rupture of a Cooling or a Stiffening Plate, i.e. In-box LOCA (Loss Of Coolant Accident). In addition, the facility will be used to validate the simulations of the pressure wave propagation with RELAP5-3D system code. THALLIUM reproduces the geometry of the LLE (Lead Lithium Eutectic) loop of the HCLL TBS and it was installed at the ENEA Brasimone Research Centre. In this paper, the facility is presented in detail, emphasizing the similarities and the differences with the reference HCLL TBS design. Particular attention has been paid to the TBM mock-up and to the TBS Storage/Recirculation Tank, which are the components that required the biggest simplifications among the key components of the facility. An analytical study of the pressure wave was carried out, with the aim to highlight a possible source of inaccuracy that might be displayed in the future simulations with the code. The results of the analytical study show that the fluid-structure interactions will decrease the speed of sound in the LLE. Instead, RELAP5-3D does not consider the fluid-structure interactions and, therefore, a difference between the experimental and the simulation data could arise from the different wave speed. Finally, the RELAP5-3D nodalization and the results of a pre-test simulation are presented. These results proved to be useful for the design of the facility