Investigation of accident cases for high pressure, high temperature experimental helium loop using RELAP5-3D code

Accident cases are investigated for the Helium Loop Karlsruhe (HELOKA) facility, a high pressure and high temperature experimental helium loop having the European Helium Cooled Pebble Beds (HCPB) Test Blanket Module (TBM) as test module. Two typical operation modes for the loop operation have been numerically modeled using RELAP5-3D code: a pulsed operation (ITER-like situation) and a steady state operation (very long pulse). In both situations a maximum heat load on the first wall of 500 kW/m2 has been considered. Using the generated RELAP-model for these two operating modes three accident cases are studied: failure of helium pressure control system (PCS), loss of helium flow and loss of cooling water flow. Simulation results show that the most critical case is the loss of helium flow. In this case failure of the TBM box is possible. By the loss of cooling water the integrity of the TBM box could be assured, if actions are taken in time. By the failure of the PCS the integrity of pressure barriers are not affected.