Design update and thermal-hydraulics of LLCB TBM first wall

Abstract

The First Wall (FW) of Indian Lead Lithium Ceramic Breeder (LLCB) Test Blanket Module (TBM) is a U-shaped structure made of India specific Reduced Activation Ferritic Martensitic Steel (IN-RAFMS). As the FW is directly exposed to high heat flux from plasma, it is actively cooled by high pressure and high temperature helium gas. Following the Conceptual Design Review (CDR) at ITER, some improvement on the design of LLCB TBM has been envisaged, this includes the FW design to reduce the operational load on helium cooling process systems. The optimization studies have been carried out selecting suitable channel size, shape and no. of flow circuits of FW to keep the FW temperature and pressure drop within the acceptable limits. The parametric study has been performed with different mass flow rates and channel configurations of FW. This analysis resulted in the reduction of mass flow requirement by about 38% of the current value. The optimized parameters have been used to carry out the thermal-hydraulic and thermo-mechanical analyses of the two selected configurations of FW using ANSYS code. The temperatures and stresses are found to be within the required limits. Finally, the detailed thermal-hydraulics of final selected design of TBM FW have been performed using ANSYS CFX to estimate temperature distribution along with the validation of analytically calculated pressure drop and Heat Transfer Coefficient (HTC). It is observed that the temperature distribution on FW obtained from the flow analysis in CFX and that obtained by performing thermal analysis in ANSYS using HTC from engineering correlations are similar. The detailed analysis of the variation of HTC along the flow length of the heat flux zone has also been discussed. This paper also discusses transient and accident thermal analysis of the updated design for some of the ITER scenarios and the temperatures have been found to be within the required limits.