Thermal and structural analysis of JT-60SA actively cooled divertor target submitted to high heat flux

Abstract

JT-60SA is a joint international fusion experiment being built and operated in Japan under the framework of the Broader Approach Agreement and Japanese National Fusion Programme, aiming at an early realization of fusion energy by conducting supportive and complementary work for the ITER project, all towards supporting the basis for DEMO. In this context, a collaboration has been established via EUROfusion between Fusion for Energy and CEA to develop actively cooled targets of the JT-60SA divertor.The first Actively Cooled Divertor (ACD) target, planned to be operated in 2029, has graphite as armour material and TZM as heat sink material. To be DEMO relevant, ACD target with tungsten armour is planned to be operated in 2033, with either CuCrZr or TZM as heat sink material.This paper focusses on the choice of the design (material, dimensions) of these targets. Results of thermal and structural analysis of these targets are presented. The calculations, carried out in the environment of Ansys 2021R2 code, have taken into account the heat loading under plasma operation (with a peak heat flux of 10 MW/m2) and the electromagnetic loads from a representative plasma disruption (VDE 30 ms). In order to check the compliance with nuclear requirements, RCC-MRx 2015 has been used for the mechanical assessment of metallic components, while for the graphite the comparison between the maximum stress and the yield stress has been considered. The performed analyses show that the thermal load on target during the plasma heat loading drives target designs due to differential expansion at the interface between the heat sink and the flat tiles.Additionally, on-going assessments on these divertor targets are presented, focussing on experimental High Heat Flux testing, as well as computational thermal-hydraulic studies on enhanced target configurations.