Application of 3D View Factor method for heat fluxes deposition on ITER Cryostat Thermal Shield

摘要

The role of the ITER Tokamak thermal shield system is to minimize heat loads transferred from the hot tokamak components to the cooled superconducting components. The system consists of two single wall structures fabricated from 304L-(N) stainless steel. Both structures are actively cooled with pipes permanently welded to the structure and filled with pressurized helium gas at 80K. One structure is the Vacuum Vessel Thermal Shield (VVTS), which protects magnet components from Vacuum Vessel (VV) radiation. The second structure is the Cryostat Thermal Shield (CTS), which protects magnet components from in-Cryostat components' radiations such as the Cryostat (at 293K), the VV Ports (at 393K), and the water cooling system (at 350K).In 2012, thermal analyses were performed in order to verify the thermal integrity of the ITER CTS 2010 baseline design. The heat loads to the CTS were estimated according to load specification as a homogeneous distribution based on cryostat temperature at 293K. Following this study, in order to determine a more realistic heat load distribution on the CTS panels, we performed a detailed 3D analysis of the Cryostat-CTS interspace.This paper describes the methodology used, based on view factors combined with Kirchhoffs law, to define the heat flux deposition on the CTS from its surrounding components via radiation. The previous thermo-hydraulic analysis models have been adapted using this method to define the temperature distribution and total power transmitted to the magnets. Despite an increase of 30% of the CTS total power deposition on the superconducting components in comparison to the previous analysis, we found the total heat power deposition onto the superconducting components at 4K to be within the limit of the design requirement (P = 1900W).