Thermohydraulic analysis of the ITER Vacuum Vessel sectors

France

The Vacuum Vessel (VV) is located inside the magnet system and the cryostat and houses the in-vessel components. A double-walled structure surrounds the plasma with several ports for diagnostics, heating and access for remote handling. Its main function is to provide a high-quality vacuum for the plasma and it is an important confinement barrier for ITER.

The VV consists of nine sectors. The volume between the outer and inner shells of each sector is designed to allow the circulation of cooling water supplied by the VV Primary Heat Transfer System (VV PHTS). A single cooling loop per sector removes the heat deposition due to nuclear heating.

The sectors in the area of the Neutral Beam Injectors (NBIs) are classified as “irregular” because their equatorial ports have been modified to allow the integration of the heating systems.

Between 2015 and 2017, IDOM simulated the thermohydraulic behaviour of 3 of the ITER vacuum vessel sectors (Irregular Sector #2, Irregular Sector #3 and Regular Sector #5).

The aim of these projects was to evaluate the impact of nuclear heating on the VV manufacturing design of the VV sectors using CFD tools; the thermo-hydraulic analyses aim at identifying the water mass flow rate distribution, velocity profiles and stagnant regions, conjugate heat transfer (water-shell), heat transfer coefficients (HTC) and temperature distributions and hot spots in the solid and fluid domains. This was done on the 3 full sectors using a steady-state simulation of a model reaching 200 million cells. In addition, due to the transient nature of the plasma scenarios, it is possible that steady state may not be reached during operation. Therefore, a thermohydraulic transient simulation of one of the sectors was performed to determine the maximum temperatures at the end of the burn time and dwell time and to ensure that the thermohydraulic requirements were met.

Fusion