Stress analysis of the KSTAR vacuum vessel under thermal and electromagnetic loads

KSTAR 진공용기 열 및 전자기력 하중에 의한 응력해석

One of the principal components of the KSTAR (Korea Superconducting Tokamak Advanced Research) tokamak structure is the vacuum vessel, which acts as the high vacuum boundary for the plasma and also provides the structural support for internal components. Hyundai Heavy Industries Inc. has performed the engineering design of the vacuum vessel. Here the overall configuration of the KSTAR vacuum vessel was briefly described and then the design methodology and the analysis results were presented. The vacuum vessel consists of double walls, several ports, leaf spring style supports. Double walls are separated by reinforcing ribs and filled with baking/shielding water. The overall external dimensions of the main body are 3.39 m high, 1.11 m inner radius, 2.99 m outer radius, and made of SA240-316LN. The vacuum vessel was designed to be capable of achieving the base pressure of $1\times10^{-8}$ Torr, and also to be structurally capable of sustaining the vacuum pressure, the electromagnetic and thermal loads during plasma disruption and bakeout, respectively. The vacuum vessel will be baked out maximum $150^{\circ}C$ by hot pressurized water through the channels formed between double walls and the reinforcing ribs. A 3-D temperature distribution and the resulting thermal loads in the vessel were calculated during bakeout. It was found that the vacuum vessel and its supports were structurally rigid based on the thermal stress analysis. The maximum electromagnetic loads on the vacuum vessel induced by eddy and halo currents resulting from the engineering plasma radial and vertical disruption scenarios have been estimated. The stress analyses have been performed based on these electromagnetic loads and the resulting stresses at he critical locations of the vacuum vessel were within the allowable stresses.