Vacuum vessel for thermonuclear device

The present invention contributes to an improvement of the reliability of a vacuum vessel for a thermonuclear device having a double-walled structure comprising inner and outer walls. Namely, the inner wall is formed by weld-joining a main plate and a main plate comprising a plurality of clad materials joined with protection plates and connecting between adjacent protection plates by connection liners. The outer wall is connected with the inner wall by way of rib members. A gas discharged groove is formed to a main plate in the vicinity of a position corresponding to the protection plate connected to the connection liner. There are disposed a gas discharge hole passing through the gas discharge grove and a gas discharge pipe connected to the gas discharge hole and being in communication with the outside of a vacuum vessel. A gas discharge means is connected to a gas discharge path comprising the gas discharge groove, a gas discharge hole and a gas discharge pipe for discharge a gas from a space between the connection liners and the protection plates. Then, remained gas can be discharge to the outside of the vacuum vessel from gaps of the connection portion. As a result, rupture of the connection liners due to remained gas can be avoided. (I.S.)