The main JT-60SA vacuum vessel (VV) is torus-shaped and double-walled. The double-walled cavity is filled during operation with borated water to enhance the neutron shielding capability of the vacuum vessel. The coolant will operate typically up to ~50°C. Every 40 degrees, the vessel is attached at the bottom to a gravity support of sprung plates.

The vacuum vessel can be baked at 200°C by means of heated nitrogen gas after draining the borated water. Plasma operation during VV baking is not planned because the neutron shielding capability would be lost and there would be too high a heat load on the cryogenic system.

The vacuum vessel system also includes the vacuum pumping and the plasma fuelling subsystems.

Manufacture of the vessel began in 2010. Due to the difficult of transporting such large components, the sectors needed to be assembled at the Naka site from an inboard and outboard leg. This required the construction of a building to house the sector assembly. To ease manufacturing and final assembly the vessel is made up of seven 40°, two 30°, and one 20° sector. To minimise distortions and keep as far as possible within tolerances, the sectors have to be welded together in a certain sequence, and alignment of adjacent sectors checked and adjusted before final assembly.