Design and safety aspects of the cryostat confinement barrier

The ITER cryostat is a double-walled vacuum/pressure chamber with flat heads. It is about 36 m diameter and 34 m high, and weighs nearly 3000 metric tons. The ITER tokamak is contained within. It provides vacuum thermal insulation for the superconducting coils. It also provides safety functions preventing radioactivity release to the environment. The spacing between the double walls provides stiffness and also an interspace region so that two leaks in series are needed to penetrate from outside to cryostat vacuum.