The tubular separate first wall for ITER-EDA

Abstract

Abstract The first wall (FW) is one of the most loaded plasma-facing components; the heat flux is such that the thermal stresses are the most important design concern. In addition, the FW must resist the eddy current induced during plasma disruption and the high pressure of the coolant and should maintain its properties under a fast neutron flux (dose up to 3 MW m−2). The tubular solution is the most suitable to cope with the thermal stresses; the use of a double wall reduces the risk of leaks inside the vacuum vessel by avoiding the growth of cracks through both walls: the soft brazing in between the walls stops the growth of cracks from one tube to the other. The eddy currents induced in the tubes are low and the halo current flowing poloidally in the tubes exerts a radial pressure which is supported by the blanket box via supporting points provided in between the FW and the blanket. The tubes are protected with a coating of beryllium or boron carbide against the radiation heat load during disruption, and with a coating of copper against runaway electrons. Fins attached to the tubes are provided to cope with the change in the toroidal width of the FW along the poloidal direction. The fins are also protected by coatings. The tubes can be made of steel to resist a heat flux of up to 1 MW m−2. For higher heat loads, copper or vanadium can be used. The tubular FW can be replaced independently of the blanket. The thermohydraulic, electromagnetic and dynamic analyses confirm the viability of the solution proposed.