Recommended in-vessel tubing failure rates for the international thermonuclear experimental reactor

Several materials have been suggested for fabrication of ITER in-vessel coolant tubing: beryllium, copper, Inconel, niobium, stainless steel, titanium, vanadium, and zirconium. This paper is a synopsis of an INEL study which generated failure rates for the suggested materials based on their individual performances with expectant coolants and operation in ITER. Coolants considered were water, helium, and liquid sodium, and lithium. The study defines tubing failure mechanisms anticipated for fusion machines: intergranular attack, flow erosion, helium induced swelling, hydrogen damage, neutron irradiation embrittlement, magnetic field interactions, cyclic fatigue and thermal cycling. The fusion tubing failure rates were generated by applying fusion K-factors to industrial operating experience failure rates for the materials. The results of the failure rates analyses and generation identified titanium, in combination with all of the coolants, as the leading candidate tubing material for operational safety and plant availability.