Radiation resistance of weld joints of type 316 stainless steel containing about 10 appm He

Welding is supposed to be an important method for making joints in the pipes conducting the heat agent when replacing divertor and first wall elements. Embrittlement through helium accumulation within the ITER components repaired by welding during maintenance is one of the factors limiting the materials lifetime. To investigate this problem, a set of the 316 RF type steel specimens was saturated by He up to 50 appm at 80°C. Another part was irradiated in the SM-2 reactor up to 0.1 dpa at 80°C. Afterwards, they were subjected to e-beam welding and arc welding, respectively. A part of each specimen underwent LCF bending; another part was tested to tension. These tensile and LCF tests of the specimens showed that neutron irradiation of the weld joints leads to their embrittlement and rapidly reduces the number of cycles to failure.