Effect of irradiation temperature on the fracture-mechanical behaviour of tungsten irradiated to 1 dpa

We investigate the influence of neutron irradiation on the fracture-mechanical behaviour of ITER-specification conform stress relieved tungsten bar. The neutron irradiation of miniaturized Disc-shaped Compact Tension specimens with electrical discharge machined notches was performed in the Material Testing High Flux BR2 reactor of SCK CEN in Mol. Damage doses close to 1 dpa were achieved at multiple irradiation temperatures of 400, 600 and 1000°C. Suppression of thermal neutrons fluence by applying stainless steel capsules resulted in reduction of Re (Os) content down to fusion application relevant level of 2 at% (0.2 at%). Neutron irradiation strongly impacted fracture-mechanical behaviour of the material. Depending on the irradiation temperature, the DBTT increases by about 650°C or even higher as has been deduced on the basis of the load-displacement curve analysis. The degradation of the mechanical properties is attributed to the alteration of the microstructure and fracture mode. The results are compared with the fracture-mechanical data on irradiated tungsten obtained previously in the course of same neutron irradiation campaign.