Fracture Toughness Evaluation With Different Sampling Positions in Butt-Welded HAZ of RPV Steel

Abstract For the structural integrity assessment of reactor pressure vessels (RPVs), the irradiation embrittlement of base metal, weld metal and heat affected zone (HAZ) of RPVs have been monitored in the surveillance program in accordance with Japan Electric Association Code (JEAC) 4201-2007 [2013 addendum]. In general, the mechanical properties in HAZ tend to show the large scatter caused by metallurgical inhomogeneity from the fusion line to the base metal. In this study, the uncertainty in their fracture toughness was clarified from the viewpoint of sampling positions in HAZ. Since the number of tested specimens is important to evaluate the uncertainty in fracture toughness, more than 50 specimens for each sampling position of HAZ were tested. The reference temperatures in all sampling positions of HAZ were lower than that of base metal, the standard position of HAZ (sampling position at 1 mm from the fusion line) showed the highest fracture toughness value among the HAZ. The uncertainty in fracture toughness was larger at sampling position close to fusion line in HAZ sampling position at 0.5 mm and 1 mm from the fusion line).