Direct measurement of reactor pressure vessel steels fracture toughness : Master Curve concept and instrumented Charpy-V test

Abstract One of the key issues concerning the structural integrity of reactor pressure vessel is the effect of neutron irradiation on the material fracture toughness. At present, this is achieved indirectly by means of correlation between Charpy and fracture toughness due to neutron irradiation. The uncertainties associated with this indirect determination have increased the need for a direct measurement of the fracture toughness. Taking into account that the surveillance capsules include Charpy-V specimens, recent investigations are focused on the determination of the fracture toughness using this type of geometry. This paper presents two different ways to obtain fracture toughness from Charpy-V specimens: instrumented Charpy-V tests and static fracture toughness tests (three-point bend) applying the “Master Curve” concept. The two methodologies are applied to reactor pressure vessel steels in the unirradiated condition.