INSTRUMENTED IMPACT TESTING OF AN IRRADIATED 20MNMONI55 PVS WELD MATERIAL

Instrumented impact tests were carried out on a 20MnMoNi55 pressure vessel steel (PVS) weld material before and after fast neutron irradiation to 2.5 x 10(19) n/cm2 at 160-degrees-C and to 3.5 x 10(19) n/cm2 and 7 x 10(19) n/cm2 at 290-degrees-C. The correlation between the fracture surface appearance and the load-time curve obtained from the tests was investigated. The impact energy was divided into fracture initiation energy and fracture propagation energy. Neutron irradiation decreased the ratio of the initiation energy to the total energy from 15% before irradiation to 10, 9.2, and 6.4% after exposure to 3.5 x 10(19) n/cm2 (T(irr) = 290-degrees-C), 7 x 10(19) n/cm2 (T(irr) = 290-degrees-C) and 2.5 x 10(19) n/cm2 (T(irr) = 160-degrees-C), respectively. The fracture initiation energy was used to establish a correlation with fracture toughness. This correlation can be used to estimate the fracture toughness of the steel after neutron irradiation.