To better understand the irradiation assisted stress corrosion cracking (IASCC) mechanism and to establish strategies for IASCC mitigation it is essential to acquire accurate crack growth data on neutron-irradiated alloys in the relevant environment. In this study a crack growth rate (CGR) test on a neutron-irradiated stainless steel alloy was conducted under constant K condition in BWR NWC BWR HWC and PWR water at 288°C and 320°C. The specimen was an 8 mm round compact tension (RCT) sample of high purity 316L SS containing Hf (HP316L+Hf) irradiated to 9.6 dpa in the BOR-60 fast reactor. The CGR test was conducted under load and environmental control and for a duration of 3000 hours. The CGRs were characterized by the real time recording of DCPD and the measurement of actual crack length on the fracture surface. The key factors affecting CGR such as K electrochemical potential water environment dissolved oxygen and hydrogen and temperature were investigated. In addition the effect of neutron-irradiation on the crack growth was also discussed.