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A management of irradiation-assisted stress corrosion cracking (IASCC) of intemal components of a nuclear power plants is considered critical for long-term operation of these reactors.Some cracking of the internals in European plants was identified initially in 1985.The cracking mechanism is not fully understood.Among the unrevealed mechanisms, the effect of the dissolved hydrogen (DH) concentration on IASCC propagation has not been studied much.The studies are more limited on the effect of DH concentration on the IASCC initiation process.Stephenson observed a high crack initiation density in a primary water (PW) environment as compared to normal water chemistry (NWC), indicating that the low electrochemical potential in hydrogenated water chemistry (HWC) or PWR primary water suppresses crack growth, possibly facilitating crack initiation.Because such studies are rare, it remains uncertain if a high DH level suppresses crack growth but enhances crack initiation.