The Influence of Water Chemistry on Fatigue Crack Propagation in LWR Pressure Vessel Steels

摘要

The results of an experimental programme designed to obtain corrosion fatigue crack growth data for pressure vessel steels are described. The work has concentrated on assessing the influence of various water chemistry variables possible in PWR or BWR primary coolants on fatigue crack propagation rates in A533-B steel. At a low cyclic frequency, 0.0167 Hz, the only variable found to have a significant effect on crack growth rates when compared with an inert helium environment at the same temperature, 288 C, is the dissolved oxygen concentration at levels in excess of 100 ppb. However, the effect of the oxygenated water on crack growth is observed to decay rapidly with time of exposure and this is attributed to passivation of surfaces previously created in a short period of time by high frequency cycling. At higher cyclic frequencies of 1.0 Hz or greater, periods of constant crack growth rate independent of the applied cyclic stress intensity factor have been observed in all the aqueous environments examined.