SIMPLIFIED ASSESSMENT OF HYDROGEN ACCUMULATION AT STAINLESS-STEEL OVERLAY BOUNDARIES OF HIGH-TEMPERATURE, HIGH-PRESSURE HYDROGEN REACTORS

With regard to the cracking (disbonding) which occurs at the fusion bo undary of austenitic overlays and the base metal of high-temperture, h igh-pressure hydrogen reactors, the accumulation of hydrogen at the fu sion boundaryu subsequent to cooling from a high to a normal temperatu re, which is considered to be the largest causative factor of such cra cking, has been evaluated by numerically solving diffusion equations u sing differential calculus. It has been shown that the amount of accum ulated hydrogen cna be expressed by applying a simple, approximate for mula which incorporates the service pressure of the hydrogen, service temperature, thickness of overlay and base metal, cooling rate, hydrog en solubility, and hydrogen diffusion coefficients.