Evaluation of environmental effects on fatigue life of piping

Recent data indicate that the effects of light water reactor environments c an significantly reduce the fatigue resistance of materials, and show that design fatigue curves may not be conservative for reactor coolant environme nts. Using revised fatigue curves developed by Argonne National Laboratory (ANL), the work of this paper calculates the expected probabilities of fati gue failures and associated core damage frequencies at a 40-year and 60-yea r plant life for a sample of components from five PWR and two BWR plants. T hese calculations were made possible by the development of an enhanced vers ion of the pc-PRAISE probabilistic fracture mechanics code that has the abi lity to simulate the initiation of fatigue cracks followed by the linking o f these cracks. Results of interim calculations subject to review are prese nted. Components with the highest probabilities of failure can have predict ed frequencies of through-wall cracks in the order of about 5 x 10(-2) per year. The corresponding maximum contributions to core damage frequencies ar e in the order of 10(-6) per year. Components with the very high failure ra tes show essentially no increase in calculated core damage frequency from 4 0 to 60 years. (C) 2001 Elsevier Science B.V. All rights reserved.