REVIEW OF THERMAL AGING DATA AND ITS APPLICATION TO OPERATING REACTORPRESSURE-VESSELS

The safe and reliable operation of PWR pressure vessels demands a rigo rous understanding of component materials properties throughout servic e life. This paper reviews the current data available for thermal agei ng of both representative pressure vessel steels (plate, weld, heat af fected zone (HAZ)), and simulated HAZ and laboratory produced model al loys. The effects of microstructure and impurity segregation on the em brittling response of a material are discussed and the accuracy of mod elling the segregation of phosphorus, using the thermodynamic and kine tic formulations of McLean, is investigated. The critical areas of the rmal degradation and the uncertainties involved in predicting the effe cts of long term ageing are identified.