Irradiation effects on strength and toughness of three-wire series- arc stainless steel weld overlay cladding

Abstract

The potential for stainless steel cladding to improve the fracture behavior of an operating nuclear reactor pressure vessel, particularly during certain overcooling transients, may depend greatly on the properties of the irradiated cladding. Therefore, three-wire stainless steel cladding irradiated at temperatures and to fluences relevant to power reactor operation was examined. Postirradiation tensile testing results show that, in the test temperature range from {minus}125 to 288{degree}C, the yield strength increased by 8 to 30%, ductility increased insignificantly, with almost no change in ultimate tensile strength. All cladding exhibited ductile-to-brittle transition behavior during Charpy impact testing, because of the dominance of delta ferrite failures at low temperatures. On the upper shelf, energy was reduced 15 and 20%, while the lateral expansion was reduced 43 and 41%, owing to irradiation exposure of 2 and 5{times}10{sup 19} neutrons/cm{sup 2} (>1 MeV), respectively. In addition, radiation damage resulted in 13 and 28{degree}C shifts of the Charpy impact transition temperature at the 41-J level for the low and high fluences, respectively. Furthermore, irradiation exposure of 12.5-mm-thick compact specimens (0.5TCS), to an average fluence of 2.41 {times} 10{sup 19} neutrons/cm{sup 2} (>1 MeV), resulted in decreases in the initiation fracture toughness, J{sub Ic}, and the tearingmore » modulus in the test temperature range. This is in agreement with the reduction in both the Charpy V-notch upper-shelf energy and the lateral expansion. 14 refs., 26 figs., 13 tabs.« less