Cladding Separate Effects Study: HSST Seventh Irradiation Series

摘要

The existence of a layer of tough weld overlay cladding on the interior of a light-water reactor pressure vessel could mitigate the damage caused during certain overcooling transients. This would occur if the cladding can keep a short surface flaw, which would otherwise become long, from growing either by impeding crack initiation or by arresting a running crack. Two aspects of cladding behavior critical to assessing its potential benefit are being examined within the HSST Program: irradiation effects on cladding toughness and the response of mechanically loaded, flawed structures in the presence of a cladding. A two-phase irradiation experiment is being conducted. In the first phase, Charpy impact and tensile specimens from a single-wire, submerged-arc stainless steel weld overlay were irradiated to 2 /times/ 10 sup 23 neutrons/m sup 2 (>1 MeV) at 288/degree/C. Typical, good quality pressure vessel cladding exhibited very little irradiation-induced degradation. In the second phase of irradiations, now in progress, a commercially produced three-wire series-arc weldment is being evaluated under identical irradiation and testing conditions as the first series. In addition, 0.5T compact specimens of both weldments and higher fluences are being examined. The specimens for Phase 2 have been successfully irradiated and all testing should be completed by the end of FY 1987.