In-Core Crack Growth Rate Studies on Irradiated Austenitic Stainless Steels in BWR and PWR Conditions in the Halden Reactor

摘要

In-core crack growth rate measurements have been made on small Compact Tension (CT) specimens prepared from irradiated 304, 347 and 316 NG stainless steels with five different fluences, ranging from 0.09 to 2.5 × 10~(22) n/cm~2 ( > 1MeV). The specimens were instrumented for on-line propagation monitoring with the reversing DC potential drop method and equipped with pressurised bellows that enabled on-line variation of applied stress intensity level. The tests were performed in BWR oxidizing and reducing environments at 280 ℃ and in PWR conditions (with 2 -3pm Li and 1000-1200 ppm B), at 335 ℃. The microstructural and microchemical characteristics of the irradiated materials are described. Significant reductions in crack growth rate were recorded for the lower fluence materials in reducing environments while less marked changes in growth rate were observed in the high dose materials with long crack lengths and / or high (invalid) applied stress intensity levels. The cracking response is examined in terms of the operating conditions, the materials' mechanical properties (e.g. yield strength) and K/size effects. Comparisons are also made with results from other crack growth studies on irradiated materials.