2017 Volume 66 Issue 4 Pages 136-141
UCL tests were performed in hydrogenated steam to accelerate SCC initiation in PWR Primary water environment. Although surface finishing effect on SCC behavior has been discussed by many researchers, it remains unresolved. The surface finishing effect on the test results was investigated by using two types of UCL specimens. One specimen was polished by the emery paper （emery polished） and the other was polished the emery paper and OP-S （mirror polished）. UCL tests were interrupted every 450 hours. Some micro cracks whose length is less than one grain boundary length were observed by SEM on the mirror polished specimen after 450 hours, but no cracks observed on the emery polished specimen after 450 hours. When cracks shorter than one grain boundary length were eliminated, time dependency of total crack number was almost the same in both the specimens up to 900 hours. After 1350 hours, total crack number on the emery polished specimen was larger than that of the mirror one. The maximum crack length of the emery polished specimen is larger than that of the mirror polished specimen. Crack volume was calculated from crack data under the assumption that crack depth and crack width were proportional to crack length. The relationship between the sum of AE energy and total crack volume suggested that crack depth in the mirror polished specimen might be larger than one in the emery specimen, or that contribution of coalescence and propagation of micro cracks in these specimens might be different.
