International programme on nondestructive testing of steel components in nuclear power plants

After nondestructive tests were carried out as stipulated in the standard, large defects were sometimes discovered, and the usefulness and reliability of such testing method for the safety evaluation of important structures have been questioned. In order to obtain the answer as perfect as possible to this question on the capability of nondestructive tests, the international cooperation research on the detection of defects in welded parts (PISC program) was begun, which evaluates the methods of detecting defects arising in the welded parts of pressure vessels and pipings and measuring their dimensions. Moreover, this international cooperation research is continued still for the purpose of internationally unifying the high capability techniques by offering the results of the PISC program to the organizations which decide the national codes and standards. The PISC program is one of the activities of PWG3 of CSNI of OECD-NEA. At present 15 countries take part in the PISC program. Three stages of the PISC program are described. The nondestructive testing method examined is ultrasonic flaw detection method. The reliability of pressure vessels and pipings tends to be improved through this important program. (Kako, I.)