Study on in-vessel ISI for JOYO; Thechnical survey of under sodium non-destructive inspection technique and study of application concept

Ariyoshi, Masahiko; Ishida, Koichi

This report is concerning the in-vessel in-service inspection (ISI) technology for the experimental fast reactor JOYO. The present ISI method in JOYO is not able to confirm the integrity of the core structure directly, expecting the visual inspection for the top of core assemblies from above the rotating plug. The purpose of this examination is to progress of the ISI method, and to confirm the integrity of the core structure directly. The core support plate is an important structure and it is selected for the object of in-vessel ISI. From the viewpoint of the influence on the plant, it is regarded impotant the method without all sodium draining, and the remote operation from above of the shielding plug. As a result, following technology is thought promising. (1)Under sodium inspection technique by means of ultrasonic method (it is able to apply in-vessel ISI without all sodium draining). (2)Nondestructive inspection technique by laser based ultrasonic method (it is superior in remote operating) (3)The local sodium discharge mechanism (it makes possible to apply laser based ultra sonic method for under sodium inspection) These technologies were investigated, examined, and the concept applied to ISI in JOYO core support plate was examined. Moreover, the problem when these were applied to in-vessel ISI in JOYO was picked up.