Study on In-vessel ISI for JOYO - Core support plate inspection equipment under sodium -

Ariyoshi, Masahiko; Nakayama, Oukatsu

This report describes the feasibility study on the in-vessel inspection technique to be applied for the experimental fast reactor JOYO. Since JOYO is a sodium cooled fast reactor and the core structure components are in high temperature and fast neutron irradiation environment, material strength yields to decrease due to heat fatigue and irradiation induced embrittlement. The present surveillance method of testing structural material mechanical property, monitoring subassembly outlet temperature and sodium leak are not sufficient to detect a small crack. Therefore, the direct inspection method to confirm the core structure integrity needs to be developed considering the recent innovative technology. Since the core structure has a complicated form and components under sodium are not visible, the manipulator technology is essential which has various positioning functions. The core support plate was selected to be an important inspection item, and the method which combines ultrasonic non-destructive inspection technology and manipulator technology was examined. In this study, the core support plate inspection equipment concept was examined on the assumption that the inspection of the core support plate was executed under sodium. The sensor for the nondestructive testing is built into the inspection assembly which is loaded in most outer core area, and can be accessed to a low-pressure plenum sidewall by the manipulator. The linear array sensor which arranges several piezo-electric elements were applied to the sensor for the nondestructive testing, and for scanning the inspection object in non-contact. It was assumed for the concept of the manipulator that the sensor was positioned by moving of the arm and bending the joint. The technology of the Master Slave Manipulator for Laparoscopic Surgery was applied for the manipulator. A detailed examination is necessary for this concept in the future. And, the development of in-vessel inspection equipment is continued and prot