Development of Under-Sodium Visualization Program for In-Service Inspection of In-Vessel Structures in a Sodium-cooled Fast Reactor

For the periodic safety assurance of a sodium-cooled fast reactor (SFR), the in-service inspection (ISI) of a SFR should be applied according to the ASME code rules and guidelines. As the liquid sodium of a sodium-cooled fast reactor (SFR) is not transparent to light, a conventional visual examination cannot be used for the inspection of in-vessel structures under a sodium level in a reactor vessel. Ultrasonic inspection technique is a unique method to inspect the in-vessel structures submersed in sodium. Under-sodium viewing techniques using ultrasonic immersion sensors and waveguide sensors have been developed for the inspection of the reactor core and internal components in the SFR. Recently a novel plate-type ultrasonic waveguide sensor using the A0 mode leaky Lamb has been developed. The ultrasonic waveguide sensor modules are installed into the ISI access ports in the reactor head and the ultrasonic waves transmit through the waveguide plate in the hot sodium, as shown in Fig. 1. In this study, the visualization inspection program which is named as Under-Sodium MultiView have been developed for the application of the waveguide sensor module to the in-service inspection of in-vessel structures in a SFR