Feasibility Test of a Waveguide Sensor for Ranging Inspection in a Sodium-cooled Fast Reactor

In the refueling process of an SFR, the assurance of clearance between the reactor core and the Upper Internal Structure (UIS) is very important because the rotating plug on the reactor head should be rotated to load new fuels as well as to unload spent fuels. However, the assurance of clearance between the reactor core and the UIS is very difficult because liquid sodium is optically opaque. One possible solution to check the clearance is the use of the ultrasonic wave technique. Since the ultrasonic wave can propagate through opaque sodium, obstacles between the reactor core and the UIS can be detected. In this work, a 10 m long horizontal beam waveguide sensor was developed and its feasibility for ranging inspection in an SFR is studied through several underwater experiments. In this work, the feasibility of the 10 m long horizontal beam waveguide sensor for ranging inspection was experimentally studied in water. Two hollow cylinder targets were inspected using the remote inspection module and the under sodium ranging program. Through several feasibility tests, it was shown that the clearance can be assured if the vertical distance between the sensor and the target is larger than 20 mm