Performance test of under sodium viewer in Monju

Aizawa, Kosuke ; Togashi, Yoshinori; Sasaki, Koei   ; Chikazawa, Yoshitaka  ; Fukuie, Masaru*; Jimbo, Noboru*

Inspection technique in opaque liquid metal coolant is one of the important issues for the safety warranty of Liquid Metal Fast Breeder Reactor (LMFBR) core. A performance test of Under Sodium Viewer (USV) which was developed to detect obstacles in reactor vessel of LMFBR Monju was carried out. The ultrasonic sensors and reflectors are located across the core inside the Monju reactor vessel. The USV detects the obstacle between the core top and the bottom of Upper Core Structure (UCS) by differences of echo signals. This reports showed the USV performance test in Monju before power operation. In the test, the basic echo signals in various conditions were accumulated and signal to noise ratio met with the design value. Measured signals with and without obstacles showed difference clearly. Those experimental results showed that basic performance of the USV to detect an obstacle between the core and UCS.