Development of an ultrasonic under-sodium scanner for the fast breeder test reactor

An Ultrasonic Under-Sodium scanner was developed and deployed in Fast Breeder Test Reactor (FBTR) at first during 1988 as a sweep-arm to scan the sodium plenum below the Core Cover Plate Mechanism (CCPM) of the reactor. It was again used in 1995 with the same objective of finding any protruding Sub-Assembly (S/A) in the interspace. During the first deployment, imaging of a part of the CCPM was also demonstrated and in the second, the detection of the Control Rod Drive Mechanisms (CRDM) kept lowered in the interspace. The paper describes the above deployments and the further experimental works under way.