Performance Verification of Reactor Unidentified Leakage Detection System

The real time detection of small leak flow is very important for the nuclear reactor safety. The early perception of the malfunction of the nuclear system due to the coolant leak can give a sufficient time required for the operator action. In the present study, an improved concept of small leak detection system was proposed and an experimental facility to evaluate the performance of the system was constructed. In the small leak detection system, the leaked steam is sampled using porous type sampling devices which are installed on the air circulation loop and the time variation of the humidity on the down stream of the loop is measured in real time. The main concept of the system proposed in the present study is to achieve fast and obvious leak detection with the aid of suction mode during the air circulation loop operation. Using the test facility, high pressure saturated steam under the condition of real nuclear power plant operation could be supplied to the test section. The small leakage flow was simulated on the wall of the pipe system simulator and the time variation of the humidity due to the leakage was detected through the circulation loop. The effects of the suction time, the air circulation loop length, and the distance form the leak point to the porous sampling device on the humidity signal were investigated. And also the leak detection performance using suction mode operation was compared to that using diffusion mode operation, which showed that faster and clearer leak detection.