Experimental Evaluation of Wire Type Leak Detector Layout for Prototype Fast Breeder Reactor (PFBR)

Wire type leak detectors working on conductivity principle are used for detecting sodium leak in the secondary sodium circuits of FBRs. It is required to assess the performance of these detectors and confirm that they are meeting the requirements. A test facility by name LEENA was constructed at Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam to test the wire type leak detector lay out by simulating sodium leaks of different rates. This test facility consists of a sodium dump tank, a test vessel, interconnecting pipelines with valves, micro filter and test section with leak simulators. There are three different test sections in the test set up of length 1000 mm each. These test sections simulate piping of Prototype Fast Breeder Reactor (PFBR) secondary circuit and the leak detector layout in full scale. All test sections are provided with leak simulator. A leak simulator consists of a hole of size one mm drilled in the test section and closed with a tapered pin. The pin position is adjusted by a screw mechanism and there by the annular gap of flow area is varied for getting different leak rates. Test facility was commissioned and 20 experiments were attempted at 350°C to 550°C. Out of 20 experiments 11 experiments were successfully completed and 9 experiments were terminated in between due to the choke in the simulator hole. From the experimental data it is found that sodium leak rate of 200 g/h and above can be detected within 6 hours. A relationship between leak rate and detection time was established from the experimental results and found that sodium leak rate of 100g/h is likely to be detected in 11.4 hours. This paper deals with the details of wire type leak detector layout for the secondary sodium circuit of PFBR, performance requirement of leak detection system as per codes, description of test facility, experimental procedure and test results. Paper also reviews the experiment conducted in CEA, Cadrache and compares with results of present experimental study.