Small-scale penetration leak test in ALPHA program

Small scale penetration leak test has been performed as a part of ALPHA program at JAERI since 1990. Two series of experiments were performed in the test using test sections which simulate important parts of an electrical penetration assembly (EPA) in a Japanese pressurized water reactor. One of the test sections simulates an alumina module and the other includes silicone resin portion of the EPA. The test section was installed in a leak test vessel in which one region simulated inside of the containment and the other region simulated outside of the containment. Four experiments were performed using the alumina module test section. The test section was heated up to 720 K at maximum 1.8 MPa. No leakage was detected in the experiments. Two experiments were performed using the silicone resin test section at near atmospheric pressure. Initial leak path formation was detected at about 420 K. It was found that heat conduction along metal portion had strong influence on melt progression of the resin. It was also found from the strain measurement that the thermal loads were predominant over the pressure loads. From the results of the experiments, it is considered that the alumina module will keep integrity in severe accident conditions, although the silicone resin is estimated to melt at high temperature. Therefore, the EPA as a whole is estimated to maintain leak-tightness during the severe accident