Thermal-hydraulic tests with out-of-pile test facility simulating natural convection capsule

Power transient tests for the fuels of light water reactors are to be carried out in the Japan Materials Testing Reactor (JMTR) using capsule-type irradiation test facilities, and the integrity of the fuels is to be investigated by the tests. Prior to the irradiation tests of the fuels, the out-of-pile test facility, which had an electric heater pin instead of a test fuel pin, was designed and fabricated to simulate the capsules used in the power transient tests. Using this facility, necessary tests for the realization of the irradiation tests and the planning of the test methods were carried out. In the present report, the outline of the out-of-pile test facility, the test plan and the tests simulating natural convection capsule were described. As a result of the tests, it was found that the power of the heater pin with a diameter of 9.5 mm can achieve to 600 W/cm without transition from nucleate boiling to film boiling under BWR and PWR coolant pressure conditions, and it became clear that the irradiation tests up to 600 W/cm of BWR and PWR fuels with their outer cladding diameter of 9.5 mm can be realized in JMTR. (author)