Investigation for the sodium leak in MONJU; Sodium leak and fire test-I

As a part of the work for investigating the sodium leak accident which occurred in the Monju reactor (hereinafter referred to as Monju) on December 8, 1995, threetests, (1)a sodium leaktest, (2)a sodium leak and fire test-I, and(3)a sodium leak and fire test-II, were carried out at OEC/PNC, The main objectives of these tests were to confirm the leak and burning behavior of sodium from the damaged thermometer, and the effects of the sodium fire on the integrity of the surrounding structure. This report describes the results of the sodium fire test-I carried out as a preliminary test. The test was performed usjng the SOLFA-2 (Sodium Leak, Fire and Aerosol) facility on April 8, 1996. In this test, sodium heated to 480circC was leaked for approximately l.5 hours from a leak simulating apparatus and caused to drop onto a ventilation duct and a grating with the same dimensions and layout as those in Monju. The main conclusions obtained from the test are shown below: (1)Observation from video cameras in the test revealed that jn the early stages of the sodium leak, sodium dripped out of the flexible tube of the thermometer. This dripping and burning expanded in range as the sodium splashed on the duct. (2)No damage to the duct itself was detected. However, the aluminum louver frame of the ventilation duct's lower inlet was damaged. lts machine screws came off, leaving half of the grill (on the grating side) detached. (3)NO large hole, like the one seen at Monju, was found when the grating was removed from the testing system for inspection, although the area centered on the point were the sodium dripped was damaged in a way indicating the first stages of grating failure. The 5mm square lattice was corroded through in some parts, and numerous blades (originally 3.2 mm thick) had become sharpened like the blade of a knife. (4)The burning pan underside thermocouple near the leak point measured 700circC in within approximately 10 minutes, and for the next ...