Investigation for the sodium leak in Monju; Sodium fire test-II

Uchiyama, Naoki; Takai, Toshihide  ; Nishimura, Masahiro ; Miyahara, Shinya  ; Miyake, Osamu; Tanabe, Hiromi

As a part of the work for investigating the sodium leak accident which occurred in Monju, sodium fire test-II was carried out using SOLFA-1 (Sodium Leak, Fire and Aerosol) facility at OEC/PNC. In the test, the piping, ventilation duct, grating and floor liner were an full-sized and arranged in a rectangular concrete cell in the same manner as Monju. Main objectives of the test are to confirm leak and burming behavior of sodium from the damaged thermometer, and effects of the sodium fire on integrity of the surrounding structure, etc. The main conclusions obtained from the test are shown as below. (1)Burning Behavior of Leaked Sodium : Images taken with cameras in the test reveal that in the early stages of the sodium leak, the sodium dropped down out of the flexible tube in drips. This dripping and burning were expanded in range as the sodium splashed on the duct, the grating and a support of thermocouples for the measurement of gas temperature. (2)Damage of Ventilation Duct and Grating : The temperature of the ventilation duct's inner surface fluctuated between approximately 600C and 700C. The temperature of the grating began rising at the outset of the test, then fluctuated between roughly 600C and 900C. The maximum temperature was about 1000C. After the test, damage of the ventilation duct and the grating was found. Damage of the duct was greater than that of Monju. (3)Effects on Floor Liner : The temperature of the floor liner under the leak point exceeded 1,000C at 3 hours and 20 minutes of the test; Post test inspection of the liner revealed five holes in the region of about 1m 1m under the leak point. There was also a decrease of a liner thickness on the north side and west side of the leak point. (4)Effects on Concrete : No surface damage of the concrete side walls and ceiling was found by the post test inspection. The floor concrete was eroded by a depth of 8 cm at maximum due to ...