Sodium fire test at broad ranges of temperature and oxygen concentration (II); The sodium burning rate and aerosol release rate in Nitrogen atmosphere

Kawada, Koji*; not registered  ; not registered; Himeno, Yoshiaki

[Purpose]A sodium pool fire test has been conducted in low oxygen containing nitrogen atmosphere to determine the sodium burning rate and aerosol release rate and compare them with calculated results by the SOFIRE-MII code. [Method]After installing a burning pan in a 3m test vessel, FRAT-1, the test vessel was filled with nitrogen gas includlng 3% in volume of oxygen gas. Then, the test was started by supplying a sodium (175400C) in the burning pan. The sodium burning rate was determined from the consumption rate of oxygen in the test vessel. The aerosol release rate was determined from total aerosol mass recovered. [Result](1)The sodium burning rate depends on the sodium pool temperature. As the result of a comparison of the experimental sodium burning rate values with the calculated ones by the SOFIRE-MII code, it was cleared that the former was lower than the latter in case of sodium pool temperature below 400 C and its differance was more than one order of magnitud at 175C. This reason is based on the fact that the burning rate is controlled by the masstransfer of oxygen at high pool temperature, while it is controlled by the reaction between oxygen and sodium at low pool temperature. In final, an empirical formula that agree with the experimental results was derived. (2)The aerosol release rate also depends on the sodium pool temperature. It is less than about 10% of the sodium burning rate. Assuming that the aerosol release rate is propotional to the sodium burning rate, an empirical formula which dependends on sodium pool temperature giving the maximum value at each sodium pool temperature was decided.