Measurement of equilibrium partition coefficient of cesium, iodine and tellurium between liquid sodium and cover gas

Objectives of present study is to obtain equilibrium partition coefficient, Kd, of cesium (Cs), iodine (I) and tellurium (Te) between liquid sodium and cover gas. Kd is defined as the ratio of (mol fraction in gas phase)/(mol fraction in liquid phase). In the experiment, one of non-radioactive materials of Cs, Nal and Te was added into sodium pool. Vapors of these volatile fission product simulants and sodium evaporated and equilibrated in the argon carrier gas at 450deg C-650deg C. The results revealed the followings. (1) Because of the high vapor pressure, cesium takes the highest Kd value (20-100). The scatter of cesium data is smallest and the data agree best with Casseleman's theoretical values based on the constitutional diagram of sodium/cesium alloy. (2) Kd of iodine is very sensitive to the change of system state. The data scatters widely such as 0.02-0.5 to 450deg C and 0.3-0.8 to 650deg C. (3) Kd of Te was 10-5-10-4. The relation between Kd of Te and liquid sodium temperature agrees with the Casseleman's equation assuming sodium/tellurium compounds which are less vapor forming. (author)