Development of sodium removal technology; Basic examination results of sodium removal rate by wet nitrogen gas

Hirakawa, Yasushi ; Yoshida, Eiichi; Gunji, Shigeru*

The sodium removal technology containing radioactive nuclides is required for inspection and repair of sodium system components and decommissioning of sodium cooled fast reactors. In order to evaluate the efficient sodium removal conditions, the sodium removal rate by the moisture gas cleaning process was examined. Experiments were conducted by simulating residual sodium in the bottom of a vessel and in the crevice parts of components. The experimental parameters were sodium temperature, moisture concentration in career gas (N), and surface area of sodium. (1)The effect of the moisture gas cleansing parameters has been investigated and quantitative data for the sodium removal rate were obtained in this study. (2)Sodium temperature and sodium-phase (liquid or solid) did not affect sodium removal rate from 80 C to 150 C sodium temperature. However, at the 180 C sodium temperature of sodium removal rate declined. (3)Moisture concentration in the nitrogen gas greatly affected the sodium removal rate increased with increasing moisture. (4)The sodium removal rate was influenced of sodium surface direction (facing upward or downward). Facing upward the sodium surface had higher sodium removal rate than facing downward. (5)The unstable rapid reaction similar to combustion was observed in some cases during experiments of sodium removal by wet nitrogen gas.