Transport and Deposition of Halide in Alkali Metal-Stainless Steel Systems, (IV)

Abstract

Solubility of sodium iodide in sodium is measured separately (a) with concentrations of major constituents leached from stainless steel in sodium and (b) with controlled concentration of oxide in sodium by the use of stainless steel capsule. The capsules loaded with 20 g sodium and 0.1–0.3 g powder of additives are heated at their upper part in a furnace and cooled at their bottom on brass plates. a. After a given period of run for sodium iodide equilibration, the distribution of the iodide and constituents is fixed in solidified sodium by quenching the capsules. Sodium samples taken from the sectioned capsule tube are submitted to sodium dissolution by steam for determining the iodide and to vacuum distillation for determining the constituents. The iodide solubility appears to be in a reverse correlation with concentrations of iron and nickel and to be insensitive to change in those of chromium, manganese and silicon. b. After a given period of run for sodium oxide equilibration, the sodium is solidified by quenching the capsule. Deposits on the capsule bottom is removed by sectioning the capsule tube and crystals of sodium iodide are introduced to the sectioned capsule on which an end plug is seal-welded. The capsule is again set under the large temperature gradient for a period of run for iodide equilibration. After fixing the iodide distribution in solidified sodium by the quenching, sodium samples are taken from the sectioned capsule tube and submitted to the sodium dissolution by steam for determining iodide in sodium. The iodide solubility data obtained from the present measurement are observed to be scarcely affected by the oxide concentration.