Transport and deposition of halide in alkali metal-stainless steel systems, (IV) - Measurement of sodium iodide solubility in sodium with major constituents of stainless steel and oxide in sodium

Solubility of sodium iodide in sodium is measured separately (a) with conce ntrations of major constituents leached from stainless steel in sodium and (b) with controlled concentration of oxide in sodium by the use of stainles s 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 thei r bottom on brass plates. (a) After a given period of run for sodium iodide equilibration, the distri bution of the iodide and constituents is fixed in solidified sodium by quen ching the capsules. Sodium samples taken from the sectioned capsule tube ar e submitted to sodium dissolution by steam for determining the iodide and t o vacuum distillation for determining the constituents. The iodide solubili ty appears to be in a reverse correlation with concentrations of iron and n ickel and to be insensitive to change in those of chromium, manganese and s ilicon. (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 r emoved by sectioning the capsule tube and crystals of sodium iodide are int roduced to the sectioned capsule on which an end plug is seal-welded. The c apsule is again set under the large temperature gradient for a period of ru n for iodide equilibration. After fixing the iodide distribution in solidif ied sodium by the quenching, sodium samples are taken from the sectioned ca psule tube and submitted to the sodium dissolution by steam for determining iodide in sodium. The iodide solubility data obtained from the present mea surement are observed to be scarcely affected by the oxide concentration.