Retention capacity of rock salt

In laboratory column experiments the capability of loose and of pressed rock salt for retaining radioactive gases was investigated. The experiments were performed at temperatures of 48deg C and 200deg C with regard to the conditions in a repository for heat and non-heat producing radioactive waste. The investigated gases were CH4, CO, CO2 (all C-14, HT, HTO, I2-131, CH3I-131, Kr-85 and Rn-222. An interaction with the rock salt was found only with two gases. HTO passed the column with a time delay depending upon the grain size of the rocksalt. A part of the injected iodine was retained on the rock salt and the other part passed the column without any delay just as the other gases. The amount of iodine retained on the salt was a function of the iodine concentration injected into the gas flow. At low concentrations more iodine was retained than at high concentrations. The isotopic exchange in the system HTO/H2S was also investigated. It could be confirmed that there is no influence on the retardation of HTO. (orig.) With 5 figs., 16 tabs., 8 refs