Removing method of radioactive gaseous volatile material

Radioactive volatile materials are solidified by a cooler disposed at a pre-stage taking notice on the fact that saturated steam pressure of chemical species (for example, Tc:Tc2O7) present in exhaust gases is lowered by lowering temperature, and they are removed by a solid particle removing device (for example, scrubbers or filters filled with zeolite, silica gel and the like) disposed at post-stage. With such procedures, when the air temperature containing gaseous Tc is 40degC, for example, the air temperature is lowered to 0degC to decrease the amount of gaseous Tc present in the air to 1/1000. Further, the entire residue is solidified. The solidified materials are removed by the solid particle remover. (T.M.)