[en] Object: To prevent radioactive rare gases from being leaked to atmosphere and to secure safety of gas storage for a long time. Structure: Radioactive rare gases separated and condensed from waste gases by a low temperature adsorbing device or the like are once stored under negative pressure in a gas holder through an introducing line. When the quantity of storage reaches a predetermined level, the line in communication with a storage vessel is opened to have the gases adsorbed with adsorbent within the storage vessel. This storage vessel is held at a low temperature by liquid nitrogen fed through the line to increase adsorbing power of the adsorbent. (Kamimura, M.)