Radioactive gas solidification device

The present invention concerns a radioactive gas solidification device used in a nuclear fuel reprocessing plant. A sputter electrode main body comprises transition metals, such as nickel, copper or the like. A plurality of circular grooves with two steps are formed each at a substantially equal interval in the circumferential direction of the electrode main body. Rear earth metals, such as yttrium and scandium are filled in the stepped grooves to deposit and bury a rail having a protruded cross section. If sputtering is proceeded and the wall thickness is reduced to the second step for the rail, the surface area of the sputtering is abruptly reduced to reduce the amount of sputtering. Accordingly, the gas pressure in the solidification vessel is increased. The opening degree of a radioactive gas supply valve is controlled so that a pressure controller maintains an appropriate gas pressure. A solidication factor measuring device measures the solidification value of radioactive gases based on the flowrate value of the radioactive gases. With such a constitution, the reduction of wall thickness of the sputtering electrode can be accurately determined, thereby enabling to improve the efficiency upon using the sputtering electrode. (I.N.)