Separating method and device for radioactive nuclides

A reducing agent is added to a radioactive solution containing neptunium and platinum ions, to reduce the platinum group ions to elemental metals and separate them by solid/liquid separation, the solution is brought into contact with a catalyst constituted with platinum. with such procedures, since the platinum catalyst is not degraded, and the efficiency is not lowered substantially permanently thereby enabling to attain reduction of neptunium into the four valence state and separation from the solution. (T.M.)