METHOD FOR REMOVING RUTHENIUM FROM NITRIC ACID SOLUTION

摘要

PURPOSE:To enhance the removing efficiency of ruthenium by reducing volatile ruthenium using a process and/or a unit (condenser) for condensing steam. CONSTITUTION:Radioactive waste liquid containing ruthenium and nitric acid is fed continuously from a waste liquid storage tank 1 to a first evaporator 2. The first evaporator 2 thermally evaporates the waste liquid to produce the vapor thereof which is fed to a first condenser 3 where the vapor is cooled and liquefied. Furthermore, NO and/or NO2 is fed from a reducing gas supply unit 4 to the condenser 3 where volatile ruthenium is reduced and dissolved into the condensed liquid. The condensed liquid is fed to a second evaporator 6 and the vapor thereof is liquefied by a second condenser 7 and fed to a purified waste liquid storage tank 8. In this regard, the volatile ruthenium and the reducing gas are caused to react in the condenser 3 and the ruthenium is reduced to a nonvolatile form having the oxidation number of 2 or 4 and dissolved into the condensed liquid. This method restrain the evaporation of ruthenium in the second evaporator 6.