Improvements in or relating to the decontamination of metal surfaces in nuclear power reactors.

摘要

Method of decontaminating metal surfaces having radioactive oxide deposits thereon which comprises preparing a decontamination solution having a pH of from 1.5 to 4 comprising water, from 0.02 to 0.5% of a water soluble organic acid which has an equilibrium constant in a complex with ferric ion of at least about 10<9> and which is capable of producing a pH of from 2 to 3 in water, and from 0.01 to 0.4% of a chelate in free acid form which has an equilibrium constant in a complex with ferric ion of from to 10<1><5> to 10<1><9> and which is soluble at at least 0.4% at 40 DEG C in water having a pH of from 2 to 3. The decontamination solution is heated to from 70 to 200 DEG C and is placed in contact with the deposits on the metal surfaces until the level of radioactivity in the solution ceases to increase significantly. The metal surfaces are rinsed with water heated to from 70 to 200 DEG C. An oxidizing solution is prepared comprising water, from 0.2 to 2.5% of an alkali metal permanganate, and from 0.2 to 2.5% of an alkali metal hydroxide. Preferably, the amount of the permanganate exceeds the amount of the hydroxide when less than a 3% solution is used. The oxidizing solution is heated to from 70 to 200 DEG C, and is placed in contact with the deposits on the metal surfaces until the level of dichromate in the oxidizing solution ceases to increase significantly. The metal surfaces are rinsed with water, radioactive ions are removed from the decontamination solutions. the heated decontamination solution is placed in contact with the deposits on the metal surfaces until the level of radioactivity in the solution ceases to increase signicantly, and the metal surfaces are rinsed with water. …An apparatus is disclosed for decontaminating metal surfaces having a coating thereon which contains radioactive substances which comprises a decontamination tank (1-3) for holding the decontamination solution, means for circulating the decontamination solution between the decontamination tank an the metal surface, a cation exchange column (10) containing a cation exchange resin, means for circulating the decontamination solution between the decontamination tank and the cation exchange column (10), an oxidizing tank for holding an oxidizing solution, means for circulating for oxidizing solution between the oxidizing tank and the metal surfaces, a water tank for holding water, means for circulating water between the water tank and the metal surfaces, a mixed anioncation exchange column (12, 13) containing a mixed anioncation exchange resin, and means for circulating the water between the water tank and mixed anion-cationexchange column (12, 13).