METHOD FOR SURFACE DECONTAMINATION
A method for chemical decontamination of an oxide-coated surface of a metal structural part or of a system in a nuclear power plant with several cleaning cycles, involves oxidation steps, in which the oxide layer is treated with an aqueous solution containing an oxidation agent, and a subsequent decontamination step, in which the oxide layer is treated with an aqueous solution of an acid. At least one oxidation step is carried out in an acid solution and at least one oxidation step in an alkaline solution.
1 . A process for chemical decontamination of a surface having an oxide layer of a metallic component or of a system of a nuclear power station, which comprises the steps of:
performing a plurality of cleaning cycles each containing oxidation steps in which the oxide layer is treated with an aqueous solution having an oxidant and a subsequent decontamination step in which the oxide layer is treated with an aqueous solution of an acid, wherein at least one of the oxidation steps is carried out in an acidic solution and at least one of the oxidation steps is carried out in an alkaline solution; and
selectin the oxidant from the group consisting of O 3 , S 2 O 8 2− and a cerium(IV) compound for use in the oxidation steps.
2 . The process according to claim 1 , which further comprises setting a pH of the acidic solution to be <6 and a pH of the alkaline solution to be >8.
3 . The process according to claim 2 , which further comprises setting a pH of the acidic solution to be <4 and a pH of the alkaline solution of >10.
4 . (canceled)
5 . The process according to claim 1 , which further comprises selecting the oxidant from the group consisting of HMnO 4 , HMnO 4 with HNO 3 , and KMnO 4 with HNO 3 for use in an oxidation step in the acidic solution.
6 . The process according to claim 1 , which further comprises using KMnO 4 together with an alkalizing agent for an oxidation step in the alkaline solution.
7 . The process according to claim 6 , which further comprises using NaOH as the alkalizing agent.