Decontamination of metal surfaces in nuclear power reactors

A method of decontaminating metal surfaces coated with oxides containing radioactive substances comprising:

• (A) providing a decontamination solution which comprises
• (1) water;
• (2) about 0.02 to about 0.5% of at least one water-soluble organic acid which has an equilibrium constant in a complex with ferric ion of at least 10.sup.9, and which is capable of producing a pH of 2 to 3 in water;
• and
• (3) about 0.01 to about 0.4% of a chelate in free acid form which has an equilibrium constant in a complex with ferric ion of about 10.sup.15 to about 10.sup.19, and which is soluble at at least 0.4% at 40.degree. C. in water having a pH of about 2 to about 3;
• (B) heating said decontamination solution to about 70.degree. to about 200.degree. C.;
• (C) circulating said decontamination solution over said metal surfaces and through a cation exchange resin until the radioactivity of said decontamination solution does not increase significantly after contacting said metal surfaces;
• (D) providing an oxidizing solution which comprises
• (1) water;
• (2) 0.2 to 2.5% of an alkali metal permanganate;
• and
• (3) about 0.2 to about 2.5% of an alkali metal hydroxide;
• (E) heating said oxidizing solution to about 70.degree. to about 200.degree. C.;
• (F) circulating said oxidizing solution over said metal surfaces until the dichromate level in said oxidizing solution ceases to increase significantly;
• and
• (G) circulating said decontamination solution over said metal surfaces and through a cation exchange resin until the radioactivity of said decontamination solution does not increase significantly after contacting said metal surfaces.