Patent Number: 047298553
Section: claims

1. A method of decontaminating metal surfaces contaminated with a radioactive deposit, comprising circulating between said deposit and a cationic ion exchange column an aqueous solution of a water soluble condensation reaction product of (1) a hydrazine compound having the general formula ##STR3## where each R is independently selected from hydrogen and alkyl to C.sub.4 ; and  (2) a water-soluble aliphatic polycarboxylic acid selected from the group consisting of oxalic acid, tartaric acid, citric acid, succinic acid, and mixtures thereof.  (1) preloading a cationic ion exchange column with N.sub.2 H.sub.5.sup.+ ;  (2) circulating between said deposit and said cationic exchange column, an aqueous solution iof dihydrazine oxalate, at a concentration of about 0.05 to about 10% by weight, based on solution weight, heated to about 870.degree. to about 125.degree. C.;  (3) passing an oxidizing solution over said deposit;  (4) repeating step (2); and  (5) adding an oxidant to said aqueous solution, whereby said dihydrazine oxalate is oxidized to nitrogen, carbon dioxide, and water. 2. A method according to claim 1 wherein said water-soluble aliphatic polycarboxylic acid is oxalic acid. 3. A method according to claim 1 wherein one mole of said hydrazine compound is reacted with one equivalent of said polycarboxylic acid. 4. A method according to claim 1 wherein the concentration of said condensation reaction product in said aqueous solution is about 0.05 to about 10% by weight, based on total solution weight. 5. A method according to claim 1 wherein the temperature of said aqueous solution is about 80.degree. to about 125.degree. C. 6. A method according to claim 1 including the additional last step of adding an oxidant to said aqueous solution. 7. A method according to claim 1 wherein said R group is H and said cationic exchange resin is loaded with N.sub.2 H.sub.5.sup.+. 8. A method according to claim 1 wherein said cationic ion exchange column is preloaded with the cationic moiety of said condensation reaction product. 9. A method according to claim 1 wherein said water-soluble aliphatic polycarboxylic acid is citric acid. 10. A method according to claim 1 wherein said water-soluble aliphatic polycarboxylic acid is tartaric acid. 11. A method according to claim 1 wherein said water-soluble aliphatic polycarboxylic acid is succinic acid. 12. A method according to claim 1 wherein each R is hydrogen. 13. A method according to claim 12 wherein said water-soluble aliphatic polycarboxylic acid is oxalic acid. 14. A method according to claim 1 including the additional last steps of passing an aqueous oxidizing solution over said deposit, followed by passing said aqueous solution iover said deposit a second time. 15. A method according to claim 14 wherein said oxidizing solution is a solution of an alkali metal hydroxide and an alkali metal permanganate. 16. A method of decontaminating a metal surface having a deposit thereon that contains radioactive elements, comprising 17. A method according to claim 16 wherein said oxidant is hydrogen peroxide.