Patent Number: 
Section: claims

1. A chemical decontamination method of chemically decontaminating radioactive nuclides from a metallic material surface contaminated by the radioactive nuclides, the method comprising the steps of: reductively decontaminating said radioactive nuclides using a reductive decontaminating agent containing at least two kinds of components; and then  decomposing said reductive decontaminating agent using a decomposing apparatus for decomposing at least two kinds of chemical substances in said reductive decontaminating agent;  wherein a catalyst decomposition column is used as the decomposing apparatus for decomposing at least two kinds of chemical substances in the reductive decontaminating agent. 2. A chemical decontamination method according to  claim 1 , wherein at least one element selected from the group consisting of platinum, ruthenium, vanadium, palladium, iridium and rhodium is used as a catalyst filled in said catalyst decomposition column, and an oxidizing agent is supplied in an inlet side of said catalyst decomposition column. claim 1 3. A chemical decontamination method according to  claim 2 , wherein a quantity of hydrogen peroxide is added in said decomposing step in an amount less than an equivalent weight of components trapped in a cation resin column after being decomposed in said decomposing step, when components trapped in the cation resin column are selectively decomposed, and the quantity of hydrogen peroxide added is more than an equivalent weight of the components trapped in the cation resin column when the components trapped in the cation resin column and components trapped in an anion resin column after being decomposed in said decomposing step at the same time. claim 2 4. A chemical decontamination method according to  claim 1 , wherein a quantity of hydrogen peroxide is added in said decomposing step in an amount less than an equivalent weight of components trapped in a cation resin column after being decomposed in said decomposing step, when components trapped in the cation resin column are selectively decomposed, and the quantity of hydrogen peroxide added is more than an equivalent weight of the components trapped in the cation resin column when the components trapped in the cation resin column and components trapped in an anion resin column after being decomposed in said decomposing step at the same time. claim 1 5. A chemical decontamination method of chemically decontaminating radioactive nuclides from a metallic material surface contaminated by the radioactive nuclides, the method comprising the steps of: reductively decontaminating said radioactive nuclides using a reductive decontaminating agent; and then  decomposing said reductive decontaminating agent using a decomposing catalyst for decomposing at least oxalic acid and hydrazine in said reductive decontaminating agent. 6. A chemical decontamination method according to  claim 5 , wherein said reductive decontaminating agent is a reductive acid solution of which a concentration of oxalic acid is 0.05 to 0.3 wt %. claim 5 7. A chemical decontamination method according to  claim 6 , wherein a quantity of hydrogen peroxide is added in said decomposing step in an amount less than an equivalent weight of components trapped in a cation resin column after being decomposed in said decomposing step, when components trapped in the cation resin column are selectively decomposed, and the quantity of hydrogen peroxide added is more than an equivalent weight of the components trapped in the cation resin column when the components trapped in the cation resin column and components trapped in an anion resin column after being decomposed in said decomposing step at the same time. claim 6 8. A chemical decontamination method according to  claim 5 , which further comprises an oxidative dissolving step for oxidatively dissolving chromium in a metal oxide on the metallic material surface contaminated by the radioactive nuclides into hexadic chromium using permanganate, for dissolving and removing the metal oxide. claim 5 9. A chemical decontamination method according to  claim 8 , wherein said reductive decontaminating step, said decomposing step, and said oxidative dissolving step are cyclically performed, and said reductive decontaminating step and said decomposing step are performed at least twice. claim 8 10. A chemical decontamination method according to  claim 9 , wherein a quantity of hydrogen peroxide is added in said decomposing step in an amount less than an equivalent weight of components trapped in a cation resin column after being decomposed in said decomposing step, when components trapped in the cation resin column are selectively decomposed, and the quantity of hydrogen peroxide added is more than an equivalent weight of the components trapped in the cation resin column when the components trapped in the cation resin column and components trapped in an anion resin column after being decomposed in said decomposing step at the same time. claim 9 11. A chemical decontamination method according to  claim 8 , wherein a quantity of hydrogen peroxide is added in said decomposing step in an amount less than an equivalent weight of components trapped in a cation resin column after being decomposed in said decomposing step, when components trapped in the cation resin column are selectively decomposed, and the quantity of hydrogen peroxide added is more than an equivalent weight of the components trapped in the cation resin column when the components trapped in the cation resin column and components trapped in an anion resin column after being decomposed in said decomposing step at the same time. claim 8 12. A chemical decontamination method according to  claim 8 , wherein a catalyst decomposition column is used in the decomposing step. claim 8 13. A chemical decontamination method according to  claim 12 , wherein at least one element selected from the group consisting of platinum, ruthenium, vanadium, palladium, iridium, and rhodium is used as a catalyst filled in said catalyst decomposition column, and an oxidizing agent is supplied in an inlet side of said catalyst decomposition column. claim 12 14. A chemical decontamination method according to  claim 8 , wherein said reductive decontaminating agent is a reductive acid solution of which a concentration of oxalic acid is 0.05 to 0.3 wt %. claim 8 15. A chemical decontamination method according to  claim 8 , wherein said reductive decontaminating agent is a reductive acid solution having a pH of 2 to 3. claim 8 16. A chemical decontamination method according to  claim 5 , wherein a catalyst decomposition column is used in the decomposing step. claim 5 17. A chemical decontamination method according to  claim 16 , wherein at least one element selected from the group consisting of platinum, ruthenium, vanadium, palladium, iridium, and rhodium is used as a catalyst filled in said catalyst decomposition column, and an oxidizing agent is supplied in an inlet side of said catalyst decomposition column. claim 16 18. A chemical decontamination method according to  claim 5 , wherein a quantity of hydrogen peroxide is added in said decomposing step in an amount less than an equivalent weight of components trapped in a cation resin column after being decomposed in said decomposing step, when components trapped in the cation resin column are selectively decomposed, and the quantity of hydrogen peroxide added is more than an equivalent weight of the components trapped in the cation resin column when the components trapped in the cation resin column and components trapped in an anion resin column after being decomposed in said decomposing step at the same time. claim 5 19. A chemical decontamination method according to  claim 5 , wherein said reductive decontaminating agent contains oxalic acid and hydrazine, and is a reductive acid solution having a pH of 2 to 3. claim 5 20. A chemical decontamination method according to  claim 5 , further comprising a cleanup step for cleaning system water using a mixed-bed resin, after the decomposing step. claim 5