Patent Number: 053405056
Section: claims

1. In a method for dissolving radioactively contaminated surfaces of articles made of metal, according to which the articles to be decontaminated are contacted with a decontamination agent comprising fluoboric acid in an aqueous solution with a strength of about 0.05 to about 50 mol/liter and where the surfaces of said contaminated articles are dissolved by said decontamination agent, the improvement comprising: changing said radioactively contaminated surfaces into an oxidized state providing an increased and quicker solubility of said radioactively contaminated surfaces in fluoboric acid by contacting said radioactively contaminated surfaces with a single aqueous solution of an oxidizing agent containing less than about 20 percent by volume and said fluoboric acid. 2. A method in accordance with claim 1, wherein hydrogen peroxide is used as said oxidation agent. 3. A method in accordance with claim 2, wherein hydrogen peroxide in a concentration of less than 20 percent by volume is used as said oxidation agent. 4. A method in accordance with claim 1, wherein a mixture of hydrogen peroxide and an additional oxidation agent is used as said oxidation agent. 5. A method in accordance with claim 1, wherein said surfaces of said radioactively contaminated metal articles are contacted with said single aqueous solution comprising fluoboric acid at about 5% concentration and about 0.5% by volume, based upon said single aqueous solution, of hydrogen peroxide. 6. A method in accordance with claim 4, wherein said surfaces of said radioactively contaminated metal articles are contacted with said single aqueous solution comprising fluoroboric acid at about 5% concentration, about 0.5% to about 2%, by volume based upon said single aqueous solution, hydrogen peroxide and about 0.1 to 2%, by volume based upon said single aqueous solution, potassium permanganate. 7. A method in accordance with claim 1, wherein said surfaces of said radioactively contaminated metal are first degreased. 8. A method in accordance with claim 1, wherein said surfaces of said radioactively contaminated metal articles are dissolved in a bath comprising fluoboric acid and said oxidation agent at about room temperature. 9. A method in accordance with claim 8, further comprising electrolytically regenerating a contaminated mixture of dissolved metal, fluoboric acid and oxidation agent at a temperature of about 25.degree. C. at a current density of about 5 to about 500 mA/cm.sup.2. 10. A method in accordance with claim 9, wherein said electrolytically regenerating of said contaminated mixture is performed below the voltage leading to the generation of oxygen. 11. A method in accordance with claim 8, wherein said electrolytically regenerating of said contaminated mixture is performed until its metal content is less than about 0.1 g per liter, after which remaining fluoboric acid is reused for repeating the process. 12. A method in accordance with claim 8, wherein following the performance of said electrolytically regenerating said bath is neutralized with addition of calcium hydroxide, sedimentation is filtered and/or sedimented forming a contaminated filter cake, said contaminated filter cake is solidified and decontaminated, and remaining filtrate, free of radioactivity and of metal, is placed into a sewage disposal system. 13. A method in accordance with claim 8, wherein said electrolytically regenerating of said contaminated mixture is performed until its lead content is less than about 0.1 g per liter, after which this solution, which still contains radioactivity, is fed through a cation exchanger, by means of which fluoboric acid free of radioactivity and lead is obtained. 14. A method in accordance with claim 6, wherein the decontaminated metal articles are cleaned by flushing with water. 15. A method in accordance with claim 6 for decontamination of radioactively contaminated closed pipe systems of metal, wherein said single aqueous solution is pumped into the pipe system, recirculated for a time, and finally conducted through an ion exchanger. 16. A method in accordance with claim 6 for decontamination of radioactively contaminated closed pipe systems of metal, wherein said single aqueous solution is pumped into the pipe system and is recirculated for a time, after which contaminated solution is pumped out and the pipe system is rinsed with water. 17. A method in accordance with claim 16, wherein the pumped out solution is electrolytically regenerated. 18. A method for dissolving radioactively contaminated metallic surfaces, comprising: contacting said surfaces with an aqueous solution comprising fluoboric acid at about 5 to 20 percent concentration and an oxidation agent. 19. A method according to claim 18, wherein said oxidation agent comprises about 0.05 to about 2 volume percent, based upon said aqueous solution, hydrogen peroxide. 20. A method according to claim 19, wherein said oxidation agent further comprises about 0.1 to about 2 percent, based upon said aqueous solution, potassium permanganate. 21. A method according to claim 19, wherein said metallic surfaces comprise lead and said contacting ceases prior to said solution attaining a lead concentration of about 55 grams lead per liter. 22. A method according to claim 19, wherein said metallic surfaces comprise lead and said contacting is continued for about 50 to about 150 minutes.