Patent Number: 055235131
Section: claims

1. A method of decontaminating the surface of a body carrying radioactive contaminants which comprises treating the surface with a decontaminant comprising a solution of tetrafluoroboric acid HBF.sub.4, treating the resultant liquor comprising decontaminant and dissolved species removed from the body surface with a first chemical agent which on reacting with the dissolved species yields insoluble compounds and regenerated decontaminant solution, and characterised in that the regenerated decontaminant solution is further treated to cause removal of the first chemical agent from the decontaminant solution. 2. A method as in claim 1 and wherein the first chemical agent comprises an acid. 3. A method as in claim 2 and wherein the first chemical agent comprises oxalic acid. 4. A method as in claim 1 and wherein the said further treatment comprises an oxidation treatment. 5. A method as in claim 4 and wherein the oxidation treatment comprises addition of a second chemical agent which is an oxidising agent. 6. A method as in claim 5 and wherein the oxidising agent is selected from potassium permanganate, potassium dichromate, lead (IV) compounds and cerium (IV) compounds. 7. A method as in claim 4 and wherein the oxidation treatment comprises photolytic decomposition. 8. A method as in claim 1 and wherein a third chemical agent is added to the decontaminant liquor to increase the rate of removal of the first chemical agent. 9. A method as in claim 8 and wherein the third chemical agent comprises a peroxide. 10. A method as in claim 1 and which includes the step of further treating the regenerated decontaminant solution by passing that solution through an ion exchange medium. 11. A method as in claim 1 and wherein the regenerated decontaminant solution is obtained in substantially pure form and is re-applied in such form to decontaminate further the surface of the said body. 12. A method as in claim 1 and wherein sold matter contained in the decontaminant liquor is separated from the liquor prior to treatment to add the first chemical agent thereto. 13. A method as in claim 1 and wherein precipitate produced by addition of the first chemical agent is separated from the decontaminant liquor prior to treatment to remove the first chemical agent. 14. A method as in claim 1 and wherein addition of the first chemical agent and the treatment to remove the chemical agent are carried out as successive steps in a common reactor vessel. 15. A method as in claim 14 and wherein different chemical agents are added to the vessel via different inlets. 16. A method as in claim 1 and wherein the regenerated HBF.sub.4 decontaminant solution is treated, at the end of decontamination, with a material to neutralise the acid. 17. A method as in claim 16 and wherein calcium hydroxide is added to the regenerated HBF.sub.4 solution.