METHOD FOR DECONTAMINATING CONTAMINATED STEEL SURFACES Russian patent published in 2000 - IPC

FIELD: decontaminating surfaces of various metals and alloys. SUBSTANCE: surfaces contaminated with weakly or strongly immobilized isotopes of various compositions are decontaminated by dissolving these contaminants, corrosion products, and oxide films in fluoride-containing solutions followed by rinsing and reconditioning decontaminating solution. Solution proposed for the purpose is mixture of hydrofluoric, boric, and orthophosphate acids with hydrofluoric acid concentration of 1-25 mole/l at molar ratio of hydrofluoric acid to boric acid being 2.0-4.0 mole/mole and that of hydrofluoric acid to orthophosphate acid, 20-100 mole/mole. In addition, it is proposed to correct chemical composition of fluoride-containing aqueous solution in the course of decontamination by adding concentrated aqueous solutions of hydrofluoric and/or tetrafluoroboric and orthophosphate acids and to conduct decontamination process at 20-90 C. Optimal chemical composition of orthophosphate acid enables use of high-concentration solutions at low temperatures. Proposed method enables removal of great variety of radioactive contaminants from surfaces of various metals and alloys using same composition of decontaminating solution and equipment, provides for desired safety due to closed-cycle process, minimal volume of radioactive wastes (approximately 300 g per ton of contaminated metal), minimal cost of chemical agents (for correction of solution only), deep decontamination of metal. EFFECT: improved decontaminating efficiency and environmental friendliness; provision for reuse of decontaminated metal. 3 cl, 1 tbl