Patent Number: 
Section: claims

1. A method of treating the surface of a steel package, in order to reduce contamination by radioactive cesium, the method comprising the steps of:a) providing a steel package;b) prior to exposing the package to radioactive cesium, pre-washing the package with a cation-containing pre-wash solution having a pH greater then about 6 and less than about 8, the pre-wash cation being selected from one or more of the group consisting of Na+, Li+, Cs+, Rb+, Ag+, Tl+, K+, and NH4+;c) exposing the package to radioactive cesium; andd) after exposing the package to radioactive cesium, post-washing the package with a cation-containing post-wash solution having a pH greater than about 6 and less than about 8, the post-wash cation being selected from one or more of the group consisting of Na+, Li+, Rb+, Ag+, Tl+, K+, and NH4+;wherein the pre-wash solution comprises a cesium salt selected from the group consisting of cesium sulfate, cesium chloride, cesium nitrate, and cesium acetate. 2. The method of claim 1 wherein the concentration of Cs+ in the pre-wash solution is greater than approximately 0.1 molar. 3. The method of claim 1 wherein the cation in the post-wash solution is selected from the group consisting of K+ and NH4+−. 4. The method of claim 3 wherein the concentration of K+ in the post-wash solution is greater than approximately 0.1 molar. 5. The method of claim 3 wherein the concentration of NH4+ in the post-wash solution is greater than approximately 0.1 molar. 6. The method of claim 1 wherein the cation used in the pre-wash solution is different that the cation used in the post-wash solution. 7. The method of claim 1 wherein the post-wash solution additionally comprises one or more complexing agents selected from the group consisting of ammonium fluorosilicate, oxalic acid, disodium chromotropic acid, glutamic acid, and sodium salicylate. 8. The method of claim 1, wherein the pre-wash solution additionally comprises one or more complexing agents selected from the group consisting of ammonium fluorosilicate, oxalic acid, disodium chromotropic acid, glutamic acid, and sodium salicylate. 9. The method of claim 1, wherein the steel package comprises a spent fuel shipping cask. 10. The method of claim 1, wherein the cation in the post-wash solution is K+. 11. The method of claim 1, wherein the surface of the steel package is contaminated with clay.