Mitigation of Cesium and Cobalt Contamination on the Surfaces of RAM Packages

Techniques for mitigating the adsorption of 137Cs and 60Co on metal surfaces (e.g., RAM packages) exposed to contaminated water (e.g., spent-fuel pools) has been developed and experimentally verified. The techniques are also effective in removing some of the 60Co and 137Cs that may have been adsorbed on the surfaces after removal from the contaminated water. The principle for the 137Cs mitigation technique is based upon ion-exchange processes. In contrast, 60Co contamination primarily resides in minute particles of CRUD that become lodged on cask surfaces. CRUD is an insoluble Fe-Ni-Cr oxide that forms colloidal-sized particles as stainless steels corrode. Because of the similarity between Ni+2 and Co+2, CRUD is able to scavenge and retain traces of cobalt as it forms. A number of organic compounds have a great specificity for combining with nickel and cobalt. Ongoing research is investigating the effectiveness of chemical complexing agent, EDTA, with regard to its ability to dissolve the host phase (CRUD) thereby liberating the entrained 60Co into a solution where it can be rinsed away.