Decontamination of mild steel surfaces containing medium and high-fired PuO[sub 2]
- Larry R.
- Robert
- Wolfgang H.
- Billy J.
Decontamination of surfaces contaminated with fission products and/or non-fired actinide oxides is generally accomplished chemically with chelating agents that have high stability constants for solubilization and removal of the contaminants. The effectiveness of the removal of soluble fission products and non-fired actinide oxides is determined by the ability of the decontamination agent to solubilize the contaminants and not dissolve the contaminated surface material. For decontamination of stainless steel, plastic, concrete, and other materials that are impervious to most decontamination agents, the most harsh decontamination agents, including acid solutions, can be used to remove contaminants. However, if the contaminants are refractory oxides, such as medium-fired or high-fired PuO{sub 2} and the surface is easily attacked by harsh decontamination agents, then the decontamination effort becomes much more difficult. With medium of high-fired PuO{sub 2}, common decontamination agents are ineffective in solubilizing and removing the Pu contaminant from a mild steel surface. When Pu is heated to high temperatures three forms of PuO{sub 2} can result; non-fired or low-fired PuO{sub 2} at <200 C, medium-fired PuO{sub 2} at 450-650 C, and high-fired PuO{sub 2} at >800 C. Common decontamination agents can be effective for solubilizing and complexing non-fired or low-fired PuO{sub 2} but will be totally ineffectual for solubilizing and complexing medium-fired and high-fired PuO{sub 2}. Attempts to decontaminate with HNO{sub 3}-HF solution will result in dissolving the mild-steel materials. The only complexing agent that has the ability to break the Pu-O bond is the fluoride ion heated above 40 C in an acid solution. To decontaminate medium and high-fired PuO{sub 2}, inhibited fluorides can break the Pu-O bond, solubilize and complex the dissolved Pu and only slowly attack a mild-steel surface. The use of fluoboric acid heated in mild acid solutions was found to be an effective inhibited fluoride for solubilizing and complexing all forms of PuO{sub 2} for decontamination of mild-steel surfaces. The boron atom in fluoboric acid (HBF{sub 4}) forms a strong complex with the fluoride ion that allows solubilization of PuO{sub 2} and inhibits the dissolution of materials, including mild-steel components. The development of this decontamination methodology is presented in this paper.
- Research Organization:
- Los Alamos National Laboratory
- Sponsoring Organization:
- DOE
- OSTI ID:
- 977473
- Report Number(s):
- LA-UR-04-0947; LA-UR-04-947
- Country of Publication:
- United States
- Language:
- English
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