Electro-decontamination of contaminated surfaces

Abstract

A decontaminating system 200 is provided that includes: (a) a decontaminating apparatus 100 including (i) an electrically conductive scrubbing shoe 104 having an inlet 204 for a gel-like material and (ii) an insulating standoff 116 positioned between the scrubbing shoe 104 and a surface 120 to be decontaminated to maintain a desired distance between the scrubbing shoe 104 and the surface 120; (b) a reservoir 216 for the gel-like material 124, the reservoir 216 being in communication with the inlet 204; and (c) a voltage source 224 in communication with the electrically conductive scrubbing shoe 104, whereby a current is passed through the gel-like material 124 applied to the surface 120, thereby removing contaminants from the surface 120.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] The present application claims the benefits of U.S. Provisional Application Serial No. 60 / 486,493, filed Jul. 10, 2003, entitled “Electrodecontamination for Mitigation of Airborne Contamination”, which is incorporated herein by this reference.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Contract Nos. DE-FG03-00ER82934 and DE-FG02-03ER83591 awarded by the Department of Energy.FIELD OF THE INVENTION [0003] The invention relates generally to decontamination of objects and surfaces and particularly to electrolytic decontamination of radioactive contaminated surfaces. BACKGROUND OF THE INVENTION [0004] Radioactive contamination of objects can occur in a wide variety of applications, such as nuclear-powered utility power pla...

AI Technical Summary

Benefits of technology

[0020] While not wishing to be bound by any theory, it is believed that, when voltage is applied to the gel-like material via the decontaminating apparatus, electrochemical reactions, optimally driven by a power waveform supplied by the power source, strip away the contaminated surface's top-most layers of atoms along with other contaminants that may be present. Current is carried by water molecules and the electrolytic agent in the gel-like material, and the electrolytic agent contributes electrons to oxidation reactions occurring at the anode and receives electrons from the reduction reactions occurring at the cathode. Depending on the system configuration, anionic or elemental contaminants may also be oxidized to a cation, and cation or elemental contaminants reduced to an anion. As a result, the material is stripped away, and becomes entrained in the gel-like material. Gentle scrubbing action using the abrasive pad on the contaminated surface disrupts oil and grease deposits, affording better electrical contact while simultaneously stirring or agitating the gel-like material to bring fresh gel-like material into contact with the contaminated surface. The decontaminating system can have a control to permit either reduction or oxidation potentials to be applied to the contaminated surface so that both metals and metal oxides, respectively, can be removed successfully. This capability can allow the system to remove effectively oxidized metal layers (e.g., rust) that may be present on the contaminated surface.

[0021] The present invention can have a number of advantages. For example, the present invention can quickly remove high levels of both fixed and smearable contaminants while minimizing airborne entrainment of the contaminants. The gel-like material captures and entrains the contaminates as they are removed from the surface. It is not be labor intensive and controls decontamination personnel exposure to radioactive materials. It can treat the surfaces in relatively short time periods and work well for large stationary surfaces, regardless of orientation due to the gel-like consistency of the material. It can use nontoxic and nonhazardous components, which can not only provide higher levels of personnel safety but also result in substantial cost savings. It achieves a magenta color when applied and a yellow color when cured, which are consistent with color codings for radioactively contaminated materials. The gel-like material can be left in place as a protective barrier to prevent recontamination of the surface. When removed, the cured gel-like material contains the radioactive materials and is in a form, namely radioactively contaminated plastics, that is already handled and familiar to current decontamination operations personnel. The decontamination system of the present invention can be compact, portable, easy to deploy, and placed in hot storage when not in use. It can minimize or eliminate entirely dangerous off-gases, making it suitable for use in tight quarters and confined spaces with limited egress, such as under gloveboxes, inside tanks and vessels, or in overhead ceiling spaces and pipe chases.

Problems solved by technology

Mechanical methods typically require surface abrasion to remove radioactive materials.

Mechanical decontamination methods can have drawbacks.

Although they can remove both fixed and smearable contaminants, removed radioactive material is typically dispersed into the surrounding atmosphere, not only presenting a significant health hazard to decontamination personnel but also spreading to and contaminating other areas.

Many of the mechanical methods are labor intensive, increasing both the cost of decontamination and decontamination personnel exposure time to radioactive materials.

The complexity of many surface contours and shapes often renders decontamination by mechanical means difficult or impractical.

They can require long treatment times to adequately decontaminate a surface because of low ion exchange rates and the need to apply chemical solutions at elevated temperatures, increasing the complexity and cost of the decontamination system.

Although electro-chemical stripping works well for objects that are fully immersed in an electrolyte bath, it does not work well for stationary surfaces or objects too large for full immersion in the bath.

When applied to a surface, the liquid electrolyte, under the force of gravity, typically runs down the surface and becomes an uncontrolled carrier of the radioactive materials to other locations.

Moreover, electrolytes can endanger personnel through their use of hazardous chemicals.

Although strippable coatings are effective for smearable contaminants, they can have a very low removal rates for fixed contaminants.

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