Decontamination of concrete

See J.P. Woodyard and E.M. Zoratto, "State-of-the-Art Technology for PCB Decontamination of Concrete," in this book. 

Decontamination of building structures and equipment containing polychlorinated biphenyls is rapidly becoming a major concern to environmental managers in industry and government. The most costly stumbling block to this type of decontamination and the focus of more technical attention than any other aspect of building decontamination is the decontamination of concrete. 

Concern for long-term environmental damage from PCB is most often associated with former disposal and spill sites rather than concrete contamination. Since PCB contained in or on concrete is generally considered even less mobile than when contained in soils or water, PCB in concrete is not considered as great an environmental risk. PCB decontamination of concrete is therefore rarely driven by broad-based environmental concerns. 

The technology for PCB decontamination of concrete includes a wide variety of techniques with specific applications in industry. Each decontamination project typically involves several different depths of PCB contamination and a variety of concrete ages and conditions. 

The Decontamination Report provides an overall strategy for removing hazardous materials from the MDB, SWMUs, and AOls. A contamination investigation (RFI), yet to be completed, will provide the detailed characterization data to support closure activities. The characterizations will be based in part on analysis of concrete core borings taken from selected locations. 

The MDB is a two-story, steel-framed building with thick, reinforced-concrete floors and most interior walls made of concrete and foam-core sandwich panels. Explosion containment rooms have 2-foot-thick reinforced concrete floors, walls, and ceilings. Because concrete is a porous material capable of absorbing agent, all concrete surfaces in the JACADS process areas were sealed with an epoxy coating. A total of 134,153 square feet of concrete will require decontamination (U.S. Army, 1999d). 

CORPEX Technologies, Inc., offers CORPEX technology for the decontamination of undesirable and toxic ions or radionuclides from contaminated surfaces and coatings. The vendor states that the process can operate as either a batch or semicontinuous process. The commercially available CORPEX technology uses patented, innovative chelation chemicals to control and recover radioactive and other types of hazardous metal ions from soils, concrete, steel, and other materials. 

The technology is commercially available for the decontamination of soil and porous concrete but is still being developed for the decontamination of water. 

Based on 1996 testing of the ELECTROSORB process for the U.S. Department of Energy (DOE), the vendor estimates the cost of concrete decontamination to be 4.91/ft. Costs square foot are broken down in the following manner disposal costs 2.51, capital costs 1.15, chemical costs 0.67, labor costs 0.52, vaporization energy 0,033, and electrical costs 0.03. This estimate is based on cleanup of 600 ft and involves the following components ... 

As part of the evaluation, a cost estimate of the centrifugal shot blast technology was prepared based on the demonstrated decontamination of 800 ft of concrete. The vendor provided personnel and equipment for which timed and measured activities were recorded to determine achievable production rates. These data included activity duration, work crew composition,... 

Smooth and Coat Concrete SurfacRc - These are preventive and protective measures against the radioactive contamination of concrete surfaces and thus decrease the quantity of radwaste associated with the decontamination of such surfaces. 

Besides the metallic structures of the circuits and components, nuclear power plants contain huge masses of concrete, a small fraction of which is activated and/ or contaminated. In order to keep the resulting waste volumes as small as possible, the fraction which contains radionuclides has to be separated during dismantling from the non-radioactive bulk of the material the techniques used for this will not be discussed in what follows. Likewise, decontamination of building walls and surfaces will not be treated here. 

Given a particular type of concrete contamination and an associated driving force for decontamination, one or more methods must be chosen to meet the standard. The selection of a technique is based on several factors including production rate, effectiveness, potential for cross contamination, potential for enhanced penetration, waste disposal or treatment requirements and cost. 

The type of PCB contamination of concrete that is most frequently encountered and most difficult to treat is just below the surface, resulting either from short-term spill contact or grinding of dry deposits through tracking. PCB has been shown, however, to penetrate concrete to much greater depths than common sense would indicate, through capillary action or other physical mechanisms. Decontamination of floors in particular sometimes shows PCB penetration of 0.5 to 2.0 inches for even small spills of limited contact time. 

Product ion/removal rates for some commonly used floor and wall concrete removal techniques are shown in Table 4. In general, the most productive techniques are also the crudest and generate the most waste Application of concrete decontamination in a relatively sensitive environment is easier to control but will typically require much slower production equipment such as that used in shot blasting. For heavy industrial applications with large floor spaces and limited impediments to movement, grinding or high pressure water techniques can be employed (Woodyard, 1985). 

The extent of concrete contamination is not well defined in most circumstances and never will be completely understood because of its very nature. Selection of the right decontamination technique must be accompanied by the know-how required to implement it so that waste and cross contamination may be controlled while effectiveness and production are maximized. 

Barbier, M. M. and C. V. Chester, May 1980, Decontamination of Large Horizontal Surfaces Outdoors, presented at the USDOE Concrete Decontamination Workshop, Richland, Washington. 

N LULS Received spent radioactive decontamination liquid from 116-H-2 facility and 107-N facility for transfer to railway tank farms Curbed pad with prefabricated metal building. Before 1976 the site consisted of concrete pad. 

The shot blaster has been developed to decontaminate, semi-automatic. lly, the walls of celts amounting to about 3000 square metres of concrete and several hundred square metres of recovery floor in stainless steel. 

Decontamination for rector decommissioning System decontamination Concrete surface removal Decontamination of disassembled components... 

Table III lists the major milestones of the JPDR dismantling activities. In parallel with dismantling the biological shield concrete, decontamination of the building inner surface has been started since the end of 1992. Various techniques such as steel blasting, and scabbier are applied to the decontamination work. After confirming that there is no...

Decontamination Technologies, 20 Adjacent Sources of Contamination, 20 Concrete, 20... 

The TechXtract process was used at a warehouse where PCB contamination resulted from the storage of electrical transformers. The decontamination costs for the concrete floor at this... 

Pentagone is an aqueous-based surface decontamination product developed for the cleanup of pentachlorophenols, creosote, petroleum hydrocarbons, chlorinated hydrocarbons, polynuclear aromatic hydrocarbons, and selected pesticide and herbicide spills. It can be used on concrete, asphalt, or metal and is capable of being applied as a foam, allowing treatment of overhead, vertical, and horizontal surfaces. It has been commercially available since 1993 and has been used in multiple applications. 

ISOTRON Corporation s electrokinetic decontamination process is a patented, in situ process for the removal of contaminants from soil, groundwater, and porous concrete. The technology applies a low-intensity direct current (DC) across electrode pairs to facilitate electromigration and electro-osmosis of contaminants. The process works primarily on highly soluble ionized inorganics including alkah metals, chlorides, nitrates, and phosphates. Heavy metals such as lead, mercury, cadmium, and chromium have also responded favorably. 

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