CHEAP STRIPPABLE POLYMER FILM TO DECONTAMINATE OR TO PREVENT CONTAMINATION

The use of a rubber film directly formed on a metallic surface from an aqueous emulsion is able to protect it very effectively against contamination by cesium in water solution. This protection is effective for a long period of time. The film remains 100 % waterproof and impermeable in all environmental conditions (humidity, irradiation). When used as a decontamination process, the implementation of this film is able to remove about 90% of the surface contamination. This film can be easily recycled, and the different products can be separated or treated. The mechanical properties of this film (adhesion, extension, resistance) make it strippable. However, the composition of the rubber emulsions has also been optimized to comply with other requirements, such as removing the film without contact by applying high pressure hot water in areas where human intervention is not permitted. BACKGROUND A decrease in the efficiency of some decontamination processes may occur after several implementations on the same surface, as recontamination between each implementation can occur. In some situations, achieving decontamination to acceptable levels can become difficult. The origin of this problem has been highlighted and solutions have been found. In fact, by thoroughly cleaning the surface, the decontamination process may lead to an increase of the adhesion of subsequent contaminants, thus making them much more difficult to remove. In concrete terms, some chemical functional groups, such as hydroxides make possible the chemical sorption of metal ions. Simply removing grease or natural pollutants from the surface allows direct contact between the contaminants and these reactive sites, increasing adhesion. If the cleaning process is badly suited to the material to be decontaminated, a modification of the chemical composition of the surface can occur, possibly increasing the density of reactive sites, making the problem worse. Predicting the evolution of the surface chemical properties with time is a challenge. Prevention of surface contamination appears to be a wiser approach. The principle is to prevent strong adhesion of the contaminants by masking the reactive groups likely to chemically bind the contaminants to the surface. With this aim in view, different methods of surface treatments offering such barrier effects have been developed at the French atomic Energy Commission (CEA). One possibility is the use of a removable protective polymer film, which can be used also for decontamination purposes. The other possibility is the vapour phase deposition of inert mineral layers on the surface. In this paper, we will describe both the studies and results that lead us to this prevention approach to the surface contamination problem, and the improvements obtained in terms of decontamination efficiency with this new approach. We demonstrated that by thoroughly cleaning the surface, the decontamination processes increase the adhesion of subsequent contaminants. In fact, the first decontamination is often efficient because it simply removes the surface pollutants (like grease) in which the radioactive contaminants are embedded. Removing pollutants (like this grease) automatically removes the contamination. Therefore, subsequent contaminants will be in direct contact with the material surface. This surface can't be removed and mustn't be damaged. The decontamination process must be able to reduce the adhesion of the contaminants to the surface. This is more difficult to achieve and demands