Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/001—Decontamination of contaminated objects, apparatus, clothes, food; Preventing contamination thereof
  • G21F9/002—Decontamination of the surface of objects with chemical or electrochemical processes

Definitions

• the present invention relates to a method for decontaminating a surface of an object, in which a removable layer of a decontaminating and a layer-forming material is produced on the surface and the layer with the impurities contained therein is then removed from the surface.
• the task often arises of cleaning the surface of radioactive or chemically contaminated objects (“decontaminate”).
• the objects to be decontaminated can be as diverse as superficially highly radioactive metallic structures from nuclear reactors and a weakly contaminated work table from a tritium laboratory.
• Decontamination processes have proven to be particularly expedient in which a strippable layer is formed on the surface to be decontaminated.
• a strippable layer is formed on the surface to be decontaminated.
• Such a method is known from DD-A-81048, in which a viscous mixture of decontaminating and film-forming material is applied to the surface to be decontaminated, which mixture contains formaldehyde and ammonium rhodanide for decontamination and polyvinyl alcohol as film former.
• Complexing agents, detergents and / or organic acids can be added to the solution for decontamination enhancement.
• EP-A-47 857 also discloses a process for the decontamination of radioactive contaminated surfaces, in which a pickling paste is applied to the surfaces to be decontaminated, which contains a pickling agent, a wetting agent, a filler and an aqueous, film-forming, agent-resistant plastic dispersion.
• the mordant can contain a mixture of nitric acid, hydrochloric acid and hydrofluoric acid or concentrated hydrochloric acid with the addition of KJ or phosphoric acid with zinc oxide and sodium nitrite.
• Aqueous copolymer dispersion of vinyl acetate, ethylene and vinyl chloride and copolymer dispersions of methacrylic acid esters are used as the film-forming component.
• the present invention avoids this disadvantage in that only the decontaminating material is first applied to the surface and allowed to act, and only then is the layer-forming material applied in such a way that it absorbs the decontaminating material before it solidifies into the removable layer.
• the decontaminating material or mordant can be left to act for as long as desired and the materials which can be used are also freer, since decontaminating materials which are intrinsically difficult to use with film formers can be modified before the film former is applied so that a good tolerance is guaranteed.
• the method can also be easily adapted to different surfaces and / or contaminations and / or degrees of contamination.
• a material is first applied to the contaminated surface in several steps, which can remove the contaminants from the surface and, if desired, attack the surface and dissolve it on the surface. Then a layer-forming material (film former) is applied, which is able to absorb the previously applied decontaminating material with the impurities contained therein and then to solidify into a coherent solid body.
• film former a layer-forming material
• the solid body thus preferably has the shape of a coherent, flexible, film-like structure which can be easily removed from the cleaned surface.
• the process can easily be repeated with the same or a modified material system.
• thixotropic materials such as amorphous silica (Si0 2 ) can be prevented that the pickling mixture of vertical walls u. The like. runs down before it causes the film formation by adding resin or another kenden material is solidified to the peelable film.
• a second step which can be timed to the degree and type of contamination, etc., then an aggressive, in particular an inorganic pickling agent is applied, if necessary with the addition of the gel or thickening agent in order to run away, drip off or the like . to prevent.
• a further component is applied which, alone or in cooperation with components of the previously applied layer (s), leads to the formation of a coherent, elastic layer or film.
• the constituents, in particular matrix constituents, of the material applied in the first and second process step can simply be incorporated into the film-forming material applied in this process step or can react with this material by coagulation, precipitation or hardening.
• the film formed which contains all constituents, including the contaminants removed from the surface, can be removed, e.g. B. be deducted.
• Effective decontamination agents for radioactively contaminated metallic surfaces should dissolve the radioactive coating and remove it from the system: furthermore, they should not be too corrosive to the surfaces; The same applies of course to chemical contaminants.
• Glasses and organic surfaces can have ionizable acidic groups that interact with strong cationic contaminants like ion exchangers. This contamination can then be removed by complexing agents.
• Acrylic glass, PTFE, PE and rubber can be treated with mixtures of 20% HN0 3 and 3% HF or complexing agents with detergents.
• halogens in particular chlorides and especially free chlorine, should be avoided if possible for reasons of corrosion.
• organic solvents such as ketones and hydrocarbons, especially halogenated hydrocarbons, be used in order not to put additional strain on the exhaust air carbon filters for iodine retention, which are normally present in radioactive waste disposal plants.
• Alcohols including higher ones, such as butyl alcohol, can generally be used.
• surfactants or detergents and relatively weak pickling chemicals are preferably added.
• the detergents cause degreasing of the surfaces and the weak, e.g. B. organic reagents such as oxalic acid, citric acid or lactic acid cause a first surface attack, which improves the adhesion necessary for the further film build-up.
• more aggressive pickling chemicals can then be applied, e.g. B. phosphoric acid with additives to inhibitors and complexing agents, optionally together with gels and thickeners and / or a component of the layer-forming material.
• the matrix e.g. B. by application of curable resins, such as urea, melamine and phenolic resins or by a second component that reacts with a previously applied component to form a layer, to form the “peelable film”.
• curable resins such as urea, melamine and phenolic resins
• a second component that reacts with a previously applied component to form a layer
• the embedded aqueous components and organic components ensure that the films remain elastic and flexible so that they come together after a corresponding «curing time» can be peeled off without leaving any sticky or dried layers on the surface due to embrittlement or drying out.
• the formation of the film can also be achieved by adding salts (borax, sulfates or carbonates), since these act gelling or even precipitating.
• Vinnapas dispersions copolymers of vinyl acetate and higher fatty acid vinyl esters

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Food Science & Technology (AREA)
• Electrochemistry (AREA)
• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Treatments Of Macromolecular Shaped Articles (AREA)
• Detergent Compositions (AREA)
• Details Or Accessories Of Spraying Plant Or Apparatus (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)
• Catching Or Destruction (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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• 1984
  • 1984-12-21 DE DE3446931A patent/DE3446931C2/de not_active Expired
• 1985
  • 1985-12-20 AT AT85116401T patent/ATE30804T1/de not_active IP Right Cessation
  • 1985-12-20 DE DE8585116401T patent/DE3560971D1/de not_active Expired
  • 1985-12-20 EP EP85116401A patent/EP0185393B1/de not_active Expired

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