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
  • G21F9/28—Treating solids
  • G21F9/30—Processing
• • 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 invention relates to a method for decontaminating a part having contaminated particles on its surface, as well as a decontamination product intended to be used for the implementation of this method.
• the method and the decontamination product are particularly intended for the treatment of fixed radioactive contamination, that is to say when the radioactive particles are either embedded in the room or chemically bonded to the surface of the room. To move particles from the surface of the workpiece to the decontamination product, it is then necessary to erode the workpiece.
• the method and the decontamination product can also be used for the treatment of unfixed radioactive contamination, ie when the particles are simply deposited on the surface of the part and it is not no need to erode the room to reach them.
• the decontamination of the room corresponds to the reduction of the number of radioactive particles present on the surface of the room, up to a predetermined threshold, which may vary according to the needs and wishes of the user of the room.
• the parts to be decontaminated may be fluid lines, walls, floors, ceilings, tanks, swimming pools, or other objects.
• Cerium (IV) makes it possible to erode metal alloys, especially steel or stainless steel, constituent materials of many parts - or their coating - in the nuclear field.
• FR-A-2,710,182 discloses a method of decontamination with an acidic aqueous solution of cerium (IV) having a pH of less than 3.
• a first problem posed by the processes of the prior art concerns the form in which the decontamination product is applied to the part.
• cerium (IV) solution is carried out most of the time in the liquid phase (washing processes, dipping, or high-pressure jet spraying), which has the following drawbacks: formation of a large amount of quantity of contaminated effluent, which increases the cost of reprocessing the effluents generated, reduced contact time with the part and limited affinity between contaminated particles and the solution, resulting in insufficient decontamination.
• Processes are also known where the product comprising cerium (IV) is applied in gel form to the workpiece.
• the contact time between the decontamination product and the part is then greater than in the liquid phase, and the decontamination more effective.
• composition of the gels is complex, and their cost price is relatively high.
• the foam phase is particularly advantageous. Indeed, the foams containing more gas than liquid, thus reducing the volumes of reagents and effluents generated. In addition, the contact time between the foam and the part being larger than with a liquid, the decontamination is considerably improved.
• Ce 4+ ion is likely to oxidize a very large number of organic functions, including those of the molecules. surfactants, foam generators.
• the principal organic functions oxidized by Ce 4+ are: carboxylic acids and amino acids, alcohols and phenols, aldehydes and ketones, esters, amides, and multi-link hydrocarbons.
• the maximum erosion stress imposed by EDF on certain sensitive installations is 3 ⁇ m over the lifetime of the installation, ie 20 years, decontamination being planned by stopping the installation.
• erosion should not exceed 0.3 ⁇ m per decontamination operation.
• cerium (IV) used in cerium (III).
• cerium (IV) is very reactive and difficult to treat, it is not desirable that the effluents generated by the decontamination contain.
• the invention aims to provide a method for treating the fixed contamination more effectively and less restrictive than in the prior art, in particular using a product comprising Cerium (IV) in the foam phase.
• the first solution - comprising cerium (IV) - and the second solution - comprising the surfactant (s), forming foaming agent (s) - are packaged separately, for example in two separate containers, and are not mixed only at the moment of their use (possibly with water).
• cerium (IV) does not have time to oxidize a large amount of surfactant, and it is possible to form a foam having the required qualities (stability, bubble size, quality of hanging on the walls , on ceilings, etc.).
• the feeding of the foam generating device, the formation of foam and the application on the part of the formed foam are successive steps carried out continuously.
• the invention thus makes it possible to obtain, from a decontamination product comprising cerium (IV), a stable foam for a time sufficient to allow the application of this foam to the part to be treated.
• Another advantage of the invention is to reduce the erosion of the treated part.
• the surfactant continues to react with cerium (IV), thereby decreasing the amount of cerium (IV) available for attacking the part on which the foam is applied.
• the method makes it possible to achieve a controlled attack of the material constituting the part to be decontaminated, which is less than the limit set by the user (for example 0.05 to 0.5 ⁇ m).
• This limit value is sufficient to reach the contaminated particles embedded in the surface irregularities of the part, so as to ensure the passage of said particles to the decontamination product.
• the method according to the invention thus makes it possible to reduce the erosion of the treated parts without impairing the quality of the decontamination.
• the mass of cerium (IV) in the mixture is between 0.5 and 5 times the mass of the surfactant or surfactants.
• cerium (IV) After decontamination, the cerium (IV) that has not been consumed for the decontamination and the surfactant react.
• the first consequence is that the concentration of cerium (IV) in the effluents is extremely low (the surfactant being in excess), in accordance with what is generally desired by the users.
• the second consequence is that the concentration of surfactant in the effluents is relatively low (the surfactant being present in as small a quantity as possible in the mixture feeding the foam generating device). As a result, the effluents foam little, and can thus be easily reprocessed in an evaporator.
• HLB hydrophilic - lipophilic balance
• the second solution may further comprise between 1 and 15% of a third nonionic surfactant whose HLB, measured at room temperature in aqueous medium, is between 13 and 15.
• the first surfactant is a polyglucoside whose alkyl chain comprises between 6 and 10 carbon atoms.
• the second surfactant is, for example, an ethoxylated fatty alcohol containing between 8 and 12 carbon atoms and between 5 and 9 average ethylene oxide groups.
• the third surfactant may be a polyglucoside whose alkyl chain comprises between 8 and 12 carbon atoms, said third surfactant being different from the first surfactant.
• the foam generation device may comprise firstly a liquid introduction nozzle and secondly a Venturi stage comprising a convergent coaxial with said nozzle, a gas inlet opening into the convergent, and a divergent communicating with a nozzle. mixing chamber, the geometry of the device being defined to create a cavitation phenomenon at the outlet of the Venturi stage.
• the first and second solutions in liquid form are introduced through the nozzle to the Venturi stage, causing Venturi gas suction and foam formation in the divergent and mixing chamber.
• said part is rinsed with water.
• the decontamination process according to the invention consists in applying to a part, in the form of foam, a product comprising two decontamination solutions.
• component % mass provider nitric acid (concentration: 52.5%) 20 FORGE Cerium nitrate ammonium 14 RHONE POULENC water 66
• cerium (IV) is slowly added, for example in the form of cerium nitrate ammonium, and then stirred for about 10 minutes.
• the containers containing the nitric acid and the cerium nitrate ammonium are then rinsed with the remainder of demineralised water, the liquid obtained being then poured into the tank.
• the first solution is obtained. This is placed in a first container, preferably opaque.
• ceric salts are their slow, but not insignificant, photochemical decomposition, by their reaction with water, according to the following reaction: 4 This 4+ + 2H 2 O ⁇ 4 This 3+ + 4 H + + O 2
• the conditioning of the first solution in opaque containers thus makes it possible to limit the conversion of the Ce 4+ ions into Ce 3+ ions, and thus to ensure that the first solution has a satisfactory decontamination efficiency.
• the nitric acid concentration in the fresh product is 10.5% by weight.
• “Fresh product” means the solution manufactured according to the method described above, for example packaged in drums, and ready to be used (diluted, heated, pressurized for the formation of a foam, etc.) for decontamination of a room.
• This first solution can be used alone, in the liquid phase, for the treatment of fixed and non-fixed decontamination.
• the second solution is an aqueous formulation of biodegradable surfactants, at neutral pH.
• the second solution can also be used alone, for the treatment of non-fixed contamination, on all materials (given its neutral pH).
• the solution also comprises water, for example demineralised water.
• water for example demineralised water.
• component % mass trade name of the component provider polyglucoside (8 carbon atoms) 18 SIMULSOL SL8 SEPPIC ethoxylated fatty alcohol (10 carbon atoms, 7 ethylene oxide groups) 7.2 SYNPERONIC 10/7 RIGHT HERE polyglucoside (10 carbon atoms) 3 SIMULSOL SL10 SEPPIC water 71.8
• the second solution may also comprise dipropylene glycol (between 1 and 15% by weight).
• This component miscible with water, solubilizes the fatty substances (grease, oil present on the surface of the part to be decontaminated), inside the micelles formed by the surfactants.
• the second decontamination solution is then able to treat the contamination in the presence of fatty substances.
• the 10-carbon polyglucoside is prepared. If the product is pasty, three quarters of the demineralized water is poured at about 30 ° C. If the product is liquid, pour three-quarters of the demineralized water at room temperature.
• the 10-carbon polyglucoside thus prepared is poured into a tank and then stirred for about 10 minutes or 20 minutes until dissolution is complete.
• the solution obtained is then translucent to light yellow.
• the totality of the polyglucoside is then added to 8 carbon atoms and then stirred for about 10 minutes.
• the entire ethoxylated fatty alcohol is then added and stirred again for about 5 minutes.
• the various containers containing the components are rinsed with the remainder of demineralised water, the liquid obtained is then poured into the tank. After stirring for about 5 minutes, the second solution is obtained.
• the first and second solutions are biodegradable and meet the requirements for products used in power plants.
• the solutions are optimized so that the concentration of organic and inorganic matter is as low as possible, and less than 5%, or even 2%, in the effluents, in order to reduce the cost and facilitate the treatment of these substances. effluents.
• the first and second solutions are intended to be mixed and brought into contact with a part having on its surface contaminated particles, to allow the decontamination of said part by ensuring the passage of contaminated particles from the surface of the part to the mixture of solutions. .
• the invention consists in applying to the part to be decontaminated a mixture of the first and second solutions in the form of foam.
• each of the two solutions can be applied alone to the part by liquid phase spraying. You can also immerse the part in the first or the second liquid solution.
• a first container, containing the first decontamination solution, and a second container, containing the second decontamination solution, are connected, separately, to the inlet of a foam generating device, for example by means of pipes and pumps. dosing.
• a third vessel including water, for example deionized water, is also connected to the inlet of the foam generating device.
• the foam generation device comprises on the one hand a liquid introduction nozzle and on the other hand a Venturi stage comprising a convergent coaxial with said nozzle, a gas inlet opening into the convergent, and a divergent communicating with a chamber mixture.
• the geometry of the device is defined to create a cavitation phenomenon at the outlet of the Venturi stage.
• the first solution, the second solution and the water are brought separately, in the desired proportions, to the foam generating device.
• the resulting mixture is immediately introduced into the nozzle and converges the Venturi stage.
• the mixture comprises 30% of the first solution, 5% the second solution and the balance of water (normal cycle).
• the mixture comprises 50% of the first solution, 5% of the second solution and the balance of water (advanced cycle).
• the proportions of the first and second solutions in the mixture are chosen in particular according to the constituent material of the part to be decontaminated, the degree of contamination, and the desired degree of decontamination.
• the table above indicates the concentrations of organic and / or inorganic matter in the mixture, which are less than 35%.
• the introduction of the liquid mixture into the convergent causes the suction of gas, for example air, by Venturi effect.
• the first and second water - air solution mixture is then displaced to the diverging and the mixing chamber, and forms a foam.
• foam is possible insofar as the surfactant, packaged separately from cerium (IV), could not be oxidized by the latter during the limited time when these two components were mixed.
• the foam is then transported, via hoses, from the device for generating this foam to the part to be decontaminated, then projected, without delay, on said part using specific tools.
• Cerium (IV) is reduced to Cerium (III).
• the cerium (IV) salts are colored (the cerium nitrate ammonium is orange, but other compounds can have a light yellow or yellow color), while the cerium (III) is colorless and not very acidic.
• the transformation of cerium (IV) into cerium (III) can be observed very easily by the change of color.
• Cerium (IV) is also reduced to cerium (III) by the action of the surfactant. Thus, the amount of cerium (IV) is decreased, and the erosion of the treated part less.
• One or more foam applications may be necessary depending on the degree of decontamination of the predetermined part by the user. Finally, after the action of the foam, it is rinsed with water, which allows to evacuate the contaminated particles with the decontamination solution.
• the effluents generated by this solution can be treated on conventional installations in a nuclear medium after a simple neutralization with an alkaline reagent to obtain a neutral pH.
• the concentration of organic and inorganic matter in the effluents is less than 5%, or even 2%.
• the effluents can contain 95 to 98% water.
• the quality of the foam obtained from the mixture makes it possible to generate the foam at a distance from the workpiece, to transport it for several tens of meters and to project it efficiently against the workpiece without the foam being degraded, in terms of composition, size of the bubbles, etc., as long as the foam is generated and used very quickly once the two solutions have been mixed.
• An operator can work remotely from the room contaminated, which considerably reduces the dose of radioactivity it receives during this decontamination.
• the process and the product according to the invention are able to comply with the new constraints imposed in the field of radioactive decontamination (quality of the foam making it possible to obtain a high level of decontamination, reduction of the dose of radioactivity received by the operator during decontamination operations ).

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• Engineering & Computer Science (AREA)
• High Energy & Nuclear Physics (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Food Science & Technology (AREA)
• Chemical & Material Sciences (AREA)
• Electrochemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Detergent Compositions (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Apparatus For Disinfection Or Sterilisation (AREA)

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• 2003
  • 2003-03-28 FR FR0303884A patent/FR2853129B1/fr not_active Expired - Fee Related
• 2004
  • 2004-03-29 DE DE602004026135T patent/DE602004026135D1/de not_active Expired - Lifetime
  • 2004-03-29 ES ES04290825T patent/ES2343459T3/es not_active Expired - Lifetime
  • 2004-03-29 EP EP04290825A patent/EP1469482B1/fr not_active Expired - Lifetime
  • 2004-03-29 AT AT04290825T patent/ATE462188T1/de not_active IP Right Cessation

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