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
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D17/00—Detergent materials or soaps characterised by their shape or physical properties
  • C11D17/0008—Detergent materials or soaps characterised by their shape or physical properties aqueous liquid non soap compositions
  • C11D17/003—Colloidal solutions, e.g. gels; Thixotropic solutions or pastes
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D3/00—Other compounding ingredients of detergent compositions covered in group C11D1/00
  • C11D3/02—Inorganic compounds ; Elemental compounds
  • C11D3/04—Water-soluble compounds
  • C11D3/042—Acids
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D3/00—Other compounding ingredients of detergent compositions covered in group C11D1/00
  • C11D3/02—Inorganic compounds ; Elemental compounds
  • C11D3/04—Water-soluble compounds
  • C11D3/044—Hydroxides or bases
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D3/00—Other compounding ingredients of detergent compositions covered in group C11D1/00
  • C11D3/02—Inorganic compounds ; Elemental compounds
  • C11D3/12—Water-insoluble compounds
  • C11D3/1213—Oxides or hydroxides, e.g. Al2O3, TiO2, CaO or Ca(OH)2
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D3/00—Other compounding ingredients of detergent compositions covered in group C11D1/00
  • C11D3/02—Inorganic compounds ; Elemental compounds
  • C11D3/12—Water-insoluble compounds
  • C11D3/124—Silicon containing, e.g. silica, silex, quartz or glass beads
  • C11D3/1246—Silicates, e.g. diatomaceous earth
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D3/00—Other compounding ingredients of detergent compositions covered in group C11D1/00
  • C11D3/39—Organic or inorganic per-compounds
  • C11D3/3947—Liquid compositions

Definitions

• the present invention relates to a suction gel that can be used for the decontamination of surfaces, as well as to the use of this gel.
• the decontamination can be for example a radioactive decontamination.
• the gel can be used on all kinds of surfaces to be treated, such as metal surfaces, plastic surfaces, vitreous material surfaces and / or porous material surfaces (eg concrete surfaces).
• the gels of the prior art do not dry or in several tens of hours and must all be removed after a few hours by rinsing with water.
• the rinsing also makes it possible to interrupt the action of the gel on the wall and to control the duration of action of the gel.
• Rinsing has the disadvantage of generating liquid effluents of the order of 10 1 of water per kg of gel used. These decontamination effluents for radioactive decontamination must be treated in existing nuclear material processing facilities. This therefore requires in-depth studies on the management of these effluents and their impact on facilities treatment circuits. In addition such gels that must be rinsed can not be used to treat installation surfaces that must not be flooded.
• This gel consists of a colloidal solution comprising from 5 to 15% by weight of silica relative to the weight of the gel, from 0.5 to 4 mol / l of an inorganic acid or a mixture of inorganic acids, and, optionally, from 0.05 to 1 mol / l of an oxidizing agent having a normal redox potential E 0 greater than 1.4 V in a strong acid medium or the reduced form of this oxidizing agent.
• the surface treatment method described in this document comprises an application of the gel to the surface to be treated, a maintenance of the gel on this surface until drying, and an elimination of dry gel residues by suction or brushing.
• the present invention aims to further improve the gel and the method described in the latter document.
• the inventors have noticed that the gel described in this document has a certain number of drawbacks: its viscosity and its drying rate are not always well controlled, its spraying is not always easy, the fracturing of the gel on the surface is not good controlled (dry residues of the gel too large), and some dry residues of the gel adhere strongly to the support and are difficult to suck or brush.
• the present invention achieves the aforementioned objective by means of a gel consisting of a colloidal solution, characterized in that it comprises: from 5 to 25% of an inorganic viscosifying agent by weight relative to total weight of the gel, from 0.01 to 0.2% of a surfactant by weight relative to the total weight of the gel, and particularly preferably a surfactant in an amount strictly less than 0.1% by weight per relative to the total weight of the gel, from 0.5 to 7 mol, per liter of gel, of an acid or of an inorganic base, and optionally from 0.05 to 1 mol, per liter of gel, of a oxidizing agent having a normal redox potential E 0 greater than 1.4 V in a strong acidic medium or the reduced form of this oxidizing agent, the balance being water.
• the gel of the present invention is aqueous, it can be acidic or basic, oxidizing or reducing. It can be used for the radioactive decontamination of surfaces and leads, after total drying in a few hours, generally from 2 to 72 hours, at a temperature of between 15 ° C. and 30 ° C. and a relative humidity of between 20 and 70%. to a solid dry residue which has an excellent ability to detach from the support.
• This gel is called "suction gel".
• the drying time can be further reduced, for example by means of ventilation, for example air. With a ventilation of 230 m 3 / hour, the drying time can be reduced for example to 48 hours or less, and with a ventilation of 900 m 3 / hour, the drying time can be reduced for example to 24 hours or less .
• viscosifying agent is meant a viscosifying agent or a mixture of viscosifying agents.
• the viscosity agent is preferably inorganic. It may be for example alumina or silica.
• this silica may be hydrophilic or hydrophobic. In addition, it can be acidic or basic. It may be for example silica Tixosil 73 (trademark) marketed by Rhodia.
• the silica is at a concentration of 5 to 25% by weight of the gel to ensure even more effectively drying of the gel at a temperature of 20 ° C. to 30 ° C. and a relative humidity of 20 to 20 ° C. 70% on average in 2 to 72 hours.
• acidic silicas which may be used, mention may be made, by way of example, of the fumed silicas "Cab-O-SiI” M5, H5 or EH5 (trademarks) marketed by CABOT and the fumed silicas sold by the company Degussa under the name 'AEROSIL appellation (trademark).
• fumed silicas silica AEROSIL (trademark) is preferred which offers the properties maximum viscosities for a minimum mineral load.
• the silica used may also be a so-called precipitated silica obtained by wet process by mixing a solution of sodium silicate and an acid.
• Preferred precipitated silicas are marketed as SIPERNAT 22 LS and FK 310 (trade marks).
• the viscosing agent may be a mixture of a silica mentioned above and a fumed silica.
• a mixture of pyrogenous and precipitated silicas represents from 5 to 25% by weight of the gel. This makes it possible to ensure drying of the gel at a temperature of 20 ° C. at 30 ° C. and a relative humidity of 20 to 70% on average in 2 to 72 hours.
• a precipitated silica for example FK 310 (trademark)
• AEROSIL 380 a precipitated silica
• the viscosing agent is based on alumina (Al 2 O 3 ), it can be obtained for example by hydrolysis at high temperature.
• alumina Al 2 O 3
• the product Alumina C sold by Degussa.
• the alumina represents from 10 to 25% by weight of the gel. Indeed, these concentrations make it possible to ensure even more efficient drying of the gel at a temperature of 20 ° C. to 30 ° C. and a relative humidity of 20 to 70% on average in 2 h 12 hours.
• a surfactant is meant a surfactant alone or a mixture of two or more surfactants.
• the gels described in document WO 03/008529 are added, in an original manner, a very small amount of a surfactant, or specific surfactant, of less than 2 g per kg of gel, generally ranging from from 0.01 to 0.2% by weight relative to the total weight of the gel.
• the amount of surfactant in the gel according to the invention is strictly less than 0.1% by weight relative to the total weight of the gel and, more particularly, this amount ranges from 0.01 to 0.1. % by weight relative to the total weight of the gel, the value 0.1% being not included.
• the values 0.2% and 0.1% are excluded from the ranges relating to surfactants in the context of the present invention.
• the surfactant may be a surfactant or a mixture of surfactants having one or more of the following properties: wetting, emulsifying, detergent.
• the surfactant (s) used may be advantageously chosen from the families of wetting surfactants, emulsifying surfactants and detergent surfactants. It may be a mixture of different surfactants belonging to one or more of these families.
• one or more surfactants (s) which are stable in the composition of the gel of the present invention will be chosen, in particular at the pH of the gel, which may be very acidic or very basic. Given although the present invention relates to gels, it is of course preferred to use one or more surfactants with no foaming agent (s).
• wetting surfactants that can be used in the present invention, mention may be made, for example, of alcohol alkoxylates, alkyl-aryl sulphonates, alkylphenol ethoxylates and block polymers based on ethylene oxide or propylene oxide (for example IFRALAN P8020). (Trade Mark)), light ethoxylated alcohols (e.g. MIRAVON B12DF (RHODIA) (Trade Mark)), ether phosphates, or a mixture thereof.
• the detergent surfactants that can be used in the present invention include, for example, alkanolamides or amine oxides (for example OXIDET DMC-LD (Kao Corporation) (trademark)), or a mixture thereof.
• Preferred surfactants are those whose trademarks are mentioned herein (disclosure of the invention and examples).
• WO 03/008529 and related to the use of a gel for the treatment of a surface, the addition of a surfactant
• a surfactant it is possible, unexpectedly, to increase the viscosity recovery of the gel, a favorable effect to prevent the gel from flowing on a wall (improvement of the rheological properties of the gel: see Example 1 below).
• This addition also unexpectedly allows better control of the drying rate of the gel, accelerating or retarding the drying kinetics (see Example 2 below). It also allows, unexpectedly, a control of the fracturing phenomenon at the surface of the gel during drying: the fracturing is more homogeneous and leads to an increased homogeneity of the size of the solid residues (see Example 3 below).
• the gel may comprise an inorganic acid or a mixture of inorganic acids.
• this acid or mixture is preferably present at a concentration of 1 to 4 moles per liter of gel.
• these concentrations advantageously make it possible to ensure that the gel is dried at a temperature of 20 ° C. at 30 ° C. and a relative humidity of 20 to 70% on average in 2 h 12 hours.
• the inorganic acid can be chosen for example from hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid or a mixture thereof.
• the viscosing agent is preferably silica or a mixture of silicas as defined above.
• the gel may comprise a mineral base or a mixture of mineral bases.
• the base is preferably present at a concentration of less than 2 mol / l of gel, preferably from 0.5 to 2 mol / l, more preferably from 1 to 2 mol / l, in order to advantageously provide a gel drying at a temperature of 20 ° C. to 30 ° C. and a relative humidity of 20 to 70% on average in 2 to 3 hours.
• the base may be chosen for example from sodium hydroxide, potassium hydroxide or mixtures thereof.
• the viscosing agent is preferably alumina.
• the gel of the invention may contain an oxidizing agent which has a normal oxidation-reduction potential greater than 1400 mV in a strong acidic medium, that is to say an oxidizing power greater than that of the permanganate.
• oxidizing agents may be Ce (IV), Co (III) and Ag (II).
• the concentration of oxidizing agent in the gel is preferably from 0.5 to 1 mol / l of gel.
• the oxidizing agents are preferably associated with a mineral acid, for example nitric acid, at a moderate concentration, that is to say less than 3 mol / l, and allowing rapid drying of the gel as defined above.
• Cerium is generally introduced in the form of electrogenerated cerium (IV) nitrate Ce (NO 3 ) 4 or hexanitrate cerium (NH 4 ) 2 Ce (NO 3 ) 6 .
• a typical example of an oxidizing decontamination gel according to the invention consists of a colloidal solution comprising, besides the surfactant in the concentrations of the invention, from 0.1 to 0.5 mol / l of Ce (NO 3 ) 4 or (NH 4) 2 Ce (NO 3) 6, from 0.5 to 2 mol / 1 of a strong acid, eg nitric acid, and 5 to 15% by weight of silica.
• the gels of the invention can easily be prepared at room temperature, for example by adding to a decontaminating aqueous solution of the prior art the mineral viscosity agent which preferably has a high specific surface area, for example greater than 100 m 2. / g, then the surfactant (s) in order to obtain a gel according to the present invention.
• the gel has a viscosity of at least 1 Pa.s and a recovery time of less than one second so that it can be applied to the surface to be decontaminated without sinking, remotely (for example at a distance of 1 to 5 m) or close (distance less than 1 m, preferably 50 to 80 cm).
• the present invention also relates to a process for decontaminating a surface, characterized in that it comprises at least one cycle comprising the following successive steps:
• a cycle comprises steps (a), (b) and (c), and several cycles can be repeated successively, until the desired decontamination is achieved.
• the process of the present invention is a radioactive decontamination method.
• the gel can be applied to the surface to be decontaminated, for example at a rate of 100 to 2000 g of gel per m 2 of surface, preferably 100 to 1000 g / m 2 . These are proportions allowing a good decontamination without unnecessary waste.
• the gel may be applied to the surface to be decontaminated by any means known to those skilled in the art. The most appropriate present means however seem to be a spray application, for example by spraying, or a brush application.
• the gel of the present invention To be applied to the surface by spraying, the gel of the present invention
• Colloidal solution can for example be conveyed by means of a low pressure pump, for example using a pressure of less than 7 ⁇ 10 5 Pa.
• the burst of the gel jet on the surface can be obtained for example by means of a jet nozzle or round jet.
• the distance between the pump and the nozzle may be any, for example from 1 to 50 m, for example 25 m.
• the short viscosity recovery time thanks to the gel composition of the present invention, allows the gel to adhere to the wall, even when sprayed.
• the gel drying time is from 2 to 72 hours thanks to the composition of the gel of the present invention and the aforementioned drying conditions.
• the dry and solid residues of the gel can be easily removed from the decontaminated surface, for example by brushing and / or by suction.
• the method of the invention may comprise a preliminary step of dedusting the surface to be decontaminated.
• the method of the invention may comprise an additional step of dedusting said surface to be decontaminated, followed by decontamination of the dusted plant by means of the method of the invention.
• the dedusting may for example consist of a preliminary cleaning of the surface to be decontaminated, for example by blowing or suction of dust, in order to remove unfixed solid contaminations.
• the decontamination method of the invention is applied so as to eliminate the contaminations fixed on the surface.
• the gel of the present invention dries completely after acting on the surface and easily detaches from the wall by suction or brushing.
• the method of the present invention is of particular interest in and relates to the decontamination of nuclear installations, for example ventilation ducts of nuclear installations.
• the method of the present invention is particularly applicable to the decontamination of metal surfaces, advantageously when they are important and this, both in the context of the periodic maintenance of existing installations, as during sanitation and / or dismantling of nuclear installations.
• the surfaces concerned are not necessarily horizontal, but may be inclined or even vertical.
• This method is applicable to any type of surface, in particular to metal surfaces, contaminated with grease, a very adherent oxide layer or in the mass or other radioactive contaminants or not.
• the gels according to the invention can be used for example for decontaminating tanks, ventilation ducts, storage pools, glove boxes, etc.
• treatment of the surface may be repeated several times (several cycles), successively, with the same gel or with different gels, preferably in accordance with the present invention.
• the drying of the gel is improved and leads to a phenomenon of homogeneous fracturing.
• the size of the dry residues is monodisperse and the ability of the residues to separate from the support is increased compared to the prior art gels.
• the inventors have noticed that the presence of surfactant (s) according to the present invention makes the gel sometimes more effective for surface treatment.
• the inventors have shown that the gels of the present invention can be more easily applied to the surface to be decontaminated by spraying or brushing, then after total drying in a few hours, more easily removed with the radioactivity they fixed by simple brushing or aspiration.
• FIG. 2 Rheogram of gels containing no surfactants (prior art) and gels containing surfactants according to the present invention: variation of the viscosity (V) as a function of time (s).
• FIG. 3 Influence of aging on the viscosity of the gel of the present invention: variation of the viscosity (V) as a function of time (s).
• Figure 4 Corrosion kinetics obtained on aluminum samples treated with acidic or basic gels containing or without a surfactant according to the present invention.
• Figure 5 photograph allowing a visual comparison of a gel according to the present invention (left), and a gel of the prior art, that is to say without surfactant (right).
• V represents the viscosity in Pa s
• T represents the time in seconds (s)
• Cor represents the observed corrosion in ⁇ m.
• Example 1 A reference gel comprising
• AEROSIL 8% by weight
• 0.1M HNO 3 and 1.5MH 3 PO 4 the conditions of use of the gel for drying are as follows: 22 0 C and 40% relative humidity.
• the viscosity limit is set at 100 mPa.s under high shear (700 s -1 ) to obtain a gel that does not flow on the wall, a viscosity greater than 1 Pa.s. under low shear (10s- 1 ) is required.
• the viscosity of the gels should preferably be in the white areas of the graph which guarantee an easy implementation of the gel.
• FIG. 2 shows the rheograms obtained for different acid gels containing different surfactants (CRAFOL AP56, SYNTHIONIC P8020 and DEHYQUART 5P (trademarks)) at 1 g kg -1 of active material and at only 8% silica.
• the gels studied are shown in this figure:
• the rheogram of an acid gel of the prior art, that is to say without surfactant, is also represented in this figure.
• the incorporation of a surfactant into the gel formulation makes it possible, surprisingly while decreasing the silica load, to reach the defined viscosity criteria.
• the viscosity of the gels with surfactants is less than 100 mPa.s under high shear and greater than 1 Pa. s under low shear.
• surfactants in the silica gels according to the present invention considerably improves their rheological behavior regardless of the electrical charge of the surfactant (1, 0 or -1). The electric charge is therefore not a sufficient criterion for selecting a surfactant.
• the surfactants were chosen in this example to be stable in acidic medium, they still tend to degrade under the strongly acidic conditions adopted here.
• EXAMPLE 2 Effect of Surfactant on Drying Time of Gel
• SYNTHIONIC or ANTAROX trade marks
• Aerosil 380 (trademark).
• the surfactant molecules are positioned at the gel / air and silica / solution interfaces to minimize contact with the water molecules.
• the surface of the gel is thus covered with surfactant molecules which can slow down the evaporation or accelerate it.
• FIG. 4 represents the corrosion kinetics obtained on aluminum samples treated with the acid gel, the acid gel containing ANTAROX (trademark) at 2 g. kg "1 and the acid gel containing SYNTHIONIC (Trade Mark) at 2 g kg -1 .
• the operating conditions are as follows: 22 ° C. and 40% relative humidity.
• FIG. 5 is a photograph allowing a visual comparison of a gel according to the present invention (on the left), and of a gel of the prior art, that is to say without surfactant (on the right), dried under the same conditions of temperature, humidity and time.
• a 0.5 M cerium-oxidizing gel film containing 3 M nitric acid (reference on the right in the photo) is prepared on a stainless steel sample.
• Tixosil (trademark) and 1.5 M phosphoric acid are deposited in film form on mild steel, at 22 0 C and 40% humidity. After drying for 3 hours at 22 ° C., with a relative humidity of 40%, and an air sweep at a speed of 0.1 m / s, the samples are inverted to drop, under the effect of gravity. , dry residues.
• the surfactant of the gel of the present invention thus favors the separation of the solid residue, which is very important for cleaning the treated surface and for facilitating the recovery of dry residues from the gel, especially in a radioactive decontamination.
• the first gel contains AEROSIL silica (trademark), 3M nitric acid and 0.33M cerium ammonium nitrate.
• the second gel is identical to the first one, but contains in addition 1 g / 1 of SYNTHIONIC surfactants (trademark).
• Both gels are brushed on two 400 cm 2 radioactively contaminated surfaces, one on the ground (2.2 mGy / h) and the other on the wall (1 mGy / h).
• the gel containing the surfactant is more easily removed by simple brushing than the gel without surfactant.
• the soil contamination is only 0.4 mGy / h and

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• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
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• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)

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  • 2005-10-05 FR FR0552999A patent/FR2891470B1/fr active Active
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