SK36995A3 - Gel for catching of radioactive contamination and its using for protect or decontamination of surface - Google Patents

Abstract

A novel gel, for radioactive contamination retention, consists of an aq. colloidal soln. contg. (by wt.) 2.5-15% gelling agent and 5-15% film-forming agent contg. SiO2, Al2O3, MgO, FeO and K2O. Pref. the gel also contains an acrylic copolymer and the gelling agent is a synthetic polymer. Also claimed are: (i) a process for protecting a surface from contamination, involving applying the above gel to the surface and, after contamination, removing the gel by rinsing with water; and (ii) a process for decontaminating a surface, involving applying the above gel and then removing the gel by rinsing with water.

Description

Gel to capture radioactive contamination and use it to protect or decontaminate a surface

Technical field

4 '

The invention relates to a gel which can bind radioactive contamination, which can be used for dry-action in nuclear installations, in particular for dismantling.

State of the art

During dismantling of a nuclear installation, it is often necessary to relocate and / or dismantle the existing installation of the entire installation. These operations can cause general radioactive contamination of the entire installation due to metal filings or aerosol formation. This also happens during the maintenance of these installations, where radioactive contamination often occurs as a result of repairs and replacement of various equipment.

In order to allow these operations, the radioactivity is on the already uncontaminated areas.

prevent radioactive proliferation during important contamination of fixed contaminated areas and protect dotec + <U)

One technique used is to coat contaminated surfaces with a polyvinyl chloride film that can fix contamination; the contaminated polyvinyl chloride film is then eliminated.

This technique is a large area, however, because it is difficult to apply especially when large amounts of waste are generated.

For this reason, have there been any indications that these films would be consumed with varnishes or paints that could be removed? and which could be applied? on areas to be? protected or decontaminated. These coatings could then be mechanically removed. However, this solution entails certain problems, since the film tears up partially. Is it also possible to lay? a polymer such as e.g. polyurethane that adheres to the surface, but this technique is mainly used during disassembly and does not allow the elimination of radioactive contamination.

SUMMARY OF THE INVENTION

The subject of the invention are gels capable of absorbing gels. radioactive contamination. Can they be used? to protect or decontaminate the surface and can then be easily disposed of.

SiOni Al _n O-> MgO, FeO and K n

A gel according to the invention capable of absorbing? radioactive contamination consists of the following appropriate colloidal solution:

- 2.5 to 15% by weight. a gelling agent; and

- 5 to 15% by weight of a film-forming agent comprising

2- ₃ »

The aqueous solution preferably contains in addition 0.2 to 1 -X materials ^-, the preservative is a bacteriostatic action and also optionally one or more additives selected from antistatic agents, coloring agents, and acrylic copolymers. In this case, the amount of antistatic agent is from 0.5 to 15% by weight, the amount of acrylic copolymer is from 0.1 to 8% by weight. and the amount of dye can move? from 0, C01 to 1 X mass.

The use of film-forming agent in the gel of the invention, comprising _a Si0, Al ^ O ^, MgO, FeO, and e.g. of the product sold under the trademark Plastorit NaiAsch ,. which is a product with three mineral constituents and, in a way, is flaky, such as sieve, quartz and silicates (magnesium hydrogen silicate and aluminum hydrogen silicate) exhibits many advantages. this

The 3 film-forming agent comprises e.g. 52% SiCl2, 22% Al2Cl2,

12.6% MgO, 3.0% FeO and 2.8. % KpO. This agent is practically inert and has good wetting ability in aqueous and oily media. It further increases the adhesion of the gel, after drying the gel gives a very hard and resistant surface to walk on.

A further advantage of the gel is that the gels additionally have dispersed adsorbent particles in the aqueous solution, the amount of particles in the aqueous solution being from 1 to 5%

It should be noted here that the gel is a colloidal solution whose phases are difficult to define with respect to the molecular weight of the colloid and the state of its dispersion in the solution.

This gel structure is achieved by adding the gelling agent to the aqueous solution with slow agitation until optimum swelling is achieved.

The gel according to the invention preferably uses a gelling agent which is an organic agent, such as a synthetic polymer or esterified cellulose.

An example of such gelling agents is the commercial product of Scott Bader S.A. under the trademark Texipol 63508, which is a dispersion of an organic solvent in an aqueous solution of a synthetic polymer and another product of the Dow Chemical Company, sold under the trademark Methocel, which is hydroxypropylmethylcellulose in the form of granules.

The gelling agent content is selected such that a sufficient viscosity is obtained and that the gel can be applied as a layer on the surface of the article. It is generally preferred that the gel exhibits a viscosity of at least 300 ° C at the time of use. Thus, the formulation can be applied very easily, e.g. even with a spray gun.

In order to obtain the characteristics of the organic gelling agents according to the invention, it is necessary to adjust the gelling agents content to 5 to 15% by weight. solution, which depends in particular on the gelling agent used.

The aqueous gel solution according to the invention may also contain a preservative, an antistatic agent, an acrylic copolymer, a colorant and optionally an adsorbed agent.

Suitable preservatives are bacteriostatic products, which exclude bacterial fermentation. An example of a preservative is phenoxyethanol, e.g. the product sold by Ehone Foule.nc under the brand IGĽPAL CD 41 C.

It is also possible to add an antistatic agent to the solution, especially when the gel is intended to be applied to surfaces of plastics such as polymethyl methacrylate surfaces, e.g. made of plexiglass or ferritic steel.

Antistatic agents suitable for use in this gel may be surface active agents of the cationic, anionic or nonionic type. As an example _, cationic surfactants, such as ethoxyamines, a commercial product of Ehone-Poulenc under the trademark Cemulcst C20, may be mentioned.

The addition of an acrylic polymer to an aqueous colloidal solution is of interest in those cases where the gel is intended to be applied to metal surfaces. Indeed, this acrylic copolymer enhances both the mechanical resistance and the mechanical resistance of the gel made film. The copolymer can be added in the form of an aqueous dispersion without styrene. An example of a useful copolymer is the product sold by LuzzatiS Figlio under the brand Luzamul AC.

A great advantage is that the gel may additionally contain a coloring agent. In this case, it is possible to first visualize good gel coverage of the treated surface, then complete removal of the contaminated gel at the end of the operation. Examples of suitable dyes include Pouge Lumina 23 and E 127 dye.

It is further desirable that the gel also contain an adsorbent powdering agent to adsorb and retain the radioactive elements that have caused the contamination. This adsorbent may be zeolite because zeolites are capable of fixing many cations. It is also possible to use activated carbon. The adsorption agent is selected having regard to the radioactive element which caused the contamination.

The gels of the invention can be prepared by stirring in a very simple manner at room temperature while mixing with demineralized water with optional aids such as a preservative, an antistatic agent and / or a colorant and then to this solution - and always with stirring - adding the gelling agent until optimum swelling, then the film-forming agent and, if necessary, the acrylic copolymer ε / or adsorbent.

The gels of the invention may be used to protect areas from contamination or to decontaminate areas already contaminated.

In the first case, the gel of the invention is applied to the area to be protected before contamination could occur; after contamination of the surfaces, the gel is removed by washing with water.

In the latter case, the gel of the present invention is applied to the already contaminated area, allowing sufficient time to fix the radioactivity and then removing, e.g. washing with water.

The gel can be applied to the surface in a completely classical manner, e.g. by spraying with a gun, dusting, immersion and dripping, or even with a brush. Subsequently, the gel can only be removed from the surface by washing with water, e.g. jet of water under pressure.

Usually, demineralized water or even an aqueous solution is used for washing, in which the gels may be dissolved or lead to the formation of a water-removable coating.

When an adsorbing agent such as e.g. zeolite or activated carbon, the radioactivity can be trapped on the adsorbent. This method can eliminate the formation of aqueous effluents that are highly radioactive.

Surfaces suitable for protection or decamination by means of the gel according to the invention may be quite different, such as those made of plastic material, e.g. plexiglass, i.e., polymethyimethacrylate, or metal surfaces, e.g. stainless steel or stainless steel.

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Other characteristics;

It will of course be better understood from the description of the examples that is not exhaustive, but that is not merely an explanation of the invention.

Example 1 Preparation of gel no. 1

Prepare a gel, the composition of which is found in Table 1 with soda, pal OD, by mixing with the demineralized water, neutralized with slow stirring, the preservative (ľg 41 G) with the dye (D 127.); then g with sufficient swelling is added while stirring gently.

gelling agent Finally, a film-forming agent (Plastorite S) is added.

lo (Texipol 53505) up to a slow melt. 2

The gel no. 2, the composition of which is given in Table 1, following the same procedure as in Example 1, but 0.5% by weight is added to the cineralized water. an antistatic agent such as Ceaulcat 020, p. we replace E 127 with Eouge Lumina 2B.

Example 3 Preparation of gel no. 3

The composition of this gel is shown in Table 1. SO parts mass. gel no. 1 prepared according to Examples 1 and 20 parts by weight. acrylic copolymer (Luzamul AC) and 1.5 wt. A portion of Texipol 63503 gelling agent is mixed together.

Example 4 Preparation of gel no. 4

For the preparation of gel no. 4, the composition of which is given in Table 1, with SO masses. gel parts no. 2 prepared according to example 2 is mixed with 20 masses. parts of acrylic copolymer (Luzamul AC) and with 1.5 wt. part of Texipol 63503.

Examples 5 to 7 Protecting Plexiglas surfaces

In these cases, gels no. 1, 2 or c. 4 to plexiglass surfaces in order to study the properties of the gel in terms of adhesion in the grooves to the surface and the ease of rinsing with water.

The results are summarized in Table 2.

Table 2 - Plexiglas surfaces

no. gel with* grip in grooves stick to the desktop ease of rinsing with water 5 no. 1 very bad really good very good 6 no. 2 good in really good with* very good 7 no. 4 very good really good in very good

In view of these results, it can be stated that gel no. 2. which contains an antistatic agent and not an acrylic copolymer, is more suitable for protecting plexiglass surfaces.

Examples 8 to 11

Surface protection from eritic steel

The properties of various gels intended to protect the ferritic steel surface were also studied in these examples. The gels used and the results obtained are shown in Table no. Third

Table 3 - Ferritic steel surfaces

no. gel grip in grooves cling to the desktop easy rinsing with water 8 no. 1 evil. bad good 9 no. 2 very good really good good with pressurized water 10 no. 3 good bad good 11 no. 4 very good very good good enough with pressurized water

Given some of the best and antistatic results, it can be stated that the gels satisfy are gels no. 2 and 4, which contain an agent and optionally an acrylic copolymer.

- 9 Examples 12 to 15 - 304 L stainless steel surface protection

In these examples, as in the previous examples, the protective properties of the gel were studied on 304 L stainless steel surfaces.

The gels used and results were summarized in Table 4.

Table 4 - The surfaces of stainless steel / 304 L / _. · -JS 7> .... t .. ..j x 7 _ f ~ ui, _Λ, ·. FROM

with" c. gel grip in grooves adherence to flat easy rinsing with water 12 No. 1 very good the average bad 13 no. 2 very good the average bad 14 no. 3 good really good good enough with pressurized water 15 no. 4 good very good pretty good with pressure vogLou_-

As shown in this table, best results were obtained with gels no. 3 with 4 containing an acrylic copolymer and optionally an antistatic agent.

Example 16 - Protection of Plexiglas Surface against Cesium Contamination 137

In this example, gel no. 2 to which 5% by weight is added. zeolize IE 96 as a cesium adsorbent 137. Zeolite IE 96 is sodium aluminosilicate manufactured by Union Carbide.

The gel is applied to the Plexiglas test plates using a spray gun, allowed to jam for 24 hours, and then cesium 137 is applied to the test plates. The gel is then removed by washing with demineralized water. The rinsing water is filtered and the activity retained by the gel and filtrate is calculated.

The results are shown in Table no. ·?

Table 5 - Protective and Retention Gel

no. gel initial activity activity activity retained gel samples Bq / .sample traction of the initial " ^z " activity t 16 no. 2 zeolite IE 96 2,47.10 ⁴ 2 2,33.10 ⁴ 94.3 17 no. 2 zeolite IE 96 2,45.10 ⁴ 94 2,22.10 ⁴ 90.6 18 no. 2 without zeolite 1,45.10 ⁴ 4 8,43.10 ³ 58.1

This test confirms the effectiveness of gel protection. After rinsing with demineralized water, virtually all of the radioactivity (94.3%) is collected and removed by gel.

Example 17 - Decontamination of Plexiglas surface

In this example, the procedure was the same as in Example 16, but the gel was applied to plexiglass test plates that had already been radioactive contaminated with cesium 137. Gel no. 2, to which 5% zeolite IE 96 was added.

The results obtained are summarized in Table 5. 2 of these results, it can be seen that the gel has a higher cesium retention capacity, even though it has been applied to the test plate.

Example 13 - Protecting a Plexiglass Surface

In this example, the same procedure as in Example 16 was followed, but gel no. 2 without the addition of zeolite. The results are summarized in Table 5.

These results clearly demonstrate that the gel has protective properties since the residual activity of the areas after gel removal is negligible. However, the ability of the gel to retain radioactivity without the addition of zeolite is very low, less than in Example 16, since without the adsorbent an important fraction of radioactivity enters the wash water.

Example 9 - Protection of austenitic steel surface

In this example, the procedure described in Example 6 was followed to protect the austenitic steel surface from cesium 137 contamination. 3 containing 5 D of zeolite IB 95. Thereafter the protected area is exposed to cesium 137 and the gel is removed by washing with water. The results obtained are summarized in Table 6.

These results only confirm the effectiveness of gel protection against cesium 13 contamination

Example 20 - Decontamination of austenitic steel bars

This example proceeds as in Example príklad to decontaminate the austenitic steel surface contaminated with cesium 137 2a using gel no. 3 containing 5% y

materials. The results obtained are summarized in Table 6. These results confirm the increased retention capacity of the gel, even if the area was pre-contaminated.

Table 5 - Protective and Retention Gel

no. gel initial sample activity activity samples activity gel arrested Bq / sample faction early activities in % 19 no. 1 D D zeolite IE 96 2.4.10 ‘ 38 2,2.10 * 92.3 20 no. 2 zeolite IE 96 3.38.10 ⁴ 1,76.10 ³ 2,90.10 ⁴ 85.8 21 no. 3 2,32.10 ⁴ 2,92.10 ² 1,35.10 ⁴ 58.2 without zeolite

Example 21 - Protection of austenitic steel surface

In this example, the same procedure as in Example 18 was carried out using gel no. 3 without zeolite for surface protection. The results obtained are summarized in Table 2 and also confirm the protective ability of the gel, but its much less retention capacity of radioactivity.

Examples 22 to 24

In these examples, the effect of protection of gels no. 1 against plutonium contamination 239 surfaces of stainless steel, ferritic steel or plexiglass.

Table no

The results of this table confirm the importance of gel protection in case of plutonium contamination. If the surfaces are gel protected, then almost all of the radioactivity induced by β-239 can be removed by simply washing with water.

7th

This table compares the results obtained with plutonium 239 contamination of areas without gel protection when the surfaces are only washed with water and the results of those areas protected by gel. In the first case, water washing is not very effective, the bulk of plutonium 239 remains flat.

These results confirm the importance of the gels of the invention.

Table 1

Composition of protective gel for dry action

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Claims (15)

1. Gel capable of retaining radioactive contamination, characterized in that it consists of an aqueous colloidal solution containing 2.5 - 15% by weight. a gelling agent; and 5 - 15% by weight. a film forming agent containing SiO 2, A12 ° 2 ' ^{Fe0 with K} 2 ° * 2. The gel of claim 1 wherein the aqueous solution further comprises 1.2 to 1% by weight. a preservative with a bacteriostatic effect. Gel according to one of Claims 1 and 2, characterized in that the aqueous solution additionally contains C5 to C5. 1.5% by weight. an antistatic agent. Gel according to one of Claims 1 to 3, characterized in that the aqueous solution contains 0.1 to 3% by weight. of an acyl copolymer. Gel according to one of Claims 1 to 4, characterized in that the aqueous solution additionally contains 0.001 to 1% dye. . The gel of one of claims 1 a; characterized in that it contains particles of the adsorption agent dispersed in the aqueous solution, the amount of particles being between 1 and 5% of the aqueous solution. Gel according to one of Claims 1 to 5, characterized in that the gelling agent is a synthetic polymer. Gel according to one of Claims 1 to 7, characterized in that the film-forming agent is composed of three components comprising SiO 2, Al 2 O 4 P 2 O, FeO and K 2 O. Gel according to one of Claims 1 to 3, characterized in that the preservative is phenoxy ethanol. Gel according to one of Claims 1 to 9, characterized in that the antistatic agent is ethoxyamine. Gel according to one of Claims 1 to 10, characterized in that the adsorption agent is zeolite or activated carbon. A method of protecting a surface from contamination, characterized in that before contamination, a gel according to any one of claims 1 to 11 is applied to the surfaces after contamination of the surfaces, the gel is removed by washing with water. 13. A process for decontamination of a contaminated area, characterized in that one gel is applied to the contaminated area and is then removed by washing with water. claims 1 to 11, which Process according to either of Claims 12 and 13, characterized in. in that the surface is made of polymethylmethacrylate or ferritic steel and that the gel comprises a gelling agent, a film-forming agent, an antistatic agent and a preservative. 1 5 steel steels a The method of claim 1, wherein the gel comprises gelling of claims 12 and 13, wherein the surface is a ferritic agent, a film-forming agent, an antistatic agent, a preservative and an acrylic copolymer. Process according to either of Claims 12 and 13, characterized in that the surface is of stainless steel and the gel comprises a gelling agent, a film-forming agent, an acrylic copolymer, a preservative and, optionally, an antistatic agent. à » Process according to one of Claims 14 to 16, characterized in that the gel additionally comprises an adsorption agent which is a zeolite and also a colorant.