EP0274329B1 - Process for decontaminating the surface of a metallic component contaminated by tritium, and device for using said process - Google Patents

Description

The present invention relates to a process for decontaminating the surface of metal parts contaminated with tritium.

More specifically, it relates to an electrolytic decontamination process, which makes it possible to remove the tritium present on the surface of a metal part without modifying the profile of the surface of this part, in order to be able to possibly reuse it.

This process applies in particular to small metal parts of complex geometry, to large-area parts but of simple geometry, as well as to parts having inaccessible areas such as parts having a tormented geometry.

Among the methods currently known for ensuring the decontamination of parts contaminated with radioactive materials, electrolytic methods can be used such as those described in French patents FR-A-2 490 685 and FR-A-2 533 356, and in the U.S. Patent US-A-3,515,655.

In these patents which use electrolytic processes to decontaminate metal parts, a demetallization of the surface of the parts is obtained, which makes it possible to extract the radioactive particles present on this surface. These treatments thus have the disadvantage of being destructive and of modifying the surface profile of the parts, which cannot therefore be reused directly after treatment. In addition, the methods described in these patents do not relate to the decontamination of parts contaminated with tritium.

• 1^o relier la pièce à décontaminer au pôle négatif d'un générateur de courant continu,
• 2^o mettre en contact au moins une partie de la surface de la pièce à décontaminer avec un mélange comprenant de l'eau et un électrolyte capable de libérer de l'hydrogène par électrolyse, et
• 3^o faire passer un courant électrique entre la pièce à décontaminer et une anode reliée au pôle positif du générateur de courant électrique et en contact avec le mélange comprenant l'eau et l'électrolyte, en appliquant sur la pièce à décontaminer une densité de courant de 10 mA/cm² à 50 mA/cm², de préférence de 10 à 25 mA/cm², pour charger cathodiquement d'hydrogène la surface de la pièce à décontaminer et remplacer ainsi par de l'hydrogène le tritium adsorbé sur la surface de la pièce à décontaminer.

The present invention specifically relates to a method of decontaminating the surface of metal parts contaminated with tritium, which avoids the disadvantage of the methods described above. The method according to the invention for decontaminating the surface of a metal part contaminated with tritium comprises the following steps:

• 1 ^o connect the part to be decontaminated to the negative pole of a direct current generator,
• 2 ^o bringing at least part of the surface of the part to be decontaminated into contact with a mixture comprising water and an electrolyte capable of releasing hydrogen by electrolysis, and
• 3 ^o passing an electric current between the part to be decontaminated and an anode connected to the positive pole of the electric current generator and in contact with the mixture comprising water and the electrolyte, by applying a current density to the part to be decontaminated from 10 mA / cm² to 50 mA / cm², preferably from 10 to 25 mA / cm², for cathodically charging with hydrogen the surface of the part to be decontaminated and thus replacing with hydrogen the tritium adsorbed on the surface of the room to decontaminate.

In the process of the invention, low current densities are used which make it possible to carry out a cathodic loading of hydrogen on the surface of the part. Thus thanks to the choice of current densities from 10 to 50 mA / cm², preferably from 10 to 25 mA / cm², the hydrogen can be adsorbed on the surface of the part whereas, in the processes of the prior art such than that of patent US-A-3515655, where higher current densities are used, the release of hydrogen is very important and promotes the decohesion of the metal; this causes the growth of cavities and cracks to lead to the removal of surface particles and to demetallization of the treated part.

Indeed, at current densities of 10 to 25 mA / cm², the hydrogen formed by electrolysis is largely adsorbed on the surface of the cathode; at current densities of 25 to 50 mA / cm², adsorption of hydrogen is simultaneously obtained on the cathode and evolution of hydrogen gas while at current densities greater than 50 mA / cm², only a release of hydrogen gas is obtained.

Thus, in the case of the prior process described in US-A-3515655, there is no cathodic loading of hydrogen, but only a release of hydrogen gas which causes the removal of metal particles and the deposited radioactive particles. on the part to be decontaminated. In addition, it is not tritium and, with radioactive particles other than tritium, there would be no decontamination at current densities below 50 mA / cm², but only a hydrogen loading of the room .

• a) - adsorption de l'hydrogène et insertion du tritium dans les couches plus profondes de la pièce :
  
  
  
          H + MTads + M → MH ads + MTins
  
  
  
  dans laquelle M représente le ou les métaux constituant la pièce, "ads" signifie adsorbé et "ins" signifie inséré ; et
• b) - rejet de tritium dans le mélange eau-électrolyte :
  
  
  
          H + MTads → MHads + T
  
  
  
  dans laquelle M et "ads" ont la signification donnée ci-dessus.

In the invention, the hydrogen is released as in the processes of the prior art by the following reaction: 2H₂O + 2e → 2H + 20H⁻, but the quantity of hydrogen released is lower, and the latter then reacts with the tritium adsorbed on the surface of the part according to two mechanisms which can be schematized by the following reactions:

• a) - adsorption of hydrogen and insertion of tritium in the deeper layers of the part:
  
  
  
  H + MTads + M → MH ads + MTins
  
  
  
  in which M represents the metal or metals constituting the part, "ads" means adsorbed and "ins" means inserted; and
• b) - rejection of tritium in the water-electrolyte mixture:
  
  
  
  H + MTads → MHads + T
  
  
  
  in which M and "ads" have the meaning given above.

These reaction mechanisms are governed by different parameters such as electrochemical parameters such as current density, cathodic overvoltage and the nature of the electrolyte, temperature and electrolysis time.

Thus, when the cathode overvoltage is located at a correct value, the adsorption of hydrogen is favored, the energy difference between HM and TM causes the insertion of tritium in the room and a rejection of tritium in the water.

At the end of the operation, we obtain a part whose the surface is charged with hydrogen, a water-electrolyte mixture containing part of the tritium present on the surface of the part and tritium inserted in the deeper layers of the part.

The replacement of the tritium adsorbed on the surface of the part by hydrogen makes it possible to form a hydrogen barrier which blocks the backscattering of the tritium inserted in the part. This process is thus very interesting, because the surface layers of the part are not deteriorated and the part can be recycled after treatment.

Generally, the mixture comprising water and an electrolyte consists of an aqueous solution of an electrolyte chosen in such a way that the aqueous solution can liberate hydrogen by electrolysis. By way of example, this electrolyte can be sulfuric acid or an alkali metal hydroxide such as sodium hydroxide. Preferably, sodium hydroxide is used because it delays the evolution of hydrogen. In the case of sulfuric acid, a metal attack is observed from 50 mA / cm² and the attack speed, i.e. corrosion, increases from this value with the current density .

Preferably, the electrolyte concentration of the solution is low to avoid corrosion of the part to be treated. Thus, generally used are aqueous solutions containing 0.1 to 1 mol.l⁻¹ of sulfuric acid or alkali metal hydroxide such as NaOH.

One can, however, use more concentrated solutions, but this is not really of interest because the effluents obtained are, moreover, difficult to treat.

According to a first embodiment of the process of the invention, which is more particularly suitable for the treatment of small parts, the part to be decontaminated is immersed in water or in an aqueous solution, preferably consisting of a aqueous electrolyte solution such as those described above. In this case, the anode can also be immersed in water or the aqueous solution. However, it is more advantageous to use the tank containing the water or the aqueous solution as an anode. This tank can be made, for example, of graphite impregnated with polytetrafluoroethylene wax which is resistant to chemical attack and which is devoid of porosity compared to pure graphite; this has the consequence that the water or the aqueous solution cannot pass through the tank by capillarity.

In this embodiment of the method, several parts can be treated simultaneously by placing them in an electrically conductive basket connected to the negative pole of a direct current generator.

According to a second mode of implementation of the method, more particularly suited to the treatment of large parts, electrolysis is carried out using the so-called "buffer" electrolysis method.

In this case, an assembly comprising the anode and a solid electrolyte is moved over the surface of the part and water is circulated between the anode, the solid electrolyte and the surface of the part to be decontaminated.

dans laquelle R représente un radical organique et n est un nombre de polymérisation, qui est ionisable par de l'eau pure.The solid electrolyte can consist of an ionic conductive polymer ionizable by water or by an aqueous solution. Perfluorosulfonic acid of formula:

in which R represents an organic radical and n is a polymerization number, which is ionizable with pure water.

This mode of implementation of the method is advantageous because it eliminates the use of chemical agents in solution which are responsible for corrosion as well as the problems of reprocessing of effluents. In addition, it makes it possible to decontaminate strongly tritiated zones compared to the others and reach areas that are difficult to access with another treatment. Finally, it is suitable for carrying out "in situ" decontamination and it provides little tritiated waste.

In this second embodiment of the process, the anode can be produced as before by graphite impregnated or not with polytetrafluoroethylene wax.

Generally, to carry out the decontamination according to this second embodiment of the method, an assembly is used which comprises both the anode and the solid electrolyte, and which is provided with means for circulating water or a aqueous solution between the anode, the solid electrolyte and the part to be decontaminated.

Also, the invention also relates to a device for decontaminating the surface of a metal part contaminated with tritium, which comprises a hollow body of electrically conductive material connected to one of the poles of a generator. electric current, the hollow body being provided with at least one liquid outlet orifice to which is applied a porous and permeable element of electrically conductive material, a solid electrolyte applied to the external surface of the porous and permeable element , means for moving the hollow body on the surface of the part to be treated so that the solid electrolyte is in contact with the part, and means for introducing a liquid into the hollow body and circulating it through the orifice outlet between the porous and permeable element of electrically conductive material and the surface of the part to be treated.

The hollow body, which in the process of the invention constitutes the anode of the device, can be made of graphite impregnated with polytetrafluoroethylene wax, and the porous and permeable element can be constituted by a graphite felt. The solid electrolyte applied to the external surface of the porous element can be produced, as above, from an ionic conductive polymer, ionizable with water or an aqueous solution, for example in perfluorinated carboxylic sulphonic acid.

According to a variant of these modes of implementation of the process of the invention, more particularly suitable for the treatment of small parts having a tormented geometry, it is possible to move over the surface of the parts to be decontaminated which are immersed in water, an assembly comprising the anode and the electrolyte solid. In this case, the solid anode-electrolyte assembly can be constituted by a graphite piece provided on one of its faces with a graphite felt coated externally with solid electrolyte, for example of solid ionic conductive polymer.

According to a variant of the second mode, it is also possible to use a "sandwich" anode-solid electrolyte-cathode. In this case, the device further comprises a cathode element in palladium black and / or nickel in which the hydrogen can diffuse, said element being applied to the solid electrolyte so that the hydrogen which has diffused in said element is either installed directly in the room to be decontaminated. In this variant, the cathode face of the solid electrolyte can be successively coated with palladium black by impregnation and with nickel over a thickness of 250 microns. Palladium black can be deposited from palladium salts in aqueous solution, nickel can then be deposited by chemical metallization or by sputtering and then by electrolysis of a nickel salt.

In this variant, the hydrogen diffuses into the nickel cathode. The atomic hydrogen is recovered on the opposite side and is installed directly on the part to be decontaminated which is attached to this assembly.

In this variant, it is also possible to use an anode-solid electrolyte-cathode "sandwich" in which the black of Pd and / or of Ni which constitute the cathodic adsorption element are nested in the underlying layers of the electrolyte. solid. This nesting has the advantage of increasing the adsorption surface of the cathodic hydrogen on the part to be decontaminated.

As an example, we can obtain this structure "sandwich" by impregnating the conductive polymer with an ionic compound of Ni or palladium which is not an anionic complex, for example NiCl₂ or Pd (NO₃) ₂, and then dipping the polymer in a solution of dimethyl aminoborane at 25 % and at 85 ° C. Under these conditions, this organic compound decomposes, giving rise to atomic hydrogen inside the polymer, and this hydrogen chemically reduces the Pd²⁺ or Ni²⁺ cations to the state of finely divided metal in the first layers under - adjacent to the polymer.

The parts which can be decontaminated by the process of the invention can be made of different metals and alloys provided that the electrolyte and the electrolysis conditions are chosen so as to avoid corrosion of the material.

By way of example, the method can be applied to the treatment of parts made of stainless steel or copper alloys, for example brass.

The process of the invention can be carried out at ambient temperature, but it can also operate at higher temperatures, since temperature plays an important role in the insertion of tritium into the deep layers of the part. The amount of H or T adsorbed decreases with temperature during electrolysis. Likewise, the diffusion of Hou T in the cathode increases with temperature; a slight backscatter exists, but the majority of H or T remains blocked in the metal and this blocking becomes even more significant on returning to ambient temperature.

Also, it is preferable to operate at temperatures above ambient temperature while avoiding the risks of corrosion, for example at temperatures of 25 to 100 ° C., in particular at 80 ° C.

In the process of the invention, the duration of electrolysis also constitutes an important parameter, since it acts on the quantity of tritium eliminated. However, in the first embodiment of the method, where the parts are immersed in in water or in an aqueous solution, a balance is obtained after a certain time between the concentration of tritium in the water or the aqueous solution and the concentration of tritium in the part to be treated. Indeed, this corresponds to the following reaction:



T + H₂O ⇆ HTO + H

Also, if in this first embodiment of the process, we want to obtain a higher decontamination rate, it is necessary to successively carry out several decontamination cycles on the same part using for each cycle a new aqueous solution or a new water charge.

• la figure 1 est une courbe représentant l'évolution du taux de décontamination en fonction de la durée du traitement,
• la figure 2 est un diagramme représentant l'évolution de l'activité superficielle en tritium d'une pièce en fonction du nombre de cycles de décontamination,
• la figure 3 représente de façon schématique un ensemble anode-électrolyte mobile, utilisable dans le second mode de mise en oeuvre du procédé de l'invention, et
• la figure 4 représente également de façon schématique l'ensemble anode-polymère électrolyte solide-cathode en noir de palladium et nickel mobile, utilisable dans le cas d'implantation d'hydrogène atomique de diffusion.

Other characteristics and advantages of the invention will appear better on reading the following description of examples of implementation of the method, with reference to the appended drawings in which:

• FIG. 1 is a curve representing the evolution of the decontamination rate as a function of the duration of the treatment,
• FIG. 2 is a diagram representing the evolution of the surface tritium activity of a part as a function of the number of decontamination cycles,
• FIG. 3 schematically represents a mobile anode-electrolyte assembly, usable in the second embodiment of the method of the invention, and
• FIG. 4 also schematically represents the anode-solid electrolyte polymer-cathode assembly in black palladium and mobile nickel, usable in the case of implantation of atomic diffusion hydrogen.

The examples which follow relate to the decontamination treatment of stainless steel or brass parts contaminated with tritium.

EXAMPLE 1

In this example, the surface decontamination of stainless steel parts is carried out using the first mode of implementation of the method, that is to say immersion of the parts in an aqueous solution containing 1 mol.l⁻¹ of NaOH, placed in a heated graphite tank impregnated with polytetrafluoroethylene wax which constitutes the anode of the device. We operate with a current density applied to the surface of the parts of 10 mA.cm⁻², at a temperature of 80 ° C, and electrolysis is carried out for a period of 2 hours.

Following this treatment, the tritium decontamination rate (TD) is determined, which corresponds to the ratio of the surface activity of tritium in the part before treatment to the surface activity of the part after treatment. The loss of thickness of the part is also determined.

12 identical cycles of treatment are then carried out using for each cycle a new aqueous solution of NaOH, and the decontamination rate (TD) of tritium is determined after these 12 cycles.

The results obtained are given in Table 1 below, where the conditions of the electrolytic treatment have also been indicated.

EXAMPLE 2

In this example, brass parts are treated as in Example 1, but using an aqueous solution containing 1 mol.l⁻¹ of sulfuric acid instead of the aqueous NaOH solution. As before, the decontamination rate and the loss of thickness of the part are determined after a treatment cycle. The results obtained are also given in Table 1.

EXAMPLE 3

In this example, the influence of the duration of electrolysis on the rate of decontamination obtained is studied. Electrolysis is carried out under the conditions of Example 1 on stainless steel parts, and the surface activity of the part is measured as a function of the duration of electrolysis always carried out in the same solution.

The results obtained are given in FIG. 1 which represents the increase in the rate of surface decontamination (TD) as a function of the duration of electrolysis (in hours). In view of this figure, it can be seen that the decontamination rate TD hardly increases after two hours, due to the balance which is established between the tritium concentration of the solution and the tritium concentration of the part, as we saw earlier.

EXAMPLE 4

In this example, the decontamination of different stainless steel parts is carried out using the electrolysis conditions of Example 1, and treatment cycles lasting two hours.

Are performed successively several treatment cycles five parts constituted by a ball (part ^No. 1), a flange (part ^No. 2), a flange (part ^No. 3), a rod (part ^No. 4), and a other flange (part ^No. 5), and is determined after each cycle the surface activity of the tritium rooms (microCi.cm⁻²).

The results obtained are given in FIG. 2 which represents the evolution of the surface activity of the parts as a function of the number of treatment cycles.

Curves 1, 2, 3, 4 and 5 relate to parts respectively n ^o 1, 2, 3, 4 and 5.

Note that, in all cases, the surface activity of the part decreases with the number of treatment cycles.

EXAMPLE 5

This example illustrates the use of the so-called "pad" method for decontaminating stainless steel parts.

In this example, the device shown diagrammatically in FIG. 3 is used which comprises an anode constituted by a hollow cylinder 1 made of graphite impregnated with polytetrafluoroethylene wax provided at its base with an outlet orifice 1a to which a porous element is applied and permeable 2 in graphite felt and a film 3 of solid ionic conductive polymer, consisting of perfluorosulfonic acid, the felt and the film 3 being fixed on the cylinder 1 by suitable means, not shown in the drawing.

The hollow graphite cylinder 1 is also provided with another orifice 1b for introducing liquid through which water can be circulated in the anodic hollow cylinder, the water then flowing through the orifice 1a through the graphite felt 2 and the film 3 of ion-conducting polymer. The hollow graphite cylinder can be connected to the positive pole of the electric current generator 5 and it can be moved in the three directions of space by any suitable means, for example by a laboratory automaton 7.

This device can be used to decontaminate the flat part 9 which is connected to the negative pole of the electric current generator 5. Under these conditions, the hollow graphite cylinder 1 is moved to bring it into contact with the part so as to circulate the water in the graphite cylinder 1 through the graphite felt 2 and the film of ionic conductive polymer 3 on the surface of the room. The speed and the mode of movement of the assembly are moved and adjusted on the part 9 so as to obtain satisfactory decontamination.

As an example, a device of this type was used to decontaminate a stainless steel plate using a current density on the plate from 10 mA.cm⁻² to 50 mA.cm⁻² and a speed of movement of the 40 cm.min⁻¹ hollow cylinder.

The total time to carry out the decontamination of a 10 cm² plate having a length of 10 cm is obtained in one hour.

The rate of tritium decontamination of the surface of the part and its loss of thickness are then determined as above. The results obtained and the treatment conditions are given in Table 2 which follows.

It is thus noted that one can obtain a good decontamination rate with a negligible loss of thickness.

In this type of device, the temperature at which one operates is higher than room temperature due to the Joule effect obtained by electrolysis.

EXAMPLE 6

This is a variant of Example 5, in which the diffusibility property of atomic hydrogen is used in a nickel cathode. The device shown diagrammatically in FIG. 4 is used, which is identical to that of FIG. 3 but to which a cathode 4 in palladium black and nickel of 250 μm has been added, located between the film of ionic conductive polymer and the plate to decontaminate. This device is provided with an orifice 1c for discharging the water contained in the hollow cylinder 1.

For example, a device of this type was used to decontaminate a stainless steel plate using a current density on the plate of 20 mA.cm⁻², an electrolyte temperature between 60 and 80 ° C. and a displacement speed of the hollow cylinder from 40 to 200 cm.min⁻¹. The total number of cycles to carry out the decontamination of a 10 cm² plate, having a length of 10 cm is 700.

The rate of tritium decontamination of the surface of the part is determined in the same way. In this case, the latter does not undergo any loss of thickness, and materials degradable to cathodic polarization and to electrolytes can be used: aluminum and copper alloy. The results obtained and the treatment conditions are given in Table 3 below.

EXAMPLE 7

In this example, the first embodiment of the method of the invention is used to treat a medium-sized piece of stainless steel having a tormented geometry constituted by a valve whose orifice is very contaminated with tritium. The part is placed in a tank containing water and a solid anode-electrolyte assembly is introduced into the orifice to be decontaminated, consisting of a graphite pencil covered with a graphite felt and a solid ionic conductive polymer film.

Electrolysis is carried out with a current density of 10 mA.cm⁻², for two hours the temperature obtained by the Joule effect due to the electrolysis. At the end of the operation, the tritium decontamination rate of the surface of the part is determined and its loss of thickness in micrometers. The results obtained and the treatment conditions are given in Table 4.

TABLEAU 4 EX.7 (matériau traité) Electrolyte Temps (heure) Densité de courant (mA.cm⁻²) Perte d'épaisseur (µm) TD acier inoxydable H₂O + acide perfluorosulfonique 2 10 10⁻² 10 The invention is in no way limited to the embodiments envisaged or described above. In particular, conventional apparatuses such as those described in French patents FR-A-2 490 685 and FR-A-2 533 356 can be used for the so-called buffer electrolysis method. for producing the anodes used in the process of the invention, as well as other materials as solid electrolyte which can be combined with water or with suitable aqueous solutions. Furthermore, when the so-called buffer electrolysis method is used, it is possible to use electrolytes in aqueous solution, for example a solution of soda or sulfuric acid.

TABLE 4 EX.7 (treated material) Electrolyte Time (hour) Current density (mA.cm⁻²) Thickness loss (µm) TD stainless steel H₂O + perfluorosulfonic acid 2 10 10⁻² 10

Claims (18)

1. Process for the decontamination of the surface of a metal part contaminated by tritium, characterized in that it comprises the following stages:

   1) connecting the part to be decontaminated to the negative pole of a direct current generator,

   2) contacting at least one portion of the surface of the part to be decontaminated with a mixture incorporating water and an electrolyte able to release hydrogen by electrolysis, and

   3) passing an electric current between the part to be decontaminated and an anode connected to the positive pole of the electric current generator and in contact with the mixture incorporating water and an electrolyte, by applying to the part to be decontaminated a current density of 10 to 50 mA/cm⁺² in order to cathodically charge with hydrogen the surface of the part to be decontaminated and thus replace by hydrogen the tritium adsorbed on the surface of the part to be decontaminated.
2. Process according to claim 1, characterized in that the mixture incorporating water and electrolyte is constituted by an aqueous solution of alkali metal hydroxide or sulphuric acid.
3. Process according to claim 2, characterized in that the mixture incorporating water and electrolyte is constituted by an aqueous soda solution.
4. Process according to any one of the claims 1 to 3, characterized in that the anode is made from polytetrafluoroethylene wax-impregnated graphite.
5. Process according to any one of the claims 1 to 4, characterized in that the part to be decontaminated is immersed in water or aqueous solution.
6. Process according to claim 5, characterized in that the anode is constituted by a vessel containing the water-electrolyte mixture.
7. Process according to either of the claims 1 and 4, characterized in that the electrolyte is a solid electrolyte.
8. Process according to claim 7, characterized in that the solid electrolyte is an ionic conductive polymer.
9. Process according to claim 8, characterized in that the solid electrolyte is perfluoro-sulphonic acid of formula:

   

   in which R represents an organic radical and n is a polymerization number.
10. Process according to any one of the claims 7 to 9, characterized in that an assembly incorporating the anode and the solid electrolyte is moved over the surface of the part and in that water or an aqueous solution is circulated between the anode, the solid electrolyte and the surface of the part to be decontaminated.
11. Process according to any one of the claims 1 to 10, characterized in that the part to be decontaminated is of stainless steel or a copper alloy.
12. Apparatus for performing the process for decontaminating the surface of a tritium-contaminated metal part according to any one of the claims 7 to 10, characterized in that it comprises a hollow electricity conducting material body (1) connected to one of the poles of an electric current generator (5), the hollow body being provided with at least one liquid outlet port ( 1a) to which is applied a porous, permeable element (2) made from electricity conducting material, a solid electrolyte (3) applied to the outer surface of the porous, permeable element and means (7) for displacing the hollow body on the surface of the part to be treated, so that the solid electrolyte is in contact with the part (9) and means (1b) for introducing a liquid into the hollow body and for circulating it through the outlet port between the porous, permeable electricity conducting material element and the surface of the part to be treated.
13. Apparatus according to claim 12, characterized in that body (1) is of polytetrafluoroethylene wax-impregnated graphite.
14. Apparatus according to either of the claims 12 and 13, characterized in that the porous, permeable element (2) is of graphite felt.
15. Apparatus according to any one of the claims 12 to 14, characterized in that the solid electrolyte (3) is an ionic conductive polymer.
16. Apparatus according to any one of the claims 12 to 15, characterized in that it also comprises a cathodic palladium black and/or nickel element (4) in which the hydrogen can diffuse, said element being applied to the solid electrolyte (3) in such a way that when the hydrogen has diffused into said element, it is directly implanted in the part to be decontaminated.
17. Apparatus according to claim 16, characterized in that the cathodic adsorption element is fitted into the solid electrolyte (3).
18. Apparatus according to either of the claims 16 and 17, characterized in that the cathodic element (4) has a thickness of approximately 250 µm.

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