FR2678761A1 - BLOCK CONTAINING CONTAMINATED ION EXCHANGE RESINS AND PROCESS FOR PREPARING THE SAME. - Google Patents

Abstract

The invention relates to a block containing contaminated ion exchange resins for storage, and it is characterized in that the ion exchange resins are incorporated, after saturation with water, in a composite matrix made of a resin. hardened epoxy and a hardened cement, chosen from Clinker slag cements and slag and ash cements, with the addition of the water necessary for the hydration of the cement components. Thanks to the presence of cement in the composite matrix, the core temperature of such blocks can be limited to 55-63 degrees C during their preparation.

Description

B Loc containing ion exchange resins

  contaminated and its method of preparation.

  The subject of the present invention is a block containing contaminated ion exchange resins, for example by toxic or radioactive elements, as well as a process for the preparation of such a block. It is particularly applicable in the field of resin storage. ion exchangers contaminated with weak radioactive elements

and average activity.

  The ion exchange resins used to purify the water of the nuclear installations undergo, after a certain time, degradation phenomena and, consequently, lose their effectiveness. It is then a question of storing these spent ion exchange resins which have fixed during their use various radioelements conferring

some radioactivity.

  Several processes are known for conditioning these contaminated resins with a view to their storage. Among them, coating processes in thermosetting resins, such as those described in documents FR-A 2 251 081, FR-A 2 361 724 and EP-A 0 127 490 are satisfactory because they make it possible to ensure good retention of the radioactivity, but they present

however some disadvantages.

  Thus, the process of document FR-A-2 251 081 is not suitable for incorporating into cationic resins cationic resins which are not completely used because, in this case, the polymerization of the epoxy resin is partially inhibited by the cationic resin which consumes certain compounds

  necessary for the hardening of the resin.

  This phenomenon can be avoided by performing a pretreatment in basic aqueous solution of the ion exchange resins as described in document FR-A 2 251 081, but the realization of this complementary step constitutes a drawback, all the more so since it leads to the production of new effluents contaminated by

radioactive elements.

  The process described in EP-A 0 127 490 also makes it possible to incorporate cationic resins having active sites in an epoxy resin, but it has the drawback of requiring the use of particular amine hardeners which are

relatively expensive products.

  In addition, the processes using these thermosetting resins are sensitive to the initial temperature which accelerates the polymerization and / or leads to a release of heat detrimental to the quality.

of the block formed.

  EP-A-0 274 927 discloses a process for packaging waste in composite matrices based on cement and epoxy resin, but in this case the radioactive waste consists of chemical coprecipitation sludges which may contain 20 at 40% water, powdery dry waste such as incineration ash of combustible material or technological waste, incombustible as

than glass and metals.

  It has also been envisaged to include ion exchange resins in a cement matrix, but this process is of limited interest because of the low coating coefficient obtained and the need to also perform a pretreatment of the resins to avoid any interaction. with cement, as described by J Duquesne Cogéma and C Jaouen

  SGN Concrete Encapsulation of Ion Exchange Resins-

  The present invention specifically relates to a block containing contaminated ion exchange resins for their storage, which overcomes the

  disadvantages mentioned above known methods.

  According to the invention, the block containing contaminated ion exchange resins for storage is characterized in that the ion exchange resins are incorporated in a composite matrix consisting of a hardened epoxy resin and a hardened cement Among the blocks of the invention, the choice of an epoxy resin and a cement with a low heat of hydration constituted by a slag cement is selected from the C linker slag cements and the slag and ash cements. Clinker (CLK) and / or a slag and fly ash cement (CLC) makes it possible to have a matrix compatible with ion exchange resins, even when these are saturated with water and contain, for example, 50 to 55% by weight of water, and / or have active sites usually requiring

pretreatment.

  Moreover, the choice of this matrix makes it possible to obtain a high coating coefficient and a block having physical and mechanical properties

very interesting.

  According to the invention, the proportions by weight of cement and cured epoxy resin forming part of the matrix are chosen so as to obtain the desired retention characteristics of the radioelements, resistance to lixiviation and mechanical resistance for storage purposes. of

  block with a high degree of safety.

  Generally, the composite matrix comprises: from 35 to 65% by weight of cured epoxy resin, and from 35 to 65% by weight of Clinker slag-cured cement and / or slag-cured cement and

fly ash.

  With this matrix, relatively large amounts of ion exchange resins can be included in the block; this can thus contain up to 45% by weight of exchange resins

  of contaminated ions, saturated with water.

  These ion exchange resins may consist of cationic exchange resins, anionic resins or mixtures of these resins, in the form of grains or

particles obtained by grinding.

  Generally, these are organic ion exchange resins such as polystyrene resins crosslinked with divinyl benzene which contain, for example, sulphonic groups or hydroxyl groups. In the block of the invention, a hydrophilic epoxy resin, compatible with both the cement used and the resin, is preferably used.

ion exchange to be conditioned.

  By way of example of such hydrophilic epoxy resins, mention may be made of the diglycidyl ether of bis-phenol-A and the diglycidyl ether of bis-phenol-F

  hardened by reaction with an amine hardener.

  It is specified that bisphenol A diglycidyl ether has the formula:

  H 2 C HC H 2 C O -C - <CO O CH 2 CH CH 2

o'0 CH 3 O

  The diglycidyl ether of bis-phenol L F corresponds to the formula

the:

0 CH 2 CH H 2

O

O -CH 2 <

H 2 C HC H 2 C O

  In the invention, the use of a hydrophilic epoxy resin is advantageous because it facilitates the production of a homogeneous mixture with the

cement, in the presence of water.

  The invention also relates to a process for preparing the block containing the resins

  contaminated ion exchangers, described above.

  This process comprises the following successive stages: 1) water saturation of the contaminated ion exchange resins, 2) stirring addition of the water necessary for hydration of the cement with water-saturated ion exchange resins, 3) addition cement, with stirring to the suspension obtained in 2), and 4) addition to the mixture obtained in 3) of

  the epoxy resin and its hardener.

  In the first stage of this process, the contaminated ion exchange resins are saturated with water, which is carried out by immersing these resins in water for a sufficient period of time, for example for 24 hours. After this operation, the ion exchange resins until the flow of water disappears to ensure that the ion exchange resins contain only their saturation water which generally accounts for about 50 to 55% by weight of the ion exchange resins. saturated ions but can go in

  some cases up to 65% by weight.

  In the second step of the process, the water required for hydration is then added to the resins.

  cement by performing this operation with stirring.

  The amount of water of hydration required for curing Clinker Dairy Cements or Dairy Cements and fly ash depends on the amount of cement that will be introduced into the block. It is generally such that the weight ratio of water to hydration / cement is 0.25 to 0.35. After the introduction of water, the cement is added with stirring and stirring is continued until a fluid paste is obtained, then the epoxy resin is added in the liquid state.

  and its amine hardener by continuing agitation.

  Generally, the operations of addition of water, cement and epoxy resin are carried out

in a mixer.

  After addition of the epoxy resin and its hardener, the mixture can be emulsified by high speed rotation, allowed to settle and poured into a mold having the dimensions of

block to manufacture.

  After this operation, the block is allowed to harden in the mold, which can be obtained

  relatively quickly, for example in 12 hours.

  In this process, the choice of the amine hardener is also important because by choosing a suitable amine hardener, the epoxy resin is allowed to cure in the presence of large amounts of water. Amino hardeners containing a combination of aromatic and aliphatic amines can be used, for example, for this purpose and, by varying the amounts of these different amines, an optimized hardener can be obtained which is suitable for the preparation of an epoxy composite matrix. Cement suitable for coating ion exchange resins

saturated with water to condition.

  Generally, the proportion of aminated hardener is such that the weight ratio hardener / epoxy resin is preferably

0.5 to 0.6.

  The b Locs obtained by the process of the invention have very interesting properties because they are extremely hard and not very reactive to attack. In addition, they have the following advantages over ion exchange resins coated in other matrices: fire risks in storage due to the lower heating value of the coating matrix, low water swelling coefficient, and lower cost of the coating matrix

  compared to that of epoxy resins alone.

  Other features and advantages of the invention will appear better on reading the following examples given of course by way of illustration and not limitation with reference to the accompanying drawing in which Figure 1 is a diagram showing as a function of time the temperature at the heart of a block according to the invention, containing contaminated ion exchange resins, during its

  hardening, for two identical tests.

  Figure 2 is a diagram showing how

  time the temperature of a block of the prior art

for two identical tests.

  Figure 3 is a diagram grouping the

  average values obtained in Figures 1 and 2.

Exempt 1.

  In this example, 490 g of contaminated ion exchange resins, consisting of Rohm and Haas IR-400 anionic resins, are incorporated into a matrix formed from the following constituents: water (78 g), slag cement Clinker CLK 45 (222 g), c liquid epoxy resin marketed by the company Spado Lassailly under the reference SL MN 201 T (200 g), and aminated hardener marketed by the company

  Spado Lassailly under the reference SL D 6 M 5.

  First, the contaminated water exchange resins are saturated with water by swelling them in water for 24 hours and then subjected to spinning. 400 g of dewatered anionic resins are then weighed and the following are added: 78 g of water, that is to say the amount sufficient to hydrate the 222 g of

cement CLK 45.

  The resins are mixed with water, then the CLK 45 cement is added to the suspension and the mixture is kneaded so as to obtain a very fluid paste. The SL NM 201 T epoxy resin and the SL D 6 M 5 hardener are then added while continuing the mixing. The mixture is then poured into the mixture.

  in a mold and allowed to cure for 36 hours.

  The resulting block is then demolded. It has a very good surface appearance. Its Shore D hardness is measured using a Shore durometer for thermosetting polymers which determines the hardness by driving a needle mounted on a calibrated scale. high since it

  corresponds to a value of 70 Shore units.

  The block obtained is also subjected to a water absorption test by immersing it for one month in water. After this period, it is found that the mass absorption coefficient of water is of the order of 1 at 3%. The block obtained thus has very satisfactory characteristics for storage

anion exchange resins.

Exempt 2.

  The same anion exchange resins and the same matrix constituents are used as in Example 1 except the hardener which in this example is the commercialized product.

  by Spado Lassailly under The reference SL D 2005.

  The same procedure as in Example 1 is followed using the same proportions to effect the coating of 400 g of exchange resins.

of anions in the composite matrix.

  This gives a solid block having properties substantially identical to those of the block obtained in Example 1, except that its appearance

outside is brighter.

Example 3

  The same procedure is followed and the same matrix as in Example 1 is used to coat 400 g of cationic ion exchange resins of the

Rohm and Haas IR 120 type.

  We also use the same proportions

  water, cement, resin and hardener.

  The block obtained also presents very

good properties.

  Indeed, its Shore hardness is 66 units and its water absorption coefficient at one month is

of 3%.

Example 4

  In this example, 400 g of a mixture of ion exchange resins containing 266 g of Rohm and Haas IR 120 cationic resins and 134 g of anionic ion exchange resins are coated in the same composite matrix as in Example 1.

Rohm and Haas IR A 400.

  The same procedure is followed and the same proportions are used as in Example 1. This gives a solid block having the following characteristics: Shore hardness: 67 units,

  water absorption rate at one month: 1 to 3%.

Exmp The comparative 1.

  In this example, the coating of contaminated ion exchange resins is carried out using only as a coating component a resin

epoxy and its hardener.

  In this case, 200 g of ion exchange resins saturated with water and spun with SL NM 201 T liquid epoxy resin and SL D 6 M 5 hardener are mixed to prepare a block of conditioned ion exchange resins only. in an epoxy resin having a volume of 0.51 After 8 to 10 hours, the block is hardened and has the following characteristics: Shore D hardness: 60,

  water absorption rate at one month: 1%.

  In the following table, the characteristics of the block obtained in this example and the block characteristics of 0.5 l obtained are grouped together.

  in the same way as in Examples I to 3.

1 1

BOARD

  Characteristics Comparative Example Invention (epoxy alone) (epoxy-cement) Hardness Shore D 60 70- 75 Maximum temperature at core 78 C 75 C 58-63 C

Poly-time

  melting 8-10 h 12-15 h Swelling in water 28 1% 1 to 3% In view of this table, it is noted that the characteristics of the blocks of the invention are more interesting, with regard to the hardness and the

  maximum temperature at the heart of the block.

  Thus, the fact of using in the invention a cement epoxy composite matrix makes it possible to limit, during the polymerization, the core core temperature to a value lower than that

  that we obtain with an epoxy resin alone.

  In the case of the invention, the core temperature is limited to 58-63 C, while in the case of an epoxy resin alone, it can reach 78 C for a block of 0.51 Also, for volume blocks more importantly, the core temperature can become greater than 1000 C with an epoxy resin alone Gold, at this temperature, the water contained in the ion exchange resins saturated with water is brought to the boil and the water vapor engendered in the block is causing more damage or

less important.

  The use according to the invention of a composite matrix based on epoxy resin and cement thus provides a significant reduction in the exotherm of the block hardening reaction which comprises both the polymerization of

  resin and hardening of the hydraulic binder.

  For the hydraulic binder part of the matrix, the enthalpy corresponding to the setting of the binder is very substantially less than the enthalpy

  of polymerization of the epoxide part.

  By way of example, the values of the heat of polymerization of an epoxide system and of the heat of hydration of a cement CLK: polymerization (epoxy resin) = 25 kcal / mol, are given below,

  AH hydration (CLK) = 4 at Skcal / mol.

  In the attached figure, the core temperature (in C) of 2 blocks according to the invention weighing 640 g, as a function of time, is represented.

(in h) when hardening.

  In this figure, curves 1 and 2 refer to a block prepared in duplicate from the following constituents: 256 g of mixed-bed ion exchange resins (cationic 1/3 anionic 2/3), 46 g of water, 146 g of CLK 45 cement, 128 g of SL MN 201 T epoxy resin, 64 g of SL D 6 M 5 hardener,

resin / hardener ratio: 2.

  From the two curves, obtained on samples of mass and of identical nature, the average values of the peak of polymerization temperature T C = 60 C i C are obtained from the time corresponding to obtaining this peak t = 12 at 15 h. As a comparison with the prior art epoxy method, the same type of measurement was established on mixed bed ion exchange resins in an epoxide matrix alone.

  Samples are identical to the previous ones.

  The values obtained on two tests are represented by the curves of FIG. 2. From these two curves, the average values are derived: peak of polymerization temperature 76 C + 2 C corresponding time: 8 to 10 hours. In FIG. 3, the curve A corresponds to the average values of the two curves of FIG. 1, and the curve B corresponds to the average values of the two curves of FIG. 2. These results show a decrease in the maximum polymerization temperature of 16 C. between the epoxy cement process and the epoxide process alone. Similarly, an increase in the time at the exothermic peak of polymerization is observed.

about 5 hours.

  Of these two properties, the lowering of the peak of the polymerization exotherm is particularly sought after, since it increases the intrinsic crack of the process, especially in the case of an acceleration of the polymerization rate observed in hot weather: in this case, in fact, the kinetics of polymerization is increased, and the temperature obtained at the core of the mix must imperatively be below the temperature

water vaporization of REI.

  The use of the epoxy process -cement

solves this problem.

  Moreover, the lengthening of the curing time is an interesting phenomenon at the industrial stage because it allows possibilities

  increased intervention on the process.

  Another important advantage of the process of the invention is that it allows the coating of anionic ion exchange resins, cationic

  or in a mixed bed without the need for pretreatment.

  Indeed, the use of a hydraulic binder which releases dissociated ions into the aqueous medium avoids the prior saturation of any active sites of the cation exchange resins, since the ions released by the cement

  are able to achieve this saturation.

Claims (6)

  1 block containing contaminated ion exchange resins for storage, characterized in that the ion exchange resins are incorporated in a composite matrix consisting of a hardened epoxy resin and a cured cement selected from cements with clinker milk   and slag and ash cements.   Block according to Claim 1, characterized in that the composite matrix comprises: from 35 to 65% by weight of hardened epoxy resin and from 35 to 65% by weight of cement cured with clinker slag and / or hardened cement. slag and fly ash. 3 Block according to any one of   claims 1 and 2, characterized in that   contains up to 45% by weight of exchange resins of contaminated ions. 4 B Loc according to any of the   Claims 1 to 3, characterized in that the   Ion exchange resins are selected from cationic resins, anionic resins and mixtures thereof. Block according to any of   Claims 1 to 4, characterized in that the resin   epoxide is a hydrophilic epoxy resin.   Block according to Claim 5, characterized in that the epoxy resin is a diglycidyl ether of bis-phenol-A and / or a diglycidyl ether of hardened bis-phenol F (s) by reaction with an amine hardener.   7 Process for preparing a block according to   any of claims 1 to 5, characterized   in that it comprises the following successive steps: 1) water saturation of the contaminated ion exchange resins, 2) addition, with stirring, of the water necessary for the hydration of the cement with saturated ion exchange resins. water, 3 addition of the cement, with stirring, to the suspension obtained in 2), and 4) addition to the mixture obtained in 3) of   the epoxy resin and its hardener.