Patent Number: 046630864
Section: description

EXAMPLE 1 This example illustrates the treatment of cation exchange resins AMBERLITE IR 120 H. The resins are transferred by means of a hydroejector using demineralized water into a treatment vessel, equipped with a mechanical stirrer and a device for the ultrasonic detection of the solid-liquid interface level. After decanting the resin mixture for a period which can extend to between 24 and 48 hours, depending on whether the resins are in ball or ground form, the supernatant water is eliminated, either by pumping, or by vacuum siphoning. Complementary resin quantities are again transferred and the decanting, pumping and vacuum siphoning operations are repeated until the volume V of the decanted resins reaches 50% of the volume of the vessel. A 0.37 mol.l.sup.-1 barium nitrate solution is prepared in an auxiliary vessel and into the treatment vessel is introduced a volume V of said solution, i.e. a volume identical to that occupied by the decanted resins. This is all stirred for 2 hours. Decanting is then allowed to continue for 1 hour and the supernatant solution is eliminated by means of a pump, a vapour ejector, or by vacuum siphoning. In this case, the volume of the eliminated solution corresponds to 1.22 V, which shows that not only the pretreatment solution, but also a certain quantity of the water absorbed by the resins, is eliminated, said quantity representing 14% of the initial volume of the decanted humid resins. This operation is repeated 3 times to obtain a Ba.sup.++ saturation level of the resins close to 100%, due to the Ba(NO.sub.3).sub.2 concentration of the solution (0.37 mol.l.sup.-1) and the contacting time. The saturation treatment leads to a salting out of 10 to 15% of the initial activity of the resins. In addition, the supernatant radioactive solution is returned to the head of the liquid effluent treatment station, either upstream of an evaporator, or upstream of a chemical coprecipitation chain. Following decanting and eliminating then of the supernatant solution, the pretreated resins are washed with demineralized water also using a washing water volume equal to 0.65 V, i.e. identical to that of the pretreated, decanted resins. The pH of the resin suspension is adjusted to 7.5.+-.0.2 with the aid of a barium slurry containing 300 g.l.sup.-1 of Ba(OH.sub.2). This washing operation is repeated four times, whilst checking the NO.sub.3.sup.- concentration of the washing waters after each operation until a NO.sub.3.sup.- concentration of the washing waters below 2 g.l.sup.-1 is obtained. Thus, it is necessary to wash the pretreated resins before conditioning them in bitumen, because if the excess barium nitrate were added to the dry extract of the resins, this would have the disadvantage of increasing not only the volume of the final residue, but also of aiding the leaching of this soluble salt in water. The transfer and washing waters are very slightly radioactive and are returned to the effluent treatment station, where their degree of radioactivity was checked. The pretreated, washed resins are then resuspended in demineralized water using 0.4 to 0.45 V of water for a proportion of 0.6 to 0.55 V of the resin mixture. The suspension of the pretreated organic resins is then passed to the bituminizing installation, which is of the four screw drying extruder type. The properties of the coatings leaving the bituminizing installation are then checked. Table 1 gives the results obtained in connection with the hourly evaporation capacity of the extruder and the composition of the coating obtained during a bituminizing operation performed with resins in ball form. The swelling properties in water of the coatings obtained are then evaluated. These have been cast and solidified in the form of cylindrical test pieces with a diameter of 48 mm and a height of 90 mm. In order to determine the swelling in water, the coatings are immersed in non-renewed ordinary or demineralized water and periodically the percentage volume increase of the coatings is measured as a function of the immersion time in days. The volume ratio between the water and the coatings is 4.5 and the surface/volume ratio of the coatings 10.5 cm.sup.-1. The results obtained are given in curves 1 of FIGS. 1 and 2, which represent the volume increase percentage of the coatings as a function of the time in days. FIG. 1 illustrates the results obtained with ordinary water and FIG. 2 the results obtained with demineralized water. On the basis of these results, it can be seen that the swelling of the coatings after 365 days immersion in ordinary water is 4.2% by volume or 4.45% by weight and that it is 5.0% by volume or 5.1% by weight after 365 days immersion in demineralized water. EXAMPLE 2 Cation exchange resins AMBERLITE IR 120H are treated as in example 1, but using aqueous 1.5 mol.l.sup.-1 barium acetate solution instead of aqueous 0.37 mol.l.sup.-1 barium nitrate solution. A 1.5 mol.l.sup.-1 barium acetate solution is prepared in an auxiliary vessel and into the treatment vessel is introduced a volume V of said solution, i.e. a volume identical to that occupied by the decanted resins. The mixture undergoes stirring for 2 hours making it possible to obtain a Ba.sup.2+ saturation level of the resins exceeding 90% due to the Ba(CH.sub.3 COO).sub.2 concentration of the solution (1.5 mol.l.sup.-1) and the contacting time. Decanting is then allowed to take place for 1 hour and the supernatant solution is eliminated by means of a pump, a vapour ejector or vacuum siphoning. In this case, the volume of the solution eliminated corresponds to 1.34 V, which shows that not only has the pretreatment solution been eliminated, but also a certain amount of the water absorbed by the resins, said quantity representing 21% of the volume of the decanted humid resins. Following decanting and elimination of the supernatant solution, the pretreated resins are washed with demineralized water using a washing water volume equal to 0.83 V, i.e. identical to that of the pretreated, decanted resins. The pH of the suspension of resins is adjusted to 7.5.+-.0.2 with the aid of a barium slurry containing 300 g.l.sup.-1 of Ba(OH).sub.2. This washing operation is repeated three times whilst checking the CH.sub.3 CO.sub.2.sup.- concentration of the washing waters after each operation until a CH.sub.3 CO.sub.2.sup.- concentration thereof below 2 g.l.sup.-1 is obtained. The operation is continued as in example 1 and bituminizing is carried out under the same conditions using a blown MR 90/40 bitumen. The properties of the coatings leaving the bituminizing installation are then checked. The results obtained are given in curves 2 of FIGS. 1 and 2, which show the volume increase percentage of the coatings as a function of the time (in days) during which they were immersed in non-renewed ordinary water (FIG. 1) or in non-renewed demineralized water (FIG. 2). On the basis of FIGS. 1 and 2, it can be seen that the swelling of the coatings after 120 days immersion in ordinary water is 2.45% by volume or 3.4% by weight and that the swelling after 120 days immersion in demineralized water is 4.9% by volume of 5.0% by weight. EXAMPLE 3 In this example, as in example 1, balls of AMBERLITE IR 120H resin are treated, but using a 1.5 mol.l.sup.-1 soda solution in place on the barium nitrate solution which has the effect of bringing the resins into Na.sup.+ form. The pretreated resins are coated with MR 90/40 bitumen under the same conditions as in example 1, followed by the determination of the properties of the coating obtained as in example 1. The results obtained are given in table 1 and in curves 3 of FIGS. 1 and 2, which represent the volume increase percentage of the coatings as a function of the time in days during which they were immersed in renewed ordinary water (FIG. 1) or renewed demineralized water (FIG. 2). It can be seen from these results that the swelling of the coatings after 15 days immersion in demineralized water or ordinary water is very significant. Thus, swelling is 38.7% by volume or 25.1% by weight in the case of demineralized water and 50.1% by volume or 45.6% by weight in the case of ordinary water. Thus, in the process of the invention, the choie of salt for the pretreatment has a very significant effect on the results obtained. EXAMPLE 4 This example illustrates the treatment of anion exchange resins AMBERLITE IRN-78L. Using the operating procedure of the preceding examples, in this case use is made of AMBERLITE IRN-78L resin balls using a 1.5 mol.l.sup.-1 sodium nitrate solution and washing the NO.sub.3.sup.- -saturated resins with demineralized water until a supernatant product is obtained, whose salinity is below 2 g.l.sup.-1. The pretreated resins are coated in blown bitumen MR 90/40 under the same conditions as in the preceding examples, followed by the determination of the properties of the coatings obtained. The results obtained are given in table 1 and in curves 4 of FIGS. 1 and 2, which represent the volume increase percentage of the coatings as a function of the time in days during which they were immersed in non-renewed ordinary water (FIG. 1), or in non-renewed demineralized water (FIG. 2). The results show that the swelling of the coatings after 365 days immersion is 9.5% by volume or 6.1% by weight in the case of ordinary water and 7.2% by volume or 7.1% by weight in the case of demineralized water. EXAMPLE 5 Anion exchange resins AMBERLITE IRN-78L are treated as in example 4, but using an aqueous 1.5 mol.l.sup.-1 barium acetate solution. The operating procedure is identical to that of example 4. The results obtained with the coatings leaving the bituminizing installation are given in table 1 and in curves 5 of FIGS. 1 and 2. It can be seen that the swelling of the coatings after 55 days immersion in demineralized water is 1.7% by volume of 4.9% by weight and that swelling after 55 days in ordinary water is 1.2% by volume or 4.6% by weight. TABLE 1 __________________________________________________________________________ Evaporation capacity of Composition of the coating Suspension of AMBERLITE the extruder during Coating casting in % by weight resins in ball form, which bituminizing (in kg .multidot. h.sup.-1 temperature bitumen MR90/40 (B) have undergone bituminizing. of water) (in .degree.C.) dry extract (ES) water __________________________________________________________________________ Ex. 1 IR12OH resins pre- 160 165 54.1 (B) treatment reagent 44.4 (ES) Ba(NO.sub.3).sub.2 1.5 (H.sub.2) Ex. 2: IR12OH resins pre- 54.2 (B) treatment reagent 162 158 44.5 (ES) Ba(CH.sub.3 CO.sub.2).sub.2 1.3 (H.sub.2 O ) Ex. 3: IR12OH resins pre- 55.7 (B) treatment reagent 143 159 43.0 (ES) NaOH 1.3 (H.sub.2 O) Ex. 4: IRN-78L resins pre- 51.9 (B) treatment reagent 144 160 46.7 (ES) NaNO.sub.3 1.4 (H.sub.2 O) Ex. 5: IRN-78L resins pre- 55.6 (B) treatment reagent 147 165 43.1 (ES) Ba(CH.sub.3 CO.sub.2).sub.2 1.3 (H.sub.2 O) __________________________________________________________________________