HU215199B - Method for purifying basic, oxidizing and/or acidiv reductive decontaminant solution of atomic power plant - Google Patents

Abstract

The process is used to clean alkaline alkaline oxydative and / or acidic turn-off active deco-directing decomposition decks as follows: Alkaline, oxidative de-oxidation of de-icing devices with radiant active clay radish containing sodium hydride, potassium permeate and 500-2000 kBq / dm3 of radioactive nitrogen in water at 80-150 ° C. active carbon, strongly acidic (II) main-liver replacement, strong acid hydrogens main liver cannabis replacement and heavily basic hydride oxide head liver angioplasty replacement sucker at a rate of 1 to 20 cm3 / cm2 / min, while radiative activity of the effluent is 54Mn, 60C, 110mAg for hatching heads at 1kBq / dm3 of lower value, which can be used to adjust the reagent concentration of the reagent as the starting alkaline of the next alkaline oxidative decomposition. Acid-reducing, radiant decinction of radiant dehumidifiers, radiant diatomite, which contains citric acid, oxalic acid and 500-2000 kBq / dm3 of radial active nitrogen in aqueous medium at 80-150 CC active carbon, potent hydrophobic main-liver catheter exchanger, and this primer-based hydride oxide fungus exchanger. At a rate of 20 cm3 / cm2 / min, while the radiant activity of the effluent is 54Mn, 60Co, 110mAg, it is less than 1kq / dm3, which can be used as the starting bed for acidic, ductive decinction following the setting of the rock concentration of the reagents. Autumn leaves filled with Arad active hammers are filled with radiant active substance storage and new suckers are placed in the cleaning equipment. ŕ

Description

The present invention relates to a process for the purification of alkaline, oxidative and / or acidic reductive decontamination solutions with radioactivity of 500-2000 kBq / dm ³ . The process of the present invention can be used to purify radioactive solutions formed during the decontamination of high-pressure nuclear power plants by the AP-CITROX process.

High-pressure primary circuit equipment of nuclear power plants (regenerative heat exchangers, steam generators, pipelines, pumps, etc.) is contaminated by corrosion processes and neutron radiation from the nuclear reactor core. As a result of corrosion and neutron radiation processes, corrosion layers are formed on the inner surface of the primary circuit devices (austenitic steel) and at the weld seams, which are 5iCr, ⁵⁴ Mn, ⁵ «Co," Co, 0n> Ag, ⁵⁹ Fe, ¹²⁴ Sb, ^They contain ⁹⁵ Nb of radionucleotides.

Of the former radionucleotides, the long half-life isotopes are ⁵⁴ Mn 312 days, “Co 5.26 years, HOm g g 250 days, while the short half-lives are ⁵¹ Cr 28 days, ⁵⁸ Co 71 days, ⁵⁹ Fe 45 days, ¹²⁴ Sb 60 days, ⁹⁵ Nh 66 days.

In the case of high pressure nuclear power plants (PWRs), the equipment must be decontaminated every 3-5 years.

In nuclear power plants with a high-pressure primary circuit (type PWR, VVER 400), the so-called AP-CITROX process is used for decontamination of primary circuit devices.

(A. P. Murray, Radioactive Waste Management, 79, December, 359-370, (1987)

K. Örtel, Kemenergie 28, 333 (1985).

R. Winkler, Kemenergie 12, 341 (1969).

In the AP-CITROX process, the surface to be decontaminated is first treated with aqueous permanganate solution at 90-95 ° C in an aqueous alkaline medium, and secondly with aqueous citric acid and oxalic acid at 90-95 ° C.

The resulting alkaline, oxidative, and acidic, reductive decontamination solutions are generally discharged into the radioactive liquid collection tanks without treatment. In these tanks, the short-lived isotopes decompose over a longer period of storage, but the longer half-life isotope ( ⁵⁴ Mn, “Co, ^110m Ag”) shows significant radioactivity after several years of storage and solutions cannot be channeled above 1 kBq / dm ³ .

It may also be a problem that the alkaline, oxidative and acidic, reductive decontamination solutions are often combined when a manganese dioxide precipitate is formed due to the oxalic acid permanganate reaction, which settles as radioactive sludge in the storage tank. This radioactive sludge is difficult to handle during subsequent purification of the radioactive solution.

It is also problematic that alkaline, oxidative decontamination solutions, in particular, contain many undesirable organic compounds (oils, fats, surfactants, detergents, etc.), as well as solid particles and colloidal impurities, which are radioactive nuclides. carriers ".

In nuclear power plants, these solutions are currently concentrated by evaporation. The concentrate, or the radioactive material obtained by evaporation to dryness, may have to be placed in a new repository, or the radioactive waste may be stored by cementation, bitumen or vitrification.

Perhaps the most important of the problems raised above is the long-term solution of storage as radioactive liquid, as the volume of stored radioactive liquids in nuclear power plants is increasing during their lifetime.

Purification of alkaline-oxidative and acidic reductive decontamination solutions in power plants of the VVERN00 type is not yet solved. It is an object of the present invention to provide a process which allows the radioactive alkaline, oxidative and acidic, reductive decontamination solutions to be processed at the site of production by concentrating the radioactive materials to a minimum volume and simultaneously purifying the aqueous phases so that they should be reused in the next decontamination step after the reagent concentrations have been adjusted.

For the first time in our research and development work we focused on the purification of concentrated alkaline-oxidative decontamination solutions. The columns containing the highly acidic cation exchanger (Vari40 on-KSN) and the strongly basic anion exchanger (see Tables 1, 2 for measurements PAV / KL / 1, PAV / KL / 2) obtained extremely low bulk density characteristics (PAV / KL / 1 Mn = 1.8, PAV / KL / 2 Mn = 7.8 at both 15 ° C and 95 ° C.

Table 1. Measurement results for PAV / KL / 1

Vol. cm ³ cr ppm Mn ppm K pPM So pPM pH Cond. pictures. pS 15 - - - 7 2.70 30 - - - 7 3.66 45 - - - 3.33 7 3.20 60 - - - 3.33 7 3.65 75 - - - 3.33 7 14.50 90 - 2.35 1.43 3.33 6 27.0 105 - 4.90 1.79 3.33 6 41.0 120 1.46 47.10 4.29 3.33 3 245

HU 215 199 Β

Table 1 (continued)

Vol. cm ³ cr pPM Mn pPM K pPM So pPM PH Cond. pictures. gS 135 5.89 217 5.36 3.33 2 1810 150 15.45 920 47.0 1.67 1 - 165 17.70 583 22.0 3.33 1 - 180 18.64 833 42.0 3.33 1 - Ag concentration cannot be measured Column: D = 1 cm, L = 64 cm 43.5 cm ³ H ⁺ Varion KSN, 6.5 cm ³ OH- Varion ATN Feed rate: 2 cm ³ / min, temperature 15 ° C Input solution: KMnO ₄ NaOH 5 g / dm ³ 10 g / dm ³ K ₂ Cr ₂ O ₇ AgNOj 30 mg / dm ³ 17 mg / dm ³ Na = 5750 ppm. Mn = 1740 ppm. K = 1230 ppm Ag = 10 ppm Cr = 10ppm

Table 2 PA V / KL / 2 measurement results

Vol. cm ³ cr pPM Mn pPM K pPM So pPM pH Cond. pictures. pS 15 - - - - 7 7.9 45 - - - - 7 4.9 75 - - 0.71 - 8 87.2 105 - - - - 8 154.2 135 - - - - 8 212 165 - - - - 7 226 195 - - - - 7 214 210 - - - 3.33 7 250 225 - - 100 - 11 250 240 - - 156 2090 11 - 255 - - 212 5000 11 - 270 0.99 - 475 - - - 285 2.16 - 850 7000 - - 300 8.22 - 965 - 11 - 315 17.7 - 1046 7182 11 - 345 45.0 - 1120 7364 - - 390 47.7 3.41 1166 - - - 405 38.5 12.3 1173 7364 - - 435 27.0 73.3 1193 7182 - - 465 17.7 85.0 1200 7182 - - 495 13.1 150.0 1200 6273 - - Ag concentration at 360-390 volumes approx. 0.5 ppm, not measurable in other samples Column: D = 1 cm L = 64 cm 43.5 cm ³ H ⁺ Varion KSN, 6.5 cm ³ OH- Varion ATN Feed rate 2 cm ³ / min, temperature 90 ° C Input solution: KMnO ₄ NaOH 5 g / dm ³ 10 g / dm ³ K ₂ Cr ₂ O ₇ AgNO, 30 mg / dm ³ 17 mg / dm ³ Na = 5750 ppm K = 1230 ppm Mn = 1740 ppm Ag = 10 ppm Cr = 10 ppm

HU 215 199 Β

The work was then continued by placing an activated carbon layer in front of the ion-exchange layers and first making room temperature measurements.

Although the experiments were designed and executed with great care, the bulk density data (volume concentration: breakthrough volume / column volume) and decontamination factors (decontamination factor, DF: inlet activity / outflow activity) proved to be extremely unfavorable, for long half-lives of ⁵⁴ Mn, ⁶⁰ Co and ^{|| Om} Ag isotopes (DF = 2-3, bulk density 1-10) for room temperature experiments. Adsorption equilibria generally change in an unfavorable direction with increasing temperature, so that the beneficial effect of the higher temperature employed in the process of the present invention has been recognized as an unexpected effect on the process. By increasing the temperature of the purification operation, the decontamination factor and the bulk density values are significantly increased when purifying alkaline, oxidative radioactive decontamination solutions. In particular, the cleaning effect was enhanced above 80 ° C.

Thus, the novel phenomenon we have discovered, an unexpected effect, is that purification of alkaline, oxidative radioactive decontamination solutions can be accomplished more advantageously by adsorption and ion exchange at 80-150 ° C, preferably 90-95 ° C directly from the decontamination process. after operation, as at room temperature. Our new discovery makes it possible to purify the highly contaminated alkaline oxidative decontamination solution (mechanical impurities, radioactive colloids, oil, fat, surfactant, detergent, radionuclides) to such an extent that the purified liquid can be reused for the next decontamination process after adjusting reagent concentrations.

Accordingly, the present invention provides a process for purifying alkaline-oxidative aqueous decontamination solutions containing 500-2000 kBq / dm ³ of aqueous decontamination solutions containing sodium hydroxide, potassium permanganate and / or acid-reductive citric acid, oxalic acid. For the solution obtained by alkaline oxidative decontamination, activated carbon, a strongly acidic iron (II) cation exchanger, a strongly acidic hydrogen cation exchanger and a strongly basic hydroxide anion exchanger (3.5-5.5) :( 0.5-1 , 5): (0.5-1.5) :( 0.5-1.5) by volume, in the case of a solution obtained by acid-reductive decontamination, activated carbon, a strongly acidic hydrogen cation exchanger and a strongly basic hydroxide form run the columns to be purified on a column containing anion exchanger (0.5-1.5) :( 2-3.2) :( 1-1.6) at a rate of 1-20 cm ³ / cm ² -minutes. The column solutions are used as the starting solution for the next decontamination after adjusting the reagent concentration.

The new, recognized process for purifying elevated temperature alkaline, oxidative, radioactive decontamination solutions is extremely fast and economical. The process achieved 500-2000 decontamination factors for long-lived isotopes with a bulk density of 50-150. The total effluent activity of the alkaline, oxidative, radioactive decontamination solution is less than 1 kBq / dm ³ for ⁵⁴ Mn, ⁶⁰ Co, ^110m Ag, and the purified solution can be reused once the reagent concentrations have been adjusted in another decontamination operation. The operation time can be set to 2-8 hours by appropriately dimensioning the adsorption, ion exchange purification unit, which also corresponds to the operational decontamination operation time.

For acidic, reductive, radioactive decontamination solutions, the cleaning characteristics (DF and bulk density data) are less sensitive to temperature changes. However, in this case, too, at 80-150 ° C, preferably at 90-95 ° C, very favorable operating characteristics (DF = 500-2000, volume concentration 50-150) are obtained at the decontamination temperature. Accordingly, purification of acidic, reductive, radioactive decontamination solutions results in a 1 kBq / dm ³ effluent activity for the long half-life of ⁵⁴ Mn, ⁶⁰ Co, uomAg.

The purified acidic, reductive, radioactive decontamination solution contains almost all the original citric acid and oxalic acid. The purified solution can be reused in the decontamination process after the addition of citric acid, oxalic acid. Direct recirculation purification can also be accomplished by acidic reductive decontamination. As a result, the decontamination processing time can be shortened, and the decontamination factor for nuclear power plants is improved, since radioactive components are always removed from the decontamination fluid.

The following examples illustrate the process of the present invention.

Example 1

An alkaline oxidative nuclear decontamination solution, the composition of which is given below, is passed through a column of 300 cm long and 5.5 cm inside diameter at a flow rate of 200 cm ³ / min (8.4 cm ³ / cm ² min) at 95 ° C, from top to bottom in the same proportion as the feed, Top-Sorb Activated Carbon with a particle size of 1-3 mm in length 180 cm (Bioflokk Ltd., University of Veszprém), Varion-KSN in the form of iron (II) with a particle size of 0.4-1.2 mm Contains cation exchange resin 40 cm in length, 0.4-1.2 mm Hydrogen form Varion-KSN cation exchange resin, and 40 cm 0.4-1.2 mm particle size hydroxide form Varion-ATN anion exchange resin (Nitrochemical Industrial Plant Balatonfűzf.).

Chemical composition of the incoming aqueous phase alkaline oxidative decontamination solution

HU 215 199 Β

Composition of KMnO ₄ 5 g / dm, NaOH 10 g / dm ³ radionuclide in kBq / dm ³

5'Cr ⁵⁴ Mn ⁵⁸ Co. "Co 1 1 Onty \ g ¹²⁴ Sb ⁹⁵ Nb Σ 82 15.4 2.9 1.6 520 77.7 230 929.6

Leaving radionuclide compositions, kBq / dm ³

Volume dm ^{3 51} Cr ^S4 Mn ⁵⁸ Co. "Co 1 lOm ^ g ^{, 24} Sb ⁹⁵ Nb ⁵⁴ Mn ^s + ⁶⁰ Co + 1 lOmy ^ g 24 0.22 0.08 0.04 0.24 0.26 1.02 0.04 0.58 57 0.4 0.16 0.1 0.36 0.38 1.94 0.12 0.90 77 0.56 0.08 0.06 0.16 0.52 4.8 0.12 0.76 93 0.58 0.06 0.06 0.14 0.16 5.4 0.08 0.36 113 1.16 0.02 0.06 0.12 0.1 6.78 0.06 0.24 136 1.76 0.08 0.08 0.22 0.28 8.06 0.08 0.58 152 3.56 0.16 0.24 0.22 0.30 10.46 0.44 0.68 173 3.24 0.14 0.22 0.24 0.16 10.74 0.36 0.54 Entering solution 82 15.4 2.9 1.6 520 77.7 230 537 DF * 110 6.6 3250 994.4

Input solution Exit solution 173 dm ³

Site radionuclide composition at 173 dm ³ throughput, kBq / dm ³

Space cm load ⁵ 'Cr ⁵⁴ Mn ^S8 Co "Co llOmAg ¹²⁴ Sb ⁹⁵ Nb ⁵⁴ MiAt- Co + 110mAg 0 ACE. 82 15.4 2.9 1.6 520 77.7 230 537 30 ACE. 82 15.4 2.9 1.6 520 77.7 230 224.5 60 ACE. 16 3.8 1.3 0.7 220 16.9 124 21.4 90 ACE. 7.2 1.9 0.6 0.8 35 15.3 20 37.7 120 ACE. 3.4 0.14 0.24 0.24 0.55 13.3 0.42 0.93 150 ACE. 3.58 0.16 0.28 0.14 0.12 13.3 0.42 0.42 180 ACE. 3.82 0.16 0.26 0.24 0.18 12.9 0.50 0.58 210 I. CS. Fe ²⁺ 3.22 0.16 0.24 0.30 0.22 9.8 0.42 0.68 240 I. CS. H ⁺ 3.18 0.12 0.22 0.14 0.28 10.2 0.38 0.54 270 I. CS. OH 3.28 0.16 0.2 0.22 0.34 U 1 0.36 0.72 300 I. CS. OH 3.24 0.14 0.22 0.24 0.16 10.74 0.36 0.54 DF * 999.4 Volumetric compression ** 60.7

Entering solution

173 dm ^{3 of} outlet solution ** (assuming a column length of 120 cm, with radioactivity of 0.93 kBq / dm ³ )

Example 2

Acidic Reductive Nuclear Decontamination Solution - Composed at a volume of 200 cm ³ / min [8.4 cm ³ / (cm ² min)] at a temperature of 95 ° C below, in a 150 cm long column having an internal diameter of 5.5 cm, Top-Sorb-Rod Activated Carbon (Bioflokk Kft., University of Veszprém), length 80 cm

Hydrogen-shaped Vari5 with a particle size of 0.4 to 1.2 mm

HU215 Contains a 199Β on-KSN cation exchanger containing 40 cm long Varion-ATN anion exchange resin (Nitrochemical Industry, Balatonfűző) in the form of hydroxide particles of 0.4-1.2 mm particle size.

The chemical composition of the incoming aqueous phase acidic reductive decontamination solution is 10 g / dm ³ citric acid, 10 g / dm ³ oxalic acid.

radionuclide composition in kBq / dm ³

⁵¹ Cr ⁵⁴ Mn ⁵⁸ Co. ⁶⁰ Co. 1 lOm ^ g ¹²⁴ Sb ⁹⁵ Nb Σ 38 280 280 940 107.6 14.5 46.8 1706.9

Exit radionuclide compositions k Bq / dm ³

Volume dm ^{3 51} Cr ⁵⁴ Mn ⁵⁸ Co. ⁶⁰ Co. 1 lOmy ^ g ^'24 Sb ⁹⁵ Nb ⁵⁴ Mn ^z + ⁶⁰ Co + llOmy ^ g 18 3.26 0.18 0.26 0.39 0.32 0.66 0.43 0.76 38 1.36 0.06 0.08 0.1 0.1 9.2 0.08 0.26 55 4.46 0.18 0.26 0.34 0.44 15.4 0.5 0.96 73 1.88 0.04 0.08 0.08 0.08 13.1 0.1 0.20 89 4.48 0.18 0.32 0.36 0.30 15.3 0.56 0.84 106 5.1 0.22 0.34 0.36 0.40 14.7 0.54 0.98 126 6.7 0.22 0.4 0.4 0.3 15.9 0.90 0.92 Entering solution 38 280 280 940 107.6 14.5 46.8 1327.6 DF * 1272 2350 360 1443

Inlet solution 126 dm ³ outlet solution

Stationary radionuclide composition at 126 dm ³ flow rate, kBq / dm ³

Space cm load ^5l Cr ^S4 Mn ^5S Co ⁶⁰ Co. 11 OmAg ^l24 Sb ⁹⁵ Nb ⁵⁴ Mn ^s + ⁶⁰ Co + U0mAg 0 ACE. 38 280 280 940 107.6 14.5 46.8 1327.6 30 ACE. 36 330 382 918 67 16.2 6.9 1315 60 I. CS. H ⁺ 2.9 0.1 0.14 0.2 4.8 13.9 0.6 5.1 90 I. CS. H ⁺ 2.4 0.08 0.12 0.22 0.44 13.8 0.5 0.74 120 I. CS. OH 2.2 0.06 0.1 0.08 0.5 13.4 0.4 0.64 150 I. CS. OH 6.7 0.22 0.4 0.4 0.3 15.9 0.9 0.92 DF * 1443 Volumetric compression ** 58.3

Entering solution

126 dm ³ effluent solution ** (assuming a column length of 90 cm at radioactivity of 0.74 kgBq / dm ³ )

Claims (1)

A process for purifying aqueous decontamination solutions of alkaline oxidative, sodium hydroxide, potassium permanganate and / or acid-reductive citric acid, oxalic acid with radioactivity of 500-2000 kBq / dm ³ , characterized in that it is obtained by alkaline oxidative decontamination at 80-150 ° C. activated carbon, preferably an acidic iron (II) cation exchanger, a strongly acidic hydrogen cation exchanger and a strongly basic hydroxide anion exchanger (3.5-5.5): (0.5-1.5) :( 0.5-1.5) :( 0.5-1.5) by volume, in the case of a solution obtained by acid-reductive decontamination, activated carbon, a strongly acidic hydrogen cation exchanger and in the form of a strongly basic hydroxide Transfer the solutions to be purified to a column containing 5 anion exchangers (0.5-1.5) :( 2-3.2) :( 1-1.6) at a rate of 1-20 cm ³ / cm ² · min, and the solutions leaving the columns after adjusting the reagent concentration, it is used as a starting solution for the next decontamination.