Neutralisation method of liquid radioactive wastes of nuclear power plants contaminated with oil products, corrosion products and synthetic surface active substances in field

FIELD: power industry.

SUBSTANCE: method provides for sedimentation of waste in an initial tank with draining of contaminants from surface to an oil product sump, pre-cleaning on mechanical bulk filters with modified nitrogen-containing coals and coarse and fine cleaning microfilters, softening and demineralisation on a reverse-osmosis filter with deposition of wastes in two intermediate tanks. Filtrate of reverse-osmosis filters is supplied for additional cleaning on ion-exchange filters, and concentrate is returned to the first intermediate tank before microfilters as an alkalising reagent prior to saturation as to salts with curing of formed radioactive concentrates by introduction to Portland cement. Coals saturated with oil products are replaced with new ones, and waste ones are burnt with oil products drained from the initial tank, including ash residue in Portland cement together with waste concentrates.

EFFECT: improving strength of cement stone by 1,5-2 times and reliable fixation of radionuclides in it.

1 dwg

 

The invention relates to the field of decontamination of liquid radioactive waste (LRW) nuclear power plants (NPP), contaminated petroleum products, corrosion products, and synthetic surfactants (detergents), membrane-sorption methods.

During operation of the NPP formed LRW often have elevated contamination by petroleum products, corrosion products and detergents, which are sorbed radionuclides and their concentrations are often ten times higher than the content in the aqueous phase. [Yepimakhov V.N., Chetverikov CENTURIES, Oleinik MS and other Decontamination and preservation of vessels for storage of liquid radioactive waste // THREAD them. A.P. Alexandrov: Annual report on research and production activities. 2006, St. Petersburg., ed. LLC "SRC "Morinth", 2006, p.65-69]. While NPP, as a rule, do not have their own treatment plants and are therefore often forced to clean LRW on the mobile units in the field [Efimov A.A. Leontiev,, Yepimakhov NR. and other tech THREADS to them. Afalexander on radioactive waste management. - Scientific and technical collection "Ecology and atomic energy", 1998, spec. edition, p.40-44].

A known method of purification of liquid radioactive wastes into the field on a mobile unit, comprising a pretreatment on mechanical and ultrafilter, softening the sodium-Katie Etowah filters desalination on electrodialyzer with defending LRW in the source and intermediate containers and purification of the N+-cationite filters, followed by curing the resulting radioactive concentrates by including Portland cement [Sobolev, IGOR Timofeev E.M., Panteleyev V.I. and other Mobile plant for the treatment of mineralized low-level liquid waste. - Atomic energy, 1992, t, issue 6 s-478].

The disadvantage of this method is that when high pollution LRW oil cleanup on ultrafilter ineffective and oil clogged pores in the ion-exchange resins N+-cationite filters, removing the sorbent from the system [Pushkarev CENTURIES, YU.V. Egorov, BORIS Khrustalev. Clarification and decontamination of wastewater by flotation. - M, Energoatomizdat, 1969]

There is a method of treatment of LRW in field conditions at the facility, including pretreatment on mechanical and ultrafilter, softening and desalination by reverse osmosis filters with defending LRW in the source and intermediate containers, purification on ion-exchange filters, and curing the resulting radioactive concentrates included in Portland cement [RF Patent №2144798, bull. No. 2, 2000]. In the technological essence and the achieved technical result of this method is closest to the proposed and selected in which the quality of the prototype.

The disadvantage of this method is that when high pollution LRW oil leakage of the ultrafiltration process starts to prevent the gel polarization [Membrane Separation Processes. Ed. P. Meares. - Amsterdam: Elsevier, 1976], which requires frequent reagent leaching ultrafiltration membranes. As a result, while in an intermediate tank is formed salt of the radioactive concentrate, in the capacity of the original LRW accumulated radioactive concentrate oil and detergents. If salt concentrates the salt content of up to 150 g/l at inclusion in the Portland cement to form a durable, safe during the transportation of cement blocks, cementing received ultrafiltration concentrates petroleum products and detergents (organic content is more than 1 g/l) decrease the quality of the hardened cement compounds [Malasek E., Vojtech O. the Development of methods for solidification of radioactive concentrates. - In the book: Research in the field of disposal of liquid, solid and gaseous radioactive waste and decontamination of contaminated surfaces (proceedings of the IV scientific-technical conference of the CMEA, Moscow, 22-23 December 1976). M: Atomizdat, 1978, VIP, pp.5-20], [Komarov A., Construction materials and products. - M.: Higher school", 1971, 560 S.].

Object of the invention is to provide a method for disposal of liquid radioactive othogonality power plants, oil contaminated with corrosion products and detergents.

The technical result of the invention is to improve the reliability of fixation of radionuclides and improving the quality of the cement compounds.

To achieve the technical result in the method of treatment of LRW NPU oil contaminated with corrosion products and detergents, in the field, including pretreatment on mechanical and membrane filters, desalination by reverse osmosis filters with defending LRW in the source and intermediate containers, purification on ion-exchange filters, and curing the resulting radioactive concentrates included in Portland cement, according to the invention after the assertion of LRW in the source tank is made by draining the upper layer of water pollution in the collection of oil, when carrying out the pretreatment as mechanical filters use conventional filters with modified nitrogen-containing coals, after settling in the first interim capacity LRW serves on the membrane the filters, which use microfilters coarse and fine cleaning, then LRW sent to the second intermediate tank, after settling in the second intermediate tank LRW is directed to the reverse osmosis filters, the concentrate is returned to the first intermediate tank in cachestoreprivate reagent prior to its saturation salts, saturated oil coal extracted from the mechanical filter replace with new, and waste coals burn with the oil drained from the upper layer of the source containers in the collection of oils obtained ash include Portland cement together with saturated salts of reverse osmosis concentrate LRW.

Modified nitrogen-containing coals (MAU) compared with standard activated carbons brands BAU, AG-3, SKT has higher adsorption capacity (5-7 times higher), provide deep cleaning water from oil to 0.05 mg/kg, detergents up to 0.1 mg/kg [TU 0320-001-23363781-01].

The proposed method is illustrated by a drawing, which shows a diagram of the disposal of liquid radioactive waste from nuclear power plants, oil contaminated with corrosion products and surface-active substances in the field.

Technological scheme shown in Fig., includes: the capacity of the original LRW 1, proceedings of petroleum products 2, mechanical filter, filled MAU, 3, the first intermediate tank 4, the second intermediate tank 8, the pumps 5 and 9, the microfilters rough 6 and thin 7 purification, reverse osmosis filter 10, the ion-exchange filter 11 and the capacity of purified water 12.

The method is as follows.

LRW contaminated with oil, about what uchumi corrosion and detergents, after soaking and settling in the tank the original LRW 1 and the drain of the top layer of dirt in the collection of the oil 2 is directed to a pretreatment by gravity on the bulk carbon filter 3, downloaded, modified nitrogen-containing carbon, to remove oil, detergents and dissolved corrosion products (iron and others). The filtrate carbon filter 3 is directed to sludge in the first intermediate tank 4 and the pump 5 to the microfilters rough 6 and 7 for fine cleaning removal of suspended corrosion products. Next, the filtrate microfilters 6 and 7 are sent to defend the second intermediate tank 8 and the pump 9 on the reverse osmosis filter 10 to remove hardness salts and partial demineralization. Softened the filtrate reverse osmosis filter 10 is directed to further demineralization by ion exchange filter 11, and the concentrate is returned to the first intermediate tank 4. The filtrate ion exchange filter is sent to the capacity of purified water 12 for averaging and determining the residual specific activity and subsequent discharge. Because bicarbonate ions are in reverse osmosis filtrate (dissolved CO2virtually no delayed membranes, passing freely to the filtrate, and interacting with the water molecules, re-forms in it, the bicarbonate ions), then concentrate on ratesmortgage filter 10, doing in the first intermediate tank 4, podslushivaet (as alkaline and alkaline earth ions in the filtrate carbon filter 3 and increases the pH of the environment. This results in the settling vessel 4 to the additional release of suspended corrosion products and hardness salts, which are then displayed on the microfilters rough 6 and fine cleaning 7. Concentrate reverse osmosis filter 10, when saturated salts and radionuclides periodically withdrawn from the first intermediate tank 4 by cementing. MAU, when saturated with oil products and detergents, are extracted from the carbon filter 3 and fed to the combustion with solid combustible radioactive waste (paper, rags, cleaning materials, bad clothes) and the oil drained from the collection of petroleum products 2. Resulting ash has vodovyazushchimi properties and in the amount of 20-30% by weight of cement added to the Portland cement when cementing reverse osmosis concentrates.

In comparison with the known membrane-sorption methods of disposal of liquid radioactive waste with subsequent cementing concentrates in the proposed method polluting LRW petroleum products do not reduce the quality of the hardened cement compounds, and, ultimately, improve it, which is not obvious from the prior art. Thus,additive to Portland cement ash residue 20 to 30% by weight of cement increases the strength of cement stone in 1,5-2 times. In addition, the ash material contributes to the viscosity of the cement mixing and, consequently, reduce its porosity, i.e. improving the strength of the fixation of radionuclides.

Examples of specific performance.

Example 1. As LRW used drain water salinity (0.5 g/l) was determined by bicarbonates, sulphates and chlorides of alkali and alkaline earth metals (pH~7), contaminated with oil up to 50 mg/l, detergents (sulfone-scrap) up to 30 mg/l and suspended corrosion products, and silt up to 20 mg/liter Volumetric Σβ-activity LRW reached to 2.0×104Bq/l and was determined137Cs90Sr60Co.

The LRW decontamination was carried out as described above. As a download for a three-stage coal bulk filter used modified nitrogen-containing coals brand MAU-2A (manufactured by NPP "polichem"). In the microfilters coarse and fine cleaning of used items fiber grades EPV and all. In the reverse osmosis filter used roll of reverse osmosis membrane elements type ESPAI-4040. In a three-stage ion-exchange filter as load used cation marks KU-2 in the H+form.

Coal filters and microfilters stood no more than 5%90Sr, up to 15%137Cs and up to 50%60With. Reverse osmosis filters provided the coefficients of isdi from ∑β activity an average of about 100, i.e. at the level of desalination and ion-exchange filters - an average of more than 103. Thus, provided the total clearance from SR-radionuclides below the intervention level (cmwater) NRB-99/2009. When reaching into the reverse osmosis concentrate salt content up to 50 g/l was sent cementing. In coal filters after sorption on MAU 300 mg/d of petroleum products, radioactive waste coals were removed and sent for incineration together with the oil drained from the surface of the source container in the collection of oil, the volume of waste was reduced by several tens of times. The obtained ash was added to the Portland cement in the amount of 20-30% by weight of cement and was mixed Portland cement with reverse osmosis concentrate at a ratio equal to 1:1. Cured in 28 days cement compound satisfies the regulatory requirements of GOST R-2002 [radioactive Waste cemented. General technical requirements. - M., ed. standards, 2002, 8 S.].

Example 2. Differs from example 1 in that the content in LRW suspended corrosion products, and silt was 100 mg/L. In this case, the PA coal filters (curb MAU-2A) and the microfilters were allocated to 15%90Sr, up to 50%137Cs and up to 90%60With.

The proposed method can be implemented on the same domestic equipment, Thu is the prototype, i.e. industrially applicable. Depending on the type of contamination LRW for its removal can be used as all equipment installation, and only the necessary part.

Method of decontamination of liquid radioactive waste from nuclear power plants, oil contaminated with corrosion products and synthetic surface-active substances, in the field, including pretreatment on mechanical and membrane filters, desalination by reverse osmosis filters with the defense of liquid radioactive waste at the source and intermediate containers and purification on ion-exchange filters with curing the formed radioactive concentrates include Portland cement, characterized in that after settling of waste at the source capacity to produce discharge of the top layer of dirt in the collection of oil, when carrying out the pretreatment as mechanical filters use conventional filters with modified nitrogen-containing coals, after settling in the first intermediate capacity of liquid radioactive waste is served on membrane filters, which use microfilters coarse and fine cleaning, the waste is sent to the second intermediate tank, after settling in the second intermediate tank waste sent for Opatovicka the filters, the concentrate is returned to the first intermediate tank as alkalizing reagent prior to its saturation salts, saturated with petroleum coal extracted from the mechanical filter replace with new, and waste coals burn with the oil drained from the upper layer of the source containers in the collection of oils obtained ash include Portland cement together with saturated salts of reverse osmosis concentrate waste.



 

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