Method of purification of liquid waste from nuclear power plants
(57) Abstract:The invention relates to the field of nuclear technology, and in particular to methods of treatment of liquid waste from nuclear power plants (NPPs). The inventive method for processing liquid radioactive waste (LRW) of nuclear power plants involves the evaporation of LRW in evaporators, cooling condensate secondary steam, purification and desalting of its filters. Part of desalinated condensate unbalanced water - concentrate, repeatedly passing it through evaporative cooling tower and heat exchanger, and remove the radionuclides in the system by-pass cleaning. As a heat exchanger using the secondary steam condensers and coolers native plants for the processing of liquid radioactive waste, and as a system bypass purification using standard system processing of LRW. This method helps to improve the environmental situation in the area of NPP, as it prevents the release into the environment of a significant number of radionuclides. 2 C.p. f-crystals, 1 tab., 2 Il. The invention relates to the field of nuclear technology, in particular to the processing of liquid waste from nuclear power plants (NPP), and can be used at ut consisting of drain waters (organized leakage of main and auxiliary equipment, water rooms and air locks plum laboratories, plums from floor washing and decontamination of premises), the solution from the regeneration and washing the ion exchange and carbon filters, water reclamation and regeneration of upstream perlite filters, water hydraulic waste ion-exchange resins and filter perlite, waste solutions from decontamination and cleaning of equipment and pipelines, water hydraulic testing and pressure testing of equipment and pipelines, waste water Laundry. Generated liquid waste sent for recycling, which consists of evaporation in the evaporator, DiaryOne condensate in the deaerator, clean condensate from oil to coal and alluvial perlite filters, further deep demineralization by ion exchange filters (1, page 127; 2, pp. 135-168). VAT residue evaporators with salinity 300-400 g/DM3sent for temporary storage and further processing, which may be in his bitumirovannaya, cementation, vitrification and getting salt water. Demineralized condensate, as appropriate make-up water reactor, re-use for different needs NPP recharge circuits of nuclear power plants, cooking regen is ecocide and other own technical needs. The resulting demineralized condensate has a conductivity of not more than 0.1 µs/cm, pH of 7.0, the content of hardness salts is not more than 0.2 ág-EQ/kg, the chloride ion is not more 4-50 mg/kg (3, page 34; 4, page 192). As part of LRW is formed by contact of potable and technical water, the amount of desalinated condensate exceeds the demand for their own needs. The difference between the actually received amount of demineralized condensate and the need for their own needs is called unbalanced water.Discharge of effluents into water bodies, including the seas and oceans is practiced all over the world (5, pages 66-74). When the discharge of unbalance waters into water bodies, commercial, fishing, fish breeding purposes and recreational uses the term "valid reset" individually defined for each plant in the feasibility study of the project. Territorial environmental agencies in coordination with the sanitary and epidemiological supervision shall be approved by the project emissions and discharges of radioactive substances and issued the opinion and the dose according to the quota that can be allocated to this NPP with regard to the current radiation environment and radiation vazdeistva the project and during the operation of NPP radiation doses to the critical group of the population should not exceed 5% of the set NRB-76/87 (6, pages 9-10). However, the specific radioactivity in the water discharged can be set significantly lower than the DKbregulated by the Norms of radiation safety (7). This approach is completely fair, because when released into water is the concentration of radionuclides:
- foam - 100-10000 times;
phytoplankton 500-75000 time;
green algae - 800-50000 time;
- insect larvae - 100-100000 time;
- fish - 100-30000 time;
(5, page 61-65; 8, pp. 25-42). Thus, to reduce the effects of radiation hazardous facilities on the population it is necessary to minimize produce discharges. During prolonged operation of the NPP as a result of physical deterioration of the equipment increases the number of technical water leaks, leak-in capacitors, respectively, and cycles of regeneration of ion-exchange filters. As a result, the number of the resulting unbalanced water can exceed the design value, and the intake of radionuclides into the hydrosphere may exceed the value of a valid reset. Practice shows that the amount of unbalance waters to reduce almost impossible, and, as a rule, they increase with increasing age of the plant and the degree of wear of the equipment.The disadvantage of the nearest analogue is all contained in unbalanced water radionuclides in the environment, and useless loss of demineralized condensate.The problem solved by the invention is to increase the level of treatment by reducing the release of radionuclides into the environment and the useful life of unbalance NPP.The invention consists in that in the method of purification of liquid radioactive waste from nuclear power plants, including the evaporation of liquid radioactive waste from NPPs in evaporators, cooling condensate secondary pen, purification and desalting of its filters, it is proposed to concentrate part of desalinated condensate unbalanced water, repeatedly passing it through evaporative cooling tower and heat exchanger, and to remove the radionuclides in the system by-pass cleaning. As the heat exchanger is proposed to use the secondary steam condensers and coolers standard installation the key of liquid radioactive waste. Under certain conditions, can be applied system-pass cleaning, consisting of complex mechanical, sorption and ion-exchange filters.The novelty of the method lies in the fact that when the cooling water in the cooling tower part of it evaporates and enters the atmosphere without boiling, and there is no evaporation of radionuclides as they are in the form of salts dissolved in water. This leads to an increase in the concentration of radionuclides in the circulating water to values at which it becomes possible to select a portion of the circulating water to the bypass cleanup and catch part of the radionuclides with the organization of effective radiometric control over the process. In this case, the radionuclides are removed from the circulating water and the composition of the cubic residue evaporators or regenerated ion exchange filters are sent for further processing together with other LRW NPP. To implement the method on NPP organize local system circulating water quench, including: requiring cooling water heat exchanger, cooling tower and bypass system circulating water purification. As requiring cooling water heat exchanger, it is advisable to use conden the key selected based on the annual amount of the resulting unbalance waters, namely, the consumption of heating steam in the evaporation apparatus should approximate the value of the evaporating water in the cooling tower. As the tower should only be used evaporative cooling tower, cableone which does not exceed 0,1-0,01%. They are modern film or ducted evaporative cooling tower is equipped with an effective vodoulaviteli (9, page 81). Bypass the cleaning may be performed sequentially includes: a mechanical filter, sorption filter, ion exchange filters or filters with selective sorbent for the radionuclides of cesium, for example, on the basis of ferrocyanides Nickel, iron, copper, based teroxide zirconium, or any other high-performance zeolite. Also as a system bypass the cleanup, you can use native system LRW processing, with cooling of circulating water should be directed to the evaporation together with LRW. When implementing this method is limited to the discharge of unbalance of water in the hydrosphere, decreases the release of radionuclides into the environment, which in this case is determined only by Kaplunov in the tower. In the bypass system cleaning captured, removed from circulation and sent to the cooled equipment. The use of cooling towers in the technique is known, for example, to create systems of circulating water cooling, designed to save cooling service water (9, 10). Here the evaporation and concentration of impurities in the circulating water plays a negative role, and are accepted, measures aimed at their elimination. So use a radiator-type cooling tower and air cooling units, in which there is no evaporation of the circulating water, as in systems with evaporative cooling towers to reduce salinity produce a periodic refresh (purge) circulating water reset it in water or use for technical purposes, after which it also gets into the environment (9, page 83; 10, page 114, 164, 183). In the proposed method cannot be used sprinkling swimming pools open, tower fan cooling tower with sprinkling or drip irrigation, coolers, cableone which can reach 2-3%. You can use evaporative film or ejection evaporative cooling tower is equipped with an effective vodoulaviteli, cableone which does not exceed 0,1-0,01%. Evaporation and concentration of radionuclides in the proposed method plays a positive roldy and the possibility to control the cleaning process. Here the tower is new for her as as an evaporator and steam separator conventional evaporation apparatus.The cooled circulating water heat exchanger in this comparison is made heating chamber conventional evaporation apparatus. It determines the performance of the system by the number of recyclable liquid waste from NPPs (unbalanced water) and has the ability to change the heat load in accordance with demand at the moment, because the amount of unbalance of water is not constant in time and may vary depending on the time of year, carried out planned repairs and the availability of emergency situations. Use as require cooling water heat exchanger, condensers and chillers evaporators system LRW processing is preferable because it easily allows you to change the heat load by reducing or increasing the flow rate of the heating steam in the evaporation apparatus. Unlike used in the technique of purging of circulating water in the cooling system with the tower is proposed to use the bypass system circulating water purification from radionuclides. This is possible because of the very low content of salts in PTS who.Examples of specific performance 1 and 2 can be seen in Fig. 1 and 2.LRW NPPs (Ref.1) served in the evaporators for evaporation (POS.2). This process consists of: VAT residue (Ref.9), which is then sent to the storage and processing (Ref. 10), and the secondary steam condensate in the condenser evaporator (POS.3). For diversion released during condensation of steam heat in the tube space of the condenser serves cold water (Ref. 11), and exits the condenser hot water (Ref.12). The secondary steam condensate is then cooled in the refrigerator (POS.4), where the removal of heat serves cold water (Ref.11), and remove with warm water (Ref. 12). The cooled condensate is fed into the system (Ref.5) mechanical, sorption, ion exchange filters, etc. for the removal of oils, surfactants and salts. Received demineralized condensate is directed to the needs of the NPP, which is 70-90% of the total number (POS.8), and 10-30% of its total number is unbalanced water (Ref. 7). Because of unbalance the water is warm, it serves for feeding in film evaporative cooling tower where it is cooled (POS.13) and mixed with the General flow of the chilled water. The cooling is should be disconnected from supply water. Exhaust of them heated water (Ref.15) is directed to a cooling tower (Ref.13). When multiple water circulation along the contour and its evaporation: the tower (Ref.13) - chilled water (Ref. 14) - heat exchangers requiring cooling water (Ref. 3 and 4) - heated water (Ref.15) - the tower (Ref.13), is the concentration of radionuclides and the conditions for their capture and removal. In the specific example 1 (Fig.1), where the system bypass purification using existing NPP system processing of LRW of the circulating water is taken, mixed with other LRW NPPs (Ref.1) and in the General flow is directed to the evaporation (POS.2). During this process, the amount of unbalance of water (Ref.7) is increased by the value selected on the bypass water treatment. In the specific example 2 (Fig.2), where the bypass system cleaning using mechanical, sorption and ion-exchange filters, part of the chilled water (Ref.14) is directed to filters (Ref.16) and after purification is mixed with a flow of heated water (Ref.15). Removal of radionuclides is periodically regenerated, leaching waters and water opening at the time of recovery filters or in conjunction with amrabat what should be evaluated on the example of Leningrad NPP, given the following specific data:
specific radioactivity of the purified condensate is ANDd=510-11Ku/DM3;
- the amount of unbalance of water 80,000 to m3/year;
- the required performance of the disposal system for liquid waste (unbalanced water) Gd= 10 m3/h;
the water quality after bypass cleaning matches the quality of the purified condensate;
- the flow to the bypass clearance Gbm3/h;
specific radioactivity circulating water of AaboutKu/DM3;
- capacity circulating water Gabout= 1000 m3/h;
- loss of circulating water with Kaplunov, Gash= 0,01-0,1% of the performance for circulating water 1000 m3/Gash/ 100% = 0,1-1 m3/h;
The efficiency of the proposed method can be evaluated by the ratio of quantity of output from the system of radioactivity to the amount of radioactivity received for processing:
Eff.%=Gb(Aabout-Ad)100% / Ad(Gd+Gb);
The value of Aaboutcan be found from the balance equation of radioactivity:
510-11Ku/DM31000 DM3/m3(10 m3/h+Gb)=AaboutKu/DM3DM3/m3Yu cleaning 2% of the performance of the disposal system for liquid wastes (Ref.2) you can talk about the marked effectiveness of the proposed method, here is removed 15-60% of radioactivity. With further increase of the flow rate in the bypass clearance 5, 10, 20, 50, 100% (POS. 3, 4, 5, 6, and 7) the efficiency increases to 98%. This means that the number of radionuclides in relation to the original is captured in the system processing and misses in the environment, unbalanced water is not discharged into the hydrosphere of the region, and is effectively used for cooling of existing equipment. The flow in the bypass clearance less than 2% cannot be applied due to the low efficiency of the system, and over 100% impractical because of the adequacy of the obtained effect.The proposed method can be implemented using produced by domestic industry equipment. It allows to increase the degree of purification and to prevent release into the environment of a significant part of the radionuclides, which contributes to the improvement of the ecological situation in the area of NPP. The economic effect is achieved by reducing failure of heat exchangers, due to lower corrosion by cooling it demineralized condensate.REFERENCES
1. Nuclear power, people and the environment / Babayev Kopylov, E. I. Verkhovsky. Sphecodogastra in nuclear power plants: M.: Vysshaya SHKOLA, 1988. - 208 S.3. Clean water nuclear power plants / Kul L. A., Fears, E. B., Voloshinov A. M., and others, Kiev, Naukova Dumka, 1979, 209 S.4. Nuclear power station. Textbook for higher education in the specialty "Nuclear power plants and installations" / Margelov T. H., M., "Higher school", 1974, 359 S.5. Purification of contaminated water laboratories and research nuclear reactors. Ed. 3rd, revised and expanded/ Janicevic A. A. Atomizdat, 1974, 312 S.6. Rules and regulations in the nuclear industry. Sanitary rules of design and operation of nuclear power plants (SP-AC-88/93)/2-nd edition, revised and expanded, 1993, 85 S.7. Radiation safety standards. NRB 76/87. Annex 2.8. Fundamentals of water purification from radioactive contamination / Kuznetsov, Y. C., Sepetkovski Century. N. , Trusov, A. G., Ed. Corr.-cor. The USSR Academy of Sciences C. M. Vdovenko, ed. 2-e, Perera. and additional, M., Atomizdat, 1974, 360 S.9. Belichenko Y. P. Closed water system chemical industries. M.: Chemistry, 1990, 208 S.10. Shabalin, A. F. the Circulating water supply for industrial enterprises. M, stroiizdat, 1972, 296 S. 1. The way to cleanse demineralization it on the filters, characterized in that the part of desalinated condensate unbalanced water - concentrate, repeatedly passing through the film evaporative cooling tower and heat exchanger, and remove the radionuclides in the system bypass cleanup.2. The method according to p. 1, characterized in that as a heat exchanger using the secondary steam condensers and coolers standard installation processing of liquid radioactive waste.3. The method according to p. 1, characterized in that the bypass system cleaning use a standard system for processing liquid radioactive waste.
FIELD: atomic power; liquid A-wastes processing.
SUBSTANCE: the invention is pertaining to the field of atomic power, in particular, to the liquid A-wastes processing. The invention contains: a device for neutralization of the liquid A-wastes of low and medium level radioactivity, which contains an upright located vaporizing container placed inside a ring-type tank. The vaporizing tank has a heater located in its middle part and louvered deflectors and a branch pipe of a condensate withdrawal - located in its upper part. The vaporizing tank is made in the form of the shut funnel with its narrow part directed downward. The bottom of the shut funnel represents a replaceable cylinder with a sorbent and is placed inside the second heater. The ring-type tank having a branch pipe to feed the processed solutions is connected to the vaporizing tank by a pipeline with a pressure-relief valve. Advantage of the invention is an improved efficiency of water purification.
EFFECT: the invention ensures improved efficiency of water purification.
FIELD: ecology; methods of environmental protection.
SUBSTANCE: the invention is pertaining to methods of environmental protection, in particular, to the method of effectivization of localization of the porous surfaces polluted by radioactive substances. The invention presents the method of effectivization of localization of the porous surfaces polluted by the radioactive substances ensuring deposition of the film-forming substances on the porous surfaces polluted by radioactive substances. Before deposition of the film-forming substances on the subjected to localization porous surfaces contaminated by the radioactive substances they are wetted with water or a surfactant solution to increase the thickness of the applied localizing film. Advantages of the invention consist in the increased efficiency of localization of the radioactive contaminations. The invention ensures increased efficiency of localization of the radioactive contaminations.
EFFECT: the invention ensures increased efficiency of localization of the radioactive contaminations.
2 tbl, 2 ex
FIELD: technology of handling of the liquid nuclear wastes of the nuclear fuel and power cycle; methods of reprocessing of the liquid nuclear wastes.
SUBSTANCE: the invention is pertaining to the procedure of the liquid nuclear wastes handling of the nuclear fuel and power cycle and may be used during reprocessing of the liquid nuclear wastes (LNW). The method includes the preliminary concentration, ozonization, microfiltration of the vat residue with fractionation of the permeate and the concentrate and the ion-selective purification of the permeate using the ion-selective a sorbent. At that the microfiltration is conducted at least in two stages: the permeate of each previous stage of the microfiltration is directed to the microfiltration as the source solution for the subsequent stage of the microfiltration, and at the final stage of the permeate from the microfiltration is sent to the utilization. The concentrate produced at each next stage of the microfiltration is mixed with the source solution of the previous stage of the microfiltration. The concentrate produced at the first stage of the microfiltration is directed to the conditioning and dumping. The ion-selective sorbent is added in the permeate of the previous stage of the microfiltration before the final stage of the microfiltration. The invention ensures: reduction of the volume of the liquid nuclear wastes due to the deep purification of the LNW with the high saline share from the radionuclides and extraction of the radionuclides in the compact form of the sparingly soluble compounds at the corresponding increase of the factor of purification of the salts extracted at the stage of the vat residue treatment; reduction and optimization of the consumption of the permeate and concentrate interacting with the source solution as well as produced at the further stages.
EFFECT: the invention ensures: reduction of the volume of the liquid nuclear wastes; the deep purification of the LNW with the high saline share from the radionuclides and extraction of the radionuclides in the compact form of the sparingly soluble compounds at the corresponding increase of the factor of purification of the salts extracted at the stage of the vat resudue treatment; reduction and optimization of the consumption of the permeate and concentrate interacting with the source solution ands produced at the further stages.
FIELD: handling nuclear fuel wastes.
SUBSTANCE: proposed method for evaporating highly active raffinate produced in recovery of irradiated nuclear fuel incorporating molybdenum, zirconium, and other fissionable products includes raffinate evaporation in oxalic acid still solution at zirconium concentration below 5 g/l.
EFFECT: enhanced safety and economic efficiency.
2 cl, 4 ex
FIELD: physics; nuclear technology.
SUBSTANCE: present group of inventions pertains to treatment of liquid radioactive wastes, and particularly to methods of concentrating, drying and solidifying an evaporate concentrate. The method of treating liquid radioactive wastes involves concentrating wastes through evaporation at 105-150°C by adding glycerine to liquid radioactive wastes, at ratio of 1:9-1:1 in the evaporation zone. A glycerine evaporate concentrate is obtained from the process of concentrating liquid radioactive wastes. This concentrate is subjected to thermal treatment at 150°-200°C. The glycerine concentrate formed as a result is returned to the liquid radioactive wastes treatment cycle. The porous anhydrous salt product obtained after distillation of glycerine is solidified by adding portions of a binding substance to it until formation of a homogenous in situ block. After adding each portion of binding substance, the product is cooled to 85°-95°C. The next portion of binding substance is added after heating the product to 105-150°C. The proposed group of inventions is aimed at simplifying the technology of neutralisation of liquid radioactive wastes, reduction of the amount of glycerine used when concentrating the wastes, and improving the environmental situation at places of permanent disposal of radioactive wastes.
EFFECT: simplification of the technology of neutralisation of liquid radioactive wastes, reduction of the amount of glycerine used when concentrating the wastes, and improvement of the environmental situation at places of permanent disposal of radioactive wastes.
3 cl, 1 tbl
SUBSTANCE: method of reprocessing radioactive ion-exchange resin, including thermal treatment of ion-exchange resin in steam-heated apparatus and curing undecomposed organic carrier of ion-exchange resin, is enabled in glyptal solution with initial volumetric ratio of wet ion-exchange resins to glyptal solution being 1:0.05 to 1:1. On thermal treatment at temperature 105-145°C resin is dehydrated and soaked in glyptal solution until water stops to evaporate. Then excess glycerine is distilled at temperature 145-180°C until glycerine to phthalic anhydride ratio optimum for synthesis of glyptal resin is obtained. Distilled glycerine condensate is delivered back to reprocessing cycle of the next portion of ion-exchange resin with following synthesis of glyptal resin at temperature 180-225°C.
EFFECT: reduced volume of buried end radioactive products, improved ecological conditions of their reprocessing and long-term storage, lower power inputs, and simplified procedure of reprocessing radioactive sorbents.
SUBSTANCE: invention relates to radiochemical engineering, particularly to methods of regenerating nitric acid from tail solutions from nuclear reprocessing with its purification from impurities of more volatile acids during fractionation. The method of regenerating nitric acid from tail solutions from nuclear reprocessing involves evaporation and fractionation with feeding the aqueous condensate to the top tray of the fractionation column, outlet of condensate backflow into the column still, feeding water for absorption of nitric acid with outlet of regenerated nitric acid from the tray over the still of the column and inlet of an additional stream of water into the column still. Outlet of the condensate backflow into the column still is done from one of the trays lying below the inlet of the supply vapour stream in form of secondary vapour from evaporation of the initial solution of nitric acid with impurities of volatile acids, including acetic, hydrofluoric and hydrochloric acid, inlet of water for absorption of nitric acid is done at one tray below the outlet of the condensate backflow into the column still, and impurities of volatile acids are discharged with the distillate. Improved purification from impurities enables to maintain concentration of nitric acid in the distillate between 0.03 and 0.1 mol/l, as well as in the regenerated nitric acid - from 10 to 13 mol/l.
EFFECT: method allows for regeneration of nitric acid from acetic, hydrofluoric and/or hydrochloric acid.
2 cl, 1 tbl, 5 dwg, 11 ex
SUBSTANCE: thermochemical processing of resin is carried out in a sulphuric acid medium with initial concentration of sulphuric acid in the reaction zone ranging from 400 to 1700 g/l in three steps at temperature 100-150°C, 150-250°C and 250-340°C and atmospheric pressure in an apparatus, under conditions with free access to air in the reaction zone, with constant or periodic stirring of the product in the apparatus. The obtained dry product undergoes concreting with binding substances for phosphate hardening (natural minerals or industrial wastes containing metal oxides).
EFFECT: maximum possible reduction in volume and weight of radioactive ion-exchange resins, simplification of the technology and design of equipment, low toxicity and amount of hazardous gaseous emissions into the environment, low power consumption.
2 cl, 4 ex
FIELD: power industry.
SUBSTANCE: invention refers to processing technology of spent nuclear fuel of nuclear power plants (NPP SNF). Processing method of NPP SNF involves extraction of U, Pu, Np, Tc and Zr with diluted tributyl phosphate, removal of Mo to raffinate and re-extraction of Zr to a separate solution of weak nitric acid with washing off actinides by means of extractant. Extraction is performed at the number of stages of not more than 8 from solution containing 350-900 g/l of U and 1.5-3.5 mol/l of HNO3, at saturation of extract with uranium to 75-90% of the tank and content in raffinate of 0.3-1.2 mol/l of HNO3, with introduction to U extraction zone of solution of complexing agent of molybdenum; after that, the removed flows of raffinate and Zr re-extract are separately evaporated with total regeneration of nitric acid. Vat solutions are supplied for curing of high-activity technological wastes (HTW).
EFFECT: invention allows preventing the formation of deposits of zirconium molybdate and barium nitrate during extraction operations and improving ecological indices of the production.
4 cl, 2 dwg, 2 ex, 1 tbl
SUBSTANCE: method of processing liquid radioactive wastes which contain radionuclides in ionic and colloidal form and mineral and organic ballast components in dissolved and suspended states involves oxidation of organic components of liquid radioactive wastes by feeding ozone into a stream of wastes which is pre-filtered on cellular filter material; ozonation is carried out with ozone with concentration higher than 0.2 g/l, in a channel for feeding ozone from an ozone generator into a mixing chamber, a vacuum which is less than 1/3 of the inverse ozone concentration is formed. The cross-section of the gas channel for feeding ozone is less than the ratio of the flow rate of gas with ozone to ozone concentration by about 5000 times. The stream of ozonised liquid radioactive wastes is directed opposite the stream of ozone in bubbles. The mixing chamber is divided by a net into two sections, into the bottom of which ozone is fed from an ejector with a closed stream of liquid radioactive wastes, taken from the same section, and then divided by a net and then raised in the second section opposite the stream of liquid radioactive wastes. The stream of liquid radioactive wastes is successively fed through two or more chambers, the last of which the amount of ozone is selected not less than 1/3 of the product of ozone concentration, flow rate of liquid radioactive wastes and a stoichiometric coefficient of its reaction with the organic component in the liquid radioactive wastes. The closed stream of liquid radioactive wastes with ozone is fed from the ejector into the bottom section of the mixing chamber at a tangent to its perimetre.
EFFECT: invention enables to reduce the volume of a radioactive concentrate by increasing the ozone utilisation factor.
1 dwg, 1 ex