RU2276110C1 - Method of production of the desalted water and the water of the high purity for the nuclear power plants of the research centers - Google Patents

Abstract

FIELD: nuclear power engineering; methods of production of the desalted water and waters of high purity for nuclear power plants of the research centers.

SUBSTANCE: the invention is pertaining to the field of nuclear power engineering, in particular, to the method of production of the desalted water and the water of high purity for nuclear power plants of research centers used at purification of the low-mineralized low-active liquid A-waste. The method provides for the water preliminary purification using the bulk carbon filter and after that using the mechanical microfilter, desalination of the water with the help of the reverse-osmosis filter and afterpurification of the filtrate by the ion-exchange filter. Then the purified water is collected in the tank. The reverse-osmosis purification conduct by two series filters. At that the filtrate of the first filter is routed through the intermediate tank to the inlet of the second filter, the filtrate of the second filter is routed to the ion-exchange filter for afterpurification. The concentrate of the second reverse-osmosis filter is routed into the tank of the initial waters, the concentrate of the first osmosis filter is routed to the water discharge or neutralization. The invention allows to increase the degree of desalting of the initial waters and ensures realization of purification without usage of the chemical reactants.

EFFECT: the invention allows to increase the degree of desalting of the initial waters and ensures realization of purification without usage of the chemical reactants.

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Description

The invention relates to the field of producing high purity water (VHF) for the coolants of nuclear power plants (NPP) by membrane-sorption methods and can also be used to produce demineralized water for NPP during the purification of low-mineralized low-level liquid radioactive waste (LRW).

During the operation of nuclear power plants at VHF scientific centers with a salinity of less than 1 mg / l, they are used for the preparation of coolant, and desalinated (with a salinity of up to 10 mg / l) water is used to prepare regeneration and decontamination solutions, washing equipment, washing filters, etc. In this case, demineralized water is obtained from fresh natural waters or low-mineralized low-active LRW by distillation, electrodialysis, reverse osmosis, etc., and VHF - by ion-exchange purification of demineralized water on ion-exchange resins, sulfonates, zeolites, etc. [1].

Scientific centers with nuclear power plants, unlike nuclear power plants, do not have an excess of thermal or electric energy, and therefore, for desalination, it is preferable to use reverse osmosis - less energy-intensive than electrodialysis, and even more so distillation [2]. The most effective sorbents are ion-exchange resins, providing almost complete removal of all salts, but their use is economically justified only when cleaning solutions with a salinity of not more than 1 g / l. Even in the treatment of low-saline waters, periodic regeneration is required, leading to the formation of additional salt concentrates (chemically toxic regenerates) that require neutralization [3].

A known method of handling coolants and technical solutions of nuclear power plants of scientific centers, including during their preparation, the removal of macrocomponents - salts of alkali and alkaline earth metals and microcomponents - radionuclides (desalination), for example, on the reverse osmosis apparatus (filter) and the post-treatment of the solution (filtrate) on ion exchange sorbents (ion-exchange filter). The resulting salt concentrates in the presence of radioactive or chemical contaminants are sent for disposal [4]. By its technological essence and the achieved result, this method is the closest to the claimed one and is selected as a prototype.

The disadvantage of this method is that reverse osmosis purification does not provide effective desalination (purification from monovalent ions is 2-5 times lower than from divalent ones) and as a result, ion exchange filters are rapidly saturated, which necessitates filter regeneration. Accordingly, due to the formation of spent regeneration solutions, the discharge of concentrates into the environment is impossible even if there are no radioactive or chemically toxic contaminants in the source water. In addition, according to this technological scheme, mainly demineralized water is obtained, while for VHF not only the total salt content (electrical conductivity is not more than 0.1 μS / cm) is limited, but also the content of chloride ion (not more than 0.004 mg / l) , iron oxides (not more than 0.01 mg / l) and copper oxides (not more than 0.002 mg / l) [5], which, like organic impurities, interfere with reverse osmosis purification.

The problem solved by this invention is to increase the degree of desalination of water upon receipt of VHF from low-mineralized (up to 1 g / l) water or low-level LRW and purification without using chemical reagents.

The technical result of the invention is to increase the degree of desalination of the source water by optimizing the operating modes of reverse osmosis and ion exchange filters without increasing the amount of salts in the concentrates.

The essence of the invention lies in the fact that in a method comprising desalination of water on a reverse osmosis filter and post-treatment of the filtrate on an ion-exchange filter with the direction of the salt concentrates formed in the presence of radioactive or chemical contaminants for neutralization, before desalination, water from the source water tank is fed to the pre-treatment on a bulk carbon filter and then on a mechanical filter, and reverse osmosis cleaning is carried out on two successive filters, the filtrate of the first direction they are poured through an intermediate container to the inlet of the second, the filtrate of the second is sent for purification to an ion-exchange filter, after which the purified water is accumulated in the container, the concentrate of the second is returned to the source water tank, the concentrate of the first is sent to discharge if there are no radioactive or chemically toxic contaminants in it, and their availability is sent for disposal.

The method is as follows.

Low-mineralized (up to 1 g / l) water or low-level LRW from the source water tank is sent for pretreatment to a bulk carbon filter (filled with activated carbon) to remove iron, copper, and organic solvents that interfere with the effective operation of reverse osmosis membranes. The carbon filter filtrate is sent for mechanical cleaning to a mechanical filter to remove suspensions. The filtrate of the mechanical filter is sent for desalination to the first reverse osmosis filter to remove hardness salts. The concentrate of hardness salts from the first reverse osmosis filter is sent for discharge in the absence of radioactive or chemically toxic contaminants in it, and if they are available, it is sent for neutralization (further concentration and cementing) outside this technological scheme. The softened filtrate of the first reverse osmosis filter is sent through an intermediate tank for further desalination to a second reverse osmosis filter to remove residual hardness salts and alkali metal salts. The salt concentrate of the second reverse osmosis filter is returned to the source water tank. The desalted (100-1000 times) filtrate of the second reverse osmosis filter is sent for purification to an ion-exchange filter (filled with cationic and anion-exchange resins) to obtain VHF.

Compared with the known membrane-sorption methods for water purification, the proposed method provides for the production of high-frequency substances without the use of regeneration of ion-exchange filters and the use of other chemical reagents, which is not obvious from the prior art, because the consistent use of reverse osmosis filters leads to a significant reduction in the degree of purification at each subsequent [6], ie meets the criteria of inventive step.

The proposed method is illustrated in the drawing, which shows a diagram of the production of demineralized water and high purity water for nuclear power research centers.

The technological scheme shown in the drawing includes: a tank with source water (1), pumps (2), (5) and (8), a carbon filter (3), a mechanical filter (4), the first (6) and the second (9 ) reverse osmosis filters, an intermediate tank (7), an ion-exchange filter (10) and a tank for the accumulation of purified water (11).

Getting VHF was carried out as follows. The source water from the tank 1 by the pump 2 was sent for pre-treatment to the charcoal filter 3 and the mechanical filter 4. The pre-treated water was pumped to the inlet of the first reverse osmosis filter 6 using the pump 5. Concentrate from the filter 6 was sent to the sewer. The filtrate from the outlet of the filter 6 was sent through an intermediate tank 7 by the pump 8 to the inlet of the second reverse osmosis filter 9. The concentrate from the filter 9 was returned to the source water tank 1. The filtrate from the outlet of the filter 9 was sent to an ion exchange filter 10. The purified water from the exit of the ion exchange filter 10 was sent to capacity 11.

The effectiveness of the proposed method is illustrated by examples.

Example 1. The source of low-saline water contained 100 mg / l HCO ₃ ^- , 90 mg / l SO ₄ ^2- , 10 mg / l Cl ^- , 5 mg / l NO ₃ ^- , 60 mg / l Ca ²⁺ , 15 mg / l Mg ²⁺ , 15 mg / l Na ⁺ , 10 mg / l K ⁺ , 0.3 mg / l Fe ³⁺ , 0.1 mg / l Cu ²⁺ .

The salinity of the water after the first reverse osmosis filter was not more than 30 mg / L, and the second reverse osmosis filter was not more than 3 mg / L, which made it possible to use it as desalted for the technical needs of nuclear power plants. The salinity of the water after the ion exchange filter was not more than 0.03 mg / l (the content of chloride ion was not more than 0.003 mg / l, iron oxides were not more than 0.005 mg / l and copper oxides were not more than 0.0015 mg / l), which allows you to use it as a VHF for the preparation of a coolant nuclear power plant. In this case, the ion-exchange filter purified at least 10,000 volumes of water with one volume of ion-exchange resin. At the same time, according to the prototype method with one reverse osmosis filter and regeneration of the ion exchange filter, the performance of the latter did not exceed 330 volumes of water per volume of ion exchange resin.

Example 2. It differs from example 1 in that the source water was contaminated with oil products up to 10 mg / l, suspensions up to 10 mg / l, strontium-90 to 1 · 10 ^-6 Ku / l, cesium-137 to 5 · 10 ^-7 Ku / l and cobaltrom-60 to 1 · 10 ^-7 Ku / l, i.e. were low-mineralized chemically toxic and low-level liquid wastes. Water purification was carried out according to the same scheme as in example 1, only the radioactive concentrate from the first reverse osmosis filter was collected in a separate container and then sent for disposal.

The purified water after the ion-exchange filter contained less than 0.001 mg / l of petroleum products, less than 0.001 mg / l of suspension, 90% less than 1 · 10 ^-10 Ku / l of strontium, less than 5 · 10 ^-11 Ku / l of cesium-137, and less than 60 cobalt 1 · 10 ^-11 Ku / l, i.e. less than the level of HC ^water intervention provided for these radionuclides by the radiation safety standards NRB-99 [7].

Thus, the proposed method makes it possible to increase the life of the ion-exchange filter by 30 times when producing HFV from low-mineralized (up to 1 g / l) solutions and, therefore, to eliminate the need for its regeneration, and even to get desalted (up to 10 mg / l) water without ion exchange purification, i.e. allows for virtually reagent-free water treatment. At the same time, contaminants harmful to reverse osmosis membranes and ion exchange resins (oil products, copper, iron, etc.) are removed at the pre-treatment stage, which significantly improves their operating conditions.

The proposed method can be carried out on the same domestic equipment as the prototype, i.e. industrially applicable. The method is completely reagent-free, i.e. its use does not lead to chemical pollution, which is an important environmental aspect. Moreover, the method is suitable for producing demineralized water and high-frequency water not only from low-mineralized drinking water, but also from low-active low-mineralized LRW, which allows them to be returned for secondary use for the needs of nuclear power plants of research centers.

Information sources

1. Kulsky L.A., Strakhov E.B., Voloshina A.M. Water purification technology at nuclear power plants. - Kiev, Science. Dumka, 1986. S.132-139.

2. Milligan T.J. Treatment of industrial wastewaters. - Chem. Engng., 1976, v. 83, No. 22 (Deskbook Issue), p. 49-66.

3. Khonikevich A.A. Treatment of radioactive contaminated water in laboratories and research nuclear reactors. - M., Atomizdat, 1974, p. 85-90.

4. RF patent №2168221, bull. No. 15, 2001.

5. Ganchev B.G., Kalishevsky L.L., Demishev R.S. and other nuclear power plants. - M., Energoatomizdat, 1983, p. 425.

6. Mamet V.A., Svitsov A.A., Schapov G.A. et al. Processing of liquid radioactive waste from nuclear power plants using reverse osmosis. - Thermal Engineering, 1978, No. 4, p. 52-54.

7. Radiation safety standards (NRB-99). - M., Ministry of Health of Russia, 1999.

Claims (1)

A method for producing demineralized water and high purity water for nuclear power plants of scientific centers, including desalination of water on a reverse osmosis filter and purification of the filtrate on an ion exchange filter, the direction of the formed salt concentrates in the presence of radioactive or chemical contaminants for neutralization, characterized in that before the water is desalted from the source water tank serves for pretreatment on a bulk carbon filter and then on a mechanical microfilter, and reverse osmosis treatment they are carried out on two consecutive filters, the filtrate of the first being sent through an intermediate tank to the inlet of the second, the filtrate of the second being sent for purification to an ion exchange filter, after which the purified water is stored in the tank, the second concentrate is returned to the source water tank, and the first concentrate is sent to discharge radioactive or chemical contaminants, and if any, they are sent for neutralization.