Method for the treatment of liquid radioactive waste

 

The invention relates to the field of processing of liquid radioactive waste. The inventive method for the treatment of liquid radioactive waste, including the collection of waste water Laundry, alkaline solutions from the regeneration of HE--unionicola filter, acid solutions from the regeneration of N+-cationite filters, averaging, and concentration of waste evaporators. By averaging solutions periodically through evaporation apparatus sequentially pass the mixture of waste water Laundry with alkaline and acidic solutions. Advantages of the invention are to increase the efficiency of treatment of liquid radioactive waste and reduce the amount of secondary waste generated during chemical cleaning of evaporators. 2 C.p. f-crystals, 3 tab., 1 Il.

The invention relates to the field of processing of liquid radioactive waste (LRW) and can be used at nuclear power plants or industries related to the processing of radioactive material.

During operation of nuclear power plants produce large amounts of LRW, which are formed due to protomol, processing overalls and so forth the Amount of the produced LRW modern nuclear power stations up to 500000 m3/year. To reduce the volume of LRW they are subjected to processing. Known methods of LRW, including the collection, averaging individual streams of liquid and subsequent concentration using precipitation methods of purification, ion exchange, electrodialysis, reverse osmosis [1, 2]. The disadvantage of these methods is the dependence of the methods of salt concentration and radionuclide content of the waste, the specific activity of LRW, fluctuations of the impurity composition.

The closest analogue is the way LRAW management, including the collection of waste water Laundry, alkaline solutions, from the regeneration of HE--anonimowy filters and acid solutions from the regeneration of the H+-cationite filters, averaging individual streams of liquid and the concentration of waste evaporators [3].

The concentration of LRW by evaporation require periodic chemical cleaning of evaporators. This is because in the process of evaporation averaged LRW on the surface evaporators produce large amounts of radioactive deposits, worsening tavani x-ray analysis established, the deposits formed on the surface evaporators NPP can be divided into 4 main groups:

1. Calcium and magnesium scale, which is dominated by up to 90% of caso3, CaSO4Ca(PO4)2, Mg(OH)2.

2. Oxalate deposits: oxalates of calcium CAC2O4the oxalates of iron FeC2O4. The presence on the surface evaporators oxalates associated with the use of the plant for the decontamination of solutions of oxalic acid.

3. Gelezinkeliai - FeOOH, Fe2O3, Fe3O4and zelenotsvetnaya - Fe3(RHO4)2, NaFePO4fat.

4. Silicate scale. Along with silicon dioxide in the composition of the silicate residue can include ferrosilicate and aluminosilicates.

The disadvantage of the closest analogue is the need of usage during chemical cleaning specially prepared solutions, leading to the formation of additional quantities of waste.

Task to be solved by the claimed invention is to increase the efficiency of LRW, reducing the number of secondary liquid radioactive waste generated during chemical cleaning of evaporators.

The essence of the invention is that of waste evaporators, offered periodically a portion of the alkaline and acid wastes prior to their mixing, to use as alkaline and acid solutions for chemical cleaning, sequentially passing through the evaporator device intended for concentration averaged waste, and as the alkaline solution, a mixture regenerate HE-- unionicola filter with waste water Laundry at a volume ratio between 1:(0.8 to 1), and as the acid solution using a mixture regenerate N+-cationite filters with waste water Laundry at their volumetric ratio of 1:(0,1-0,8).

In the proposed method used the following distinctive features:

Sign 1 - changed the sequence of LRW, namely, that part of the waste, bypassing the stage of averaging, periodically sent to the evaporating device, using them as solutions for chemical leaching. Sign 2 - as solutions for the chemical treatment used LRW: for the alkali treatment, a mixture regenerate HE--unionicola filter with waste water, Laundry, and acid - mixture regenerate N+-cationite filter is clean, contain regenerated ion-exchange filters and waste water from Laundry in a certain ratio to most effectively remove deposits from the surfaces of the evaporators.

In order to substantiate the claimed combination of features of the invention the criteria of novelty, inventive step given the following:

First symptom: in the way that the closest analogue all threads LRW to the treatment process residue, average by mixing, and removal of sediment from the evaporators are subject to periodic chemical cleaning specially prepared solutions, which leads to the formation of additional quantities of waste. In the proposed method, the chemical treatment is carried out in the liquid radioactive waste generated during operation of the nuclear power station. This changed the sequence of LRW (see drawing): the part of the waste, before the operation of averaging, periodically sent to the evaporators for chemical cleaning. Thus, unlike the way - the closest analogue - when implementing the proposed method does not form an additional quantity of liquid radwaste. According to the second feature: the proposed method for the chemical treatment of evaporation apparitional is a mixture regenerate HE--unionicola filter with waste water, Laundry, and acid - mixture regenerate N+-cationite filter with waste water Laundry. In modern nuclear power plants for the regeneration of HE--unionicola filter use 4-5% NaOH solution, the regeneration of N+-cationite filter 4-5% solution NGO3. After carrying out the regeneration in alkaline regenerate along with the NaOH present carbonate, chloride, fluoride, sulfate, nitrate ions. In the acid reclaim - HNO3and the metal cations. Waste water from Laundry contain surface-active substances (surfactants), complexing agents: Trilon B, sodium hexametaphosphate etc., Each of the components of alkaline and acid solutions perform a specific function in the process of removing sediment. The presence of the surfactant promotes the separation of particles of sediment from the metal surface, forming an emulsion or suspension, which does not allow the separated particles are re-deposited on the treated surface. The presence of NaOH in the alkaline wash solution facilitates dissolution and emulsification of oil inclusions, which are always present in the sediments of evaporators and impede the dissolution of the core is, the La of silicon compounds that exist in the sediments in the form nSiO2mH2O, FeOSiO2, Fe2About3SiO2, Al2About3SiO2under the action of alkali leads to the formation of soluble silicates:

SiO2+2NaOH=Na2SiO3+H2O;

FeOSiO2+2NaOH=Na2SiO3+Fe(OH)2.

Aluminum compounds interact with the alkali with the formation of soluble hydroalumination, for example:

Al(Oh)3+NaOH=NaAl(OH)4.

For compounds of zinc alkali leads to the formation of zincato - Na2ZnO2.

The complexing agents are introduced into the solution with waste waters Laundry, interact with insoluble oxalate of calcium, magnesium, iron, leading to their partial dissolution.

The presence of the acid wash solution of nitric acid can effectively dissolve iron oxide and carbonate deposits. It should be noted that when the joint presence in alkaline solution regenerate HE-- anion-exchange filters and waste water Laundry, and in the acid solution regenerate N-ka is viceroys.

Third characteristic: the efficiency of removal of deposits from the surfaces of the evaporators in a joint presence in alkaline solution regenerate HE--anion-exchange filters and waste water Laundry, and in the acid solution regenerate H-cationite filters and waste water Laundry is observed only when a certain ratio. Suggested values for the ratios of wash solutions obtained experimentally.

The method is illustrated in flow diagram of the sequence of operations management of liquid (see drawing) and examples of its implementation.

In the drawing POS.1-4 - separate threads LRW (1 - drain water, waste decontamination solutions; 2 - regenerate IT filters; 3 - regenerate N filters; 4 - waste water from Laundry); 5 - averaging and adjusting the pH of individual streams of liquid radioactive waste; 6 - residue average LRW; 7 - VAT residue formed after evaporation of liquid radioactive waste; 8 - secondary steam condensate formed after evaporation of LRW. The proposed method flows LRW (1-4) after the averaging operation and adjustment of pH (5) are fed to the residue (6). The resulting residue after VAT residue (7) direct bitumirovannaya and conden the Ute, before averaging, the evaporators for chemical cleaning.

Example 1 illustrates the effect of the volume ratio of regenerate IT filters and waste water Laundry in the alkaline wash solution on the efficiency of removal of deposits from the surfaces of the evaporators. Example 2 illustrates the effect of volume regenerate H-cationite filters and waste water Laundry in the acid solution on the efficiency of removal of deposits from the surfaces of the evaporators. Example 3 describes the claimed invention, and to compare the data on the efficiency of removal of deposits by traditional methods of chemical cleaning.

To determine the optimal proportions of the components of drilling fluids and comparative tests used cutting tubes of heating chambers evaporators Leningrad nuclear power station; as components of drilling fluids - real LRW Leningrad nuclear power station: the regenerated ion-exchange filters and waste water from Laundry. The removal efficiency of sediment was estimated by the value of Y:

Y=An/AK,

where An, AK - the amount of sediment before and after chemical cleaning.

Example 1. To determine the optimal balance of eUSA camera, area of 20 cm2were placed in a stainless steel tank was filled with 400 ml of solution containing different amounts regenerate IT-unionicola filter and waste water Laundry and kept at a temperature of 80C for 20 hours. Then the alkaline solution was trenirovki and the samples were poured acid solution containing regenerate H-cationite filter and waste water from Laundry in the ratio of 1:0,5. Washing in acid solution held at a temperature of 90-95C for 10 hours. The test results of example 1 are given in table.1.

From the data given in table. 1, it follows that for the alkali treatment is most effective to use solutions, while simultaneously containing regenerate IT filters and waste water from Laundry. The optimal ratio of volumes regenerate IT filters and waste water Laundry is 1:(0.2 to 1).

Example 2. Sample tubes of the convection cells, with an area of 20 cm2, was treated with alkaline and acid solutions, with a volume of 400 ml. Alkaline treatment was carried out with a solution containing reclaim IT-filter and waste water from Laundry in the ratio of 1:0.5, and at a temperature of 80With over 10 hours at different ratios regenerate H-cationite filter and waste water Laundry. The research results are summarized in table.2.

Are given in table.2 data show that the additive combination and N filters waste water Laundry intensifies the process of removal of sediments. The optimal ratio of the volumes of the regenerate H-cationite filters and waste water Laundry is 1:(0,1-0,8).

Example 3. The results of comparative tests of the claimed method comprising carrying out chemical cleaning using solutions based on LRW and traditional methods of chemical cleaning table.3. From the above table.3 data shows that the use of LRW for chemical cleaning can effectively remove deposits from the surfaces of the evaporators, and the proposed method does not form an additional quantity of liquid radwaste.

Using LRW (waste water Laundry and regenerates) for chemical cleaning of evaporators allows to avoid the formation of additional amounts of liquid radioactive waste.

Sources of information

1. Kuznetsov, Y. C., Sepetkovski C. I., A. Trusov, Fundamentals of water purification from radioactive contamination. Ed. Corr.-cor. The USSR Academy of Sciences C. M. Vdovenko. M, Atomizdat, 1974, the 360s.

the th nuclear power plants: Training. manual for schools. C. M. Sedov, A. F. Nechaev, V. A. Dominican, P., Krutikov. - M.: Energoatomizdat, 1985, 312 S., S.

Claims

1. Method for the treatment of liquid radioactive waste, including the collection of waste water Laundry, alkaline solutions from the regeneration of HE--unionicola filter, acid solutions from the regeneration of the H+-cationite filters, averaging, and waste concentration in evaporators, characterized in that prior to averaging solutions periodically through evaporation apparatus sequentially pass the mixture of waste water Laundry with alkaline and acidic solutions.

2. The method according to p. 1, characterized in that the alkaline solution is passed through the evaporator unit in conjunction with waste water Laundry with a volumetric ratio of 1:(0.8 to 1).

3. The method according to p. 2, characterized in that the acid solution is passed through the evaporator unit in conjunction with waste water Laundry with a volumetric ratio of 1:(0,1-0,8).

 

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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.

1 dwg

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