RU2452050C1 - Method for processing solid mixed radioactive wastes - Google Patents

Abstract

FIELD: ecology.

SUBSTANCE: method for processing solid mixed radioactive wastes includes their thermal destruction in a chemically active environment in a heated device. Thermal destruction of solid mixed radioactive wastes of organic origin is carried out in the medium of radioactive salt fusion cakes and sediments previously fluidised with high-boiling mineral acids in process of heating from 20 to 350°C in four stages, by means of sequential increase and maintenance of medium temperature in the device in the ranges from 20 to 60°C, from 100 to 150°C, from 150 to 250°C, from 250 to 350°C, under atmospheric pressure, in conditions of free access of air into the reaction zone as the product is mixed in the device, and the produced dry product is solidified.

EFFECT: invention makes it possible to possibly reduce volume and weight of solid radioactive wastes to the maximum, to simplify technology and design of the equipment, to reduce toxicity and quantity of hazardous gas emissions into environment.

3 cl, 2 ex

Description

The invention relates to the field of environmental protection and can be used in the processing (disposal) of solid mixed radioactive waste generated during the operation of nuclear power plants (NPPs).

A large amount of medium and low level solid radioactive waste (SRW) is inevitably generated and accumulated at a nuclear power plant as a result of production activities, which are usually divided into combustible (combusted) and non-combustible (non-combustible) waste [V.P.Shvedov, V.M.Sedov and other nuclear technology. Moscow, Atomizdat, 1979, p. 248-249, 252].

Solid non-combustible radioactive waste includes metal fragments and components of technological equipment, construction waste, filters of ventilation systems, sludge and salt sludge from LRW storage tanks, melts of deep evaporation plants (UGU) of bottoms, etc. The amount of solid salt waste (packed sediments and UGU melt ) is from 10 to 30% of the total volume generated at the NPP LRW.

Organic waste, which is conventionally divided into two large groups - cellulose (paper, cardboard, rags, wood, cotton wool, etc.) and polymeric (polyethylene, plastic compound, ion-exchange resins, which have worked out their routine life) are materials that are burned. The volume of solid combustible radioactive waste (RW) is 40-60% of the total mass of radioactive waste generated at nuclear power plants [Yu.V. Chechetkin, A.F. Grachev. Radioactive waste management. Samara, Samara Printing House, 2000, p.137, 207].

An urgent problem of radioactive waste management at nuclear power plants, requiring effective decisions, is the problem associated with the high degree of filling of the station storage with radioactive waste and the absence at the majority of nuclear power plants of existing plants (sites, workshops) for the disposal of radioactive waste directly on the territory of the nuclear power plant. This significantly aggravates the environmental hazard in the regions where the nuclear power plant is located, due to the possibility of radionuclide release into the environment [Yu.P. Korchagin. Reducing the receipt of radioactive waste and technology for their processing. Abstracts of the 4th international scientific and technical conference. Radioactive waste management. M., June 26-28, 2001, p.13]. Transportation of station radioactive waste to specialized enterprises for their disposal is associated with environmental risk associated with the possibility of radiation pollution in the event of road traffic accidents and sabotage.

Currently, none of the countries has effective technologies to completely solve the problem of handling radioactive waste generated at nuclear power plants. In most countries, radioactive waste is simply sorted and stored on the territory of a nuclear power plant in anticipation of a solution to this problem, which is why radioactive waste management is still one of the research priorities in countries with developed nuclear energy [Yu.V. Chechetkin, A.F. Grachev. Radioactive waste management. Samara, Samara Printing House, 2000, p.3].

It is known that to ensure environmental safety during long-term storage and disposal of radioactive waste, a set of measures (technologies) for their disposal should be carried out. At the same time, the main conditions for organizing effective RW disposal technologies are not only ensuring the requirements for maximum reduction of their volume and quality curing (monolithic, monolithic, immobilization) of the final product in a solid matrix that meets the requirement of reliable RW isolation from the external environment, but also the simplicity of the methods used in the technology and hardware design of the RW reprocessing process. It is also important to minimize energy costs, cost and availability of reagents and materials used in the technology of disposal of radioactive waste.

In the technology for processing non-combustible SRW, a special place is occupied by the problem of extracting solid-phase caked salt sediments from station storage tanks of LRW concentrates both in an emergency situation for their transfer to reserve tanks and for sending saline waste concentrates for solidification. Currently, all practical methods for the extraction of salt sediments from LRW storage tanks are based on the use of mechanical, hydromechanical, and pulsating devices and units that operate in a corrosive radioactive environment, which creates certain difficulties in the maintenance and repair of this equipment [L .S. Raginsky, A. A. Reznik and others. Ways of solving the problem of RW extraction from storage tanks of LRW nuclear power plants. Abstracts of the 4th international scientific and technical conference. Radioactive waste management. M., June 26-28, 2001, p.24, 25 and A.S. Nikiforov, V.V. Kulichenko, M.I. Zhikharev. Neutralization of liquid radioactive waste. M., Energoatomizdat, 1985, p.69-70].

Currently, in the practice of neutralizing mixed solid combustible organic waste (cellulosic and polymeric) thermal methods are widely used. Thermal methods primarily include methods of their fire and plasma combustion in special furnaces at temperatures of 800-4000 ° C. These methods make it possible to transfer organic radioactive waste into a biologically and fireproof state, while the volume of waste can be reduced by 10-50 times [Yu.V. Chechetkin, A.F. Grachev. Radioactive waste management. Samara, Samara Press House, 2000, p.164-170, 204-206 and V.P. Shvedov, V. M. Sedov and others. Nuclear technology. Moscow, Atomizdat, 1979, p. 252-256].

The main disadvantages of the methods of fire and plasma burning of organic RW are the high temperatures of the process, the significant metal consumption of the equipment, the complex hardware and technological design of the process, etc., which leads to a significant increase in energy and capital costs.

In this regard, the search for simple effective methods for the disposal of mixed organic radioactive waste, which would be carried out at lower temperatures, is highly relevant.

One of such methods is low-temperature pyrolysis of solid organic waste in molten hydroxides and alkali metal salts, which is currently being developed both in our country and abroad [Yu.V. Chechetkin, A.F. Grachev. Radioactive waste management. Samara, Samara Press House, 2000, p.206-209 and Yu.V. Ostrovsky, V.A. Matyukha. Thermal destruction of solid organic waste with alkali melts. News of the Academy of Industrial Ecology. No. 2, M., Edition of the Academy of Industrial Ecology, 1999, S. 60-67]. This method by technical nature is closest to the claimed and selected as a prototype.

The essence of the prototype method is that the pyrolysis of solid radioactive waste of organic origin is carried out in a chemically active medium, which is a molten alkali, at a temperature of 400-450 ° C. As a result of pyrolysis, pyrolysis gas with a high calorific value and solid particles of radioactive aerosols are formed.

Despite its indisputable advantages (simplicity of design and compact equipment, relatively low melting temperatures of alkalis and the process itself, etc.), the prototype method has significant drawbacks.

During the pyrolysis of solid organic radioactive wastes in alkali melts, solid particles of alkalis, acid gases and products of pyrolysis of organic origin get into the gas phase, which significantly complicates the dust-gas cleaning system, which requires deep extraction of aerosol solid particles and neutralization of “acid” gases with subsequent oxidation of organic substances to harmless СО ₂ and Н ₂ О by the catalytic method [Yu.V. Chechetkin, A.F. Grachev. Radioactive waste management. Samara, Samara Printing House, 2000, p.208]. In addition, the prototype method does not provide a solution to the problems of the neutralization of radioactive salt sediments and floats, the treatment of the resulting secondary radioactive waste and spent radioactive alkali melts.

The task to which the invention is directed is the creation of a universal method (integrated technology) for the disposal of mixed solid radioactive waste generated at nuclear power plants, which allows:

- to carry out the washing out (liquefaction) of salt packed sediments of LRW storage facilities and the old-time UFU melts and their hydraulic pumping from storage using concentrated high-boiling mineral acids as a fluidizing liquid;

- to carry out a joint neutralization of acid-diluted salt concentrates (packed sediments and floats) and mixed organic carbon-containing wastes in one simplest apparatus (bath, tank);

- as much as possible to reduce the volume and mass of radioactive waste and the final product subject to long-term storage;

- reduce the metal consumption of equipment and energy costs for the process;

- transfer the final product of RW processing into a fire and explosion safe state;

- to provide the possibility of immobilization of biologically stable solids from the processing of radioactive waste in a solid matrix (geo-cement stone), which provides reliable long-term storage and burial of the final product;

- reduce the financial costs of reagents;

- to reduce the technogenic impact of harmful substances on the environment of the region during the disposal of radioactive waste and improve the environmental situation during the long-term storage of final radioactive products.

To solve the problem and achieve the technical result in a method for processing solid mixed radioactive waste, including their thermal destruction in a chemically active medium (pyrolysis) in a heated apparatus (bath), it is proposed that thermal destruction of mixed solid radioactive waste of organic origin be carried out in a medium pre-liquefied with high boiling point mineral acids of radioactive salt sediments and floats when heated from 20 to 350 ° C.

It is also proposed that in the process of neutralization, heating and RW treatment be carried out in four stages, successively raising and maintaining the temperature of the medium in the apparatus in the ranges from 20 to 60 ° C, from 100 to 150 ° C, from 150 to 250 ° C, from 250 to 350 ° FROM.

It is also proposed that the RW neutralization process be carried out at atmospheric pressure, under conditions of free access of oxygen (air) to the reaction zone of the apparatus with stirring of the product in the apparatus.

In addition, it is proposed that the dry product obtained as a result of RW neutralization be monitored using phosphate hardening binders, natural minerals or industrial wastes containing metal oxides.

The essence of the proposed method lies in the fact that it incorporates the principle of "radioactive neutralized in radioactive". Namely, it is proposed that the thermal destruction (pyrolysis) of solid mixed radioactive organic waste be carried out in a chemically active medium, which is radioactive salt sediments and melts diluted with an excess of high boiling mineral acids. During the neutralization process, gradually warm up the medium in which solid radioactive waste of organic origin is placed in the range from 20 to 350 ° C, and homologate the resulting dry processing product, for example, with phosphoric acid or mixing liquids based on it using natural minerals as a protective matrix or industrial waste containing metal oxides.

The proposed method allows, depending on the composition (type) of the RW accumulated at the NPP, their quantity, the degree of filling station storages with waste, etc., to carry out the disposal of RW using a flexible (universal) technology that enables the processing of RW both individually and comprehensively (sequentially , together) with the receipt of final products, which are solid monoliths (geo-cement stones), suitable for environmentally safe long-term storage.

It has been experimentally established that long-standing salt deposits and melts are effectively diluted with concentrated high boiling mineral acids, in particular phosphoric, sulfuric acids and their mixtures, with the formation of a mobile transportable product, which is a saturated mixture of metal salts of mineral and organic acids in excess of high boiling mineral acids.

When implementing the proposed method, the need to use a specific acid or mixture of acids is determined by many factors, the main of which is the quantity and quantitative ratio (salt sediment: organic waste) of processed SRW.

So, if the composition of the SRW processed includes mainly salt sediments and floats, it is advisable to liquefy and neutralize them using phosphoric acid or phosphoric acid with the addition of sulfuric acid.

The choice of phosphoric acid in this case is preferable in that the number of hardly soluble and insoluble metal phosphates that are formed during the processing of salt deposits and floats in water significantly exceeds the number of insoluble sulfates [V.I. Perelman. Handbook of a chemist. Goskhimizdat, Moscow, 1955, pp. 55-86]. With the final immobilization of SRW processing products, this makes it possible to increase the water resistance of monolithic products and, therefore, reduce the leachability (leachability) of radionuclides from them during long-term storage.

When neutralizing solid radioactive waste, consisting mainly of organic waste, it is necessary to use salt sediments and smelts diluted with sulfuric acid as a chemically active medium.

The choice of sulfuric acid to dilute salt sediments and floats and subsequent neutralization of radioactive waste of organic origin in them is preferable in that, in the interaction of concentrated H ₂ SO ₄ with organic materials, a number of chemical processes can occur that provide additional opportunities to increase the efficiency of SRW processing. Concentrated sulfuric acid itself has strong oxidizing properties, especially when heated [B.V. Nekrasov. Fundamentals of General Chemistry. Volume 1. Ed. Chemistry. Moscow, 1965, p. 314]. Sulfuric acid is usually reduced to colorless sulfur dioxide (SO ₂ ), which, in turn, at a sufficiently high temperature, but not more than 400 ° C in the presence of catalysts, interacts with oxygen by a highly exothermic reaction - 1 with the formation of sulfur trioxide fuming in air ( SO ₃ ). Sulfur trioxide, in turn, is also characterized by strong oxidizing properties.

A noticeable decomposition of SO ₃ upon heating (by reaction opposite to its formation) occurs only at temperatures above 400 ° C.

Sulfuric acid also actively absorbs water vapor [N.L. Glinka. General chemistry. Volume 1. Ed. Chemistry, Leningrad Branch, 1976, p. 384]. The ability to absorb water is explained by carbonization of organic substances, especially those belonging to the class of hydrocarbons (fiber, sugar, etc.), under the action of concentrated sulfuric acid on them. The composition of hydrocarbons, hydrogen and oxygen are in the same ratio as they are in water. Sulfuric acid, even cold, takes away hydrogen and oxygen from hydrocarbons, which form water, and carbon is released in the form of coal. Hot sulfuric acid, being an energetic oxidizing agent, oxidizes the formed carbon, according to reaction (2), to volatile products - СО ₂ , SO ₃ and Н ₂ О

In addition, when "amorphous" carbon is heated in air, it interacts vigorously with oxygen by reaction (3) [B.V. Nekrasov. Fundamentals of General Chemistry. Volume 1. Ed. Chemistry. Moscow, 1965, p.6]

The main component of combustible organic waste belonging to the class of cellulosic materials is fiber. Plant tissue is built from it. Cotton wool, filter paper - the most pure forms of fiber (up to 96%). The main components of wood are fiber (prevails) and lignin. Cellulose and fiber in the cold are dissolved in concentrated sulfuric acid (with partial destruction) [A.A. Petrov et al. Organic chemistry. Ed. Higher School, Moscow, 1973, p.302], forming a viscous solution [N.L. Glinka. General chemistry. Volume 1. Ed. Chemistry, Leningrad Branch, 1976, p. 490].

The polymeric materials that make up the burnt SRW are high molecular weight organic chemical compounds whose macromolecules are constructed (consist) of a large number of repeating hydrocarbon groups (units) of one or different monomers interconnected by chemical bonds [A.I. Artemenko. Organic chemistry. Ed. "Enlightenment", Moscow, 2001, p.333-334, 353]. The main physical and chemical properties (thermal and chemical resistance) of polymeric materials are very close. It is known that when heated, polymeric materials soften, at temperatures of 110-170 ° C they turn into a liquid-like (viscous) state, and at temperatures above 300 ° C their huge molecules are destroyed [A.I. Artemenko. Organic chemistry. Ed. "Enlightenment", Moscow, 2001, p. 343-345 and A.F. Nikolayev. Technology of plastics. Ed. “Chemistry”, Leningrad Branch, 1977, p.29]. The destruction (destruction) of polymeric materials is intensified in an oxidizing environment in the presence of catalysts (heavy metals in higher degrees of oxidation).

It is known about the catalytic effect of metals in higher degrees of oxidation, for example, Fe ⁺³ , accelerating the kinetics of the process of thermochemical destruction of organic substances [US Patent No. 4737315, 1986, G21F 9/08 and Journal of Radijanalytical Chemistry, 1983, v.78, No. 2, p. 295-305]. When implementing the proposed method, the catalysts that accelerate the reaction of thermochemical destruction of cellulosic and polymer SRW are metal cations (Fe ⁺³ , Cu ⁺² , etc.) that are part of radioactive salt concentrates (salt precipitation and floats).

It is also important that H ₂ SO _{4 is} not scarce and is used in the technological cycle of operating and designed NPPs with VVER for the regeneration of H-cation exchange filters of the secondary condensate purification system. Concentrated (above 75%) sulfuric acid does not act on iron, which allows it to be stored and transported to places of radioactive waste processing in steel tanks (tanks) [B.V. Nekrasov, Fundamentals of General Chemistry. Volume 1. Ed. Chemistry, Moscow, 1965, p. 314].

It is known [RF patent No. 2336584, G21F 9/04, publ. 10/20/2008, bull. No. 29] that during the heat treatment of salt concentrates containing an excess of H ₃ PO ₄ at temperatures of 100-150 ° C, not only the purely physical process of thermal distillation of water, low boiling mineral and organic acids, such as nitric and acetic (the boiling point of aqueous solutions) occurs HNO ₃ no more than 122 ° С [B.V. Nekrasov. Fundamentals of general chemistry, vol. 1, published by Chemistry, Moscow, 1965, p. 420]; acetic acid - 118.1 ° С [V.I. Perelman. Chemist’s provocateur, Goskhimizdat, Moscow, 1955, pp. 154-155]), but also the thermochemical decomposition of salts of the basic acids that make up G PO (boric, nitric, oxalic) - to volatile borates, nitrogen oxides and carbon, while Н ₃ РО _{4 is} not volatile (boiling point Н ₃ РО ₄ - 213 ° С [V.I. Perelman. Chemical chemist reference book. Goskhimizdat Moscow, 1955, p.66-68]) and is spent only on chemical reactions with the salt components of LRW with the formation of fire-explosion-proof, anhydrous [R. Ripan, I. Chetyanu. Inorganic Chemistry, Volume 1, Ed. Mir, Moscow, 1971, p.86] phosphates.

Similar results on the transformation (change) in the composition and properties of salt concentrates were obtained by the authors during the development of the proposed method using concentrated sulfuric acid as a fluidizing liquid (boiling point of H ₂ SO ₄ - 336.5 ° C). At the same time, the final product of heat treatment of salt mixtures in a sulfuric acid medium was a quasi-homogeneous, transportable mixture of crystalline salts (mainly sulfates) in excess of H ₂ SO ₄ .

The above information on the physicochemical properties of sulfuric and phosphoric acids, salt concentrates based on them, the known information on the thermochemical resistance of organic materials in aggressive acidic environments and the experimental data obtained during the development of the proposed method indicate that the treatment of mixed combusted SRW in A salt product diluted with sulfuric acid or with a mixture of sulfuric and phosphoric acids in the temperature range from 20 to 350 ° C leads to complete destruction (destruction) of SRW with the formation gaseous products and ash solids. The composition and amount of ash residue depends on the composition of the used salt concentrate, mineral additives (stabilizers) used in the production of polymeric materials.

It has been experimentally established that the process of thermochemical destruction of SRW of organic origin in the medium of salt fluids and sediments previously diluted with high boiling mineral acids proceeds in stages with the formation of intermediate products in the apparatus.

At the initial stage, at temperatures of 20-60 ° C, intense dissolution of the cellulosic materials that make up the mixed SRW occurs. The process takes place with self-heating and foaming of the product in the apparatus. In this regard, it is advisable to introduce the ground SRW mixture into the apparatus in small portions with constant stirring. After completion of SRW input and termination of steam and gas evolution from the reaction zone of the apparatus, the heating is increased. In the temperature range of 100-150 ° C, the second stage of waste treatment is carried out. In this temperature range of processing, not only deep dehydration of mineral salts occurs, but also the thermochemical transformation of salts of the main acids that make up salt concentrates (boric, nitric, oxalic, acetic, etc.) to water vapor, volatile borates, nitrogen, and carbon with the formation in the apparatus of a mixture of dehydrated mineral salts (sulfates and phosphates) with hydrocarbon components of the waste. The completion of the process stage is indicated by the termination of steam and gas emissions from the reaction zone of the apparatus.

With a further increase in the temperature in the apparatus and continued treatment of radioactive waste in the temperature range of 150-250 ° C, the organic waste base is subjected to intense thermal, chemical, catalytic, oxidative effects of sulfuric acid and the resulting sulfur trioxide with the formation in the apparatus of a powdery mixture biologically resistant to all types of microorganisms "Amorphous" carbon black [RF patent No. 2156511, IPC ⁶ G21F 9/28, 9/28, publ. 09/20/2000. Bull. No. 26] and dehydrated salts of high boiling mineral acids and metal oxides. The criterion for completing the process of complete destruction of mixed SRW to carbon is the absence of sulfur trioxide fuming in the air from gas emissions.

With increasing temperature and continuing the process of neutralization of solid radioactive waste in the temperature range of 250-350 ° C, the formed carbon under conditions of free access of atmospheric oxygen to the reaction zone of the apparatus completely burns by reaction (3) to carbon dioxide. At the same time, an ash residue remains in the apparatus, which is a dehydrated mixture of salts of high boiling mineral acids with metal oxides. The criterion for completing the process of deep thermochemical destruction of organic SRW is the cessation of gas evolution from the reaction zone of the apparatus and the constancy of the weight of the final product.

When implementing the proposed method, it is also positive that the main reactions that occur in the reaction zone of the apparatus are exothermic, and the “amorphous” carbon formed at the final stage of neutralization of the burned solid waste is fuel itself, which can significantly reduce the external energy consumption for the process.

When implementing the proposed technology in practice, the main chemical-technological parameters, such as the required amount of acids to dilute salt products, the temperature regime of the process, the sequence (sequence, stage-by-stage) of SRW processing, etc., are determined individually in each case and depend on the type of processed waste, their quantity and quantitative ratio, the degree of filling station storages with waste, etc.

After the disposal of mixed SRW of organic origin by the proposed method, the resulting dry ash residue is monolithic. For this, phosphoric acid or mixing liquids based on it can be used [S.L. Golynko-Wolfson, M. M. Sychev, L. G. Sudakas and others. Chemical fundamentals of the technology and application of phosphate bonds and coatings. Chemistry, Leningrad Branch, 1968], which allow one to obtain solid matrices similar to the properties of geo-cement stones from the final products of the disposal of SRW. The feasibility of monolishing the dry final product into a geo-cement stone is determined by the fact that such a matrix is chemically, thermally, radiation and biologically more stable in comparison with ordinary cement or bitumen used in the immobilization of salt concentrates of radioactive waste. By its nature, geocement stone is close to rocks in which it is planned to place repositories for the long-term disposal of radioactive waste.

When conducting experiments to justify the proposed technology for the disposal of SRW used:

- concentrated sulfuric acid brand "hch" according to GOST 4204-77;

- salt floats by chemical composition simulating the melts obtained at the Novovoronezh NPP USU. The main salt components of the melt are nitrates and borates (base) of sodium, copper, iron, nickel and chromium in the higher degrees of oxidation, as well as (in a smaller amount) metal salts of organic acids (oxalic, acetic and ethylenediaminetetraacetic);

- dry salt mixtures, in chemical composition simulating salt concentrates formed as a result of evaporation of vat residues coming for curing at the Leningrad NPP. The main salt components of the mixtures are nitrates and chlorides (base) of sodium, copper, iron, nickel, chromium, manganese and cobalt in the higher degrees of oxidation, as well as (in a smaller amount) metal salts of organic oxalic acid;

- cellulose household materials (filter paper, rags, cotton wool, wood, etc.);

- floor plastic compound (soft PVC) and plastic film;

- a mixture of KU-2-8 hC cation exchanger sorbents with AV-17-8 hS anion exchanger in a 1: 1 volumetric ratio of swollen sorbents worked out in the purification system of the 2nd coolant of the transport nuclear power plant with a water-water reactor.

When the stage of phosphate homologation of the final dry product into an inert matrix was worked out, the natural magnetite powder of the Khibiny ore basin and technical phosphoric acid according to TU 2142-002-00209450-96 were used.

The experiments were carried out in an open quartz crucible under conditions of free access of air to the reaction zone with periodic (1 time in 15 minutes) stirring of the product in a crucible with a quartz stirrer.

Examples of the proposed method.

Example 1

1.0 cm ^{3 of} salt melt (weight 0.98 g), placed in a quartz crucible, is diluted in 3.0 cm ^{3 with} concentrated H ₂ SO ₄ , after which it is introduced into the liquefied cold product (20 ° C) in small portions with stirring 0 , 5 grams (2.5 cm after compaction) of a crushed mixture of organic materials (rags 0.08 grams, filter paper 0.07 grams, sawdust 0.05 grams, plastic 0.16 grams, household polyethylene 0.14 grams) and carry out the neutralization process in the temperature range of 20-60 ° C. After the vapor and gas evolution ceases and the cellulose materials are dissolved (liquefied), heating is turned on and, when the temperature in the reaction zone reaches 100 ° C, air-dry IOS mixture is introduced in small portions into the product. A total of 5.0 cm ³ (3.0 grams) of IOS was introduced. Further thermochemical processing (pyrolysis) of organic materials is carried out in stages at temperatures of 100-150 ° C and 200-250 ° C until the evolution of white SO ₃ vapor from the reaction zone ceases. The combustion of the amorphous carbon formed in this process is carried out at temperatures of 250-350 ° C until an ash residue having a constant weight is formed.

The main results of the example:

- the volume of the final product is 1.0 cm ³ ;

- the weight of the final product is 0.79 grams;

- decrease in volume - 8.5 times;

- weight reduction - 5.7 times.

Example 2

1.0 cm ^{3 of} salt melt (weight 1.01 grams) placed in a quartz crucible is liquefied in 5.0 cm ^{3 of} concentrated H ₂ SO ₄ , after which it is introduced into the resulting cold product (20 ° С) in small portions with stirring 1 , 0 grams (5.0 cm ³ after compaction) of a crushed mixture of organic materials (rags of 0.2 grams, filter paper 0.2 grams, sawdust 0.1 grams, plastic 0.25 grams, household polyethylene 0.25 grams) and carry out the neutralization process in the temperature range of 20-60 ° C. After the vapor and gas evolution ceases and the cellulose materials are dissolved (liquefied), the heating is turned on and the product is heated at a temperature in the reaction zone of 100-150 ° C until a liquid “quasi-homogeneous” mixture of hydrocarbons, dehydrated salts of mineral acids, metal oxides and carbon in excess of H are formed in the bath ₂ SO ₄ . Next, a wet mixture of IOS is introduced in small portions into the resulting mixture. A total of 10 cm ³ (6.0 grams) of IOS was introduced. After the cessation of the release of water vapor from the reaction zone, further thermochemical processing (pyrolysis) of the organic materials is carried out at a temperature of 150-250 ° C until the cessation of the release of white SO ₃ vapor from the reaction zone. The combustion of the amorphous carbon formed in this process is carried out at temperatures of 250-350 ° C until an ash residue having a constant weight is formed. The main results of the example:

- the volume of the final product is 1.0 cm;

- the weight of the final product is 0.8 grams;

- decrease in volume - 16 times;

- weight reduction - 10 times.

The resulting product (ash residue) is mixed in a cylindrical form with natural magnetite in a volume ratio of 1: 0.5 and the mixture is cured using concentrated phosphoric acid as the mixing liquid. The final product after completion of the cold phosphate hardening process and its additional heat treatment at a temperature of 20 → 250 → 20 ° C is a durable water-resistant geo-cement monolith with a volume of about 1.5 cm ³ .

The proposed method of processing SRW in comparison with the prototype has significant advantages:

- simplifies the technology for the disposal of SRW due to the possibility of conducting the entire cycle of their processing, from deep thermochemical destruction of the combusted organic waste and drying of the final product to immobilization (monolithic) of the dry product in an inert matrix (geo-cement stone), in one heated apparatus (capacity);

- reduces the metal consumption of equipment and energy costs for the process;

- minimizes the volume and mass of solids and the final product subject to long-term disposal;

- increases radiation and fire safety during the process of disposal of SRW;

- reduces the consumption of reagents and reduces the toxicity of gas emissions from processing;

- allows you to regenerate sulfuric acid for its reuse in the cycle of disposal of SRW;

- reduces the technogenic impact of harmful substances on the environment of the region and improves environmental conditions during long-term storage of final radioactive products.

In general, the introduction of the proposed method into the practice of the disposal of radioactive SRW at WWER nuclear power plants will completely “burn” the radioactive organic waste, transform the radioactive fire and explosive salt melt and precipitation into a fire and explosion safe state, and reduce the volume and weight of the resulting products tens of times processing and ensure their reliable long-term disposal, reduce the impact of harmful substances on the environment of the regions during the disposal of SRW and improve the environmental situation for a long time m storage of final products.

Claims (3)

1. A method of processing solid mixed radioactive waste, including their thermal destruction in a chemically active medium in a heated apparatus, characterized in that the thermal destruction of solid mixed radioactive waste of organic origin is carried out in a medium preliminarily liquefied with high boiling mineral acids, radioactive salt melts and precipitation when heated from 20 to 350 ° C in four stages by successively raising and maintaining the temperature of the medium in the apparatus in the ranges from 20 to 60 ° C, from 100 to 150 ° C, from 150 to 250 ° C, from 250 to 350 ° C, at atmospheric pressure, under conditions of free access of air to the reaction zone with stirring of the product in the apparatus, and the resulting dry product is monopolized. 2. The method according to claim 1, characterized in that the homologation of the obtained dry product is carried out with phosphate hardening binders. 3. The method according to claim 2, characterized in that, as phosphate hardening binders, for example, natural minerals or industrial wastes containing metal oxides are used.