RU2765864C1 - Method for processing carbon irradiated in a reactor of an npp and apparatus for implementation thereof - Google Patents

Abstract

FIELD: chemical processes.

SUBSTANCE: invention relates to a method and apparatus for processing carbon irradiated in a reactor of an NPP. The method includes selecting a method for separating Carbon isotopes from a group of separation technologies: gas diffusion, nozzle method, gas centrifugation, aerodynamic separation method, laser method. Then working gas is produced from the irradiated NPP Carbon to extract ¹⁴C isotope atoms by the selected separation method. The ¹⁴C isotope is then isolated on a single-stage separation unit or a cascade of said units and separated in a separation unit. Separation is executed to a level ensuring, in a fraction for collection from a single unit or cascade, depleted by the content of ¹⁴C isotope, the activity of ¹⁴C isotope below the level allowing for near-surface disposal of radioactive waste, then sorting, compaction, differentiated disposal of radioactive waste, and return of the waste to nature with natural activity are executed. The apparatus comprises a unit for processing Carbon into working gas for a Carbon isotope separation unit, the output whereof is supplied to the input of the separation unit.

EFFECT: creation of separated fractions of the working gas with a content of ¹⁴C isotope above the initial content and with a content of ¹⁴C isotope reduced to a level allowing for near-surface disposal.

21 cl, 10 dwg

Description

The invention relates to the nuclear industry, namely to the technology of disposal of radioactive waste, and can be used for processing irradiated reactor graphite (hereinafter irradiated Carbon NPP) after the decommissioning of uranium-graphite reactors of nuclear power plants (NPP).

In uranium-graphite reactors, the graphite form of carbon is used as a moderator. At the same time, the radioactive isotope ¹⁴ C is accumulated in Carbon - a β-emitter with a half-life of 5730 years. After the reactor is decommissioned and unloaded, the irradiated carbon must be disposed of.

According to experts, there were about 26,000 tons of irradiated graphite in operating and decommissioned uranium-graphite reactors in the world. Currently, in the Russian Federation there are about 60 thousand tons of graphite in operating RBMK type reactors, 30,000 tons in industrial reactors and 2500 tons in industrial power reactors (A.V. Bushuev, A.F. Kozhin, V.N. Zubarev. et al., Radioactive Contamination of Spent Reactor Graphite / Atomnaya Energiya, 2014, v. 117, issue 3, pp. 156-159).

The level of activity of freshly recovered irradiated carbon from a nuclear power plant depends on the type of reactor and on its operating conditions. According to various studies (for example - Pavlyuk A.O. Technical solutions and experience of JSC ODC UGR on handling irradiated graphite during decommissioning, International public forum-dialogue and exhibition AtomEco 2017, Moscow, November 21-22, 2017) the activity of freshly extracted irradiated NPP Carbon is 1.5÷10⋅10 ⁵ Bq/g (Table 1).

The rules for handling radioactive waste are regulated by Federal Law No. 190-FZ dated July 11, 2011 “On the management of radioactive waste and on amendments to certain legislative acts of the Russian Federation” (website of the Federal State Unitary Enterprise “National Operator for the Management of Radioactive Waste”, http: //www.norao.ru/). In accordance with article 24 of the law: according to the level of activity and radiation characteristics, this type of radioactive waste (RW) belongs to hazard class 2, which implies centralized deep burial (Table 2).

The import of radioactive waste into Russia from abroad for processing and disposal is regulated by the same law, which means a significant restriction on the disposal of even radioactive waste from reactors built by the USSR outside of Russia. Similar laws and classifications have been adopted in all developed countries using nuclear energy and isotope sources.

Prior Art

There is no experience, equipment and technologies for moving such volumes of class 2 radioactive waste over several thousand kilometers to a centralized deep storage facility, just as there are no technologies for creating the storage facility itself, which ensures its tightness for several thousand years. There are also no ways to process and dispose of the irradiated Carbon from NPPs (at present, these radioactive wastes are stored near the places of unloading from the reactors), although an active search for methods is underway.

It should be noted that in the process of off-design operation, decommissioning of reactors, a significant amount of new radioactive waste is generated with a more complex composition compared to the waste generated during the normal operation of these facilities (Table 1 data). At the same time, the main contribution (>90%) to the activity of irradiated NPP carbon, which determines its hazard class and the problem of its storage due to a half-life of 5730 years, is made by the 14C carbon ^isotope .

The fundamental simplification of the situation is the development of technology for the processing of irradiated carbon at nuclear power plants, which will make it possible to transfer the bulk of this type of radioactive waste to the third hazard class, which allows local near-surface disposal, and, ideally, to obtain a natural level of activity of these wastes that does not require burial and storage.

At present, various methods for processing irradiated graphite have been proposed, including for reducing the content of the ¹⁴ C isotope in the irradiated carbon of the NPP due to physical-chemical, mechanical treatment of the surface of the blocks of irradiated carbon of the NPP. They showed the possibility of reducing the total activity of this isotope by several (2-5) times, which practically does not change the hazard class of radioactive waste and the requirements for its disposal.

The authors of the patent "Method of processing reactor graphite waste" (No. RU 2624270, priority 24.02.2016) propose a method for processing reactor graphite waste, including its high-temperature processing, characterized in that, before heat treatment, graphite is exposed to reagents that destroy its surface layer containing radioactive nuclides , and remove the resulting product from the graphite surface. According to the results of the application of the method, all non-carbon radioactive impurities were almost completely removed with mass losses (essentially: mass loss - concentrated active radionuclides of radioactive waste of class 2 subject to unconditional centralized disposal) from 3 to 52%.

In another patent "Method of processing irradiated reactor graphite" (No. RU 2580818, priority 07/04/2015), the authors propose a method that includes the selection of reactor graphite from the stack of a uranium-graphite reactor, mechanical grinding of large pieces, oxidation of crushed graphite, characterized in that the irradiated reactor graphite is oxidized in a low-temperature plasma environment, graphite is first placed in a plasma-chemical reactor as consumable electrodes, the material of consumable electrodes is evaporated to form atomic carbon, an oxidizer is introduced into the area of low-temperature plasma formation, the products of the plasma-chemical reaction are moved along the axis of the reactor, and the reaction products are deposited in the dispersed phase in the form of an ash residue on the walls of the reactor, gaseous reaction products are removed from the reactor, part of the gas flow is looped and fed together with an oxidizer into the reactor, gaseous reaction products, with the exception of carbon oxides, are captured by a scrubber, approx. carbon oxides are transferred to the liquid phase and sent for further disposal, the solid ash residue is removed from the plasma-chemical reactor and buried separately. According to the results of applying the method, all non-carbon radioactive impurities were almost completely removed, but there was no data on a significant decrease in the activity of the ¹⁴ C isotope. The reason for the absence of a significant decrease in the activity of the ¹⁴ C isotope is that the ¹⁴ C isotope, produced as a result of neutron irradiation of Carbon during the operation of the reactor, is distributed almost evenly over the entire volume of blocks of irradiated Carbon at the NPP (Pavlyuk A.O. - “Development of technological solutions for processing elements of graphite masonry to reduce the class of radioactive waste "" LKIRO JSC ODC UGR", report on the results of the state contract dated 19.04.2016).

Thus, the existing technical proposals for the processing of irradiated NPP Carbon are aimed at extracting microimpurities of non-carbon nuclides of high specific activity, mainly from the surface of graphite blocks - the carbon masonry of the reactor, and making a relatively small contribution (5-10%) to the total activity of freshly extracted irradiated NPP Carbon. There are no methods for guaranteed reduction in the activity of the ^14C isotope during processing by 50-100 times, which ensures the transfer of these RW to hazard class 3 and higher for disposal at the unloading site, for irradiated Carbon NPP of any type of reactor and with possible levels of deviations of its initial activity.

The technical problem to be solved by a group of inventions related by a single inventive concept is the development of a method for the utilization of irradiated NPP Carbon, which makes it possible to reduce its residual activity after processing by 50-100 times or more for any type of reactor and with possible levels of deviations of its initial activity for further transfer of these RW to the 3rd hazard class, which provides the possibility of near-surface local disposal, or to the level of natural activity, as well as options for a device for processing irradiated NPP Carbon at the site of its unloading and reducing the radiation activity of the bulk of the irradiated NPP Carbon to a level that allows transfer to the class Hazard 3 and higher, allowing local near-surface disposal, or release into the natural environment in the case of the obtained natural level of carbon radiation activity.

The technical result consists in the use in the method of available and optimal in terms of their characteristics methods of purification of irradiated carbon from nuclear power plants from non-carbon radioactive microimpurities when carrying out a complex of chemical reactions to obtain a working gas from carbon, and then applying available methods of isotope separation in relation to the separation of carbon isotopes. At the same time, the process of gas separation into two main fractions is carried out to isolate the radioactive isotope ¹⁴ C from the irradiated carbon ^of the NPP in the gaseous form. the activity of the isotope ¹⁴ C is reduced by 50-100 or more times, up to the natural level of activity of ¹⁴ C.

Using the proposed method makes it possible to achieve the following features of the process of processing irradiated carbon from nuclear power plants:

- processing of this type of RW at the site of unloading from the reactor without transporting the entire volume of RW over distances of thousands to tens of thousands of kilometers to a deep disposal site (such transportation will be necessary only for volumes of high-level RW that are tens to hundreds of times less than the initial ones). At the same time, the main volume of irradiated NPP Carbon, after processing and reducing its activity by 50-100 times or more, is buried near the place of processing. And in the case of bringing to the natural level of activity at ¹⁴ C, it can be partially sold as a commercial product, and also safely returned to the natural environment;

- a fraction with a concentrated ¹⁴ C isotope or part of it, instead of being transported to a deep burial site, can then be used to obtain a commercial product based on ¹⁴ C;

- the versatility of the proposed method, which provides the possibility of processing irradiated carbon from nuclear power plants for any type of carbon-graphite reactors with possible fluctuations in the composition of radioactive waste in terms of chemical composition and activity;

- in the proposed method, the complex of technologies makes it possible to create a single production module that combines all technological flows of applied technologies of a universal nature, suitable for serial production at specialized plants with a processing capacity consistent with the amount of discharged irradiated carbon from a nuclear power plant for each individual complex of nuclear power plant reactors, near which it will be located.

The essence of the invention in terms of the method lies in the fact that the method of processing carbon irradiated in the NPP reactor, providing that a preliminary selection of the method of separation of carbon isotopes from the group of separation technologies is carried out: gas diffusion, nozzle method, gas centrifugation, aerodynamic separation method, laser method, further from the irradiated Carbon NPP receive a working gas to extract the isotope ¹⁴ C by the selected method of separation, then the isotope ¹⁴ C is isolated in a single-stage separation plant or a cascade of these plants for the separation of carbon isotopes, and separation in the separation plant, which is carried out to a level that ensures the production of in the 14С isotope- ^depleted extraction fraction from a single facility or cascade, the activity of the ^14С isotope is below the level that allows near-surface disposal of radioactive waste, and then sorting, compacting and differentiated disposal of radioactive waste, and return to nature waste with natural activity.

In particular cases of implementing the method for processing irradiated NPP Carbon, before processing the Carbon irradiated in the NPP reactor, the surface of irradiated Carbon blocks is cleaned from non-carbon microimpurities by chemical cleaning, mechanical cleaning.

In particular cases of implementation of the method for processing irradiated NPP carbon, mechanical grinding of blocks of carbon irradiated in the NPP reactor is carried out before manufacturing a working gas to extract ¹⁴ C isotope atoms.

In particular cases of implementing the method of processing irradiated carbon at nuclear power plants, before supplying the synthesized working gas to a separation plant for extracting ¹⁴ C isotope atoms, the working gas is cleaned from by-products of the working gas synthesis reaction at a plant that implements the method of rectification, adsorption, chemical exchange.

In particular cases of implementing the method for processing irradiated NPP Carbon, the capacity of each of the plants for processing irradiated NPP Carbon in terms of purification from non-carbon microimpurities, mechanical grinding of blocks of irradiated Carbon, production and purification of working gas is selected from the condition of not less than the productivity of a single separation plant or a cascade of such plants.

In particular cases of the implementation of the method for processing irradiated carbon from nuclear power plants, compounds from the group are used as a working gas for use in separation technology:

- methane, oxide, carbon dioxide (only for the gas diffusion method, gas centrifugation, aerodynamic separation method, nozzle and vortex process);

- mixed Fluorine-substituted methanes with one carbon atom in the molecule CF ₂ Cl ₂ (freon-12), CF ₂ HCl (freon-22);

- trifluoroiodomethane (CF ₃ I), trifluorobromomethane (CF ₃ Br), tribroiodomethane (CBr ₃ I) and iodomethane (CH ₃ J).

In particular cases of implementing the method of processing irradiated carbon, nuclear power plants choose the productivity of single-stage separation plants or a cascade of such plants from the condition of processing the available initial irradiated carbon from nuclear power plants for a predetermined number of years or the service life of separation plants.

In particular cases of implementing the method for processing irradiated carbon at nuclear power plants, the number of single-stage separating plants connected in series in a cascade is selected from the condition of obtaining the ^{14 C isotope activity level in the 14 C} isotope depleted fraction of the cascade, corresponding to the natural level of activity of this isotope in nature.

In particular cases of implementing the method of processing irradiated carbon from nuclear power plants, the fraction of selection of a single-stage separation plant or a cascade of such plants, depleted in the content of the ¹⁴ C isotope, is converted by chemical methods into compounds that are in a solid, liquid phase under normal conditions.

In particular cases of implementing the method of processing irradiated NPP carbon, the extracted ¹⁴ C isotope is processed in an additional cascade into products with highly enriched ¹⁴ C using enrichment technology by isotope separation methods from the group: diffusion method, Becker separation nozzle, gas centrifugation, vortex tube, aerodynamic separation.

The essence of the invention in terms of the device is that a device for processing carbon irradiated in a nuclear power plant reactor, containing a plant for processing Carbon into a working gas for a carbon isotope separation plant, the output of which is fed to the inlet of a separation plant, consisting of a single-stage separation plant, a cascade of series-connected single-stage installations with extractions of separated fractions of the working gas, in one of which the content of the ^14С isotope is higher than the initial content, and the fraction with the concentration of the ^14С isotope is reduced compared to the initial one to a level that allows near-surface burial.

In particular cases, in the facility for processing irradiated NPP carbon, before the installation for processing carbon irradiated in the NPP reactor into the working gas, a unit for chemical, mechanical cleaning of the surface of blocks of Carbon irradiated in the NPP reactor from non-carbon microimpurities is located.

In particular cases, in the device for processing irradiated carbon of the nuclear power plant, in front of the plant for the production of working gas, there is a mechanical crushing unit for blocks of carbon irradiated in the reactor of the nuclear power plant.

In particular cases, in the facility for processing irradiated carbon at a nuclear power plant, between the plant for manufacturing the working gas and the separating plant for extracting 14C isotope ^atoms , there is a plant for cleaning the working gas from non-carbon-containing by-products of the working gas synthesis reaction.

In particular cases, in a device for processing irradiated carbon at a nuclear power plant, a diffusion stage consisting of a filter and a compressor, a Becker separation nozzle with a compressor, a gas centrifuge, a vortex tube with a compressor, and an aerodynamic separation unit with a compressor .

In particular cases, in a device for processing irradiated carbon at a nuclear power plant, the separating cascade consists of series-connected single-stage laser complexes with gas reactors and installations for distillation, adsorption separation of pure working gas from a mixture of gases, as well as a compound containing a gas fraction enriched in the ¹⁴ C isotope, combined along a direct-flow scheme.

In particular cases, in the device for processing irradiated carbon at nuclear power plants, the flow of the fraction of the cascade enriched in the isotope ¹⁴ C, consisting of laser separation stages, is sent to the working gas production device for the countercurrent cascade, composed of single separation stages of other separation methods, and then the resulting working gas enters the counterflow separation cascade, which implements the separation method from the group: diffusion method, Becker separation nozzle, gas centrifugation, vortex tube, aerodynamic separation.

In particular cases, the device in the form of a single complex is located near the place of unloading irradiated carbon from the reactor or group of reactors of a given nuclear power plant, the place of local near-surface disposal of radioactive waste.

In particular cases, in a device for processing irradiated carbon at a nuclear power plant, the number of stages connected in series from single-stage separation plants in a cascade is selected from the condition of obtaining a level of activity ^{of the isotope 14 C} corresponding to the natural level of activity of this isotope in nature.

In particular cases, in the device for the processing of irradiated carbon at nuclear power plants, the pipelines for the extraction of both separated fractions after the separation plant are connected to the installations for the chemical conversion of gas flows after separation into a solid, liquid phase under normal conditions.

In particular cases, in a device for processing irradiated carbon at a nuclear power plant, the pipeline for the extraction flow depleted in the isotope ¹⁴ C to the level of the natural content of the fraction of the cascade of single-stage plants is connected to the installation of chemical, rectification processing into a commercial product, and to the pipeline for the release of excess extraction of the fraction into nature.

Description of drawings

In FIG. 1 shows a schematic diagram of the processing of irradiated NPP carbon after the separation method has been selected; FIG. 2 is a schematic diagram of the processing of irradiated carbon into a working gas, in FIG. 3 is a schematic diagram of a ¹⁴ C isotope separation device in a single separation plant, in FIG. 4 is a schematic diagram of a device for separating the ^14C isotope from irradiated carbon in a countercurrent cascade of single separation plants, in FIG. 5 is a schematic diagram of the device of a single laser separation unit, in FIG. 6 is a schematic diagram of the arrangement of a cascade of single laser separating installations, in FIG. 7 is a schematic diagram of a device for processing fractions of irradiated carbon after separation in a single separation plant or in a cascade of single separation plants: FIG. 7a) and 7b) - options for processing the fraction of the separation plant with a reduced content of ¹⁴ C; fig. 7c) - options for processing the fraction of the separation plant with a high content of ¹⁴ C, in Fig. 8 - reduction of waste of the 2nd class of radiation hazard, depending on the separation factor of the separation plant with a decrease in the activity of ¹⁴ C by a different number of times.

In the diagram of Fig. 1 are marked: 1 - unit for synthesizing the working gas from the irradiated Carbon of the NPP, 2 - procedure for transferring the flow of non-carbon radioactive microimpurities, 3 - block of the separation plant, 4 - block for compacting RW waste of the 2nd class of radiation hazard before transportation, 5 - procedure for transporting RW of the 2nd class to deep centralized disposal site, 6 - RW stream processing unit after the separation plant with reduced activity of the 14C isotope, ⁷ - transportation procedure to the near-surface disposal site, or 8 - procedure for release into the natural environment or commercial application.

In the diagram of Fig. 2 are marked: 9 - installation for the operation of mechanical cleaning of the surface of blocks of irradiated Carbon from non-carbon radioactive microimpurities, 10 - installation for the operation of chemical cleaning of the surface of blocks of irradiated Carbon from non-carbon radioactive microimpurities, 11 - installation for the operation of mechanical crushing of blocks of Carbon, 12 - installation for the operation purification of the synthesized working gas from by-products of non-carbon-containing synthesis reactions, 13 - installation for the operation of compaction of microimpurities isolated during the behavior of operations 9, 10, 12 for operation 2 - compaction and transfer of the flow of non-carbon radioactive microimpurities.

In the diagram of Fig. 3 are marked: 14 - the pipeline for supplying high-purity working gas with the initial content of the isotope ¹⁴ C C _F0 and the flow rate Q _F0 to a single separation device 17, 15 - the flow Qp of the fraction enriched in the content of the isotope ¹⁴ C separated in the device 17 with a concentration Ср>C _F0 , 16 - flow Qw of the fraction depleted in the content of the isotope ¹⁴ C separated in the device 17 with a concentration Cw<C _F0 .

In the diagram of Fig. 4 in addition to the symbols of FIG. 3 are marked: 18 - pipeline for supplying high-purity working gas with the initial content of the isotope ¹⁴ С C _F0 and the flow value Q _F0 - the feed input flow to the cascade, 19 - the selection flow of the cascade fraction enriched in ¹⁴ С, 20 - the selection flow of the fraction depleted in ¹⁴ С cascade, 21 - a device for regulating the values of flows transmitted from stage to stage of the cascade.

In the diagram of Fig. 5 are marked: 22 - IR laser, 23 - channel for inputting laser radiation into a gas reactor, 24 - gas reactor, 25 - window for inputting radiation into a gas reactor, 26 - circulation of a gas mixture with a working gas in a gas reactor, 27 - a compressor that provides circulating the flow of the mixture with the working gas in the gas reactor, 28 - the operation of removing the mixture of gases from the reactor after processing with IR laser radiation, 29 - the block for separating the reaction product from the mixture with a high content of the isotope ¹⁴ With concentration Ср>C _F and the flow Qp, 30 - block purification of the working gas with a reduced isotope content ¹⁴ With a concentration of Cw<C _F and a flow Qw, 31 - a unit for cleaning the mixture from the gas reactor and separating non-carbon-containing reaction products 32 - the operation of withdrawing non-carbon-containing reaction products for further disposal or commercial use.

In the diagram of Fig. 6 in addition to the symbols of FIG. 4, 5 are marked: 33 - a complex for a single stage of an IR laser, a gas circuit with a compressor, 34 - a pipeline for collecting non-carbonaceous reaction products in each stage for further disposal or commercial use, 35 - a pipeline for collecting a reaction product with a high content of the ¹⁴ C isotope, belonging to the 2nd class of radiation hazard, 36 - a pipeline for collecting the reaction product with a high content of the isotope ¹⁴ C, belonging to the 3rd and higher radiation hazard class, 37 - the selection of a fraction of steps enriched in ^14C belonging to the 3rd and higher radiation hazard class.

In the diagram of Fig. 7 in addition to the symbols of FIG. 1 and 4 are marked: 38 - production of working gas for the application of carbon isotope separation methods from the group of gas diffusion, nozzle method, gas centrifugation, aerodynamic separation method, 39 - cascade for obtaining a highly enriched ¹⁴ C isotope, 40 - compactization of working gas from fraction c reduced content of ¹⁴ C (dump) into a form for transportation to a place of centralized deep burial, 41 - the operation of manufacturing from a fraction of the cascade with an isotope content of ¹⁴ C≥0.1% of the commodity form of the product.

In FIG. Figure 8 shows graphs of the reduction of waste of the 2nd class of radiation hazard depending on the separation factor of the separation plant with a decrease in the activity of ¹⁴ C compared with its initial content in irradiated carbon by a given number of times: 8 times (graphs of Fig. 8a), 50 times (graphs Fig. 8b) and 10 ⁶ times (graphs of Fig. 8c).

Implementation of the invention

Processing of irradiated carbon involves four main stages:

First stage: choice of carbon separation method.

The choice of separation method determines the main equipment of the irradiated carbon separation unit and the list of working gases acceptable for the selected method. In this case, from all the allowable working gases for synthesis, other things being equal, it is necessary to choose the gas with the highest content of carbon atoms in the molecule: during the separation of isotopes in the gas phase, gas molecules containing different carbon isotopes are separated. Therefore, the higher the content of carbon atoms in the molecule, the greater the amount of carbon will be processed in the separation unit at the same volumetric gas flow rates through the unit.

At the same time, when choosing a separation method, it is also necessary to take into account not only the technical and cost parameters of the method, but also such factors as:

- existing experience in the development of equipment, its industrial production and operation of the selected separation technology on an industrial scale. Industrial technologies for isotope separation from the group of methods gaseous diffusion, nozzle method, gas centrifugation, aerodynamic separation method, laser method, suitable for the separation of carbon isotopes, are owned by a very small number of countries. These technologies are rarely exported by developers to other countries and only in the form of complete plants for the enrichment of uranium as fuel for nuclear power plants. Knowledge on the development of equipment, documentation for the manufacture of equipment is not transferred, therefore, the development of new projects for the production of other isotopes is excluded;

- in a number of countries that have experience in developing equipment for the above isotope separation methods, there are stopped and mothballed plants for enriching uranium isotopes, which is associated with excess production capacity in the world and insufficient competitiveness of production facilities that were stopped. In particular, such plants are available in the USA, France (diffusion separation method), South Africa (partially stopped the plant using the aerodynamic separation method), etc. A significant part of the equipment of these plants can be used to create a plant for the separation of irradiated carbon.

In view of the above, the choice of separation method and economic considerations and experience in separation technologies and in the establishment of an irradiated carbon processing plant may differ significantly for different countries.

The second stage: production of the working gas from the initial irradiated carbon from the nuclear power plant for the installation for the separation of irradiated carbon.

The irradiated carbon enters the working gas synthesis reactor in block 1, fig. 1. During the synthesis of the working gas in block 1, in almost all versions of the working gas, the working gas is cleaned from non-carbon radioactive microimpurities, which are presented, for example, in Table 1. The value of the total activity of these microimpurities in the initial composition of irradiated Carbon is relatively small, but in concentrated 50 -100 or more times the form of these microimpurities in terms of activity are small amounts of radioactive waste of the 2nd class. Therefore, these microimpurities are compacted in operation 2 and enter block 4 of collection, compaction and preparation for procedure 5 - transportation of RW of hazard class 2 to a deep burial site. The synthesized working gas enters block 3 - a separation plant, in which the working gas is divided into two main parts - the plant selection fractions:

- in the first part, significantly less (by 10-100 or more times) than the initial amount of the working gas that entered the separation plant, contains the main amount of the ¹⁴ C isotope from the original working gas. This fraction is hazard class 2 RW, therefore it enters unit 4 for compaction and preparation for procedure 5 - transportation of hazard class 2 RW to a deep burial site;

- the second part of the initial working gas, leaving the separation plant, has a low content of the ¹⁴ C isotope, which determines the 3 and higher hazard class of this type of RW, therefore it is subject to local near-surface disposal near the processing site. Before local disposal, in order to compact the volume of RW of the 3rd class, processing of the working gas is also carried out in block 6.

With sufficient separating power of separation unit 3, the main part of the fraction with a reduced activity of the ^14С isotope (or the entire volume of this fraction) can have a level of natural (natural) activity of the 14С isotope, therefore, in procedure ⁸ , it can either be processed, if necessary, into a commercial product, or processing and safe entry into the natural environment. If not the entire volume of the fraction with a reduced activity of the isotope ¹⁴ C has a level of natural activity of ¹⁴ C, then the remaining part is also subject to local disposal in procedure 7 as RW of class 3.

Additional preliminary cleaning of a thin layer of the surface of carbon blocks of irradiated Carbon, carried out by known chemical and mechanical methods from non-carbon impurities in operations 9, 10, fig. 2 is not fundamentally necessary, but in some cases it may be useful and desirable:

- firstly, it makes it possible to almost completely remove non-carbon radioactive impurities from the composition of irradiated carbon;

- secondly, as a result of a more stable composition of the carbon supplied for synthesis, it will ensure the standardization and stability of the technological process of working gas synthesis for any fluctuations in the chemical composition of the initial irradiated carbon.

Grinding of irradiated Carbon in operation 11, FIG. 2, by increasing the surface of the reacting components, it increases the efficiency of the working gas synthesis reactions.

In the schematic diagram of the synthesis of the working gas, Fig. 2, it is also possible to carry out operation 12 - removal of by-products of the synthesis reaction to obtain a working gas of high purity entering the separation unit 3, FIG. 1. In a separating plant, block 3 of FIG. 1, for any used separation methods, additional purification of the working gas from its chemical impurities will also occur, but their presence in the initial composition of the working gas requires additional costs for the separation power of the installation, the inclusion of devices for removing these impurities in its design, and can also lead to disruption of the system flow control of the separation unit.

The extracted microimpurities of non-carbon elements are collected, compacted in operation 13 and mixed - operation 2, fig. 1, with the flow of hazard class 2 RW compacted in block 4, obtained after the process of ¹⁴ C separation at the separation plant of block 3 and intended for transportation in procedure 5 to a centralized deep disposal site.

The main requirements for the connection of the working gas is its sufficiently high condensation pressure - at least 10 mm Hg. at normal temperature, high chemical purity and low corrosiveness in relation to structural materials. An additional, desirable requirement that simplifies the separation process is the uniqueness of the carbon atom in the compound - the working gas.

Separating plant, block 3 of FIG. 1, in terms of volume, cost of its equipment and operation, as a rule, is significantly higher than the equipment of other units of the installation for the implementation of the proposed method. To minimize the required volume of the separation plant as the main one, a continuous mode of its operation is required. Therefore, the productivity of all units of blocks 9, 10, 11, 1, 12 - preliminary purification of irradiated carbon, synthesis and purification of the working gas must be not less than the performance of block 3 - a single separation plant or a cascade of such installations.

There are a lot of possible carbon compounds that meet such requirements, and the choice is primarily determined by the separation method from the entire possible set of known and acceptable methods for isotope separation and ¹⁴ C extraction at stage 2. So, in the case of using gas diffusion, nozzle, vortex method , for the aerodynamic separation method, the most effective working gases are methane and carbon monoxide - CH ₄ , CO, for gas centrifugation - CO ₂ , for the laser separation method - mixed Fluorine-substituted methanes with one carbon atom in the CF ₂ Cl ₂ (freon-12) molecule, CF ₂ HCl (freon-22), trifluoroiodomethane CF ₃ I, tribromoiomethane CBr ₃ I, trifluorobromomethane CF ₃ Br and iodomethane CH ₃ J. For all these working gases, industrial production methods are known and available: in particular, for the synthesis of promising working gases such as CH ₄ , CO, CO ₂ the predominant method is the direct combustion of carbon in an atmosphere of hydrogen or ka working gas from impurity reaction products., to obtain Freon-22, a chain of reactions of industrial type C → CH ₄ (Methane) → CHCl ₃ (Chloroform) → CHClF ₂ (Freon-22) is possible.

Third step: in the single-stage separating plant of FIG. 3, or a cascade of these installations 17, FIG. 4, the separation of carbon isotopes is carried out. In the separating unit block 3, fig. 1, the synthesized high-purity working gas 14 enters, which at the outlet of the installation is divided into two streams - fractions 15 and 16, differing in the content of the ¹⁴ C isotope. Compared to the content of this isotope in the incoming stream, one of the fractions - 16 - has less flow content of ¹⁴ C - Cw - depleted, and the other - 15 - more - Ср - enriched. The separating plant provides a reduction in the content of the isotope ¹⁴ C in the depleted fraction by 50-100 times or more, compared with the initial content in the incoming stream. In this case, the flow of the depleted fraction Qw, 16 corresponds to class 3 and higher in terms of radiation hazard and can be subject to local near-surface disposal on site without transport operations over long distances. The flow of the enriched fraction - Qp, 15, is tens to hundreds of times less in mass than the initial volumes of irradiated carbon, while it has a radiation activity higher than the initial one, belongs to the 2nd class of radiation hazard and requires transportation to a centralized deep burial site.

The choice of a separation method from the above class of admissible and mastered in the industry is determined not only by the technical characteristics of the method, but also by the content of the ¹⁴ C isotope in the initial irradiated carbon, the experience in manufacturing and operating equipment for a specific separation method for organizations using the proposed method.

The separating plant in the general case, regardless of the separation method, is characterized by two main technical parameters - the value of the fraction separation factor for the isotope ¹⁴ C - α ₁₄ in the optimal technological mode, the value of the incoming flow Q _F (in the special literature - the feed flow of the installation) in this mode, where α ₁₄ is defined as:

The values of the flows of fractions Qw, Qp and the feed flow of the separation plant Q _F are related to the concentrations of the isotope ¹⁴ C in these fractions - Cw, Ср and the feed flow - C _F by the relations:

, то необходимое количество n ступеней каскада оценивается по формуле:from which it is possible to obtain the main dependencies necessary for the selection of a separation plant, including an estimate of the required number n (stages) of series-connected single separation units - a cascade. If the separation factor of a single installation is denoted as

, then the required number n of stages of the cascade is estimated by the formula:

Separation methods (“Isotopes: properties, obtaining, application.” Edited by V.Yu. Baranov, vol. 1, M.: Fizmatlit, 2005) differ significantly from each other in their characteristic features:

газодиффузионным методом максимально оценивается по формуле:- The gas diffusion separation method is based on the difference in the diffusion rates of light and heavy molecules through porous partitions with small diameter channels compared to the mean free path of molecules in a gas. Technically, a single separation unit (stage of the cascade) of the method consists of a compressor that pumps the flow along the porous partition (the so-called filter), on which the incoming flow is divided into two parts, and devices pumping these flows after the filter - also a compressor. Light molecules of the gas component predominantly pass through the partition - filter, and, since the diffusion rate is proportional to the square root of the molecular weight, a gas flow enriched in the lighter isotope will follow the partition. Separation factor of a single stage for the separation of irradiated carbon

gas diffusion method is maximally estimated by the formula:

where μ ₁₂ , μ ₁₄ is the molecular weight of the isotopic components of the gas mixture containing isotopes ¹² C and ¹⁴ C. The real difference from 1 coefficient is approximately 2-5 times lower than the maximum theoretical value. At the same time, from formula (5) follows the rationale for the desirability of the lightest carbon compounds when using the gas diffusion method: for example, for the CH ₄ compound, the separation factor of a single stage will be 1.2-1.4, for CO ~ 1.1-1.25 , and for CO ₂ ~ 1.07-1.2. This method was initially widely used for the enrichment of the 235 Uranium isotope in the USA, France, Great Britain, the USSR, and the PRC, but then the equipment was stopped due to lack of competition with other separation methods and was mothballed in a number of countries. The main reason for the low performance of the method is the huge energy consumption and the relatively lower separation factor of an individual stage (~1.02-1.05 for the separation of Uranium isotopes). At the same time, this method is characterized by high reliability and the possibility of processing large volumes of working gas, which is its positive characteristic in relation to the processing of irradiated carbon;

- The centrifugal method is based on the process of separating a mixture of gases due to the action of a field of ultra-high (0.5 million or more g-accelerations in the Earth's gravitational field) centrifugal forces acting on atoms and molecules. During centrifugation, the enrichment factor does not depend on the ratio of the masses of the atoms of the isotopes to be separated, but on their difference. The process is implemented in fast-rotating rotors of gas centrifuges. In a centrifuge rotor rotating at a high circumferential speed, heavier molecules are concentrated at the periphery under the action of centrifugal forces, and lighter molecules are concentrated at the centrifuge rotor. An axial circulation is created at the walls of the rotor due to gas-dynamic excitation and axial temperature difference. The selection of gases is carried out: from the outer part with heavy isotopes, from the inner part with light isotopes. The separation effect of a single gas centrifuge can be estimated by the formula:

- окружная скорость вращения ротора, а Т(К) - температура газа внутри ротора газовой центрифуги. Оборудование и технология для центробежного метода разделения разработано и используется при обогащении изотопов Урана в России, и в Западной Европе (концерн ЮРЕНКО), и разработчиками построены заводы и в США, Франции, КНР и других странах. В России существуют технологии, оборудование и промышленное производство, позволяющее производить изотопы Углерода по центробежной технологии. При разделении изотопов Углерода ¹⁴С и ¹²С газоцентрифужный метод дает оценку коэффициента разделения одиночной центрифуги

~ 1,2-1,8, при этом легкие соединения Углерода внутри ротора центрифуги практически невозможно удержать, поэтому рабочие газы должны иметь молекулярную массу не менее 30-40 а.е.м. - для российских газовых центрифуг, и не менее -120-150 а.е.м. - для центрифуг разработчиков других стран. Преимуществом метода являются минимальные, по сравнению со всеми остальными методами энергозатраты на разделение, поскольку процесс разделения проводится в режиме близком к термодинамическому равновесию. В то же время сравнительно невысокое газосодержание центрифуг требует применения очень большого количества машин при переработке объемов рабочего газа более десятков тонн Углерода в год. При этом резко возрастает и объем и стоимость установки даже при этих количествах;where k is a coefficient depending on the design of the centrifuge rotor, the gas temperature in the rotor and the organization of the circulation flow, usually the value of k is in the range of 4-20, and

is the circumferential speed of rotation of the rotor, and T(K) is the temperature of the gas inside the rotor of the gas centrifuge. The equipment and technology for the centrifugal separation method has been developed and used in the enrichment of uranium isotopes in Russia and Western Europe (YURENKO concern), and the developers have built plants in the USA, France, China and other countries. In Russia, there are technologies, equipment and industrial production that allow the production of carbon isotopes using centrifugal technology. When separating ¹⁴ C and ¹² C carbon isotopes, the gas centrifuge method gives an estimate of the separation factor of a single centrifuge

~ 1.2-1.8, while light carbon compounds inside the centrifuge rotor are practically impossible to keep, so the working gases must have a molecular weight of at least 30-40 a.m.u. - for Russian gas centrifuges, and not less than -120-150 a.m.u. - for centrifuges developed by other countries. The advantage of the method is the minimal, in comparison with all other methods, energy consumption for separation, since the separation process is carried out in a mode close to thermodynamic equilibrium. At the same time, the comparatively low gas content of centrifuges requires the use of a very large number of machines in the processing of working gas volumes of more than tens of tons of carbon per year. At the same time, both the volume and cost of the installation increase sharply even with these quantities;

- Aerodynamic separation - this method can be considered as a variant of centrifugation, but instead of swirling the gas in a centrifuge, it swirls when it exits a special nozzle, where it is supplied under pressure. This vortex effect technology has been used by South Africa (pilot implementation) and Germany. Vortex effect (Ranque-Hilsch Effect) - the effect of separation of a gas or liquid when swirling in a cylindrical or conical chamber into two fractions. A swirling flow with a higher temperature is formed at the periphery, and a swirling cooled flow is formed in the center, and the rotation in the center occurs in the opposite direction than at the periphery. The vortex effect is the effect of energy separation of compressible media in their swirling flow. The medium refers to gases, vapors, vapor-gas, vapor-liquid and other compressible mixtures. A vortex tube is a device designed to implement the vortex effect. It implements the effect of dividing the gas flow into cold and hot. Flow separation occurs in a cylindrical or conical chamber, the gas enters with pressure at a certain angle. A swirling flow with a higher temperature is formed at the periphery, and a swirling cooled flow is formed in the center, and the rotation in the center occurs in the opposite direction than at the periphery;

- Nozzle process (Becker process) - a process in which a gas flow is injected at high speed into a nozzle having a large curvature. The separation effect of the method is also based on the separation of the mixture in the field of centrifugal forces when flowing around a curved surface with a circular cross section. At the outlet, the flow is divided into two fractions by special cut-off knives. The process has been implemented in the industrial production of uranium isotopes. Both of the last considered separation methods have a significantly lower separation factor than the centrifugal method ~ 1.05-1.1, but are effective when working on light carbon compounds and can be used when processing large amounts of carbon - hundreds of tons or more per year. The disadvantages of these methods include the need for large energy costs associated with the operation of powerful compressors for input-output flows of working gases into the separation device;

- The laser separation method, unlike all previously considered, is based on a change in the activity of molecules containing different carbon isotopes during a chemical reaction under the action of laser radiation, the working gas. In this case, the constants of chemical reactions become different for different isotopes, and when the reaction is carried out, the concentrations of isotopes in the reaction products become different - separation occurs. A schematic diagram of a single device for laser separation of carbon isotopes is shown in Fig. 5. Initial working gas, pos. 14 enters the gas reactor 24. Inside the gas reactor, in addition to the working gas, for technological reasons, a fraction of a neutral, non-carbonaceous gas is often added. In the gas reactor, the circulation of the mixture with the working gas 26 is organized thanks to the compressor 27. One of the sides of the gas reactor is equipped with an optically transparent window 25 through which IR radiation 23 of the laser 22 enters the gas reactor. Under the action of the IR radiation of the laser, a chemical reaction occurs inside the gas reactor in which part of the working gas decomposes and other gaseous chemical compounds are formed. In this case, the concentration of the ^14C isotope in the carbon-containing reaction products will be higher than in the initial working gas. Laser radiation parameters - radiation frequency, power and pulse repetition rate, as well as circulation parameters of the mixture with the working gas in the gas reactor, such as mixture pressure, circulation rate and irradiation time of a portion of the mixture in the reactor, and others, are selected from the condition for obtaining the optimal flow rate power plant 14 and the resulting increase in the concentration of the isotope ¹⁴ C in the reaction product. From the condition of balance of the 14 C isotope entering the reactor and the exiting amount of the ¹⁴ C isotope - formula (2) - in this case, the concentration of the ¹⁴ C-Cw isotope in the remaining working gas will be lower than in the initial one, Cw<C _F . The resulting mixture is removed from the gas reactor - operation 28 is the operation of removing the mixture of gases from the reactor after processing with IR laser radiation. Further, this mixture is separated by chemical, physico-chemical methods into at least three fractions:

- in block 29 - separation from the mixture of the reaction product with a high content of the ¹⁴ C isotope with a concentration Cp>C _F and a flow Qp, then the purified product with a high content of the ¹⁴ C isotope is removed with a stream 15;

- in block 30, the working gas with a reduced content of the isotope ¹⁴ C is cleaned with a concentration of Cw<C _F and a flow Qw, then the purified working gas with a reduced content of the isotope ¹⁴ C is discharged with a stream 16;

- in block 31, the mixture from the gas reactor is purified and non-carbon-containing reaction products are isolated.

The volume of the output stream from block 31 is comparable and may be greater than the value of the stream 15 of the reaction product - the separated fraction Qp. Compounds of non-carbonaceous reaction products usually require disposal, but some components may have commercial use. Therefore, the concept provides for the operation 32 output of non-carbonaceous reaction products for further disposal or commercial use.

As applied to the separation of carbon isotopes by the laser method, the phenomenon of multiphoton dissociation (MPD) of carbon-containing molecules under the action of IR laser radiation is used. As carbon-containing molecules ("Isotopes: properties, obtaining, application." Edited by V.Yu. Baranov, vol. 1, M .: Fizmatlit, 2005 - ch. 8.3, Table 8.3.1), the effectiveness of exposure to CF ₃ compounds was found I, CF ₃ Br, CF ₂ HCl, CF ₃ COCF ₃ . The latter compound, due to the presence of three carbon atoms in the molecule and the "isotopic overlap" effect associated with it, is of little use for separating heavy carbon isotopes. A feature of the laser separation method is that the separation factor on a single device can reach values of 50–100 or more, and, compared with other methods, with small capital costs and the size of production areas, the volume of processed initial carbon can be also hundreds or more tons per year.

The laser method of IR multiphoton dissociation of CHClF ₂ has been industrially tested by irradiating a mixture of Freon-22 (CHClF ₂ ) with nitrogen in a reactor, as a result of which the probability of the formation of tetrafluoroethylene (C ₂ F ₄ - TFE) with the ¹³ C isotope and subsequent isolation of TFE increases. In the period 1999-2005 in Kaliningrad, CJSC "GA3-OIL" on the basis of the plant "Quartz" created industrial production, which carried out the primary enrichment of the isotope ¹³ C from ~ 1.1% (nature) to ~ 30%, further, this product was used to obtain commercial 99% ¹³ C by the centrifuge method. In this industrial production, a separation factor of ~50 was obtained.

In almost all cases and for all separation methods, the separation factor necessary for solving a technical problem is unattainable on a single separation plant and cascading is required - a series connection of single installations along the input-output flows of the separated fractions of single installations.

To increase the efficiency of working gas processing in terms of extracting the ¹⁴ C isotope - reducing the amount of the fraction enriched with this isotope - with more than 2-3 stages, the cascade should be built according to the countercurrent scheme, Fig. 4. In the scheme of the countercurrent cascade, fig. 4, flow 15 - the extraction of the fraction enriched in ¹⁴ C of the stage of the cascade with the number K enters the input of the stage K + 1 - subsequent and is part of the feed stream 14 for it. The selection stream 16 - the fraction depleted in ¹⁴ C of the stage K enters the input of the stage K -1 and is also part of the power flow 14 for it. The power flow of the entire cascade 18 enters - is added to the power flow of the stage K _F . From stage 1 of the cascade, a selection stream of the cascade fraction depleted in ¹⁴ C with a concentration of ¹⁴ C below the requirements of radioactive waste of the 3rd radiation hazard class is taken, and from the last stage of the cascade - n - the selection stream 19 of the fraction of the cascade enriched in ¹⁴ C, which is radioactive waste of the 2nd radiation class danger. The mode of operation of the stages of the cascade is set and optimized by the devices 21 to control the magnitude of the flows transmitted from stage to stage of the cascade. Such a cascade scheme makes it possible to choose the optimal values of the feed flow of single separation plants and increases the depth of processing of the initial working gas. In this case, each of the stages of the cascade can consist of several parallel-connected single separation plants.

The total number of single separating elements connected in parallel in a stage of a cascade - the "cascade width" - determines the total separating capacity of the separating plant and the volume of processing of the initial amount of working gas.

всех ступеней каскада. При этом в части каскада - в ступенях, расположенные на схеме фиг. 4 правее ступени, в которую осуществляется ввод потока питания каскада, концентрация изотопа ¹⁴С в рабочем газе выше, чем в потоке питания и увеличивается по мере приближения к отбору 19, а в другой части - в ступенях, расположенных на схеме фиг. 4 левее ступени, в которую осуществляется ввод потока питания каскада, концентрация изотопа ¹⁴С в рабочем газе ниже, чем в потоке питания и уменьшается по мере приближения к отбору 20. Меняя число ступеней в этих частях каскада можно изменять оптимальные концентрации ¹⁴С в отборах 19 и 20 каскада.The total number of stages of the countercurrent cascade - "the length of the cascade" - n determines the total separation factor of the separation plant α ₁₄ as a product of the values

all stages of the cascade. At the same time, in the part of the cascade - in the steps located in the diagram of Fig. 4 to the right of the stage into which the cascade feed stream is introduced, the concentration of the ¹⁴ C isotope in the working gas is higher than in the feed stream and increases as it approaches extraction 19, and in the other part - in the stages located in the diagram of FIG. 4 to the left of the stage into which the feed stream of the cascade is introduced, the concentration of the ¹⁴ C isotope in the working gas is lower than in the feed stream and decreases as it approaches extraction 20. By changing the number of stages in these parts of the cascade, it is possible to change the optimal concentrations of ¹⁴ C in the extractions 19 and 20 cascade.

By increasing the length of the part of the cascade with a reduced content of ¹⁴ C, it is possible to ensure the level of activity of this isotope in the selection of 20, corresponding to its natural level in nature, which will exclude the handling of this selection as radioactive material and part of this selection can be used for commercial purposes, the rest, if necessary. - after processing, it can safely enter the natural environment. By increasing the length of the part of the cascade with a high content of ¹⁴ C, it is possible to provide a concentration level of this isotope in the selection of 19 of more than 0.1%, corresponding to its commercial use.

The laser separation method, unlike all the others, as mentioned earlier, has fundamental features in cascading: the separated fraction of a single separation device with a high content of the ¹⁴ C isotope (enriched) is not a working gas.

Of course, it is possible to organize a cycle of chemical conversions of the obtained compound back into the working gas, but this will not only lead to a significant complication of the design and operation technology of the cascade, but also to significant losses of the 14C- ^enriched fraction during the chemical conversion. Studies of the operation of laser separation units for the enrichment of the ^13C isotope have shown the inefficiency or practical impossibility of organizing the procedure for the reverse redistribution of the compound of the enriched fraction into the working gas.

This feature leads to the impossibility of constructing a scheme of a countercurrent cascade, but when solving the set technical problem, the organization of the process of cascading a fraction depleted in the content of the ¹⁴ C isotope is possible. Schematic diagram of cascading laser single separation units is shown in Fig. 6.

The initial working gas 18 enters the gas reactor of the extreme right, the last stage of the cascade with the number n, pos. 33. After irradiation in stage n, the output stream from the gas reactor, as described above, is divided into three parts in blocks 29, 30 and 31, and after cleaning in block 30, the working gas with a reduced content of the ¹⁴ C isotope enters the inlet of the gas reactor of stage n- one. The purified separation product of stage n with a high content of the isotope ^14C from block 29 enters the pipeline 35 to collect the reaction product with a high content of the isotope ^14C and belongs to the 2nd class of radiation hazard, and non-carbon-containing compounds - reaction products isolated in block 31, enter the common pipeline of the cascade 34 and further in operation 32 they are disposed of or converted into a commodity form for commercialization.

All other stages of the cascade are connected in a similar way. This type of cascade can be called "co-current".

At the same time, to increase the volume of processing of the working gas in each stage, as well as for the countercurrent cascade, typical single laser separation installations can be connected in parallel, and the blocks 29, 30, 31 for processing the mixture stage leaving the gas reactors can be the same for all gas reactors. steps.

на одной ступени. При этом, по мере движения в каскаде потока рабочего газа в сторону фракции отбора каскада с пониженным содержанием изотопа ¹⁴С (уменьшения номера ступени каскада), концентрация изотопа ¹⁴С в продукте обогащенной фракции ступени с повышенной, по сравнению с концентрацией ¹⁴С в входящем потоке рабочего газа в ступень, также будет снижаться.Another feature of this scheme of the cascade is that the concentration of the fraction enriched in the ^14С isotope cannot exceed the concentration of ^14С of the initial working gas by more than the separation factor

at one step. At the same time, as the working gas flow in the cascade moves towards the cascade extraction fraction with a reduced content of the ¹⁴ C isotope (decreasing the number of the stage of the cascade), the concentration of the ¹⁴ C isotope in the product of the enriched fraction of the stage with an increased, compared with the concentration of ¹⁴ C in the incoming stream working gas per stage will also decrease.

With a sufficiently large number of steps in the cascade, it is possible to obtain in the main selection 20 a fraction of the cascade depleted in ¹⁴ C of the concentration of this isotope above the PAO class 4 up to the natural level of activity. In this case, the concentration of the ^14C isotope in the enriched fractions of the extraction stages, starting from a certain stage located between stage n and 1, will become lower than the concentration of ^14C according to the requirements for class 3 radioactive waste, and this will be true for all located to the left in the diagram of Fig. 6 steps. It is expedient to collect these stage extractions separately in the pipeline 36 into the selection stream 37, since it is intended for local near-surface disposal near the processing site.

In FIG. 8, based on relations (1)-(3), the dependences of the flow share Qw/Q _F and the decrease in the share of radioactive waste of the second hazard class (Q _F /Qp is the number of times) that require transportation to a centralized deep disposal site from α ₁₄ for a given decrease in activity are shown ^14С isotope in the depleted C _F /Cw fraction by a factor of 50 – fig. 8a and 8 times - fig. 8b and in Fig. 8c - 10 ⁶ times.

The choice of the reduction factor for the activity of the ^14C isotope in the main fraction of RW 50 times (Fig. 8b) corresponds to fairly typical cases of the composition of irradiated carbon freshly extracted from the nuclear power plant reactor (Table 1), equal to 8 (Fig. 8a) - practically the limiting case when still processed RW can be transferred to radiation hazard class 3, and the decrease in activity by 10 ⁶ times (Fig. 8c) - to the natural level of activity of the ¹⁴ C isotope in irradiated carbon after its processing.

In the case of C _F /Cw=8, FIG. 8a, in order to reduce the amount of radioactive waste of the second hazard class by 10-20 times (Q _W /Q _F > 90-95%), the separation factor of the installation α ₁₄ > 80-150 is required.

In the case of C _F /Cw=50 or more, FIG. 8b, in order to reduce the amount of radioactive waste of the second hazard class by 10-20 times, it is required to ensure the coefficient α _{14 of} the separation plant 500-1000.

In the case of C _F /Cw=10 ⁶ or more, FIG. 8c, the natural activity of radioactive waste is ensured and these wastes can be returned to the natural environment. To reduce the amount of radioactive waste of the second hazard class by 10-20 times, it is required to ensure the coefficient α _{14 of} the separation plant 1×10 ⁷ ÷1.8×10 ⁷ .

Estimates of the required number of stages of the cascade n according to formula (4) for different separation methods at various reduction factors for the activity of the ¹⁴ C isotope in the main fraction of RW (C _F /Cw) are given in Table 3.

Fourth step: converting the separated carbon containing working gas into a form suitable for transportation to a disposal site, release to the natural environment or for commercial sale.

A schematic diagram of the implementation of the fourth stage according to the proposed method is shown in Fig. 7. In the diagrams of FIG. 7a and fig. 7b, options for processing the fraction of the separation plant with a reduced content of ¹⁴ C. The withdrawal stream of a single separation plant or cascade 20 with the activity of the isotope ¹⁴ C of the corresponding RW of the 3rd radiation hazard class or higher enters the processing unit 6 of the RW flow after the separation plant with a reduced activity of the isotope ¹⁴ C. In this block, the RW flow from the gas phase is converted by chemical methods known for all working gases into compounds that are in the solid, liquid phase under normal conditions. Due to such compaction, the volume of these radioactive wastes decreases and it becomes possible to transport them and locally dispose them for a long period.

The scheme of Fig. 7b is intended for the case when the extraction stream 20 of a single separation plant or cascade has a natural activity of the ¹⁴ C isotope. In this case, the material of this stream in the form of a gas is not a radiation hazardous material, and, taking into account the high chemical purity after passing through the separation plant, is suitable for any application : the working gas for the separation plant itself can be a commercial product, such as CH ₄ , CO ₂ , freons, etc., or can be used to obtain raw materials for the chemical industry. During this processing, reactors are used to carry out chemical processing reactions, and to ensure the required purity of the commercial product, distillation and adsorption purification installations are used. Therefore, the task of processing stream 20 for block 6 is determined by commercial orders, and the remainder of this unclaimed product can be transferred to nature, including in the gas phase or after conversion in chemical processing reactors into compounds in the solid, liquid phase under normal conditions.

In the diagrams of Fig. 7c shows options for processing the extraction fraction 19 of the separation plant with a high content of ¹⁴ C. Stream 19 enters block 4, where it is transferred from the gas phase by chemical methods known for all working gases into compounds that are in the solid, liquid phase under normal conditions. Due to such compaction, the volume of these class 2 RW is reduced and it becomes possible to carry out procedure 5 - transportation of these RW to a centralized deep disposal site.

The ¹⁴ C isotope is widely used in scientific research, primarily in chronological studies of events 2-10 thousand years ago (“Isotopes: properties, obtaining application.” Edited by V.Yu. Baranov, vol. 2, M .: Fizmatlit, 2005, p. 520). Concentrated ¹⁴ C has commercial applications, but its concentration in class 2 radioactive waste obtained during the processing of irradiated carbon at nuclear power plants may not be sufficient. Therefore, after the main separation plant, part of the extraction of the ^14C enriched fraction of the installation is sent for additional re-enrichment in a cascade of a significantly smaller (10-100 or more times) volume compared to the main separation plant, and the separation methods at the main and additional separation plant may differ - the choice is determined by economic considerations for the cost of additional installation and the available experience in the manufacture of equipment and its operation. To do this, in block 38, the working gas is produced from a part of the selection stream 19 for the use of carbon isotope separation methods from the group of gas diffusion, nozzle method, gas centrifugation, aerodynamic separation method. (The laser method is unsuitable for an additional separation unit, since it does not allow cascading the effect of ¹⁴ C enrichment). Next, the resulting working gas enters block 39 - a separation cascade to produce a highly enriched ¹⁴ C isotope. The amount of required enrichment is determined by practical market demand, but the usual requirement is not less than ¹⁴ C≥0.1%. The selection of the cascade 39 with highly enriched ¹⁴ C enters block 41 for the operation of manufacturing the commodity form of the product by chemical methods, and the selection of the cascade with a content of ¹⁴ C reduced in comparison with the initial gas goes to block 40 for compaction - processing by chemical methods from gas into compounds that are in the solid, liquid phase under normal conditions. Further, depending on the activity value of the 14C isotope (RAW ² or 3 radiation hazard class), the material obtained in block 40 is combined with materials for processing RW in block 4 (RAW class 2) or block 6 of Fig. 7a - RW class 3.

If the same working gas is used in the main 3 and additional 39 separation plants, then the need to use in the scheme of Fig. 7 blocks 38 and 40 no.

The device for processing irradiated carbon according to the method, for the implementation of steps 2-4, is a single production complex operating in a continuous mode. To do this, block 1 of the device of the second stage of processing is connected by pipelines for transferring the gas phase to separation block 3 of stage 3, and the outlet of block 3 is connected by pipelines for transferring separated gas streams with different concentrations of the isotope ¹⁴ C and belonging to different classes of radiation hazard with blocks 4 and 6 for processing of these streams into a form for transportation to a centralized deep disposal site, a local near-surface disposal site, and into a form for commercial use. To ensure continuous operation of the device for processing irradiated carbon, the working gas capacities of blocks 1,4 and 6 are coordinated with the productivity of block 3.

The equipment used in the construction of all main units is known and in most cases manufactured by the industry. In the design of blocks 9 and 10 for mechanical and chemical purification of the initial irradiated carbon, installations for high-temperature surface treatment of the blocks of irradiated carbon using various reagents can be used, for example, based on the inventions of RU 2624270 priority 02.24. 11 carbon pre-treatment before the reactor 1 working gas synthesis - industrial mills for crushing various materials. The working gas treatment plants before being fed into the pipeline connecting the working gas synthesis unit and the separation unit are based on the well-known and used in the chemical industry systems for producing high-purity gases on column-type apparatuses using the technology of rectification, adsorption, and chemical exchange.

As already mentioned above, to ensure technical characteristics and reliability, all equipment of separation plants is produced only industrially and only in series.

The entire complex of equipment that implements the proposed method for processing irradiated carbon is based on the same chain of operations and industrially produced equipment. To account for each type of composition of irradiated carbon unloaded from the reactor, the complex for processing irradiated carbon is built according to the modular principle as a single production site, which will minimize the length of process flows and pipelines and reduce the area of radiation-hazardous production.

To minimize transport operations, improve the safety and environmental friendliness of procedures for disposing of irradiated carbon, it is useful to locate this complex in close proximity to the place of unloading of irradiated carbon from a particular reactor or group of reactors of a given nuclear power plant and the place of the proposed local disposal.

In case of remoteness of the proposed site of local disposal of RW of the 3rd class of radiation hazard from the NPP, from the point of view of minimizing transportation costs and radiation safety, the transportation of RW of the 3rd class of hazard is more preferable than the transportation of RW of the 2nd hazard class. Therefore, in this case, for the NPP irradiated Carbon processing and disposal complex, it is more preferable to locate it near the site of RW unloading from the reactor or group of reactors of this NPP.

The amount of irradiated carbon unloaded from the reactors of a nuclear power plant after its shutdown, depending on its capacity, design, etc. may differ, but for almost all industrial nuclear power plants it ranges from 2 to 10-15 thousand tons.

The proven service life of separation equipment for various methods of isotope separation ranges from 15 to 50 years. Therefore, the separation plant as part of a single production module for the processing of irradiated carbon, like all other equipment of the module, must have a capacity such that during this time it will be possible to process the entire volume of irradiated carbon unloaded from the reactor. Estimates show that the required capacity of the module is 100-500 tons of carbon per year, and taking this into account, for each complex for processing irradiated carbon located near a particular nuclear power plant, the productivity of single-stage separation plants or a cascade of such plants is selected from the condition of processing the available initial irradiated carbon of the nuclear power plant for a predetermined amount years or service life of separation plants. Single separating plants, including those from which, if necessary, a separating cascade is created, are serial-type with a limited set (one to three types) of volumetric productivity values for the working gas supply flow. In this case, the performance of the separation plants of the complex varies depending on the number of single-stage plants installed in parallel.

Therefore, the present invention is implemented with the help of universally available modern equipment, using substances that are widely used in the industry.

Claims (24)

1. A method for processing carbon irradiated in a nuclear power plant reactor, providing that a preliminary selection of a method for the separation of carbon isotopes from the group of separation technologies is carried out: gas diffusion, nozzle method, gas centrifugation, aerodynamic separation method, laser method, then working gas is obtained from the irradiated carbon of the nuclear power plant for extraction of the 14C isotope ^atoms by the selected separation method, then the ^14C isotope is isolated in a single-stage separation plant or a cascade of these plants for the separation of carbon isotopes, and the separation in the separation plant is carried out to a level that ensures the production of a selection fraction depleted in the content of the ^14С isotope from a single installation or cascade, the activity of the ¹⁴ C isotope is below the level that allows surface disposal of radioactive waste, and then sorting, compacting and differentiated disposal of radioactive waste, and returning waste with natural activity to nature. 2. The method according to claim 1, characterized in that before processing the irradiated Carbon from the NPP, the surface of the irradiated Carbon blocks is cleaned from non-carbon microimpurities by chemical cleaning, mechanical cleaning. 3. The method according to p. 1, characterized in that before the manufacture of the working gas to extract the isotope ¹⁴ C atoms, the blocks of carbon irradiated in the NPP reactor are mechanically crushed. 4. The method according to any one of paragraphs. 1, or 2, or 3, characterized in that before the synthesized working gas is supplied to the separation plant for extracting ¹⁴ C isotope atoms, the working gas is cleaned from by-products of the working gas synthesis reaction at the plant that implements the method of rectification, adsorption, chemical exchange. 5. The method according to any one of paragraphs. 1, or 2, or 3, characterized in that the performance of each of the NPP irradiated Carbon processing plants in terms of purification from non-carbon microimpurities, mechanical grinding of irradiated Carbon blocks, production and purification of working gas is selected from the condition of not less than the performance of a single separation plant or cascade such settings. 6. The method according to any one of paragraphs. 1, or 2, or 3, characterized in that compounds from the group are used as a working gas for use in separation technology: - methane, oxide, carbon dioxide (only for the gas diffusion method, gas centrifugation, aerodynamic separation method, nozzle and vortex process); - mixed Fluorine-substituted methanes with one carbon atom in the molecule CF ₂ Cl ₂ (freon-12), CF ₂ HCl (freon-22); - trifluoroiodomethane CF ₃ I, tribromoiomethane CBr ₃ I, trifluorobromomethane CF ₃ Br and iodomethane CH ₃ J. 7. The method according to claim 1, characterized in that the productivity of single-stage separation plants or a cascade of such plants is selected from the condition of processing the available initial irradiated carbon from a nuclear power plant for a predetermined number of years or the service life of separation plants. 8. The method according to p. 1, characterized in that the number of single-stage separation plants connected in series in a cascade is selected from the condition of obtaining a ¹⁴ C isotope activity level corresponding to the natural level ^of activity of this isotope in nature . 9. The method according to claim 1, characterized in that the ¹⁴ C isotope-depleted fraction of the selection of a single-stage separation unit or a cascade of such units is chemically converted into compounds that are in a solid, liquid phase under normal conditions. 10. The method according to claim 1, characterized in that the extracted ¹⁴ C isotope is processed in an additional cascade into products with highly enriched ¹⁴ C using the technology of enrichment by isotope separation methods from the group: diffusion method, Becker separation nozzle, gas centrifugation, vortex tube, aerodynamic separation. 11. A device for processing carbon irradiated in a nuclear power plant reactor, containing a plant for processing Carbon into a working gas for a carbon isotope separation plant, the output of which is fed to the inlet of a separation plant, consisting of a single-stage separation plant, a cascade of series-connected single-stage plants, having selections of separated fractions of the working gas, in one of which the content of the ^14С isotope is higher than the initial content, and the fraction with the concentration of the ^14С isotope is reduced compared to the initial one to a level that allows near-surface burial. 12. The device according to claim 11, characterized in that before the plant for processing carbon irradiated in the NPP reactor into the working gas, a unit for chemical, mechanical cleaning of the surface of blocks of Carbon irradiated in the NPP reactor from non-carbon microimpurities is placed. 13. The device according to claim 11, characterized in that before the installation for the production of working gas there is an installation for mechanical crushing of blocks of carbon irradiated in the NPP reactor. 14. The device according to any one of paragraphs. 11, or 12, or 13, characterized in that between the installation for the production of working gas and the separation plant for extracting the isotope ¹⁴ C atoms, a plant for cleaning the working gas from non-carbon-containing by-products of the working gas synthesis reaction is placed. 15. The device according to claim. 11, characterized in that as a single-stage separation plant for the design of a counterflow type separation cascade, a diffusion stage is used, consisting of a filter and a compressor, a Becker separation nozzle with a compressor, a gas centrifuge, a vortex tube with a compressor, an aerodynamic separation unit with compressor. 16. The device according to claim 11, characterized in that the separation cascade consists of series-connected single-stage laser complexes with gas reactors and installations for distillation, adsorption separation of pure working gas from a mixture of gases, as well as a compound containing a gas fraction enriched in the ¹⁴ C isotope combined in a direct-flow scheme. 17. The device according to claim 16, characterized in that the flow of the fraction of the cascade enriched in the isotope ¹⁴ C, consisting of laser separation stages, is sent to the working gas manufacturing device for the countercurrent cascade, composed of single separation stages of other separation methods, and then the resulting working the gas enters the countercurrent separation cascade, which implements the separation method from the group: diffusion method, Becker separation nozzle, gas centrifugation, vortex tube, aerodynamic separation. 18. The device according to any one of paragraphs. 11, or 15, or 16, or 17, characterized in that the device in the form of a single complex is located near the place of unloading irradiated carbon from the reactor or group of reactors of this nuclear power plant, the place of local near-surface disposal of radioactive waste. 19. The device according to any one of paragraphs. 11, or 15, or 16, or 17, characterized in that the number of series-connected stages from single-stage separation plants in the cascade is selected from the condition of obtaining the ¹⁴ C isotope activity level, corresponding to the natural level ^of activity of this isotope in nature. 20. The device according to claim 11, characterized in that the pipelines for sampling both separated fractions after the separation plant are connected to the installations for the chemical conversion of gas flows after separation into a solid, liquid phase under normal conditions. 21. The device according to claim 19, characterized in that the pipeline for the extraction flow depleted in the ¹⁴ C isotope to the level of the natural content of the fraction of the cascade of single-stage installations is connected to the installation for chemical, distillation processing into a commercial product and to the pipeline for releasing excess fraction selection into nature.

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