RU2090948C1 - Method and device for decontaminating nuclear power plants - Google Patents

Abstract

FIELD: nuclear power engineering. SUBSTANCE: contaminated unit is placed in pressurized chamber, spaces of chamber and unit ate connected to vacuum installation, flexible container with conducting external layer is inserted in unit space and filled with chemically active decontaminating solution. Decontamination is carried out by using electrochemical method; flexible container functions as one of electrodes and walls of nuclear power unit, as other electrode. Electrolysis is performed while solution is circulating doped in the process with gas-filled destructable-wall bodies. Dirty decontaminating solution is discharged to radionuclide compartment for further burial; fresh portions of solution are introduced in remaining quantity. Procedure is made until MPC norms are complied with. Decontaminating device is equipped with instrumentation and numeric-control unit, chamber for decontaminating nuclear power plant units connected in series with coarse and fine liquid-phase cleaning chambers. Coarse cleaning chamber is of variable sectional area and has diaphragms and separator placed at its outlet and provided with two pipes for discharging liquid to fine cleaning chamber and for supplying gas to remove radionuclides. Fine cleaning chamber has three chambers separated by membranes with cavities. Walls of one of them (central one) have cavities and depressions. Shaft installed along central chamber axis carries cup on its end with mushroom-shaped swirler and conical splitter to separate liquid from gases and solid admixtures. Aerosol collector is placed at outlet of three chambers. EFFECT: improved efficiency and capacity of decontamination process, reduced amount of wastes subject to storage, improved reliability, facilitated procedure. 5 cl, 10 dwg

Description

 The invention relates to physicotechnological processes for the decontamination of structures of nuclear power plants during their rehabilitation for use in primary and secondary energy-producing processes.

 The closest way is the process of decontamination of nuclear power plants, including the removal of a layer of material from the design of a decontaminated object having increased activity, packaging of radioactive waste and their subsequent placement in a repository or temporary disposal sites.

 The closest device for implementing the method of decontamination of nuclear installations is a device containing a chamber for processing a contaminated object, an electrode, a supply line for a working agent and removal of liquid and gas phases.

 Significant disadvantages of the known method of decontamination are the high energy intensity of the process, low efficiency caused by significant specific energy consumption and expenditure of the working agent per unit area of the decontaminated surface of the structure due to the static model of this process and the absence of a change in the cleaning processes of the working agent involved in the decontamination of the structure of the structure of a nuclear power plant, which leads, in addition, to the need for containerization and disposal of significant volumes used in working agent, and a low degree of deactivation of the object makes it difficult to use the basic processes.

 A significant disadvantage of the known device is its low productivity at significant costs of the working agent, caused by constant losses of the agent due to its discharge after the first contact with the design of the decontaminated object, which leads to the alienation of significant areas for waste storage facilities.

 The technical result of this invention is to increase the efficiency of the method and productivity of the device, to increase efficiency by eliminating the losses of the working agent and reducing the amount of waste to be disposed of, as well as to increase the reliability and technological culture of the whole process.

 This technical result in a method for the decontamination of nuclear power plants, including the removal of a layer of material from the design of a decontaminated object having increased activity, packaging of radioactive waste in containers and their subsequent placement in the repository, due to the fact that the deactivated object is placed in a sealed chamber, connect the cavity of this the chambers and the cavity of the deactivated object with a vacuum installation, the volume of the internal cavity of the deactivated object is reduced by introducing an elastic container into it a spine, the outer surface of which is made of an electrically conductive material, the structure of the object and the electrically conductive material are connected to different poles of the current source, an aggressive working agent is circulated between the walls of the object and the electrically conductive material, gas-filled bodies with a destructible outer film are introduced into this agent, and, as they accumulate in the working agent of radioactive waste, part of the agent is allocated for separation, enrichment with flocculants and packaging in containers, restore the volume and the concentration of the agent circulating in the inner cavity by introducing an additional amount, the process is carried out until the set activity standards are obtained in the withdrawn agent according to the MPC, by which they judge the completion of the decontamination process.

 At the same time, an alternating electric potential is applied to the electrodes (the installation case of the electrically conductive material), an aggressive acid solution is used as the working agent, the circulating working agent is additionally subjected to acoustic impact, which decreases as the contaminated surface is cleaned, and after the decontamination of the object is completed, the electrode is removed from the object cavity and subjected to decontamination.

 Before the process, the electrically conductive material is coated externally with a film having caverns.

 A device for the decontamination of nuclear power plants, containing a chamber for processing a contaminated object, an electrode, a working agent line and removal of liquid and gaseous phases, is additionally equipped with a coarse filter for the liquid phase and a camera for fine finishing the liquid phase, connected in series with the camera for processing the object, while the electrode made in the form of an elastic container, on the outer surface of which an electrically conductive material is applied, and the electrode is made with the possibility of placing it in the inner the cavity of the object to be deactivated, the coarse cleaning chamber of the liquid phase is made variable in cross section and equipped with membranes having caverns and holes, the outlet of this chamber is equipped with a separator in the form of a perforated plate with needles and a mustache, the separator has two nozzles for discharging gas and liquid phases, while the liquid phase outlet pipe is connected to the input of the fine finishing chamber having an intermediate, annular and central chamber, of which the central chamber has hollow spherical walls with liquid inlet and outlet openings phase and production in the form of oblique cavities, the annular chamber has membranes with perforation and caverns, the output of the central chamber is connected to the bell communicated by means of a perforated cylinder and a perforated bridge with an aerosol collection cavity, needles with an inclination to the flow are fixed in the bell on the strings, and along in the bearings of the axis of the central chamber, a shaft is installed in the bearings with a bowl at its end, made in the form of a mushroom-shaped swirler and a divider, the bed of the bowl is connected to the perforated cavity through a mesh bottom and tubes astruba.

 At the same time, membranes installed in the annular chamber have screw regulators for their tension.

 In FIG. 1 shows a general view of a device for the decontamination of nuclear power plants; in FIG. 2 view of the working chamber with a deactivated installation; in FIG. 3 section of the working chamber with technological equipment; in FIG. 4, 5 and 6 show the details of the device and installation; in FIG. 7 a section along AA in FIG. 3 devices; in FIG. 8 and 9 show the processing units of the working agent; in FIG. 10 knots with a fine finishing chamber for a working liquid agent.

 The device for the decontamination of nuclear power plants 1 (NPP) has a control panel 2 connected by command and feedback channels to a power unit 3 having a unit 4 for preparing a liquid working agent and an exhaust ventilation unit 5. The panel 2 is connected to a sensor unit 6 for monitoring background radiation and pump station 7 for supplying the working agent from the node 4 to the working chamber. The device also has a node 8 connected to the backup chamber 10, a return working agent and a container 11 for collecting a low-concentration working agent, as well as a neutral gas supply unit 9 to the working chamber. The collection of liquid radioactive waste of medium concentration is carried out in a container 12, a high concentration in the container 13. To supply the working agent and empty the containers there is a source of compressed gas 14 to pressurize these containers.

 The contaminated object 1 is located in the processing chamber 15 and connected to the pole of the current source, and the second pole is connected to the electrically conductive material 16 introduced into the cavity of the deactivated object 1 having a neck 17 and a hollow shaft 18 located in its housing with a spiral impeller 19 at the lower end .

 The processing chamber 15 of the object 1 has nozzles 21 for supplying a working agent and a nozzle 22 for discharging gas phases into the exhaust ventilation unit 5; lower pipe 23 / Fig. 3 / discharge of spent liquid phases; also has an elastic-flexible guide sleeve 24, through which an elastic container 25 is introduced into the cavity of the object 1 with an electrically conductive material 16 placed on it that acts as an electrode, and to fix a given gap between the electrodes / pair: 1-16 /, dielectrics 27 are fixed on the electrode 16, defining a gap 28 / Fig. 5/. If necessary, the electrode 16 is protected from the outside with a polymer film 29, preventing the electrode material from overgrowing during its operation.

 The agent supply pipe 30 is mechanically connected to a current-carrying cable 31 supplying electric potential to a pair of electrodes 1-16. The pipe 30 is made coaxial: the outer pipe 32 and the inner pipe 33, from which the working agent is fed through the tubes 34 to the gap 8. The sleeve 26 has an annular seal 35 on the neck 17 and an annular seal 36 pressed against the upper neck of the deactivated object 1. The gas from the gap 28 is carried out through the outlet pipe 37 to the filters of the exhaust system 5.

 To activate the process of removing radioactive material from the walls of the housing 1, acoustic generators 38 are mounted on its outer surface, preferably magnetostrictors, which are especially effective in removing local deposits of radioactive material / Fig. 4 / on the wall of the housing 1. To remove such deposits, use / prior to introducing into the cavity of the housing of the vessel 6 / a working member 39 in the form of a tube with a nozzle through which an acid solution is supplied to the RAW spot and simultaneously acted by electrohydraulic shock, applying a 40-bit to the electrodes voltage.

 Level control, change of a part of the working agent is carried out through a coaxial pipe 30, taking the agent through perforations 41 in the outer pipe 32, and using the pipe 32 and 33, it is possible to not only add the agent, select it for analysis of samples by MPC, but also circulate agent in the working gap 28 of the capacity of the housing 1, which is the working chamber of its decontamination.

 When deactivating reactor compartment structures having a monolithic section / Fig. 2 / with a capacity of 25 capture this unit 42, creating the same conditions for the electrode made in the form of a grid 16. Gas-filled bodies / balls / with a soluble wall in the working agent are periodically introduced into the cavity 28. 0 Such an operation is carried out through the pipe 30.

 Part of the radioactive waste is planted on the electrode 16. The other part, where suspended RAW particles are present, is withdrawn through the hollow shaft 18 and the nozzle from this hollow shaft “from 18” / Fig. 8 / into the unit 43, connected by the transition nozzle 44 and the forces of the background 45 with this shaft for supplying to the processing chamber of the unit 43 of the indicated withdrawal part of the radioactive waste. For this treatment, there are membranes 46 in the chamber with cavities and openings 47 for uniform distribution and processing of radioactive waste. To enter the membranes into self-oscillation mode, they are connected at the ends with springs 48 fixed to the output of the nozzle 44. To control the temperature of the treatment, the chamber has a jacket 49 into which neutral gas of a given temperature and pressure is supplied through the pipe 50.

At the outlet, the chamber is equipped with an outlet flow separator. This separator 51 has a perforated plate 52 / FIG. 8 and 9 / with a pointed and bent at the ends of the mustache 53 and 54. The plate has perforations / many holes / 55 and needles 56 for crushing and separating the outgoing liquid into a gas phase / gas aerosol / discharged through a bellows 57 and a nozzle 58 to a vacuum installation 5 for separation on filters / for example, Petryanov /; the liquid phase containing heavy RAW particles is discharged through the bellows adapter 59 and the pipe 60 to the final stage of fine purification: pure liquid, gas pure phase and solid residue. In operation, the unit 43 is fed with additional gas through the pipe "P" / Fig. 8 / from among neutral gases, for example, CO ₂ , He; for capture and removal of ionized gas from the plate 52 by the method of low-pressure gas-liquid flotation of this shared stream. Finer cleaning is carried out using the device developed by the applicant for this / as well as the above devices / apparatus connected to the pipe 60 / Fig. 10 / and having a housing 61, mainly in the form of a cylinder having an outlet pipe 62 on the other side. A chamber 63 is made in the cavity of the housing, in the form of a ring and a camera 64 in its central part, both chambers are powered by an intermediate feed receiving chamber 65 through the pipe 60 The annular chamber has inlet nozzles 66, 67 and 68 supplying liquid to separate cavities of the chamber 63 formed by annular membranes 69 and 70, thus obtaining three annular cavity-subchambers 71.

 The membrane 70 is made by analogy with the membrane 46 / Fig. 8 / and has caverns on its surface with recesses of craters by 5-10 times the thickness of its wall, and the membrane 69 has perforations / holes / 72 for uniform multi-jet bypass of the liquid. For tensioning the membranes 69 and 70 there are screws 73 / in the section of FIG. 10 shows only the membrane screw 69; the screws of the membrane 70 pass through the membrane 69, through the hole in it one of these screws is shown on the left axis. The cavities of the sub-chamber 71 are connected by openings 74 and 75 to a conical chamber 76, from which gases and purified liquid are technologically planned removed; the gas carries the entire balance of radioactive impurities for their final filtration and containerization.

 The central chamber 64 is shaped: it contains convex hollow spherical walls 77 with holes 78 and 79, where the holes 79 are 1 / 5-1 / 10 D larger than the holes 78, where D is the diameter of the holes. 78. In this case, the walls of the chamber 64 have a working 80 and 81 in the form of oblique caverns with the exit direction upward along the axis of the chamber / Fig. 10/.

 A shaft 82 is located along the axis of the chamber 64 in the bearing 83, having a mushroom-shaped bowl 84 in the upper part with tubes 85 connected to it, over which needles 87 are fixed on the strings 86 on the strings 86, having an inclination relative to the vertical axis, designed to ionize the stream being washed gas-liquid medium.

A cylinder 88 is installed above the conical chamber 76 with a horizontal annular jumper 89 having openings 90. The wall of the cylinder 88 also has openings 91, but inclined downwardly into the gas collection chamber 92, where gases also enter from the cut 93 of the openings 90. The annular collecting chamber 92 has interconnected the calculated values of "H" and "B", which determine its capacity, eliminating the ingress of liquid into it from the central stream discharged to the pipe 62. For this, in front of the pipe 62 there is a chamber formed by cones 94 and 95 with a line 96 connecting them with large bases, take into account which widen the angle of expansion of the outlet jet within 10-14 ^° , which ensures the collection in the chamber 92 of only gas phases and gas aerosols with finely dispersed radioactive waste, which are removed from the openings 97 for purification c in block 5 in the gas stream.

 The whole structure of this apparatus / FIG. 10 / is highly productive, original and progressive / for further use and development in terms of selective removal of aerosol phases /.

 The shaft 82 is connected to the drive of its rotation by command from the console 2, and the upper mushroom-shaped bowl 84 has a central divider 98, a peripheral flow swirl 99 in the transitional bed of which / from the swirl 99 to the divider 98 has a sinus, overlapped by a grid 100 for collecting gases at the bottom of the bowl and their removal through the tubes 85 and the chamber 76 into the chamber 92 with further disposal through the vacuum unit 5.

 This design of the device, including blocks of preliminary treatment of radioactive waste / Fig. 1-7 /, post-treatment unit / Fig. 8, 9 / and the node for fine fine cleaning of radioactive waste, allows you to conduct the entire process of decontamination of the surface stricture / to a depth of 2-3 mm / of the nuclear reactor 1 in a continuous and autonomous mode during the processing and disposal of the metal casing 1, environmentally safe processing of liquids and gases, containerization and burial of all types of radioactive waste: solid residue released with gases of aerosol phases and residual highly radioactive liquid.

 The operation of the described installation / Fig. 1-10 / is carried out in the sequential mode of switching on all units and devices connected by transitional pipes, connected by direct and feedback connection with control unit 2 of the entire process of decontamination of the RAM. The work begins with checking and debugging the instrumentation of the entire specified critical technological chain, checking exhaust ventilation and sanitary protection on the units.

 Further, the use of the described nodes, blocks and apparatus of the installation is carried out when implementing the process according to the method.

 The method of decontamination of nuclear power plants using the described device is as follows.

 Given that during operation the building 1 was exposed to radioactive substances (RAV) in the form of isotope-exchange diffusion processes, multicomponent ion-exchange adsorption, the literal and spatial distribution of radionuclides, this led to induced and residual radioactivity of the building 1, a high background inside the case, according to laboratory examination up to 10-20 R / h; outside on the wall of the housing is 0.1-0.2 R / h, i.e. a very high background value.

 To deactivate such a highly active object of the atomic compartment located in a very cramped geometric space / Fig. 3 /, developed the only effective stand-alone method for this technology. At the same time, a guide sleeve 26 is inserted into the neck 17, it also protects against loss of deposition of RAB on the grid-shaped electrode 16 when it is removed together with the parasitic capacitance 25. The tank 25 in which there is an elastic pipe 30 with a current-carrying cable 34 in the folded / in the form of a serpentine, or bellows / form is introduced along the guide 26 into the cavity of the housing 1; serves under pressure "P" the compressed medium / liquid /, this leads to the expansion of the container in the cavity of the housing and fixing it in it by means of tracking crackers 27 / Fig. 1.3.5 /. Then in the gap 28 serves a working agent; the second agent is filled with gas-filled bodies, balls, and the third agent is current to the housing 1 and the mesh electrode 16, forming the process of electrochemical transfer from the housing to the electrode on which the radioactive waste is deposited. As a working agent, a mixture of acids of sulfuric and HCl or sulfuric and HF; or nitric of the same depassivator from hydrohalic acids.

In this case, pressure and capacity are monitored and, accordingly, in the gap 28 and acid temperature are controlled, controlling the decontamination process. The temperature is selected from 25 to 80 ^o C at an overpressure in a pressure of 1.05-1.2 kgf / cm ² . The decontamination technology begins when a current is supplied to the housing 1 and the electrode 16, while the layer dissolves on the inner surface of the housing 1 and the ions transfer, including radionuclides, to the electrode 16, which forms a compact radioactive deposit on the electrode 16. The concentration of radioactive waste in the acid solution is determined by sampling through a pipe 32-41 // control MPC //. In the process, it is possible to detach RW from the walls and shed them to the bottom. In this case, by feeding the solution, the gap is washed and the waste is drained through the pipe 23 and the container 11, 12.

 The concentration of the acid solution can be changed due to its circulation from the gap 28 through the tube and back after enrichment / adjustment of its chemical content /.

 The current and voltage of the electric potential are also adjusted within the current range of 20-50 A, the voltage of 30-50 V at reduced / to atmospheric / pressure in the processing chambers from 0.9 to 0.8 atm, which ensures active gas evolution and prevents emission from the chambers of radioactive gases. As the housing 1 is deactivated, metals (iron, chromium, nickel, etc.) that carry radioactive waste / strontium, cesium, cerium, uranium, plutonium, etc. / accumulate on the electrode 16, while heavy particles fall to the bottom and their transported by the hydrodynamic current of the electrolyte along the rotating shaft 18 for further separation in the unit 43 and the apparatus 61 of the technological complex, and the gases are removed through the pipe 22 to the filter unit 5 / Petroyanova or others /.

 Part of the electrolyte from the bottom of the casing is impelled by the impeller 19 and raised together with particles that have fallen to the bottom and are not subject to landing on the electrode 16, i.e., those particles that are not amenable to electrical processing in the electrolyte and are neutral and passive to the action of the electric field / mainly mineral particles materials accumulated during reactor operation during assembly and disassembly of assemblies, fuel rods, resolution of insulating material, etc. inclusion / discharge into the unit 43 and subjected to intensive flow treatment between special membranes 46, diffusing, crushing on the needles 56 and processing with neutral gas, which allows creating conditions for the radioactive waste particles to flow in the exhaust gas stream and removing these aerosols from the nozzle 58 for cleaning to block 5 .

 Part of the aerosol fractions then flows with the flow from the nozzle 60 and for the complete cleaning of this stream from radioactive waste use the apparatus 61 of the final decontamination received from the housing 1 of the liquid radioactive waste. In this apparatus, methods of fine-jet, fine-dispersed and diffuse treatment are set and used in conjunction with the cavitation mode of the treated solution / liquid-RAO /, and dissolved and suspended radioactive particles are separated from the electrolyte into gas phases in several successive stages / as described in FIG. 10 /: from chambers 71 and 64, chambers 77 and openings 80, 81 to bowl 84, after which the finally separated aerosol with radioactive waste is ionized by needles 87 and separated through openings 90 and 91 into chamber 92 for directing to the filters of unit 5. Most intensive separation RAO occurs when the bowl rotates on the shaft 82, when the gas phase is collected in its bed and ejected through tubes 85 through openings 90 and outlet openings 97 to the exhaust system 5.

 Example.

Case 1 is subjected to decontamination, containing RW waste in the form of residual / on its walls / plutonium, uranium, cesium, cerium, etc. / and induced activity of ⁵⁹ Fe and ⁶⁰ Co in the surface structure of the metal of the case. When exposed to the body, as shown above, its surface structure dissolves, and a high concentration of radioactive waste is contained in liquid radioactive waste, some of which are deposited on the volume electrode 16, the other part of the LRW is fed to the chamber 43 for separation into gas-liquid phases, and purified liquid up to the norms of MPC 10 ^-6 10 ^-7 Ci / kg goes further to the final fine tertiary treatment in the apparatus 61 and its working chambers, where LRW is cleaned to the norms of MPC 10 ^-8 Ci / kg, which allows free discharge of the purified liquid or use it in reverse water supply and, for example, to supply fresh water reactor; gases in the first case after chamber 43, and in the second case after leaving the pipe 97 contain aerosol radioactive waste, which are separated from the gas phase in block 5, for example, using Petryanov filters.

 At all these stages of cleaning: three stages from the direct impact on the walls of the housing 1 to the subsequent decontamination of dissolved radioactive substances, gases, carefully monitor the frequency of the process, observing the environmental standards of waste water and gas discharged after cleaning. Such control is carried out using instrumentation / devices not shown in the drawing, as trivial and mandatory support for such a process /.

 T. about. when implementing the method, a qualitatively new technical effect is achieved in terms of purity and culture of the process, which makes the process highly productive, autonomous and automatic at all stages.

 If necessary, the applicant submitted more complete data on the nature and technical and economic indicators of this method.

Claims (5)

 1. A method of deactivating nuclear power plants, including removing a layer of material from the structure of a decontaminated object having increased activity, packaging of radioactive waste and their subsequent placement in a repository, characterized in that the decontaminated object is placed in a sealed chamber, the cavity of this chamber and the cavity of the deactivated object are connected with a vacuum installation, the volume of the internal cavity of the deactivated object is reduced by introducing into it an elastic container, the outer surface of which you filled from an electrically conductive material, the object structure and the electrically conductive material are connected to different poles of the current source, the aggressive working agent is circulated between the walls of the deactivated object and the electrically conductive material of an elastic capacity, gas-filled bodies with destructible outer film are introduced into this agent and, as radioactive materials accumulate in the working agent part of the agent is allocated to waste separation, enrichment with flocculants and packaging in containers, restoring volume and concentration The centering of the agent circulating in the inner cavity by the introduction of its additional amount, the process is carried out until the set norms for MPC are obtained in the withdrawn agent, by which they judge the completion of the decontamination process.  2. The method according to claim 1, characterized in that an alternating electric potential is applied to the electrodes, an aggressive acid solution is used as the working agent, the circulating working agent is additionally subjected to acoustic impact, which decreases as the contaminated surface is cleaned, and after the decontamination of the contaminated object is completed an electrode made in the form of an elastic container is removed from the cavity of a deactivated object and subjected to deactivation.  3. The method according to p. 1, characterized in that the electrically conductive material of the elastic container is coated externally with a film having caverns.  4. A device for the decontamination of nuclear power plants containing a chamber for processing a contaminated object, an electrode, a line for supplying a working agent and removal of liquid and gas phases, characterized in that it is additionally equipped with a chamber for rough cleaning of the liquid phase and a camera for fine finishing of the liquid phase, connected in series with a processing chamber of a contaminated object, the electrode being made in the form of an elastic container, on the outer surface of which an electrically conductive material is applied, the electrode being made n with the possibility of placing it in the internal cavity of a decontaminated object, the rough phase liquid purification chamber is made in cross section and is equipped with membranes having cavities and holes, the outlet of this chamber is equipped with a separator in the form of a perforated plate with needles and a mustache, the separator has two nozzles for exhausting gas and liquid phases, while the branch pipe of the liquid phase is connected to the input of the fine finishing chamber having an intermediate, annular and central chamber, the central chamber has hollow spherical walls with the inlet and outlet openings and openings in the form of oblique cavities, the annular chamber has membranes with perforation and caverns, the outlet of the central chamber is connected to a bell communicated by means of a perforated cylinder and a perforated jumper with an aerosol collecting cavity, needles with an inclination to the flow are fixed in the bell on the strings, and on the axis of the central chamber in the bearings there is a shaft with a bowl at its end, made in the form of a mushroom-shaped swirler and a divider, the bed of the bowl is connected to the perforation through a mesh bottom and tubes th e bell cavity.  5. The device according to claim 4, characterized in that the membranes installed in the annular chamber have screw regulators for their tension.

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