JP2014142331A - Method and device for treating radioactive resin waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for appropriately treating radioactive resin waste.SOLUTION: Radioactive resin waste is thermally decomposed in a reaction vessel 11, and residues generated by the thermal decomposition are discharged to a powder reservoir 19. The residues are added with an additive containing phosphoric acid to be melted and solidified in a melting and solidification facility 30.

Description

  The technique disclosed in this specification relates to a technique for treating radioactive resin waste.

  In nuclear power plants and facilities that handle radioactive substances, system water is purified and water injected into the system is purified to prevent corrosion of the equipment. The radioactive resin waste used for such purification of water is classified according to the radioactivity level. Those with low radioactivity levels are incinerated, and those with high radioactivity levels are stored and stored in tanks with water. For this reason, it is preferable to dispose of radioactive resin waste having a high radioactivity level after mineralization and stabilization. Thus, a method has been proposed in which radioactive resin waste is thermally decomposed by dry distillation treatment or gasification treatment with superheated steam (for example, Patent Documents 1 and 2).

JP 63-171400 A JP 2012-116997 A

  Unlike the incineration process, the method of pyrolyzing radioactive resin waste by dry distillation or gasification can eliminate the need for refractories, and because it is processed at a lower temperature than the incineration process, cesium (Cs) Scattering can also be suppressed. However, when a radioactive waste is pyrolyzed, a residue is generated, and the residue needs to be stabilized. In order to stabilize the residue, it is preferable to melt and solidify, but the main component of the residue is high-melting iron oxide (attached when purifying water). For this reason, in order to melt | dissolve the residue after a thermal decomposition process, you have to process at high temperature and a melting process is difficult. This specification discloses the technique which can process a radioactive resin waste appropriately.

  The method for reducing the volume of radioactive resin waste disclosed in this specification includes a pyrolysis step for thermally decomposing radioactive resin waste, and phosphoric acid contained in a residue discharged by pyrolyzing the radioactive resin waste. A melt-solidifying step in which the additive to be added is melted and solidified.

  In the above treatment method, first, the radioactive resin waste is pyrolyzed, and an additive containing phosphoric acid is added to the residue generated by the pyrolysis treatment to melt and solidify. Since the melting point of the residue (containing iron oxide) is lowered by phosphoric acid, the residue can be melted and solidified at a lower temperature than when no additive is added to the residue. Thereby, a radioactive resin waste can be processed appropriately. Various methods can be used as a method for thermally decomposing radioactive waste. For example, a dry distillation process of heating in a nitrogen atmosphere, a process of thermal decomposition / gasification using water vapor, or the like can be used. When dry distillation treatment is used in the thermal decomposition step, the hydrogen component contained in the radioactive resin waste is gasified, so that the melting treatment can be suitably performed. On the other hand, if pyrolysis / gasification treatment using steam is used in the pyrolysis process, the hydrogen and carbon components contained in the radioactive resin waste are gasified, and the residue after treatment is reduced. Furthermore, it can carry out suitably.

  Moreover, this specification discloses the processing apparatus which can implement suitably said volume reduction processing method. That is, the processing apparatus disclosed in this specification is disposed below the thermal decomposition unit that thermally decomposes the radioactive resin waste, and melts the residue discharged by pyrolyzing the radioactive resin waste. It has a melt-solidified part that solidifies. And the residue discharged | emitted from a thermal decomposition part falls to the melt-solidification part by the dead weight.

  In this processing apparatus, the radioactive resin waste is put into the thermal decomposition unit and is thermally decomposed into a residue by the thermal decomposition unit. The residue after pyrolysis falls to the melt-solidified part by its own weight, and is melted and solidified in the melt-solidified part. For this reason, it is not necessary to provide the apparatus which conveys from a thermal decomposition part to a melt-solidification part, and a radioactive resin waste can be processed suitably. That is, the residue after pyrolysis has a higher radioactivity level than the radioactive resin waste before pyrolysis. For this reason, if the residue after pyrolysis is conveyed from the pyrolysis section to the melt-solidification section using equipment, the handling is difficult and maintenance of the equipment is also required. In this volume reduction processing apparatus, the residue after pyrolysis is charged into the melting and solidifying part by its own weight, so that the volume reduction processing apparatus can have a simple configuration.

  Details of the technology disclosed in this specification and further improvements will be described in detail in the detailed description and examples.

The whole block diagram of the volume reduction processing system which concerns on a present Example. The figure for demonstrating the ball-type reaction furnace which concerns on a present Example. Schematic of the high frequency melting apparatus which concerns on a present Example. The whole block diagram of the volume reduction processing apparatus which concerns on a modification.

  The main features of the embodiments described below are listed. The technical elements described below are independent technical elements and exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Absent.

(Characteristic 1) The processing method of the radioactive resin waste which this specification discloses contains phosphoric acid discharged | emitted by the electropolishing process which electropolishes a radioactive metal waste using the electrolyte solution containing a phosphoric acid solution. The waste liquid to be added may be added to the residue and melted and solidified. According to such a configuration, waste liquid (containing phosphoric acid) discharged by electropolishing for decontaminating the surface of the radioactive metal waste is added to the residue. Therefore, it is not necessary to prepare an additive only for lowering the melting point of the residue, and the residue can be efficiently melted.

(Characteristic 2) The radioactive resin waste processing apparatus disclosed in the present specification is disposed below the thermal decomposition unit and above the melt-solidifying unit, and can store residues discharged from the thermal decomposition unit You may further have a storage part. According to such a structure, the undecomposed part contained in the residue discharged | emitted from a thermal decomposition part can be further decomposed | disassembled in a residue storage part. For this reason, the undecomposed part contained in the residue thrown into a melt-solidification part can be decreased, and a melt-solidification process can be performed suitably.

(Characteristic 3) In the radioactive resin waste processing apparatus disclosed in this specification, the thermal decomposition unit may discharge the residue and exhaust gas discharged by thermally decomposing the radioactive resin waste to the residue storage unit. . In this case, the radioactive resin waste treatment apparatus is connected to the residue storage unit, and both the exhaust gas discharged from the thermal decomposition unit to the residue storage unit and the exhaust gas generated when the residue is melted and solidified in the melt-solidifying unit. You may have further the filter part which can be processed. According to such a configuration, the exhaust gas generated by thermally decomposing the radioactive resin waste and the exhaust gas generated by melting and solidifying the residue can be processed by one filter unit. For this reason, the exhaust gas treatment facility can have a simple configuration.

(Characteristic 4) The processing apparatus of the radioactive resin waste which this specification discloses may further have the switchgear arrange | positioned between the residue storage part and the melt-solidification part. The switchgear is configured such that the residue storage unit and the melt-solidification unit are in communication with each other and the residue and exhaust gas are allowed to move between each other, and the residue storage unit and the melt-solidification unit are in communication with each other. It may be possible to switch to the second state in which movement between the two is disabled. In this case, when the radioactive resin waste is thermally decomposed in the thermal decomposition unit, the melting and solidifying process by the melting and solidifying unit may be stopped and the switchgear may be set in the second state. Further, when the residue is melt-solidified in the melt-solidifying unit, the thermal decomposition process by the thermal decomposition unit is stopped, and the switchgear may be in the first state. According to such a configuration, the thermal decomposition treatment and the melt solidification treatment can be suitably performed while sharing the filter unit for the exhaust gas treatment.

(Characteristic 5) In the radioactive resin waste processing apparatus disclosed in this specification, a thermal decomposition section and a filter section may be disposed on the upper surface of the residue storage section. In this case, the lower end of the thermal decomposition unit and the lower end of the filter unit may be connected to the internal space of the residue storage unit. According to such a configuration, when the filter unit is back-washed, residues and foreign substances accompanying the part of the exhaust gas removed by the filter unit fall to the lower part of the residue storage part and are put into the melting and solidifying part from the lower part of the residue storage part. The Therefore, it is possible to reduce the volume and solidify the residue and foreign substances accompanying the part of the exhaust gas removed by the filter unit while confining the radioactive substance in the processing apparatus.

  Hereinafter, the volume reduction processing system according to the present embodiment will be described. The volume reduction processing system of the present embodiment is a system for volume reduction processing of used ion exchange resin (an example of radioactive resin waste) generated at a nuclear power plant. As shown in FIG. 1, the volume reduction processing system includes a resin receiving tank 1, a superheated steam supply device 4, a ball reactor 3, an exhaust gas processing device 5, a control device 2, and a solidification facility 30. Yes.

  The resin receiving tank 1 stores a used ion exchange resin generated at a nuclear power plant as a 5-15% slurry (resin 5-15%, moisture 85-95%). A supply pump 6 is connected to the resin supply port of the resin receiving tank 1. When the supply pump 6 operates, the slurry in the resin receiving tank 1 is supplied to the ball reactor 3 through the supply path.

  The superheated steam supply device 4 includes a water tank 7, a supply pump 8, a steam generator 9, and a steam superheater 10. A supply pump 8 is connected to the supply port of the water tank 7. When the supply pump 8 is activated, the water in the water tank 7 is supplied to the steam generator 9. The steam generator 9 uses water supplied from the water tank 7 as water vapor. A steam superheater 10 is connected to the steam generator 9, and water vapor generated by the steam generator 9 is supplied to the steam superheater 10. The steam superheater 10 superheats the steam supplied from the steam generator 9 to form superheated steam. The superheated steam generated by the steam superheater 10 is supplied to the ball reactor 3.

  The ball-type reactor 3 brings the ion-exchange resin slurry stored in the resin receiving tank 1 into contact with the superheated steam supplied from the superheated steam supply device 4 to thermally decompose the ion-exchange resin. . The gas generated by the thermal decomposition is sent to the exhaust gas treatment device 5, and the residue after the thermal decomposition of the ion exchange resin is sent to the solidification facility 30. Detailed configurations of the ball reactor 3 and the solidification facility 30 will be described later.

  The exhaust gas treatment device 5 treats the exhaust gas discharged from the ball type reactor 3, renders it harmless and exhausts it to the atmosphere. The exhaust gas treatment device 5 includes a secondary combustor that combusts combustible components in the exhaust gas supplied from the ball reactor 3, and a plurality of HEPA filters that remove particulates in the exhaust gas exhausted from the secondary combustor. have. By discharging the gas after passing through the HEPA filter to the atmosphere, the fine particles contained in the exhaust gas are prevented from diffusing into the atmosphere.

  The control device 2 is a control device that controls each device constituting the volume reduction processing system. For example, the controller 2 supplies the ion-exchange resin supplied to the ball reactor 3 (supply amount per hour) and the superheated steam supplied to the ball reactor 3 (supply per hour). Amount) and the atmospheric temperature in the ball reactor 3 are controlled. That is, the control device 2 controls the supply amount of the ion exchange resin by controlling the supply pump 6, and controls the supply amount of the superheated steam by controlling the superheated steam supply device 4. The ambient temperature is controlled by controlling the heater output.

  Next, a detailed configuration of the ball type reactor 3 will be described with reference to FIG. As shown in FIG. 2, the ball-type reaction furnace 3 includes a metal sealed reaction vessel 11 serving as a ball filling unit, and an external heater 14 (illustrated in FIG. 1) for heating the inside of the reaction vessel 11 from outside the vessel. The ceramic or metal ball 12 filled in the reaction vessel 11, the stirring blade 13 that can mechanically agitate the ball 12, and the ions that supply the ion exchange resin from above the reaction vessel 11 onto the ball 12 An exchange resin supply nozzle 16 and a superheated steam supply nozzle 15 for supplying superheated steam from the upper part of the reaction vessel 11 onto the balls 12 are configured.

  Note that whether or not superheated steam is supplied from the superheated steam supply nozzle 15 is arbitrary, and can be appropriately determined according to the moisture content of the ion exchange resin supplied from the ion exchange resin supply nozzle 16. For example, when the moisture content of the ion exchange resin is high, the supply of superheated steam from the superheated steam supply nozzle 15 may be stopped, whereas when the moisture content of the ion exchange resin is low, the superheated steam supply nozzle 15 Superheated steam may be supplied.

  The sealed reaction vessel 11 is composed of a metal cylinder, and includes a pressure control mechanism for controlling the pressure in the reaction vessel 11 and an external electric heater 14 for controlling the inside of the reaction vessel 11 to a desired temperature. I have. The length of the reaction vessel 11 can be appropriately determined according to the type of ion exchange resin to be processed. When the slurry of the ion exchange resin having a high moisture content is directly charged into the reaction vessel 11, it is preferable that the length of the reaction vessel 11 is set long because the temperature of the ion exchange resin is difficult to rise. By increasing the length of the reaction vessel 11, the reaction time can be made sufficiently long, and the charged ion exchange resin can be suitably thermally decomposed.

  A rotating shaft that is rotated at a low speed by a drive motor installed in the upper part of the reaction vessel 11 is provided at the axial center of the reaction vessel 11. A stirring blade 13, which is a spiral blade whose outer edge forms a space between the rotation axis and the outer edge, is attached to the periphery of the rotation shaft.

  The ball 12 in the reaction vessel 11 is a ceramic ball having corrosion resistance or a ball made of Hastelloy or Inconel which is a high nickel alloy. The ball 12 ascends the peripheral portion in the reaction vessel 11 while being stirred by the stirring blade 13, and the balls located at the upper portion in the reaction vessel 11 are sequentially lowered into the space formed accordingly. Go.

  A holding plate 23 for holding the ball 12 in the reaction vessel 11 is disposed at the lower end of the reaction vessel 11 (shown in FIG. 1). The holding plate 23 prohibits the passage of the ball 12 while allowing the passage of the gas and the ion exchange resin residue. As a result, the balls 12 filled in the reaction vessel 11 are prevented from falling into the powder reservoir 19, while the residue that has not been pyrolyzed in the reaction vessel 11 and the gas generated by the pyrolysis are powdered. The storage unit 19 can be moved.

  A temperature sensor 22 (shown in FIG. 1) is disposed at the approximate center of the lower surface of the holding plate 23. The temperature sensor 22 detects the temperature of the lower end of the reaction vessel 11 (that is, the lower end of the reaction unit). The temperature sensor 22 is connected to the control device 2. The temperature detected by the temperature sensor 22 is input to the control device 2.

  A powder reservoir 19 is provided below the reaction vessel 11. The powder storage unit 19 separates solid (powder such as ion exchange resin residue) from the gas discharged from the reaction vessel 11 and stores the separated powder. A superheated steam supply nozzle 21 is provided at the lower end of the powder storage unit 19. The superheated steam supply nozzle 21 is supplied with superheated steam from the superheated steam supply device 4. The superheated steam supplied from the superheated steam supply nozzle 21 into the powder reservoir 19 is used to decompose combustible components contained in the residue of the ion exchange resin. Further, a part of the superheated steam supplied into the powder reservoir 19 flows into the reaction vessel 11 and contacts the ion exchange resin in the reaction vessel 11 and is used for thermal decomposition of the ion exchange resin. The temperature of the superheated steam supplied from the superheated steam supply nozzle 21 is adjusted to 500 to 700 ° C, preferably 550 ° C or less. By setting the temperature of the superheated steam to 500 ° C. or higher, thermal decomposition of the ion exchange resin can be promoted. Further, by setting the temperature of the superheated steam to 700 ° C. or less, it is possible to improve the durability of the metal housing constituting the outer shell of the ball type reactor 3.

  An external electric heater 20 is provided on the wall surface of the powder storage unit 19. The heater 20 controls the atmosphere temperature in the powder reservoir 19 to a temperature at which the residue of the ion exchange resin can be thermally decomposed.

  A sintered metal filter 17 is disposed on the upper surface of the powder storage unit 19. The gas in the powder reservoir 19 is filtered by the sintered metal filter 17. The exhaust gas filtered by the sintered metal filter 17 is sent to the exhaust gas treatment device 5 from the exhaust gas outlet 18.

  Next, the solidification facility 30 will be described. In this embodiment, a high-frequency melting apparatus is used as the solidification facility 30. As shown in FIG. 3, the high-frequency melting apparatus 30 includes a furnace body 58, a lid body 64 attached to the upper end of the furnace body 58, and an elevating device 44 disposed below the furnace body 58. The furnace body 58 includes a furnace body 54, a cooling nozzle 42, and an induction heating coil 40 disposed along the outer peripheral surface of the furnace body 54. The furnace body 54 is formed in a cylindrical shape with an upper end and a lower end opened, and an accommodation space 56 is provided therein. In the accommodation space 56, the melting container 38 can be accommodated. A charging port 60 is provided at the upper end of the furnace body 54, and an opening 50 is provided at the lower end of the furnace body 54. The input port 60 and the opening 50 communicate with the accommodation space 56. The opening 50 is formed in a size that allows the melting container 38 to pass therethrough. The charging port 60 is formed to be smaller than the opening 50 and has a size that the melting container 38 cannot pass through. The cooling nozzle 42 is disposed in the lower part of the furnace body 54 so as to penetrate the outer wall of the furnace body 58 and the furnace body 54. A space is formed between the outer wall of the furnace body 58 and the furnace body 54. The induction heating coil 40 is held in the cavity by a holding arm (not shown). The induction heating coil 40 is disposed so as to cover the side surface of the melting vessel 38 through the furnace body 54. The induction heating coil 40 is connected to a high-frequency power source (50 to 3000 Hz) (not shown).

  The lid body 64 is attached to the upper end of the furnace body 58. When the lid body 64 is attached to the furnace body 58, the charging port 60 at the upper end of the furnace body 54 is closed. A charging machine 32 is installed on the lid 64. The charging machine 32 is disposed above the charging port 60 (that is, the accommodation space 56) of the furnace body 54. The charging machine 32 is loaded with a solid secondary waste (for example, a residue discharged from the ball-type reactor 3, phosphoric acid concentrated powder, etc.) to be melted. The input machine 32 inputs the secondary waste into the melting container 38 accommodated in the accommodation space 56. The lid 64 is provided with a nozzle 62. The nozzle 62 communicates with the accommodation space 56 of the furnace body 54. The nozzle 62 throws into the melting container 38 liquid secondary waste (for example, phosphoric acid-concentrated waste liquid discharged by an electric field polishing process, which will be described later) to be melted. The lid 64 is provided with an exhaust gas outlet 34. The exhaust gas outlet 34 communicates with the accommodation space 56 of the furnace body 54. The exhaust gas outlet 34 discharges gas generated during the melting process. The exhaust gas outlet 34 is connected to the exhaust gas treatment device 5 (specifically, a plurality of HEPA filters) shown in FIG. The exhaust gas discharged from the exhaust gas outlet 34 is rendered harmless by the exhaust gas treatment device 5 and discharged to the atmosphere. In addition, you may connect to a ceramic filter (illustration omitted), for example, before connecting to the waste gas processing apparatus 5 shown in FIG.

  The lifting device 44 includes a flat table 48 and a lifting mechanism (not shown) that lifts and lowers the flat table 48. The abutment 52 is placed on the flat table 48, and the melting container 38 is placed on the abutment 52. When the flat table 48 is raised to the upper end position (position indicated by the solid line in FIG. 3) by the lifting mechanism, the lower end of the accommodation space 56 is closed. When the plane table 48 is lowered to the lower end position (position indicated by the two-dot chain line in FIG. 3) by the lifting mechanism, the lower end of the accommodation space 56 is opened.

  The melting vessel 38 is a bottomed vessel and is made of a conductive ceramic containing carbon. When a high frequency power source is applied to the induction heating coil 40, an eddy current flows in the melting vessel 38, and the melting vessel 38 can be suitably heated. The temperature of the melting container 38 can be controlled by adjusting the electrical resistivity and thickness of the melting container 38. For example, the melting container 38 can be heated to 1200 [° C.].

  Next, a method for reducing the volume of the ion exchange resin by the volume reduction processing system according to the present embodiment will be described. In the present embodiment, first, the ion exchange resin is thermally decomposed by the ball type reactor 3, and the residue discharged from the ball type reactor 3 is melted and solidified by the high frequency melting device 30. First, the process of thermally decomposing the ion exchange resin in the ball reactor 3 will be described.

  First, the control device 2 drives the supply pump 6 to supply the ion-exchange resin slurry to the reaction vessel 11 of the ball-type reactor 3 and also drives the superheated steam supply device 4 to supply the superheated steam to the ball-type reactor 3. To the powder storage unit 19. At this time, the moisture content of the ion exchange resin supplied to the reaction vessel 11 per unit time and the moisture content of the superheated steam supplied to the powder storage unit 19 per unit time are determined depending on whether the ambient temperature in the ball reactor 3 is an ion. It adjusts so that it may be maintained suitably at the temperature required in order to thermally decompose an exchange resin. The superheated steam may be supplied onto the balls 12 from the upper part of the reaction vessel 11 by the superheated steam supply nozzle 15. Whether or not superheated steam is supplied from the superheated steam supply nozzle 15 depends on the amount of water in the superheated steam supplied to the powder storage unit 19 per unit time or the moisture in the ion exchange resin supplied from the ion exchange resin supply nozzle 16. It can be determined appropriately according to the rate.

  The ion exchange resin slurry supplied to the reaction vessel 11 is supplied from the ion exchange resin supply nozzle 16 into the reaction vessel 11. The ion exchange resin supplied into the reaction vessel 11 is initially in a water-containing state of 5 to 15% slurry, and basically adheres to the surface of the ball 13 and moves in the furnace. For this reason, the residence time of the ion exchange resin in the reaction vessel 11 is the same as the ball descent time. The ball descent time can be freely adjusted by the size of the stirring blade, the rotation speed, the ball size, and the height of the packed bed, but the ball descent time (that is, the residence time of the ion exchange resin in the reaction vessel 11). ) Is preferable for improving the weight loss rate. Specifically, a method of reducing the diameter of the ball, reducing the rotation speed of the rotating shaft, or increasing the length of the packed bed filled with the ball can be employed.

  The superheated steam supplied into the powder storage unit 19 is supplied from the superheated steam supply nozzle 21 into the powder storage unit 19. A part of the water vapor supplied into the powder reservoir 19 enters the reaction vessel 11 and is supplied to the ion exchange resin attached to the surface of the ball 13. The temperature of the superheated steam supplied into the powder storage unit 19 is set to 500 to 700 ° C., while the ion exchange resin supplied into the reaction vessel 11 is set to room temperature. For this reason, the upper layer part of reaction container 11 is lower than the temperature of the lower layer part of reaction container 11, and the temperature of the position of the lower end of reaction container 11 becomes the highest. Therefore, the temperature of the ion exchange resin charged into the reaction vessel 11 gradually increases as it moves from the upper layer portion to the lower layer portion.

  Therefore, the ion exchange resin charged into the reaction vessel 11 is divided into a first stage (around 100 ° C.) in which water contained in the ion exchange resin evaporates and a second stage (200 to 300 ° C.) in which ion exchange groups are separated. ) And the third stage (300 to 600 ° C.) in which carbonization of the substrate by dehydrogenation occurs. Here, since the ball 13 is agitated when the ball 13 having the ion exchange resin attached passes through the second stage (200 to 300 ° C.) where the ion exchange group is separated, the ion exchange resin and the superheated steam are efficient. Contact well. Thereby, the sulfonyl bridge | crosslinking of an ion exchange resin (more specifically, cation exchange resin) is suppressed, and the weight loss rate improvement of an ion exchange resin is attained.

  Further, in this embodiment, the control device 2 is configured so that the temperature of the ion exchange resin slurry supplied to the reaction vessel 11 is such that the temperature detected by the temperature sensor 22 is a predetermined temperature (for example, 460 to 700 ° C.). The amount, the amount of superheated steam supplied to the powder storage unit 19, and the outputs of the various heaters 14 and 20 are controlled. As a result, even when the ion exchange resin is charged into the reaction vessel 11 in a water content state of 5 to 15% slurry, the temperature at the lower end of the reaction vessel 11 is maintained at a sufficient temperature necessary for the decomposition of the ion exchange resin. The ion exchange resin can be sufficiently pyrolyzed in the container 11. Further, by controlling the temperature at the lower end of the reaction vessel 11 to be a predetermined temperature (for example, 460 to 700 ° C.), as a result, the supply amount of the ion exchange resin slurry into the reaction vessel 11 and the powder The amount of superheated steam supplied to the storage unit 19 is optimized. As a result, the ball-type reactor 3 is suppressed from increasing in size, and the exhaust gas treatment device 5 is suppressed from increasing in size.

  Residue (mainly iron oxide) generated by the decomposition in the reaction vessel 11 is discharged to the powder reservoir 19. Since it is difficult for the residue to accumulate in the reaction vessel 11, various problems associated with the residue processing in the reaction vessel 11 can be effectively avoided. In this embodiment, superheated steam is supplied to the lower part of the powder storage unit 19 and the powder storage unit 19 is heated by the heater 20. Thereby, the temperature of the powder storage unit 16 is controlled to 460 ° C. or higher, preferably 500 ° C. or higher, which is higher than the decomposition temperature of polystyrene. Therefore, the undecomposed portion in the residue discharged to the powder storage unit 19 is decomposed, and the weight reduction rate of the ion exchange resin can be further improved.

  Note that cracked gases (CO, CxHy), sulfuric acid gas, sulfurous acid gas, and the like generated by the decomposition in the reaction vessel 11 are discharged from the exhaust gas outlet 18 through the sintered metal filter 17 and processed by the exhaust gas processing device 5. The The sintered metal filter 17 can be a ceramic filter.

  Residue generated by the above-described thermal decomposition treatment of the ball-type reactor 3 is discharged from the powder storage unit 19. The residue discharged from the powder storage unit 19 is melted and solidified by the high-frequency melting device 30. In order to melt and solidify the residue, first, the elevating device 44 is driven to position the flat table 48 at the lower end position (position indicated by the two-dot chain line in FIG. 3). Next, the abutment 52 is placed on the flat table 48, and the melting container 38 is placed on the abutment 52. The melting vessel 38 is previously charged with phosphoric acid concentrated powder and residue. Next, the elevating device 44 is raised until the flat table 48 contacts the lower surface of the furnace body 58. As a result, the melting container 38 disposed on the abutment 52 is accommodated in the accommodating space 56 of the furnace body 54.

  Next, a high frequency power source is applied to the induction heating coil 40. As a result, an eddy current is generated in the melting container 38 and the melting container 38 generates heat. When the temperature of the melting container 38 rises, the secondary waste (that is, phosphoric acid concentrated powder and residue) charged in the melting container 38 is melted. When these secondary wastes are melted and reduced in volume, a space is formed above the melting container 38. Therefore, the charging machine 32 is driven, and secondary waste (that is, residues, phosphoric acid concentrated powder, etc.) is driven into the space. ). As a result, the melting container 38 is filled with the melt. The gas generated during the melting process is discharged from the exhaust gas outlet 34 and processed in the exhaust gas processing device 5. When the melting process is completed, the melting container 38 is unloaded from the high-frequency melting device 30. Next, the unloaded melting vessel 38 is moved to the cooling chamber 46, and the molten metal inside is cooled and solidified. The molten container 38 obtained by cooling and solidifying the molten metal is discarded in a predetermined storage facility. In the present embodiment, the melting container 38 is discarded, but the melting container 38 may be loaded into a predetermined container and then discarded. When a ceramic filter is connected between the exhaust gas outlet 34 and the exhaust gas treatment device 5, the gas discharged from the exhaust gas outlet 34 may pass through the ceramic filter and be processed in the exhaust gas treatment device 5. .

  Note that the charging machine 32 inputs the solid secondary waste into the high-frequency melting apparatus 30, but the type of secondary waste input into the high-frequency melting apparatus 30 is not limited to this. For example, instead of phosphoric acid concentrated powder, waste liquid discharged by electrolytic polishing treatment may be added. That is, in nuclear facilities such as nuclear power plants, metal waste is generated with the abolition, dismantling, and operation of facilities. When the radioactivity level of the metal waste exceeds the reference value, such decontamination processing is performed to decontaminate such radiometal waste and lower the radioactivity level. As a decontamination process of this radioactive metal waste, there is an electrolytic polishing process. In the electrolytic polishing treatment, an electrolytic solution containing a phosphoric acid solution is used, and the electrolytic solution after the electrolytic polishing treatment is treated as a waste liquid. Since this waste liquid contains phosphoric acid, this waste liquid can be put into the high-frequency melting apparatus 30 instead of the phosphoric acid concentrated powder. Specifically, it is introduced into the melting container 38 from the nozzle 62 of the high-frequency melting apparatus 30. When the waste liquid discharged by the electrolytic polishing treatment is used, it is not necessary to prepare an additive (that is, phosphoric acid concentrated powder) only for lowering the melting point of the residue, and the residue can be efficiently melted.

Here, an experiment in which a mixture obtained by mixing diphosphorus pentoxide (P ₂ O ₅ ) and iron oxide (Fe ₂ O ₃ : a residue generated by the thermal decomposition treatment of the ball-type reactor 3) was melt-processed will be briefly described. Keep it. In the experiment, diphosphorus pentoxide (P ₂ O ₅ ) and iron oxide (Fe ₂ O ₃ ) were mixed at a molar ratio of 4: 6, and the mixture was put into the high-frequency melting apparatus 30. In the melting container 38, 60 kg of the mixture was previously charged to start melting, and then 100 kg of the mixture was additionally charged. The rate at which the mixture was charged was 48 kg / h. The melting temperature of the mixture was 1200 ° C. Convection occurred in the molten metal in the melting vessel 38, and the molten state was also good.

  In the volume reduction processing system of the present embodiment, the ion exchange resin is thermally decomposed in the ball type reactor 3. Since the ion exchange resin is thermally decomposed at a relatively low temperature, scattering of cesium (Cs) is suppressed, and it is not necessary to use a refractory for the ball reactor 3 (that is, the durability of the ball reactor 3 is improved). Can be improved). The residue discharged from the ball reactor 3 is mixed with an additive (melting aid) containing phosphoric acid and melted. For this reason, melting | fusing point of a residue falls and it can melt and solidify at comparatively low temperature (for example, about 1200 degreeC). Thereby, cesium (Cs) can be confined in the molten solidified product while suppressing scattering of cesium (Cs). Further, since the residue can be melted and solidified at a low temperature, the possibility that the melting container 38 will break can be reduced. Furthermore, if the waste liquid discharged by electrolytic polishing is used as a melting aid to be added to the residue, it is not necessary to prepare a melting aid only for lowering the melting point of the residue, and the residue can be efficiently melted and solidified. Can do.

  As mentioned above, although one Example of the technique disclosed by this specification was described in detail, this is only an illustration and does not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

  For example, in the above-described embodiment, the ball-type reaction furnace 3 that thermally decomposes radioactive resin waste (ion exchange resin) and the high-frequency melting apparatus 30 that melts and solidifies the residue discharged from the ball-type reaction furnace 3 are separated. However, the technique disclosed in the present specification is not limited to such a form. For example, as shown in FIG. 4, a volume reduction processing apparatus 80 in which a ball-type reactor 3 and a high-frequency melting apparatus 68 (an example of a melting and solidifying unit) are integrated may be used. That is, the volume reduction device 80 includes a ball-type reaction furnace 3 that thermally decomposes radioactive resin waste, a high-frequency melting device 68 that is disposed below the ball-type reaction furnace 3, a ball-type reaction furnace 3, and a high-frequency melting device. 68 is provided.

  The ball-type reactor 3 has the same configuration as the ball-type reactor 3 of the above-described embodiment, and includes a sealed reaction vessel 11 (an example of a thermal decomposition unit) and a powder storage unit 19 (residue storage unit). And a sintered metal filter 17 (an example of a filter portion). The reaction vessel 11 and the sintered metal filter 17 are disposed on the upper surface of the powder reservoir 19. Since each structure of the reaction container 11, the powder storage part 19, and the sintered metal filter 17 is the same structure as the Example mentioned above, the detailed description is abbreviate | omitted.

  The high-frequency melting device 68 has the same configuration as the high-frequency melting device 30 of the above-described embodiment, but differs in that the charging machine 32 is not provided and the exhaust gas outlet 34 is not provided. That is, in the volume reduction processing device 80, the residue discharged from the ball type reactor 3 is put into the high frequency melting device 68 by its own weight. For this reason, the high frequency melting apparatus 68 is not equipped with the charging machine 32 for charging the residue. Further, as will be described later, the exhaust gas discharged from the high-frequency melting device 68 is processed by the sintered metal filter 17 through the powder reservoir 19. For this reason, the high-frequency melting device 68 is not provided with the exhaust gas outlet 34. The other points are the same as those of the above-described embodiment, and the high-frequency melting device 68 includes a furnace body 58, a lid 64, and a lifting device 44. Since each structure of the furnace main body 58, the cover body 64, and the raising / lowering apparatus 44 is the same structure as the Example mentioned above, the detailed description is abbreviate | omitted.

  The connection pipe 66 is disposed below the ball-type reactor 3 and above the high-frequency melting device 68. That is, the upper end of the connection pipe 66 is connected to the lower end of the ball-type reactor 3 (lower end of the powder storage unit 19). On the other hand, the lower end of the connection pipe 66 is connected to the upper end of the high-frequency melting device 68 (the opening 67 of the lid body 64). The connecting pipe 66 communicates the internal space of the powder storage unit 19 and the accommodation space 56 of the high-frequency melting device 68. The connection pipe 66 includes a damper (an example of an opening / closing device) not shown. The damper opens and closes the connecting pipe 66 to switch between a state in which the internal space of the powder storage unit 19 and the accommodation space 56 of the high-frequency melting device 68 communicate with each other and a state in which these spaces do not communicate with each other. The opening / closing operation of the damper is controlled by a control device (not shown).

  Next, a procedure for volume reduction processing of radioactive resin waste by the volume reduction processing apparatus 80 will be described. In order to reduce the volume of radioactive resin waste, first, the damper is driven to close the connecting pipe 66, and the radioactive resin waste is pyrolyzed (dry-distilled) by the ball reactor 3. That is, radioactive resin waste is supplied to the reaction vessel 11 of the ball-type reaction furnace 3 and superheated steam is supplied to the ball-type reaction furnace 3. Thereby, the radioactive resin waste supplied to the reaction vessel 11 is thermally decomposed. Residue and exhaust gas generated when the radioactive resin waste is thermally decomposed in the reaction vessel 11 is discharged to the powder reservoir 19. The powder reservoir 19 separates solids (powder such as radioactive resin waste residue) from the exhaust gas discharged from the reaction vessel 11. Since the connecting pipe 66 is closed by the damper, the solid (residue) separated from the exhaust gas is stored in the lower part of the powder storage unit 19. Since superheated steam is supplied to the lower part of the powder storage part 19, the undecomposed part in the residue stored in the lower part of the powder storage part 19 is further decomposed. On the other hand, the exhaust gas discharged from the reaction vessel 11 to the powder storage unit 19 is discharged from the exhaust gas outlet 18 through the sintered metal filter 17 and processed by the exhaust gas treatment device 5.

  Note that, as described above, when the radioactive resin waste is thermally decomposed in the ball-type reaction furnace 3, the connecting pipe 66 is closed by the damper. For this reason, the melt solidification process by the high frequency melting apparatus 68 is not performed. Further, solids (such as radioactive resin waste residue) adhering to the surface of the sintered metal filter 17 fall into the powder storage unit 19 by backwashing the sintered metal filter 17, and the powder storage unit 19. It is stored in the lower part of.

When the residue is stored in the powder storage unit 19 by thermally decomposing the radioactive resin waste, the residue stored in the powder storage unit 19 is then melted and solidified. For this purpose, first, the supply of the radioactive resin waste and superheated steam to the ball-type reaction furnace 3 is stopped, and the thermal decomposition treatment of the radioactive resin waste by the ball-type reaction furnace 3 is stopped. Next, in a state where the melting container 38 is set in the accommodation space 56 of the high frequency melting device 68, the damper is driven to open the connection pipe 66. As a result, the residue stored in the powder storage unit 19 falls due to its own weight. That is, the residue stored in the powder storage unit 19 is introduced into the melting container 38 set in the high-frequency melting device 68 through the connection pipe 66. Note that an additive (for example, phosphoric acid concentrated powder (diphosphorus pentoxide (P ₂ O ₅ )) or the like can be charged in the melting container 38 in advance. This makes it possible to add additives to the residue to be melted.

  Next, a high frequency power source is applied to the induction heating coil 40 to generate an eddy current in the melting vessel 38 and heat the melting vessel 38. As a result, the residue and additive introduced into the melting container 38 are melted. When the melting process is completed, the melting container 38 is unloaded from the high-frequency melting device 30. The gas generated during the melting process is processed by the sintered metal filter 17 through the connection pipe 66 and the powder reservoir 19. The exhaust gas processed by the sintered metal filter 17 is discharged from the exhaust gas outlet 18 and further processed by the exhaust gas processing device 5.

  Hereinafter, the volume reduction process of the radioactive resin waste is performed by alternately repeating the thermal decomposition process by the ball reactor 3 and the melting process by the high-frequency melting apparatus 30.

  In the volume reduction processing apparatus 80 described above, the residue discharged by thermal decomposition in the ball-type reactor 3 is stored in the powder storage unit 19 and then put into the melting container 38 in the high-frequency melting apparatus 68 by its own weight. Is done. For this reason, it is not necessary to provide equipment for conveying the residue from the ball-type reactor 3 to the high-frequency melting device 68, and the residue can be charged into the melting vessel 38 with a very simple configuration. Residues generated from the radioactive resin waste (having a high radioactivity level) are subjected to the melting process in a state of being confined in the volume reduction processing apparatus 80. For this reason, scattering of radioactive substances (cesium etc.) can be prevented effectively.

  Further, the residue put into the high-frequency melting device 68 is decomposed while being stored in the powder storage unit 19, and the undecomposed content in the residue is extremely small. For this reason, the amount of exhaust gas generated during the melting process can be reduced. As a result, the exhaust gas generated during the melting process can be processed by the sintered metal filter 17 that processes the exhaust gas generated during the thermal decomposition. Since the sintered metal filter 17 can be shared, the configuration of the volume reduction processing device 80 can be simplified.

  In the volume reduction processing device 80 described above, instead of previously adding an additive such as phosphoric acid concentrated powder into the melting vessel 38, the electrolytic solution (waste liquid) after the electrolytic polishing treatment is supplied from the nozzle 62. You may make it supply. Further, the residue may be melted and solidified without adding an additive containing phosphoric acid.

  Moreover, in each Example mentioned above, radioactive resin waste (ion exchange resin etc.) was thermally decomposed using the ball-type reaction furnace, However, The thing of various types of thermal decomposition apparatuses can be used. For example, a screw feeder type thermal decomposition apparatus may be used, and radioactive resin waste (ion exchange resin) may be supplied to one end of the screw feeder, and decomposition gas and residue may be discharged from the other end of the screw feeder. Moreover, in the Example mentioned above, although the radioactive resin waste (ion exchange resin) was gasified with superheated steam, the radioactive resin waste (ion exchange resin) may be dry-distilled in a nitrogen atmosphere.

  Moreover, although the example which processes an ion exchange resin was demonstrated in the Example mentioned above, the technique disclosed by this specification is volume reduction of other radioactive resin wastes (For example, filter sludge, a filter aid, etc.). Can be used for processing.

  The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

DESCRIPTION OF SYMBOLS 1 Resin receiving tank 2 Control apparatus 3 Ball-type reactor 4 Superheated steam supply apparatus 5 Exhaust gas treatment means 6 Supply pump 7 Water tank 8 Supply pump 9 Steam generator 10 Steam superheater 11 Sealed reaction vessel 14 External electric heater 12 Ball 13 Stirring blade 16 Ion exchange resin supply nozzle 15 Superheated steam supply nozzle 17 Sintered metal filter 18 Exhaust gas outlet 19 Powder storage part 20 External electric heater 21 Superheated steam nozzle 22 Temperature sensor 23 Holding plate 30 High frequency melting apparatus

Claims (7)

It is a method to reduce the volume of radioactive resin waste,
A pyrolysis step of pyrolyzing the radioactive resin waste;
And a melting and solidifying step of adding an additive containing phosphoric acid to a residue discharged by thermally decomposing the radioactive resin waste and melting and solidifying the radioactive resin waste.   In the melting and solidifying step, a waste liquid containing phosphoric acid discharged by electropolishing radioactive metal waste using an electrolytic solution containing a phosphoric acid solution is added to the residue and melted and solidified. The method for processing radioactive resin waste according to 1. It is a device that reduces the volume of radioactive resin waste,
A pyrolysis section for pyrolyzing the radioactive resin waste;
A melting and solidifying part that is disposed below the pyrolyzing part and melts and solidifies by adding an additive containing phosphoric acid to a residue discharged by pyrolyzing the radioactive resin waste. ,
The radioactive resin waste processing apparatus according to claim 1, wherein the residue discharged from the thermal decomposition unit falls into the melting and solidifying unit by its own weight.   4. The apparatus according to claim 3, further comprising a residue storage unit that is disposed below the thermal decomposition unit and above the melt-solidifying unit and capable of storing a residue discharged from the thermal decomposition unit. The processing apparatus of the radioactive resin waste described in 2. The thermal decomposition unit discharges residue and exhaust gas discharged by pyrolyzing the radioactive resin waste to the residue storage unit,
A filter unit connected to the residue storage unit and capable of processing both the exhaust gas discharged from the thermal decomposition unit to the residue storage unit and the exhaust gas generated when the residue is melted and solidified in the melt solidification unit is further provided. The processing apparatus of the radioactive resin waste of Claim 4 which is carrying out. It further has a switchgear disposed between the residue storage part and the melt-solidification part,
The switchgear includes a first state in which the residue storage unit and the melt-solidification unit are in communication with each other and movement between the residue and the exhaust gas, and the residue storage unit and the melt-solidification unit are in a non-communication state. It is possible to switch to the second state in which movement between both the residue and the exhaust gas is impossible,
When pyrolyzing the radioactive resin waste in the thermal decomposition unit, the melt-solidification process by the melt-solidification unit is stopped, and the switchgear is in the second state,
6. The radioactive resin waste according to claim 5, wherein when the residue is melt-solidified in the melt-solidification unit, the thermal decomposition process by the thermal decomposition unit is stopped and the switchgear is brought into the first state. Processing equipment. On the upper surface of the residue storage part, the thermal decomposition part and the filter part are arranged,
The radioactive resin waste processing apparatus of Claim 5 or 6 with which the lower end of the said thermal decomposition part and the lower end of the said filter part are connected with the internal space of the said residue storage part.

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