Radioactive waste treatment containers and methods

Abstract

To provide a radioactive waste processing container and a method for processing a radioactive waste which can improve the efficiency of a drying work of a radioactive waste.SOLUTION: The present invention includes: a cylindrical container body having an upper opening part and a closed lower part; a cylindrical member which forms a porous cylindrical shape and is arranged in the inside of the container body; a lid removably provided in the upper opening part of the container body; and a gas exit part for discharging gas inside the container body to the outside.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a processing container and method for radioactive waste.

Background Art

[0002] In a nuclear power plant, when core fuel disposed inside a reactor pressure vessel melts, structures inside the reactor containment vessel also melt and solidify, becoming debris as radioactive waste. Therefore, it is necessary to recover and process radioactive waste such as debris from the reactor containment vessel. As a technique for processing radioactive waste, for example, there is one described in Patent Document 1. The technique described in Patent Document 1 is to store radioactive waste in a canister, and heat the canister with a heater disposed outside the canister, thereby drying the radioactive waste inside.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] When radioactive waste is stored in a canister and the canister is heated from the outside to dry the radioactive waste inside, the heat of the heater is less likely to be transmitted to the radioactive waste inside the canister, and there is a problem that the drying operation takes a long time. In particular, when a large amount of moisture is entrained in the radioactive waste, the drying operation becomes even longer. In addition, radioactive waste containing moisture solidifies as a result of drying, and cracks occur due to the solidification. Then, the evaporated gas generated by drying the radioactive waste rises through the cracked portions. Then, there is a concern that the flow velocity of the evaporated gas rising through the cracked portions increases, causing the radioactive waste to scatter.

[0005] This disclosure aims to solve the aforementioned problems and to provide a radioactive waste processing container and method that improves the efficiency of drying radioactive waste. [Means for solving the problem]

[0006] To achieve the above objectives, the radioactive waste processing container of this disclosure comprises a container body having an upper opening and a closed lower end, a cylindrical member having a porous cylindrical shape and disposed inside the container body, a lid detachably provided on the upper opening of the container body, and a gas outlet for discharging gas from inside the container body to the outside.

[0007] Furthermore, the radioactive waste treatment method of the present disclosure is a method for treating radioactive waste using a treatment container in which a cylindrical member having a porous cylindrical shape is arranged inside a container body whose lower part is closed, and the upper opening of the container body can be opened and closed by a lid, comprising the steps of: placing radioactive waste inside the container body through the upper opening; closing the upper opening of the container body with the lid; drying the radioactive waste placed inside the inner cylinder; and discharging the gas from the container body to the outside through the cylindrical member. [Effects of the Invention]

[0008] The radioactive waste treatment container and method described herein can improve the efficiency of drying radioactive waste. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram representing the radioactive waste processing container of this embodiment. [Figure 2] Figure 2 is a horizontal cross-sectional view showing a radioactive waste processing container. [Figure 3] Figure 3 is an exploded view of a radioactive waste processing container. [Figure 4] Figure 4 is a flowchart illustrating the radioactive waste processing method according to this embodiment. [Figure 5]Figure 5 is a schematic diagram illustrating the drying process in the processing container. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. However, these embodiments do not limit the present disclosure, and where there are multiple embodiments, they may be combinations of these embodiments. Furthermore, the components in the embodiments include those readily conceivable by those skilled in the art, those that are substantially identical, and those that are equivalent.

[0011] <Containers for processing radioactive waste> Figure 1 is a schematic diagram representing the radioactive waste treatment container of this embodiment, Figure 2 is a horizontal cross-sectional view representing the radioactive waste treatment container, and Figure 3 is an exploded view representing the radioactive waste treatment container.

[0012] In nuclear power plants, when the reactor core and other components inside the reactor vessel melt, molten material such as molten fuel is generated, and this solidified molten material (debris) is subject to recovery as radioactive waste. The radioactive waste processing container and method of this embodiment, for example, recovers and stores radioactive waste generated at a nuclear power plant and dries it. However, the radioactive waste is not limited to debris, but may also include spent fuel or structures generated during decommissioning.

[0013] As shown in Figures 1 to 3, the radioactive waste processing container 10 comprises an outer cylinder 11, an inner cylinder 12, a cylindrical member 13, and a lid 14. The processing container body is composed of the outer cylinder 11 and the inner cylinder 12.

[0014] The outer cylinder 11 is cylindrical in shape, with an open top and a closed bottom. The outer cylinder 11 has an outer cylinder body 21, a bottom 22, an upper opening 23, and a flange portion 24. The outer cylinder body 21 is cylindrical, but may also be rectangular in shape. The bottom 22 is disc-shaped according to the shape of the outer cylinder body 21 and is integrally provided at the lower part of the outer cylinder body 21. The upper opening 23 is provided at the upper end of the outer cylinder body 21 and allows fluid to flow between the inside and outside of the outer cylinder body 21. The flange portion 24 is ring-shaped and is integrally provided on the outside of the upper end of the outer cylinder body 21.

[0015] The inner cylinder 12 is cylindrical in shape, with an open top and a closed bottom. The inner cylinder 12 has an inner cylinder body 31, a bottom 32, and an upper opening 33. The inner cylinder body 31 is cylindrical, but may also be rectangular. The bottom 32 is disc-shaped according to the shape of the inner cylinder body 31 and is integrally provided at the lower part of the inner cylinder body 31. The upper opening 33 is provided at the upper end of the inner cylinder body 31 and allows fluid to flow between the inside and outside of the inner cylinder body 31. That is, the inside of the outer cylinder 11 and the inside of the inner cylinder 12 are in communication on the upper side.

[0016] The cylindrical member 13 has a porous cylindrical shape with an open top and bottom. Specifically, the cylindrical member 13 has a cylindrical shape made of mesh (wire mesh). The cylindrical member 13 is not limited to a cylindrical shape, but may also be a rectangular cylinder. Multiple cylindrical members 13 are arranged inside the inner cylinder 12. In this embodiment, multiple cylindrical members 13 (five in this embodiment) are arranged inside the inner cylinder 12 at intervals around the center and the periphery of the center. However, the position and number of cylindrical members 13 are not limited, and one or multiple cylindrical members may be provided at intervals. The holes in the mesh of the cylindrical member 13 are set according to the type and size of radioactive waste contained inside the inner cylinder 12. That is, it is preferable that the mesh is large enough so that the radioactive waste contained inside the inner cylinder 12 cannot pass through. The cylindrical member 13 may also be made of perforated metal.

[0017] In the present embodiment, the tubular members 13 are provided integrally with the inner cylinder 12. That is, a plurality of the tubular members 13 are erected on the bottom portion 32 inside the inner cylinder main body 31. In this case, the vertical length of the tubular member 13 is shorter than the vertical length of the inner cylinder main body 31, and the lower end portion thereof is integrally connected to the bottom portion 32. In this case, the lower end portion of the tubular member 13 is closed by the bottom portion 32. However, the tubular members 13 may be provided separately from the inner cylinder 12, and the vertical length thereof may be equal to or longer than the vertical length of the inner cylinder 12.

[0018] The inner diameter of the outer cylinder 11 is larger than the outer diameter of the inner cylinder 12. The total length (axial length) of the outer cylinder 11 is longer than the total length (axial length) of the inner cylinder 12. The inner cylinder 12 is disposed inside the outer cylinder 11. In this case, the outer cylinder 11 and the inner cylinder 12 are arranged such that their centers coincide with each other. The outer cylinder 11 and the inner cylinder 12 are arranged such that the bottom portions 22 and 32 overlap each other vertically, and are connected by welding or the like, whereby the inner cylinder 12 is positioned and supported inside the outer cylinder 11.

[0019] In the processing vessel 10, a first gas flow path 41 is provided between the inner peripheral surface of the outer cylinder main body 21 in the outer cylinder 11 and the outer peripheral surface of the inner cylinder main body 31 in the inner cylinder 12. The first gas flow path 41 has a cylindrical shape. Further, in the processing vessel 10, a second gas flow path 42 is provided inside each of the tubular members 13. The second gas flow path 42 has a cylindrical shape.

[0020] The lid 14 has a disc shape. The outer diameter of the lid 14 is substantially the same as the outer diameter of the flange portion 24 of the inner cylinder 12. The lid 14 is disposed on the upper part of the outer cylinder 11, and is fixed to the outer cylinder 11 by a plurality of bolts 15. The lid 14 is fixed to the upper part of the outer cylinder 11 to close the upper opening 23 of the outer cylinder 11. The lid 14 is detachable from the outer cylinder 11 by the plurality of bolts 15.

[0021] The lid 14 is provided with a first communication portion 51 penetrating in the thickness direction. The first communication portion 51 is disposed at the outer peripheral portion of the lid 14. The first communication portion 51 communicates with the upper part of the first gas flow path 41 between the outer cylinder 11 and the inner cylinder 12. In the present embodiment, a plurality of the first communication portions 51 are provided, but the number of the first communication portions 51 is not limited to a plurality, and may be one. Further, the outer cylinder 11 is provided with a second communication portion 52 penetrating the bottom portion 22 in the thickness direction. The second communication portion 52 is disposed at the outer peripheral portion of the bottom portion 22 of the outer cylinder 11. The second communication portion 52 communicates with the lower part of the first gas flow path 41 between the outer cylinder 11 and the inner cylinder 12. In the present embodiment, a plurality of the second communication portions 52 are provided, but the number of the second communication portions 52 is not limited to a plurality, and may be one.

[0022] Although not shown, the lid 14 has a coupler corresponding to the first communication portion 51 mounted on the upper part thereof, and the outer cylinder 11 has a coupler corresponding to the second communication portion 52 mounted on the bottom portion 22. Each of the couplers is a pipe connection coupler. That is, the coupler has a valve provided therein, and the valve is biased and supported in a direction to close the passage by the biasing force of a spring. Then, the valve is opened by connecting the plug of a pipe to the coupler.

[0023] In the present embodiment, the second communication portion 52 communicates with the first gas flow path 41 and functions as a gas inlet portion for supplying a drying gas from the outside to the first gas flow path 41. On the other hand, the first communication portion 51 communicates with the first gas flow path 41 and the second gas flow path 42, and functions as a gas outlet portion for discharging the gas in the first gas flow path 41 and the second gas flow path 42 to the outside.

[0024] The outer cylinder 11 is provided with a heating device 61 on the outer peripheral portion. The heating device 61 is, for example, an electric heater. The heating device 61 has a cylindrical shape and is fixed in close contact with the outer peripheral surface of the outer cylinder 11.

[0025] The inner cylinder 12 is inserted into the outer cylinder 12 and positioned and fixed. At this time, a plurality of cylindrical members 13 are arranged inside the inner cylinder 12. The heating device 61 is disposed and fixed on the outer side of the outer cylinder 11. The lid 14 is detachable from the outer cylinder 11.

[0026] <Methods for disposing of radioactive waste> Figure 4 is a flowchart illustrating the radioactive waste processing method of this embodiment, and Figure 5 is a schematic diagram illustrating the drying process in the processing container.

[0027] As shown in Figures 4 and 5, the radioactive waste processing method of the first embodiment is a method for processing radioactive waste using the processing container 10 described above, and involves drying and storing the radioactive waste. Furthermore, in the radioactive waste processing method of this embodiment, various processing operations are performed remotely by an operator using a manipulator (not shown).

[0028] In step S11, the radioactive waste 100 is placed in the processing container 10. In this case, the processing container 10 has its lid 14 removed, and the radioactive waste 100 is placed inside the inner cylinder 12 through the open upper opening 33. In step S12, the lid 14 is attached to the processing container 10 to close the upper opening 33, and the radioactive waste 100 is sealed inside the processing container 10.

[0029] In step S13, various pipes constituting the drying apparatus are connected to the lid 14 of the processing container 10. Specifically, the gas supply pipe 71 has a heating device 72 at its base end and branches into multiple pipes at its tip, with plugs connected to the ends of each branch pipe. The gas discharge pipe 73 has a filter 74 and a blower 75, and a plug is connected to its base end. The operator remotely operates the manipulator to connect the gas supply pipe 71 to the second communication section 52 and the gas discharge pipe 73 to the first communication section 51.

[0030] In step S14, the drying process of the radioactive waste 100 is started. Specifically, the blower 75 is activated to apply negative pressure to the first gas passage 41 between the outer cylinder 11 and the inner cylinder 12 through the first communication section 51 from the gas discharge pipe 73. The negative pressure in the first gas passage 41 acts on the gas supply pipe 71 via the second communication section 52.

[0031] Then, the drying gas (heated air) heated by the heating device 72 is drawn into the first gas flow path 41 through the gas supply pipe 71 and the second communication section 52, and rises up the first gas flow path 41, heating the radioactive waste 100 contained inside the inner cylinder 12 via the inner cylinder 12. As a result, the radioactive waste 100 inside the inner cylinder 12 is heated from the lower end side and from the outer circumference side, causing the moisture adhering to or contained in the radioactive waste 100 to evaporate and dry out. In addition, the heating device 61 heats the radioactive waste 100 contained inside the inner cylinder 12 using radiant heat. Note that the drying gas is not limited to heated air, but may also be dry air with a low moisture content or an inert gas (such as nitrogen).

[0032] At this time, as the radioactive waste 100 solidifies due to the evaporation of moisture, cracks form, and the evaporated gas generated from the evaporation of moisture from the radioactive waste 100 moves upward through the cracks. The evaporated gas also moves inside the inner cylinder 12 toward the cylindrical member 13, and moves through the mesh-like cylindrical member 13 to the second gas flow path 42. Multiple cylindrical members 13 that form the second gas flow path 42 are arranged inside the inner cylinder 12. Therefore, the evaporated gas generated from the radioactive waste 100 rises inside the inner cylinder 12 through multiple second gas flow paths 42 (cylindrical members 13). In other words, the evaporated gas rises not only through the cracks in the solidified radioactive waste 100, but also through multiple second gas flow paths 42. As a result, the flow velocity of the evaporated gas rising inside the inner cylinder 12 is reduced, and the scattering of the dried radioactive waste 100 is suppressed.

[0033] The drying gas that rises through the first gas passage 41 is then discharged from the first connecting section 51 to the gas discharge pipe 73. The evaporated gas that rises through the second gas passage 42 of the cylindrical member 13 is discharged upward from the upper opening 33 of the inner cylinder 12 and then discharged from the first connecting section 51 to the gas discharge pipe 73. At this time, the filter 74 adsorbs and removes harmful substances contained in the air and gas.

[0034] In step S15, it is determined whether a predetermined processing time has elapsed since the start of the drying process. If it is determined that the predetermined processing time has not elapsed since the start of the drying process (No), the drying process continues. On the other hand, if it is determined that the predetermined processing time has elapsed since the start of the drying process (Yes), the drying process is terminated. That is, the operation of the blower 75 is stopped, and the gas supply pipe 71 and gas discharge pipe 73 are removed from the lid 14. Then, in step S17, the lid 14 of the processing container 10 is replaced with a storage lid (not shown), and the radioactive waste 100 is stored in the processing container 10.

[0035] [Effects of this embodiment] The radioactive waste processing container according to the first embodiment comprises a cylindrical container body (outer cylinder 11 and inner cylinder 12) having upper openings 23, 33 and closed at the bottom, a cylindrical member 13 having a porous cylindrical shape and being disposed inside the container body, a lid 14 that is detachably provided on the upper opening 23 of the container body, and a first communication part (gas outlet part) 51 for discharging gas from inside the container body to the outside.

[0036] In the first embodiment of the radioactive waste processing container, a second gas channel 42 is formed by arranging a cylindrical member 13 with a porous cylindrical shape inside the container body. When the radioactive waste 100 contained inside the container body is heated, the generated evaporated gas rises through the second gas channel 42 and is discharged to the outside from the first communication section 51. At this time, the evaporated gas rises not only inside the radioactive waste 100 but also through the second gas channel 42, and the increased upward path of the evaporated gas allows for earlier discharge of the evaporated gas. As a result, the radioactive waste 100 can be dried efficiently, and the efficiency of the drying work on the radioactive waste 100 can be improved. In addition, by increasing the upward path of the evaporated gas, the flow velocity of the evaporated gas is reduced, and the scattering of the dried radioactive waste 100 can be suppressed.

[0037] The radioactive waste processing container according to the second embodiment is the same as the radioactive waste processing container according to the first embodiment, and further, the first communication section (gas outlet section) 51 is provided on the lid 14. This allows the evaporated gas generated by heating the radioactive waste to be properly discharged to the outside from the first communication section 51.

[0038] The radioactive waste processing container according to the third embodiment is a radioactive waste processing container according to the first or second embodiment, further comprising, as the container body, an outer cylinder 11 having an upper opening 23 and a closed lower end, an inner cylinder 12 having an upper opening 33 and a closed lower end, and positioned inside the outer cylinder 11 to form a first gas flow path 41 between itself and the outer cylinder 11, and a second communication section (gas inlet section) 52 for supplying drying gas to the first gas flow path 41. By supplying drying gas from the second communication section 52 to the first gas flow path 41 and discharging it from the first communication section 51, the radioactive waste 100 contained inside the inner cylinder 12 can be efficiently dried.

[0039] The radioactive waste processing container according to the fourth embodiment is a radioactive waste processing container according to the third embodiment, wherein the cylindrical member 13 is arranged inside the inner cylinder 12 and a second gas flow path 42 is formed inside it, and the first gas flow path 41 and the second gas flow path 42 communicate with a first communication section (gas outlet section) 51. This allows the drying gas supplied to the first gas flow path 41 and the evaporated gas rising in the second gas flow path 42 to be appropriately discharged to the outside from the first communication section 51.

[0040] The radioactive waste processing container according to the fifth embodiment is a radioactive waste processing container according to the third or fourth embodiment, further comprising a second communication section (gas inlet section) 52 provided at the bottom 22 of the outer cylinder 11, which allows for efficient drying of the radioactive waste 100 by appropriately flowing drying gas into a first gas flow path provided on the outside of the inner cylinder 12.

[0041] The radioactive waste processing container according to the sixth embodiment is a radioactive waste processing container according to any one of the third to fifth embodiments, further comprising an inner cylinder 12 having a cylindrical inner cylinder body 31 and a bottom portion 32 provided at the lower part of the inner cylinder body 31, and a cylindrical member 13 integrally provided on the bottom portion 32. This allows the inner cylinder 12 and the cylindrical member 13 to be provided integrally, simplifying assembly to the outer cylinder 11.

[0042] The radioactive waste processing container according to the seventh embodiment is a radioactive waste processing container according to any one of the first to sixth embodiments, and furthermore, a heating device 61 is arranged on the outer surface of the outer cylinder 11. This makes it possible to effectively heat the radioactive waste 100.

[0043] The eighth aspect of the method for processing radioactive waste includes the steps of: placing radioactive waste 100 inside the container through the upper opening 23 of the container body; closing the upper opening 23 of the container body with a lid 14; drying the radioactive waste 100 contained inside the inner cylinder 12; and discharging the gas from the container body to the outside using a cylindrical member 13.

[0044] According to the radioactive waste treatment method of the eighth embodiment, a second gas channel 42 is formed by the cylindrical member 13, so that evaporated gas generated from the radioactive waste 100 rises through the second gas channel 42 and is discharged. At this time, the evaporated gas rises not only inside the radioactive waste 100 but also through the second gas channel 42, and the increased upward path of the evaporated gas allows for earlier discharge of the evaporated gas. As a result, the radioactive waste 100 can be dried efficiently, and the efficiency of the drying work on the radioactive waste 100 can be improved. In addition, by increasing the upward path of the evaporated gas, the flow velocity of the evaporated gas is reduced, and the scattering of the dried radioactive waste 100 can be suppressed. [Explanation of Symbols]

[0045] 10. Containers for processing radioactive waste 11. Outer cylinder (container body) 12. Inner cylinder (container body) 13. Cylindrical member 14 Lid 15 volts 21 Outer cylinder body 22 Bottom 23 Upper opening 24 Flange section 31 Inner cylinder body 32 Bottom 33 Upper opening 41 First gas channel 42 Second gas channel 51. First connecting section (gas outlet section) 52 Second connecting section (gas inlet section) 61 Heating device 71 Gas supply piping 72 Heating device 73 Gas exhaust piping 74 filters 75 Blower 100 Radioactive waste

Claims

1. A container body having an opening at the top and a closed bottom, forming a cylindrical shape, A cylindrical member having a porous cylindrical shape and positioned inside the container body, thereby forming a space for containing radioactive waste between itself and the container body, and a second gas flow path formed inside, A lid is detachably provided on the upper opening of the container body, The container body includes a gas outlet for discharging gas from inside to the outside, A radioactive waste processing container equipped with [a specific feature / feature].

2. The gas outlet portion is provided in the lid, A radioactive waste treatment container according to claim 1.

3. The container body comprises an outer cylinder having an upper opening and a closed lower end, an inner cylinder having an upper opening and a closed lower end, which is positioned inside the outer cylinder to form a first gas passage between itself and the outer cylinder, and a gas inlet for supplying drying gas to the first gas passage. A radioactive waste treatment container according to claim 1 or claim 2.

4. The cylindrical member is positioned inside the inner cylinder and has a second gas passage formed inside it, and the first gas passage and the second gas passage communicate with the gas outlet. A radioactive waste treatment container according to claim 3.

5. The gas inlet is provided at the bottom of the outer cylinder. A radioactive waste treatment container according to claim 3.

6. The inner cylinder has a cylindrical inner cylinder body and a bottom portion provided at the lower part of the inner cylinder body, and the cylindrical member is integrally provided on the bottom portion. A radioactive waste treatment container according to claim 3.

7. The container body has a heating device arranged on its outer surface. A radioactive waste treatment container according to claim 1.

8. A method for processing radioactive waste using a processing container in which a cylindrical member having a porous cylindrical shape is arranged inside a container body whose lower part is closed, and the upper opening of the container body can be opened and closed by a lid, The steps include: placing radioactive waste between the container body and the cylindrical member through the upper opening of the container body; The steps include closing the upper opening of the container body with the lid, The steps include drying the radioactive waste contained inside the container body, The steps include: discharging the gas from the container body to the outside through a second gas passage formed inside the cylindrical member; A method for processing radioactive waste containing [unclear / unclear].

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