Supercritical water oxidation nuclide removal reactor for radioactive waste

Abstract

A kind of radioactive waste supercritical water oxidation nuclide removal reactor, including cooling jacket, the pressure-bearing reaction cavity is arranged in cooling jacket, the flow guide cavity is arranged in the inside of pressure-bearing reaction cavity, the nuclide salt removal core area is arranged in the middle of flow guide cavity, the end cap material import area is arranged in the top of nuclide salt removal core area, respectively in flow guide cavity and pressure-bearing reaction cavity are provided with residual heat recovery device;Radioactive waste is efficiently degraded in supercritical water oxidation environment, while using the characteristics of nuclide salt solubility extremely low in supercritical water, and inorganic salt hot wall adhesion effect, nuclide is separated using multistage filtration method, so that the migration of radioactive nuclide salt is limited in the core area in the reactor, to avoid nuclide contamination of reactor pressure-bearing wall, end cap and other large volume key parts, at the same time, no additional stirring, scraping and other mechanical devices are arranged in the reactor, to ensure that the device minimizes the generation of radioactive waste after decommissioning;It has significant application value in the field of radioactive waste supercritical water oxidation treatment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of radioactive waste treatment, and particularly relates to a reactor for removing nuclides from radioactive waste by supercritical water oxidation. BACKGROUND

[0002] In the process of carbon peak and carbon neutralization, nuclear energy as a low-carbon clean energy is an important choice for energy transformation in China. With the active, safe and orderly promotion of nuclear power construction, various types of radioactive organic waste, such as radioactive waste resin, waste protective clothing, waste vacuum pump oil, waste TBP solvent and waste degradable protective material, need to be disposed. However, the corresponding waste management work is seriously lagging behind, and the uncertainty of long-term storage and future management of radioactive waste is causing potential safety risks to increase day by day.

[0003] At present, the conventional treatment process mainly includes cement solidification, thermal super compression, incineration method, etc. However, cement solidification has the problems of capacity increase, and the super compression storage process of organic matter will be decomposed by irradiation, which will cause the compression cake to break, the incineration method has a complex tail gas treatment system, etc. The glass solidification technology has slow substantial engineering progress due to high operating temperature and complex waste gas treatment system.

[0004] Supercritical water oxidation technology, as a cutting-edge organic waste treatment technology, has been proven to be able to efficiently degrade radioactive waste resin, waste tri-n-butyl phosphate (TBP) solvent, waste scintillation liquid, waste vacuum pump oil and waste plastic used in the nuclear industry. This technology utilizes the special properties of supercritical water to make radioactive organic waste and oxidizing agents undergo rapid and complete homogeneous oxidation reaction in supercritical water. At the same time, the solubility of nuclide inorganic salt in supercritical water is extremely low, which can separate and remove the nuclide salt in the supercritical water environment.

[0005] However, for the nuclide salt with radioactivity in the reaction process, mechanical stirring, scraping and other mechanical devices are usually used for removal. On the one hand, the mechanical stirring device is unstable under the condition of high temperature and high pressure supercritical water, and on the other hand, the nuclide salt will be contaminated in a large area and a wide range in the reactor, which will increase the radioactive waste after the subsequent decommissioning of the device.

[0006] Chinese patent CN108665993B discloses a nuclear power plant supercritical water oxidation reactor for treating radioactive waste resin of a nuclear power plant, the oxidation reactor comprising a main body portion having an accommodating space inside, and a plurality of feed channels and discharge channels respectively communicating with the accommodating space, further comprising: a filter container arranged in the accommodating space, the feed channel extending into the filter container; a stirring device rotatably arranged in the filter container for crushing and stirring the waste resin; an oxygen channel arranged outside the filter container for injecting oxygen; the material liquid after stirring and oxidation passes through the filter screen of the filter container and is discharged through the discharge channel. The supercritical water oxidation reactor provided by the invention increases the contact area and reaction time of the waste resin and supercritical water, but the additional configuration of the stirring device increases the probability of generating radioactive waste after the product is retired, increases the opportunity of secondary pollution, and increases the cost; and only one filtration through the filter screen is not thorough enough for nuclide removal. SUMMARY

[0007] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a radioactive waste supercritical water oxidation nuclide removal reactor, which realizes efficient degradation of radioactive waste in a supercritical water oxidation environment, utilizes the characteristics of extremely low solubility of nuclide salt in supercritical water, and the inorganic salt thermal wall adhesion effect, adopts a multi-stage filtration method to separate the nuclide, limits the migration of radioactive nuclide salt to the core area of the reactor, avoids the contamination of the nuclide in the key parts of the reactor pressure-bearing wall and end cap, and at the same time, the reactor does not additionally set stirring, scraping and other mechanical devices, to ensure the minimization of radioactive waste generated after the device is retired; the reactor also has the functions of low-temperature material injection, alcohol co-oxidation, cold wall protection and waste heat recovery; and provides a practical solution for the treatment of radioactive waste.

[0008] In order to achieve the above purpose, the technical solution adopted by the present application is:

[0009] A radioactive waste supercritical water oxidation nuclide removal reactor, comprising a cooling water jacket 15, the cooling water jacket 15 is provided with a pressure-bearing reaction cavity 10, the pressure-bearing reaction cavity 10 is provided with a flow guide cavity 11 inside, the flow guide cavity 11 is provided with a nuclide salt removal core area in the middle, the top of the nuclide salt removal core area is provided with an end cap material inlet area, the flow guide cavity 11 and the pressure-bearing reaction cavity 10 are respectively provided with waste heat recovery devices.

[0010] The nuclide salt removal core region is sequentially provided from inside to outside with a nuclide salt induced generation region 19, a nuclide salt generation buffer region 18, a nuclide salt primary filtration region 17 and a nuclide salt multi-stage filtration region 16; wherein the top of the nuclide salt induced generation region 19 is respectively communicated with a high-temperature supercritical water injection inlet N1 in the middle of the end cover material inlet region, a low-temperature material inlet N2, a first oxidizing agent inlet N3; the nuclide salt induced generation region 19 and the nuclide salt generation buffer region 18 outside thereof are provided with a first filter screen 2, the nuclide salt generation buffer region 18 and the nuclide salt primary filtration region 17 outside thereof are provided with a second filter screen 4; the nuclide salt primary filtration region 17 is provided with a fine filter screen block 5; the nuclide salt primary filtration region 17 and the nuclide salt multi-stage filtration region 16 outside thereof are provided with a flow guide purification filter screen 7; the outer wall of the nuclide salt multi-stage filtration region 16 is a core region flow guide wall 8; the nuclide salt multi-stage filtration region 16 is communicated with a second oxidizing agent inlet N4 of the end cover material inlet region; the waste heat recovery device 12 adopts a heat extractor.

[0011] The bottom of the first filter screen 2, the second filter screen 4 and the flow guide purification filter screen 7 is respectively provided with a non-porous nuclide salt collection bin 6; the rough protrusion shape includes an angular shape, a square shape and an irregular shape.

[0012] The side wall bottom of the flow guide cavity 11 is provided with a porous medium channel 13, and the porous medium channel 13 communicates the flow guide cavity 11 with the pressure-bearing reaction cavity 10.

[0013] The end cover material inlet region includes a cover plate 1, the cover plate 1 is provided with a dosing cylinder 1-1 in the middle, the high-temperature supercritical water injection inlet N1, the low-temperature material inlet N2 and the first oxidizing agent inlet N3 are respectively opened on the dosing cylinder 1-1, the cover plate 1 is provided with a sacrificial inner liner 21 at the bottom, the cover plate 1 is filled with a heat insulation filling material 20, and the second oxidizing agent inlet N4 penetrates the cover plate 1 to communicate with the nuclide salt multi-stage filtration region 16.

[0014] The nuclide salt multi-stage filtration region 16 is provided with a plurality of vertical direction partition plates 3 in the nuclide salt primary filtration region 17, one end of the partition plate 3 is connected with a third filter screen 9, the third filter screens 9 on adjacent partition plates 3 are arranged staggeredly to form a flow guide channel in the nuclide salt multi-stage filtration region 16.

[0015] The nuclide salt multi-stage filtration region 16 is provided with a multi-stage filtration outlet 14 in the middle, the bottom of the multi-stage filtration outlet 14 extends to the height of the porous medium channel 13 near the bottom of the flow guide cavity 11; the multi-stage filtration outlet 14 adopts a filter material.

[0016] The pressure-bearing reaction cavity 10 is provided with a cooling water jacket 15 outside, the cooling water jacket 15 is provided with a cooling water inlet N5 on one side of the upper part, the cooling water jacket 15 is provided with a cooling water outlet N6 on the opposite side of the lower part, and the pressure-bearing reaction cavity 10 is provided with a reaction water outlet N7 on the side wall of the upper part.

[0017] The second filter screen 4 is dense at the upper part and sparse at the lower part, and the upper part of the filter screen filters particles with a size not greater than the filter screen block 5, and the lower part of the filter screen filters particles with a size not greater than the first filter screen 2.

[0018] The first filter screen 2, the flow guide buffer filter screen 4, the fine filter screen block 5 and the multi-stage filter outlet 14 are composed of flexible, light and compressible filter screens, and the material includes alloy, asbestos and powder sintered metal.

[0019] The thickness of the fine filter screen block is adjustable.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] 1. The core area of the reactor effectively separates the nuclides. The nuclides are removed in the high-temperature area of the reactor by using the extremely low solubility of the nuclides in supercritical water and the thermal wall adhesion effect, and a rough protrusion is arranged to induce the formation of adhesion of the nuclide salt in the core area. At the same time, a buffer area with the function of inducing the crystallization and adhesion of the nuclide salt is arranged to increase the size of the nuclide salt particles as the reaction area expands, so as to confine most of the nuclide salt in the core area of the reactor and avoid the contamination of the nuclide salt in a large range.

[0022] 2. The reactor does not need additional mechanical nuclide removal devices such as stirrers and scrapers, which avoids the operation failure of the mechanical devices such as stirrers and scrapers under high-temperature and high-pressure conditions, so that the reactor operates more stably. The nuclide salt is filtered and removed by multiple stages and multiple times through the flow guide, filtration coupling and gravity sedimentation effect of the dense and sparse filter screens in the core area, and no mechanical stirring device is arranged, so that the reactor operates more reliably and safely under high-temperature and high-pressure conditions.

[0023] 3. The reactor has the functions of preheating by high-temperature pure supercritical water, cold material injection without preheating of radioactive materials, which avoids the preheating coking and plugging problem of the radioactive materials before entering the reactor; alcohol substances can be mixed in the materials to realize the functions of supercritical water oxidation and alcohol co-oxidation, so that the reaction temperature is higher and the organic matter is degraded more completely; cold wall water is used for cooling and protecting the high-temperature and high-pressure pressure-bearing wall to prevent the over-temperature of the pressure-bearing wall of the reactor; a multi-stage waste heat recovery area is arranged to realize the energy cascade recovery and utilization, which can ensure the safe, energy-saving, stable and reliable operation of the reactor.

[0024] In summary, the present application has the advantages of rapid reaction, complete reaction, excellent volume reduction, less secondary pollution and energy saving based on the supercritical water oxidation technology for treating radioactive waste. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The figure is a structural schematic diagram of the present application.

[0026] Figure 2 The figure is a local enlarged view of the core area.

[0027] Wherein: 1-Cover plate; 1-1-Dosing cylinder; 2-First filter screen; 3-Baffle plate; 4-Second filter screen; 5-Fine filter block; 6-Non-porous nuclide salt collection chamber; 7-Guiding purification filter screen; 8-Core area guiding wall; 9-Third filter screen; 10-Pressurized reaction chamber; 11-Guiding chamber; 12-Waste heat recovery device; 13-Porous media channel; 14-Multi-stage filtration outlet; 15-Cooling water jacket; 16-Nuclide salt multi-stage filtration zone; 17-Nuclide salt primary filtration zone; 18-Nuclide salt generation buffer zone; 19-Nuclide salt induced generation zone; 20-Insulating filling material; 21-Sacrificial liner; N1-High temperature supercritical water inlet; N2-Low temperature material inlet; N3-First oxidant inlet; N4-Second oxidant inlet; N5-Cold wall water inlet; N6-Cold wall water outlet; N7-Reaction water outlet. Detailed Implementation

[0028] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0029] like Figure 1 and Figure 2 As shown, a radioactive waste supercritical water oxidation nuclide removal reactor includes a cooling water jacket 15, a pressure-bearing reaction chamber 10 inside the cooling water jacket 15, a flow guide chamber 11 inside the pressure-bearing reaction chamber 10, a nuclide salt removal core area in the center of the flow guide chamber 11, and a material inlet area with an end cap at the top of the nuclide salt removal core area. Waste heat recovery devices are respectively provided in the flow guide chamber 11 and the pressure-bearing reaction chamber 10.

[0030] The nuclide removal core area is provided with a nuclide-induced generation zone 19, a nuclide generation buffer zone 18, a nuclide primary filtration zone 17, and a nuclide multi-stage filtration zone 16, arranged sequentially from the inside out. The top of the nuclide-induced generation zone 19 is connected to the high-temperature supercritical water inlet N1, the low-temperature material inlet N2, and the first oxidant inlet N3 in the center of the end cap material inlet area. A first filter 2 is provided between the nuclide-induced generation zone 19 and the external nuclide generation buffer zone 18, and a second filter 4 is provided between the nuclide generation buffer zone 18 and the external nuclide primary filtration zone 17. A fine filter block 5 is provided inside the nuclide primary filtration zone 17. A flow-guiding purification filter 7 is provided between the nuclide primary filtration zone 17 and the external nuclide multi-stage filtration zone 16. The outer wall of the nuclide multi-stage filtration zone 16 is the core area flow-guiding wall 8. The nuclide multi-stage filtration zone 16 is connected to the second oxidant inlet N4 of the end cap material inlet area. The waste heat recovery device 12 uses a heat extractor.

[0031] The bottom of the first filter screen 2, the second filter screen 4 and the flow-guiding purification filter screen 7 is provided with a non-porous nuclide salt collection chamber 6; the rough protrusion shape includes sharp corners, squares and irregular shapes.

[0032] The side wall bottom of the flow guide cavity 11 is provided with a porous medium channel 13, and the porous medium channel 13 is communicated with the pressure-bearing reaction cavity 10.

[0033] The end cover material inlet area further comprises a cover plate 1, the cover plate 1 is provided with a dosing cylinder 1-1 in the middle, the high-temperature supercritical water injection inlet N1, the low-temperature material inlet N2 and the first oxidant inlet N3 are respectively opened on the dosing cylinder 1-1, the cover plate 1 is provided with a sacrificial inner liner 21 at the bottom, the cover plate 1 is filled with a heat-insulating filling material 20, and the second oxidant inlet N4 penetrates the cover plate 1 and is communicated with the nuclide salt multi-stage filtering area 16.

[0034] The nuclide salt multi-stage filtering area 16 is provided with a plurality of vertical direction partition plates 3 in the nuclide salt primary filtering area 17, one end of the partition plate 3 is connected with the third filter screen 9, the third filter screens 9 on adjacent partition plates 3 are arranged in a staggered manner, and the flow guide channel is formed in the nuclide salt multi-stage filtering area 16.

[0035] The nuclide salt multi-stage filtering area 16 is provided with a multi-stage filtering outlet 14 in the middle, the multi-stage filtering outlet 14 extends to the height of the porous medium channel 13 near the bottom of the flow guide cavity 11 at the bottom; the multi-stage filtering outlet 14 is made of filtering material, so that the purified reaction fluid uniformly flows out and is heated by the waste heat recovery device 12.

[0036] The pressure-bearing reaction cavity 10 is provided with a cooling water jacket 15 outside, the cooling water jacket 15 is provided with a cooling water inlet N5 on one side of the upper portion, the cooling water jacket 15 is provided with a cooling water outlet N6 on the opposite side of the lower portion, and the pressure-bearing reaction cavity 10 is provided with a reaction water outlet N7 on the side wall of the upper portion.

[0037] The second filter screen 4 is dense at the upper portion and sparse at the lower portion, and the upper portion filtering particle size is not greater than the filtering particle size of the fine dense filter screen block 5, and the lower portion filtering particle size is not greater than the filtering particle size of the first filter screen 2.

[0038] The first filter screen 2, the second filter screen 4, the fine dense filter screen block 5 and the multi-stage filtering outlet 14 are made of flexible, light and compressible filter screens, and the material includes alloy, asbestos and powder sintered metal.

[0039] The thickness of the fine dense filter screen block can be adjusted.

[0040] The working principle of the application is as follows:

[0041] According to the above structure, the supercritical water, oxidant and low-temperature material mixed with alcohol are injected from the end cap material inlet area, mixed and reacted in the induction generation area 19, and the organic matter is degraded efficiently, and the nuclide salt is attached on the first filter screen 2 due to the low solubility in supercritical water and the thermal wall attachment effect. Then the reaction fluid and the nuclide salt continue to pass through the second filter screen 4, most of the nuclide salt is intercepted, at the same time the reaction fluid and the remaining nuclide salt enter the nuclide salt primary filtration area 17 by the flow guiding effect, and are further purified under the action of the fine filter screen block 5, and then enter the multi-stage filtration area for deep treatment; the nuclide salt not attached is collected by each level of the non-porous nuclide salt collection bin 6; under the conditions of flow guiding, gravity sedimentation and multi-stage filtration, the remaining nuclide salt is intercepted by the multi-stage filter screen. After purification, the reaction fluid passes through the filter screen wall of the multi-stage filter outlet 14, and the flow guiding cavity 11 and the pressure-bearing reaction cavity 10, and the waste heat is recovered and utilized, and finally discharged from the outlet N7 of the reactor; each level of filter screen is replaced during operation according to the use requirements and conditions. In the supercritical water oxidation environment, the nuclide salt is separated by the multi-stage filtration method, the migration of the nuclide salt is limited in the core area of the reactor, and the nuclide contamination of the reactor pressure-bearing wall, end cap and other large-volume key parts is avoided; the reactor also has the functions of low-temperature material injection, alcohol co-oxidation, cold wall protection and waste heat recovery.

[0042] In summary, based on the problems existing in the traditional radioactive waste treatment method, the radioactive waste supercritical water oxidation nuclide removal reactor is provided, which can realize efficient degradation of radioactive waste and efficient collection of radioactive nuclide salt in a small range in the reactor, without additional mechanical devices such as stirring and scraping, to ensure that the device minimizes the production of radioactive waste after decommissioning. Thus, inorganic reduction of radioactive waste is realized, which has important application significance for actual radioactive waste treatment.

Claims

1. A supercritical water oxidation nuclide removal reactor for radioactive waste, comprising a cooling jacket (15), characterized in that, The cooling jacket (15) is internally provided with a pressure-bearing reaction cavity (10), the pressure-bearing reaction cavity (10) is internally provided with a flow guide cavity (11), the flow guide cavity (11) is centrally provided with a nuclide salt removal core area, the top of the nuclide salt removal core area is provided with an end cover material inlet area, the flow guide cavity (11) and the pressure-bearing reaction cavity (10) are respectively provided with a residual heat recovery device (12); the nuclide salt removal core area is sequentially provided, from inside to outside, with a nuclide salt induced generation area (19), a nuclide salt generation buffer area (18), a nuclide salt primary filtration area (17) and a nuclide salt multi-stage filtration area (16); wherein the top of the nuclide salt induced generation area (19) is respectively communicated with a high-temperature supercritical water injection inlet (N1), a low-temperature material inlet (N2) and a first oxidizing agent inlet (N3) in the middle of the end cover material inlet area; the nuclide salt induced generation area (19) and the nuclide salt generation buffer area (18) outside the nuclide salt induced generation area (19) are provided with a first filter screen (2), the nuclide salt generation buffer area (18) and the nuclide salt primary filtration area (17) outside the nuclide salt generation buffer area (18) are provided with a second filter screen (4) with rough protrusions; the nuclide salt primary filtration area (17) is provided with a fine filter screen block (5); the nuclide salt primary filtration area (17) and the nuclide salt multi-stage filtration area (16) outside the nuclide salt primary filtration area (17) are provided with a flow guide purification filter screen (7); the outer wall of the nuclide salt multi-stage filtration area (16) is a core area flow guide wall (8); the nuclide salt multi-stage filtration area (16) is communicated with a second oxidizing agent inlet (N4) of the end cover material inlet area; the residual heat recovery device (12) adopts a heat extractor; The bottom of the first filter screen (2), the second filter screen (4) and the flow guide purification filter screen (7) is respectively provided with a non-porous nuclide salt collection bin (6); The bottom of the side wall of the flow guide cavity (11) is provided with a porous medium channel (13), the porous medium channel (13) is communicated with the flow guide cavity (11) and the pressure-bearing reaction cavity (10); The end cover material inlet area comprises a cover plate (1), the cover plate (1) is centrally provided with a dosing barrel (1-1), the high-temperature supercritical water injection inlet (N1), the low-temperature material inlet (N2) and the first oxidizing agent inlet (N3) are respectively opened on the dosing barrel (1-1), the bottom of the cover plate (1) is provided with a sacrificial inner lining (21), the cover plate (1) is filled with a heat insulation filling material (20), the second oxidizing agent inlet (N4) penetrates into the cover plate (1) and is communicated with the nuclide salt multi-stage filtration area (16).

2. A supercritical water oxidation nuclide removal reactor for radioactive waste according to claim 1, characterized in that, The nuclide salt multi-stage filtration area (16) and the bottom of the nuclide salt primary filtration area (17) are provided with a plurality of vertical direction partition plates (3), one end of the partition plate (3) is connected with a third filter screen (9), the third filter screens (9) on the adjacent partition plates (3) are arranged in a staggered manner, and a flow guide channel is formed in the nuclide salt multi-stage filtration area (16).

3. A supercritical water oxidation nuclide removal reactor for radioactive waste according to claim 1, wherein The nuclide salt multi-stage filtration area (16) is centrally provided with a multi-stage filtration outlet (14), the bottom of the multi-stage filtration outlet (14) extends to the height of the porous medium channel (13) near the bottom of the flow guide cavity (11); the multi-stage filtration outlet (14) adopts a filter material.

4. A supercritical water oxidation nuclide removal reactor for radioactive waste according to claim 1, wherein The pressure-bearing reaction cavity (10) is externally provided with a cooling water jacket (15), the upper side of the cooling water jacket (15) is provided with a cooling water inlet (N5), the lower side of the cooling water jacket (15) is provided with a cooling water outlet (N6), and the upper side wall of the pressure-bearing reaction cavity (10) is provided with a reaction water outlet (N7).

5. A supercritical water oxidation nuclide removal reactor for radioactive waste according to claim 1, wherein The second filter screen (4) is dense at the upper part and sparse at the lower part, the upper part of the second filter screen (4) filters particles with a particle size not greater than that of the fine dense filter screen block (5), and the lower part of the second filter screen (4) filters particles with a particle size not greater than that of the first filter screen (2).

6. A supercritical water oxidation nuclide removal reactor for radioactive waste according to claim 1, wherein The first filter screen (2), the second filter screen (4), the fine dense filter screen block (5) and the multi-stage filter outlet (14) are composed of flexible, light and compressible filter screens, and the material includes alloy and asbestos.

7. A supercritical water oxidation nuclide removal reactor for radioactive waste according to claim 1, wherein The shape of the rough protrusions of the rough protrusion second filter screen (4) includes sharp angle shape and square shape.

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