Spent fuel pellet and cladding separation device and separation method

Abstract

The invention relates to the technical field of spent fuel aftertreatment, in particular to a spent fuel pellet and cladding separation device and method. The spent fuel pellet and cladding separation device comprises a charging cavity, a vibrator, a rotary driving mechanism and an inclined driving mechanism. The charging cavity comprises a first cavity body, a second cavity body and a sieve plate, the first cavity body is connected with the second cavity body through the sieve plate, the first cavity body is connected with the feeding port, the air inlet and the cladding outlet, and the second cavity body is connected with the powder outlet and the exhaust port. The vibrator is connected with the charging cavity and used for driving the charging cavity to vibrate. The rotation driving mechanism is connected with the charging cavity and used for driving the charging cavity to rotate with the center shaft as a rotating shaft. The inclined driving mechanism is connected with the charging cavity and used for driving the charging cavity to incline from one end of the center shaft to the other end of the center shaft. According to the device and the method, high-quality and high-efficiency separation of the spent fuel pellet and the cladding can be realized, the waste output in the spent fuel post-treatment process can be reduced, and the spent fuel post-treatment energy efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of spent fuel reprocessing technology, and in particular to a spent fuel pellet and cladding separation device and method. Background Technology

[0002] In nuclear power plant reactors, nuclear fuel (usually ceramic pellets sintered from uranium dioxide) is sealed within cladding tubes made of metallic alloys (such as zirconium alloys), forming fuel rods. Irradiated nuclear fuel is called spent fuel, which contains a large amount of fission products and is highly radioactive. To achieve a closed-loop nuclear fuel cycle, improve uranium resource utilization, and reduce radioactive waste, spent fuel reprocessing is necessary. Safely and efficiently separating spent fuel pellets from the metallic cladding is one of the key initial steps in the reprocessing process. Currently, the mainstream technology for separating spent fuel pellets from the cladding is mechanical cutting and dissolution. This method typically involves first cutting the fuel rods into short segments using a shearing machine, then dissolving the exposed fuel pellets using a chemical solvent (such as hot nitric acid), while the metallic cladding remains as an insoluble substance, thus achieving separation. However, this method has many inherent drawbacks: large amounts of secondary waste, high nuclear criticality safety risks, and difficulties in equipment corrosion and maintenance.

[0003] To overcome the aforementioned shortcomings, existing technologies typically employ multiple solvent-free or dry separation methods to achieve the disintegration and separation of spent fuel pellets and cladding. For example, spent fuel pellets and cladding are treated in a high-temperature, oxidizing atmosphere (such as air or oxygen). During this process, only a very small amount of oxidation occurs on the surface of the zirconium cladding tube, ensuring the integrity of the overall cladding structure after separation, while the uranium dioxide pellets are oxidized into uranium octoxide powder. However, during the aforementioned oxidation process, the volume of the uranium octoxide powder expands. Under static conditions, the powder can become stuck in the zirconium tube, preventing further oxygen penetration and preventing the powder from detaching from the zirconium tube, thus failing to achieve effective pellet separation. In fact, existing separation devices generally suffer from problems such as: the inner layer oxidation rate of uranium dioxide (UO2) in static oxidation is less than 60%, and the sticking rate of uranium octoxide (U3O8) exceeds 30%; the separation rate of dynamic oxidation is only around 85%, thus failing to meet the separation requirement of ≥99% pellet separation rate in spent fuel reprocessing. In addition, there are methods for separation using mechanical ejection to achieve low fuel consumption, but these methods involve a small amount of operation and cannot be used industrially. Summary of the Invention

[0004] This invention provides a spent fuel pellet and cladding separation device and method to solve the defects of existing technologies in the reprocessing of spent fuel, such as large amount of secondary waste, powder jamming, and incomplete oxidation. It can not only achieve high-quality and efficient separation of spent fuel pellets and cladding, but also further separate volatile fission products such as tritium, iodine, carbon, krypton, and xenon, greatly reducing the amount of waste generated in the spent fuel reprocessing process.

[0005] This invention provides a spent fuel pellet and cladding separation device, comprising: a loading chamber including a first chamber, a second chamber, and a sieve plate, wherein the first chamber is connected to the second chamber via the sieve plate, the first chamber is connected to a feed inlet, an air inlet, and a cladding outlet, and the second chamber is connected to a powder outlet and an air outlet; a vibrator connected to the loading chamber for driving the loading chamber to vibrate; a rotary drive mechanism connected to the loading chamber for driving the loading chamber to rotate about a central axis, the central axis being the axis of the loading chamber; and a tilting drive mechanism connected to the loading chamber for driving the loading chamber to tilt from one end to the other along the central axis.

[0006] According to the present invention, a spent fuel pellet and cladding separation device is provided, wherein the first cavity is at least partially inserted into the second cavity.

[0007] According to the present invention, a spent fuel pellet and cladding separation device is provided, wherein the loading chamber is provided with a first end and a second end, the first chamber is connected to the first end, and the second chamber is connected to the second end; the sieve plate is configured as the side wall of the first chamber near the end plate; and / or the sieve plate is configured as the end plate of the first chamber.

[0008] According to the present invention, a spent fuel pellet and cladding separation device is provided, wherein a plurality of screen holes are distributed on the screen plate, and each of the screen holes is uniformly distributed circumferentially along the side wall of the first cavity near the end plate; and / or each of the screen holes is distributed at a position near the outer edge of the end plate of the first cavity.

[0009] According to the present invention, a spent fuel pellet and cladding separation device is provided, wherein the loading chamber further includes: a threaded rib formed on the inner wall of the first cavity, the threaded rib being disposed at a position near the first end of the loading chamber; a plurality of baffles connected to the inner wall of the first cavity, each baffle being disposed at the position of the screen plate; each baffle being uniformly arranged along the circumference of the first cavity, and each baffle being disposed along the central axis.

[0010] According to the present invention, a spent fuel pellet and cladding separation device is provided, wherein the rotary drive mechanism includes: a gear disk connected to the loading chamber; and a rotary drive motor, wherein the output shaft of the rotary drive motor is connected to the gear disk through tooth meshing.

[0011] According to the present invention, a spent fuel pellet and cladding separation device includes a tilting drive mechanism comprising: a support platform supported under the loading chamber; a first drive unit connected to the support platform; and a second drive unit connected to the first drive unit, wherein the second drive unit is equipped with a connecting shaft, and the first drive unit is meshed with the connecting shaft via a worm gear transmission mechanism to enable the first drive unit to rotate relative to the connecting shaft; wherein the connecting shaft is arranged perpendicular to the central axis of the loading chamber.

[0012] According to the present invention, a spent fuel pellet and cladding separation device further includes a heating and insulation mechanism, which includes a thermocouple and an insulation layer. The heating and insulation layer is wrapped around the outer wall of the charging chamber, and the thermocouple is disposed between the heating and insulation layer and the outer wall of the charging chamber.

[0013] According to the present invention, a spent fuel pellet and cladding separation device further includes: a cladding receiving tank connected to the cladding outlet; a powder receiving tank connected to the powder outlet; and a balance connected to the powder receiving tank.

[0014] The present invention also provides a method for separating spent fuel pellets from their cladding, which is performed using the spent fuel pellet and cladding separation device described above; the method for separating spent fuel pellets from their cladding includes the following.

[0015] The loading chamber is tilted toward the powder outlet using a tilting drive mechanism, and the loading chamber is rotated using a rotation drive mechanism.

[0016] Spent fuel pellets and their casings are fed into the first chamber of the charging chamber through the feed inlet. The spent fuel short segments undergo an oxidation reaction in the first chamber and disintegrate to form casings and powder.

[0017] The feeding chamber is driven to vibrate by a vibrator, and the powder enters the second cavity of the feeding chamber through the sieve plate, and all the powder is discharged through the powder outlet.

[0018] After all the powder has been discharged, the tilting drive mechanism drives the loading chamber to tilt toward the shell outlet end, so that the shell leaves the first chamber through the shell outlet.

[0019] The spent fuel pellet and cladding separation device provided by this invention includes a loading chamber, a vibrator, a rotary drive mechanism, and a tilting drive mechanism. The loading chamber includes a first chamber, a second chamber, and a sieve plate. The first chamber is connected to the second chamber via the sieve plate. The first chamber connects to a feed inlet, an air inlet, and a cladding outlet. The second chamber connects to a powder outlet and an air outlet. After the spent fuel pellets and cladding undergo an oxidation reaction in the first chamber, the resulting powder passes through the sieve plate into the second chamber and is then discharged through the powder outlet. The cladding, however, is blocked by the sieve plate and remains in the first chamber, being discharged through the cladding outlet. The vibrator is connected to the loading chamber and drives the loading chamber to vibrate. The vibration of the loading chamber accelerates the separation of the cladding and powder and effectively prevents powder from getting stuck on the sieve plate and adhering to the inner wall of the loading chamber. The rotary drive mechanism is connected to the loading chamber and drives the loading chamber to rotate about its central axis. The tilting drive mechanism is connected to the loading chamber and drives the loading chamber to tilt from one end of the central axis to the other. Both the rotary drive mechanism and the tilting drive mechanism can facilitate the disintegration and discharge of spent fuel pellets from their cladding. This spent fuel pellet and cladding separation device and method can not only achieve high-quality and efficient separation of spent fuel pellets and cladding, but also further separate volatile fission products such as tritium, iodine, carbon, krypton, and xenon, greatly reducing the amount of waste generated during spent fuel reprocessing.

[0020] Furthermore, the separation device of the present invention utilizes a combination of a rotary drive mechanism, a tilting drive mechanism, and a vibrator. This not only catalyzes the oxidation reaction of spent fuel short segments in the charging chamber, improving reaction efficiency and sufficiency, but also catalyzes the disintegration of spent fuel short segments through the combination of rotation and vibration. The combination of rotation and tilting controls the efficient collection of the disintegrated shell and powder, reducing secondary waste residue. Moreover, the combination of rotation, vibration, and tilting further accelerates the removal of the disintegrated shell and powder, effectively preventing powder from sticking to the walls and getting stuck in the pipes, greatly improving the powder recovery rate, and further enhancing the efficiency and effectiveness of post-processing.

[0021] Therefore, the separation device described in this invention can achieve the separation of spent fuel pellets from their cladding. The alumina content of the inner layer of uranium dioxide in the short segment of spent fuel far exceeds 60%, and the jamming rate of uranium octoxide is less than 30%. Furthermore, the separation rate through dynamic oxidation reaches over 99%, far exceeding the efficiency of static separation, fully meeting the separation requirements for pellet separation rate in spent fuel reprocessing processes. Moreover, the production capacity of this separation device is also significantly higher than that of static structures. Furthermore, this separation device is adaptable to various spent fuel reprocessing processes, including dry and aqueous reprocessing, demonstrating very high adaptability. Additionally, for high burnup spent fuel, increasing the time can maximize the separation and recovery of uranium dioxide. Moreover, in engineering applications, scaling up the structural size will yield better results because the drop distance of the short segment is greater.

[0022] The present invention also provides a method for separating spent fuel pellets from their cladding, which is performed using the aforementioned spent fuel pellet and cladding separation device. This method possesses all the advantages of the aforementioned spent fuel pellet and cladding separation device, which will not be elaborated further here. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of the spent fuel pellet and cladding separation device provided by the present invention.

[0025] Figure 2 This is a cross-sectional view of the loading chamber provided by the present invention.

[0026] Figure 3 This is a schematic diagram of the tilting drive mechanism provided by the present invention.

[0027] Figure label: 1. Feed inlet; 2. Loading chamber; 201. First end; 202. Second end; 210. First cavity; 211. Spiral rib; 212. Baffle; 220. Second cavity; 230. Sieve plate; 231. Sieve hole; 3. Heating and heat preservation mechanism; 4. Exhaust port; 5. Vibrator; 6. Shell outlet; 7. Powder outlet; 8. Inclined drive mechanism; 81. Support platform; 82. First drive unit; 83. Second drive unit; 84. Hinge shaft; 85. Worm gear; 86. Worm; 87. Handle; 9. Shell receiving tank; 10. Powder receiving tank; 11. Bracket; 12. Balance; 13. Rotary drive motor; 14. Gear disk; 15. Flange. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] The following is combined Figures 1-3 The present invention describes a spent fuel pellet and cladding separation device (hereinafter referred to as the "separation device" or "device").

[0030] like Figure 1 As shown, the spent fuel pellet and cladding separation device of this embodiment includes a loading chamber 2, a vibrator 5, a rotary drive mechanism, and a tilting drive mechanism 8. The loading chamber 2, serving as the main reaction chamber, is preferably mounted on a support 11 to ensure the overall stable operation of the device. (Reference) Figure 1 and Figure 2 As shown, the loading chamber 2 includes a first chamber 210, a second chamber 220, and a sieve plate 230. The first chamber 210 is connected to the second chamber 220 via the sieve plate 230. The first chamber 210 is connected to the feed inlet 1, the air inlet (not shown in the figure), and the cladding outlet 6. The second chamber 220 is connected to the powder outlet 7 and the exhaust port 4. After the spent fuel pellets and cladding undergo an oxidation reaction in the first chamber 210, the resulting powder passes through the sieve plate 230 into the second chamber 220 and is then discharged through the powder outlet 7. The cladding, however, is blocked by the sieve plate 230 and remains in the first chamber 210 before being discharged through the cladding outlet 6. A vibrator 5 is connected to the loading chamber 2 and is used to drive the loading chamber 2 to vibrate. The vibration of the loading chamber 2 accelerates the separation of the cladding and the powder and effectively prevents the powder from getting stuck on the sieve plate 230. A rotary drive mechanism is connected to the loading chamber 2. A rotary drive mechanism drives the charging chamber 2 to rotate around its central axis, ensuring sufficient contact between the spent fuel pellets and cladding within the chamber and the oxygen-containing gas, thereby improving oxidation efficiency. A tilting drive mechanism 8 connects to the charging chamber 2. This mechanism tilts the charging chamber 2 from one end of its central axis to the other. Tilting the charging chamber 2 towards the powder outlet 7 guides the powder to exit more quickly; similarly, tilting the charging chamber 2 towards the cladding outlet 6 guides the cladding to exit more quickly. Furthermore, the vibrator 5 promotes the discharge of both powder and cladding, preventing pipe jamming and wall adhesion. Thus, the rotary drive mechanism and the tilting drive mechanism 8 work synergistically to promote the disintegration and discharge of the spent fuel pellets.

[0031] Understandably, the spent fuel pellets in the short segment are uranium dioxide pellets, which will oxidize into uranium octoxide powder under certain conditions. The separation device described in this embodiment can achieve at least two technical effects. First, rapid pulverization and recovery of spent fuel: Uranium dioxide spent fuel will rapidly oxidize into uranium octoxide in an oxygen-containing atmosphere. Uranium octoxide is in a certain powder form, and theoretically, the overall volume of the oxidized spent fuel is several times larger than the volume of the pellet state. However, under static conditions, the uranium octoxide generated on the surface of the spent fuel will prevent oxygen from diffusing inward, resulting in a very slow oxidation rate of the internal uranium dioxide. More seriously, the uranium octoxide powder will get stuck in the cladding tube and cannot be automatically separated. Spent fuel is highly radioactive, and the uranium octoxide powder stuck in the alloy cladding tube is difficult to completely separate from the cladding. If a water-based reprocessing process is subsequently used, the pellet separation can be completed by gradually dissolving the powder. However, dry separation requires complete separation of the uranium octoxide powder and the cladding tube. The separation device of this invention utilizes the dynamic rotation of the charging chamber 2 to promote the separation of spent fuel cores. Specifically, during the oxidation of uranium dioxide to uranium octoxide, the rotation keeps the cladding tube within the charging chamber 2 in a fully three-dimensional dynamic state. The uranium octoxide produced on the surface detaches from the cladding tube in a timely manner, allowing oxygen to fully contact the unreacted uranium dioxide, thus achieving rapid oxidation. Secondly, the pulverized uranium octoxide powder separates efficiently from the cladding tube in a timely manner: In the separation device of this invention, during the rotation of the charging chamber 2, the vibration generated by the vibrator 5 accelerates the detachment of the uranium octoxide powder, which then passes through the sieve plate 230 from the first chamber 210 and enters the second chamber 220. The sieve plate 230 can block large pieces of cladding within the first chamber 210, thereby achieving efficient separation of the core and cladding.

[0032] In this embodiment, as Figure 1 and Figure 2 As shown, the air inlet is connected to the first chamber 210 and is used to introduce oxygen-containing gas, such as air or oxygen, into the first chamber 210. The exhaust port 4 is connected to the second chamber 220 and is used to discharge the exhaust gas after the reaction in the second chamber 220. Thus, in combination with the air inlet, it ensures that the oxygen content in the loading chamber 2 is within the range required for the oxidation reaction.

[0033] Therefore, the separation device of this embodiment of the invention can utilize the combination of the rotary drive mechanism, the tilt drive mechanism 8 and the vibrator 5 to not only catalyze the oxidation reaction of spent fuel short segments in the charging chamber 2, improving reaction efficiency and reaction sufficiency, but also catalyze the disintegration of spent fuel short segments through the combination of rotation and vibration. The combination of rotation and tilt controls the accurate discharge of the disintegrated shell and powder, reducing secondary waste residue. Furthermore, the combination of rotation, vibration and tilt further accelerates the removal of the disintegrated shell and powder, and effectively avoids situations such as powder sticking to the wall and blocking the pipe, greatly improving the powder recovery rate and further improving the efficiency and effect of post-processing.

[0034] In some embodiments, such as Figure 1 As shown, the loading chamber 2 has a first end 201 and a second end 202. The first cavity 210 is connected to the first end 201. The second cavity 220 is connected to the second end 202. Preferably, a first flange connection mechanism and a second flange connection mechanism are respectively installed at the first end 201 and the second end 202 of the loading chamber 2 to ensure that the rotating loading chamber 2 does not interfere with other pipeline channels (such as feed pipe, shell outlet 6, powder outlet 7 and exhaust pipe).

[0035] In some specific embodiments, such as Figure 1 As shown, the separation device also includes a cladding receiving tank 9 and a powder receiving tank 10. The cladding receiving tank 9 is connected to the cladding outlet 6 and is used to receive the cladding discharged from the cladding outlet 6. The powder receiving tank 10 is connected to the powder outlet 7 and is used to receive the uranium octoxide powder discharged from the powder outlet 7. The pipe connecting the air inlet to the first cavity 210 and the pipe connecting the cladding receiving tank 9 to the cladding outlet 6 are both connected to the first flange connection mechanism. Similarly, the pipe connecting the exhaust port 4 to the second cavity 220 and the pipe connecting the powder receiving tank 10 to the powder outlet 7 are both connected to the second flange connection mechanism. In the three-dimensional dynamic state of the loading chamber 2, which is in rotation and / or vibration, the first flange connection mechanism and the second flange connection mechanism can ensure that the above-mentioned pipes remain statically fixed, avoiding mutual interference and affecting the rotation and vibration of the loading chamber 2.

[0036] Understandably, in order to reliably control the opening and closing of the above-mentioned air inlet, exhaust outlet 4, shell outlet 6 and powder outlet 7, and to ensure a purer oxidation reaction environment in the loading chamber 2, it is preferable to install valves on each of the above-mentioned pipelines.

[0037] In some embodiments, such as Figure 1 and Figure 2As shown, the first cavity 210 of the loading chamber 2 is at least partially inserted into the second cavity 220. The insertion connection structure between the first cavity 210 and the second cavity 220 can increase the surface area of ​​the first cavity 210 inside the second cavity 220, thereby increasing the position where the sieve plate 230 can be set, that is, increasing the setting area of ​​the sieve plate 230, thereby increasing the efficiency and timeliness of powder passing through the sieve plate 230, and better avoiding the occurrence of powder sticking to the wall and clogging the sieve plate 230.

[0038] In some embodiments, such as Figure 1 and Figure 2 As shown, to improve separation efficiency, enhance the timeliness and effectiveness of powder passing through the sieve plate 230, and prevent powder from adhering to the wall, the sieve plate 230 is preferably configured as the side wall of the first cavity 210 near the end plate; and / or the sieve plate 230 is configured as the end plate of the first cavity 210. That is, the sieve plate 230 can be configured as the side wall of the first cavity 210 near the second end 202, or as the end plate of the first cavity 210 near the second end 202, or both. Using the side wall and end plate of the first cavity 210 located inside the second cavity 220 as the sieve plate 230 can effectively increase the area through which the powder is sieved, thereby improving the efficiency of powder sieving. In this embodiment, the circumferential side wall of the first cavity 210 near the second end 202 and the end face of the first cavity 210 near the second end 202 are both configured as sieve plates 230. This configuration increases the area through which the powder passes through the sieve plate 230, meaning that the disintegrated powder can enter the second cavity 220 through either the side wall of the first cavity 210 or the end plate of the first cavity 210.

[0039] In some embodiments, such as Figure 1 and Figure 2As shown, a plurality of sieve holes 231 are preferably distributed on the sieve plate 230. Each sieve hole 231 is evenly distributed circumferentially along the side wall of the first cavity 210 near the end plate; and / or each sieve hole 231 is distributed near the outer edge of the end plate of the first cavity 210. Preferably, the opening ratio of the sieve holes 231 on the sieve plate 230 accounts for more than 60% of the area of ​​the opening position of the sieve plate 230. The above arrangement can better combine with the tilting drive mechanism 8. When the loading cavity 2 is tilted towards the end of the powder outlet 7, that is, when the loading cavity 2 is tilted to the state where the first end 201 is higher than the second end 202, the disintegrated powder accumulates at the bottom of the side wall of the first cavity 210 and the lower side connection of the end face. In this case, more sieve holes 231 are distributed on the side wall and near the edge of the end plate, which can greatly improve the powder passing efficiency and prevent the powder from getting stuck on the sieve plate 230. Furthermore, this structural design can be used in conjunction with the vibrator 5. When the loading chamber 2 is vibrating, the powder will be deposited at the bottom of the first chamber 210 due to gravity. Additionally, this structural design can be used with a rotary drive mechanism. The powder, under the influence of centrifugal force, will be flattened into a larger area on the circumferential sidewalls of the first chamber 210. Simultaneously, the vibration force allows the powder to pass through the sieve holes 231 more quickly into the second chamber 220, and also allows it to be vibrated more quickly from the second chamber 220 to the powder outlet 7, ensuring efficient powder discharge.

[0040] In some specific embodiments, the ratio of the length of the sieve plate 230 to the length of the first cavity 210 is preferably in the range of 1 / 5 to 2 / 3, so that the area of ​​the sieve holes 231 on the sieve plate 230 can better cover the area where the disintegrated powder is spread out, increasing the powder throughput. Preferably, the diameter of the sieve holes 231 is smaller than the diameter of the casing to prevent the casing from leaking into the second cavity 220. Preferably, the diameter of the sieve holes 231 is in the range of 2mm to 8mm, more preferably 3mm to 5mm, so as to better accommodate the passage of powder and prevent large nodular powder clumps from passing through the sieve holes 231 and affecting the quality of the recovered powder.

[0041] In some embodiments, such as Figure 2 As shown, the loading chamber 2 also includes threaded ribs. The threaded ribs are formed on the inner wall of the first cavity 210 and are located near the first end 201 of the loading chamber 2. The threaded ribs protrude relative to the inner wall of the first cavity 210. During rotation, the threaded ribs guide and push the spent fuel short section to rotate around the interior of the first cavity 210. This increases the self-rotation of the spent fuel short section, thus making the oxidation reaction more complete. Furthermore, the rotation of the spent fuel short section around the interior of the first cavity 210 accelerates disintegration, and during the cladding discharge process, it can push the cladding to move within the first cavity 210 in the opposite direction, thus promoting faster and more stable discharge of the cladding from the cladding outlet 6.

[0042] Understandably, the spiral ribs allow for better integration with the tilting drive mechanism 8. When the loading chamber 2 is tilted towards the end of the shell outlet 6, i.e., when the loading chamber 2 is tilted until the first end 201 is lower than the second end 202, since the powder has already been discharged from the second chamber 220, the shell remaining in the first chamber 210 moves faster towards the shell outlet 6 at the first end 201 due to gravity within the tilted loading chamber 2. This structure also works in conjunction with the vibrator 5; when the loading chamber 2 is vibrating, the shell moves faster towards the shell outlet 6 at the first end 201 due to gravity. Furthermore, this structure can be integrated with the rotary drive mechanism; the shell, subjected to centrifugal force, is continuously agitated by the spiral ribs 211, causing it to rotate within the first chamber 210 and move around the inner wall of the first chamber 210, thus fully agitating the shell within the first chamber 210, preventing blockage of the shell outlet 6 during discharge, and improving shell discharge efficiency. In this embodiment, the length of the threaded rib is set to 1 to 2 times the circumference of the inner wall of the first cavity 210. The height of the threaded rib is 3mm to 10mm. The pitch of the threaded rib is 10mm to 30mm.

[0043] In some embodiments, such as Figure 2 As shown, the loading chamber 2 also includes several baffles 212. Each baffle 212 is connected to the inner wall of the first chamber 210. Each baffle 212 is positioned near the sieve plate 230. Each baffle 212 is evenly arranged circumferentially along the first chamber 210, and each baffle 212 is arranged along the central axis. Preferably, the baffles 212 protrude relative to the inner wall of the first chamber 210. During the rotation of the first chamber 210, the baffles 212 can guide the short segments to move to higher positions, increasing the three-dimensional movement amplitude of the short segments within the chamber, thereby making the oxidation reaction more complete and accelerating the disintegration of the powder and the coating; furthermore, the baffles 212 can also push the powder more evenly onto the sieve plate 230, so as to push the powder through the sieve plate 230 faster and improve the powder throughput.

[0044] In some embodiments, such as Figure 1 As shown, the rotary drive mechanism includes a gear disk 14 and a rotary drive motor 13. The gear disk 14 is connected to the loading chamber 2. The output shaft of the rotary drive motor 13 is connected to the gear disk 14 via gear meshing. Preferably, the gear disk 14 is coaxially mounted on the second end 202 of the loading chamber 2, and the first end 201 of the loading chamber 2 is connected to the first flange connection mechanism via a flange 15. This structural arrangement allows the output shaft of the rotary drive motor 13 to be connected to the gear disk 14 via a drive gear, thereby driving the loading chamber 2 to rotate around its central axis. The flange 15 and the gear disk 14 ensure that both ends of the loading chamber 2 rotate coaxially and effectively prevent the rotation of the loading chamber 2 from interfering with surrounding components.

[0045] In some embodiments, such as Figure 1 and Figure 3 As shown, the tilting drive mechanism 8 includes a support platform 81, a first drive unit 82, and a second drive unit 83. The support platform 81 is supported under the loading cavity 2. Preferably, the support platform 81 is positioned to avoid other components installed at both ends of the loading cavity 2, such as the pipes connecting the casing receiving tank 9 and the powder receiving tank 10, which are both located on the rear side of the support platform 81. The first drive unit 82 is connected to the support platform 81. The second drive unit 83 is connected to the first drive unit 82. The second drive unit 83 is equipped with a connecting shaft. The first drive unit 82 is engaged with the connecting shaft through a worm gear 85 and worm 86 transmission mechanism, so that the first drive unit 82 can rotate relative to the connecting shaft. The connecting shaft is perpendicular to the central axis of the loading cavity 2. The worm gear 85 and worm 86 transmission mechanism can drive the second drive unit 83 to rotate relative to the first drive unit 82 around the connecting shaft, thereby ensuring that the loading cavity 2 can rotate around the connecting shaft, that is, to achieve tilting of the loading cavity 2 from one end to the other along the central axis.

[0046] In some specific embodiments, such as Figure 3 As shown, the worm gear 85 and worm 86 transmission mechanism includes a worm gear 85 and a worm 86. The worm gear 85 is mounted on a connecting shaft, with the axis of the connecting shaft as the rotation center line of the worm gear 85. The worm 86 is connected to the second drive unit 83 and is connected to the worm gear 85 through tooth meshing. The worm 86 is preferably arranged parallel to the central axis of the loading chamber 2. The rotation of the worm 86 drives the worm gear 85 to rotate, thereby driving the second drive unit 83 to rotate relative to the first drive unit 82. Preferably, the worm gear 85 and worm 86 transmission mechanism also includes a handle 87, which is connected to the worm 86 for driving the worm 86 to rotate. Alternatively, the worm 86 can be connected to a drive motor for automated rotation.

[0047] Understandably, in order to further improve the rotational accuracy of the support platform 81, and thus improve the precise control of the tilt angle of the loading chamber 2, it is preferable that the first drive unit 82 and the second drive unit 83 are respectively provided with arc-shaped linear connecting surfaces, for example... Figure 3 As shown. A guide rail is provided on the connection surface between the first drive unit 82 and the second drive unit 83, and a slider is provided on the second drive unit 83. The slider is assembled in the corresponding guide rail, so that the second drive unit 83 can rotate relative to the first drive unit 82 along the trajectory of the connection surface.

[0048] In some embodiments, such as Figure 1As shown, the separation device also includes a heating and insulation mechanism 3. The heating and insulation mechanism 3 ensures that the charging chamber 2 is at an optimal temperature for the oxidation reaction, thereby further improving the efficiency of the oxidation reaction between spent fuel pellets and the cladding. Preferably, the heating and insulation mechanism 3 includes a thermocouple and an insulation layer. The heating and insulation layer is wrapped around the outer wall of the charging chamber 2. The thermocouple is positioned between the heating and insulation layer and the outer wall of the charging chamber 2. The thermocouple can be directly connected to the outer wall of the charging chamber 2, thereby heating the charging chamber 2. The thermocouple is wrapped with an insulation layer to prevent heat loss.

[0049] In some embodiments, such as Figure 1 As shown, the separation device also includes a balance 12. The balance 12 is connected to the powder receiving tank 10. The balance 12 can monitor the powder recovery rate in real time.

[0050] In some embodiments, such as Figure 1 As shown, the separation device also includes a support frame 11 and a lifting frame. The support frame 11 serves as a supporting structure placed on the ground, and the loading chamber 2 and the components connected to its two ends are mounted on the support frame 11 via a tilting drive mechanism 8. To ensure that the balance 12 can be stably placed and connected to the powder receiving tank 10, it is preferable that the balance 12 is placed on the lifting frame. The lifting frame allows for more accurate and convenient adjustment of the height of the balance 12.

[0051] The method for separating spent fuel pellets from their cladding provided by the present invention is described below. The method for separating spent fuel pellets from their cladding described below can be referred to in correspondence with the device for separating spent fuel pellets from their cladding described above.

[0052] The separation method described in this embodiment of the invention is performed using the separation device described above. The separation method includes the following steps.

[0053] Step 1: Use the tilting drive mechanism 8 to drive the loading chamber 2 to tilt towards the powder outlet 7, and use the rotation drive mechanism to drive the loading chamber 2 to rotate.

[0054] Step 2: The spent fuel short segments (the structure of the core block and the shell connected) are put into the first cavity 210 of the charging chamber 2 through the feed port 1. The spent fuel short segments undergo an oxidation reaction in the first cavity 210 and disintegrate to form the shell and powder.

[0055] Step 3: The vibrator 5 drives the loading chamber 2 to vibrate, and the powder enters the second chamber 220 of the loading chamber 2 through the sieve plate 230, and all the powder is discharged through the powder outlet 7.

[0056] Step 4: After all the powder has been discharged, the tilting drive mechanism 8 is used to drive the loading chamber 2 to tilt towards the shell outlet 6 so that the shell leaves the first chamber 210 through the shell outlet 6.

[0057] In some specific implementations, the specific process of this separation method is as follows: the device is powered on; the tilting drive mechanism 8 drives the entire charging chamber 2 to tilt the furnace body at more than 5° towards the powder outlet, and the rotary drive mechanism is started to rotate the charging chamber 2; the feed port 1 is opened, and a short section of spent uranium dioxide fuel (with cladding) is added from the feed port 1. After feeding, the feed port is closed, the valve of the air inlet is opened, and oxygen-containing gas is delivered into the charging chamber 2. The oxygen content can be 10%~80%, with air preferred; the heating and heat preservation mechanism 3 is started to heat the charging chamber 2. The heating rate is not limited, and the target temperature is 400℃~700℃, with 500℃~600℃ being optimal. Then, the temperature is kept constant for more than 1 hour, which varies depending on the amount added and the uranium dioxide burnup. The goal is to recover all the uranium dioxide powder; the powder receiving tank 10 is connected to the balance 12, which can monitor the powder recovery rate in real time. Once the reading of the balance 12 remains constant, the temperature can be lowered. After cooling to room temperature, the cavity is rotated in the opposite direction, and the tilting drive mechanism 8 drives the loading cavity 2 to tilt the furnace body towards the shell outlet 6 to collect the shell.

[0058] The following describes in detail the spent fuel pellet and cladding separation device and method provided by the present invention, using four specific experimental examples and a comparative example.

[0059] Experiment Example 1 (La2O3 Simulation Experiment): This experiment used lanthanum oxide (La2O3) powder as the simulated sample. Five zirconium alloy clad tubes were used, each approximately 2 cm in length, with cladding masses of 3.1327 g, 3.1310 g, 3.1430 g, 3.1394 g, and 3.1446 g, respectively. The weighed La2O3 powder was loaded into the cladding tubes and manually compacted, with a total loading mass of 6.0129 g. The experiment was conducted in an air atmosphere, with the furnace temperature in loading chamber 2 maintained at room temperature. The reverse rotation time was 30 min, and the rotation speed was 20 r / min. -1 The vibration pressure was approximately 0.1 MPa, the duration was 30 seconds, and vibration was performed once every 10 minutes for a total of three times. The experimental results showed that the total mass of recovered powder was 5.8175 g, and the powder recovery rate was calculated to be 96.75%. This indicates that the powder separation effect was good under these conditions, the separation device operated stably, and it possessed high separation efficiency.

[0060] Experiment Example 2 (UO2 core block, three 3cm clad tubes): The experiment used UO2 core blocks as the experimental sample. Three zirconium alloy clad tubes, each with an inner diameter of 8.2mm and a length of approximately 3cm, were used, each containing two UO2 core blocks. The core block masses in each clad tube were 9.8364g, 10.4810g, and 10.3916g, respectively. After loading the samples, the two ends of the tubes were appropriately pinched together to prevent the core blocks from falling off during the pulverization process. The experiment was conducted in an air atmosphere, with a heating rate set at 10℃·min. -1The furnace temperature was raised from room temperature to 500℃ and held for 3 hours; the temperature of the thermocouple resistance wire was approximately 750℃. The rotation speed was 30 r / min. -1 Airflow rate: 0.3~0.5 L·min -1 After the heat preservation period, the furnace body was tilted and vibrated three times (vibration pressure 0.1 MPa, 1 min each time), then switched to forward rotation to remove the cladding tube from the furnace cavity and collect the powder. Experimental results showed that the total initial mass of the three samples was 30.709 g, and the recovered powder mass after pulverization was 31.489 g. Based on the chemical conversion relationship UO2→U3O8, the uranium element mass before and after the reaction was calculated to be 27.069 g and 26.708 g, respectively, resulting in a powder recovery rate of 98.64%. The results indicate that under these conditions, the pellet pulverization was sufficient, the separation effect was good, and very little residue remained in the zirconium tube, demonstrating that the prototype exhibits high pulverization and separation efficiency.

[0061] Experiment Example 3 (UO2 core block, three 4cm clad tubes): The experiment used UO2 core blocks as the experimental sample. Three 4cm long zirconium alloy clad tubes, with an inner diameter of 8.2mm, were used, each containing two UO2 core blocks. The masses of each core block were 4.9832g, 5.1716g, 5.0235g, 4.8937g, 5.1098g, and 4.9242g, respectively. The total mass was approximately 30.1060g. After loading the sample, the two ends of the tubes were appropriately pinched together to prevent the core block from falling off during the pulverization process. The experiment was conducted in air, with a heating rate set at 10℃·min. -1 The furnace temperature was raised from room temperature to 500℃ and held for 3 hours; the temperature of the thermocouple resistance wire was approximately 750℃. The rotation speed was 30 r / min. -1 Air flow rate 0.4 L·min -1 After the heat preservation period, the furnace body was tilted and vibrated three times (vibration pressure 0.1 MPa, 1 min each time), then switched to forward rotation to remove the cladding tube from the furnace cavity and collect the powder. Experimental results showed that the recovered powder mass after pulverization was 30.757 g, and the calculated powder recovery rate was 98.28%. The results indicate that the pulverization and separation effect of the core block did not decrease significantly under the 4 cm zirconium tube condition.

[0062] Experiment Example 4 (UO2 core blocks, five 3cm clad tubes): The experiment used UO2 core blocks as the experimental sample. A total of five zirconium alloy clad tubes, each with an inner diameter of 8.2mm and a length of approximately 3cm, were used to hold 10 UO2 core blocks. The masses of each core block were: 4.9951g, 5.0356g, 5.0213g, 4.8833g, 4.9152g, 5.1023g, 4.9261g, 5.0765g, 4.9907g, and 5.1200g, respectively. The total mass was approximately 50.0661g. After loading the sample, the ends of the tubes were appropriately pinched together to prevent the core blocks from falling off during the powdering process. The experiment was conducted in an air atmosphere, with a heating rate set at 10℃·min. -1 The furnace temperature was raised from room temperature to 500℃ and held for 3 hours; the temperature of the thermocouple resistance wire was approximately 750℃. The rotation speed was 30 r / min. -1 Air flow rate 0.4 L·min -1 After the heat preservation period, the furnace body was tilted and vibrated three times (vibration pressure 0.1 MPa, 1 min each time), then switched to forward rotation to remove the cladding tube from the furnace cavity and collect the powder. Experimental results showed that the total mass of powder recovered after pulverization was 51.263 g, and the powder recovery rate was calculated to be 98.50%. The results indicate that under these conditions, the core block pulverization was sufficient, the separation effect was good, and very little residue remained inside the zirconium tube. This device is capable of pulverization and separation experiments at the 50 g level.

[0063] Comparative Example: Analysis of existing research experiments simulating the oxidation behavior of short segments of spent fuel at 673-873 K is shown to be unsatisfactory. The experimental equipment used in this comparative example has structural flaws, such as the risk of rod jamming between pitches. For instance, using M5 alloy as the cladding, with a cladding length of 32 mm and a diameter of 8.3 mm, and each cladding containing two UO2 pellets (approximately 7 g each, with a height of 12.19-14.73 mm and a diameter of 8.192 ± 0.012 mm), to simulate short segments of spent fuel, a rotary oxidation volatilization device was used at 3 K·min. -1 The temperature was increased at a rate of 673~873K, and 1.5L·min⁻¹ was introduced. -1 Air is used to remove oxidation products in real time. Experimental results show that oxidation at 673K ​​is insufficient, and some cores detach before fully reacting; the conversion rate at 823K is only 86%, and unreacted cores remain inside the shell; sintering of oxidation products at 873K hinders oxygen diffusion, reducing the separation efficiency.

[0064] Comparative analysis shows that the separation device and method of this application can achieve highly efficient separation of spent fuel pellets and cladding, with a separation efficiency of over 99%, significantly higher than the comparative example. Furthermore, the separation device and method of this application ensure thorough separation of spent fuel pellets and cladding, with minimal residue inside the cladding tube and no powder sticking to the wall or causing tube blockage. It can also separate volatile fission products such as tritium, iodine, carbon, krypton, and xenon, greatly reducing the amount of waste generated during spent fuel reprocessing.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A spent fuel pellet and cladding separation device, characterized in that, include: The loading chamber includes a first chamber, a second chamber, and a sieve plate. The first chamber is connected to the second chamber through the sieve plate. The first chamber is connected to a feed inlet, an air inlet, and a shell outlet. The second chamber is connected to a powder outlet and an exhaust outlet. A vibrator is connected to the loading chamber, and the vibrator is used to drive the loading chamber to vibrate; A rotary drive mechanism is connected to the loading chamber. The rotary drive mechanism is used to drive the loading chamber to rotate about the central axis, which is the axis of the loading chamber. A tilting drive mechanism is connected to the loading chamber, and the tilting drive mechanism is used to drive the loading chamber to tilt from one end to the other along the central axis.

2. The spent fuel pellet and cladding separation device according to claim 1, characterized in that, The first cavity is at least partially inserted into the second cavity.

3. The spent fuel pellet and cladding separation device according to claim 2, characterized in that, The loading chamber is provided with a first end and a second end, the first chamber is connected to the first end, and the second chamber is connected to the second end; The sieve plate is configured as the side wall of the first cavity near the end plate; and / or the sieve plate is configured as the end plate of the first cavity.

4. The spent fuel pellet and cladding separation device according to claim 3, characterized in that, The sieve plate has a plurality of sieve holes, each of which is evenly distributed circumferentially along the side wall of the first cavity near the end plate; and / or each of which is distributed at a position near the outer edge of the end plate of the first cavity.

5. The spent fuel pellet and cladding separation device according to claim 3, characterized in that, The loading chamber further includes: A threaded rib is formed on the inner wall of the first cavity, and the threaded rib is located near the first end of the loading cavity; Several baffles are connected to the inner wall of the first cavity, and each baffle is positioned at the location of the sieve plate; each baffle is evenly arranged along the circumference of the first cavity, and each baffle is arranged along the central axis.

6. The spent fuel pellet and cladding separation device according to any one of claims 1-5, characterized in that, The rotary drive mechanism includes: Gear disk, connected to the loading chamber; A rotary drive motor, the output shaft of which is connected to the gear disk via tooth meshing.

7. The spent fuel pellet and cladding separation device according to any one of claims 1-5, characterized in that, The tilting drive mechanism includes: A support platform is provided beneath the loading chamber; The first drive unit is connected to the support platform; A second drive unit is connected to the first drive unit. The second drive unit is equipped with a connecting shaft. The first drive unit is meshed with the connecting shaft through a worm gear transmission mechanism so that the first drive unit can rotate relative to the connecting shaft. The connecting shaft is arranged perpendicular to the central axis of the loading chamber.

8. The spent fuel pellet and cladding separation device according to any one of claims 1-5, characterized in that, It also includes a heating and insulation mechanism, which includes a thermocouple and an insulation layer. The heating and insulation layer is wrapped around the outer wall of the filling chamber, and the thermocouple is disposed between the heating and insulation layer and the outer wall of the filling chamber.

9. The spent fuel pellet and cladding separation device according to any one of claims 1-5, characterized in that, Also includes: A receiving tank with a casing is connected to the casing outlet; A powder receiving container is connected to the powder outlet; The balance is connected to the powder receiving container.

10. A method for separating spent fuel pellets from their cladding, characterized in that, Performed using the spent fuel pellet and cladding separation device as described in any one of claims 1-9; The method for separating spent fuel pellets from their cladding includes: The loading chamber is tilted toward the powder outlet end by a tilting drive mechanism, and the loading chamber is rotated by a rotary drive mechanism. The spent fuel short segments are fed into the first cavity of the charging chamber through the feed port. The spent fuel short segments undergo an oxidation reaction in the first cavity and disintegrate to form a shell and powder. The feeding chamber is driven to vibrate by a vibrator, and the powder enters the second cavity of the feeding chamber through the sieve plate, and all the powder is discharged through the powder outlet; After all the powder has been discharged, the tilting drive mechanism drives the loading chamber to tilt toward the shell outlet end, so that the shell leaves the first chamber through the shell outlet.

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