Phase separation method and device, and extraction separation method and system for spent fuel reprocessing plant

Abstract

The present invention discloses a phase separation method and device, the phase separation method comprises extracting a mixed phase of an organic phase and an aqueous phase obtained after extraction in an extraction and separation process of a spent fuel reprocessing plant, and performing a decantation operation on the mixed phase to separate an organic phase and an aqueous phase; the phase separation device comprises a decantation unit and a conveying mechanism, the decantation unit is connected to an extraction and separation device in the spent fuel reprocessing plant through the conveying mechanism, the conveying mechanism is used to extract the mixed phase of an organic phase and an aqueous phase in the extraction and separation device into the decantation unit, and the decantation unit is used to perform a decantation operation on the mixed phase to separate an organic phase and an aqueous phase. The present invention also discloses an extraction and separation method and system for a spent fuel reprocessing plant. The present invention can avoid the generation of interface contaminants at the phase separation interface in the extraction and separation device, and ensure the operational stability and safety of the extraction and separation device.

Description

Technical Field

[0001] The present invention belongs to the field of nuclear technology, and in particular relates to a phase separation method and device, a spent fuel reprocessing plant extraction and separation method comprising the phase separation method, and a spent fuel reprocessing plant extraction and separation system comprising the phase separation device. Background Art

[0002] The main process of Purex mainly adopts extraction and separation technology, and the extraction column is the key equipment for extraction and separation. The traditional extraction column is generally a pulse extraction column (such as Figure 2 As shown in the figure, it consists of an upper expansion section, a lower expansion section and a plate section, and the organic phase and the aqueous phase are separated in the expansion section. Due to the high radioactive concentration of the feed liquid, during the contact mass transfer process between the two phases, the degradation products of the organic phase, the fission products of the feed liquid and other impurities are very likely to generate interface contaminants at the interface of the phase separation. During long-term operation, interface contaminants will continue to form and accumulate, and may also enter the plate section, making the pulse extraction column unable to continue to operate stably, so that the purification capacity in the later stage of operation drops sharply. At this time, the system needs to be stopped for maintenance, which consumes a lot of manpower and reagents, and may still not meet the maintenance requirements, thus affecting the stability of operation. What is more serious is that fissile nuclides are easily enriched at the interface contaminants, which poses a critical risk and affects the safety of operation. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a phase separation method and device in view of the above-mentioned deficiencies in the prior art, as well as an extraction and separation method for a spent fuel reprocessing plant comprising the above-mentioned phase separation method, and an extraction and separation system for a spent fuel reprocessing plant comprising the above-mentioned phase separation device, which can avoid the generation of interface contaminants at the phase separation interface in the extraction and separation equipment, and ensure the operating stability and safety of the extraction and separation equipment.

[0004] The technical solution of the present invention to solve the above technical problems is:

[0005] According to a first aspect of the present invention, a phase separation method is provided, comprising: extracting a mixed phase of an organic phase and an aqueous phase obtained after extraction in an extraction separation process of a spent fuel reprocessing plant, and performing a decantation operation on the mixed phase to separate the organic phase and the aqueous phase.

[0006] Preferably, the decantation operation specifically includes: passing the mixed phase into a decanter, clarifying and separating the mixed phase in the decanter, obtaining an organic phase at the upper part of the decanter, obtaining an aqueous phase at the lower part of the decanter, and providing a first outlet at the upper part of the decanter, and providing a second outlet at the bottom of the decanter, and connecting a conveying pipeline having an inverted U-shaped pipe segment to the second outlet, and controlling the highest point of the inverted U-shaped pipe segment to be between the first outlet and the two-phase interface of the organic phase and the aqueous phase; and controlling the height of the highest point of the inverted U-shaped pipe segment to discharge the organic phase from the first outlet overflow and discharge the aqueous phase from the conveying pipeline.

[0007] Preferably, the mixed phase of the organic phase and the aqueous phase obtained after extraction in the extraction and separation process of the spent fuel reprocessing plant is extracted by compressed air lifting;

[0008] The method further comprises: before the decantation operation, performing gas-liquid separation on the mixed phase extracted by the compressed air lifting method to remove the compressed air mixed in during the compressed air lifting process.

[0009] According to a second aspect of the present invention, there is provided a phase separation device, comprising a decantation unit and a conveying mechanism, wherein the decantation unit is connected to an extraction and separation device in a spent fuel reprocessing plant via the conveying mechanism, wherein the conveying mechanism is used to extract a mixed phase of an organic phase and an aqueous phase in the extraction and separation device into the decantation unit, and the decantation unit is used to perform a decantation operation on the mixed phase to separate an organic phase and an aqueous phase.

[0010] Preferably, the decantation unit comprises a decanter, a conveying pipeline, and a steam ejector, wherein the decanter is provided with an inlet at the top, a first outlet at the upper part, and a second outlet at the bottom, the inlet being communicated with the outlet of the conveying mechanism for receiving the mixed phase extracted by the conveying mechanism, the second outlet being communicated with the conveying pipeline, and an inverted U-shaped pipe section being provided on the conveying pipeline, the highest point of the U-shaped pipe section being located between the first outlet and the second outlet, so that the mixed phase is clarified and separated in the decanter to obtain an organic phase and an aqueous phase, the aqueous phase is discharged from the conveying pipeline via the second outlet, and the organic phase is discharged via overflow from the first outlet; the suction port of the steam ejector pump is arranged near the interface between the two phases in the decanter, for discharging interface dirt generated at the interface between the two phases.

[0011] Preferably, the height between the highest point of the U-shaped pipe section and the first outlet is:

[0012] h2=h1(ρ 水 -ρ 有 ) / ρ 水

[0013] Wherein, h1 is the height of the two-phase interface between the first outlet and the organic phase and the aqueous phase in the decanter, ρ水 is the density of the water phase, ρ 有 is the density of the organic phase.

[0014] Preferably, the conveying mechanism is an air lift, and the device also includes a gas-liquid separation tank, which is connected to the air lift and the decanter respectively, and is used to perform gas-liquid separation on the mixed phase extracted by the air lift, and convey the mixed phase after gas-liquid separation to the decanter for decantation operation.

[0015] Preferably, the gas-liquid separation tank and the decanter are both located at a height greater than the extraction separation device, and the gas-liquid separation tank is located above the decanter.

[0016] According to a third aspect of the present invention, there is provided an extraction and separation method for a spent fuel reprocessing plant, comprising: introducing a feed liquid from the upper end of an extraction and separation device, introducing an extractant from the lower end of the extraction and separation device, allowing the feed liquid and the extractant to contact and transfer mass in reverse in the extraction and separation device, obtaining an extracted organic phase at the upper part of the extraction and separation device, and obtaining a mixed phase of the extracted organic phase and an aqueous phase at the lower part of the extraction and separation device; and treating the mixed phase using the above-mentioned phase separation method to separate the organic phase and the aqueous phase.

[0017] According to a fourth aspect of the present invention, there is provided an extraction and separation system for a spent fuel reprocessing plant, comprising extraction and separation equipment and the above-mentioned phase separation device, wherein a decanter in the phase separation device is connected to the extraction and separation equipment via a conveying mechanism.

[0018] Beneficial effects:

[0019] The phase separation method and device of the present invention are used in the extraction and separation process of a spent fuel reprocessing plant. By extracting the mixed phase of the organic phase and the aqueous phase in the extraction and separation equipment and performing a decantation operation, the direction of the interface dirt in the extraction and separation equipment is controlled, and the dirt is discharged in a timely or regular manner to prevent the purification capacity from decreasing due to the accumulation of dirt, thereby ensuring the operating stability and safety of the extraction and separation equipment. In addition, the device can realize automatic phase separation by setting an inverted U-shaped pipe section, can achieve maintenance-free by setting an air lift, and can facilitate maintenance by setting the decanter at a high place.

[0020] The extraction and separation method and system of the spent fuel reprocessing plant of the present invention, because the method includes the above-mentioned phase separation method, can extract the mixed phase of the organic phase and the aqueous phase in the extraction and separation equipment and perform a decantation operation, thereby controlling the direction of the interface dirt in the extraction and separation equipment, timely or regularly discharging the dirt, preventing the purification capacity from decreasing due to dirt accumulation, and ensuring the operation stability and safety of the extraction and separation equipment. Because the system includes the above-mentioned phase separation device, it can realize automatic phase separation, can be maintenance-free, can be convenient for staff to perform maintenance, and, compared with the traditional pulse extraction column, the lower expansion section is omitted, which can simplify the structure of the pulse extraction column (extraction and separation equipment). BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the extraction and separation system in an embodiment of the present invention;

[0022] Figure 2 Schematic diagram of the structure of a traditional pulse extraction column.

[0023] In the figure: 1-gas-liquid separation tank; 2-decanter; 3-transport pipeline; 4-air lift; 5-mixed phase outlet; 6-extractant inlet; 7-upper expansion section; 8-organic phase outlet; 9-feed liquid inlet; 10-extraction column plate section; 11-first outlet; 12-second outlet; 13-lower expansion section. DETAILED DESCRIPTION

[0024] The following will be combined with the accompanying drawings in the present invention to clearly and completely describe the technical solutions in the invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention.

[0025] In the description of the present invention, it should be noted that the directions or positional relationships indicated by “upper” and the like are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience and simplification of the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0026] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0027] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connect", "set", "install", "fix" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, an indirect connection through an intermediate medium, or the internal communication of two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] Example 1

[0029] This embodiment discloses a phase separation method, comprising:

[0030] The mixed phase of the organic phase and the aqueous phase obtained after extraction in the extraction and separation process of the spent fuel reprocessing plant is extracted, and the mixed phase is subjected to decantation operation to separate the organic phase and the aqueous phase.

[0031] Specifically, if Figure 1 As shown, the decantation operation specifically includes: passing the mixed phase into the decanter 2. Since the density of the organic phase is small, the density of the aqueous phase is large, and the two are immiscible, the mixed phase is finally clarified and separated in the decanter 2, and the organic phase is obtained at the upper part of the decanter 2, and the aqueous phase is obtained at the lower part of the decanter 2. A first outlet 11 is set at the upper part of the decanter 2, and a second outlet 12 is set at the bottom of the decanter 2. A conveying pipeline 3 with an inverted U-shaped pipe section is connected to the second outlet 12, and the highest point of the inverted U-shaped pipe section is controlled to be between the first outlet 11 and the two-phase interface of the organic phase and the aqueous phase. The two-phase interface is preferably in the upper half of the decanter; the height of the highest point of the inverted U-shaped pipe section is controlled to overflow and discharge the organic phase from the first outlet 11, and discharge the aqueous phase from the conveying pipeline 3 through the second outlet 12.

[0032] In some embodiments, the mixed phase of the organic phase and the aqueous phase obtained after extraction in the extraction and separation process of the spent fuel reprocessing plant can be extracted by compressed air lifting, that is, the mixed phase is extracted by using the air lift 4. Specifically, the compressed air enters the air pipe in the air lift 4 from the side into the liquid riser (also called a gas-liquid mixer) filled with liquid (mixed phase) in the air lift, and is mixed with the liquid by the gas-liquid mixer to form foam. The foamy liquid mixed with compressed air rises along the liquid riser due to the decrease in relative density, and is finally discharged from the upper end outlet of the liquid riser. The air lift 4 is a maintenance-free liquid conveying equipment that can avoid maintenance.

[0033] In some embodiments, the method further comprises:

[0034] Before the decantation operation is performed, the two-phase mixed phase extracted by the compressed air lifting method is first subjected to gas-liquid separation treatment to separate the gas (compressed air) mixed in during the compressed air lifting process.

[0035] The phase separation method of this embodiment is used in the extraction and separation process of a spent fuel reprocessing plant. By extracting the mixed phase of the organic phase and the aqueous phase in the extraction and separation equipment and performing a decantation operation, the direction of the interface dirt in the extraction and separation equipment is controlled, and the dirt is discharged in a timely or regular manner to prevent the purification capacity from decreasing due to the accumulation of dirt, thereby ensuring the operating stability and safety of the extraction and separation equipment.

[0036] Example 2

[0037] This embodiment discloses a phase separation device, including a decantation unit and a conveying mechanism. The decantation unit is connected to an extraction and separation device in a spent fuel reprocessing plant through the conveying mechanism, wherein the conveying mechanism is used to extract a mixed phase of an organic phase and an aqueous phase obtained in an extraction process in the extraction and separation device into the decantation unit, and the decantation unit is used to perform a decantation operation on the mixed phase to separate the organic phase and the aqueous phase.

[0038] In some embodiments, Figure 1 As shown, the decanting unit includes a decanter 2, a delivery pipeline 3, and a steam jet pump (not shown in the figure). The top of the decanter 2 is provided with an inlet, the upper part thereof is provided with a first outlet 11, and the bottom thereof is provided with a second outlet 12, wherein the inlet of the decanter 2 is connected to the outlet of the delivery mechanism, for receiving the mixed phase extracted by the delivery mechanism, the second outlet 12 of the decanter 2 is connected to one end of the delivery pipeline 3, the other end of the delivery pipeline 3 is connected to the water phase storage tank, and an inverted U-shaped pipe section is provided on the delivery pipeline 3, the highest point of the inverted U-shaped pipe section is located between the first outlet 11 and the second outlet 12, so that the mixed phase is clarified and separated in the decanter 2 to obtain an organic phase and an aqueous phase, and the height of the highest point of the U-shaped pipe section is controlled to be between the first outlet 11 and the two-phase interface of the organic phase and the aqueous phase, wherein the two-phase interface is preferably located in the upper half of the decanter, so that the aqueous phase is discharged from the delivery pipeline 3 to the water phase storage tank through the second outlet 12, and the organic phase is discharged through the overflow of the first outlet 11. The suction port of the steam jet pump is arranged near the interface between the two phases in the decanter, and is used to discharge the interface dirt generated at the interface between the two phases.

[0039] In this embodiment, in order to facilitate clarification and phase separation, the decanter 2 is preferably a slender conical container, and the first outlet 11 is connected to an organic phase delivery pipeline, which is connected to an organic phase storage tank to transport the overflow of the organic phase separated in the decanter to the organic phase storage tank.

[0040] In some embodiments, the height between the highest point of the U-shaped pipe section and the first outlet 11 is:

[0041] h2=h1(ρ 水 -ρ 有 ) / ρ 水

[0042] Wherein, h1 is the height of the two-phase interface between the first outlet 11 and the organic phase and the aqueous phase in the decanter 2, and ρ 水 is the density of the water phase, ρ 有 is the density of the organic phase.

[0043] In this embodiment, by setting a U-shaped pipe section and strictly controlling the height of h2, the position of the two-phase interface in the decanter can be controlled, so that the two-phase interface of the organic phase and the aqueous phase is located in the decanter, so that the steam jet pump can discharge interface dirt.

[0044] In some embodiments, the conveying mechanism is an air lift 4, and the mixed phase in the extraction and separation equipment is extracted by the air lift in a compressed air lifting manner and conveyed to the decanter. The air lift 4 is a maintenance-free liquid conveying device, which can avoid maintenance. The device also includes a gas-liquid separation tank 1, which is connected to the air lift 4 and the decanter 2 respectively, and is used to perform gas-liquid separation on the mixed phase extracted by the air lift to remove the compressed air mixed in when the air lift 4 conveys the mixed phase, and convey the mixed phase after gas-liquid separation to the decanter for decantation operation.

[0045] Specifically, the gas-liquid separation tank 1 is preferably an elongated conical container, which is arranged above the decanter. An inlet is provided at the upper part of the gas-liquid separation tank 1, and the inlet is connected to the outlet of the air lift. A sieve plate (not shown in the figure) is provided inside the gas-liquid separation tank, and the sieve plate is located below the inlet of the gas-liquid separation tank 1. After the mixed phase enters the gas-liquid separation tank 1, the liquid phase sinks through the sieve plate under the action of its own gravity, thereby separating the gas (i.e., compressed air). An air outlet is provided at the top of the gas-liquid separation tank 1 for discharging the separated compressed air. A liquid outlet is provided at the bottom of the gas-liquid separation tank 1 for discharging the two-phase mixed phase after the air is separated to the decanter, and an inclined baffle (not shown in the figure) is provided on the liquid outlet to prevent the mixed phase after the compressed air is separated from disturbing the liquid in the decanter.

[0046] In this embodiment, the heights of the gas-liquid separation tank 1 and the decanter 2 are both greater than the height of the extraction and separation equipment, and the gas-liquid separation tank 1 is located above the decanter 4. The mixed phase after gas-liquid separation can automatically flow into the decanter 2 by gravity, without consuming energy, and can facilitate maintenance operations by staff.

[0047] The phase separation device of this embodiment is used in the extraction and separation process of the spent fuel reprocessing plant. It can extract the mixed phase of the organic phase and the aqueous phase in the extraction and separation equipment and perform a decantation operation, thereby controlling the direction of the dirt at the interface between the two phases in the extraction and separation equipment, discharging the dirt in a timely or regular manner, preventing the purification capacity from decreasing due to the accumulation of dirt, and ensuring the operating stability and safety of the extraction and separation equipment. In addition, by setting an inverted U-shaped pipe section, automatic phase separation can be achieved; by setting an air lift, maintenance-free can be achieved; by setting the decanter at a high place, it is convenient for staff to perform maintenance.

[0048] Example 3

[0049] This embodiment discloses an extraction and separation method for a spent fuel reprocessing plant, comprising:

[0050] A feed liquid (e.g., a uranium-plutonium feed liquid in a spent fuel reprocessing plant) is introduced from the upper end of an extraction and separation device, and an extractant (e.g., 30% TBP-kerosene) is introduced from the lower end of the extraction and separation device, so that the feed liquid and the extractant are in reverse contact and mass transfer in the extraction and separation device, an organic phase after extraction is obtained at the upper part of the extraction and separation device, and a mixed phase of the organic phase after extraction and water phase is obtained at the lower part of the extraction and separation device;

[0051] The mixed phase at the bottom of the extraction column plate section in the extraction separation device was treated by the phase separation method described in Example 1, and finally clarified and separated in a decanter to obtain an organic phase and an aqueous phase.

[0052] The spent fuel reprocessing plant extraction and separation method of this embodiment includes the phase separation method described in Example 1, and can extract the mixed phase at the bottom of the extraction column plate section in the extraction and separation equipment and perform a decantation operation, thereby controlling the direction of the interface dirt in the extraction and separation equipment, discharging the dirt in a timely or regular manner, preventing the purification capacity from decreasing due to the accumulation of dirt, and ensuring the operation stability and safety of the extraction and separation equipment.

[0053] Example 4

[0054] This embodiment discloses an extraction and separation system for a spent fuel reprocessing plant, including extraction and separation equipment and the phase separation device described in Example 2, wherein the decanter in the phase separation device is connected to the extraction and separation equipment via a conveying mechanism.

[0055] Specifically, the extraction and separation device is a pulse extraction column (e.g., a 1AX extraction column into which the extractant can be continuously introduced). However, the structure of the pulse extraction column is different from that of the conventional pulse extraction column. The pulse extraction column includes an upper expansion section 7 and an extraction column plate section 10 (the conventional pulse extraction column also includes a lower expansion section 13, e.g., Figure 2As shown), the upper expansion section 7 is connected to the extraction column plate section 10 and is located at the top of the extraction column plate section 10. A feed liquid inlet 9 and an organic phase outlet 8 are provided on the upper expansion section 7. The feed liquid inlet 9 is used to introduce the feed liquid. The height of the organic phase outlet 8 is higher than the height of the feed liquid inlet, and is used to discharge the organic phase obtained after extraction. An extractant inlet 6 and a mixed phase outlet 5 are provided at the lower part of the extraction column plate section 10, wherein the extractant inlet 6 is used to introduce the extractant, and the feed liquid introduced by the feed liquid inlet 9 and the extractant introduced by the extractant inlet 6 are in reverse contact in the extraction column plate section 10, uniformly mixed, and mass transfer is performed, thereby realizing extraction and separation to obtain an organic phase and an aqueous phase, wherein the organic phase is at the upper part of the pulse extraction column, and the aqueous phase is at the lower part of the pulse extraction column; the mixed phase outlet 5 is preferably located below the extractant inlet 6, and is used to connect a conveying mechanism to extract the aqueous phase and the organic phase mixed phase through the conveying mechanism. It should be noted that Ideally, the mixed phase extracted from the mixed phase outlet 5 is a two-phase mixture at the interface between the aqueous phase and the organic phase. However, in actual operation, since the mixed phase outlet 5 is arranged at the lower part of the extraction column plate section 10, the mixed phase outlet 5 also has the function of discharging the aqueous phase, and some of the extractant that does not participate in the extraction process will also be extracted together with the mixed phase. That is to say, the liquid phase extracted from the mixed phase outlet 5 includes not only the two-phase mixture at the interface between the organic phase and the aqueous phase, but also the aqueous phase obtained after extraction and some of the extractant that does not participate in the extraction process.

[0056] The working process of the spent fuel reprocessing plant extraction and separation system of this embodiment is described in detail below, as follows:

[0057] A feed liquid containing uranium and plutonium is introduced from the feed liquid inlet 9, and an extractant is introduced from the extractant inlet 6. The two are contacted and mixed in reverse direction in the extraction column plate section 10 and mass transfer is performed. An organic phase containing uranium and plutonium is obtained at the upper part of the extraction column plate section 10. The organic phase is finally discharged through the organic phase outlet 8 on the upper expansion section 7, and an aqueous phase is obtained at the lower part of the extraction column plate section 10.

[0058] At the same time, the air lift 4 is started to extract the water phase at the bottom of the extraction column plate section 10, the two-phase mixture at the junction of the water phase and the organic phase, and part of the extractant that does not participate in the extraction process and transport them to the gas-liquid separation tank 1 for gas-liquid separation, and the separated liquid is discharged into the decanter 2. Due to the different densities of the organic phase and the water phase, under the action of gravity, the organic phase and the water phase in the liquid are clarified and separated in the decanter 2. The organic phase is in the upper layer and overflows through the first outlet 11 to be discharged to the organic phase storage tank, and the water phase is in the lower layer and is discharged to the water phase storage tank through the second outlet 12;

[0059] During this period, the interfacial dirt generated at the interface between the organic phase and the aqueous phase in the decanter 2 is observed or detected. When the interfacial dirt in the decanter 2 accumulates to a certain amount (which can be obtained by detecting the density change in the decanter 2), it is discharged using a steam jet pump.

[0060] The spent fuel reprocessing plant extraction and separation system of this embodiment includes the phase separation device described in Example 2, which can extract the mixed phase of the organic phase and the aqueous phase in the extraction and separation equipment and perform a decantation operation, thereby controlling the direction of the interface dirt in the extraction and separation equipment, discharging the dirt in a timely or regular manner, preventing the purification capacity from decreasing due to the accumulation of dirt, and ensuring the operational stability and safety of the extraction and separation equipment. In addition, compared with the traditional pulse extraction column, the lower expansion section is omitted, which can simplify the structure of the pulse extraction column (extraction and separation equipment).

[0061] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A phase separation method, comprising: Extracting a mixed phase of an organic phase and an aqueous phase obtained after extraction in an extraction and separation process of a spent fuel reprocessing plant, and performing a decantation operation on the mixed phase to separate an organic phase and an aqueous phase, wherein the decantation operation specifically comprises: introducing the mixed phase into a decanter, allowing the mixed phase to be clarified and separated in the decanter, obtaining an organic phase at the upper part of the decanter, and obtaining an aqueous phase at the lower part of the decanter, and providing a first outlet at the upper part of the decanter, and providing a second outlet at the bottom of the decanter, and connecting a conveying pipeline having an inverted U-shaped pipe section to the second outlet, controlling the highest point of the inverted U-shaped pipe section to be between the first outlet and the two-phase interface of the organic phase and the aqueous phase, and controlling the height of the highest point of the inverted U-shaped pipe section to overflow and discharge the organic phase from the first outlet, and to discharge the aqueous phase from the conveying pipeline; During the process, the interface dirt generated at the interface between the organic phase and the aqueous phase in the decanter is observed or detected. When the interface dirt in the decanter accumulates to a certain amount, it is discharged using a steam jet pump.

2. The phase separation method according to claim 1, characterized in that: The mixed phase of organic phase and aqueous phase obtained after extraction in the extraction and separation process of the spent fuel reprocessing plant is extracted by compressed air lifting; The method further comprises: before the decantation operation, performing gas-liquid separation on the mixed phase extracted by the compressed air lifting method to remove the compressed air mixed in during the compressed air lifting process.

3. A phase separation device, characterized in that: It includes a decanting unit and a conveying mechanism. The decantation unit is connected to the extraction and separation equipment in the spent fuel reprocessing plant through the conveying mechanism, wherein the conveying mechanism is used to extract the mixed phase of the organic phase and the aqueous phase in the extraction and separation equipment into the decantation unit, and the decantation unit is used to perform a decantation operation on the mixed phase to separate the organic phase and the aqueous phase; The decanting unit comprises a decanter, a transfer line, and a steam ejector. The decanter is provided with an inlet at the top, a first outlet at the upper part, and a second outlet at the bottom. The inlet is connected to the outlet of the conveying mechanism and is used to receive the mixed phase extracted by the conveying mechanism. The second outlet is connected to the conveying pipeline, and an inverted U-shaped pipe section is provided on the conveying pipeline. The highest point of the U-shaped pipe section is between the first outlet and the second outlet, so that the mixed phase is clarified and separated in the decanter to obtain an organic phase and an aqueous phase. The aqueous phase is discharged from the conveying pipeline through the second outlet, and the organic phase is discharged through the overflow of the first outlet. The suction port of the steam jet pump is arranged near the interface between the two phases in the decanter, and is used to discharge interface dirt generated at the interface between the two phases.

4. The phase separation device according to claim 3, characterized in that: The height between the highest point of the U-shaped pipe section and the first outlet is: h2=h1(ρ 水 -r 有 ) / p 水 Wherein, h1 is the height of the two-phase interface between the first outlet and the organic phase and the aqueous phase in the decanter, ρ 水 is the density of the water phase, ρ 有 is the density of the organic phase.

5. The phase separation device according to claim 3, characterized in that: The conveying mechanism is an air lift, and the device also includes a gas-liquid separation tank. The gas-liquid separation tank is connected to the air lift and the decanter respectively, and is used to perform gas-liquid separation on the mixed phase extracted from the air lift, and transport the mixed phase after gas-liquid separation to the decanter for decantation operation.

6. The phase separation device according to claim 5, characterized in that: The heights of the gas-liquid separation tank and the decanter are both greater than the height of the extraction and separation equipment, and the gas-liquid separation tank is located above the decanter.

7. A method for extraction and separation in a spent fuel reprocessing plant, comprising: The feed liquid is introduced from the upper end of the extraction and separation device, and the extractant is introduced from the lower end of the extraction and separation device, so that the feed liquid and the extractant are in reverse contact and mass transfer in the extraction and separation device, and an organic phase after extraction is obtained at the upper part of the extraction and separation device, and a mixed phase of the organic phase after extraction and water phase is obtained at the lower part of the extraction and separation device; The mixed phase is treated by the phase separation method according to any one of claims 1 to 2 to separate the organic phase and the aqueous phase.

8. A spent fuel reprocessing plant extraction and separation system, comprising extraction and separation equipment, characterized in that: It also comprises the phase separation device according to any one of claims 3 to 6, wherein the decanter in the phase separation device is connected to the extraction and separation equipment via a conveying mechanism.

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