System for extracting UF6 from a UF6 container and corresponding method

Abstract

The present invention relates to a system (1) for extracting UF6 from a UF6 container placed in an autoclave (5), comprising a pump (24) having an inlet port (26) being connected to an upstream supply circuit (10, 20), the upstream supply circuit (10, 20) transporting UF6 from the autoclave to the pump (24); wherein the system further comprises a temperature- controlled subsystem (3) providing a heat supply to the pump (24) and at least a downstream portion of the upstream supply circuit (10, 20), the temperature-controlled subsystem (3) heat supply being adapted to maintain a temperature within the upstream supply circuit and the pump (24) during operation such that said temperature is above the crystallization temperature of UF6.

Description

[0001] System for extracting UF6 from a UF6 container and corresponding method

[0002] The present invention concerns a system for extracting UF6 from a UF6 container. In addition, the present invention relates to a conversion installation for converting UF6 into UO2.

[0003] Further, the present invention relates to a method for emptying UF6 from a UF6 container.

[0004] This emptying process of residual UF6 in UF6 container takes place within the field of the production of uranium dioxide (UO2) powder, intended in particular for the manufacture of UO2 pellets for nuclear fuel rods.

[0005] KR102075649 B1 discloses a uranium hexafluoride vaporization system, which prevents workers from being exposed to UF6 gas in advance. The uranium hexafluoride vaporization system comprises: a vaporizer having an internal space of a constant volume; a cylinder arranged inside the vaporizer and vaporizing solid UF6; a cylinder valve provided on one side of the cylinder to open and close the cylinder, and discharging gas UF6 to the outside of the cylinder.

[0006] JPS6374918 A relates to the pumping of residual UF6 from a UF6 cylinder. The gas is sucked into a hydrolysis column through a suction nozzle.

[0007] EP048095 B1 discloses a pump for heavy gases like UF6.

[0008] EP3864675 B1 discloses an installation for converting uranium hexafluoride, UF6, to uranium dioxide, UO2, based on a UF6 container placed in an autoclave and a supply circuit configured to supply a reactor with UF6 in gaseous for conversion of UF6 into UO2. Such installation comprises a pumping circuit in parallel of the supply circuit, comprising a pump that is activated when the pressure in the UF6 container is insufficient to ensure the UF6 gas circulation toward the reactor.

[0009] For purpose of better nuclear material management, it is needed to improve the performance of emptying the UF6 container. It is an aim of the present invention to provide a pumping circuit that answers the need of better performance in emptying the UF6 container.

[0010] Object of the invention is to provide an efficient pumping circuit for evacuating residual UF6 from UF6 cylinders.

[0011] According to one aspect, a system is provided for extracting UF6 from a UF6 container placed in an autoclave, comprising a pump having an inlet port being connected to an upstream supply circuit, the upstream supply circuit transporting UF6 from the autoclave to the pump; wherein the system further comprises a temperature-controlled subsystem providing a heat supply to the pump and at least a downstream portion of the upstream supply circuit, the temperature-controlled subsystem heat supply being adapted to maintain a temperature within the upstream supply circuit and the pump during operation such that said temperature is above the crystallization temperature of UF6.

[0012] Further embodiments may relate to one or more of the following features, which may be combined in any technical feasible combination: the system further comprises a motor for driving the pump, wherein the pump has a pump shaft and the motor has a motor shaft, wherein the motor shaft is operatively coupled to the pump shaft, such that the motor drives the pump and the motor is arranged outside the temperature-controlled subsystem;

[0013] - the pump is a scroll pump; the temperature-controlled subsystem is a housing surrounding at least a downstream portion of the upstream supply circuit, and the pump, and having an internal space defining a zone of controlled temperature; the motor shaft is connected via at least one metal bellow connection to the pump shaft; the system further comprising a connecting shaft, the connecting shaft couples the motor shaft to the pump shaft; the motor shaft is coupled via a first metal bellow connection to the connecting shaft and the connecting shaft is coupled via a second metal bellow connection to the pump shaft; the motor shaft, the pump shaft or the connecting shaft traverses a wall of the housing; the pump shaft includes bearings, in particular ball bearings, wherein the bearings of the scroll pump shaft are heat resistant, in particular for a temperature between 80 and 150 degrees Celsius; the lubricant of the bearings of the pump is heat resistant, in particular for a temperature between 80 and 150 degrees Celsius; the pump includes a pressure sensor for detecting leaks within the pump; the system further comprising a bypass fluid circuit the bypass fluid circuit being adapted to bypass the pump, the temperature-controlled subsystem providing a heat supply to the bypass fluid circuit adapted to maintain a temperature within the bypass fluid circuit during operation such that said temperature is above the crystallization temperature of UF6; and / or

[0014] - the bypass circuit, the upstream supply circuit and the pump are provided in a common temperature-controlled subsystem, in particular in a common housing. According to another aspect, a conversion installation is provided for converting UF6 into UO2, the conversion installation being feed with gaseous UF6 by a system according to an embodiment disclosed herein.

[0015] According to a further aspect, a method is provided for emptying UF6 from a UF6 container with a system according to an embodiment disclosed herein, the method comprising: placing the UF6 container in the autoclave, heating the UF6 container in the autoclave; activating the pump.

[0016] Further embodiments may relate to one or more of the following features, which may be combined in any technical feasible combination: the pump is activated, when the pressure in the UF6 container is below 2000 mbar, in particular below 1800 mbar and, in particular, the pump remains activated at least until the pressure in the UF6 container is lower than 100 mbar.

[0017] Further advantages, features, aspects and details are evident from the dependent claims, the description and the drawings.

[0018] The accompanying drawings relate to embodiments of the invention and are described in the following:

[0019] Fig. 1 shows schematically a system according to an embodiment;

[0020] Fig. 2 shows schematically the connection between the motor and the pump according to an embodiment;

[0021] Fig. 3 shows a partial cross sectional view of a scroll pump; and

[0022] Fig. 4 shows schematically a system according to another embodiment.

[0023] It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0024] It is contemplated that elements of one embodiment may be advantageously utilized in other embodiments without further recitation.

[0025] UF6 (Uranium Hexafluoride) cylinders are specialized containers used to store and transport uranium hexafluoride.

[0026] Empting UF6 containers, in particular UP6 cylinders, requires careful consideration of safety protocols due to the hazardous nature of the substance.

[0027] Usually, the UF6 is provided in solid form in the UF6 containers.

[0028] Fig. 1 shows schematically a system 1 according to an embodiment. The UF6 container 7 to be emptied is provided in an autoclave 5. The UF6 containers 7 are emptied by heating them in the autoclave 5, in order to transform the UF6 from a solid form into a gaseous form. The gaseous UF6 is transported by the system 1 to a treatment device 50 for UF6. The treatment device 50 converts for example the UF6 into UO2. In other words, the treatment device 50 is a conversion installation. The conversion installation may be the one described in EP3864675 B1.

[0029] For example, gaseous UF6 from a system 1 according to an embodiment disclosed herein, dry water vapor and H2 (hydrogen) is provided to the conversion installation 50. In a first step UF6 and the dry water vapor reacts in a reactor for creating IIO2F2. In a next step, the IIO2F2 is converted in an oven into UO2 powder by the reaction of the IIO2F2 with dry water vapor and H2. The UO2 power may be used to produce fuel pellets for a nuclear power plant.

[0030] In other words, the conversion installation 50 being feed with gaseous UF6 by the system 1. In some embodiments, a production installation may include the conversion installation and the system 1.

[0031] The system 1 according to the invention includes a pump 24. The pump 24 has an inlet port 26 and an outlet port 28. The inlet port 26 being connected to an upstream supply circuit 10, for example in form of a tubing, connecting the UF6 container 7 to the inlet port 26.

[0032] The outlet port 28 of the pump 24 being connected to a downstream fluid circuit 11 , for example a tubing. The downstream fluid circuit 11 connects the outlet port 28 to the treatment device 50 that needs to be fed with the gaseous UF6.

[0033] Upon activation of the pump 24, the gaseous UF6 is forced from the UF6 container to the treatment device 50.

[0034] In Fig. 1 , the system 1 includes a temperature-controlled subsystem 3 providing a heat supply to at least a downstream portion of the upstream supply circuit 10 and / or the pump 24 and / or at least a upstream portion of the downstream fluid circuit 11 so that the temperature of the gaseous UF6 circulating in the upstream supply circuit 10, the pump 24 and the downstream fluid circuit 11 is above the crystallization temperature of the UF6. The heat supply can be done through convection or radiation or a combination of convection and radiation. For example, the temperature-controlled subsystem 3 can be configured to deliver a heat supply that generate a temperature between 80°C and 150°C, in particular between 90°C and 120°C in the immediate vicinity of the at least downstream portion of the upstream supply circuit 10, and / or the pump 24 and / or the at least upstream portion of the downstream fluid circuit 11 .

[0035] The system further includes a motor 34, in particular an electric motor, for driving the pump 24. The motor 34 is mechanically coupled to the pump 24. The motor 34 is arranged outside the temperature-controlled subsystem 3. Therefore, the motor 34 is not exposed to the heat supply.

[0036] In an embodiment of the invention, the temperature-controlled subsystem 3 is a housing 3 defining a zone of controlled temperature 8 surrounding at least a downstream portion of the upstream supply circuit 10, the pump 24 and at least a upstream portion of the downstream fluid circuit 11 , in the internal volume defined by the housing 3. For example, the housing 3 surrounds at least the majority of the upstream supply circuit 10 and / or at least the majority of the downstream supply circuit 11 .

[0037] The housing 3 is adapted to maintain the gaseous UF6 circulating within the system 1 above the crystallization temperature of UF6.

[0038] As stated, during operation, the zone of controlled temperature 8 has a temperature between 80°C and 150°C, in particular between 90°C and 120°C. For example, in an embodiment, the system 1 may include a controller for controlling the temperature. The controller is operationally connected to a heat source, in particular for the heat supply.

[0039] As it can be seen from Fig. 1 , the system further includes a motor 34, in particular an electric motor, for driving the pump 24. The motor 34 is mechanically coupled to the pump 24. The motor 34 is arranged outside the housing 3 or the zone of controlled temperature. Therefore, the motor 34 is not exposed to the heat inside the housing 3 or the zone of controlled temperature 8. Thus, the pump 24 is not driven by a motor provided inside the housing 3.

[0040] Fig. 2 shows schematically the connection between the motor 34 and the pump 24 according to an embodiment. As it can be seen from Fig. 3, a wall 36 of the housing 3 separates pump 24 from the motor 34. The wall 36 is insulating the motor 34 from the heat inside the housing 3.

[0041] The pump 24 has a pump shaft 38. The pump shaft 38 is provided with heat resistant bearings, in particular heat resistant ball bearings, for example heat resistant grooved ball bearings. For example, a heat resistant lubricant (grease) is used for that purpose. The heat resistant lubricant is adapted to support the temperatures inside the housing 3 and / or the zone of controlled temperature 8.

[0042] The motor 34 has a motor shaft 40. The motor shaft 40 is operatively coupled to the pump shaft 38, so that a rotation of motor shaft 40 causes a rotation of the pump shaft 38.

[0043] According to an embodiment, the motor shaft is coupled with at least one metal bellow connection 42, 44 to the pump shaft 38.

[0044] In an embodiment, a connecting shaft 46 is used to couple the motor shaft 40 to the pump shaft 38. The connecting shaft 46 traverses the wall 36 of the housing 3, in particular in a substantial orthogonal direction with respect to the wall plane. The motor shaft 40 is coupled via a first metal bellow connection 42 to the connecting shaft 46 and the connecting shaft 46 is coupled with a second metal bellow connection 44 to the pump shaft 38. In other embodiments, the system may have more or less connecting shafts 46. For example, the motor shaft 40 or the scroll pump shaft 38 may traverse the wall 36 and connect to each other.

[0045] This arrangement allows an easy maintenance of the system.

[0046] In an embodiment, the motor shaft 40 and the pump shaft 38 are provided as a single, common shaft 48, for example as shown in Fig. 1. In such a case, the common shaft 48 traverses the wall 34 of the housing 3. In a preferred embodiment, the pump 24 is a scroll pump. A scroll pump 24 is also called a scroll compressor or spiral compressor.

[0047] Fig. 3 shows more details of the scroll pump 24. The scroll pump 24 is a displacement pump. The scroll pump 24 uses two interleaving scroll units 30. A scroll unit 30 is a spiralshaped component. One of the scroll units 30 is fixed, whereas the other scroll unit 30 is eccentrically mounted and rotatable, such that it rotates in a circular way around the fixed scroll unit 30. When the rotatable scroll unit rotates, a fluid is moved from the exterior to the interior.

[0048] Further, the pump 24 includes a pressure sensor monitoring a space 32 within the scroll pump 24. The sensor is adapted to monitor the joints, in particular whether there is a leakage.

[0049] The pump shaft 38 is fixed to the rotatable scroll of the scroll pump 24, so that a rotation of the pump shaft 38 rotates the rotatable scroll.

[0050] Fig. 4 discloses another embodiment of a system T according to the invention. The same reference signs designate the same features as in the preceding embodiments. The features of the previous embodiments may be combined with the features of the embodiment of Fig. 4, in particular the use of the system T for a treatment device 50, like a conversion installation, and the pump 24 as described with respect to Figures 1 to 3.

[0051] The system T includes the pump 24. The pump 24 has an inlet port 26 and an outlet port 28. The inlet port 26 being connected to an upstream supply circuit 10, 20 for example in form of a tubing, connecting the UF6 container 7 to the inlet port 26.

[0052] The outlet port 28 of the pump 24 being connected to a downstream circuit 21 , for example a tubing. The downstream circuit 21 connects the outlet port 28 of the pump 24 to a treatment device 50 that needs to be fed with the gaseous UF6.

[0053] The system T includes a temperature-controlled subsystem providing a zone of controlled temperature where the temperature of the gaseous UF6 circulating in the upstream supply circuit 10, 20 the pump 24 and the downstream circuit 21 is above the crystallization temperature of the UF6. For example, the temperature of the zone of controlled temperature is between 80°C and 150°C, in particular between 90°C and 120°C.

[0054] In Fig. 4, for illustration purpose, the temperature-controlled subsystem is a housing 3 surrounding at least a downstream part of the upstream supply circuit 10, the pump 24 and at least a upstream part of the downstream circuit 21. The zone of controlled temperature 8 being the internal volume defined by the housing 3.

[0055] The housing 3 further includes a bypass fluid circuit 16, which includes a first valve 18. The bypass fluid is adapted to transport UF6 directly from the UF6 container 7 to the treatment device, in particular without passing via the pump 24.

[0056] In the embodiment shown in Fig. 4, the upstream supply circuit 20 includes a second valve 22.

[0057] Thus, the UF6 vapor can be directed via the bypass circuit 16 or via the upstream supply circuit 10, 20, the pump 24 and the downstream fluid circuit 21 from the UF6 container to the treatment device 50. Thus, both the bypass circuit 16, the supply circuit 10, 20, in particular the downstream fluid circuit, and the pump 24 are provided in a common housing 3. Thus, the bypass circuit 16 is part of the temperature-controlled subsystem.

[0058] In an embodiment, the bypass circuit is connected at its upstream end to the upstream supply circuit 10, 20 and at its downstream end to the downstream fluid circuit 21. Thus, in the example shown in Figure 4, the entire bypass circuit 16 is arranged in the housing 3.

[0059] According to embodiments, either the first valve 18 or the second valve 22 is open. Alternatively both valves 18, 22 are closed. In an embodiment, the system T only includes the first valve 18.

[0060] During operation, after the UF6 container are placed in the autoclave 5, the UF6 containers are heated to evaporate the UF6, in order to supply the treatment device 50 with gaseous UF6. For example, the autoclave 5 is adapted to heat the UF6 container 7 to a temperature above 75°C, in particular above 95°C.

[0061] Then, in case of the embodiment of Fig. 4, the first valve 18 is opened. The UF6 gas is directed, through the housing 3, via the bypass circuit 16 to the treatment device 50. In this case, the pump 24 is not activated. Thus, the UF6 is transported passively and directly to the treatment device 50 via the system T, in particular via the bypass circuit 16.

[0062] In case the pressure in the UF6 container falls below 2000 mbar, in particular below 1800 mbar, the first valve 18 is closed and, if it is provided in the system T, the second valve 22 is opened. Then, the pump 24 is activated by activating the motor 34. The UF6 is therefore pumped via the upstream supply circuit, the pump 24 and the downstream fluid circuit 21 towards the treatment device 50. In the embodiment of Figure 1 , the pump 24 is activated after the UF6 container 7 is heated up in the autoclave 5. In other words, the gaseous UF6 is transported actively by the system 1 , 1 ’ to the treatment device 50.

[0063] Optionally, the pump 24 remains activated at least until the pressure in the UF6 container is lower than 100 mbar.

[0064] According to embodiments, the pump 24 is adapted to generate a final pressure of less than 100 mbar. Further, the debit rate of the pump 24 is sufficiently high in order to assure a nearly complete removal of the UF6 form the UF6 container.

[0065] The temperature-controlled subsystem 3 described as a housing 3 above may be realized according to alternative principles.

[0066] In an embodiment, temperature-controlled subsystem 3 is a hot box. A hot box includes a hollow casing containing at least partially the upstream supply circuit 10, 20 and the pump 24. A hot box may further include circulating heat transfer fluids that regulate the temperature by flowing around or alongside the upstream supply circuit 10, 20 and the pump 24. The hot box may further include at least partially the downstream fluid circuit 11 , 21 and / or the bypass fluid circuit 16. Further, the heat transfer fluids may circulate around the downstream fluid circuit 11 , 21 and / or the bypass fluid circuit 16. For example, the controller described above may control the circulation and the heat of the heat transfer fluids. The heat transfer fluid is then the heat source.

[0067] In other embodiments, which may be combined with other embodiments disclosed herein, the temperature-controlled subsystem 3 is insulating materials surrounding the upstream supply circuit 10, 20 and the pump 24, for example coatings, wraps, or liners, that minimize the transfer of heat between the inside of the upstream supply circuit and / or the pump 24 and its environment. Further, the insulating materials may surround the downstream fluid circuit 11 , 21 and / or the bypass fluid circuit 16.

[0068] In some embodiments, which may be combined with other embodiments disclosed herein, the temperature-controlled subsystem 3 is a double-wall or double-envelope systems that create a space around the upstream supply circuit 10, 20 and the pump 24, and optionally the downstream fluid circuit 11 , 21 and / or the bypass fluid circuit 16. A heated medium circulates in the double-envelope system to heat the upstream supply circuits 10, 20 and the pump 24, and optionally the downstream fluid circuit 11 , 21 and / or the bypass fluid circuit 16. In this case, the heated medium corresponds to the heat source.

[0069] In other embodiments, which may be combined with other embodiments disclosed herein, the temperature-controlled subsystem 3 is heating elements in form of cables or tapes surrounding or wrapped around the upstream supply circuit 10, 20 and the pump 24 that provides heat to the upstream supply circuit 10, 20 and the pump 24, and optionally the downstream fluid circuit 11 , 21 and / or the bypass fluid circuit 16. For example, the heating elements may be electric heating elements. In an embodiment, the heating elements are controlled by at least one external power source, which is controlled by the controller. In such a case, the electric heating elements are a heat source.

[0070] As it can be seen, the heat source is not the gaseous UF6 circulating in the upstream supply circuit 10, 20, the pump 24, the downstream fluid circuit 11 , 21 and / or the bypass fluid circuit 16. The heat source is provided outside the upstream supply circuit 10, 20, the pump 24, the downstream fluid circuit 11 , 21 and / or the bypass fluid circuit 16, and, in particular, inside the housing 3.

[0071] List of reference signs:

[0072] 1 , T System

[0073] 3 housing

[0074] 5 autoclave

[0075] 7 UF6 container

[0076] 8 zone of controlled temperature

[0077] 10 Tubing

[0078] 11 T ubing, downstream fluid circuit

[0079] 12 outlet port

[0080] 16 bypass fluid circuit

[0081] 18 valve

[0082] 20 upstream supply circuit

[0083] 21 downstream fluid circuit

[0084] 22 valve

[0085] 24 pump

[0086] 26 inlet port

[0087] 28 outlet port

[0088] 30 scroll unit

[0089] 32 space

[0090] 34 motor

[0091] 36 wall

[0092] 38 scroll pump shaft

[0093] 40 motor shaft

[0094] 42 metal bellow connection

[0095] 44 metal bellow connection

[0096] 46 connecting shaft

[0097] 48 common shaft 50 treatment device

Claims

AMENDED CLAIMS received by the International Bureau on 11 March 2026 (11.03.2026)1. System (1) for extracting UF6 from a UF6 container placed in an autoclave (5), comprising a pump (24) having an inlet port (26) being connected to an upstream supply circuit (10, 20), the upstream supply circuit (10, 20) adapted to transport UF6 from the autoclave to the pump (24); characterized in that the system further comprises a temperature-controlled subsystem (3) providing a heat supply to the pump (24) and at least a downstream portion of the upstream supply circuit (10, 20), the temperature- controlled subsystem (3) heat supply being adapted to maintain a temperature within the upstream supply circuit and the pump (24) during operation such that said temperature is above the crystallization temperature of UF6.

2. System (1) according to claim 1 , wherein the pump (24) is a scroll pump.

3. System (1) according to any claims 1 to 2 wherein the temperature-controlled subsystem (3) is a housing (3) surrounding at least a downstream portion of the upstream supply circuit (10, 20), and the pump, and having an internal space defining a zone of controlled temperature (8).

4. System (1) according to any one of the claims 1 to 3, wherein the system further comprises a motor (34) for driving the pump (24), wherein the pump (24) has a pump shaft (38) and the motor (34) has a motor shaft (40), wherein the motor shaft (40) is operatively coupled to the pump shaft (38), such that the motor (34) drives the pump and the motor (34) is arranged outside the temperature-controlled subsystem (3).

5. The system according to claim 4, wherein the motor shaft (40) is connected via at least one metal bellow connection (42, 44) to the pump shaft (38).

6. The system of claim 5, further comprising a connecting shaft (46), the connecting shaft couples the motor shaft (40) to the pump shaft (38).

7. The system of claim 6, wherein the motor shaft (40) is coupled via a first metal bellow connection (42) to the connecting shaft (46) and the connecting shaft (46) is coupled via a second metal bellow connection (44) to the pump shaft (38).

8. The system according to any claim 4 to 7, when depending on claim 2, wherein the motor shaft, the pump shaft or the connecting shaft (46) traverses a wall (34) of the housing (3).

9. The system of any one of the preceding claims 4 to 8, wherein the pump shaft (38) includes bearings, in particular ball bearings, wherein the bearings of the scroll pump shaft (38) are heat resistant for a temperature between 80 and 150 degrees Celsius.

10. The system according to claim 9, wherein a lubricant of the bearings of the pump (24) is heat resistant for a temperature between 80 and 150 degrees Celsius.

11. The system according to one of the preceding claims, wherein the pump includes a pressure sensor for detecting leaks within the pump (24).

12. The system according to any one of the preceding claims, further comprising a bypass fluid circuit (16) the bypass fluid circuit (16) being adapted to bypass the pump (24), the temperature-controlled subsystem (3) providing a heat supply to the bypass fluid circuit (16) adapted to maintain a temperature within the bypass fluid circuit (16) during operation such that said temperature is above the crystallization temperature of UF6.

13. The system according to claim 12, wherein the bypass circuit (16), the upstream supply circuit (10, 20) and the pump (24) are provided in a common temperature-controlled subsystem (3), in particular in a common housing.

14. Conversion installation for converting UF6 into UO2, the conversion installation (50) being feed with gaseous UF6 by a system (1) according to any one of the preceding claims.

15. Method for emptying UF6 from a UF6 container (7) with a system according to one of the preceding claims 1 to 14, the method comprising: placing the UF6 container (7) in an autoclave (5), heating the UF6 container (7) in the autoclave (5); activating the pump (24).

16. Method according to claim 15, wherein the pump (24) is activated, when the pressure in the UF6 container is below 2000 mbar, in particular below 1800 mbar and, inparticular, the pump (24) remains activated at least until the pressure in the UF6 container is lower than 100 mbar.

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