Method and system for detecting a uranium hexafluoride leak

Abstract

The detection method can be used to detect the presence of uranium hexafluoride (UF6) in a gas stream (G). The detection method comprises humidifying the gas stream by circulating the gas stream (G) in contact with a sulfonated tetrafluoroethylene-based fluoropolymer copolymer, in particular Nafion, and then detecting the presence of hydrogen fluoride (HF) in the gas stream (G) by means of a sensor.

Description

[0001] Method and system for detecting a uranium hexafluoride leak

[0002] The present invention relates to the field of uranium hexafluoride leak detection.

[0003] Uranium dioxide (UO2) is a fissile material used as nuclear fuel in nuclear power generation reactors.

[0004] It is possible to produce UCh from uranium hexafluoride (UFe). To do this, it is possible to use a conversion unit configured to convert gaseous UFe into uranium oxyfluoride (UO2F2) by hydrolysis in a reactor, by injecting gaseous UFe and dry steam into the reactor to obtain UO2F2 powder, then converting the UO2F2 powder into UCh2 powder by pyrohydrolysis in a furnace, by circulating the UO2F2 powder in the furnace and injecting dry steam and gaseous dihydrogen (H2) into the furnace.

[0005] Gaseous UFe is produced for example by vaporizing UFe in solid or liquid state contained in a reservoir placed in an autoclave oven swept by a flow of sweeping gas, the reservoir being fluidly connected to one or more nozzles for injecting gaseous UFe into the reactor.

[0006] For safety reasons, it is desirable to detect any potential UFe leaks in the autoclave oven reliably and with limited false alarms, for example by detecting the presence of UFe in the scavenging gas flow.

[0007] One of the aims of the invention is to propose a method for detecting UFe in a gas stream that is reliable and robust.

[0008] To this end, the invention proposes a method for detecting the presence of uranium hexafluoride in a gas stream, the detection method comprising:

[0009] - humidification of the gas stream by circulating the gas stream in contact with a fluoropolymer copolymer based on sulfonate tetrafluoroethylene, in particular Nation; then

[0010] - the detection of the presence of hydrogen fluoride in the gas stream using a sensor.

[0011] A copolymer fluoropolymer material based on sulfonate tetrafluoroethylene, particularly in Nation, is capable of retaining moisture and easily transferring it to a gaseous stream circulating in contact with the material.

[0012] In the presence of UFe in the gas stream, humidifying the gas stream induces a hydrolysis reaction of UFe with water, generating hydrogen fluoride (HF), the presence of which can be detected using a suitable sensor. Tetrafluoroethylene sulfonate copolymer fluoropolymer material, particularly in Nation, provides a simple, effective, and reliable means of humidifying the gas stream appropriately for UFe detection, without adding air to the gas stream, which would dilute the UFe.

[0013] The use of the fluoropolymer copolymer material based on sulfonate tetrafluoroethylene, particularly in Nation, thus allows the precise detection of UFe at a lower threshold.

[0014] A demister device placed upstream of the humidification device retains impurities, for example in the form of liquid droplets and / or solid particles, which could cause false alarms by deposition and / or interaction of these with a sensor, and impair detection.

[0015] In specific implementation modes, the detection method includes one or more of the following optional features, taken individually or in all technically possible combinations:

[0016] - the circulation of the gas flow in contact with fluoropolymer copolymer based on sulfonate tetrafluoroethylene, in particular of Nation, is carried out by circulation of the gas flow via a conduit delimited at least in part by a wall made of fluoropolymer copolymer based on sulfonate tetrafluoroethylene;

[0017] - the detection method includes defoaming the gas stream before humidifying the gas stream;

[0018] - degassing is achieved by passing the gas flow through a porous body;

[0019] - the porous body is a foam or a mass of fibers;

[0020] - the porous body is made of metal, in particular steel, preferably stainless steel.

[0021] The invention also relates to a system for detecting uranium hexafluoride in a gas stream, the detection system comprising:

[0022] - a humidification device configured for humidifying the gas stream by circulating the gas stream in contact with a sulfonate tetrafluoroethylene copolymer fluoropolymer, in particular Nation, and

[0023] - a measuring device configured to receive the gas stream after it has passed through the humidification device, the measuring device including a sensor configured to detect the presence of hydrogen fluoride in the gas stream.

[0024] In particular implementation modes, the detection system includes one or more of the following optional features, taken individually or in all technically possible combinations: - the humidification device includes a duct for the circulation of the gas flow, delimited at least in part by a wall made of fluoropolymer copolymer based on sulfonate tetrafluoroethylene;

[0025] - the detection system includes a demister fluidically connected device to the humidification device and configured for the removal of droplets present in the gas stream before it passes into the humidification device;

[0026] - the devesiculating device is configured for devesiculating the gas flow by passing through a porous body, for example a foam or a mass of fibers, the porous body preferably being made of metal, in particular steel, preferably stainless steel.

[0027] The invention also relates to an installation comprising a production device configured for the production of uranium fluoride hexafluoride by vaporizing the uranium fluoride hexafluoride contained in a reservoir in an autoclave furnace and circulating a flow of scouring gas in the autoclave furnace, and a detection system as defined above, arranged for the detection of the presence of uranium fluoride hexafluoride in the scouring gas flow.

[0028] In one embodiment, the installation includes a conversion unit configured for the conversion of uranium hexafluoride to uranium dioxide, the conversion unit being connected to the production device for its supply of uranium hexafluoride.

[0029] The invention and its advantages will be better understood upon reading the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings, on which:

[0030] - Figure 1 is a schematic view of an installation including a detection system for the detection of UFe in a gas flow of the installation;

[0031] - Figure 2 illustrates steps in a process for detecting UFe in a gas stream.

[0032] As illustrated in Figure 1, an installation 10 includes a detection system 12 for detecting the presence of UFe in a gas stream G to be monitored from the installation 10.

[0033] The detection system 12 includes a demister device 14 configured to separate from the gas stream G organic impurities, present for example in the form of liquid droplets or solid particles (such as fumes), suspended in this gas stream G.

[0034] The devesiculating device 14 includes a gas inlet 16 for receiving the gas flow G and a gas outlet 18 for the outlet of the devesiculated gas flow G. The devesiculating device 14 optionally has a pressure balancing device 20 configured to equalize the pressure between the inside and outside of the devesiculating device 14.

[0035] The devesiculating device 14 is, for example, configured for the passage of the gas flow G through a porous body 22. This allows the droplets present in the gas flow G to be deposited on the porous body 22.

[0036] The porous body 22 is for example a foam, preferably an open-cell foam, or a mass of fibers or more generally any substance having a high exchange surface area.

[0037] A porous body 22 in the form of a foam or a mass of fibers allows significant contact of the gas flow with the porous body 22, promoting the deposition of liquid droplets present in the gas flow G onto the porous body 22.

[0038] The porous body 22 is, for example, made of metal, in particular steel, preferably stainless steel. The porous body 22 is, in particular, a metallic foam or a mass of metallic fibers.

[0039] The devesiculating device 14 includes a chamber 26 inside which is disposed the porous body 22, the gas inlet 16 being arranged so that the gas flow G enters the chamber 26 and passes through the porous body 22 to go from the gas inlet 16 to the gas outlet 18.

[0040] If necessary, the balancing device 20 is configured to achieve pressure balancing between the inside and outside of the enclosure 26 of the devesiculator 14.

[0041] Preferably, the gas inlet 16 of the demisting device 14 is equipped with an inlet valve 28.

[0042] Preferably, the pressure balancing device 20 of the demister device 14 is equipped with a balancing valve 30.

[0043] The detection system 12 includes a humidification device 32 configured to humidify the gas flow G.

[0044] The devesiculating device 14 is arranged fluidically upstream of the humidification device 32 for the devesiculation of the gas flow G in the devesiculating device 14 before its humidification in the humidification device 32.

[0045] The humidification device 32 is configured to circulate the gas flow G through a conduit 34 at least partially delimited by a wall 36 made of fluoropolymer copolymer based on sulfonate tetrafluoroethylene, in particular Nation, so as to allow moisture exchange through the wall 36, between the outside and the inside of the conduit 34. A wall 36 made of fluoropolymer copolymer based on sulfonate tetrafluoroethylene, in particular Nation, is capable of retaining moisture from the outside and transferring it in part to a gas flow circulating inside the conduit 34.

[0046] Thus, the circulation of the gas flow G via the conduit 34, at least partly delimited by a wall 36 made of fluoropolymer copolymer based on tetrafluoroethylene sulfonate, in particular in Nation, makes it possible to balance the humidity between the gas flow G and the outside air, and thus to humidify the gas flow G.

[0047] If UFe is present in the gas stream, humidification of the gas stream causes hydrolysis of UFe and consequently the appearance of HF.

[0048] Conduit 34, for example, is rigid or flexible.

[0049] The detection system 12 includes a measuring device 40 arranged to receive the gas flow G exiting the humidification device 32, the measuring device 40 including a sensor 42 configured to detect the presence of HF in the gas flow G, and preferably to measure the HF content in the gas flow G.

[0050] The sensor 42 is configured to provide a measurement signal Mes indicating the presence of HF in the gas flow G, and preferably representative of the HF content of the gas flow G.

[0051] Sensor 42, for example, is configured for the detection of the presence of HF by colorimetry or using a specific electrode (redox type sensor).

[0052] The detection system 12 advantageously includes an electronic data processing unit 44 comprising a measurement module 46 configured to receive the measurement signal Mes from the sensor 42 and to determine the presence of UFe in the gas flow G as a function of the measurement signal Mes, in particular as a function of the HF content of the gas flow G indicated by the measurement signal Mes.

[0053] In examples, the measurement module 46 is a software application comprising code instructions stored in a memory 48 of the electronic data processing unit 44 and executable by a processor 50 of the electronic data processing unit 44.

[0054] In variants, the measurement module 46 is a programmable logic component, in particular an in situ programmable gate array (or FPGA for "Field Programmable Gate Array"), or a specialized integrated circuit (or ASIC for "Application Specific Integrated Circuit").

[0055] In some examples, the detection system 12 includes a user terminal 52 connected to the electronic data processing unit 44 for transmitting measurement data from the electronic data processing unit 44 to the user terminal 52 and for viewing by a human operator. The user terminal 52 includes, for example, a human-machine interface, including in particular a display screen (not shown) and a graphical user interface. The user terminal 52 is, for example, a computer, a tablet, or a mobile phone.

[0056] Installation 10 illustrated in Figure 1 includes, for example, a conversion unit 54 configured for the conversion of UFe in gaseous form into UCh powder.

[0057] The conversion unit 54 is configured for example to carry out a hydrolysis of gaseous UFe in the presence of dry steam in a reactor to obtain UO2F2 powder, then to convert the UO2F2 powder into UCh powder by pyrohydrolysis of the UO2F2 powder in a furnace in the presence of dry steam and gaseous H2.

[0058] As shown schematically in Figure 1, the conversion unit 54 receives as input gaseous uranium hexafluoride UFe, a stream of dry water vapor H2O and an incoming stream of neutral gas N2 and has separate outputs for UC>2 powder, a stream of gaseous hydrogen fluoride HF and an outgoing stream of neutral gas N2.

[0059] Installation 10 includes, for example, a production device 56 configured for the production of gaseous UFe and the supply of gaseous UFe to the conversion unit 54.

[0060] The production device 56 includes, for example, a tank 58 containing UFe in solid or liquid form arranged in an autoclave oven 60 configured for the circulation of a gas flow G for scavenging, the tank 58 being fluidly connected to the conversion unit 54 for supplying the conversion unit with gaseous UFe.

[0061] It is important to ensure that the scavenging gas flow exiting the autoclave furnace 60 does not contain UFe from an internal UFe leak in the autoclave furnace 60.

[0062] The detection system 12 is for example fluidically connected to the autoclave oven 60 to receive the outgoing sweep gas flow as the gas flow G to be monitored, and to detect the possible presence of UFe in the sweep gas flow exiting the autoclave oven 60.

[0063] Steps in a process for detecting a UFe leak that can be implemented by a detection system 12 according to Figure 1 are illustrated in Figure 2.

[0064] The detection process includes a step E1 of devesiculation of the gas flow G, carried out in the devesiculating device 14, to remove from the gas flow G droplets present in the gas flow G.

[0065] The devesiculation is carried out for example by passing the gas flow G through a porous body 22 in such a way that the gas flow G passes through the porous body 22 and droplets present in the gas flow G are deposited on the porous body 22. The detection process includes a step E2 of humidification of the gas flow G, carried out in the humidification device 32, by circulation of the gas flow G in contact with fluoropolymer copolymer based on sulfonate tetrafluoroethylene, in particular Nation.

[0066] The E2 step of humidifying the gas flow G is carried out after the E1 step of devesiculation.

[0067] The circulation of the gas flow G in contact with a wall 36 made of fluoropolymer copolymer based on sulfonate tetrafluoroethylene, in particular Nation, is carried out for example by circulation of the gas flow G in a conduit 34 at least partly delimited by the wall 36 made of fluoropolymer copolymer based on sulfonate tetrafluoroethylene, in particular Nation.

[0068] This allows the humidity to be balanced between the flow of gas G circulating in the duct 34 and the outside air, and thus to humidify the flow of gas G.

[0069] The detection method includes a step E3 of detecting the presence of HF in the moistened gas stream G, for example using a sensor 42 configured to detect the presence of HF, and, preferably, measuring the HF content of the gas stream.

[0070] The detection method includes a step E4 of determining the presence of HF in the gas flow G as a function of the measurement signal provided by the sensor 42, for example using a detection module 46 of an electronic data processing unit 44.

[0071] The detection method advantageously includes a reporting step E5 comprising sending and / or displaying a message to an operator. The message indicates the detection of HF in the gas stream G, the HF content of the gas stream G, and / or the occurrence of a UFe leak. The message is, for example, sent by the electronic data processing unit 44. The message is, for example, sent to and / or displayed on the user terminal 52.

[0072] The detection system 12 allows for easy, reliable and robust detection of the presence of UFe in a gas stream G, in particular for detecting the presence of a UFe leak in an autoclave oven 60 of a production device 56 for the production of gaseous UFe.

[0073] The circulation of the gas flow G through a conduit 34, at least partially delimited by a wall 36 made of a fluoropolymer copolymer based on sulfonate tetrafluoroethylene, in particular Nation, allows humidification of the gas flow G without dilution of the UFe, which is capable of causing hydrolysis of any UFe present in the gas flow, resulting in the appearance of HF detectable by means of a suitable sensor 42. The demister 14, located upstream of the humidification device 32, retains foreign bodies and / or impurities that could cause false alarms and impair detection.

Claims

9 DEMANDS 1. Method for detecting the presence of uranium hexafluoride (UFe) in a gas stream (G), the detection method comprising: - humidification of the gas stream by circulating the gas stream (G) in contact with a fluoropolymer copolymer based on sulfonate tetrafluoroethylene, in particular Nation; then - detection of the presence of hydrogen fluoride (HF) in the gas stream (G) using a sensor.

2. Detection method according to claim 1, wherein the circulation of the gas flow in contact with fluoropolymer copolymer based on tetrafluoroethylene sulfonate, in particular Nation, is achieved by circulation of the gas flow (G) via a conduit (34) delimited at least in part by a wall (36) made of fluoropolymer copolymer based on tetrafluoroethylene sulfonate.

3. Detection method according to claim 1 or 2, comprising defoaming of the gas stream (G) before humidification of the gas stream (G).

4. Detection method according to claim 3, wherein the devesiculation is carried out by passing the gas flow (G) through a porous body (22).

5. Detection method according to claim 4, wherein the porous body (22) is a foam or a mass of fibers.

6. Detection method according to claim 4 or 5, wherein the porous body (22) is made of metal, in particular steel, preferably stainless steel.

7. Uranium hexafluoride (UFe) detection system in a gas stream (G), the detection system comprising: - a humidification device (32) configured for humidifying the gas stream (G) by circulating the gas stream (G) in contact with a fluoropolymer copolymer based on sulfonate tetrafluoroethylene, in particular Nation, and - a measuring device (40) configured to receive the gas stream (G) after it has passed through the humidification device (32), the measuring device (40) comprising a sensor (42) configured to detect the presence of hydrogen fluoride (HF) in the gas stream (G).

8. Detection system according to claim 7, wherein the humidification device (32) comprises a conduit (34) for the circulation of the gas flow (G), delimited at least in part by a wall (36) made of fluoropolymer copolymer based on tetrafluoroethylene sulfonate.

9. A detection system according to claim 7 or 8, comprising a demister (14) fluidly connected to the humidification device (32) and configured for removing droplets present in the gas stream (G) before it passes through the humidification device (32).

10. A detection system according to claim 9, wherein the demister (14) is configured for demistering the gas stream (G) by passing it through a porous body (22), for example, a foam or a bundle of fibers, the porous body (22) preferably being made of metal, in particular steel, preferably stainless steel. 11.Installation comprising a production device (56) configured for the production of uranium fluoride hexafluoride (UFe) by vaporizing the uranium fluoride hexafluoride (UFe) contained in a tank (58) in an autoclave furnace (60) and circulating a flow of scouring gas in the autoclave furnace (60), and a detection system according to any one of claims 7 to 10 arranged for the detection of the presence of uranium fluoride hexafluoride (UFe) in the scouring gas flow.

12. Installation according to claim 11, comprising a conversion unit (54) configured for the conversion of uranium hexafluoride (UFe) into uranium dioxide (UO2), the conversion unit (54) being connected to the production device (56) for its supply of uranium hexafluoride (UFe).

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