A dissolved oxygen control system in liquid metal coolant

Abstract

The present invention provides a dissolved oxygen control system in a liquid metal coolant, comprising: a container containing liquid metal coolant, an oxygen injector installed on the container for injecting oxygen into the liquid metal coolant, an oxygen injection controller connected to the oxygen injector for controlling the oxygen injector; an oxygen sensor installed on the container for detecting the oxygen content in the liquid metal coolant, and a working electrode installed on the container; the oxygen sensor is connected to the oxygen injection controller; the oxygen injector comprises a zirconium oxide ceramic probe, and a catalyst for dissociating oxygen molecules into oxygen ions is arranged in the zirconium oxide ceramic probe. By using a catalyst to dissociate oxygen molecules in the air into oxygen ions, the oxygen ions are injected into the liquid metal coolant under the action of an external potential. Since the flux of injected oxygen ions is determined by the external potential and the activation area of ​​the oxygen injector probe, the oxygen injection rate can be better controlled to achieve an excellent oxygen control effect.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear reactor coolants, and in particular to a dissolved oxygen control system in a liquid metal coolant. Background Art

[0002] Liquid metals such as lead, lead-bismuth eutectic alloys or sodium-cooled fast neutron reactors can breed nuclear fuel, reduce the generation of nuclear waste, and realize closed nuclear fuel circulation, thereby greatly improving the utilization rate of uranium resources. They are the next generation of nuclear reactor technology that is being studied. Among them, liquid lead or lead-bismuth alloy-cooled fast neutron reactors have excellent intrinsic nuclear safety performance in addition to the above advantages, and have received widespread attention in recent years. However, there is a problem of liquid metal corrosion between liquid lead or lead-bismuth coolants and structural materials such as ferrite / martensitic steel and austenitic stainless steel. Liquid metal corrosion depends on the dissolved oxygen content. When the oxygen content is too high, the steel surface will be oxidized to form an overly thick oxide film. For nuclear fuel cladding, a too thick oxide film will hinder the heat transfer from the nuclear fuel pellets to the coolant outside the cladding. Excessive oxygen content will also cause lead to be oxidized to form lead oxide with poor fluidity, resulting in blockage of the core cooling flow channel. If the dissolved oxygen is too low, a dense and continuous protective oxide film cannot be formed on the steel surface, and the steel substrate is directly exposed to the liquid metal environment, resulting in element selective dissolution corrosion (such as nickel), and the dissolved corrosion products are precipitated at the cold end of the reactor, which will not only form highly radioactive dirt, but also cause flow channel blockage. Therefore, it is very necessary to control the dissolved oxygen in the liquid metal and keep it within a reasonable range.

[0003] At present, the main oxygen control methods are gas phase oxygen control and solid phase oxygen control. The basic principle of gas phase oxygen control is to use PID control method to automatically control the flow rate of oxidizing gas and reducing gas introduced into liquid metal to achieve oxygen control. When the oxygen content is high, reducing gas is introduced, and when the oxygen content is low, oxidizing gas is introduced. Oxidizing gas can be a certain proportion of Ar+O 2 or Ar+H 2 O and other mixed gases, the ratio of the mixed gas and the volume of the liquid metal determine the sensitivity of the oxygen supply. The reducing gas can be pure hydrogen or a certain ratio of Ar+H 2 This method has been successfully applied in many liquid metal experimental circuits and devices at home and abroad. The principle of solid-state oxygen control is to install many lead oxide balls on the bypass of the main circuit, and to control the decomposition rate of the lead oxide balls by regulating the lead-bismuth flow and temperature flowing through the lead oxide ball area, so as to achieve automatic control of the dissolved oxygen content in the main circuit. This method has been applied in engineering in Russia's liquid lead-bismuth nuclear reactor. However, the above two oxygen control methods cannot finely control the dissolved oxygen.

[0004] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0005] In view of the above-mentioned deficiencies of the prior art, an object of the present invention is to provide a dissolved oxygen control system in a liquid metal coolant, aiming to solve the problem in the prior art that it is difficult to achieve fine regulation of dissolved oxygen when controlling oxygen in the liquid metal coolant.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0007] A dissolved oxygen control system in a liquid metal coolant, comprising: a container containing the liquid metal coolant, an oxygen injector installed on the container for injecting oxygen into the liquid metal coolant, an oxygen injection controller communicatively connected to the oxygen injector for controlling the oxygen injector; an oxygen sensor installed on the container for detecting the oxygen content in the liquid metal coolant, and a working electrode installed on the container; the oxygen sensor is communicatively connected to the oxygen injection controller; the oxygen injector comprises a zirconia ceramic probe, and a catalyst for dissociating oxygen molecules into oxygen ions is provided in the zirconia ceramic probe.

[0008] Optionally, the dissolved oxygen control system in the liquid metal coolant further includes a reducing gas supply device and a deoxygenation controller, the reducing gas supply device is connected to the container through a pipeline, an analog gas valve is provided on the pipeline, and the deoxygenation controller is communicatively connected to the analog gas valve and the oxygen sensor respectively.

[0009] Optionally, in the system for controlling dissolved oxygen in liquid metal coolant, the zirconia ceramic is 5 mol % or 8 mol % yttria-stabilized zirconia solid electrolyte ceramic.

[0010] Optionally, in the system for controlling dissolved oxygen in liquid metal coolant, the catalyst is one or more of nano-platinum powder, strontium lanthanum cobaltate, strontium lanthanum ferrite, strontium lanthanum manganate and strontium lanthanum cobaltate iron.

[0011] Optionally, in the dissolved oxygen control system in the liquid metal coolant, the oxygen injection controller includes a voltmeter and a PID module, the voltmeter is communicatively connected to the oxygen sensor, and the PID module is communicatively connected to the oxygen injector.

[0012] Optionally, in the dissolved oxygen control system in the liquid metal coolant, the deoxygenation controller includes a voltmeter and a PID module, the voltmeter is communicatively connected to the oxygen sensor, and the PID module is communicatively connected to the analog gas valve.

[0013] Optionally, in the dissolved oxygen control system in the liquid metal coolant, the oxygen sensor is an air reference electrode or a metal reference electrode.

[0014] Optionally, in the dissolved oxygen control system in the liquid metal coolant, the deoxygenation controller further comprises a manual voltage adjustment knob, and the output upper limit of the PID module is manually adjusted by the manual voltage adjustment knob.

[0015] Optionally, in the system for controlling dissolved oxygen in liquid metal coolant, a heating wire is wound around the outer wall of the container.

[0016] Optionally, the dissolved oxygen control system in the liquid metal coolant further includes a terminal for recording and displaying the voltage value collected by the voltmeter.

[0017] Beneficial effect: The present invention provides a dissolved oxygen control system in a liquid metal coolant, the system comprising: a container containing liquid metal coolant, an oxygen injector installed on the container for injecting oxygen into the liquid metal coolant, an oxygen injection controller connected to the oxygen injector for controlling the oxygen injector; an oxygen sensor installed on the container for detecting the oxygen content in the liquid metal coolant, and a working electrode installed on the container; the oxygen sensor is connected to the oxygen injection controller for communication; the oxygen injector comprises a zirconia ceramic probe, and a catalyst for dissociating oxygen molecules into oxygen ions is arranged in the zirconia ceramic probe. The oxygen molecules in the air are dissociated into oxygen ions by using a catalyst, and the potential on the oxygen injection probe is regulated by the oxygen injection controller to inject oxygen ions into the liquid metal coolant. Since the flux of injected oxygen ions is determined by the control potential and the activation area of ​​the oxygen injector probe, the oxygen injection rate can be better controlled, and when the activation area is small, the oxygen injection rate can be carried out within a very small range, which is conducive to controlling the oxygen concentration at an extremely low level. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of a dissolved oxygen control system in a liquid metal coolant provided in an embodiment of the present invention.

[0019] Figure 2 It is a structural diagram of the oxygen injector provided in an embodiment of the present invention.

[0020] Figure 3 This is a test chart of the experimental results of Example 1 provided by the present invention.

[0021] Description of the numbers in the figure:

[0022] 1-container, 2-heating wire, 3-liquid metal coolant, 4-flange container cover, 5-oxygen sensor, 6(7)-oxygen injector, 8-working electrode, 9-gas cylinder, 10-stainless steel gas pipe, 11-analog gas valve, 12-exhaust port, 13-oxygen injection controller, 14-high internal resistance voltmeter, 15-voltage display meter, 16-voltage manual adjustment knob, 17-PID module, 18-computer and data acquisition device; 19-deoxygenation controller, 20-voltage manual adjustment knob, 21-high internal resistance voltmeter, 22-voltage display meter, 23-PID module. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention clearer and more specific, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in the present invention, unless otherwise specified, include direct and indirect connections (couplings). In the description of the present invention, it should be understood that the orientation or position relationship indicated by the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. are based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0025] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0026] like Figure 1As shown, a dissolved oxygen control system in a liquid metal coolant comprises: a container 1 containing liquid metal coolant, an oxygen injector 6 (7) installed on the container 1 for injecting oxygen into the liquid metal coolant 3, an oxygen injection controller 13 connected in communication with the oxygen injector 6 (7) for controlling the oxygen injector; an oxygen sensor 5 installed on the container 1 for detecting the oxygen content in the liquid metal coolant, and a working electrode 8 installed on the container 1; the oxygen sensor 5 is connected in communication with the oxygen injection controller 13; the oxygen injector 6 (7) comprises a zirconia ceramic probe, and a catalyst for dissociating oxygen molecules into oxygen ions is arranged in the zirconia ceramic probe.

[0027] In this embodiment, the container 1 is provided with a flange cover 4, and an oxygen injector 6 (7), an oxygen sensor 5, an exhaust hole 12 and an electrode 8 are provided on the flange cover 4. The voltage outputted to the oxygen injector 6 (7) is regulated by the oxygen injection controller 13, so that the catalyzed oxygen ions inside the zirconia ceramic probe are forced to move from the inside of the zirconia ceramic probe to the liquid metal coolant outside, thereby achieving the purpose of injecting oxygen into the liquid metal coolant. Since the flux of injected oxygen ions is determined by the control potential and the activation area of ​​the oxygen injector probe, the oxygen injection rate can be better controlled, and when the activation area is small, the oxygen injection rate can be carried out within a very small range, which is conducive to controlling the oxygen concentration at an extremely low level.

[0028] In some embodiments, Figure 2 As shown, the oxygen injector 6 (7) is composed of a YSZ tube 61 and a stainless steel sealing component 62. The bottom of the YSZ tube is a probe inserted into the liquid metal 3. Two small holes 63 are opened at the upper end of the oxygen injector 6 (7) to ensure that air can enter the inside of the probe. If used in a nuclear reactor, the two small holes need to be connected to the air container outside the nuclear island by a sealed conduit. The catalyst inside the probe at the lower end of the oxygen injector 6 (7) is one of nano platinum powder (Pt), lanthanum strontium cobaltate (LSC), lanthanum strontium ferrite (LSF), lanthanum strontium manganate (LSM), lanthanum strontium cobaltate iron (LSCF) or any combination thereof. The purpose of the catalyst is to dissociate oxygen molecules in the air into oxygen ions.

[0029] Optionally, the zirconia ceramic is 5 mol % or 8 mol % yttria-stabilized zirconia solid electrolyte ceramic (YSZ for short).

[0030] Optionally, a heating wire 2 is wound around the outer surface of the container, and the container can be heated by electrical heating.

[0031] In some embodiments, the dissolved oxygen control system in the liquid metal coolant also includes a reducing gas supply device 9 and a deoxygenation controller 19. The reducing gas supply device 9 is connected to the container 1 through a pipeline 10. An analog gas valve 11 is provided on the pipeline 10. The deoxygenation controller 13 is respectively communicated with the analog gas valve 11 and the oxygen sensor 5.

[0032] Specifically, the reducing gas supply device 9 is a gas cylinder. The gas in the gas cylinder 9 can be a reducing gas Ar+5%H 2 Or pure hydrogen, but for safety reasons, Ar + 5% H 2 The gas in the gas cylinder 9 is introduced into the liquid metal 3 through the stainless steel gas pipe 10, in order to reduce the dissolved oxygen content in the liquid metal 3. An analog gas valve 11 is also installed on the stainless steel gas pipe 10. The amount of reducing gas entering the liquid metal is controlled by adjusting the flow rate of the analog gas valve, so as to control the speed of removing dissolved oxygen in the liquid metal 3. The remaining gas is discharged from the exhaust port 12.

[0033] In some embodiments, the oxygen injection controller 13 includes a high internal resistance voltmeter 14, a voltage display meter 15 and a PID module 17, wherein the high internal resistance voltmeter 14 is communicatively connected to the oxygen sensor 5, and the PID module 17 is communicatively connected to the oxygen injector 6 (7).

[0034] In one embodiment, the dissolved oxygen control system in the liquid metal coolant further includes a terminal for recording and displaying the voltage value collected by the voltmeter. The terminal may be a computer 18. By setting up a computer in the system, the control result can be conveniently and intuitively displayed.

[0035] Specifically, the voltage signal of the oxygen sensor 5 is collected by the high internal resistance voltmeter 14 of the oxygen injection controller 13, and the high internal resistance voltmeter 14 then converts the collected voltage into a standard signal and transmits it to the PID module 17. At the same time, the collected voltage is sent to the data collector in the computer 18 for data storage and display. The PID module 17 automatically adjusts the voltage output on the oxygen injector 6 (7) according to the target oxygen control potential, forcing the catalyzed oxygen ions inside the probe to move from the inside of the YSZ probe to the outside of the liquid metal 3, thereby achieving the purpose of injecting oxygen into the liquid metal 3. The voltage display meter 15 on the oxygen injection controller 13 displays the output signal of the PID module 17 in real time. At the same time, it is sent to the data collector in the computer 18 for data storage and display.

[0036] Furthermore, the oxygen injection controller also includes a voltage manual adjustment knob 16 which can manually adjust the output upper limit of the PID module 17 to prevent the YSZ probe from being burned.

[0037] In some embodiments, the deoxygenation controller 19 includes a high internal resistance voltmeter 21 and a PID module 23 . The high internal resistance voltmeter 21 is communicatively connected to the oxygen sensor 5 , and the PID module 23 is communicatively connected to the analog gas valve 11 .

[0038] Specifically, the voltage signal of the oxygen sensor 5 is collected by the high internal resistance voltmeter 21 on the deoxygenation controller 19, and the high internal resistance voltmeter 21 then converts the collected signal into a standard signal and sends it to the PID module 23. The PID module 23 adjusts the flow of the analog gas valve 11 according to the target oxygen control range, thereby controlling the speed of removing dissolved oxygen in the liquid metal 3. When the dissolved oxygen is lower than the target value, the deoxygenation controller 19 closes the analog gas valve 11, and the oxygen injection controller 13 works at this time, and vice versa. The purpose of automatic oxygen control is achieved by using the oxygen injection controller in conjunction with the deoxygenation controller.

[0039] In this embodiment, the deaerator controller 19 is also provided with a voltage display meter 22 and a voltage manual adjustment knob 20. The voltage display meter 22 can display the output voltage of the PID module 23 in real time, and the voltage manual adjustment knob 20 can set the output voltage upper limit of the PID module 23.

[0040] In some embodiments, the oxygen sensor 5 is an air reference electrode or a metal reference electrode.

[0041] Specifically, the oxygen sensor 5 can use an air reference electrode or a metal / metal oxide reference electrode. When the air reference electrode is used, the structure of the oxygen sensor 5 is the same as that of the oxygen injector 6 (7); when the metal / metal oxide reference electrode is used, the upper end of the oxygen sensor 5 does not need to be opened, and the rest of the structure is the same as that of the oxygen injector 6 (7). The low potential ends of the oxygen sensor 5 and the oxygen injector 6 (7) are both connected to the working electrode 8 inserted into the liquid metal 3.

[0042] The above system provided by the present invention is further explained below through specific embodiments.

[0043] Embodiment 1:

[0044] according to Figure 1 The structure shown is used to make an oxygen control device. The basic structure and functions of each component have been described above. The liquid metal 3 is a lead-bismuth eutectic alloy with a volume of 5L and a temperature of 428°C. The gas in the gas cylinder 9 is Ar+5%H 2 The oxygen sensor 5 uses an air reference electrode, the catalyst of the oxygen injectors 6 and 7 uses LSC, the YSZ tube uses a 5mol% YSZ tube, and the activation area of ​​the tube probe is about 240mm 2First, open the analog gas valve 11 and keep its flow rate constant at 1.2L / h. Under the action of reducing gas, the dissolved oxygen content continues to decrease, and the signal of oxygen sensor 5 continues to increase. When the oxygen content corresponding to the signal is lower than the target oxygen content of 3.5x10 - 11 wt%, the oxygen injection controller 13 is turned on and the voltage value corresponding to the target oxygen content is set.

[0045] Depend on Figure 3 The results show that under the automatic regulation of the oxygen injection controller 13, the dissolved oxygen is 4x10 -11 wt% and 3x10 -11 After the controller was turned off, the dissolved oxygen deviated seriously from the target value. After the controller was turned on again, the dissolved oxygen approached the target value, and then fluctuated slightly around the target value, achieving a relatively stable oxygen control effect.

[0046] In summary, the present invention provides a dissolved oxygen control system in a liquid metal coolant, comprising: a container containing liquid metal coolant, an oxygen injector installed on the container for injecting oxygen into the liquid metal coolant, an oxygen injection controller connected to the oxygen injector for controlling the oxygen injector; an oxygen sensor installed on the container for detecting the oxygen content in the liquid metal coolant, and a working electrode installed on the container; the oxygen sensor is connected to the oxygen injection controller; the oxygen injector comprises a zirconia ceramic probe, and a catalyst for dissociating oxygen molecules into oxygen ions is arranged in the zirconia ceramic probe. By using a catalyst to dissociate oxygen molecules in the air into oxygen ions, when the activation area is constant, the flux of oxygen ions depends on the magnitude of the applied voltage, thereby achieving the purpose of injecting oxygen into the liquid metal, and then combined with automatic control to introduce reducing gas (Ar+H 2 or pure hydrogen, etc.), to achieve the purpose of automatic oxygen control. Since the flux of injected oxygen ions is determined by the control potential and the activation area of ​​the oxygen injector probe, the oxygen injection rate can be better controlled, and when the activation area is small, the oxygen injection rate can be carried out in a very small range, which is conducive to controlling the oxygen concentration at an extremely low level. Similarly, by increasing the number of oxygen injector probes (i.e., increasing the activation area), it is beneficial to increase the oxygen injection rate and control the oxygen concentration at a higher level.

[0047] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A dissolved oxygen control system in a liquid metal coolant, characterized in that: include: A container containing liquid metal coolant, an oxygen injector installed on the container for injecting oxygen into the liquid metal coolant, an oxygen injection controller connected in communication with the oxygen injector for controlling the oxygen injector; an oxygen sensor installed on the container for detecting the oxygen content in the liquid metal coolant, and a working electrode installed on the container; the oxygen sensor is connected in communication with the oxygen injection controller; the oxygen injector includes a zirconia ceramic probe, and a catalyst for dissociating oxygen molecules into oxygen ions is provided in the zirconia ceramic probe; The catalyst is one or more of nano-platinum powder, strontium lanthanum cobaltate, strontium lanthanum ferrite, strontium lanthanum manganate and strontium lanthanum cobaltate iron; The oxygen injection controller is used to regulate the voltage output on the oxygen injector, forcing the catalyzed oxygen ions inside the zirconia ceramic probe to move from the inside of the zirconia ceramic probe to the outside of the liquid metal coolant, thereby achieving the purpose of injecting oxygen into the liquid metal coolant; the flux of the injected oxygen ions is determined by the control potential and the activation area of ​​the oxygen injector probe.

2. The dissolved oxygen control system in liquid metal coolant according to claim 1, characterized in that: It also includes a reducing gas supply device and a deoxygenation controller. The reducing gas supply device is connected to the container through a pipeline. An analog gas valve is provided on the pipeline. The deoxygenation controller is communicated with the analog gas valve and the oxygen sensor respectively.

3. The dissolved oxygen control system in liquid metal coolant according to claim 1, characterized in that: The zirconia ceramic is a 5 mol % or 8 mol % yttria-stabilized zirconia solid electrolyte ceramic.

4. The dissolved oxygen control system in liquid metal coolant according to claim 1, characterized in that: The oxygen injection controller includes a voltmeter and a PID module. The voltmeter is communicatively connected to the oxygen sensor, and the PID module is communicatively connected to the oxygen injector.

5. The dissolved oxygen control system in liquid metal coolant according to claim 2, characterized in that: The deoxygenation controller includes a voltmeter and a PID module. The voltmeter is communicatively connected to the oxygen sensor, and the PID module is communicatively connected to the analog gas valve.

6. The dissolved oxygen control system in liquid metal coolant according to claim 1, characterized in that: The oxygen sensor is an air reference electrode or a metal reference electrode.

7. The dissolved oxygen control system in liquid metal coolant according to claim 5, characterized in that: The deoxygenation controller also includes a manual voltage adjustment knob, through which the output upper limit of the PID module is manually adjusted.

8. The dissolved oxygen control system in liquid metal coolant according to any one of claims 1 to 7, characterized in that: A heating wire is wound on the outer side wall of the container.

9. The dissolved oxygen control system in liquid metal coolant according to claim 7, characterized in that: It also includes a terminal for recording and displaying the voltage value collected by the voltmeter.

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