An on-line measurement system for the fission gas release pressure of a reactor fuel element

Abstract

The present invention discloses an on-line measurement system for the fission gas release pressure of a reactor fuel element, which includes a fission gas release pressure measurement mechanism, a displacement signal and data processing system, and a gas regulation system; the fission gas release pressure measurement mechanism includes a gas pressure measurement section located inside the reactor pressure vessel; the gas pressure measurement section includes an outer sleeve; a pressure-bearing sleeve and a linear displacement sensor are sequentially fixed at one end to the other end in the inner side of the outer sleeve; a bellows is fixed inside the pressure-bearing sleeve, and an adjustment air chamber and a measurement air chamber are respectively arranged in the pressure-bearing sleeve at both ends of the bellows; a magnetic core rod is fixed at the other end of the bellows, and the magnetic core rod extends into the inner cavity of the winding skeleton of the linear displacement sensor. By using a displacement sensor in combination with a bellows for measurement, the problem that it is difficult to on-line measure the fission gas pressure of the existing reactor fuel can be solved, the operation economy and safety of the reactor can be improved, and at the same time, technical support can be provided for the research and development verification of new fuels for research reactors.

Description

Technical Field

[0001] The present invention relates to the field of measurement of operating behavior parameters of fuel elements in the core of a reactor and a research reactor, and particularly relates to an on-line measurement system for the fission gas release pressure of a reactor fuel element. Background Art

[0002] The fuel element is the core component of the reactor core, and its performance is closely related to the safety, reliability, service life and safety performance of the nuclear power plant. During the operation of the reactor, the nuclear fuel will undergo a chain fission reaction, and the fission products will have a certain impact on the fuel and the cladding. Among them, a large amount of fission gas generated during the irradiation of the nuclear fuel element will cause a certain degree of swelling of the fuel element. The swelling will increase with the increase of burnup, resulting in a stronger interaction between the fuel and the cladding, and the operating risk of the fuel element in the reactor will increase. In view of this, it is of extremely important significance and value to monitor the fission gas release pressure of nuclear fuel in the reactor.

[0003] The measurement of fission gas is divided into the measurement of fission gas pressure and the measurement of fission gas composition. For the measurement of fission gas release pressure, the backpressure method and the displacement method can be used. The backpressure method mainly balances the fission gas pressure through pressure recoil. A double-stage bellows is used in the device. When the fission gas pressure increases, the shaft in the middle of the bellows will move, pushing the conductive block in the electrical detection device to move. By adjusting the pressure of the recoil gas, when this pressure is close to the gas pressure, the conductive block is connected to the electrical contact block to make the circuit connected. Then the gas pressure can be measured. However, the disadvantage of this method is that its response time is relatively long.

[0004] Another effective method for measuring gas pressure is to use an LVDT combined with a bellows for measurement. The upper end of the bellows is fixed, and a gas with a certain pressure is sealed in the bellows. The gas released by the fuel pellet is collected in the sealed cavity in the end plug. As the gas release pressure increases, the bellows will be further compressed. The lower end of the bellows is connected to the iron core of the LVDT. As the bellows is compressed, the iron core will move upward, generating an induced signal in the LVDT to obtain the expansion and contraction amount of the bellows. According to the elastic characteristics of the bellows and its expansion and contraction amount, the pressure of the gas inside the bellows can be obtained. At the same time, due to the compression of the bellows, the pressure of the gas inside the bellows will increase, and the pressure of the internal gas can be calculated based on the volume change. Combining the elastic force of the bellows and the pressure of the internal gas, the fission gas pressure can be obtained.

[0005] The conventional means of analyzing the composition of fission gas is sampling. In order to facilitate the carrying of the generated gas out of the reactor, a gas mixing system must be set up in the system. Ne and He are passed through the gas mixing system, and the gas temperature needs to be strictly controlled to accurately control the flow rate. The added gas enters the irradiation device in the reactor and carries the generated fission gas out of the reactor, passing through purification systems such as particle filtration, and then enters the detection device. The disadvantage of the direct sampling method is that a special gas mixing system needs to be arranged and a large amount of waste gas will be generated. The acoustic wave measurement method can realize direct detection of fission gas in the reactor. This method is based on high-frequency echo technology, mainly using sound sensors to record the shape of the echo, thereby detecting the echo rate of the sound wave in the gas and the attenuation of the echo. The speed of the sound wave depends on the composition of the fission gas, and the attenuation of the sound wave is closely related to the gas pressure. By detecting the rate and attenuation of the echo, the purpose of simultaneously measuring the composition and pressure of the fission gas is achieved.

[0006] In summary, the existing nuclear reactor core has insufficient means and methods for measuring the fission gas release pressure of fuel elements under the harsh operating conditions of high temperature, high pressure and strong nuclear radiation. There are engineering technical difficulties in that the means and methods for measuring the fission gas release pressure of fuel core blocks under the harsh operating conditions in the reactor are limited and insufficient. Summary of the invention

[0007] The present invention aims to solve the deficiencies of the prior art and to provide an online measurement system for the fission gas release pressure of reactor fuel elements. By adopting a displacement sensor in combination with a bellows for measurement, the problem that the existing reactor fuel fission gas pressure is difficult to measure online can be solved, the economy and safety of reactor operation can be improved, and technical support can be provided for the research and development and verification of new fuels for research reactors.

[0008] The present invention is achieved through the following technical solutions:

[0009] An online measurement system for the release pressure of fission gas of a reactor fuel element, comprising a fission gas release pressure measurement mechanism, a displacement signal and data processing system and a gas regulating system;

[0010] The fission gas release pressure measurement mechanism comprises a gas pressure measurement section located inside the reactor pressure vessel, and the gas pressure measurement section is located in the core active area of ​​the reactor pressure vessel;

[0011] The gas pressure measuring section comprises an outer sleeve, the lower end of which is fixed to the fuel cladding; a pressure sleeve and a linear displacement sensor are fixed in sequence from one end to the other end of the inner side of the outer sleeve; the pressure sleeve opens at one end toward the fuel cladding and is connected to the fuel pellet;

[0012] A corrugated pipe is fixed inside the pressure-bearing casing. Inside the pressure-bearing casing at both ends of the corrugated pipe, there are respectively an adjustment air chamber and a measurement air chamber. One end of the corrugated pipe facing the measurement air chamber is open, and the fuel pellets are sequentially communicated through an opening at one end of the pressure-bearing casing, the measurement air chamber, an opening at one end of the corrugated pipe, and the inside of the corrugated pipe;

[0013] A magnetic core rod is fixed at the other end of the corrugated pipe. The magnetic core rod passes through the other end of the pressure-bearing casing and extends into the inner cavity of the winding skeleton of the linear displacement sensor. The center of the magnetic conduction section of the magnetic core rod is placed at the axial center of the inner cavity of the winding skeleton of the linear displacement sensor;

[0014] The signal cable of the linear displacement sensor passes through the reactor pressure vessel and is connected to the displacement signal and data processing system through a signal conditioner;

[0015] The gas regulation system is used to convey inert gas to the adjustment air chamber and the measurement air chamber and regulate the internal air pressure of the adjustment air chamber and the measurement air chamber.

[0016] Regarding the problem of the deficiency of the means and methods for measuring the fission gas release pressure of fuel elements under the harsh working conditions of high temperature, high pressure, and strong nuclear radiation in the existing nuclear reactor core in the prior art, the present invention provides a high-temperature resistant and radiation-resistant on-line measurement system for the fission gas release pressure of reactor fuel elements, which is applicable to the harsh working conditions inside the reactor, on-line measures the fission gas release pressure of fuel elements to evaluate the health status of fuel elements, and has good practicability, advancement, and broad market prospects. In a specific scheme, one end of the corrugated pipe is open and the other end is closed. A measurement air chamber is provided at one end of the corrugated pipe and is communicated with the fuel pellets. The fission gas generated by the fuel pellets will enter the measurement air chamber and push the other end of the corrugated pipe to expand and contract, thereby driving the synchronous displacement of the magnetic core rod; an adjustment air chamber is provided at the other end of the corrugated pipe, and inert gas is filled into the adjustment air chamber through a gas regulation device, thereby pushing the other end of the corrugated pipe to expand and contract and driving the synchronous displacement of the magnetic core rod; therefore, as the fission gas in the measurement air chamber increases, the charging amount of the inert gas is dynamically adjusted, and the displacement balance of the corrugated pipe is maintained, so that the fission gas release pressure P is calculated through the pressure of the filled inert gas; in addition, this device combines displacement signal to measure the displacement of the corrugated pipe, cooperates with gas dynamic regulation, keeps the corrugated pipe within the sensitive elastic limit, and improves the measurement accuracy. Among them, the nuclear fuel pellets and the fission gas release pressure measurement mechanism are coupled and installed in the fuel assembly. The fission gas release pressure measurement mechanism is respectively connected to a signal conditioner and a gas regulation system through armored signal cables and gas pipes. The signal conditioner connects a shielded signal cable to pass through the containment penetration to reach the multi-channel data processing and control unit and finally connect to the upper monitoring and analysis system; the gas pipe passes through the containment penetration to connect to the gas regulation system, and further connects to the measurement and control system through a communication cable to the upper monitoring and analysis system for gas regulation control and acquisition parameter processing.

[0017] According to a further solution, the fission gas release pressure measuring mechanism also includes a protective tube, a sealing flange and an armored cable sealing head, wherein the sealing flange is arranged at the top outlet of the reactor pressure vessel; the upper end of the outer sleeve is connected to the lower end of the protective tube, and the upper end of the protective tube is connected to the sealing flange; the signal cable of the linear displacement sensor and the air pipe of the gas regulating system both pass through the protective tube and exit the sealing flange; the armored cable sealing head is used to seal the armored signal cable passing through the sealing flange.

[0018] A further solution also includes a containment penetration piece, wherein the signal conditioner is connected to the displacement signal and data processing system via a shielded signal cable, and the shielded signal cable and the air pipe both pass through the containment penetration piece.

[0019] A further solution also includes a bellows head for sealing the other end of the bellows, and a connecting rod is fixed at the bellows head; the other end of the pressure-bearing sleeve is also provided with a column groove that matches the diameter of the connecting rod, and the connecting rod slides into the column groove at one end away from the bellows, and the magnetic core rod is arranged on the end of the connecting rod extending into the column groove.

[0020] In a further solution, one end of the bellows is sealed and fixed in the pressure casing by welding a fixed support ring.

[0021] In a further solution, the other end of the outer sleeve is provided with a cover plate for closing its end, and the inner side of the outer sleeve is also provided with a fixed support block for fixing the linear displacement sensor;

[0022] The gas pipe of the gas regulating system passes through the cover plate, the fixed support block and the pressure-bearing sleeve in sequence, and is communicated with the interior of the pressure-bearing sleeve.

[0023] In a further solution, the gas regulating device includes a high-pressure gas source bottle for conveying inert gas to the regulating gas chamber and the measuring gas chamber respectively, a tail gas tank connected to the exhaust outlet of the regulating gas chamber, and a collecting tank connected to the exhaust outlet of the measuring gas chamber; wherein the tail gas tank is used to cooperate with the high-pressure gas source bottle to dynamically adjust the gas pressure in the regulating gas chamber; the collecting tank is used to collect fission gas, which can be transported for component analysis.

[0024] In a further solution, the output end of the high-pressure gas source bottle is connected to a gas source buffer tank, and the high-pressure gas source bottle conveys inert gas to the regulating gas chamber and the measuring gas chamber through the gas source buffer tank; a pressure reducing valve is arranged between the high-pressure gas source bottle and the gas source buffer tank; wherein, the high-pressure gas source bottle is connected to the pressure reducing valve through a stainless steel metal pipeline, and the gas pressure can be reduced to the required air pressure through the pressure reducing valve; the pressure reducing valve is connected to the gas source buffer tank through a stainless steel metal pipeline, and the decompressed gas can be filled into the gas source buffer tank.

[0025] In a further solution, a first electric valve and a first gas mass flowmeter are sequentially arranged at the output end of the gas source buffer tank; a second electric valve is arranged between the output end of the first gas mass flowmeter and the regulating gas chamber; a third electric valve is arranged between the output end of the first gas mass flowmeter and the measuring gas chamber.

[0026] In a further solution, a fourth electric valve is arranged between the exhaust outlet of the measuring gas chamber and the collection tank; a fifth electric valve and a second gas mass flowmeter are sequentially arranged between the exhaust outlet of the regulating gas chamber and the tail gas tank.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] 1. The present invention provides an on-line measurement system for the fission gas release pressure of a high-temperature and radiation-resistant reactor fuel element. The gas release pressure measurement mechanism is composed of a bellows (expansion tube), a pressure-bearing sleeve, and a linear variable differential pressure sensor (LVDT). In the on-line measurement of gas pressure, the released fission gas is contained in the bellows, and the fission gas pressure is converted into the sum of the internal and external pressure differences after the bellows extends and the regulating gas pressure. The elongation amount of the bellows in the mechanism is detected by a linear variable differential pressure sensor (LVDT), and the fission gas pressure can be obtained by collecting the electrical signal of the linear variable differential pressure sensor without directly contacting the highly radioactive fission gas.

[0029] 2. The present invention provides an on-line measurement system for the fission gas release pressure of reactor fuel elements. A gas regulation system is provided, which forms a regulation gas chamber together with a bellows and a pressure-bearing casing. When the fission gas is released to a certain high pressure, the compression amount of the bellows approaches the elastic limit limit value. The gas regulation system can be used to increase the pressure in the regulation gas chamber and reduce the force on both sides of the bellows, so as to ensure that the bellows always effectively works within the compressible range, which can ensure that the device has a wider detection range and higher accuracy for fission gas within the elastic limit range of expansion and contraction, greatly reducing the volume of the bellows and meeting the installation and application scenarios in the narrow space inside the reactor. The purpose of setting the regulated air pressure and the bellows in this measuring mechanism is also to improve the response speed of the measurement of high-pressure gas. There is no need to frequently change the regulated air pressure to adapt to the fission gas pressure. The small-range fluctuation of the pressure can be monitored and displayed in real time through the expansion and contraction amount of the bellows, thereby improving the response speed and reaction sensitivity of the measuring mechanism to the change of fission gas pressure.

[0030] 3. The present invention provides an on-line measurement system for the fission gas release pressure of reactor fuel elements. The gas pressure measuring mechanism can achieve the effects of protecting the coil of the linear variable differential pressure sensor and preventing the leakage of fission gas. The magnetic core is placed in a pressure-bearing casing made of non-magnetic materials such as lead and tungsten to isolate the core from the coil. Considering the high radioactivity generated during the fission process, due to the existence of the fission gas chamber shell and the regulated gas chamber shell, radioactive particles and rays will be mostly confined in the fission gas chamber and the regulated gas chamber, thereby weakening the adverse effects of radioactivity on the linear variable differential pressure sensor. At the same time, based on abnormal conditions, once the bellows ruptures, the pressures on both sides of the bellows will be equal. At this time, the linear variable differential pressure sensor will have no output signal. At the same time, the fission gas will be confined and contained in the two gas chambers without leaking into the reactor interior. And considering the discharge of fission gas under abnormal conditions, one side of the regulated gas chamber is also connected to a tail gas storage device.

[0031] 4. The present invention provides an on-line measurement system for the fission gas release pressure of reactor fuel elements. The gas regulation system collects the displacement amount of the linear displacement sensor through a displacement signal and a data processing system, the gas pressure transmitter measures the feedback pressure, the flowmeter measures the feedback flow, and the controller in the control cabinet controls the opening degrees of the main gas path controller, the regulated intake controller, and the regulated outlet controller to drive the regulated intake electric valve and the regulated outlet electric valve, so as to realize the automatic balance adjustment of the gas pressures in the regulated pressure chamber and the measurement chamber and improve the on-line measurement accuracy of the fission gas pressure.

[0032] 5. The gas pressure measuring device provided by the present invention is applicable to the on-line measurement of the fission gas release pressure of the core fuel elements of research reactors and nuclear power reactors, and each component can meet the advantages of high temperature resistance, high pressure resistance, and anti-nuclear radiation. Description of the Drawings

[0033] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings. In the drawings:

[0034] Figure 1 Schematic diagram of the structure of an on-line measurement system according to an embodiment provided by the present invention;

[0035] Figure 2 Schematic diagram of the structure of a gas pressure measurement section according to an embodiment provided by the present invention;

[0036] Figure 3 Schematic diagram of the structure of a gas regulation system according to an embodiment provided by the present invention.

[0037] Markings in the drawings and corresponding component names:

[0038] 1. Fuel; 2. Fission gas release pressure measurement mechanism; 3. Gas pressure measurement section; 4. Pressure vessel; 5. Protection tube; 6. Sealing flange; 7. Armored cable seal head; 8. Gas pipe; 9. Armored signal cable; 10. Signal conditioner; 11. Working box; 12. Computer control system; 13. Shielded signal cable; 14. Containment penetration; 16. Gas regulation system; 17. Communication cable; 18. Network switching module; 19. Displacement signal and data processing system; 20. Upper monitoring and analysis system; 3-1. Outer sleeve; 3-2. Cover plate; 3-3. Linear displacement sensor; 3-4. Magnetically conductive core rod; 3-5. Connecting rod; 3-6. Pressure-bearing sleeve; 3-7. Bellows; 3-8. Bellows head; 3-9.1. Regulating gas pipe; 3-9.2. Measuring gas pipe; 3-10. Fixed support ring; 3-11. Fixed support block; 3-12. Armored signal wire; 3-13. Fuel cladding; 3-14. Fuel pellet; 3-15. Measuring gas chamber; 3-16. Regulating gas chamber; 16-1. High-pressure gas source bottle; 16-2. Pressure reducing valve; 16-3. Gas source buffer tank; 16-4. First electric valve; 16-5. Main gas path controller; 16-6. First gas mass flowmeter; 16-7. Regulating air intake controller; 16-8. Second electric valve; 16-9. Third electric valve; 16-10. Measuring air intake controller; 16-12. Second gas mass flowmeter; 16-13. Regulating air outlet controller; 16-14. Fifth electric valve; 16-15. Tail gas tank; 16-16. Fourth electric valve; 16-17. Measuring air outlet controller; 16-18. Collection tank; 16-19. Measuring control cabinet. Detailed implementation manners

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with embodiments and the accompanying drawings. The illustrative embodiments of the present invention and their descriptions are only used to explain the present invention and do not limit the present invention.

[0040] Embodiment 1:

[0041] This Embodiment 1 provides an on-line measurement system for the fission gas release pressure of a reactor fuel element. As Figures 1 - 3 shown, the system includes: a fission gas release pressure measurement mechanism 2, a displacement signal and data processing system 19, a gas regulation system 16, and an upper monitoring and analysis system 20. The nuclear fuel pellets 3-14 and the fission gas release pressure measurement mechanism 2 are coupled and installed in the fuel assembly. The pressure measurement mechanism is respectively connected to a signal conditioner 10 and a gas regulation system through an armored signal cable 3-12 and a gas pipe 8. The signal conditioner 10 is connected to a shielded signal cable 13, passes through a containment penetration 14, reaches a multi-channel data processing and control unit, and is finally connected to the upper monitoring and analysis system 20; the gas pipe 8 passes through the containment penetration 14 and is connected to the gas regulation system 16, and is further connected to a measurement and control system through a communication cable 17 to the upper monitoring and analysis system 20 for gas regulation control and acquisition parameter processing.

[0042] The fission gas release pressure measurement mechanism 2 includes: a gas pressure measurement section 3, a protection tube 5, a sealing flange 6, and an armored cable sealing head 7. The gas pressure measurement section 3 is located in the core active area of the reactor pressure vessel 4, the lower end is connected to the fuel assembly, the upper end is connected to the lower end of the test protection tube 5, the upper end of the protection tube 5 is connected to the sealing flange 6, and the sealing flange 6 is used to penetrate the armored cable sealing head 7; the armored signal cable 3-12 and the gas pipe 8 are arranged in the protection tube 5.

[0043] The described gas pressure measurement section 3 includes: an outer sleeve 3-1, a cover plate 3-2, a linear displacement sensor 3-3, a magnetic core rod 3-4, a connecting rod 3-5, a pressure-bearing sleeve 3-6, a high-pressure-resistant micro bellows 3-7, a bellows head 3-8, a regulating air pipe 3-9.1, a measuring air pipe 3-9.2, a fixed support ring 3-10, and a fixed support block 3-11. One end periphery of the high-pressure-resistant micro bellows 3-7 is welded and sealed to the inside of the pressure-bearing sleeve 3-6 through the fixed support ring 3-10, and the other end is connected to the connecting rod 3-5 after being sealed by the bellows head 3-8. The other end of the connecting rod 3-5 and the connecting magnetic core rod 3-4 are placed side by side inside the pressure-bearing sleeve 3-6. One end of the pressure-bearing sleeve 3-6 is sealed and welded to one end of the fuel cladding 3-13, and the other end is placed inside the winding skeleton cavity of the linear displacement sensor 3-3 after being sealed, ensuring that the center of the magnetic conduction section of the magnetic core rod 3-4 is at the axial center of the winding skeleton cavity of the linear displacement sensor 3-3. The linear displacement sensor 3-3 is fixedly installed inside the outer sleeve 3-1 through the fixed support block 3-11. The armored signal wire 3-12 of the linear displacement sensor 3-3 passes through the cover plate 3-2. One end of the outer sleeve 3-1 is welded and sealed by the cover plate 3-2 and then connected to the protection pipe 5. The air pipe 8 passes through the protection pipe 5, the cover plate 3-2, and the fixed support block 3-11 and is communicated with the pressure-bearing sleeve 3-6, forming a pressure-regulating air chamber with the outside of the high-pressure-resistant micro bellows 3-7 inside the pressure-bearing sleeve 3-6; the inside of the pressure-bearing sleeve 3-6 and the inside of the high-pressure-resistant micro bellows 3-7 form a measuring air chamber 3-15. The release of fission gas by the fuel pellets 3-14 causes the pressure in the measuring air chamber 3-15 to increase, and the high-pressure-resistant micro bellows 3-7 elongates due to the increase in internal pressure. The elongation of the bellows 3-7 is measured and output by the linear displacement sensor 3-3, and the fission gas release pressure can be measured online.

[0044] The described displacement signal and data processing system 19 includes an armored signal wire 3-12, a shielded signal cable, a signal conditioner 10, and a data processing unit. The armored signal wire 3-12 of the linear displacement sensor 3-3 is led out of the pressure vessel 4 through the cover plate 3-2, the protection pipe 5, the flange, and the sealing head and then connected to the signal conditioner 10. After the signal conditioner 10 conditions the displacement signal into a 4-20 mA standard signal, it is connected to the data processing unit for signal acquisition and processing, and the data is uploaded to the upper monitoring and analysis system 20 for display and storage.

[0045] The described gas regulation system 16 includes a high-pressure gas source bottle 16-1, a pressure reducing valve 16-2, a gas source buffer tank 16-3, a first electric valve 16-4, a main gas path controller 16-5, a first gas mass flowmeter 16-6, a regulating intake controller 16-7, a second electric valve 16-8, a third electric valve 16-9, a measuring intake controller 16-10, a second gas mass flowmeter 16-12, a regulating outlet controller 16-13, a fifth electric valve 16-14, a tail gas tank 16-15, a fourth electric valve 16-16, a measuring outlet controller 16-17, a collection tank 16-18, and a measuring control cabinet 16-19. The gas source in the high-pressure gas source bottle 16-1 selects an in-core non-activated inert gas, and its outlet is connected to the pressure reducing valve 16-2 and then connected to the gas source buffer tank 16-3 through a pipeline to reduce the high-pressure gas to the gas source buffer tank 16-3. A pressure gauge (PT02) is installed on the gas source buffer tank 16-3, and the desired gas source pressure value can be obtained from the gas source bottle through the pressure reducing valve 16-2. The gas source buffer tank 16-3 is also connected to the first electric valve 16-4 through a pipeline. The first electric valve 16-4 controls the opening degree to regulate the intake gas flow through the main gas path controller 16-5. After being connected to the first gas mass flowmeter 16-6 through a pipeline, it is divided into two gas paths. One path is connected to the regulating second electric valve 16-8 through a pipeline and the opening and closing of the valve is controlled by the regulating intake controller 16-7. Then it is connected to the gas pipe 8 of the fission gas release pressure measuring mechanism 2 and the regulating gas pipe 3-9.1 of the gas pressure measuring section 3 through a pipeline. At the same time, it is connected to the regulating fifth electric valve 16-14 through a pipeline and the opening degree of the valve is controlled by the regulating outlet controller 16-13. After passing through the second gas mass flowmeter 16-12, it is connected to the tail gas tank 16-15 through a pipeline. The other path is connected to the third electric valve 16-9 through a pipeline and the opening and closing of the valve is controlled by the measuring intake controller 16-10. Then it is connected to the gas pipe 8 of the fission gas release pressure measuring mechanism 2 and the measuring gas pipe 3-9.2 of the gas pressure measuring section 3 through a pipeline. At the same time, it is connected to the fourth electric valve 16-16 through a pipeline and the opening degree of the valve is controlled by the measuring outlet controller 16-17. Then it is connected to the collection tank 16-18 through a pipeline. A gas pressure transmitter (PT03) is installed on the pipeline behind the second electric valve 16-8 to monitor the gas pressure in the regulating gas chamber 3-16 of the gas pressure measuring section 3. A gas pressure transmitter (PT04) is installed on the pipeline behind the third electric valve 16-9 to monitor the gas pressure in the measuring gas chamber 3-15 of the gas pressure measuring section 3. A gas pressure transmitter (PT05) is installed on the pipeline of the tail gas tank 16-15 to monitor the regulating tail gas pressure.The control signals of the main gas path controller 16-5, the regulating intake air controller 16-7, the measuring intake air controller 16-10, the regulating outlet air controller 16-13, and the measuring outlet air controller 16-17 are operated by commands from the upper monitoring and analysis system 20 and output by the controller in the measuring control cabinet 16-19. The first gas mass flowmeter 16-6 and the second gas mass flowmeter 16-12 collect the gas flow rate. The gas pressure transmitters (PT01, PT02, PT03, PT04, PT05) collect the gas pressure, which is collected by the collection unit in the measuring control cabinet 16-19 and then sent to the upper monitoring and analysis system 20 for parameter processing. The measuring tail gas collection tank 16-18 is used to store the released activated fission gas for subsequent component analysis.

[0046] The gas regulation system 16 collects the displacement of the linear displacement sensor 3-3 through the displacement signal and data processing system 19, and the gas pressure transmitters (PT01, PT02, PT03, PT04, PT05) measure the pressure. As feedback, the controller in the control cabinet controls the opening degrees of the second electric valve 16-8 and the fifth electric valve 16-14 by driving the main gas path controller 16-5, the regulating intake air controller 16-7, and the regulating outlet air controller 16-13, so as to realize the automatic balance adjustment of the gas pressure in the pressure regulating gas chamber and the measuring gas chamber 3-15 and improve the online measurement accuracy of the fission gas pressure.

[0047] Embodiment 2:

[0048] This Embodiment 2 is further optimized on the basis of Embodiment 1. As Figure 1 shown, a method for online measurement of the fission gas release pressure of fuel elements is provided, including the following processes:

[0049] Process 1: The high-pressure gas source bottle 16-1 is a general standard 50L high-purity helium gas bottle. The pressure in the helium gas bottle is fed back by the gas pressure transmitter PT01. It is necessary to ensure that the pressure of the high-pressure gas source bottle 16-1 is greater than 10 Mpa. If it is less than 10 Mpa, a new gas bottle needs to be replaced in time;

[0050] Process 2: Connect the high-pressure gas source bottle 16-1 to the pressure reducing valve 16-2 through a stainless steel metal pipeline, and reduce the gas pressure to the required air pressure through the pressure reducing valve 16-2;

[0051] Process 3: The pressure reducing valve 16-2 is connected to the gas source buffer tank 16-3 through a stainless steel metal pipeline, and the reduced-pressure gas is filled into the gas source buffer tank 16-3. The reduced-pressure gas in the tank can be fed back in real time by the gas pressure transmitter PT02.

[0052] Process 4: The gas after pressure reduction passes through the metal gas pipe 8 and is precisely controlled and regulated in terms of gas flow by the first electric valve 16-4 and the first gas mass flowmeter 16-6, and then the regulated gas volume can be obtained.

[0053] Process 5: According to the gas regulation requirements, the regulated gas can respectively enter the regulation gas chamber 3-16 of the fission gas measurement tooling through the control of the second electric valve 16-8 to achieve negative regulation of the regulated gas pressure, or enter the measurement gas chamber 3-15 of the fission gas measurement tooling through the control of the third electric valve 16-9.

[0054] Process 6: The regulation gas chamber 3-16 of the fission gas measurement tooling is led out of the reactor through a stainless steel metal pipe, passes through the fifth electric valve 16-14 and the second gas mass flowmeter 16-12, and then is connected to the tail gas tank 16-15, and negative regulation of the regulated gas pressure can be achieved.

[0055] Process 7: The tail gas pressure collected by the tail gas tank 16-15 is fed back by the gas pressure transmitter PT04.

[0056] Process 8: The measurement gas chamber 3-15 of the fission gas measurement tooling is led out of the reactor through a stainless steel metal pipe, passes through the fourth electric valve 16-16, and then is connected to the collection tank 16-18, and the collected gas can be transported for component analysis.

[0057] Process 9: The subsystem composed of the high-pressure gas source bottle 16-1, the gas pressure transmitter PT01, the pressure reducing valve 16-2, the gas source buffer tank 16-3, the gas pressure transmitter PT01, the first electric valve 16-4, the first gas mass flowmeter 16-6, and the second electric valve 16-8 is arranged in the non-radioactive process room. The subsystem composed of the fifth electric valve 16-14, the second gas mass flowmeter 16-12, the tail gas tank 16-15, the fourth electric valve 16-16, and the collection tank 16-18 is arranged in the radioactive process room outside the pressure vessel 4, while the fission gas measurement tooling is coupled and installed inside the pressure vessel 4 to achieve safety zoning management.

[0058] Process 10: The pressure seal boundary of the regulation gas chamber 3-16 of the fission gas measurement tooling is the pressure-bearing sleeve 3-6 and the bellows 3-7.

[0059] Process 11: The pressure seal boundary of the measurement gas chamber 3-15 of the fission gas measurement tooling is the pressure-bearing sleeve 3-6, the bellows 3-7, and the fuel cladding 3-13.

[0060] Process 12: The pressure changes in the regulating chamber 3-16 and the measuring chamber 3-15 of the fission gas measurement tooling will cause the bellows 3-7 to expand and contract, which in turn causes the magnetostrictive core rod 3-4 connected to the bellows 3-7 in the pressure-bearing sleeve 3-6 to move. Finally, the magnetic field of the coil of the linear displacement sensor 3-3 is cut, resulting in a change in the induced current, which is collected through signal cables.

[0061] Through the above process, an on-line measurement method can be formed. The method steps include:

[0062] Step 1: Close the first electric valve 16-4, the second electric valve 16-8, the third electric valve 16-9, the fourth electric valve 16-16, the fifth electric valve 16-14, and set the first gas mass flowmeter 16-6 and the second gas mass flowmeter 16-12 to 0.

[0063] Step 2: Record the pressure of the gas pressure transmitter PT01 as P2, the pressure of the gas pressure transmitter PT03 as P 11 , the pressure of the gas pressure transmitter PT04 as P 18 , and the linear displacement sensor 3-3 measures the displacement of the bellows 3-7 as V.

[0064] Step 3: Adjust the pressure after the pressure reducing valve 16-2 to 2 Mpa, adjust the first electric valve 16-4 to fill the gas source buffer tank 16-3 with the reduced-pressure gas, and observe that the pressure of the gas pressure transmitter PT01 remains at 2 Mpa as P2.

[0065] Step 4: As the released fission gas increases, when V increases to the threshold value V a , (V a is the elongation displacement corresponding to the fission gas pressure reaching a within the sensitive elastic range of the bellows 3-7), open the first electric valve 16-4, set the flow rate of the first mass flowmeter to 5 mL / min, control the second electric valve 16-8, and slowly fill the regulating chamber 3-16 of the fission gas measurement tooling with helium.

[0066] Step 5: Observe the displacement V of the bellows 3-7 measured by the linear displacement sensor 3-3. When V decreases to 0, close the second electric valve 16-8 and the first electric valve 16-4, and set the flow rate of the first gas mass flowmeter 16-6 to 0.

[0067] Step 6: If the measured displacement V of the bellows 3-7 becomes negative, the flow rate of the second gas mass flowmeter 16-12 can be set to 2 mL / min, and the fifth electric valve 16-14 is controlled to slowly release the helium in the regulating chamber 3-16 to the tail gas tank 16-15.

[0068] Step 7: Repeat Step 5 and Step 6 to dynamically adjust the pressure in the regulating air chamber 3-16, so that the displacement V of the bellows 3-7 is 0. Close the first electric valve 16-4, the second electric valve 16-8, the third electric valve 16-9, the fourth electric valve 16-16, the fifth electric valve 16-14, and set the first gas mass flowmeter 16-6 and the second gas mass flowmeter 16-12 to 0. Record the pressure of the gas pressure transmitter PT03 as P 12 ;

[0069] Step 8: Adjust the pressure after the pressure reducing valve 16-2 to 4 Mpa, and fill the gas source buffer tank 16-3 with the reduced-pressure gas. Observe that the pressure of the gas pressure transmitter PT01, P2, remains at 4 Mpa;

[0070] Step 9: Repeat Step 4 to Step 7, and record the pressure of the gas pressure transmitter PT03 as P 13 ;

[0071] Step 10: Adjust the pressure after the pressure reducing valve 16-2 to 6 Mpa, and fill the gas source buffer tank 16-3 with the reduced-pressure gas. Observe that the pressure of the gas pressure transmitter PT01, P2, remains at 6 Mpa;

[0072] Step 11: Repeat Step 4 to Step 7, and record the pressure of the gas pressure transmitter PT03 as P 14 ;

[0073] Step 12: Adjust the pressure after the pressure reducing valve 16-2 to 8 Mpa, and fill the gas source buffer tank 16-3 with the reduced-pressure gas. Observe that the pressure of the gas pressure transmitter PT01, P2, remains at 8 Mpa;

[0074] Step 13: Repeat Step 4 to Step 7, and record the pressure of the gas pressure transmitter PT03 as P 15 ;

[0075] Step 14: Adjust the pressure after the pressure reducing valve 16-2 to 10 Mpa, and fill the gas source buffer tank 16-3 with the reduced-pressure gas. Observe that the pressure of the gas pressure transmitter PT01, P2, remains at 10 Mpa;

[0076] Step 15: Repeat Step 4 to Step 7, and record the pressure of the gas pressure transmitter PT03 as P 16 ;

[0077] Step 16: If the gas pressure is too high and needs to be released and collected, adjust the fourth electric valve 16-16 to collect the gas into the collection tank 16-18;

[0078] Step 17: When V decreases to the threshold value V b (V bWhen the fission gas pressure is less than the regulating gas b within the sensitive elastic range of the bellows 3-7 (corresponding compression displacement), close the fourth electric valve 16-16, set the flow rate of the first gas mass flowmeter 16-6 to 5 mL / min, and control the fifth electric valve 16-14 to slowly release the helium gas in the regulating gas chamber 3-16 to the tail gas tank 16-15 to make the displacement V of the bellows 3-7 equal to 0;

[0079] Step 18: Repeat Step 16 to Step 17 to relieve the gas pressure and collect the released fission gas;

[0080] The release pressure P of the fission gas is the sum of the pressures of the multi-stage pressure regulating measurement gas pressure transmitter PT03, that is, P = P 11 +P 12 +P 13 +P 14 +P 15 +P 16 ;

[0081] In the above steps, the gas pressure measured by the gas pressure transmitter PT03 is the inert gas helium that is not easily activated, and the pressure measurement position is at the high-pressure end outside the reactor. The pipeline is thin and long, and the activated gas in the reactor will not diffuse outside the reactor, reducing the radioactive risk of personnel operation;

[0082] The described measurement process combines the linear displacement signal to measure the displacement of the bellows 3-7, and cooperates with the gas dynamic regulation to keep the bellows 3-7 within the sensitive elastic limit, improving the measurement accuracy.

[0083] The above specific implementation manners have further detailed the purpose, technical solution and beneficial effects of the present invention. It should be understood that the above are only the specific implementation manners of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An on-line measurement system for the fission gas release pressure of a reactor fuel element, characterized in that, It comprises a fission gas release pressure measuring mechanism (2), a displacement signal and data processing system (19) and a gas regulating system (16); The fission gas release pressure measuring mechanism (2) comprises a gas pressure measuring section (3) located inside the reactor pressure vessel (4); the gas pressure measuring section (3) is located in the core active area of ​​the reactor pressure vessel (4); The gas pressure measuring section (3) comprises an outer sleeve (3-1), the lower end of the outer sleeve (3-1) being fixed to the fuel cladding (3-13); a pressure sleeve (3-6) and a linear displacement sensor (3-3) are fixed in sequence from one end to the other end of the inner side of the outer sleeve (3-1); the pressure sleeve (3-6) is open toward one end of the fuel cladding (3-13) and is in communication with the fuel pellet (3-14); A bellows (3-7) is fixed in the pressure-bearing sleeve (3-6), and the pressure-bearing sleeves (3-6) at both ends of the bellows (3-7) are respectively provided with a regulating air chamber (3-16) and a measuring air chamber (3-15), and one end of the bellows (3-7) is open toward the measuring air chamber (3-15), and the fuel pellets (3-14) are connected to the inside of the bellows (3-7) in sequence through the opening at one end of the pressure-bearing sleeve (3-6), the measuring air chamber (3-15), the opening at one end of the bellows (3-7), and the inside of the bellows (3-7); A magnetic core rod (3-4) is fixed to the other end of the bellows (3-7), the magnetic core rod (3-4) passes through the other end of the pressure-bearing sleeve (3-6) and extends into the inner cavity of the winding frame of the linear displacement sensor (3-3), and the center of the magnetic section of the magnetic core rod (3-4) is placed at the axial center of the inner cavity of the winding frame of the linear displacement sensor (3-3); The signal cable (9) of the linear displacement sensor (3-3) passes through the reactor pressure vessel (4) and is connected to the displacement signal and data processing system (19) through a signal conditioner (10); The gas regulating system (16) is used to transport inert gas to the regulating gas chamber (3-16) and the measuring gas chamber (3-15), and to regulate the internal gas pressure of the regulating gas chamber (3-16) and the measuring gas chamber (3-15).

2. The on-line measurement system for the fission gas release pressure of a reactor fuel element according to claim 1, characterized in that, The fission gas release pressure measuring mechanism (2) further comprises a protective tube (5), a sealing flange (6) and an armored cable sealing head (7); the sealing flange (6) is arranged at the top outlet of the reactor pressure vessel (4); the upper end of the outer sleeve (3-1) is connected to the lower end of the protective tube (5), and the upper end of the protective tube (5) is connected to the sealing flange (6); the signal cable (9) of the linear displacement sensor (3-3) and the gas pipe (8) of the gas regulating system (16) both pass through the protective tube (5) and out of the sealing flange (6); the armored cable sealing head (7) is used to seal the armored signal cable (9) passing through the sealing flange (6).

3. An on-line measurement system for the fission gas release pressure of a reactor fuel element according to claim 2, characterized in that, It further includes a containment penetration (14). The signal conditioner (10) is connected to the displacement signal and data processing system (19) through a shielded signal cable (13). Both the shielded signal cable (13) and the air pipe (8) pass through the containment penetration (14).

4. An on-line measurement system for the fission gas release pressure of a reactor fuel element according to claim 1, characterized in that, It further includes a bellows head (3-8) for sealing the other end of the bellows (3-7). A connecting rod (3-5) is fixed at the bellows head (3-8). A column groove adapted to the diameter of the connecting rod (3-5) is further formed at the other end of the pressure-bearing sleeve (3-6). The end of the connecting rod (3-5) away from the bellows (3-7) slides into the column groove, and the magnetic conductive core rod (3-4) is arranged at the end of the connecting rod (3-5) extending into the column groove.

5. An on-line measurement system for the fission gas release pressure of a reactor fuel element according to claim 1, characterized in that, One end of the bellows (3-7) is welded and sealed in the pressure-bearing sleeve (3-6) through a fixed support ring (3-10).

6. An on-line measurement system for the fission gas release pressure of a reactor fuel element according to claim 1, characterized in that, The other end of the outer sleeve (3-1) is provided with a cover plate (3-2) for closing its own end. A fixed support block (3-11) for fixing the linear displacement sensor (3-3) is further arranged inside the outer sleeve (3-1). The air pipe (8) of the gas regulation system (16) sequentially passes through the cover plate (3-2), the fixed support block (3-11) and the pressure-bearing sleeve (3-6), and is in internal communication with the pressure-bearing sleeve (3-6).

7. An on-line measurement system for the fission gas release pressure of a reactor fuel element according to claim 1, characterized in that The gas regulation system includes a high-pressure gas source bottle (16-1) for respectively supplying inert gas to the regulation gas chamber (3-16) and the measurement gas chamber (3-15), a tail gas tank (16-15) for connecting to the exhaust outlet of the regulation gas chamber (3-16), and a collection tank (16-18) for connecting to the exhaust outlet of the measurement gas chamber (3-15).

8. An on-line measurement system for the fission gas release pressure of a reactor fuel element according to claim 7, characterized in that, The output end of the high-pressure gas source bottle (16-1) is connected with a gas source buffer tank (16-3). The high-pressure gas source bottle (16-1) supplies inert gas to the regulation gas chamber (3-16) and the measurement gas chamber (3-15) through the gas source buffer tank (16-3). A pressure reducing valve (16-2) is arranged between the high-pressure gas source bottle (16-1) and the gas source buffer tank (16-3).

9. An on-line measurement system for the fission gas release pressure of a reactor fuel element according to claim 8, characterized in that, A first electric valve (16-4) and a first gas mass flowmeter (16-6) are sequentially arranged at the output end of the gas source buffer tank (16-3). A second electric valve (16-8) is arranged between the output end of the first gas mass flowmeter (16-6) and the regulation gas chamber (3-16). A third electric valve (16-9) is arranged between the output end of the first gas mass flowmeter (16-6) and the measurement gas chamber (3-15).

10. An on-line measurement system for the fission gas release pressure of a reactor fuel element according to claim 9, characterized in that, A fourth electric valve (16-16) is arranged between the exhaust outlet of the measurement gas chamber (3-15) and the collection tank (16-18). A fifth electric valve (16-14) and a second gas mass flowmeter (16-12) are sequentially arranged between the exhaust outlet of the regulation gas chamber (3-16) and the tail gas tank (16-15).

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