An online measuring device and method for the release pressure of fission gas of fuel element

Abstract

The present invention discloses an online measuring device and method for the release pressure of fission gas of fuel elements, including a fission gas measuring tool arranged in a pressure vessel and a gas regulating device arranged outside the pressure vessel; the fission gas measuring tool includes an outer sleeve; a pressure-bearing 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; a bellows is fixed in the pressure-bearing sleeve, and the pressure-bearing sleeves at both ends of the bellows are respectively provided with a regulating gas chamber and a measuring gas chamber, and the fuel core block is connected to the inside of the bellows; a magnetically conductive core rod is fixed at the other end of the bellows; the gas regulating device is used to transport inert gas to the regulating gas chamber and the measuring gas chamber. By using a displacement sensor combined with a bellows for measurement, the problem that the fission gas pressure of the existing reactor fuel is difficult to measure online can be solved, the economic efficiency and safety of the reactor operation can be improved, and 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 measuring operating behavior parameters of reactor and research reactor core fuel elements, and in particular to an online measuring device and method for the release pressure of fission gas of fuel elements. Background Art

[0002] During the operation of the reactor, the nuclear fuel will undergo a chain fission reaction and produce fission products, among which the most obvious is the release of fission gas. The fuel cladding is generally a closed structure. The internal pellets produce a large amount of fission gas, which will have a certain impact on the fuel and cladding, causing the fuel elements to swell to a certain extent or even break. The increase in swelling will cause the interaction between the fuel cladding to become stronger, the coolant flow path will change, and the operation risk of the fuel elements in the reactor will increase. In view of this, it is extremely important and valuable to measure the release pressure of nuclear fuel fission gas during the operation of the reactor.

[0003] The measurement of fission gas is divided into fission gas pressure measurement and fission gas composition measurement. The conventional method for analyzing fission gas composition is sampling method, which requires the fission gas to be led out of the reactor for analysis, and the integrity of the cladding structure must be guaranteed. Therefore, the measurement of fission gas pressure is the focus of consideration during operation. Summary of the invention

[0004] The present invention aims to solve the deficiencies of the prior art and to provide an on-line measuring device and method for the fission gas release pressure of fuel elements. By adopting a displacement sensor in combination with a bellows for measurement, the problem that the fission gas pressure of existing reactor fuel is difficult to measure on-line 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.

[0005] The present invention is achieved through the following technical solutions:

[0006] An online measuring device for the release pressure of fission gas of a fuel element, comprising a fission gas measuring tool arranged in a pressure vessel and a gas regulating device arranged outside the pressure vessel;

[0007] The fission gas measurement tooling comprises an outer sleeve, one 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 toward one end of the fuel cladding and is connected to the fuel pellets;

[0008] A bellows is fixed in the pressure-bearing sleeve, and the pressure-bearing sleeves at both ends of the bellows are respectively provided with a regulating air chamber and a measuring air chamber, and one end of the bellows is open toward the measuring air chamber, and the fuel pellets are connected in sequence through the opening at one end of the pressure-bearing sleeve, the measuring air chamber, the opening at one end of the bellows, and the interior of the bellows;

[0009] A magnetic conductive core rod is fixed to the other end of the bellows, the magnetic conductive core rod passes through the other end of the pressure-bearing sleeve and extends into the inner cavity of the linear displacement sensor winding frame, and the center of the magnetic conductive section of the magnetic conductive core rod is placed at the axial center of the inner cavity of the linear displacement sensor winding frame;

[0010] The gas regulating device is used to transport inert gas to the regulating gas chamber and the measuring gas chamber, and to regulate the internal gas pressure of the regulating gas chamber and the measuring gas chamber.

[0011] With respect to the problem in the prior art that the existing reactor fuel fission gas pressure is difficult to measure online, the present invention provides an online measuring device for the fission gas release pressure of a fuel element, which uses a displacement sensor in combination with a bellows for measurement; as the gas release pressure increases, the bellows is compressed, and an induction signal is further generated in the displacement sensor to obtain the expansion and contraction amount of the bellows, and the pressure of the internal gas can be inferred, and the pressure of the fission gas can be obtained by combining the elastic force of the bellows and the pressure of the internal gas; at the same time, a set of fission gas pressure measurement process methods are formed, which are suitable for harsh working conditions in the reactor, and the fission gas release pressure of the fuel element is measured online to evaluate the economy and safety of the reactor operation, as well as the advancement of the new fuel research and development process, and has broad market prospects. In the specific scheme, one end of the bellows is open and the other end is closed. A measuring gas chamber is provided at one end of the bellows and is connected to the fuel core block. The fission gas generated by the fuel core block will enter the measuring gas chamber and push the other end of the bellows to expand and contract, thereby driving the magnetic core rod to synchronously displace; an adjusting gas chamber is provided at the other end of the bellows, and inert gas is filled into the adjusting gas chamber through a gas regulating device, thereby pushing the other end of the bellows to expand and contract, and driving the magnetic core rod to synchronously displace; therefore, as the fission gas in the measuring gas chamber increases, the filling amount of the inert gas is dynamically adjusted, and the displacement balance of the bellows is maintained, thereby calculating the fission gas release pressure P through the pressure of the filled inert gas; in addition, the device combines the displacement signal to measure the displacement of the bellows, cooperates with the dynamic adjustment of the gas, keeps the bellows within the sensitive elastic limit, and improves the measurement accuracy.

[0012] 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.

[0013] 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 transports inert gas to the regulating gas chamber and the measuring gas chamber through the gas source buffer tank; a pressure reducing valve and a first electric valve are sequentially arranged between the high-pressure gas source bottle and the gas source buffer tank; 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 first electric valve through a stainless steel metal pipeline, and the gas source buffer tank can be filled with the reduced pressure gas by opening the first electric valve.

[0014] In a further solution, a second electric valve and a first gas mass flow meter are sequentially arranged at the output end of the gas source buffer tank; wherein the decompressed gas passes through the metal gas pipe through the second electric valve and the first gas mass flow meter to accurately control and adjust the gas flow, thereby obtaining the adjusted gas volume.

[0015] In a further solution, a third electric valve is provided between the output end of the first gas mass flow meter and the regulating gas chamber; and a fourth electric valve is provided between the output end of the first gas mass flow meter and the measuring gas chamber.

[0016] In a further solution, a fifth electric valve is provided between the exhaust outlet of the measuring air chamber and the collecting tank; a sixth electric valve and a second gas mass flow meter are provided in sequence between the exhaust outlet of the regulating air chamber and the tail gas tank.

[0017] In a further solution, the high-pressure gas source bottle, the gas source buffer tank, the output end of the third electric valve, the output end of the fourth electric valve and the tail gas tank are all provided with pressure transmitters.

[0018] A further solution is a measurement method for an online measurement device for measuring the release pressure of fission gas of a fuel element, comprising the following steps:

[0019] S1: measuring the initial displacement of the bellows and the initial pressure value in the regulating air chamber;

[0020] S2: As the release of fission gas from the fuel pellets increases, the displacement V of the bellows measured by the linear displacement sensor increases to V a When the pressure behind the pressure reducing valve is adjusted, the first electric valve is opened, and the regulating air chamber is filled with inert gas; the V a is the corresponding elongation displacement when the fission gas pressure reaches a within the sensitive elastic range of the bellows;

[0021] S3: When the displacement V of the bellows measured by the linear displacement sensor decreases to the initial displacement 0, the pressure value in the regulating air chamber at this time is recorded;

[0022] S4: repeating steps S2 to S3, and gradually increasing the pressure behind the pressure reducing valve, and recording the pressure value in the regulating air chamber each time when the displacement V of the bellows is reduced to the initial displacement 0;

[0023] S5: The fission gas release pressure P is obtained by adding the initial pressure value in the regulating gas chamber and the pressure value in the regulating gas chamber recorded each time.

[0024] In a further embodiment, step S3 further comprises the following sub-steps:

[0025] When the displacement V of the bellows becomes a negative value, the sixth electric valve between the exhaust outlet of the regulating air chamber and the tail gas tank is opened to release inert gas into the tail gas tank until the displacement V of the bellows becomes 0.

[0026] A further solution, when the fission gas released by the fuel pellets is too high, further comprises the following steps:

[0027] S6: when the fission gas released by the fuel pellets is too high, opening the fifth electric valve between the exhaust outlet of the measuring gas chamber and the collecting tank to release the fission gas into the collecting tank;

[0028] S7: When the displacement V of the bellows decreases to the threshold value V b , close the fifth electric valve; control the sixth electric valve to release the inert gas in the regulating air chamber to the tail gas tank until the displacement V of the bellows becomes 0; V b It is the corresponding compression displacement when the fission gas pressure is less than the regulating gas b within the sensitive elastic range of the bellows;

[0029] S8: Repeat steps S6 and S7 to release the gas pressure and collect the released fission gas.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] 1. The present invention provides an online measurement device and method for the fission gas release pressure of a fuel element, which uses a displacement sensor combined with a bellows for measurement; as the gas release pressure increases, the bellows is compressed, and an induction signal is further generated in the displacement sensor to obtain the expansion and contraction amount of the bellows, and the pressure of the internal gas can be inferred, and the pressure of the fission gas can be obtained by combining the elastic force of the bellows and the pressure of the internal gas; at the same time, a set of fission gas pressure measurement process methods are formed, which are suitable for harsh working conditions in reactors, and can measure the fission gas release pressure of fuel elements online to evaluate the economy and safety of reactor operation, as well as the advancement of the new fuel research and development process, and have broad market prospects.

[0032] 2. The present invention provides an online measurement device and method for the fission gas release pressure of a fuel element. A gas regulating system is provided to form a regulating gas chamber with a bellows and a pressure-bearing casing. When the fission gas is released to a certain high pressure, the compression of the bellows is close to the elastic limit. The gas regulating system can be used to increase the pressure in the regulating gas chamber and reduce the force on the inner and outer sides of the bellows, thereby ensuring that the bellows always effectively works within the compressible range. The bellows can be guaranteed to be within the telescopic elastic limit, increase the detection range and accuracy of the device for fission gas, and greatly reduce the volume of the bellows, which is suitable for installation and application scenarios in narrow spaces within the reactor.

[0033] 3. The present invention provides an online measurement device and method for the fission gas release pressure of a fuel element. The subsystem of the gas regulating device is arranged in the radioactive process room outside the pressure vessel, and the fission gas measurement tooling is coupled with the fuel element and installed inside the pressure vessel to achieve safe zoning management and avoid hazards caused by radioactive products. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0035] Figure 1 A connection diagram of an online measurement device according to an embodiment of the present invention;

[0036] Figure 2 A schematic structural diagram of a fission gas measurement tooling provided in one embodiment of the present invention.

[0037] Marks and corresponding parts names in the attached drawings:

[0038] 1. High-pressure gas source bottle; 2. First pressure transmitter; 3. Pressure reducing valve; 4. First electric valve; 5. Gas source buffer tank; 6. Second pressure transmitter; 7. Second electric valve; 8. First gas mass flow meter; 9. Third electric valve; 10. Fourth electric valve; 11. Third pressure transmitter; 12. Fission gas measurement tooling; 13. Fifth electric valve; 14. Collection tank; 15. Sixth electric valve; 16. Second gas mass flow meter; 17. Tail gas tank; 18. Fourth pressure transmitter; 12-1. Fuel core block; 12-2. Fuel cladding; 12-3. Bellows; 12-4. Pressure casing; 12-5. Outer casing; 12-6. Linear displacement sensor; 12-7. Signal cable; 12-8. Adjusting gas chamber; 12-9. Measuring gas chamber; 12-10. Permeable core rod. DETAILED DESCRIPTION

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0040] Embodiment 1:

[0041] This embodiment 1 provides an online measuring device for the release pressure of fission gas of a fuel element, such as Figure 2 As shown, it includes a fission gas measuring tool 12 arranged in the pressure vessel and a gas regulating device arranged outside the pressure vessel;

[0042] The fission gas measurement tool 12 includes an outer sleeve 12-5, one end of which is fixed to the fuel cladding 12-2; a pressure sleeve 12-4 and a linear displacement sensor 12-6 are fixed in sequence from one end to the other end of the inner side of the outer sleeve 12-5; the pressure sleeve 12-4 opens toward one end of the fuel cladding 12-2 and is connected to the fuel pellet 12-1;

[0043] A bellows 12-3 is fixed in the pressure-bearing sleeve 12-4, and the pressure-bearing sleeves 12-4 at both ends of the bellows 12-3 are respectively provided with a regulating air chamber 12-8 and a measuring air chamber 12-9, and one end of the bellows 12-3 is open toward the measuring air chamber 12-9, and the fuel pellets 12-1 are connected to the inside of the bellows 12-3 in sequence through the opening at one end of the pressure-bearing sleeve 12-4, the measuring air chamber 12-9, the opening at one end of the bellows 12-3, and the inside of the bellows 12-3;

[0044] A magnetic core rod 12-10 is fixed to the other end of the bellows 12-3. The magnetic core rod 12-10 passes through the other end of the pressure-bearing sleeve 12-4 and extends into the inner cavity of the winding frame of the linear displacement sensor 12-6. The center of the magnetic section of the magnetic core rod 12-10 is placed at the axial center of the inner cavity of the winding frame of the linear displacement sensor 12-6.

[0045] The gas regulating device is used to transport inert gas to the regulating gas chamber 12-8 and the measuring gas chamber 12-9, and to regulate the internal gas pressure of the regulating gas chamber 12-8 and the measuring gas chamber 12-9.

[0046] With respect to the problem in the prior art that the existing reactor fuel fission gas pressure is difficult to measure online, the present invention provides an online measuring device for the fission gas release pressure of a fuel element, which uses a displacement sensor in combination with a bellows 12-3 for measurement; as the gas release pressure increases, the bellows 12-3 is compressed, and an induction signal is further generated in the displacement sensor to obtain the expansion and contraction amount of the bellows 12-3, and the pressure of the internal gas can be inferred, and the pressure of the fission gas can be obtained by combining the elastic force of the bellows 12-3 and the pressure of the internal gas; at the same time, a set of fission gas pressure measurement process methods are formed, which are suitable for harsh working conditions in the reactor, and the fission gas release pressure of the fuel element is measured online to evaluate the economy and safety of the reactor operation, as well as the advancement of the new fuel research and development process, and has broad market prospects. In the specific scheme, one end of the bellows 12-3 is open, and the other end is closed. A measuring gas chamber 12-9 is provided at one end of the bellows 12-3 and is connected to the fuel pellet 12-1. The fission gas generated by the fuel pellet 12-1 will enter the measuring gas chamber 12-9 and push the other end of the bellows 12-3 to expand and contract, thereby driving the magnetic core rod 12-10 to move synchronously; a regulating gas chamber 12-8 is provided at the other end of the bellows 12-3, and an inert gas is filled into the regulating gas chamber 12-8 through a gas regulating device, so as to The other end of the bellows 12-3 is pushed to expand and contract, and the magnetic core rod 12-10 is driven to move synchronously; therefore, as the fission gas in the measuring gas chamber 12-9 increases, the filling amount of the inert gas is dynamically adjusted, and the displacement balance of the bellows 12-3 is maintained, so that the fission gas release pressure P is calculated by the pressure of the filled inert gas; in addition, the device combines the displacement signal to measure the displacement of the bellows 12-3, cooperates with the dynamic adjustment of the gas, keeps the bellows 12-3 within the sensitive elastic limit, and improves the measurement accuracy.

[0047] In some possible embodiments, the gas regulating device includes a high-pressure gas source bottle 1 for conveying inert gas to the regulating gas chamber 12-8 and the measuring gas chamber 12-9 respectively, a tail gas tank 17 for connecting to the exhaust outlet of the regulating gas chamber 12-8, and a collecting tank 14 for connecting to the exhaust outlet of the measuring gas chamber 12-9; wherein the tail gas tank 17 is used to cooperate with the high-pressure gas source bottle 1 to dynamically adjust the gas pressure in the regulating gas chamber 12-8; the collecting tank 14 is used to collect fission gas, which can be transported for component analysis.

[0048] In some possible embodiments, the output end of the high-pressure gas source bottle 1 is connected to a gas source buffer tank 5, and the high-pressure gas source bottle 1 transports inert gas to the regulating gas chamber 12-8 and the measuring gas chamber 12-9 through the gas source buffer tank 5; a pressure reducing valve 3 and a first electric valve 4 are sequentially arranged between the high-pressure gas source bottle 1 and the gas source buffer tank 5; the high-pressure gas source bottle 1 is connected to the pressure reducing valve 3 through a stainless steel metal pipeline, and the gas pressure can be reduced to the required air pressure through the pressure reducing valve 3; the pressure reducing valve 3 is connected to the first electric valve 4 through a stainless steel metal pipeline, and the pressure reducing valve 4 can be opened to fill the gas source buffer tank 5 with the reduced pressure gas.

[0049] In some possible implementations, a second electric valve 7 and a first gas mass flow meter 8 are sequentially provided at the output end of the gas source buffer tank 5; wherein the decompressed gas passes through the metal gas pipe through the second electric valve 7 and the first gas mass flow meter 8 to precisely control and adjust the gas flow, thereby obtaining the adjusted gas volume.

[0050] In some possible implementations, a third electric valve 9 is provided between the output end of the first gas mass flow meter 8 and the regulating gas chamber 12 - 8 ; a fourth electric valve 10 is provided between the output end of the first gas mass flow meter 8 and the measuring gas chamber 12 - 9 .

[0051] In some possible implementations, a fifth electric valve 13 is provided between the exhaust outlet of the measuring air chamber 12-9 and the collecting tank 14; a sixth electric valve 15 and a second gas mass flow meter 16 are provided in sequence between the exhaust outlet of the regulating air chamber 12-8 and the tail gas tank 17.

[0052] In some possible implementations, the high-pressure gas source bottle 1 , the gas source buffer tank 5 , the output end of the third electric valve 9 , the output end of the fourth electric valve 10 , and the tail gas tank 17 are all provided with pressure transmitters.

[0053] Embodiment 2:

[0054] This embodiment 2 is further optimized on the basis of embodiment 1, such as Figure 1 As shown, a method for online measurement of the release pressure of fission gas of a fuel element is provided, comprising the following processes:

[0055] Process 1: The high-pressure gas source bottle 1 is a general standard 50L high-purity helium bottle. The pressure in the helium bottle is fed back by the first pressure transmitter 2. It is necessary to ensure that the pressure of the high-pressure gas source bottle 1 is greater than 10Mpa. If it is less than 10Mpa, it is necessary to replace it with a new gas bottle in time;

[0056] Process 2: Connect the high-pressure gas source bottle 1 to the pressure reducing valve 3 through a stainless steel metal pipeline, and reduce the gas pressure to the required pressure through the pressure reducing valve 3;

[0057] Process 3: The pressure reducing valve 3 is connected to the first electric valve 4 through a stainless steel metal pipeline. The first electric valve 4 can be opened to fill the gas source buffer tank 5 with the reduced pressure gas. The reduced pressure gas in the tank can be fed back in real time through the second pressure transmitter 6.

[0058] Process 4: The decompressed gas passes through the metal gas pipe, the second electric valve 7 and the first gas mass flowmeter 8 to accurately control and adjust the gas flow rate, thereby obtaining the adjusted gas volume;

[0059] Process 5: According to the gas regulation requirements, the regulated gas can be controlled by the third electric valve 9 to enter the regulating gas chamber 12-8 of the fission gas measurement tooling 12 to achieve negative regulation of the regulated gas pressure, or controlled by the fourth electric valve 10 to enter the measuring gas chamber 12-9 of the fission gas measurement tooling 12;

[0060] Process 6: The regulating gas chamber 12-8 of the fission gas measurement tooling 12 is led out of the reactor through a stainless steel metal pipe and connected to the tail gas tank 17 after passing through the sixth electric valve 15 and the second gas mass flow meter 16, so as to realize negative regulation of the regulating gas pressure;

[0061] Process 7: The tail gas pressure collected by the tail gas tank 17 is fed back by the fourth pressure transmitter 18;

[0062] Process 8: The measuring gas chamber 12-9 of the fission gas measuring tool 12 is led out of the reactor through a stainless steel metal pipe and connected to the collecting tank 14 after passing through the fifth electric valve 13. The collected gas can be transported for component analysis.

[0063] Process 9: The subsystem composed of the high-pressure gas source bottle 1, the first pressure transmitter 2, the pressure reducing valve 3, the first electric valve 4, the gas source buffer tank 5, the first pressure transmitter 2, the second electric valve 7, the first gas mass flow meter 8, and the third electric valve 9 is arranged in the non-radioactive process room, the subsystem composed of the sixth electric valve 15, the second gas mass flow meter 16, the tail gas tank 17, the fifth electric valve 13, and the collecting tank 14 is arranged in the radioactive process room outside the pressure vessel, and the fission gas measurement tooling 12 is coupled with the fuel element and installed inside the pressure vessel to realize safe zoning management.

[0064] Process 10: The pressure sealing boundary of the regulating gas chamber 12-8 of the fission gas measurement tool 12 is the pressure-bearing casing 12-4 and the bellows 12-3;

[0065] Process 11: The pressure sealing boundary of the measuring gas chamber 12-9 of the fission gas measuring tool 12 is the pressure-bearing casing 12-4, the bellows 12-3, and the fuel cladding 12-2;

[0066] Process 12: The pressure changes in the regulating gas chamber 12-8 and the measuring gas chamber 12-9 of the fission gas measuring tool 12 will cause the bellows 12-3 to expand and contract, thereby causing the magnetic core rod 12-10 connected to the bellows 12-3 in the pressure-bearing casing 12-4 to move, and finally causing the magnetic field of the coil of the linear displacement sensor 12-6 to be cut, resulting in induced current changes, which are transmitted and collected by the signal cable 12-7; wherein a connecting rod can be set at the other end of the bellows 12-3, and a magnetic core rod 12-10 is set at the end of the connecting rod extending into the linear displacement sensor 12-6.

[0067] The above process can form an online measurement method, and the method steps include:

[0068] Step 1: Close the first electric valve 4, the second electric valve 7, the third electric valve 9, the fourth electric valve 10, the fifth electric valve 13, the sixth electric valve 15, the first gas mass flow meter 8, and the second gas mass flow meter 16 and set them to 0;

[0069] Step 2: Record the pressure of the first pressure transmitter 2 as P2 and the pressure of the third pressure transmitter 11 as P 11 , the pressure of the fourth pressure transmitter 18 is P 18 , the linear displacement sensor 12-6 measures the displacement of the bellows 12-3 as V;

[0070] Step 3: adjust the pressure after the pressure reducing valve 3 to 2Mpa, adjust the first electric valve 4 to fill the gas source buffer tank 5 with reduced pressure gas, and observe that the pressure P2 of the first pressure transmitter 2 remains at 2Mpa;

[0071] Step 4: As the fission gas release increases, when V increases to the threshold V a , (V a The corresponding elongation displacement when the fission gas pressure reaches a within the sensitive elastic range of the bellows 12-3 is opened, the flow rate of the first mass flowmeter is set to 5 mL / min, and the third electric valve 9 is controlled to slowly fill the regulating gas chamber 12-8 of the fission gas measurement tooling 12 with helium;

[0072] Step 5: Observe the displacement V of the bellows 12-3 measured by the linear displacement sensor 12-6. When V decreases to 0, close the third electric valve 9, close the second electric valve 7, and set the flow rate of the first gas mass flow meter 8 to 0;

[0073] Step 6: If the displacement V of the measured bellows 12-3 becomes a negative value, the flow rate of the second gas mass flow meter 16 can be set to 2 mL / min, and the sixth electric valve 15 can be controlled to slowly release the helium in the regulating gas chamber 12-8 to the tail gas tank 17;

[0074] Step 7: Repeat steps 5 and 6 to dynamically adjust the pressure in the regulating chamber 12-8, so that the displacement V of the bellows 12-3 is 0, close the first electric valve 4, the second electric valve 7, the third electric valve 9, the fourth electric valve 10, the fifth electric valve 13, the sixth electric valve 15, the first gas mass flow meter 8, and the second gas mass flow meter 16 to 0, and record the pressure of the third pressure transmitter 11 as P 12 ;

[0075] Step 8: Adjust the pressure after the pressure reducing valve 3 to 4Mpa, adjust the first electric valve 4 to fill the gas source buffer tank 5 with reduced pressure gas, and observe that the pressure P2 of the first pressure transmitter 2 remains at 4Mpa;

[0076] Step 9: Repeat steps 4 to 7 and record the pressure of the third pressure transmitter 11 as P 13 ;

[0077] Step 10: Adjust the pressure after the pressure reducing valve 3 to 6Mpa, adjust the first electric valve 4 to fill the gas source buffer tank 5 with reduced pressure gas, and observe that the pressure P2 of the first pressure transmitter 2 remains at 6Mpa;

[0078] Step 11: Repeat steps 4 to 7 and record the pressure of the third pressure transmitter 11 as P 14 ;

[0079] Step 12: Adjust the pressure after the pressure reducing valve 3 to 8Mpa, adjust the first electric valve 4 to fill the gas source buffer tank 5 with reduced pressure gas, and observe that the pressure P2 of the first pressure transmitter 2 remains at 8Mpa;

[0080] Step 13: Repeat steps 4 to 7 and record the pressure of the third pressure transmitter 11 as P 15 ;

[0081] Step 14: Adjust the pressure after the pressure reducing valve 3 to 10 MPa, adjust the first electric valve 4 to fill the gas source buffer tank 5 with reduced pressure gas, and observe that the pressure P2 of the first pressure transmitter 2 is maintained at 10 MPa;

[0082] Step 15: Repeat steps 4 to 7 and record the pressure of the third pressure transmitter 11 as P 16 ;

[0083] Step 16: The released gas pressure is too high, and gas pressure relief and collection are required. The fifth electric valve 13 is adjusted to collect the gas into the collection tank 14;

[0084] Step 17: When V decreases to the threshold V b (V bThe corresponding compression displacement when the fission gas pressure is less than the regulating gas b within the sensitive elastic range of the bellows 12-3 is closed, the flow rate of the first gas mass flowmeter 8 is set to 5 mL / min, and the sixth electric valve 15 is controlled to slowly release the helium in the regulating gas chamber 12-8 to the tail gas tank 17, so that the displacement V of the bellows 12-3 is 0;

[0085] Step 18: Repeat steps 16 to 17 to release the gas pressure and collect the released fission gas;

[0086] The fission gas release pressure P is the sum of the pressures measured by the third pressure transmitter 11 in the multi-stage pressure regulation, that is, P = P 11 +P 12 +P 13 +P 14 +P 15 +P 16 ;

[0087] In the above steps, the third pressure transmitter 11 measures the pressure of inert gas helium which is not easy to activate, and the pressure measuring position is at the high pressure end outside the pile. The pipeline is thin and long, and the activated gas in the pile will not diffuse out of the pile, reducing the risk of radioactivity during operation by personnel.

[0088] The measurement process combines the linear displacement signal to measure the displacement of the bellows 12-3, and cooperates with the dynamic adjustment of the gas to keep the bellows 12-3 within the sensitive elastic limit, thereby improving the measurement accuracy.

[0089] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An on-line measuring device for the release pressure of fission gas of a fuel element, characterized in that: It comprises a fission gas measuring tool (12) arranged in the pressure vessel and a gas regulating device arranged outside the pressure vessel; The fission gas measurement tool (12) comprises an outer sleeve (12-5), one end of the outer sleeve (12-5) being fixed to the fuel cladding (12-2); a pressure sleeve (12-4) and a linear displacement sensor (12-6) are fixed in sequence from one end to the other end of the inner side of the outer sleeve (12-5); the pressure sleeve (12-4) is open toward one end of the fuel cladding (12-2) and is in communication with the fuel pellet (12-1); A bellows (12-3) is fixed in the pressure-bearing sleeve (12-4), and the pressure-bearing sleeves (12-4) at both ends of the bellows (12-3) are respectively provided with a regulating air chamber (12-8) and a measuring air chamber (12-9), and one end of the bellows (12-3) is open toward the measuring air chamber (12-9), and the fuel pellet (12-1) is connected to the interior of the bellows (12-3) in sequence through the opening at one end of the pressure-bearing sleeve (12-4), the measuring air chamber (12-9), the opening at one end of the bellows (12-3); A magnetic core rod (12-10) is fixed to the other end of the bellows (12-3); the magnetic core rod (12-10) passes through the other end of the pressure-bearing sleeve (12-4) and extends into the inner cavity of the winding frame of the linear displacement sensor (12-6); the center of the magnetic section of the magnetic core rod (12-10) is placed at the axial center of the inner cavity of the winding frame of the linear displacement sensor (12-6); The gas regulating device is used to transport inert gas to the regulating gas chamber (12-8) and the measuring gas chamber (12-9), and to regulate the internal gas pressure of the regulating gas chamber (12-8) and the measuring gas chamber (12-9); The gas regulating device comprises a high-pressure gas source bottle (1) for conveying inert gas to the regulating gas chamber (12-8) and the measuring gas chamber (12-9), respectively, a tail gas tank (17) for connecting to the exhaust outlet of the regulating gas chamber (12-8), and a collecting tank (14) for connecting to the exhaust outlet of the measuring gas chamber (12-9); The output end of the high-pressure gas source bottle (1) is connected to a gas source buffer tank (5), and the high-pressure gas source bottle (1) delivers inert gas to the regulating gas chamber (12-8) and the measuring gas chamber (12-9) through the gas source buffer tank (5); a pressure reducing valve (3) and a first electric valve (4) are sequentially arranged between the high-pressure gas source bottle (1) and the gas source buffer tank (5); A second electric valve (7) and a first gas mass flow meter (8) are sequentially arranged at the output end of the gas source buffer tank (5); A third electric valve (9) is provided between the output end of the first gas mass flow meter (8) and the regulating gas chamber (12-8); a fourth electric valve (10) is provided between the output end of the first gas mass flow meter (8) and the measuring gas chamber (12-9); A fifth electric valve (13) is provided between the exhaust outlet of the measuring gas chamber (12-9) and the collecting tank (14); a sixth electric valve (15) and a second gas mass flow meter (16) are provided in sequence between the exhaust outlet of the regulating gas chamber (12-8) and the tail gas tank (17); The high-pressure gas source bottle (1), the gas source buffer tank (5), the output end of the third electric valve (9), the output end of the fourth electric valve (10) and the tail gas tank (17) are all provided with pressure transmitters.

2. A measuring method for an online measuring device for the release pressure of fission gas of a fuel element according to claim 1, characterized in that: The following steps are involved: S1: measuring the initial displacement of the bellows (12-3) and the initial pressure value in the regulating air chamber (12-8); S2: As the fission gas released by the fuel pellet (12-1) increases, when the displacement V of the bellows (12-3) measured by the linear displacement sensor (12-6) increases to V a When the pressure behind the pressure reducing valve (3) is adjusted, the first electric valve (4) is opened, and the regulating gas chamber (12-8) is filled with inert gas; the V a is the corresponding elongation displacement when the fission gas pressure reaches a within the sensitive elastic range of the bellows; S3: when the displacement V of the bellows (12-3) measured by the linear displacement sensor (12-6) decreases to the initial displacement 0, the pressure value in the regulating air chamber (12-8) at this time is recorded; S4: repeating steps S2 to S3, and gradually increasing the pressure behind the pressure reducing valve (3), and recording the pressure value in the regulating air chamber (12-8) each time the displacement V of the bellows (12-3) decreases to the initial displacement 0; S5: The initial pressure value in the regulating gas chamber (12-8) and the pressure value in the regulating gas chamber (12-8) recorded each time are added together to obtain the fission gas release pressure P.

3. A measuring method for an on-line measuring device for the release pressure of fission gas of a fuel element according to claim 2, characterized in that: The step S3 also includes the following sub-steps: When the displacement V of the bellows (12-3) becomes a negative value, the sixth electric valve (15) between the exhaust outlet of the regulating air chamber (12-8) and the tail gas tank (17) is opened to release inert gas into the tail gas tank (17) until the displacement V of the bellows (12-3) becomes 0.

4. A measuring method for an on-line measuring device for measuring the release pressure of fission gas of a fuel element according to claim 3, characterized in that: When the fission gas released by the fuel pellet (12-1) is too high, The following steps are involved: S6: when the fission gas released by the fuel pellet (12-1) is too high, opening the fifth electric valve (13) between the exhaust outlet of the measuring gas chamber (12-9) and the collecting tank (14), and releasing the fission gas into the collecting tank (14); S7: When the displacement V of the bellows (12-3) decreases to the threshold value V b , closing the fifth electric valve (13); controlling the sixth electric valve (15) to release the inert gas in the regulating air chamber (12-8) to the tail gas tank (17) until the displacement V of the bellows (12-3) becomes 0; V b It is the corresponding compression displacement when the fission gas pressure is less than the regulating gas b within the sensitive elastic range of the bellows; S8: Repeat steps S6 and S7 to release the gas pressure and collect the released fission gas.

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