Device and method for pressurizing and measuring fuel rod and sampling gas in rod

Abstract

The invention belongs to the technical field of nuclear fuel assembly manufacturing, and aims to solve the problems of sealing pressurization, in-rod gas pressure detection and gas sampling of an annular fuel rod made of a double-layer cladding pipe. The invention discloses a fuel rod pressurizing, pressure measuring and in-rod gas sampling device and method.The device comprises a sealed welding chamber, a fuel rod tail end pressure guiding cavity and a gas pressure measuring and sampling assembly, and the sealed welding chamber is provided with a welding gun, a pressure gauge, a vacuum gauge and an end plug; the fuel rod tail end pressure guiding chamber is provided with a pipe fixing seat, a sealing detection seat, a tail end gland and a pipe fixing seat gland, and the gas pressure measuring and sampling assembly is provided with a three-valve group, a pressure gauge and a sampling gas cylinder; the method comprises the steps of stamping, pressure measuring and gas sampling. According to the invention, sealed pressurizing, in-rod gas pressure detection and gas sampling of the annular fuel rod made of the double-layer cladding pipe are realized.

Description

Technical Field

[0001] This application belongs to the field of nuclear fuel assembly manufacturing technology, and in particular relates to an apparatus and method for pressurizing, measuring and sampling gas inside fuel rods. Background Technology

[0002] In this field, Chinese patent CN201920161113.8 discloses a welding chamber for a fuel rod helium-filling plugging welding machine. It relates to the structure of a fuel rod helium-filling plugging welding machine suitable for end face plugging. The plugging welding device consists of a welding chamber, a welding torch, a vacuum system, and a helium-filling system. Because the welding torch is installed from the side, and the device only has a sealing structure for the tube wall and no sealing structure for the tube hole, it is not suitable for welding double-shell fuel rods with the gas filling hole on the side of the end plug and a hollow structure.

[0003] Furthermore, the literature "Light Water Reactor Fuel Elements" presents two pressure monitoring device structures, one using a pressure gauge connected to the end plug and the other using a method of puncturing the fuel cladding in a confined space to measure the internal pressure of the fuel rod. Chinese patent CN201511028427.3 discloses a fuel rod puncture device and a fuel rod helium volume ratio measuring device, which relates to the structure of the fuel rod puncture device and a method for detecting the helium composition inside the fuel rod. The literature "Reliability Analysis of Non-destructive Testing Method for Fuel Rod Helium Pressure" describes the principle and specific method of measuring the internal pressure of the fuel rod using the heat transfer method and verifies the measurement accuracy. It is difficult to machine a connection port on a hollow end plug, and the thinness of the connection part may lead to safety issues. Therefore, the method of measuring internal pressure by connecting a pressure gauge is not suitable for measuring the internal pressure of fuel rods with this structure. Although the puncture method and the heat transfer method are theoretically applicable to the detection of gas composition and pressure inside the fuel rod, the puncture method is a destructive testing method, complex to operate, and the device cannot be reused. The heat transfer method is relatively complex and not direct. Summary of the Invention

[0004] The purpose of this application is to provide an apparatus and method for pressurizing, measuring, and sampling gas inside a fuel rod, thereby solving the problems of sealed pressurization, gas pressure detection, and gas sampling of annular fuel rods made of double-layered cladding tubes.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] In a first aspect, this application provides an apparatus for pressurizing, measuring, and sampling gas inside a fuel rod, comprising:

[0007] A sealed welding chamber is provided with a welding torch, a pressure gauge, a vacuum gauge, and an end plug, the end plug being installed at the upper end of the fuel rod;

[0008] The fuel rod tail end pressure chamber has a tube fixing seat, a sealing detection seat, a tail end cap and a tube fixing seat cap. The tube fixing seat and the tube fixing seat cap clamp the fuel rod. The tube fixing seat connects the sealing detection seat and the tail end cap. The sealing detection seat has a central through hole and a pressure port.

[0009] The gas pressure measurement and sampling assembly includes a three-valve group, a pressure gauge, and a sampling gas cylinder. The three-valve group is connected to the pressure inlet, the pressure gauge is installed on the three-valve group, and the sampling gas cylinder is connected to the three-valve group through a pipeline.

[0010] In some embodiments, the vacuum gauge is connected to the sealed welding chamber via a pipeline, and the pipeline is equipped with a valve.

[0011] In some embodiments, the sealed welding chamber is provided with an exhaust port and a vacuum filling port.

[0012] In some embodiments, the entrance to the sealed welding chamber is provided with a first O-ring and a sealing ring top mechanism.

[0013] In some embodiments, a second O-ring is arranged on one side of the sealing detection seat and a third O-ring is arranged on the other side, and the tail end cap is pressed against the second O-ring.

[0014] In some embodiments, the three-valve assembly includes a first shut-off valve, a second shut-off valve, a third shut-off valve, a first interface, a second interface, a third interface, and a fourth interface; the first shut-off valve controls the connection of the second interface and the third interface 246, the second shut-off valve controls the connection of the first interface and the second interface, and the third shut-off valve controls the connection of the second interface and the fourth interface; the second interface is connected to the pressure port via a threaded adapter.

[0015] In some embodiments, the sampling gas cylinder has a sampling gas cylinder inlet valve and a sampling gas cylinder outlet valve, and the tail end of the sampling gas cylinder is provided with an exhaust port.

[0016] Secondly, this application provides a method for pressurizing, measuring, and sampling gas inside a fuel rod, including:

[0017] S1: Pressurization: Place the fuel rod into the sealed welding chamber and seal it. After evacuation, press helium to the preset pressure and maintain the pressure.

[0018] S2: Pressure measurement: Install the fuel rod tail end pressure chamber and connect it to the tail end of the simulated fuel rod that can measure the tail pressure. Use a three-valve group to make it synchronously filled with helium with the sealed welding chamber. Place the simulated fuel rod that can measure the tail pressure into the sealed welding chamber and seal it. After evacuation, fill with helium to the preset pressure and maintain the pressure so as to compare the pressure at both ends to determine the stabilization time.

[0019] S3: Gas sampling: Connect the sampling gas cylinder to the three-valve assembly, place the simulated fuel rod that can measure the tail pressure into the sealed welding chamber and seal it, evacuate and then fill it with helium to the preset pressure and maintain the pressure, fill the simulated fuel rod that can measure the tail pressure and the sampling gas cylinder with helium by controlling the valve, and collect the gas sample after replacement.

[0020] In some embodiments, S1 includes:

[0021] S11: Insert the fuel rod into the sealed welding chamber so that the upper end plug contacts the end plug plug;

[0022] S12: Tighten the sealing ring top mechanism against the first O-ring to seal the fuel rod sidewall and the weld chamber inlet;

[0023] S13: Close the exhaust port, evacuate the welding chamber, and open the vacuum measuring valve;

[0024] S14: After reaching the preset vacuum level, close the vacuum measuring valve, fill the sealed welding chamber with gas, and close the helium filling solenoid valve after reaching the preset pressure and holding time.

[0025] In some embodiments, S2 includes:

[0026] S21: The fuel rod is fed into the sealed welding chamber and sealed;

[0027] S22: Place the tube fixing seat on the predetermined position at the tail end of the fuel rod, install the tube fixing seat cover on the tube fixing seat, and clamp the outer wall of the fuel rod;

[0028] S23: Insert the third O-ring into the hole of the pipe fixing seat, insert the sealing detection seat into the fuel rod, and make its inner cavity cover the orifice plate, and the boss in the inner cavity presses on the third O-ring;

[0029] S24: Install the second O-ring in the sealing ring hole of the sealing test seat 18, and make the boss of the tail end cap contact the second O-ring.

[0030] S25: Connect the pipe fixing seat, the sealing detection seat and the tail end cap to deform the third O-ring and the second O-ring to form a sealing space;

[0031] S26: Install the three-valve assembly and pressure gauge at the pressure inlet;

[0032] S27: Open the second shut-off valve, close the first and third shut-off valves, and measure in real time whether the pressure at the tail end of the fuel rod is consistent with the pressure in the front welding chamber to obtain the helium stabilization time.

[0033] In some embodiments, S3 includes:

[0034] S31: Seal the fuel rod in the sealed welding chamber;

[0035] S32: Connect the sampling gas cylinder to the fourth interface, and open the inlet valve and outlet valve;

[0036] S33: Close the first shut-off valve, and open the second and third shut-off valves;

[0037] S34: Open the helium filling solenoid valve to fill the fuel rod and the sampling gas cylinder with helium. After continuously replacing the original air in the sampling gas cylinder for a period of time, close the sampling gas cylinder outlet valve. After the preset filling pressure is reached, close the sampling gas cylinder inlet valve and the welding chamber filling solenoid valve in sequence.

[0038] S35: Open the welding chamber exhaust solenoid valve to exhaust and depressurize the welding chamber.

[0039] Compared with the prior art, the apparatus and method for fuel rod pressurization, pressure measurement, and gas sampling provided in this application have the following advantages:

[0040] This application enables the sealing and pressurization of annular fuel rods made of double-layered cladding tubes, as well as the detection of gas pressure inside the rods and gas sampling.

[0041] The welding chamber structure design provided in this application can meet the requirements for sealing and helium filling of hollow fuel rods.

[0042] The tail pressure-inducing passage and pressure-inducing chamber provided in this application are based on the existing fuel rod structure design, which solves the problem of not being able to install a pressure gauge on the hollow end plug. At the same time, the structure and operation are simpler than the pressure measurement structure and operation of puncturing the outer wall or heat transfer method.

[0043] This application integrates functions such as gas sampling and vacuuming, and the switching is convenient. Attached Figure Description

[0044] To more clearly illustrate the technical solution of this application, the accompanying drawings used in the technical description will be briefly introduced below.

[0045] Figure 1 A schematic diagram of a fuel rod structure provided for the prior art;

[0046] Figure 2 A schematic diagram of the fuel rod welding chamber provided in this application;

[0047] Figure 3 A schematic diagram of a simulated fuel rod capable of measuring tail pressure provided in this application;

[0048] Figure 4 A schematic diagram of the fuel rod tail end pressure chamber structure provided in this application;

[0049] Figure 5 A schematic diagram of the structure of the tube fixing seat provided in this application;

[0050] Figure 6 This is a schematic diagram of the structure of the pipe fixing seat gland provided in this application;

[0051] Figure 7 This is a schematic diagram of the sealing test seat structure provided in this application;

[0052] Figure 8 for Figure 7 A cross-sectional view along plane AA;

[0053] Figure 9 A schematic diagram of the gas pressure measurement and sampling assembly at the tail end of the fuel rod provided in this application;

[0054] Figure 10 A flowchart illustrating the method for pressurizing, measuring, and sampling gas inside fuel rods provided in this application.

[0055] Explanation of reference numerals in the attached figures:

[0056] 1. Outer casing tube; 2. Inner casing tube; 3. Contents; 4. Lower plug; 5. Upper plug; 6. Inflation port;

[0057] 7. Sealed welding chamber; 8. Welding torch; 9. Pressure gauge; 10. Vacuum gauge; 11. Vacuum measuring valve; 12. End plug; 13. Vent port; 14. Vacuum filling and helium filling port; 15. First O-ring seal; 16. Sealing ring top mechanism;

[0058] 17. Pipe fixing seat; 18. Sealing test seat; 181. Tightening boss; 182. Mounting groove; 19. Tail end cap; 191. Countersunk through hole; 20. Second O-ring seal; 21. Pressure inlet; 22. Third O-ring seal; 23. Pipe fixing seat cap;

[0059] 21. Pressure tap; 24. Three-valve manifold; 25. Pressure gauge; 26. Quick-connect fitting; 27. Sampling gas cylinder; 28. Exhaust port;

[0060] 241. First shut-off valve; 242. Second shut-off valve; 243. Third shut-off valve; 244. First port; 245. Second port; 246. Third port; 247. Fourth port; 271. Inlet valve; 272. Outlet valve. Detailed Implementation

[0061] The following detailed description provides further details on specific implementation methods.

[0062] To facilitate understanding, a simple description of a fuel rod structure is provided first. The fuel rod includes an outer casing tube 1, an inner casing tube 2, a lower plug 4, and an upper plug 5. The lower plug 4 and the upper plug 5 are sealed together using a TIG ring welding process to create an annular cavity, within which the annular core, spring, and other contents 3 are enclosed. After ring welding, high-pressure helium gas is injected into the fuel rod cavity through the filling port 6, and the filling port 6 is plugged using TIG spot welding under helium atmosphere protection.

[0063] like Figures 1 to 9 As shown, this application provides a device for pressurizing, measuring and sampling gas inside an annular fuel rod, including a sealed welding chamber 7, a fuel rod tail end pressure chamber and a gas pressure measurement and sampling assembly.

[0064] Pressurized welding must be performed in a sealed welding chamber 7. This application provides a sealed welding chamber 7 specifically for plugging welding of hollow fuel rods. For example... Figure 2 As shown, the sealed welding chamber 7 includes a welding torch 8, a pressure gauge 9, a vacuum gauge 10, a vacuum measuring valve 11, an end plug 12, a first O-ring seal 15, and a sealing ring top mechanism 16. The sealed welding chamber 7 has an exhaust port 13 and a vacuum-filling / helium-filling port 14, both located at the bottom. The vacuum gauge 10 is connected to the vacuum measuring valve 11 and then to the sealed welding chamber 7 via a pipeline. The welding torch 8 is mounted on the top of the sealed welding chamber 7 via the sealing ring and a mechanical adjustment device. The pressure gauge 9 is also mounted on the top of the sealed welding chamber 7. The first O-ring seal 15 is located at the inlet where the fuel rod enters the sealed welding chamber 7. The sealing ring top mechanism 16 presses the first O-ring seal 15 tightly, sealing the first O-ring seal 15 against the outer casing tube 1.

[0065] After the fuel rod enters the sealed welding chamber 7, its upper end plug 4 is pressed against the polyethylene end plug 12. The sealing ring top mechanism 16 compresses and deforms the first O-ring seal 15, sealing the fuel rod end from the outer wall into the sealed welding chamber 7. At the same time, the deformation of the first O-ring seal 15 also keeps the end face of the upper end plug 5 of the fuel rod pressed against the end plug 10. After the solenoid valve connected to the exhaust port 13 is closed, the interior of the sealed welding chamber 7 is connected to the fuel rod, and is isolated from the external atmosphere of the sealed welding chamber 7.

[0066] The end plug 12 is made of polyethylene.

[0067] A pressure gauge 9 is installed on the sealed welding chamber 7 through a screw hole. The pressure gauge 9 can display the helium pressure in the welding chamber.

[0068] The sealed welding chamber 7 is equipped with an exhaust port 13 and a vacuum-filling helium port 14. The pressure gauge can withstand both positive pressure and negative pressure during vacuuming. The exhaust port 13 and the vacuum-filling helium port 14 are connected to corresponding pipelines under the control of solenoid valves: the exhaust port 13 is connected to the waste gas collection pipeline, which can realize the discharge of high-pressure gas in the welding chamber after helium-filled welding; the vacuum-filling helium port 14 is connected to the vacuum pump and the helium pressure reducing gauge through pipelines, which realizes the vacuuming or helium-filling operation of the welding chamber and the annular inner cavity of the fuel rod (through the filling port 6). The on / off state of the solenoid valve is switched by the output signal of the PLC.

[0069] To ensure consistency between the internal pressure of the fuel rod and the pressure inside the welding chamber, pressure measurement needs to be performed from the lower end plug 4. Since the lower end plug 4 lacks a through hole, while the upper end plug 5 has its own inflation port 6, the lower end plug 4 of the fuel rod is replaced with the upper end plug 5. This transforms the inflation port 6 on the end plug into a pressure-sensing tube. This structure only needs to be adapted to the length of the outer casing tube, yet it facilitates pressure measurement, vacuuming from the tail end, gas sampling, and other operations. Furthermore, the device can be reused. Figure 3 As shown, this application specifically designs a simulated fuel rod that can measure tail pressure, with upper plugs 5 on both sides.

[0070] like Figure 4 As shown, the fuel rod tail end pressure chamber includes a tube holder 17, a seal detection seat 18, a tail end cap 19, a second O-ring 20, a third O-ring 22, and a tube holder cap 23. The tube holder 17 and the tube holder cap 23 can be fitted onto the outer casing tube 1, and the two are connected by screws. The seal detection seat 18 has an inner cavity that can be inserted into the tube holder 17 and the tube holder cap 23, and at the same time, it has a hole on its other side that allows the tail end cap 19 to be inserted. Finally, countersunk screws are passed through the side through holes of the tail end cap 19 and the side through holes of the seal detection seat 18 in sequence, and tightened into the threaded holes on the sides of the tube holder 17 and the tube holder cap 23.

[0071] Preferably, to reduce weight, all components except the sealing ring are made of aluminum alloy, and the components are connected by screws. The O-rings seal the outer wall of the fuel rod to form a closed pressure-pressurizing space.

[0072] The tube holder 17 and the tube holder cap 23 are used to clamp the fuel rod, achieving axial positioning of the pressure-applying device and the fuel rod. Both components have semi-circular grooves machined at their contact points with the outer surface of the fuel rod casing tube 1, matching its outer diameter. For example... Figure 5 and Figure 6 As shown, four symmetrical assembly holes are drilled on these two components, which can be tightened by screws to clamp the fuel rods inside.

[0073] The fuel rod can be inserted through the hole on the side of the tube holder 17. A sealing ring mounting groove is milled at the edge of the hole through the fuel rod. Six symmetrical threaded through holes are machined on the side of the tube holder 17 to connect the screw that passes through the sealing detection seat 18 and the tail end cap 19, so as to connect these parts together.

[0074] like Figure 7 and Figure 8 As shown, the through hole in the middle of the sealing test seat 18 is a fuel rod passage hole. This through hole communicates with the pressure port 21 on the side of the sealing test seat. A tightening boss 181 for the third O-ring 22 is machined on one side of the through hole, and a mounting groove 182 for the second O-ring 20 is machined on the other side. Six through holes are machined on the end face of the sealing test seat 18 to connect with the pipe fixing seat 15 and the tail end cap 19.

[0075] The tail end cap 19 has a hole for the fuel rod to pass through; the side boss can tighten the second O-ring 20 after assembly, and the edge is machined with a countersunk through hole 191 for connecting the seal detection seat 18.

[0076] like Figure 9 As shown, the gas pressure measurement and sampling assembly includes a three-valve group 24, a pressure gauge 25, and a sampling gas cylinder 27.

[0077] The three-valve manifold 24 includes a first shut-off valve 241, a second shut-off valve 242, a third shut-off valve 243, and a first port 244, a second port 245, a third port 246, and a fourth port 247. The first shut-off valve 241 controls the connection of the second port 245 and the third port 246, the second shut-off valve 242 controls the connection of the first port 244 and the second port 245, and the third shut-off valve 243 controls the connection of the second port 245 and the fourth port 247.

[0078] The second port 245 of the three-valve manifold 24 is connected to the pressure port 21 via a threaded adapter. The internal pressure of the fuel rod is then measured through the inflation port 6 of the upper plug 5. The second shut-off valve 242 is opened, and the pressure value is displayed on the pressure gauge 25 connected to the first port 244. The third port 246 is connected to a KF25 connector, which can be used to connect to a vacuum line or a vacuum gauge. The fourth port 247 is used to fill the sampling gas cylinder with gas.

[0079] A clean stainless steel sampling cylinder 27 with a pressure resistance level matching the gas pressure level inside the fuel rod was selected. The sampling cylinder 27 is equipped with two sets of needle valves (inlet valve 271 and outlet valve 272) to control the opening and closing of the cylinder inlet and outlet respectively. The sampling cylinder 27 can be quickly connected to the fourth interface 247 of the three-valve group 24 through the quick-connect connector 26. The sampling cylinder 27 is also equipped with an exhaust port 28 at the tail end for venting.

[0080] Preferably, the three-valve manifold 24 is a stainless steel three-valve manifold.

[0081] like Figure 10 As shown, this application also provides a method for pressurizing, measuring, and sampling gas inside a fuel rod, comprising the following steps:

[0082] S1: Pressurization: Pressurization of the fuel rods, specifically including:

[0083] S11: Insert the fuel rod into the sealed welding chamber 7 so that the upper end plug 5 contacts the end plug plug 12.

[0084] S12: Make the sealing ring top mechanism 16 press against the first O-ring 15 to seal the fuel rod sidewall and the welding chamber inlet.

[0085] S13: Close the exhaust port 13 of the sealed welding chamber 7 by controlling the solenoid valve through the program, start the vacuum pump to evacuate the welding chamber, and open the vacuum measuring valve 11.

[0086] S14: After the preset vacuum level is reached, the program closes the vacuum measuring valve 11, and fills the sealed welding chamber 7 with helium through the vacuum filling helium port 14. After the preset pressure and holding time are reached, the helium filling solenoid valve is closed.

[0087] S2: Pressure Measurement: Measurement of the uniformity of helium filling pressure within the fuel rods, specifically including:

[0088] S21: Follow steps S11 to S12 to send the fuel rod into the sealed welding chamber 7 and seal it with the sealed welding chamber 7;

[0089] S22: Place the tube fixing seat 17 on the predetermined position at the tail end of the fuel rod, and install the tube fixing seat cover 23 on the tube fixing seat 17 with screws to clamp the outer wall of the fuel rod.

[0090] S23: Insert the third O-ring 22 into the hole of the pipe fixing seat 17, insert the sealing detection seat 18 into the fuel rod, and make its inner cavity cover the outside of the orifice plate of the pipe fixing seat 17, and the boss in the inner cavity presses on the third O-ring 22. At this time, the air filling hole 6 on the end plug should be connected to the pressure inlet 21; otherwise, adjust the position of the pipe fixing seat 17.

[0091] S24: Install the second O-ring 20 into the sealing ring hole of the sealing test seat 18, and make the boss of the tail end cap 19 contact the second O-ring 20.

[0092] S25: The pipe fixing seat 17, the sealing detection seat 18 and the tail end cap 19 are connected together by a long screw, so that the third O-ring 22 and the second O-ring 20 are deformed, forming a sealing space with the outer wall of the fuel rod between the two sealing rings.

[0093] S26: Install a three-valve manifold 24 and a pressure gauge 25 at the pressure inlet 21.

[0094] S27: Open the second shut-off valve 242 of the three-valve group 24, close the first shut-off valve 241 and the third shut-off valve 243, and follow steps S13 to S14 to measure in real time whether the pressure at the tail end of the fuel rod is consistent with the pressure at the front welding chamber, and obtain a suitable helium stabilization time.

[0095] S3: Gas Sampling: Collection of gas within the fuel rods, specifically including:

[0096] S31: Execute steps S21 to S26.

[0097] S32: Connect the sampling gas cylinder 27 to the fourth port 247 of the three-valve assembly 24 via the quick-connect port 26, and open the inlet valve 271 and outlet valve 272 of the sampling gas cylinder 27.

[0098] S33: Close the first shut-off valve 241 of the three-valve manifold 24, and open the second shut-off valve 242 and the third shut-off valve 243.

[0099] S34: Open the welding chamber helium filling solenoid valve to fill the fuel rod and sampling gas cylinder 27 with helium. After continuously replacing the original air inside the sampling gas cylinder 27 for a period of time, close the sampling gas cylinder outlet valve. After the preset filling pressure is reached, close the sampling gas cylinder inlet valve and the welding chamber filling solenoid valve in sequence.

[0100] S35: Open the welding chamber exhaust solenoid valve to exhaust and depressurize the welding chamber.

[0101] S36: If multiple samples are required, simply connect the new gas cylinder to the quick-connect interface and perform gas sampling using the method in step S34.

[0102] S37: If a gas sampling bottle without an exhaust port 28 is used, a vacuum line can be connected to the third port 246 of the three-valve group 24 to evacuate the tail end of the tube and the gas cylinder area before filling with gas.

[0103] In this application, pressure measurement and gas sampling shall be performed using end plugs with holes at both ends (such as...). Figure 3 (As shown), therefore the tail end must be sealed first.

[0104] The above description is only a specific embodiment of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the protection scope of this application.

Claims

1. A device for pressurizing, measuring, and sampling gas inside a fuel rod, characterized in that, include: The sealed welding chamber (7) has a welding torch (8), a pressure gauge (9), a vacuum gauge (10) and an end plug head (12), which is mounted on the upper end (5) of the fuel rod; The fuel rod tail end pressure chamber has a tube fixing seat (17), a sealing detection seat (18), a tail end cap (19) and an upper cap (23). The tube fixing seat (17) and the upper cap (23) clamp the fuel rod. The tube fixing seat (17) connects the sealing detection seat (18) and the tail end cap (19). The sealing detection seat (18) has a central through hole and a pressure port (21). The gas pressure measurement and sampling assembly has a three-valve group (24), a pressure gauge (25) and a sampling gas cylinder (27). The three-valve group (24) is connected to the pressure inlet (21). The pressure gauge (25) is installed on the three-valve group (24). The sampling gas cylinder (27) is connected to the three-valve group (24) through a pipeline.

2. The apparatus for pressurizing, measuring, and sampling gas inside fuel rods according to claim 1, characterized in that, The vacuum gauge (10) is connected to the sealed welding chamber (7) via a pipeline, and a vacuum measuring valve (11) is provided on the pipeline.

3. The apparatus for pressurizing, measuring, and sampling gas inside fuel rods according to claim 1, characterized in that, The entrance of the sealed welding chamber (7) is provided with a first O-ring seal (15) and a sealing ring top mechanism (16). The sealed welding chamber (7) is provided with an exhaust port (13) and a vacuum filling port (14).

4. The apparatus for pressurizing, measuring, and sampling gas inside fuel rods according to claim 1, characterized in that, A second O-ring (20) is arranged on one side of the sealing detection seat (18), and a third O-ring (22) is arranged on the other side. The tail end cap (19) presses against the second O-ring (20).

5. The apparatus for pressurizing, measuring, and sampling gas inside fuel rods according to claim 1, characterized in that, The three-valve assembly (24) includes a first shut-off valve (241), a second shut-off valve (242), a third shut-off valve (243), a first port (244), a second port (245), a third port (246), and a fourth port (247); the first shut-off valve (241) controls the connection of the second port (245) and the third port (246), the second shut-off valve (242) controls the connection of the first port (244) and the second port (245), and the third shut-off valve (243) controls the connection of the second port (245) and the fourth port (247); the second port (245) is connected to the pressure port (21) through a threaded adapter.

6. The apparatus for pressurizing, measuring, and sampling gas inside fuel rods according to claim 1 or 6, characterized in that, The sampling gas cylinder (27) has a sampling gas cylinder inlet valve and a sampling gas cylinder outlet valve, and the tail end of the sampling gas cylinder (27) is provided with an exhaust port (28).

7. A method for pressurizing, measuring, and sampling gas inside a fuel rod, characterized in that, include: S1: Place the fuel rod into the sealed welding chamber (7) and seal it. After evacuating the vacuum, fill it with helium to the preset pressure and maintain the pressure. S2: Install the tail end pressure chamber of the fuel rod and connect it to the tail end of the simulated fuel rod that can measure the tail pressure. Use a three-valve group (24) to make it synchronously fill helium with the sealed welding chamber. Place the simulated fuel rod into the sealed welding chamber (7) and seal it. After evacuating, fill it with helium to the preset pressure and hold the pressure to compare the pressure at both ends to determine the stabilization time. S3: Connect the sampling gas cylinder (27) to the three-valve group (24), place the simulated fuel rod into the sealed welding chamber (7) and seal it, evacuate and fill it with helium to the preset pressure and maintain the pressure, fill the simulated fuel rod and the sampling gas cylinder (27) with helium through the control valve, and collect the gas sample after replacement.

8. The method for pressurizing, measuring, and sampling gas inside fuel rods according to claim 7, characterized in that, S1 includes: S11: Insert the fuel rod into the sealed welding chamber (7) so that the upper end plug (5) comes into contact with the end plug top (12); S12: Make the sealing ring top mechanism (16) press against the first O-ring (15) to seal the fuel rod sidewall and the welding chamber inlet; S13: Close the exhaust port (13), evacuate the welding chamber, and open the vacuum measuring valve (11); S14: After reaching the preset vacuum level, close the vacuum measuring valve (11), fill the sealed welding chamber (7) with gas, and close the helium filling solenoid valve after reaching the preset pressure and holding time.

9. The method for pressurizing, measuring, and sampling gas inside fuel rods according to claim 7, characterized in that, S2 include: S21: The fuel rod is fed into the sealed welding chamber (7) and sealed; S22: Place the tube fixing seat (17) on the predetermined position at the tail end of the fuel rod, install the upper pressure cap (23) on the tube fixing seat (17), and clamp the outer wall of the fuel rod; S23: Insert the third O-ring (22) into the hole of the pipe fixing seat (17), insert the sealing detection seat (18) into the fuel rod, and make its inner cavity cover the outside of the orifice plate, and the boss in the inner cavity presses on the third O-ring (22); S24: Install the second O-ring (20) into the sealing ring hole of the sealing detection seat 18, and make the boss of the tail end cap (19) contact the second O-ring (20). S25: Connect the pipe fixing seat (17), the sealing detection seat (18) and the tail end cap (19) to deform the third O-ring (22) and the second O-ring (20) to form a sealing space; S26: Install the three-valve assembly (24) and pressure gauge (25) at the pressure inlet (21); S27: Open the second shut-off valve (242), close the first shut-off valve (241) and the third shut-off valve (243), and measure in real time whether the pressure at the tail end of the fuel rod is consistent with the pressure at the front welding chamber to obtain the helium stabilization time.

10. The method for pressurizing, measuring, and sampling gas inside fuel rods according to claim 7, characterized in that, S3 include: S31: Seal the fuel rod inside the sealed welding chamber (7); S32: Connect the sampling gas cylinder (27) to the fourth interface (247), and open the inlet valve (271) and the outlet valve (272); S33: Close the first shut-off valve (241), and open the second shut-off valve (242) and the third shut-off valve (243); S34: Open the helium filling solenoid valve to fill the fuel rod and the sampling gas cylinder (27) with helium. After continuously replacing the original air inside the sampling gas cylinder (27) for a period of time, close the sampling gas cylinder outlet valve. After the preset filling pressure is reached, close the sampling gas cylinder inlet valve and the welding chamber filling solenoid valve in sequence. S35: Open the welding chamber exhaust solenoid valve to exhaust and depressurize the welding chamber.

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