Detection method for thermal destructive test of nuclear fuel rod cladding

Abstract

The invention discloses a thermal destructive test detection method for a nuclear fuel rod cladding, which is characterized in that gas is introduced into the cladding to apply pressure, and an electric heating wire element is adopted to apply non-uniform heat in the circumferential direction or the axial direction of the cladding while the pressure is applied; and the damage bearing capacity of the device under the conditions of internal pressure and non-uniform heat conduction at the same time is detected. The device can better simulate the thermal instability of nuclear reaction when the cladding works so as to detect the thermal destruction performance of the cladding, and can better ensure the quality safety of products.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear fuel rod cladding detection, and in particular to a nuclear fuel rod cladding thermal destructive test detection method. Background Art

[0002] As traditional resources are gradually depleted, nuclear power generation using nuclear fuel has become increasingly promising. Nuclear fuel cladding is the sealed shell of nuclear fuel. Because it is in the shape of a long round tube, it is also called cladding tube or nuclear fuel rod cladding. Its function is to prevent the escape of fission products and avoid the corrosion of fuel by coolant and to effectively conduct heat energy. It is the second safety barrier of nuclear power plants. Therefore, in the production process, the destructive performance quality inspection of the cladding is particularly important.

[0003] The existing cladding destructive performance detection method usually inputs a high-temperature and high-pressure detection medium into the cladding to test its burst strength performance, such as a zirconium alloy cladding tube burst test energy storage measurement device and method disclosed in CN202311606401.7; a rapid pressure increase burst system for nuclear fuel cladding tubes disclosed in CN202122268106.8; and a nuclear fuel cladding tube burst test device and test method disclosed in CN202011052604.2, etc., all of which are similar technologies. However, due to the great instability of nuclear fuel reactions, the cladding is not subjected to uniform thermal pressure shocks in the actual working process, and the temperature of each part is not the same. In addition, in the prior art, some of them use electric heating wires to heat the cladding, and at the same time assist in passing high-pressure gas into the cladding for pressure testing. In this method, the electric heating wire is usually inside the cladding and is evenly heated, and the test cost is relatively lower. However, the influence of nuclear fuel reaction instability is still not taken into account, and the electric wire heating element is located inside the cladding, which can easily affect the internal ventilation and pressurization process.

[0004] Therefore, how to detect the thermal damage performance of the cladding under the condition of non-uniform working environment and better ensure its quality has become a problem to be considered and solved by technical personnel in this field. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is: how to provide a nuclear fuel rod cladding thermal destructive test detection method that can better simulate the thermal instability of nuclear reactions during cladding operation and detect its thermal destructive performance, so as to better ensure product quality and safety.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for testing the thermal destructiveness of nuclear fuel rod cladding is provided, wherein gas is introduced into the cladding to apply pressure, and the method is characterized in that, while applying pressure, a heating wire element is used to apply non-uniform heating to the cladding in the circumferential or axial direction to detect the ability of the cladding to withstand damage under the conditions of internal pressure and non-uniform heat conduction.

[0007] Therefore, the present invention adopts heating wire heating and gas pressure to jointly detect the thermal damage performance of nuclear fuel rod cladding, which is convenient, simple and easy to implement. At the same time, non-uniform heating in the circumferential or axial direction is adopted during heating, so the thermal instability of nuclear reaction during cladding operation can be better simulated to detect its thermal damage performance, which can better ensure the quality and safety of the product.

[0008] Furthermore, the gas introduced into the cladding is nitrogen. While better improving safety, nitrogen has better thermal conductivity and can better achieve heat conduction. During implementation, the pressure of the introduced gas is the pressure of the simulated cladding working limit, which varies according to the cladding specifications and types.

[0009] Furthermore, the method is implemented by a set of cladding test electric heating equipment, which includes a nuclear fuel rod cladding circumferential thermal destructive test heating device, the fuel rod cladding circumferential thermal destructive test heating device, including an inner heating tube whose length matches the cladding length, a joint is provided at the access end of the inner heating tube, and a plug is provided at the outlet end, two linear heating wires arranged along the axial direction are arranged in parallel at intervals in the middle position of the inner heating tube along the diameter direction, the two linear heating wires have the same length but different heating power specifications, the access ends of the two linear heating wires are respectively welded to a positive conductive metal wire and then connected to the joint, the joint has two external DC positive input wires connected to the two positive conductive metal wires in the joint, the outlet ends of the two linear heating wires are simultaneously welded to a negative conductive metal wire, the negative conductive metal wire is connected to the plug along the axis of the inner heating tube and is externally connected to a DC negative output wire.

[0010] In this way, when the nuclear fuel rod cladding circumferential thermal destructive test heating device is used, the device is installed and fixed inside the cladding to be tested, nitrogen is introduced into the cladding to form air pressure, and then direct current is used for heating. Two DC positive input wires are connected to the DC positive pole, and a single DC negative output wire is connected to the DC negative pole. Different voltages can be connected respectively, so that the two straight heating wires form two different heating powers. The cladding is subjected to different heat and temperature on both sides in the circumferential direction. After the test time is over, the cladding is qualified if it is not cracked or deformed. Therefore, this can better simulate the actual working conditions and detect the thermal destructive performance of the cladding when it is subjected to uneven heat shock in the circumferential direction. Compared with the uniform heating method, it can better improve the detection effect and improve the safety of the cladding.

[0011] Furthermore, the specifications of the two linear heating wires are Φ0.9 and Φ0.7 respectively. This can better improve the detection effect. During implementation, the heating wire uses Cr20Ni80 heating wire, which has a large heat output and better guarantees the test effect.

[0012] Furthermore, the positive electrode conductive metal wire and the negative electrode conductive metal wire are both copper wires, which are low in cost and have good conductivity.

[0013] Furthermore, the internal heating tube is a metal tube (preferably stainless steel is used in implementation), two straight heating wires and the connected positive conductive metal wire are each inserted into and fixed in the interior of a magnesium oxide tube, the interior of the two magnesium oxide tubes and between the outside and the internal heating tube are filled with magnesium oxide powder, and the space between the negative conductive metal wire and the internal heating tube is filled with magnesium oxide powder.

[0014] In this way, the inner heating tube is a metal tube, which is more convenient for conducting heat outward. At the same time, the internal powder filling is filled with magnesium oxide powder for better insulation. After the magnesium oxide tubes are respectively sleeved outside the two straight heating wires and the connected positive conductive metal wires and then filled with powder, the positioning of the two straight heating wires and the connected positive conductive metal wires can be easily achieved, so that they keep a distance from each other and the external metal tube, maintain insulation, and avoid short circuit and leakage.

[0015] Furthermore, the plug is made of silicone rubber material and is sealed at the end of the inner heating pipe outlet. The use of this material can better achieve sealing and withstand high temperature environments.

[0016] Furthermore, the joint includes a sleeve-shaped joint shell made of metal and a sealing material located inside. The outer surface of the joint shell is provided with two layers of frustum which gradually become smaller toward the connecting end. The surface at the smallest diameter of the frustum is used for insertion and positioning of the cladding port, the middle diameter of the frustum is used for welding and fixing with the inserted cladding port, and the largest diameter of the frustum is used for installation and positioning of the device itself.

[0017] In this way, when the device is used, one end of the cladding to be tested is inserted into the inner heating tube and positioned to the step surface at the minimum diameter of the truncated cone of the joint and connected to the position at the middle diameter, and then welded and sealed, and then nitrogen is passed from the other end of the cladding to form air pressure and the test is carried out. Therefore, it is more convenient to install and fix the cladding to be tested. During implementation, the sealing material inside the joint is realized by silicone rubber.

[0018] Furthermore, the cladding test electric heating equipment also includes a nuclear fuel rod cladding axial thermal destructive test heating device, the nuclear fuel rod cladding axial thermal destructive test heating device includes an inner sleeve and an outer sleeve whose length matches the cladding length and are coaxially arranged, the inner diameter of the inner sleeve is larger than the cladding and is inserted and connected during testing, a spiral heating wire is arranged in the middle position of the inner sleeve wrapped around the inner sleeve in the cavity between the inner sleeve and the outer sleeve, the spiral heating wire is axially composed of at least two sections with different heating power specifications, and both ends of the spiral heating wire are respectively connected to an armored cable, the outer ends of the two armored cables respectively pass through the circumferential surface of the outer sleeve near the end positions of the two ends and are connected to the positive and negative leads, and the cavity between the inner sleeve and the outer sleeve is also filled and sealed with insulating material.

[0019] In this way, when the nuclear fuel rod cladding axial thermal destructive test heating device is used, the cladding to be tested is inserted from the inner sleeve and installed therein, and then nitrogen is introduced into both ends of the cladding to be tested to form air pressure, and then direct current is connected to the two positive and negative leads, so that the spiral heating wires of different power specifications in the middle position of the inner sleeve emit different heat; the cladding is subjected to different heat and temperature at different positions in the axial direction, and after the test time is over, the cladding is qualified if there is no cracking or deformation. Therefore, this can better simulate the actual working conditions of the cladding and detect the thermal destructive performance of the cladding when it is subjected to uneven heat shock in the axial direction. Therefore, compared with the uniform heating method, it can better improve the detection effect and improve the safety of the cladding. At the same time, since the device heats from the outside of the cladding, it will not affect the pressure effect of the internal nitrogen, and it is also beneficial to increase the heating power of the heating wire and improve the heating simulation effect.

[0020] In specific implementation, when sampling the same batch of products, two claddings can be used at the same time, and they can be tested separately by the nuclear fuel rod cladding circumferential thermal destructive test heating device and the nuclear fuel rod cladding axial thermal destructive test heating device. The products are judged to be qualified only when both devices are not damaged or deformed. In specific implementation, the spiral heating wire is composed of three sections with different heating power specifications in the axial direction, and the specifications are 0.8kW, 2kW and 0.8kW respectively.

[0021] Furthermore, the insulating material is magnesium oxide powder, which has the advantages of good insulation effect and good thermal conductivity.

[0022] Furthermore, the inner sleeve is a metal tube, and the spiral heating wire is an armored heating wire.

[0023] In this way, heat can be better transferred inwards and the spiral heating wire and the metal tube can be prevented from contacting and conducting electricity.

[0024] Furthermore, a straight line segment is extended from both ends of the spiral heating wire in the axial direction, and an inner core is extended from the outer end of the straight line segment to connect with the inner core extending from the end of the armored cable. The inner core of the spiral heating wire and the inner core of the armored cable are bent outward as a whole and then butt-welded.

[0025] In this way, leakage between the inner core and the inner tube at the welding position of the spiral heating wire and the armored cable can be better avoided.

[0026] Furthermore, a sealing head is respectively provided at the ends of both ends of the cavity between the inner sleeve and the outer sleeve. After the outer end of the armored cable passes through the sealing head, it passes through the outer sleeve from the side. A sealing ring is provided on the outside of the sealing head. The inner circle of the sealing ring is sleeved on the outer surface of the inner sleeve and welded to seal and fix. The inner side surface of the sealing ring abuts against the end face of the outer sleeve and is welded to seal and fix.

[0027] In this way, better sealing and fixing can be achieved.

[0028] Furthermore, the plugging head is made of silicone rubber material, which has a good insulation and sealing effect.

[0029] Furthermore, a connecting handle sleeve is provided at the junction between the outer end of the armored cable and the positive and negative lead wires, and the interior of the connecting handle sleeve is filled with a sealing material.

[0030] In this way, the positive and negative leads can be better prevented from breaking due to pulling force.

[0031] Furthermore, the sealing material is a silicone rubber material.

[0032] In summary, the present invention can better simulate the thermal instability of nuclear reactions during cladding operation and detect its thermal damage performance, thereby better ensuring product quality and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The figure is a schematic diagram of the structure of the heating device for the circumferential thermal destructive test of the nuclear fuel rod cladding used in the present invention.

[0034] Figure 2 The figure is a schematic diagram of the structure of the heating device for the axial thermal destructive test of the nuclear fuel rod cladding used in the present invention.

[0035] Figure 3 for Figure 2 Enlarged structural diagram at A in the middle. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0037] In specific implementation: A method for testing the thermal destructiveness of nuclear fuel rod cladding, in which gas is introduced into the cladding to apply pressure, and its characteristic is that while applying pressure, a heating wire element is used to apply uneven heating to the cladding in the circumferential or axial direction to detect its ability to withstand damage under the conditions of internal pressure and uneven heat conduction.

[0038] Therefore, the present invention adopts heating wire heating and gas pressure to jointly detect the thermal damage performance of nuclear fuel rod cladding, which is convenient, simple and easy to implement. At the same time, non-uniform heating in the circumferential or axial direction is adopted during heating, so the thermal instability of nuclear reaction during cladding operation can be better simulated to detect its thermal damage performance, which can better ensure the quality and safety of the product.

[0039] During implementation, the gas introduced into the cladding is nitrogen. While it can better improve safety, nitrogen has better thermal conductivity and can better achieve heat conduction. During implementation, the pressure of the gas introduced is the pressure of the simulated cladding working limit, which varies according to the cladding specifications and types.

[0040] Specifically, the method is implemented by a set of cladding test electric heating equipment, which includes a nuclear fuel rod cladding circumferential thermal destructive test heating device, see Figure 1 A heating device for a circumferential thermal destructive test of a fuel rod cladding comprises an inner heating tube 1 whose length matches that of the cladding, a joint 2 being provided at the access end of the inner heating tube 1, and a plug 3 being provided at the outlet end, two linear heating wires 4 arranged along the axial direction being arranged in parallel and spaced apart in the middle position of the inner heating tube 1 along the diameter direction, the two linear heating wires 4 having the same length but different heating power specifications, the access ends of the two linear heating wires 4 being respectively welded and fixed with a positive conductive metal wire 5 and then connected to the joint 2, the joint 2 having two externally connected direct current positive input wires 6 connected to the two positive conductive metal wires 5 in the joint, the outlet ends of the two linear heating wires 4 being simultaneously welded with a negative conductive metal wire 7, the negative conductive metal wire 7 being connected to the plug 3 along the axis of the inner heating tube and being externally connected to a direct current negative output wire 8.

[0041] In this way, when the nuclear fuel rod cladding circumferential thermal destructive test heating device is used, the device is installed and fixed inside the cladding to be tested, nitrogen is introduced into the cladding to form air pressure, and then direct current is used for heating. Two DC positive input wires are connected to the DC positive pole, and a single DC negative output wire is connected to the DC negative pole. Different voltages can be connected respectively, so that the two straight heating wires form two different heating powers. The cladding is subjected to different heat and temperature on both sides in the circumferential direction. After the test time is over, the cladding is qualified if it is not cracked or deformed. Therefore, this can better simulate the actual working conditions and detect the thermal destructive performance of the cladding when it is subjected to uneven heat shock in the circumferential direction. Compared with the uniform heating method, it can better improve the detection effect and improve the safety of the cladding.

[0042] The specifications of the two linear heating wires 4 are Φ0.9 and Φ0.7 respectively. This can better improve the detection effect. During implementation, the heating wire uses Cr20Ni80 heating wire, which has a large heat output and better guarantees the test effect.

[0043] Wherein, the positive electrode conductive metal wire 5 and the negative electrode conductive metal wire 7 are both copper wires. Copper wires are low in cost and have good conductivity.

[0044] Among them, the internal heating tube 1 is a metal tube (stainless steel is preferably used in implementation), two straight heating wires 4 and the connected positive conductive metal wire 5 are each inserted into and fixed in the interior of a magnesium oxide tube (not shown in the figure), the inside of the two magnesium oxide tubes and between the outside and the internal heating tube are filled with magnesium oxide powder (not shown in the figure), and the space between the negative conductive metal wire 7 and the internal heating tube 1 is filled with magnesium oxide powder (not shown in the figure).

[0045] In this way, the inner heating tube is a metal tube, which is more convenient for conducting heat outward. At the same time, the internal powder filling is filled with magnesium oxide powder for better insulation. After the magnesium oxide tubes are respectively sleeved outside the two straight heating wires and the connected positive conductive metal wires and then filled with powder, the positioning of the two straight heating wires and the connected positive conductive metal wires can be easily achieved, so that they keep a distance from each other and the external metal tube, maintain insulation, and avoid short circuit and leakage.

[0046] The plug 3 is made of silicone rubber material and is sealed at the end of the inner heating pipe outlet. The use of this material can better achieve sealing and withstand high temperature environment.

[0047] Among them, the joint 2 includes a sleeve-shaped joint shell 9 made of metal and a sealing material located inside. The outer surface of the joint shell 9 is provided with two layers of frustum which gradually become smaller toward the connecting end. The surface at the smallest diameter of the frustum is used for insertion and positioning of the cladding port, the middle diameter of the frustum is used for welding and fixing with the inserted cladding port, and the largest diameter of the frustum is used for installation and positioning of the device itself.

[0048] In this way, when the device is used, one end of the cladding to be tested is inserted into the inner heating tube and positioned to the step surface at the minimum diameter of the truncated cone of the joint and connected to the position at the middle diameter, and then welded and sealed, and then nitrogen is passed from the other end of the cladding to form air pressure and the test is carried out. Therefore, it is more convenient to install and fix the cladding to be tested. During implementation, the sealing material inside the joint is realized by silicone rubber.

[0049] The cladding test electric heating equipment also includes a nuclear fuel rod cladding axial thermal destructive test heating device, see Figure 2-3 The heating device for the axial thermal destructive test of the nuclear fuel rod cladding comprises an inner sleeve 11 and an outer sleeve 12 whose length matches the length of the cladding and are coaxially arranged. The inner diameter of the inner sleeve 11 is larger than that of the cladding and is inserted and connected during the test. A spiral heating wire 13 is wound around the inner sleeve at a middle position in the cavity between the inner sleeve 11 and the outer sleeve 12. The spiral heating wire 13 is composed of at least two sections with different heating power specifications in the axial direction. An armored cable 14 is respectively connected to both ends of the spiral heating wire 13. The outer ends of the two armored cables 14 are respectively passed through the circumferential surface of the outer sleeve near the end positions of both ends and connected to the positive and negative electrode leads 15. The cavity between the inner sleeve 11 and the outer sleeve 12 is also filled and sealed with an insulating material.

[0050] In this way, when the nuclear fuel rod cladding axial thermal destructive test heating device is used, the cladding to be tested is inserted from the inner sleeve and installed therein, and then nitrogen is introduced into both ends of the cladding to be tested to form air pressure, and then direct current is connected to the two positive and negative leads, so that the spiral heating wires of different power specifications in the middle position of the inner sleeve emit different heat; the cladding is subjected to different heat and temperature at different positions in the axial direction, and after the test time is over, the cladding is qualified if there is no cracking or deformation. Therefore, this can better simulate the actual working conditions of the cladding and detect the thermal destructive performance of the cladding when it is subjected to uneven heat shock in the axial direction. Therefore, compared with the uniform heating method, it can better improve the detection effect and improve the safety of the cladding. At the same time, since the device heats from the outside of the cladding, it will not affect the pressure effect of the internal nitrogen, and it is also beneficial to increase the heating power of the heating wire and improve the heating simulation effect.

[0051] In specific implementation, when sampling the same batch of products, two claddings can be used at the same time, and they can be tested separately by the nuclear fuel rod cladding circumferential thermal destructive test heating device and the nuclear fuel rod cladding axial thermal destructive test heating device. The products are judged to be qualified only when both devices are not damaged or deformed. In specific implementation, the spiral heating wire is composed of three sections with different heating power specifications in the axial direction, and the specifications are 0.8kW, 2kW and 0.8kW respectively.

[0052] Wherein, the insulating material is magnesium oxide powder, which has the advantages of good insulation effect and good thermal conductivity.

[0053] The inner sleeve 11 is a metal tube, and the spiral heating wire 13 is an armored heating wire.

[0054] In this way, heat can be better transferred inwards and the spiral heating wire and the metal tube can be prevented from contacting and conducting electricity.

[0055] Among them, the ends of the spiral heating wire 13 extend a straight line segment in the axial direction, and an inner core extends from the outer end of the straight line segment to connect with the inner core extending from the end of the armored cable 14. The inner core of the spiral heating wire 13 and the inner core of the armored cable 14 are bent outward as a whole and then butt-welded.

[0056] In this way, leakage between the inner core and the inner tube at the welding position of the spiral heating wire and the armored cable can be better avoided.

[0057] Among them, a sealing head 16 is respectively provided at the two ends of the cavity between the inner sleeve 11 and the outer sleeve 12. The outer end of the armored cable 14 passes through the sealing head 16 and then passes through the outer sleeve 12 from the side. A sealing ring 17 is provided on the outside of the sealing head 16. The inner circle of the sealing ring 17 is sleeved on the outer surface of the inner sleeve and welded to seal and fix. The inner side surface of the sealing ring 17 abuts against the end face of the outer sleeve and is welded to seal and fix.

[0058] In this way, better sealing and fixing can be achieved.

[0059] The plugging head 16 is made of silicone rubber material, which has a good insulation and sealing effect.

[0060] A connecting handle sleeve 18 is sleeved at the junction of the outer end of the armored cable 14 and the positive and negative lead wires 15, and a sealing material is filled inside the connecting handle sleeve.

[0061] In this way, the positive and negative leads can be better prevented from breaking due to pulling force.

[0062] Wherein, the sealing material is silicone rubber material.

Claims

1. A method for testing the thermal destructiveness of a nuclear fuel rod cladding, wherein gas is introduced into the cladding to apply pressure, and the method is characterized in that: While applying pressure, a heating wire element is used to apply uneven heating to the cladding in the circumferential or axial direction to test its ability to withstand damage under the condition of internal pressure and uneven heat at the same time.

2. The method for thermal destructive testing of nuclear fuel rod cladding according to claim 1, characterized in that: The gas introduced into the cladding is nitrogen.

3. The method for thermal destructive testing of nuclear fuel rod cladding according to claim 1, characterized in that: The method is implemented by a set of cladding test electric heating equipment, which includes a nuclear fuel rod cladding circumferential thermal destructive test heating device, the fuel rod cladding circumferential thermal destructive test heating device, including an inner heating tube whose length matches the cladding length, a joint is provided at the access end of the inner heating tube, and a plug is provided at the outlet end, two linear heating wires arranged along the axial direction are arranged in parallel at intervals in the middle position of the inner heating tube along the diameter direction, the two linear heating wires have the same length but different heating power specifications, the access ends of the two linear heating wires are respectively welded to a positive conductive metal wire and then connected to the joint, the joint has two external direct current positive input wires connected to the two positive conductive metal wires in the joint, the outlet ends of the two linear heating wires are simultaneously welded to a negative conductive metal wire, the negative conductive metal wire is connected to the plug along the axis of the inner heating tube and is externally connected to a direct current negative output wire.

4. The method for thermal destructive testing of nuclear fuel rod cladding according to claim 3, characterized in that: The positive electrode conductive metal wire and the negative electrode conductive metal wire are both copper wires.

5. The method for thermal destructive testing of nuclear fuel rod cladding according to claim 3, characterized in that: The inner heating tube is a metal tube. Two straight electric heating wires and the connected positive conductive metal wire are respectively inserted into and fixed in the interior of a magnesium oxide tube. The interior of the two magnesium oxide tubes and between the outside and the inner heating tube are filled with magnesium oxide powder. The space between the negative conductive metal wire and the inner heating tube is filled with magnesium oxide powder.

6. The method for thermal destructive testing of nuclear fuel rod cladding according to claim 3, characterized in that: The plug is made of silicone rubber material and is sealed at the end of the outlet of the inner heating pipe.

7. The method for thermal destructive testing of nuclear fuel rod cladding according to claim 3, characterized in that: The joint includes a sleeve-shaped joint shell made of metal and a sealing material located inside. The outer surface of the joint shell is provided with two layers of frustum that gradually become smaller toward the connecting end. The surface at the smallest diameter of the frustum is used for insertion and positioning of the cladding port, the middle diameter of the frustum is used for welding and fixing with the inserted cladding port, and the largest diameter of the frustum is used for installation and positioning of the device itself.

8. The method for thermal destructive testing of nuclear fuel rod cladding according to claim 1, characterized in that: The cladding test electric heating equipment also includes a nuclear fuel rod cladding axial thermal destructive test heating device, which includes an inner sleeve and an outer sleeve whose length matches the cladding length and are coaxially arranged. The inner diameter of the inner sleeve is larger than the cladding and is inserted and connected during the test. A spiral heating wire is arranged in the middle position of the inner sleeve and the outer sleeve. The spiral heating wire is axially composed of at least two sections with different heating power specifications. The two ends of the spiral heating wire are respectively connected to an armored cable. The outer ends of the two armored cables are respectively passed through the circumferential surface of the outer sleeve near the end positions of the two ends and are connected to the positive and negative electrode leads. The cavity between the inner sleeve and the outer sleeve is also filled and sealed with insulating material.

9. The method for thermal destructive testing of nuclear fuel rod cladding according to claim 8, characterized in that: The insulating material is magnesium oxide powder; The inner sleeve is a metal tube, and the spiral heating wire is an armored heating wire; A straight line segment is extended from both ends of the spiral heating wire in the axial direction, and an inner core is extended from the outer end of the straight line segment to connect with the inner core extending from the end of the armored cable. The inner core of the spiral heating wire and the inner core of the armored cable are bent outward as a whole and then butt-welded.

10. The method for thermal destructive testing of nuclear fuel rod cladding according to claim 8, characterized in that: A plugging head is respectively arranged at the ends of both ends of the cavity between the inner sleeve and the outer sleeve. The outer end of the armored cable passes through the plugging head and then passes through the outer sleeve from the side. A sealing ring is arranged on the outside of the plugging head. The inner ring of the sealing ring is sleeved on the outer surface of the inner sleeve and welded to seal and fix. The inner side surface of the sealing ring abuts against the end surface of the outer sleeve and is welded to seal and fix. The plugging head is made of silicone rubber material; A connecting handle sleeve is provided at the junction of the outer end of the armored cable and the positive and negative lead wires, and a sealing material is filled inside the connecting handle sleeve; the sealing material is a silicone rubber material.

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