A test device for coating capsules

Abstract

The application provides a coated test device, which comprises a simulation cladding, the simulation cladding is located in a high-temperature and high-pressure water environment, an outer wall of the simulation cladding is coated, the simulation cladding defines a sealed cavity, and the internal pressure of the cavity is adjustable; a heating rod is arranged in the cavity of the simulation cladding, a plurality of annular ridges are arranged on the heating rod, the annular ridges are arranged at intervals in the axial direction of the heating rod, and the annular ridges are annular protrusions in the radial direction of the heating rod; wherein the outermost annular surface of the annular ridges in the radial direction is in contact with the inner wall of the simulation cladding, a through hole is arranged on the annular ridge, and the through hole penetrates through the opposite two sides of the annular ridge in the axial direction. The performance of the coated cladding in the coupling scene of the high-temperature and high-pressure water environment and internal stress change is tested.

Description

Technical Field

[0001] This invention relates to the field of pressurized water reactors, and more particularly to a testing device for a coating cladding. Background Technology

[0002] As research and development of coating cladding progresses, the long-term service performance of coating cladding, especially the failure mechanisms under the corrosion-mechanical coupling effect in actual reactors, still requires in-depth research and reliable evaluation. Current testing of coating cladding materials largely focuses on individual performance evaluations. For example, testing the basic mechanical properties of coating materials (such as strength, hardness, and toughness) uses universal testing machines to conduct ring crush tests, circumferential tensile tests, internal pressure burst tests, and internal pressure creep tests. These tests can be performed at both room temperature and high temperature, but they cannot be coupled with fouling deposition for testing. Similarly, for corrosion performance testing (such as uniform corrosion, knot corrosion, and under-deposit corrosion), current methods commonly use autoclaves for plate corrosion experiments, which cannot simulate the internal pressure creep atmosphere.

[0003] Most existing experimental setups can only simulate single operating conditions, such as simple high-temperature water corrosion experiments, high-temperature mechanical loading experiments, or boiling heat transfer experiments. They cannot simultaneously reproduce the multi-field coupling conditions faced by the cladding in actual operation. This leads to insufficient understanding of the failure mechanisms of coated cladding under complex service environments and a lack of relevant experimental verification methods, thus restricting the research and development and engineering application of new coated cladding materials.

[0004] In general, there is a severe lack of testing equipment capable of fully simulating the failure process of coating cladding. Existing testing and experimental equipment cannot reproduce the entire failure process of coating cladding for research. It is impossible to simulate the application of periodic mechanical loads to samples in the high-temperature, high-pressure water chemical environment of the pressurized water reactor primary loop to induce bamboo-like deformation and coating cracking by simulating PCMI (particle-cladding mechanical interaction) mechanical effects. It is also difficult to study the changes in nucleation and boiling behavior (such as bubble nucleation frequency and detachment diameter) and their interaction with CRUD (corrosion product deposition on pressurized water reactor fuel element surfaces) on the surface of coated cladding samples with predetermined cracks or defects. Therefore, current methods for assessing the integrity of coating cladding under the "corrosion-mechanical coupling-nucleation and boiling environment" are significantly inadequate, lacking the means to study the local chemical microenvironment within coating cracks and under scale, and its impact on localized coating dissolution and substrate corrosion processes. Summary of the Invention

[0005] The purpose of this invention is at least to provide a testing device for coated shells that can simulate the stress state of fuel rods in a high-temperature and high-pressure water environment, so as to test the performance of the coated shells in a coupled scenario of high-temperature and high-pressure water environment and internal stress changes.

[0006] The following provides a brief overview of one or more aspects to offer a basic understanding of them. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify key or decisive elements of all aspects, nor to define the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form to prepare for the more detailed descriptions that follow.

[0007] One embodiment of the present invention provides a testing device for coating and shelling, the testing device comprising:

[0008] The simulated shell is located in a high-temperature and high-pressure water environment. The outer wall of the simulated shell is coated with a coating. The simulated shell defines a sealed cavity, and the internal pressure of the cavity is adjustable.

[0009] A heating rod is disposed within the cavity of the simulated enclosure. The heating rod has several annular ridges spaced apart axially, and the ridges protrude radially in a ring shape.

[0010] The outermost annular surface of the ridge in the radial direction contacts the inner wall of the simulated shell. Through holes are provided on the ridge, which penetrate the opposite sides of the ridge in the axial direction to maintain uniform internal pressure in the cavity.

[0011] In some embodiments, the simulated casing is a tubular structure, coaxially arranged with the heating rod.

[0012] In some embodiments, the axial spacing between adjacent annular ridges on the heating rod is close to or consistent.

[0013] In some embodiments, the through-hole also extends through the outermost annular surface of the ridge in the radial direction.

[0014] In some embodiments, the testing apparatus includes a pressure supply system for inflating or deflating the cavity of the simulated cladding to simulate the internal pressure creep state during the heating process of the fuel rod.

[0015] In some embodiments, an air inlet and an exhaust outlet are provided on the simulated shell, and both the air inlet and the exhaust outlet are in communication with the cavity.

[0016] The pressure supply system includes an air source and a booster pump. The air source is connected to the air inlet through the booster pump to achieve air filling and pressurization. A gas back pressure valve is installed at the exhaust port to achieve exhaust pressure stabilization.

[0017] In some embodiments, the testing apparatus includes a high-temperature, high-pressure water loop system for providing a high-temperature, high-pressure water environment that simulates the primary loop of a pressurized water reactor.

[0018] In some embodiments, the high-temperature and high-pressure water circuit system includes:

[0019] Material storage tanks are used to store aqueous solutions that simulate the chemical environment of fouling deposits in the primary loop of a pressurized water reactor.

[0020] A high-pressure pump is used to pressurize aqueous solutions. The inlet of the high-pressure pump is connected to the outlet of the material storage tank.

[0021] A heating element is used to heat the pressurized aqueous solution; the inlet of the heating element is connected to the outlet of the high-pressure pump.

[0022] An autoclave is used to contain and isolate a pressurized and heated aqueous solution from the outside environment, providing a high-temperature and high-pressure water environment. The inlet of the autoclave is connected to the outlet of the heating element, and the simulated shell is placed in the aqueous solution inside the autoclave.

[0023] In some embodiments, the heating component includes:

[0024] A preheating device is used to preheat pressurized aqueous solutions. The inlet of the preheating device is connected to the outlet of the high-pressure pump.

[0025] A heat exchange device is used to heat a pressurized aqueous solution using the heat from the effluent from an autoclave. The cold end inlet of the heat exchange device is connected to the outlet of a preheating device, the cold end outlet of the heat exchange device is connected to the inlet of the autoclave, and the outlet of the autoclave is connected to the hot end inlet of the heat exchange device.

[0026] In some embodiments, the high-temperature and high-pressure water circuit system further includes a cooling device and a water treatment device. The cooling device is used to cool the discharged liquid, and the inlet of the cooling device is connected to the hot end outlet of the heat exchange device. The outlet of the cooling device is connected to the inlet of the material storage tank through the water treatment device, and the water treatment device is used to treat the cooled discharged liquid.

[0027] In some embodiments, a liquid back pressure valve is provided in the flow path between the hot end outlet of the heat exchange equipment and the inlet of the material storage tank. The liquid back pressure valve is used to maintain the pressure balance of the high temperature and high pressure water circuit system.

[0028] In some embodiments, a temperature monitoring element is installed inside the autoclave to monitor the temperature of the aqueous solution inside the autoclave.

[0029] The coating cladding testing device involved in this invention can comprehensively simulate cladding stress changes, supercooled nucleation boiling, corrosion product deposition, and under-deposit chemical environment. It has significant engineering application value and theoretical significance for revealing the failure mechanism of chromium coating cladding, evaluating its service integrity and lifespan, and guiding the development of new accident-tolerant coating cladding materials. Specifically:

[0030] By employing a heating rod with a ring ridge, the shape of a deformed core block can be simulated. By adjusting the internal pressure of the cladding, the mechanical properties of the cladding under core block contact scenarios are created, thereby quickly simulating the surface characteristics of the bamboo-like cladding and promoting the initiation of cracks in the coating. The cracks in the coating cladding can form nucleation sites for bubble boiling, thus replacing the traditional methods of simulating crack formation by controlling surface roughness or artificially creating millimeter-scale cracks on the coating surface, which are closer to the real environment. Attached Figure Description

[0031] The above-described features and advantages of the present invention will be better understood after reading the following detailed description of embodiments of the present disclosure in conjunction with the accompanying drawings. In the drawings, components are not necessarily drawn to scale, and components having similar related characteristics or features may have the same or similar reference numerals. Wherein:

[0032] Figure 1 This is a schematic diagram of the coating failure process;

[0033] Figure 2 This is a schematic diagram of the structure of a coating-coated testing device according to some embodiments;

[0034] Figure 3 This is a schematic diagram of the structure of a simulated fuel rod according to some embodiments;

[0035] Figure 4 This is a radial plan view of the ridge on the heating rod as shown in some embodiments. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the aspects described below with reference to the accompanying drawings and specific embodiments are merely exemplary and should not be construed as limiting the scope of protection of the present invention in any way.

[0037] It should be understood that the terms "system" and "device" used in this article are a method of distinguishing different components, elements, parts, sections, or assemblies at different levels. However, if other words can achieve the same purpose, they can be replaced by other expressions.

[0038] It is understood that the technical terms that may be used in the description of this specification, such as “inner” and “outer”, indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing the implementation method and do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of the invention.

[0039] It should be noted that the use of terms such as "first" and "second" to define features in this document is merely for the purpose of distinguishing the corresponding features. Unless otherwise stated, these terms have no special meaning and should not be construed as limiting the scope of protection of this invention. As shown in this specification and claims, terms such as "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural, unless the context clearly indicates otherwise. Generally, the term "comprising" only indicates the inclusion of explicitly identified elements, which do not constitute an exclusive list of devices and may also include other elements.

[0040] During the long-term operation of a pressurized water reactor (PWR), the cladding encases the fuel rods and fuel pellets. As fuel burnup increases, the fuel pellets deform to some extent due to factors such as sintering shrinkage, cracking swelling, and rearrangement. This deformation interacts with the inner wall of the cladding, generating a ratchet effect, such as... Figure 1 ( Figure 1 As shown in the schematic diagram of the coating failure process, periodic stress zones often form along the axial direction of the coating. Simultaneously, the internal pressure power of the coating changes instantaneously, causing internal pressure fluctuations and leading to creep. Under the combined effects of ratcheting and creep, the coating exhibits "bamboo-like" deformation, specifically annular protrusions on the coating surface. This "bamboo-like" deformation alters the local stress distribution of the coating to some extent, making the coating more prone to cracking and generating microcracks in stress concentration areas.

[0041] In the primary circuit of a pressurized water reactor, the fuel rod cladding must withstand not only the mechanical forces from the fuel pellets but also the corrosive effects of the high-temperature, high-pressure aqueous chemical environment. The cladding is situated in this high-temperature, high-pressure aqueous chemical environment, and its surface is typically in a state of subcooled boiling or localized nucleation boiling. For example... Figure 1 As shown, when microcracks develop in the coating on the cladding surface, these microcracks act as boiling initiation points, leading to intensified surface nucleation boiling. This increased nucleation boiling intensity not only alters local heat transfer characteristics but also accelerates the deposition of corrosion products and hydrochemical impurities on the cladding surface. As fouling on the cladding surface worsens, under-deposit corrosion occurs between the scale and the coating. Furthermore, over time, the corrosion at the film-substrate interface intensifies, often resulting in pitting or localized dissolution of the coating (e.g., chromium coatings).

[0042] Once the coating peels off, the exposed cladding substrate (such as a zirconium alloy substrate) is directly exposed to a high-temperature, high-pressure water environment, which not only accelerates its oxidation rate but may also lead to hydride formation and mechanical property degradation. Under long-term effects, the synergistic effect of external chemical corrosion and internal stress changes may eventually induce overall coating failure or even cladding damage, directly affecting the integrity of the core fuel and the safe operation of the reactor, with extremely serious consequences.

[0043] Therefore, it is necessary to test the performance changes of the coating under the synergistic effect of external chemical corrosion and internal stress changes in advance. This specification proposes a testing device for the coating to achieve performance testing under the synergistic effect of external chemical corrosion and internal stress changes. This device can recreate the entire process of coating crack initiation → crack propagation → CRUD deposition → under-deposit corrosion → coating failure.

[0044] In some embodiments, the coating cladding test apparatus can be used to verify the evolution of chromium-coated zirconium alloy cladding tubes from crack initiation to under-deposit corrosion penetration under typical pressurized water reactor start-up and shutdown cycles, and to evaluate its effectiveness as a platform for verifying the performance of accident-resistant fuel (ATF).

[0045] Figure 2 This is a schematic diagram of the structure of a coating-coated testing device according to some embodiments; Figure 3 This is a schematic diagram of a simulated shell structure based on some embodiments.

[0046] like Figure 2 As shown, the test apparatus includes a simulated fuel rod 6, a high-temperature and high-pressure water circuit system, and a pressure supply system.

[0047] like Figure 3 As shown, the simulated fuel rod 6 includes a simulated cladding 18 and a heating rod 16.

[0048] The simulated casing 18 is used to simulate the coated casing in actual applications. The outer wall of the simulated casing 18 is coated. The simulated casing 18 defines a sealed cavity, isolating the internal cavity from the external environment and capable of withstanding a certain degree of internal pressure, which can be adjusted. In some embodiments, the simulated casing 18 adopts a tubular structure with an axial dimension greater than its radial dimension, and the wall thickness of the simulated casing 18 is uniform throughout. See [reference needed] for axial and radial dimensions in this specification. Figure 3 As shown, the axial direction is Figure 3 The vertical orientation of the view. The axial direction is perpendicular to the radial plane containing the radial direction, which is the transverse section of the simulated shell 18.

[0049] A heating rod 16 is disposed within the cavity of the simulated cladding 18. The heating rod 16 heats the cavity of the simulated cladding 18 to simulate the heat release process of the fuel pellets inside the coated cladding. In some embodiments, such as Figure 3As shown, the heating rod 16 is powered by an external power supply 14. In some embodiments, an insulating coating is sprayed onto the surface of the heating rod 16. The heating rod 16 has a bamboo-like structure, with a plurality of annular ridges 20 arranged on it. The annular ridges 20 are spaced apart axially on the heating rod 16, and the annular ridges 20 are annularly protruding in the radial direction of the heating rod 16. The outermost annular surface of the annular ridge 20 contacts the inner wall of the simulated shell 18 in the radial direction. An air gap 17 is formed between the area of ​​the heating rod 16 that is recessed relative to the annular ridges 20 and the inner wall of the simulated shell 18.

[0050] In some embodiments, when the simulated shell 18 adopts a tubular structure, the simulated shell 18 and the heating rod 16 are coaxially arranged, so that the heating effect of the heating rod 16 on the cavity of the simulated shell 18 is consistent or nearly uniform. In some embodiments, a through hole 19 is provided on the annular ridge 20, which serves as a gas flow channel within the simulated shell 18. The through hole 19 penetrates the opposite sides of the annular ridge 20 in the axial direction to maintain uniform internal pressure within the cavity. In this embodiment, the axial spacing between adjacent annular ridges 20 on the heating rod 16 is close or consistent. In some embodiments, such as Figure 4 As shown, the through hole 19 also penetrates the outermost annular surface of the annular ridge 20 in the radial direction. Figure 4 The radial plane at the ridge 20 on the heating rod 16 is shown.

[0051] By making the heating rod 16 have several axial ridges 20, and the ridges 20 contact the inner wall of the simulated shell 18, under the action of the internal pressure in the simulated shell 18, the simulated shell 18 area corresponding to the ridges 20 undergoes convex deformation, which induces stress concentration in the corresponding outer surface area of ​​the simulated shell 18. The simulated shell 18 area corresponding to adjacent ridges 20 undergoes concave deformation, which can simulate the "bamboo joint" deformation of the coating shell, thereby causing the coating on the corresponding outer surface of the simulated shell 18 to crack, thus realizing the mechanism simulation of the initiation and propagation of coating cracks.

[0052] The pressurization system inflates or deflates the cavity of the simulated casing 18 to simulate the internal pressure creep state during fuel rod heating. The pressurization system includes a gas source and a booster pump 11. In some embodiments, the gas source is an inert gas cylinder group 10 filled with a chemical inert gas. The simulated casing 18 has an inlet and an outlet, both of which communicate with its cavity. The gas source is connected to the inlet via the booster pump 11 to achieve pressurization. In some embodiments, a first retaining sleeve 15 is provided on the inlet, and the booster pump 11 is sealed to the inlet via the first retaining sleeve 15 to ensure the high-pressure airtightness of the cavity of the simulated casing 18. A gas back pressure valve 12 is provided at the outlet to achieve pressure stabilization during exhaust. In some embodiments, a second retaining sleeve 13 is provided on the outlet, and the outlet is connected to the gas back pressure valve 12 via the second retaining sleeve 13 to maintain gas flow stability.

[0053] In some embodiments, the pressure supply system periodically applies internal pressure to the cavity of the simulated cladding 18, for example, 0→12MPa→0, to simulate internal pressure fluctuations caused by reactor start-up and shutdown, with a frequency of one cycle every 24 hours, for a total of 100 cycles. In some embodiments, the pressure supply system also has the function of monitoring the integrity of the simulated cladding 18.

[0054] After being pressurized by the booster pump 11, the gas enters the interior of the simulated casing 18 through the first ferrule 15 and is discharged through the second ferrule 13 and the gas back pressure valve 12. By repeatedly charging and discharging, the internal pressure change of the simulated casing 18 can be adjusted to simulate the internal pressure creep behavior under transient power conditions.

[0055] The heating rods 16 with several annular ridges 20 and the pressure supply system described above can simulate the stress changes of the coating shell. The following combination... Figure 2 This describes a high-temperature, high-pressure water circuit system that simulates the chemical corrosion of the coating's exterior.

[0056] The high-temperature and high-pressure water loop system is used to provide a high-temperature and high-pressure water environment to simulate the primary loop of a pressurized water reactor, with the simulated cladding 18 located in the high-temperature and high-pressure water environment.

[0057] The high-temperature, high-pressure water loop system includes a material storage tank 1, a high-pressure pump 2, a heating assembly, and an autoclave 5. The material storage tank 1 stores an aqueous solution simulating the fouling chemical environment of the primary loop of a pressurized water reactor. The high-pressure pump 2 delivers the aqueous solution and applies the required pressure; its inlet is connected to the outlet of the material storage tank 1. The outlet of the high-pressure pump 2 is connected to the inlet of the heating assembly, which heats the pressurized aqueous solution. The autoclave 5 contains the pressurized and heated aqueous solution and isolates it from the outside environment, providing a high-temperature, high-pressure water environment simulating the primary loop of a pressurized water reactor. The inlet of the autoclave 5 is connected to the outlet of the heating assembly, and the simulated cladding 18 is immersed in the high-temperature, high-pressure aqueous solution within the autoclave 5. A temperature monitoring element is installed inside the autoclave 5 to monitor the temperature of the aqueous solution within it.

[0058] In some embodiments, the heating assembly includes a preheating device 3 and a heat exchange device 4. The preheating device 3 is used to preheat the pressurized aqueous solution, and its inlet is connected to the outlet of the high-pressure pump 2. The heat exchange device 4 is used to heat the pressurized aqueous solution using the heat from the discharge liquid from the autoclave. The cold end inlet of the heat exchange device 4 is connected to the outlet of the preheating device 3, the cold end outlet of the heat exchange device 4 is connected to the inlet of the autoclave 5, and the outlet of the autoclave 5 is connected to the hot end inlet of the heat exchange device 4. Since the heating rod 16 continuously heats the aqueous solution in the autoclave 5 through the simulated shell 18, the temperature of the aqueous solution discharged from the autoclave 5 (hereinafter referred to as "discharge liquid") is higher than that of the preheated aqueous solution. The heat exchange device 4 plays a reheating role. In the heat exchange device 4, the preheated aqueous solution exchanges heat with the discharge liquid from the autoclave 5, thereby reheating the preheated aqueous solution and improving the system thermal efficiency.

[0059] In some embodiments, the high-temperature, high-pressure water loop system further includes a cooling device 7 (e.g., an air cooler) and a water treatment device 9. The cooling device 7 is used to cool the regenerated effluent, and its inlet is connected to the hot-end outlet of the heat exchange device 4. The outlet of the cooling device 7 is connected to the inlet of the material storage tank 1 through the water treatment device 9, which is used to treat the cooled effluent. The water treatment device 9 treats the cooled effluent and partially returns it to the material storage tank 1 for recycling, thus completing the simulated primary loop water circulation.

[0060] In some embodiments, a liquid back pressure valve 8 is provided in the flow path between the hot end outlet of the heat exchange device 4 and the inlet of the material storage tank 1. The liquid back pressure valve 8 is used to maintain the pressure balance of the high-temperature and high-pressure water circuit system. Specifically, such as Figure 2 As shown, the liquid back pressure valve 8 is located between the cooling equipment 7 and the water treatment equipment 9. The liquid back pressure valve 8 can maintain the system pressure balance and ensure that the cooled fluid can smoothly enter the water treatment equipment 9.

[0061] By coupling the high-temperature and high-pressure water environment provided by the high-temperature and high-pressure water circuit system with the stress changes simulated by the heating rod 16 and the pressure supply system, the coating cladding test device involved in the embodiments of this specification can simulate the local nucleation boiling phenomenon induced by surface cracks of fuel rods in a high-temperature and high-pressure water environment, so as to test the performance of the coating cladding in a coupled scenario of high-temperature and high-pressure water environment and internal stress changes.

[0062] The following is a specific embodiment, which is intended to illustrate the implementation of the present invention in conjunction with the above embodiments, and does not limit the application scenarios of the present invention.

[0063] A chromium-coated simulated cladding is fitted over a heating rod to serve as a simulated fuel rod, forming a closed cavity within the simulated cladding. A small air gap (approximately 0.1 mm) is maintained between the simulated cladding and the heating rod to simulate the actual pellet-cladding gap.

[0064] Before testing, inspect the coating integrity to confirm there are no obvious defects. Record the initial cladding surface morphology and coating thickness distribution. Turn on the high-pressure pump to establish a high-temperature, high-pressure water environment and operate stably for 24 hours. Start the heating rod and gradually increase the temperature to the rated heat load (corresponding to a linear power of 45 kW / m) according to the power gradient. Simultaneously start the internal pressure circulation: apply a pressure pulse of 0→12 MPa→0 every 24 hours for 100 days (100 cycles in total). Monitor the simulated internal pressure of the cladding in real time. If abnormal pressure fluctuations are detected in the simulated internal pressure of the cladding, it indicates that the cladding tube has been damaged, and the test should be stopped immediately.

[0065] Test Results: Water quality monitoring showed a gradual increase in Ni and Fe ion concentrations in the circuit. From day 60 onwards, brown deposits were observed in the coating crack area, forming a CRUD scale layer. EIS data showed a 40% decrease in charge transfer resistance in the crack area, indicating accelerated under-deposit corrosion. After the 85th cycle, abnormal internal pressure was observed in the simulated cladding, indicating cladding damage. The test was terminated and an inspection was conducted. The simulated fuel rod was immersed in water, and the damage location was located using a pressure bubbling method. Samples were taken from the damage location for the following microstructural analysis:

[0066] 1) Metallographic and scanning electron microscopic observation of the cross section at the damaged location showed fatigue and corrosion cracking characteristics, with CRUD scale deposits near the crack and hydride accumulation inside.

[0067] 2) EDS and XRD analysis further clarified the composition and crystal structure of CRUD.

[0068] The above specific embodiments demonstrate the feasibility of the device.

[0069] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although some inventive embodiments that are currently considered useful have been discussed in the above disclosure by way of various examples, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. Rather, the claims are intended to cover all modifications and equivalent combinations that conform to the substance and scope of the embodiments in this specification.

Claims

1. A testing device for coating shells, characterized in that, The testing apparatus includes: A simulated enclosure is located in a high-temperature and high-pressure water environment. The outer wall of the simulated enclosure is coated with a coating. The simulated enclosure has a tubular structure and defines a sealed cavity. The internal pressure of the cavity is adjustable. A heating rod is disposed within the cavity of the simulated shell, coaxially arranged with the simulated shell. The heating rod has several annular ridges spaced apart axially, with the axial spacing between adjacent ridges being approximately equal. Each ridge has a radially annular protrusion. The outermost annular surface of the ridge in the radial direction contacts the inner wall of the simulated shell. A through hole is provided on the ridge, which penetrates the opposite sides of the ridge in the axial direction to maintain uniform internal pressure in the cavity. The through hole also penetrates the outermost annular surface of the ridge in the radial direction.

2. The testing apparatus for coating and shelling according to claim 1, characterized in that, The testing device includes a pressure supply system for inflating or deflating the cavity of the simulated casing to simulate the internal pressure creep state during the heating process of the fuel rod.

3. The testing apparatus for coating and shelling according to claim 2, characterized in that, The simulated shell is provided with an air inlet and an exhaust outlet, both of which are connected to the cavity; The pressure supply system includes an air source and a booster pump. The air source is connected to the air inlet through the booster pump to achieve air filling and pressurization. A gas back pressure valve is installed at the exhaust port to achieve exhaust pressure stabilization.

4. The testing apparatus for coating and shelling according to claim 1, characterized in that, The testing apparatus includes a high-temperature, high-pressure water loop system for providing a high-temperature, high-pressure water environment that simulates the primary loop of a pressurized water reactor.

5. The testing apparatus for coating and shelling according to claim 4, characterized in that, The high-temperature and high-pressure water circuit system includes: Material storage tanks are used to store aqueous solutions that simulate the chemical environment of fouling deposition water in the primary loop of the pressurized water reactor. A high-pressure pump is used to pressurize the aqueous solution, and the inlet of the high-pressure pump is connected to the outlet of the material storage tank; A heating assembly for heating the pressurized aqueous solution, wherein the inlet of the heating assembly is connected to the outlet of the high-pressure pump; An autoclave is used to contain the pressurized and heated aqueous solution and isolate it from the outside, providing the high-temperature and high-pressure water environment. The inlet of the autoclave is connected to the outlet of the heating component, and the simulated shell is placed in the aqueous solution inside the autoclave.

6. The testing apparatus for coating and shelling according to claim 5, characterized in that, The heating component includes: A preheating device is used to preheat the pressurized aqueous solution, and the inlet of the preheating device is connected to the outlet of the high-pressure pump; A heat exchange device is used to heat the pressurized aqueous solution using the heat from the effluent of the autoclave. The cold end inlet of the heat exchange device is connected to the outlet of the preheating device, the cold end outlet of the heat exchange device is connected to the inlet of the autoclave, and the outlet of the autoclave is connected to the hot end inlet of the heat exchange device.

7. The testing apparatus for coating and shelling according to claim 6, characterized in that, The high-temperature and high-pressure water circuit system also includes a cooling device and a water treatment device. The cooling device is used to cool the discharged liquid, and the inlet of the cooling device is connected to the hot end outlet of the heat exchange device. The outlet of the cooling device is connected to the inlet of the material storage tank through the water treatment device, and the water treatment device is used to treat the cooled discharged liquid.

8. The testing apparatus for coating and shelling according to claim 7, characterized in that, A liquid back pressure valve is installed in the flow path between the hot end outlet of the heat exchange equipment and the inlet of the material storage tank. The liquid back pressure valve is used to maintain the pressure balance of the high temperature and high pressure water circuit system.

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