SiC fuel element accident condition research test system and method

Abstract

The application discloses a SiC fuel element accident condition research test system and method, and relates to the field of SiC fuel element research. The test system comprises a reaction container, a heating module, a steam supply module and a water quenching thermal impact module. The reaction container has a reaction cavity axially penetrating a SiC composite cladding tube, and opposite ends of the SiC composite cladding tube are closed and respectively extend out of opposite ends of the reaction container. The heating module is arranged outside the reaction container and heats the reaction cavity. The steam supply module is connected to the reaction cavity and provides water vapor for the reaction cavity. The water quenching thermal impact module is connected to the reaction cavity and is used for conveying cooling water with a predetermined pressure into the reaction cavity to perform quenching thermal impact on the SiC composite cladding tube in the reaction cavity. The application is used for quenching thermal impact test research on the SiC composite cladding fuel element after bulging and explosion under a simulated LOCA accident condition, and is also used for simulating the bulging and explosion and quenching thermal impact behavior of the SiC composite cladding fuel element in a very short time under a RIA accident.

Description

Technical Field

[0001] This invention relates to the field of nuclear reactor fuel element accident condition research technology, and in particular to a SiC fuel element accident condition research test system and method. Background Technology

[0002] SiC composite cladding has advantages such as high melting point, corrosion resistance, high-temperature oxidation resistance, almost no decrease in strength at high temperatures, and no hydrogen production. Therefore, as an innovative accident-tolerant fuel (ATF) cladding material, it is expected to be applied to mainstream commercial pressurized water reactor nuclear power plants in the future to significantly improve the safety margin under accident conditions.

[0003] In pressurized water reactor nuclear power plants, loss-of-coolant accidents (LOCA) and reactive introduction accidents (RIA) are two typical design basis accidents. Under conventional UO2-Zr alloy fuel systems, fuel elements will undergo bulging and bursting as well as high-temperature oxidation and quenching thermal shock processes under both LOCA and RIA accidents. The difference lies in the fact that cladding RIA accidents have a higher heating rate and a shorter oxidation duration.

[0004] Currently, research on bulging, bursting, and embrittlement of SiC composite cladding under RIA (Rapid Induction and Exhaust) conditions is still lacking. There are only a few experimental studies on SiC composite cladding under LOCA (Local Oxygen-Carbide-Coating) conditions. For example, Reference 1 (Martin Steinbrueck, Mirco Grosse, et al. Oxidation of silicon carbide composites for nuclear applications at very high temperatures in steam. Progress in Color, Colorants and Coatings, 2022, 12) conducted a high-temperature steam oxygen quenching thermal shock test on SiC composite cladding tubes. Although the highest oxidation temperature reached 1845℃, the cladding tubes were only sealed without pressurization. Reference 2 (K. Furumoto, M. Okamoto et al. Out of Pile Test with SiC Cladding Simulating LOCA Conditions, TopFuel 2018, Prague Czech Republic, 30 Sep-04 Oct, 2018) conducted a LOCA burst test on the SiC composite cladding. The maximum internal pressure was 7 MPa, but due to the limitation of infrared heating capability, the maximum heating temperature was around 1600℃. The SiC composite cladding did not experience burst failure.

[0005] In existing technologies, the main focus is on off-pile simulated LOCA test studies for Zr-UO2 fuel systems, lacking understanding and testing considerations for SiC composite clad fuel elements. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an experimental system and method for studying the accident conditions of SiC fuel elements.

[0007] The technical solution adopted by this invention to solve its technical problem is: to provide a SiC fuel element accident condition research and testing system, comprising: A reaction vessel having a reaction chamber through which a SiC composite cladding tube is axially inserted, the opposite ends of the SiC composite cladding tube being closed and extending out of the opposite ends of the reaction vessel respectively; A heating module is installed outside the reaction vessel to heat the reaction chamber; A steam supply module, connected to the reaction chamber, provides steam to the reaction chamber; and The water-quenched thermal shock module is connected to the reaction chamber and is used to supply cooling water at a predetermined pressure into the reaction chamber to perform quenching thermal shock on the SiC composite cladding tube inside the reaction chamber.

[0008] Preferably, the heating module includes a spiral coil sleeved around the outer periphery of the reaction vessel; The spiral coil is connected to an external induction power supply, which heats the reaction vessel through induction heating.

[0009] Preferably, the steam supply module includes a controllable steam mixer, a gas source connected to the controllable steam mixer, and a first water tank; the output end of the controllable steam mixer is connected to the reaction vessel through a steam supply pipeline, and the controllable steam mixer supplies steam to the reaction chamber through the steam supply pipeline.

[0010] Preferably, the output end of the controllable steam mixer includes a first outlet and a second outlet, the first outlet being connected to the steam supply pipeline via a steam pipeline, and the second outlet being connected to the steam supply pipeline via an air supply pipeline; the steam pipeline and the air supply pipeline are respectively equipped with valves; When the first outlet is connected to the steam supply pipeline, the controllable steam mixer supplies steam to the reaction chamber; when the second outlet is connected to the steam supply pipeline, the controllable steam mixer supplies inert gas to the reaction chamber to vent the reaction chamber.

[0011] Preferably, the water-quenched thermal shock module includes a quenching tank and a thermal shock pipeline connecting the quenching tank and the reaction vessel; the internal space of the quenching tank includes a gas space and a cooling water space located below the gas space, and the thermal shock pipeline connects the reaction chamber and the cooling water space.

[0012] Preferably, the water quenching and impact module further includes a second water tank and a water supply pump connected between the second water tank and the quenching tank; and / or, the water quenching and impact module further includes a gas source and a pressure-bearing pipeline connected between the gas source and the quenching tank; the pressure-bearing pipeline is provided with an air filling valve.

[0013] Preferably, the reaction chamber includes a cooling chamber at the top, a sealing chamber at the bottom, and a main chamber between the cooling chamber and the sealing chamber; the reaction vessel is provided with a temperature measuring through hole and a steam exhaust through hole at one end corresponding to the cooling chamber; the reaction vessel is provided with a water vapor inlet and a water quenching inlet at one end corresponding to the sealing chamber.

[0014] Preferably, the SiC fuel element accident condition research and testing system further includes a cooling module; the cooling module includes a chiller, which is connected to the cooling chamber and the opposite ends of the SiC composite cladding tube respectively through cooling pipes.

[0015] Preferably, the cooling chamber is provided with a condensate collection ring, which defines a condensate collection ring cavity located between the outer periphery of the condensate collection ring and the inner periphery of the cooling chamber; the reaction vessel is provided with a drain hole communicating with the condensate collection ring cavity.

[0016] Preferably, the SiC fuel element accident condition research and testing system further includes a condensate collection module; the condensate collection module includes a condensate tank, which is connected to the drain hole and / or the exhaust vent hole via a condensate pipe.

[0017] Preferably, the reaction vessel includes a high-temperature glass tube, a first sleeve and a second sleeve sealed to opposite ends of the high-temperature glass tube; the first sleeve and the second sleeve are respectively provided with through holes, and the opposite ends of the SiC composite cladding tube extend out of the opposite ends of the reaction vessel through the through holes.

[0018] Preferably, the SiC fuel element accident condition research and testing system further includes a protective sleeve, which is fitted over the outside of the reaction vessel; the heating module is located inside the protective sleeve.

[0019] Preferably, the SiC fuel element accident condition research and testing system further includes a temperature and pressure measurement module; The temperature and pressure measurement module includes a pressure detection unit and a temperature detection unit; the pressure detection unit is connected to the lower end of the SiC composite clad tube and is used to detect the internal pressure of the SiC composite clad tube; the temperature detection unit includes a thermocouple and / or an infrared thermometer and is used to detect the temperature of the SiC composite clad tube. The control system receives the temperature signal detected and sent by the temperature detection unit, and controls the heating power of the heating module through a PID program, so that the SiC composite cladding tube can complete the high-temperature bulging and bursting and quenching thermal shock process according to the set temperature change mode.

[0020] The present invention also provides a test method for studying the accident conditions of SiC fuel elements, which adopts the test system for studying the accident conditions of SiC fuel elements described in any of the above. The test method for studying the accident conditions of SiC fuel elements includes a bulging burst and quenching thermal shock test method under LOCA conditions and a bulging burst and quenching thermal shock test method under RIA conditions.

[0021] Preferably, the method for bulging burst and quenching thermal shock testing under LOCA conditions includes the following steps: S11. Install the SiC composite cladding tube inside the reaction vessel; Alumina rods and graphite rods are loaded inside the SiC composite cladding tube, or a simulated core block is loaded inside the SiC composite cladding tube, the simulated core block being formed of graphite rods; S12. Start the test according to the simulated LOCA test procedure and conduct heating expansion burst and isothermal high temperature steam oxidation tests on the SiC composite cladding tube. In the heating expansion burst and isothermal high-temperature steam oxidation tests, the heating rate is ≥5℃ / s and the isothermal oxidation time is 100s~8h; S13. After completing the heating expansion burst and isothermal high-temperature steam oxidation tests, the SiC composite cladding tube is cooled down at a predetermined cooling rate and the supply of steam is stopped. When the temperature drops to 800℃±20℃, the heating power is turned off, and the SiC composite cladding tube is subjected to quenching thermal shock.

[0022] Preferably, the method for bulging burst and quenching thermal shock testing under RIA conditions includes the following steps: S21. Install the SiC composite cladding tube inside the reaction vessel; Alumina rods and graphite rods are loaded inside the SiC composite cladding tube, or a simulated core block is loaded inside the SiC composite cladding tube, the simulated core block being formed of graphite rods; S22. Start the test according to the simulated RIA test procedure and conduct heating expansion burst and isothermal high temperature steam oxidation tests on the SiC composite cladding tube. In the heating expansion burst and isothermal high-temperature steam oxidation tests, the heating rate is ≥100℃ / s and the isothermal oxidation time is 10s±1s.

[0023] S23. After completing the heating expansion burst and isothermal high-temperature steam oxidation tests, stop heating and stop supplying steam. Without cooling, quickly subject the SiC composite cladding tube to quenching thermal shock.

[0024] The beneficial effects of this invention are as follows: By combining the reaction chamber with the heating module, the steam supply module and the water quenching thermal shock module to form an experimental system, it is possible not only to conduct quenching thermal shock test research on SiC composite clad fuel elements under simulated LOCA accident conditions, but also to accurately simulate the bulging explosion and quenching thermal shock behavior of SiC composite clad fuel elements under RIA accidents in a very short time. Attached Figure Description

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a connection diagram of a SiC fuel element accident condition research and testing system according to an embodiment of the present invention; Figure 2 This is a schematic cross-sectional view of the reaction vessel in a SiC fuel element accident condition research test system according to an embodiment of the present invention. Detailed Implementation

[0026] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0027] like Figures 1-2 As shown, an embodiment of the SiC fuel element accident condition research test system of the present invention includes a reaction vessel 10, a heating module 20, a steam supply module 30, and a water quenching heat shock module 40, etc.

[0028] The reaction vessel 10 is the main component for conducting bulging burst and quenching thermal shock tests on the SiC composite cladding tube 100 under steam conditions. The reaction vessel 10 has a reaction chamber in which the SiC composite cladding tube 100 is axially inserted. The opposite ends of the SiC composite cladding tube 100 extend beyond the opposite ends of the reaction vessel 10, and are sealed by upper and lower sealing heads, respectively. A heating module 20 is located outside the reaction vessel 10 and is used to heat the reaction chamber, thereby heating the SiC composite cladding tube 100 inside the reaction chamber. A steam supply module 30 is connected to the reaction chamber and provides steam. A water quenching thermal shock module 40 is connected to the reaction chamber and is used to supply cooling water at a predetermined pressure into the reaction chamber to perform quenching thermal shock on the SiC composite cladding tube 100 inside the reaction chamber.

[0029] Specifically, refer to Figure 2 Taking a vertically positioned reaction vessel 10 as an example, the reaction chamber inside the reaction vessel 10 may include a cooling chamber 101 at the top, a sealing chamber 103 at the bottom, and a main chamber 102 located between the cooling chamber 101 and the sealing chamber 103. The main chamber 102 occupies most of the reaction chamber, meaning its axial length (height) is greater than the axial length (height) of both the cooling chamber 101 and the sealing chamber 103. The cooling chamber 101 and the sealing chamber 103 are located at the upper and lower ends of the main chamber 102, respectively, and also at opposite ends of the reaction vessel 10.

[0030] The reaction vessel 10 has a temperature measuring through-hole 104 and a steam vent 105 at one end corresponding to the cooling chamber 101. The temperature measuring through-hole 104 can serve as a thermocouple channel for thermocouple insertion for temperature measurement. The steam vent 105 serves as a steam outlet and can be further connected to a steam discharge pipeline (equipped with a steam vent valve) for steam discharge from the reaction chamber. The reaction vessel 10 has a steam inlet 106 and a water quenching inlet 107 at one end corresponding to the sealing chamber 103. The steam inlet 106 is connected to the steam supply module 30 to receive steam from the steam supply module 30. The water quenching inlet 107 is connected to the water quenching thermal shock module 40 to receive quenching cooling water from the water quenching thermal shock module 40.

[0031] The cooling chamber 101 may further be provided with a condensate collection ring 108, which defines a condensate collection ring cavity 1011 within the cooling chamber 101, located between the outer periphery of the condensate collection ring 108 and the inner periphery of the cooling chamber 101. Condensate formed after water vapor cools on the inner wall of the cooling chamber 101 is collected in the condensate collection ring cavity 1011. The reaction vessel 10 is provided with a drain hole 109 communicating with the condensate collection ring cavity 1011, through which the condensate collected in the condensate collection ring cavity 1011 is discharged from the cooling chamber 101.

[0032] exist Figure 2 In the illustrated embodiment, the condensate collection ring 108 is an annular body with an outer peripheral surface that is concave and arc-shaped. Inside the cooling chamber 101, the concave and arc-shaped surface of the condensate collection ring 108 faces the inner surface of the cooling chamber 101. The periphery of one end of the condensate collection ring 108 facing the main chamber 102 may abut against or be spaced from the inner surface of the cooling chamber 101; the opposite end of the condensate collection ring 108 (the end away from the main chamber 102) is spaced from the inner surface of the cooling chamber 101, and this space forms an opening for the condensate collection ring cavity 1011.

[0033] Further, the reaction vessel 10 may be formed of a high-temperature resistant container. In some embodiments, the reaction vessel 10 may include a high-temperature glass tube 13, a first sleeve 11, and a second sleeve 12. The opposite ends of the high-temperature glass tube 13 are open, and the first sleeve 11 and the second sleeve 12 are respectively sealed and fitted onto the opposite ends of the high-temperature glass tube 13. The axial length of the SiC composite cladding tube is greater than the axial length of the reaction vessel 10. The SiC composite cladding tube passes through the high-temperature glass tube 13 axially. The first sleeve 11 and the second sleeve 12 are respectively provided with through holes, and the opposite ends of the SiC composite cladding tube extend out of the opposite ends of the reaction vessel 10 through the through holes.

[0034] The first sleeve 11 and one end of the high-temperature glass tube 13 can be sealed together via a flange, and the second sleeve 12 and the other end of the high-temperature glass tube 13 can also be sealed together via a flange. Each sealing connection is equipped with a sealing ring; depending on the temperature of the sealing location, the sealing ring is made of a temperature-resistant material with conservative temperature characteristics to ensure a tight seal.

[0035] The cooling chamber 101 of the reaction chamber is located inside the first sleeve 11. The temperature measuring through-hole 104 and the steam exhaust through-hole 105 are respectively located on the top surface of the first sleeve 11 away from the high-temperature glass tube 13. The sealing chamber 103 is located inside the second sleeve 12. The steam inlet 106 and the water quenching inlet 107 are respectively located on the bottom surface of the second sleeve 12 away from the high-temperature glass tube 13. The main chamber of the reaction chamber is located inside the high-temperature glass tube 13. The heating expansion and bursting tests and quenching thermal shock tests of the SiC composite cladding tube 100 are all conducted inside the high-temperature glass tube 13. The selection of the high-temperature glass tube 13 as the main body of the reaction vessel has two considerations: firstly, induction heating will not heat the glass; secondly, the transparent high-temperature glass tube allows for temperature measurement and control using infrared thermometers, and also allows for real-time monitoring of the cladding expansion and bursting and quenching thermal shock behavior through a camera.

[0036] Combination Figure 1 and Figure 2 To ensure the safety of test operators, the SiC fuel element accident condition research test system also includes a protective sleeve 50, which is fitted over the outside of the reaction vessel 10. The protective sleeve 50 is fitted over at least the periphery of the high-temperature glass tube 13 of the reaction vessel 10 to prevent potential injury from splashing glass in case of accidental breakage. The protective sleeve 50 is made of steel and has appropriately sized observation windows at locations requiring observation and control.

[0037] refer to Figures 1-2The heating module 20 may include a spiral coil, which is sleeved around the outer periphery of the reaction vessel 10. The spiral coil is connected to an external induction power supply, heating the reaction vessel 10 and its internal SiC composite cladding tube 100 via induction heating. In embodiments where the reaction vessel 10 includes a high-temperature glass tube 13, the spiral coil is positioned close to but not in contact with the high-temperature glass tube 13, with sufficient pitch space for temperature measurement, control, and observation. When a protective sleeve 50 surrounds the high-temperature glass tube 13, the spiral coil is located within the protective sleeve 50, and its connecting wires are connected to the induction power supply via pre-drilled holes in the protective sleeve 50.

[0038] Corresponding to the induction heating method, the heating module 20 may also include an induction power supply.

[0039] In other embodiments, the heating module 20 may use direct current heating to heat the SiC composite clad tube 100. For direct current heating, the heating module 20 includes a heating rod assembled inside the SiC composite clad tube 100, with the end of the heating rod extending outside the SiC composite clad tube 100 and externally sealed to the electrodes and pressurization lines. The heating rod may be a graphite rod or a tungsten alloy rod.

[0040] The steam supply module 30 may include a controllable steam mixer (CEM) 31, a gas source 32, and a first water tank 33. The gas source 32 and the first water tank 33 are respectively connected to the controllable steam mixer 31 through pipelines. The inert gas (generally Ar) from the gas source (such as a gas cylinder or tank) 32 is supplied to the controllable steam mixer 31 through pipelines, and the water in the first water tank 33 is supplied to the controllable steam mixer 31 through pipelines. The output end of the controllable steam mixer 31 is connected to the reaction vessel 10 through a steam supply pipeline 34. Specifically, the steam supply pipeline 34 is connected to the steam inlet 106 on the reaction vessel 10, thereby communicating with the reaction chamber through the steam inlet 106. The inert gas and water are mixed and heated in the controllable steam mixer 31 according to a set ratio to form a mixture of Ar and steam. The mixture is introduced into the reaction chamber through the steam supply pipeline 34.

[0041] Furthermore, the output end of the controllable steam mixer 31 includes a first outlet and a second outlet. The first outlet is connected to the steam supply pipeline 34 via a steam pipeline 35, and the second outlet is connected to the steam supply pipeline 34 via an air supply pipeline 36. Valves are respectively provided on the steam pipeline 35 and the air supply pipeline 36. An air vent valve is also provided on the steam supply pipeline 34.

[0042] When the first outlet is connected to the steam supply pipeline 34 via steam pipeline 35 (with the valve on the gas supply pipeline closed and the vent valve closed after the steam flow stabilizes), the controllable steam mixer 31 can supply steam to the reaction chamber. When the second outlet is connected to the steam supply pipeline 34 via gas supply pipeline 36 (with the valve on steam pipeline 35 and the vent valve closed), the controllable steam mixer 31 can supply inert gas to the reaction chamber to vent it. When venting the reaction chamber, the inert gas supplied to the reaction chamber is high-velocity Ar.

[0043] The water-quenched thermal shock module 40 may include a quenching tank 41 and a thermal shock pipeline 42 connected between the quenching tank 41 and the reaction vessel 10. The thermal shock pipeline 42 is specifically connected to the water quenching inlet 107 on the reaction vessel 10 and communicates with the reaction chamber through the water quenching inlet 107, thereby connecting the quenching tank 41 and the reaction chamber.

[0044] The quenching tank 41 is a pressure vessel containing cooling water and inert gas. The internal space of the quenching tank 41 includes a gas space and a cooling water space located below the gas space. The cooling water space contains cooling water, and the gas space contains inert gas, maintaining a predetermined internal pressure. The thermal shock pipeline 42 specifically connects the reaction chamber and the cooling water space. A quenching valve 421 is provided on the thermal shock pipeline 42 to control its opening and closing. Opening the quenching valve 421 completes the quenching thermal shock operation on the SiC composite cladding tube 100. A drain valve 422 is also provided on the thermal shock pipeline 42; after the thermal shock test, the cooling water in the reaction chamber is discharged through the drain valve 422.

[0045] In some embodiments, the water quenching shock module 40 further includes a second water tank 43 and a water supply pump 44, the water supply pump 44 being connected between the second water tank 43 and the quenching tank 41 via a water supply pipeline 45. The top of the quenching tank 41 is provided with an interface for connecting to the water supply pipeline 45, and cooling water in the second water tank 43 is injected from the top of the quenching tank 41 through the water supply pipeline 45 and the water supply pump 44.

[0046] In some embodiments, the water quenching shock module 40 further includes a gas source (gas cylinder or gas tank) 46 and a pressure-bearing pipeline 47 connecting the gas source 46 and the quenching tank 41; the pressure-bearing pipeline 47 is equipped with an inflation valve 471. The top of the quenching tank 41 has an interface connected to the pressure-bearing pipeline 47. Inert gas from the gas source 46 enters the quenching tank 41 through the pressure-bearing pipeline 47 and the inflation valve 471, applying a certain internal pressure to the gas space of the quenching tank 41. The pressure of the gas space is measured in real time by a pressure gauge. The pressure-bearing pipeline 47 is also connected to an empty pipeline 48 and an exhaust valve 49 for gas depressurization and communication with the atmosphere during water filling.

[0047] Furthermore, the SiC fuel element accident condition research and testing system may also include a cooling module 60, which is used to cool the cooling chamber 101 of the reaction chamber and both ends of the SiC composite cladding tube 100, with circulating cooling water as the cooling medium.

[0048] The cooling module 60 may specifically include a chiller 61, which is connected to the cooling chamber 101 of the reaction chamber and the opposite ends of the SiC composite cladding tube 100 via cooling pipes 62. When the induction power supply itself does not have an integrated cooling system, the circulating cooling water of the chiller 61 also circulates to cool the induction power supply.

[0049] Furthermore, the SiC fuel element accident condition research and testing system may also include a condensate collection module. The condensate collection module includes a condensate tank 71, which is connected to a drain hole 109 and / or a steam vent hole 105 via a condensate pipe 72. A condensate valve 721 is installed on the condensate pipe 72 to prevent air from entering after the reaction chamber has been emptied.

[0050] In the embodiment where the condensate tank 71 is connected to the drain hole 109 via the condensate pipe 72, the condensate collected in the condensate collection ring cavity 1011 is discharged from the reaction vessel 10 via the condensate pipe 72 and enters the condensate tank 71.

[0051] In the embodiment where the condensate tank 71 is connected to the exhaust port 105 via the condensate pipe 72, the steam discharged through the exhaust port 105 at the top of the cooling chamber is discharged into the condensate tank 71 via the condensate pipe 72, where it is cooled and collected.

[0052] Furthermore, the SiC fuel element accident condition research and testing system also includes a temperature and pressure measurement module for measuring the temperature and pressure of the reaction chamber / SiC composite cladding tube 100. The temperature and pressure measurement module may include a pressure detection unit 81 and a temperature detection unit 82.

[0053] The pressure detection unit 81 is connected to the lower end of the SiC composite clad tube 100 and is used to measure the internal pressure of the SiC composite clad tube 100. The pressure detection unit 81 can also transmit the measured internal pressure signal to the control system (such as a measurement and control computer), and the internal pressure of the SiC composite clad tube 100 can be recorded in real time through the measurement and control program. The pressure detection unit 81 may include, but is not limited to, a pressure sensor.

[0054] The temperature detection unit 82 includes a thermocouple and / or an infrared thermometer for measuring the temperature of the SiC composite clad tube 100. The failure temperature of the SiC composite clad tube 100 can reach over 2000℃; therefore, the temperature range of RT-800℃ can be measured using a thermocouple, while temperatures above 800℃ are primarily controlled using an infrared thermometer. The temperature signal obtained from the infrared thermometer is transmitted to the control system (such as a control computer). Using this temperature signal as input, a PID program controls the heating power supply, enabling the SiC composite clad tube 100 to complete the high-temperature bulging burst and quenching thermal shock processes according to a set temperature change pattern (heating, holding, and cooling).

[0055] The present invention provides a SiC fuel element accident condition research and testing system for implementing SiC fuel element accident condition research and testing methods. These methods include bulging burst and quenching thermal shock testing methods under LOCA (Local Oscillation-Acting-Air) conditions and bulging burst and quenching thermal shock testing methods under RIA (Rapid Oscillation-Acting-Air) conditions.

[0056] refer to Figures 1-2 The test method for bulging burst and quenching thermal shock under LOCA conditions includes the following steps: S11. Install the SiC composite cladding tube 100 inside the reaction vessel 10.

[0057] Since the SiC composite clad tube 100 cannot be induction heated, a graphite rod can be used as the internal heat source for induction heating of the SiC composite clad tube 100. Specifically, two alumina rods and one graphite rod are loaded inside the SiC composite clad tube 100, with the graphite rod located between the two alumina rods.

[0058] In another embodiment, a simulated pellet is loaded inside the SiC composite cladding tube 100. The simulated pellet is formed of graphite rods, thereby more realistically simulating the characteristics of the SiC composite cladding fuel element.

[0059] The upper and lower sealing heads at opposite ends of the SiC composite cladding tube 100 may be provided with micro-through holes for pressurization, pressure measurement, etc.

[0060] The upper end of the SiC composite cladding tube 100 extending from the reaction chamber is connected to a gas cylinder via an upper sealing head for pressurizing the SiC composite cladding tube 100. The lower end of the SiC composite cladding tube 100 is connected to a pressure sensor via a lower sealing head for measuring the internal pressure of the SiC composite cladding tube 100. After the sample (SiC composite cladding tube 100) is installed, the safety valve of the gas cylinder is opened, and Ar gas is injected into the SiC composite cladding tube 100 to the set internal pressure level (e.g., 5 MPa). Then, the valve on the pressurization pipeline is closed. If the internal pressure level does not drop after maintaining the pressure for 5-10 minutes, it indicates that the sealing connection of the SiC composite cladding tube 100 is good, and subsequent tests can be carried out.

[0061] S12. Start the test according to the simulated LOCA test procedure and conduct heating expansion burst and isothermal high temperature steam oxidation tests on the SiC composite cladding tube 100.

[0062] Before conducting the heating expansion burst and isothermal high-temperature steam oxidation tests, the following preparatory work should be carried out: (1) Expel the air in the reaction chamber by controlling the purging gas in the controllable steam mixer 31, that is, close the valve on the steam pipeline 35 at the output end of the controllable steam mixer 31 and the vent valve and open the valve on the gas supply pipeline, and introduce high-flow-rate Ar gas into the reaction chamber to expel the air in the reaction chamber.

[0063] (2) Start the chiller 61 and heat the SiC composite clad tube 100 at a low power level so that the temperature of the SiC composite clad tube 100 is maintained at about 300℃.

[0064] (3) Introduce uniform and stable water vapor into the reaction chamber.

[0065] (4) Ensure that each module is working properly.

[0066] After completing the above preparations, confirm that the entire test system is in a normal and stable working state. Then, start the test program in the test computer according to the simulated LOCA test procedure and begin the heating expansion burst and isothermal high-temperature steam oxidation test of SiC composite clad tube 100.

[0067] In the heating expansion burst and isothermal high-temperature steam oxidation tests, the heating rate is ≥5℃ / s, and the isothermal oxidation time is 100s (seconds) to 8h (hours).

[0068] S13. After completing the heating expansion burst and isothermal high-temperature steam oxidation tests, the SiC composite cladding tube 100 is cooled down at a predetermined cooling rate and the supply of water vapor is stopped. When the temperature drops to 800℃±20℃, the heating power supply (induction power supply) is turned off, and the SiC composite cladding tube 100 is subjected to quenching thermal shock.

[0069] Before subjecting the SiC composite clad tube 100 to quenching thermal shock, the quenching tank 41 needs to be filled with water and pressurized, and the time when the cooling water begins to impact the SiC composite clad tube 100 after the quenching valve 421 is opened needs to be tested, so as to ensure that the SiC composite clad tube 100 can complete the quenching thermal shock at a temperature of 800℃±20℃ during the test.

[0070] After the quenching thermal shock is completed, the SiC composite cladding tube 100 is disassembled: after the cooling water in the reaction chamber stops boiling for a period of time (5 minutes), the cooling water is discharged from the reaction chamber through the drain valve 422 on the thermal shock pipeline 42, all moving parts are stopped, and then the SiC composite cladding tube 100 after the test is taken out from the reaction chamber to complete one test.

[0071] refer to Figures 1-2 The test method for bulging burst and quenching thermal shock under RIA conditions includes the following steps: S21. Install the SiC composite cladding tube 100 inside the reaction vessel 10.

[0072] Since the SiC composite clad tube 100 cannot be induction heated, a graphite rod can be used as the internal heat source for induction heating of the SiC composite clad tube 100. Specifically, two alumina rods and one graphite rod are loaded inside the SiC composite clad tube 100, with the graphite rod located between the two alumina rods.

[0073] In another embodiment, a simulated pellet is loaded inside the SiC composite cladding tube 100. The simulated pellet is formed of graphite rods, thereby more realistically simulating the characteristics of the SiC composite cladding fuel element.

[0074] The upper and lower sealing heads at opposite ends of the SiC composite cladding tube 100 may be provided with micro-through holes for pressurization, pressure measurement, etc.

[0075] The upper end of the SiC composite cladding tube 100 extending from the reaction chamber is connected to a gas cylinder via an upper sealing head for pressurizing the SiC composite cladding tube 100. The lower end of the SiC composite cladding tube 100 is connected to a pressure sensor via a lower sealing head for measuring the internal pressure of the SiC composite cladding tube 100. After the sample (SiC composite cladding tube 100) is installed, the safety valve of the gas cylinder is opened, and Ar gas is injected into the SiC composite cladding tube 100 to the set internal pressure level (e.g., 5 MPa). Then, the valve on the pressurization pipeline is closed. If the internal pressure level does not drop after maintaining the pressure for 5-10 minutes, it indicates that the sealing connection of the SiC composite cladding tube 100 is good, and subsequent tests can be carried out.

[0076] S22. The test was started according to the simulated RIA test procedure, and the SiC composite cladding tube 100 was subjected to heating expansion burst and isothermal high temperature steam oxidation tests.

[0077] Before conducting the heating expansion burst and isothermal high-temperature steam oxidation tests, the following preparatory work should be carried out: (1) Expel the air in the reaction chamber by controlling the purging gas in the controllable steam mixer 31, that is, close the valve on the steam pipeline 35 at the output end of the controllable steam mixer 31 and the vent valve and open the valve on the gas supply pipeline, and introduce high-flow-rate Ar gas into the reaction chamber to expel the air in the reaction chamber.

[0078] (2) Start the chiller 61 and heat the SiC composite clad tube 100 at a low power level so that the temperature of the SiC composite clad tube 100 is maintained at about 300℃.

[0079] (3) Introduce uniform and stable water vapor into the reaction chamber.

[0080] (4) Ensure that each module is working properly.

[0081] After all the above preparations are completed, confirm that the entire test system is in a normal and stable working state, and then start the test program in the test computer according to the simulated RIA test program to begin the heating expansion burst and isothermal high temperature steam oxidation test of SiC composite clad tube 100.

[0082] In the heating expansion burst and isothermal high-temperature steam oxidation tests, the heating rate is ≥100℃ / s and the isothermal oxidation time is 10s±1s.

[0083] S23. After completing the heating expansion burst and isothermal high-temperature steam oxidation tests, stop heating and stop supplying steam, and quickly open the quenching valve 421 to perform quenching thermal shock on the SiC composite cladding tube 100.

[0084] Before subjecting the SiC composite cladding tube 100 to quenching thermal shock, the quenching tank 41 needs to be filled with water and pressurized, and the time when the cooling water begins to impact the SiC composite cladding tube 100 after the quenching valve 421 is opened needs to be tested. It is necessary to ensure that the quenching thermal shock of the SiC composite cladding tube 100 is achieved at the highest possible temperature, so as to simulate the quenching thermal shock conditions of the in-core RIA as realistically as possible.

[0085] After the quenching thermal shock is completed, the SiC composite cladding tube 100 is disassembled: after the cooling water in the reaction chamber stops boiling for a period of time (5 minutes), the cooling water is discharged from the reaction chamber through the drain valve 422 on the thermal shock pipeline 42, all moving parts are stopped, and then the SiC composite cladding tube 100 after the test is taken out from the reaction chamber to complete one test.

[0086] The test system and method of the present invention can realize the high-temperature bulging and bursting and oxidation quenching thermal shock process experienced by SiC composite clad fuel elements after DNB under accident conditions. It is not only applicable to LOCA accident conditions, but also to RIA accident conditions with ultra-high heating rate (≥100℃ / s) and extremely short oxidation time (10s), and can match the high-temperature failure temperature (2000℃ and above) that SiC composite clad fuel elements can reach.

[0087] On the other hand, this invention does not consider other failure mechanisms such as PCMI. The graphite rod assembled inside the cladding tube is only used for induction heating. Therefore, the assembly of the fuel element is relatively simple. Moreover, the connection and sealing of the SiC composite cladding tube is carried out outside the reaction chamber. Therefore, the complicated sealing connection method can be eliminated. The water-cooled glue is directly used for bonding and sealing. The cladding tube can be directly removed as a whole after the test. It is convenient, quick and inexpensive, and facilitates large-scale testing.

[0088] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A test system for studying accident conditions of SiC fuel elements, characterized in that, include: A reaction vessel having a reaction chamber through which a SiC composite cladding tube is axially inserted, the opposite ends of the SiC composite cladding tube being closed and extending out of the opposite ends of the reaction vessel respectively; A heating module is installed outside the reaction vessel to heat the reaction chamber; A steam supply module is connected to the reaction chamber and provides steam to the reaction chamber; as well as The water-quenched thermal shock module is connected to the reaction chamber and is used to supply cooling water at a predetermined pressure into the reaction chamber to perform quenching thermal shock on the SiC composite cladding tube inside the reaction chamber.

2. The SiC fuel element accident condition research and testing system according to claim 1, characterized in that, The heating module includes a spiral coil, which is sleeved on the outer periphery of the reaction vessel; The spiral coil is connected to an external induction power supply, which heats the reaction vessel through induction heating.

3. The SiC fuel element accident condition research and testing system according to claim 1, characterized in that, The steam supply module includes a controllable steam mixer, a gas source connected to the controllable steam mixer, and a first water tank. The output end of the controllable steam mixer is connected to the reaction vessel through a steam supply pipeline, and the controllable steam mixer supplies water vapor to the reaction chamber through the steam supply pipeline.

4. The SiC fuel element accident condition research and testing system according to claim 3, characterized in that, The output end of the controllable steam mixer includes a first outlet and a second outlet. The first outlet is connected to the steam supply pipeline via a steam pipeline, and the second outlet is connected to the steam supply pipeline via an air supply pipeline. Valves are provided on the steam pipeline and the air supply pipeline respectively. When the first outlet is connected to the steam supply pipeline, the controllable steam mixer supplies steam to the reaction chamber; when the second outlet is connected to the steam supply pipeline, the controllable steam mixer supplies inert gas to the reaction chamber to vent the reaction chamber.

5. The SiC fuel element accident condition research and testing system according to claim 1, characterized in that, The water-quenched thermal shock module includes a quenching tank and a thermal shock pipeline connecting the quenching tank and the reaction vessel. The internal space of the quenching tank includes a gas space and a cooling water space located below the gas space, and the thermal shock pipeline connects the reaction chamber and the cooling water space.

6. The SiC fuel element accident condition research and testing system according to claim 5, characterized in that, The water quenching and heat shock module further includes a second water tank and a water supply pump connected between the second water tank and the quenching tank; and / or, The water quenching and shock module also includes a gas source and a pressure-bearing pipeline connected between the gas source and the quenching tank; the pressure-bearing pipeline is equipped with an air filling valve.

7. The SiC fuel element accident condition research and testing system according to claim 1, characterized in that, The reaction chamber includes a cooling chamber at the top, a sealing chamber at the bottom, and a main chamber located between the cooling chamber and the sealing chamber. The reaction vessel is provided with a temperature measuring through hole and a steam exhaust through hole at one end corresponding to the cooling chamber, respectively connected to the cooling chamber; the reaction vessel is provided with a water vapor inlet and a water quenching inlet at one end corresponding to the sealing chamber, respectively connected to the sealing chamber.

8. The SiC fuel element accident condition research and testing system according to claim 7, characterized in that, The SiC fuel element accident condition research and testing system also includes a cooling module; The cooling module includes a chiller, which is connected to the cooling chamber and the opposite ends of the SiC composite cladding tube via cooling pipes.

9. The SiC fuel element accident condition research and testing system according to claim 7, characterized in that, The cooling chamber is provided with a condensate collection ring, which defines a condensate collection ring cavity located between the outer periphery of the condensate collection ring and the inner periphery of the cooling chamber. The reaction vessel is provided with a drain hole that connects to the condensate collection ring cavity.

10. The SiC fuel element accident condition research and testing system according to claim 9, characterized in that, The SiC fuel element accident condition research and testing system also includes a condensate collection module; The condensate collection module includes a condensate tank, which is connected to the drain hole and / or the steam vent hole via a condensate pipe.

11. The SiC fuel element accident condition research and testing system according to claim 7, characterized in that, The reaction vessel includes a high-temperature glass tube, a first sleeve and a second sleeve sealed to opposite ends of the high-temperature glass tube; the first sleeve and the second sleeve are respectively provided with through holes, and the opposite ends of the SiC composite shell tube extend out of the opposite ends of the reaction vessel through the through holes.

12. The SiC fuel element accident condition research and testing system according to any one of claims 1-11, characterized in that, The SiC fuel element accident condition research and testing system also includes a protective sleeve, which is fitted over the outside of the reaction vessel; the heating module is located inside the protective sleeve.

13. The SiC fuel element accident condition research and testing system according to any one of claims 1-11, characterized in that, The SiC fuel element accident condition research and testing system also includes a temperature and pressure measurement module; The temperature and pressure measurement module includes a pressure detection unit and a temperature detection unit; the pressure detection unit is connected to the lower end of the SiC composite clad tube and is used to detect the internal pressure of the SiC composite clad tube; the temperature detection unit includes a thermocouple and / or an infrared thermometer and is used to detect the temperature of the SiC composite clad tube. The control system receives the temperature signal detected and sent by the temperature detection unit, and controls the heating power of the heating module through a PID program, so that the SiC composite cladding tube can complete the high-temperature bulging and bursting and quenching thermal shock process according to the set temperature change mode.

14. A test method for studying accident conditions of SiC fuel elements, characterized in that, The SiC fuel element accident condition research test system according to any one of claims 1-13 is adopted, and the SiC fuel element accident condition research test method includes the bulging burst and quenching thermal shock test method under LOCA condition and the bulging burst and quenching thermal shock test method under RIA condition.

15. The experimental method for studying accident conditions of SiC fuel elements according to claim 14, characterized in that, The method for bulging burst and quenching thermal shock testing under LOCA conditions includes the following steps: S11. Install the SiC composite cladding tube inside the reaction vessel; Alumina rods and graphite rods are loaded inside the SiC composite cladding tube, or a simulated core block is loaded inside the SiC composite cladding tube, the simulated core block being formed of graphite rods; S12. Start the test according to the simulated LOCA test procedure and conduct heating expansion burst and isothermal high temperature steam oxidation tests on the SiC composite cladding tube. In the heating expansion burst and isothermal high-temperature steam oxidation tests, the heating rate is ≥5℃ / s and the isothermal oxidation time is 100s~8h; S13. After completing the heating expansion burst and isothermal high-temperature steam oxidation tests, the SiC composite cladding tube is cooled down at a predetermined cooling rate and the supply of steam is stopped. When the temperature drops to 800℃±20℃, the heating power is turned off, and the SiC composite cladding tube is subjected to quenching thermal shock.

16. The experimental method for studying accident conditions of SiC fuel elements according to claim 14, characterized in that, The method for bulging burst and quenching thermal shock testing under RIA conditions includes the following steps: S21. Install the SiC composite cladding tube inside the reaction vessel; Alumina rods and graphite rods are loaded inside the SiC composite cladding tube, or a simulated core block is loaded inside the SiC composite cladding tube, the simulated core block being formed of graphite rods; S22. Start the test according to the simulated RIA test procedure and conduct heating expansion burst and isothermal high temperature steam oxidation tests on the SiC composite cladding tube. In the heating expansion burst and isothermal high-temperature steam oxidation tests, the heating rate is ≥100℃ / s and the isothermal oxidation time is 10s±1s. S23. After completing the heating expansion burst and isothermal high-temperature steam oxidation tests, stop heating and stop supplying steam, and quickly subject the SiC composite cladding tube to quenching thermal shock.

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