Method for cooling reactor core and steam generator after emergency shutdown of high-temperature gas-cooled reactor

Abstract

The present invention discloses a method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor, which comprises the following steps: S1: discharging helium in the primary circuit of the reactor to adjust the internal and external pressure difference of the heat transfer tubes of the steam generator; S2: cooling the shell of the steam generator; S3: draining the water stored in the steam generator and the main feed water pipeline; S4: passing uniform-temperature steam through the steam generator to perform a uniform-temperature treatment on the steam generator; S5: injecting water into the heat transfer tubes and the connecting pipelines thereof and boosting the pressure to establish a stable large-flow circulation; S6: filling helium into the primary circuit of the reactor to increase the helium pressure and density in the primary circuit of the reactor; S7: starting the helium purification system and the helium compressor to establish a small-flow helium circulation in the primary circuit of the reactor to cool the reactor core. This method can prevent high-temperature components from experiencing cold / hot shocks, ensure the safe operation of the reactor, shorten the cooling time, and reconstruct the primary circuit circulation and the secondary circuit circulation to meet the conditions for restarting the reactor.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power plant operation, and particularly relates to a method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor. Background Art

[0002] The modular high-temperature gas-cooled reactor independently developed in China has the safety characteristics of the fourth-generation advanced nuclear reactor. Helium is used as the primary coolant, and the outlet temperature of the reactor core can reach 750°C; a helical tube once-through steam generator is adopted, and the secondary loop can generate high-temperature and high-pressure steam above 570°C. After an emergency shutdown of the high-temperature gas-cooled reactor, the main helium blower will be quickly stopped, the control rods will be dropped, the blower baffle will be closed, and the inlet and outlet isolation valves of the steam generator will be quickly closed to terminate the forced circulation of the primary and secondary loops. After an emergency shutdown, the main difficulties in restarting the reactor are as follows: the structural components of the reactor core and steam generator still continuously bear high temperature and high pressure, approaching the material tolerance limit; the energy balance and mass balance of the forced circulation heat transfer in the primary and secondary loops are broken, and the thermal-hydraulic state of the working medium changes greatly compared with that before shutdown; it is difficult to accurately synchronously control the flow rates of the primary and secondary loops. In this case, if the reactor is directly restarted, the temperatures of the working media in the primary and secondary loops will inevitably fluctuate greatly, and the reactor core, the heat transfer tubes of the steam generator, and the outlet tube sheet will be subjected to cold / hot shocks, and large thermal stresses and fatigue damages will be formed inside the components, which is extremely harmful to the safe operation of the reactor. Therefore, before restarting the reactor, it is necessary to cool down and equalize the temperature of the reactor core and steam generator, eliminate the temperature fluctuations of the working medium, and safely reconstruct the primary and secondary loop circulations.

[0003] At present, there is no mature method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor in the world. Only by directly restarting the reactor with a relatively small flow rate of the primary and secondary loops, this method causes great damage to the equipment. If no measures are taken and only natural cooling is relied on, the cooling time of the reactor core and steam generator is too long, resulting in a large economic loss. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. For this reason, an object of the present invention is to provide a method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor, which can safely and relatively quickly cool the reactor core and steam generator, and reconstruct the primary loop circulation and secondary loop circulation to meet the conditions for restarting the reactor.

[0005] According to an embodiment of the present invention, a method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor includes the following steps:

[0006] S1: Discharge the helium in the primary loop of the reactor to adjust the internal and external pressure difference of the heat transfer tubes of the steam generator;

[0007] S2: Cool the housing of the steam generator;

[0008] S3: Drain all the water in the steam generator and the main feed water pipeline;

[0009] S4: Pass uniform temperature steam through the steam generator to perform a uniform temperature treatment on the steam generator;

[0010] S5: Inject water into the heat transfer tubes and the connecting pipelines communicating with the heat transfer tubes and boost the pressure to establish a stable large flow rate circulation;

[0011] S6: Fill helium into the primary circuit of the reactor to increase the helium pressure and density in the primary circuit of the reactor;

[0012] S7: Start the helium purification system and the helium compressor to establish a small flow rate helium circulation in the primary circuit of the reactor to cool the reactor core.

[0013] In order to shorten the total cooling time of the reactor core and the steam generator, first perform step S1 and step S2 simultaneously; then perform step S3 and step S4 in sequence, and then perform step S5, step S6 and step S7 simultaneously.

[0014] According to the method for cooling the reactor core and the steam generator after an emergency shutdown of a high-temperature gas-cooled reactor according to an embodiment of the present invention, the following advantages are achieved: First, by taking measures such as first cooling the housing of the steam generator with compressed air, then equalizing the temperature with a small flow rate of slightly superheated steam, establishing a large flow rate water circulation in the heat transfer tubes, and establishing a small flow rate helium circulation outside the heat transfer tubes, the large fluctuations in the fluid temperature in the heat transfer tubes are suppressed, and the high-temperature components of the reactor core and the steam generator are prevented from suffering cold / hot shocks, ensuring the safe operation of the reactor; Second, an active cooling method is adopted to cool the reactor core and the steam generator, greatly shortening the cooling time and saving the operating cost. In short, through the method for cooling the reactor core and the steam generator after an emergency shutdown of a high-temperature gas-cooled reactor according to an embodiment of the present invention, the reactor core and the steam generator can be cooled safely and relatively quickly, and the primary circuit circulation and the secondary circuit circulation can be rebuilt to meet the conditions for restarting the reactor.

[0015] In some embodiments, step S1 is specifically: using the pressure difference between the helium pressure in the primary circuit of the reactor and the pressure in the helium storage tank or a helium compressor to discharge the helium in the primary circuit of the reactor to the helium storage tank, so that the pressure difference inside and outside the heat transfer tubes satisfies the following relational expression:

[0016] -8.0 ≤ P1 - P2 ≤ 2.5 (1)

[0017] Where P1 is the pressure outside the heat transfer tube; P2 is the pressure inside the heat transfer tube; the unit of both is MPa.a.

[0018] In some embodiments, step S2 is specifically: cooling the housing with compressed air.

[0019] In some embodiments, step S2 is more specifically: spraying compressed air onto the outer wall surface of the housing through an air cooler, and the compressed air flows along the outer wall surface of the housing to cool the housing.

[0020] In some embodiments, step S3 is specifically: draining the water stored in the heat transfer tubes and the main feed water pipeline into a discharge buffer tank, and then draining the water in the discharge buffer tank into a condenser or a drainage monitoring pool through a drainage pump.

[0021] In some embodiments, step S4 is specifically: introducing the uniform temperature steam into the heat transfer tubes through the main feed water pipeline, and after heat exchange with the heat transfer tubes, the inlet tube sheet and the outlet tube sheet, discharging from the steam generator.

[0022] In some embodiments, the flow rate of the uniform temperature steam is less than 1 t / h, the uniform temperature steam is slightly superheated steam, the degree of superheat of the slightly superheated steam is 5 - 10 °C, and the duration of the uniform temperature treatment is more than 8 h.

[0023] In some embodiments, step S5 is specifically: starting the main feed water system, injecting water into the heat transfer tubes and the connecting pipelines connected to the heat transfer tubes through the main feed water pipeline and boosting the pressure to establish a stable large-flow circulation.

[0024] In some embodiments, step S6 is specifically: discharging the helium in the helium storage tank into the primary circuit of the reactor by using the pressure difference between the pressure in the helium storage tank and the helium pressure in the primary circuit of the reactor or the helium compressor, so that the internal and external pressure difference of the heat transfer tubes satisfies the relation formula (1).

[0025] In some embodiments, step S7 is specifically: after the helium purification system and the helium compressor are started, the helium compressor drives the helium in the helium storage tank into the primary circuit of the reactor, successively exchanges heat with the reactor core and the steam generator, transfers the heat of the reactor core to the water in the heat transfer tubes, and finally returns to the helium purification system for cooling.

[0026] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, wherein:

[0028] Figure 1Schematic diagram of the method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor according to an embodiment of the present invention.

[0029] Reference numerals:

[0030] Reactor core 10; steam generator 20; inlet tube sheet 21; outlet tube sheet 22; heat transfer tubes 23; housing 24; air cooler 30; compressed air system 31; air main pipe 32; gas transmission branch pipe 33; external thermal insulation layer 41; air-conditioning return air opening 42; negative pressure ventilation system 43; compartment 44; environment 45; helium purification system 51; helium compressor 52; helium storage tank 53; demineralized water system 61; discharge buffer tank 62; drainage pump 63; drainage monitoring pool 64; main feed water system 71; auxiliary steam system 72; main feed water pipe 73; feed water isolation valve 74; steam-water separator 75; condenser 76. Detailed implementation manners

[0031] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0032] In order to clearly describe the method for cooling the reactor core 10 and steam generator 20 after an emergency shutdown of a high-temperature gas-cooled reactor according to an embodiment of the present invention, the structure of the high-temperature gas-cooled reactor will be described first here.

[0033] As Figure 1 shown, the high-temperature gas-cooled reactor includes a reactor, a steam generator 20, an air cooler 30, an external thermal insulation layer 41, an air-conditioning return air opening 42, a negative pressure ventilation system 43, a compartment 44, an environment 45, a helium purification system 51, a helium compressor 52, a helium storage tank 53, a demineralized water system 61, a discharge buffer tank 62, a drainage pump 63, a drainage monitoring pool 64, a main feed water system 71, an auxiliary steam system 72, a main feed water pipe 73, a feed water isolation valve 74, a steam-water separator 75, and a condenser 76. Among them, a reactor core 10 is provided in the reactor, the steam generator 20 includes a housing 24, heat transfer tubes 23, an inlet tube sheet 21, and an outlet tube sheet 22, and the air cooler 30 includes a compressed air system 31, an air main pipe 32, and a gas transmission branch pipe 33; the connection relationships of the above components are as Figure 1 shown. It should be noted that among the above components, except for the air cooler 30, the rest of the components are the original structures of the high-temperature gas-cooled reactor.

[0034] Next, refer to Figure 1 to describe the method for cooling the reactor core 10 and steam generator 20 after an emergency shutdown of a high-temperature gas-cooled reactor according to an embodiment of the present invention.

[0035] After the reactor triggers an emergency shutdown, the fan baffle is closed, and the inlet and outlet isolation valves of the steam generator 20 are interlocked to close, isolating the steam generator 20 from other equipment and pipelines in the secondary circuit. After excluding accidents such as loss of cooling, loss of pressure, primary circuit break, and secondary circuit break, and confirming that the conditions are met, the core 10 and the steam generator 20 can be cooled, including the following steps:

[0036] S1: Drain the helium in the primary circuit of the reactor to adjust the pressure difference between the inside and outside of the heat transfer tubes 23 of the steam generator 20. It can be understood that since the primary circuit of the reactor needs to be isothermalized in the subsequent steps, the absolute pressure inside the heat transfer tubes 23 will decrease at that time. To avoid excessive pressure difference between the inside and outside of the heat transfer tubes 23, it is necessary to first drain the helium in the primary circuit of the reactor and lower the pressure in the primary circuit of the reactor. The pressure in the primary circuit of the reactor is the external pressure of the heat transfer tubes 23 inside the steam generator 20. That is to say, by lowering the external pressure of the heat transfer tubes 23, the pressure difference between the inside and outside of the heat transfer tubes 23 can be adjusted, so as to avoid excessive pressure difference on the heat transfer tubes 23, the inlet tube sheet 21, and the outlet tube sheet 22.

[0037] S2: Cool the shell 24 of the steam generator 20. It can be understood that when the internal components of the steam generator 20, such as the heat transfer tubes 23, are still in a high-temperature and high-pressure state, first cooling the shell 24 of the steam generator 20 and starting from the relatively low-temperature shell 24 of the steam generator 20 can avoid cold shock to the high-temperature heat transfer tubes 23 and the outlet tube sheet 22, reduce the thermal stress during the cooling process, and is beneficial to the safety of the equipment.

[0038] S3: Drain all the water in the steam generator 20 and the main feed water pipeline 73. In this way, it is avoided that the isothermalizing steam will carry water to the relatively high-temperature outlet tube sheet 22 during the subsequent isothermalizing process, preventing the outlet tube sheet 22 from suffering cold shock.

[0039] S4: Pass isothermalizing steam through the steam generator 20 to perform isothermalizing treatment on the steam generator 20. It can be understood that after the end of steps S2 and S3, the temperature of the main structure of the steam generator 20 has been greatly reduced. At this time, isothermalizing steam should be quickly passed through the main feed water pipeline 73 into the heat transfer tubes 23 to make the temperatures of the inlet tube sheet 21, the outlet tube sheet 22, the heat transfer tubes 23, and the connected metal components close to the temperature of the isothermalizing steam, reduce the temperature difference between the main feed water pipeline 73, the inlet tube sheet 21, the outlet tube sheet 22, the heat transfer tubes 23, and the connected metal components, and make the temperature of the steam generator 20 as balanced as possible.

[0040] S5: Inject water into the heat transfer tubes 23 and the connecting pipes communicating with the heat transfer tubes 23 and boost the pressure to establish a stable large-flow circulation. It can be understood that after the end of step S4, the temperatures of the inlet tube sheet 21, the outlet tube sheet 22, the heat transfer tubes 23 and the connected metal components are already close to the steam temperature. At this time, after filling the heat transfer tubes 23 and their connecting pipes with water, start the main feed water system 71, increase the pressure and flow rate, and establish a large-flow stable circulation. In this way, after starting the helium compressor 52, the water temperature at the outlet of the steam generator 20 will not fluctuate significantly, avoiding cold / hot shocks to the outlet tube sheet 22.

[0041] S6: Fill the primary circuit of the reactor with helium to increase the helium pressure and density in the primary circuit of the reactor. In this way, the heat transfer coefficient between the core 10 and the outside of the heat transfer tubes 23 can be increased, and the cooling rate of the core 10 can be accelerated.

[0042] S7: Start the helium purification system 51 and the helium compressor 52 to establish a small-flow helium circulation in the primary circuit of the reactor to cool the core 10. It can be understood that a smaller helium flow rate can ensure that the outlet temperature of the steam generator 20 will not rise significantly, avoiding thermal shocks.

[0043] To shorten the total cooling time of the core 10 and the steam generator 20, first perform step S1 and step S2 simultaneously; then perform step S3 and step S4 in sequence, and then perform step S5, step S6 and step S7 simultaneously.

[0044] According to the method for cooling the core 10 and the steam generator 20 after an emergency shutdown of a high-temperature gas-cooled reactor according to an embodiment of the present invention, the following advantages are obtained: First, by taking measures such as first cooling the shell 24 of the steam generator 20 with compressed air, then equalizing the temperature with a small-flow slightly superheated steam, and establishing a large-flow water circulation in the heat transfer tubes 23 and a small-flow helium circulation outside the heat transfer tubes 23, the large fluctuations in the temperature of the fluid in the heat transfer tubes 23 are suppressed, avoiding cold / hot shocks to the high-temperature components of the core 10 and the steam generator 20, and ensuring the safe operation of the reactor; Second, an active cooling method is adopted to cool the reactor core 10 and the steam generator 20, greatly shortening the cooling time and saving the operating cost. In short, through the method for cooling the core 10 and the steam generator 20 after an emergency shutdown of a high-temperature gas-cooled reactor according to an embodiment of the present invention, the reactor core 10 and the steam generator 20 can be cooled safely and relatively quickly, and the primary circuit circulation and the secondary circuit circulation can be rebuilt to meet the conditions for restarting the reactor.

[0045] In some embodiments, step S1 is specifically: using the pressure difference between the helium pressure in the primary circuit of the reactor and the pressure in the helium storage tank 53 or the helium compressor 52 to discharge the helium in the primary circuit of the reactor to the helium storage tank 53, so that the internal and external pressure differences of the heat transfer tubes 23 satisfy the following relational expression:

[0046] -8.0 ≤ P1 - P2 ≤ 2.5 (1)

[0047] Where P1 is the external pressure of the heat transfer tube 23, which is also the primary circuit pressure of the reactor; P2 is the internal pressure of the heat transfer tube 23, which is the secondary side pressure of the steam generator 20, that is, the secondary circuit pressure; the unit of both is MPa.a.

[0048] It can be understood that since uniform-temperature steam needs to be introduced into the heat transfer tube 23 and its connected pipes for uniform-temperature treatment in subsequent steps, the absolute pressure inside the heat transfer tube 23 will drop to 1.1 - 1.7 MPa at that time. To avoid too large a pressure difference between the inside and outside of the heat transfer tube 23, it is necessary to use the helium purification system 51 to recover the helium in the primary circuit of the reactor to the helium storage tank 53 by using the pressure difference or through the helium compressor 52, thereby reducing the primary circuit pressure of the reactor, that is, reducing the external pressure of the heat transfer tube 23. During the pressure regulation process, it is necessary to ensure that the primary circuit pressure and the secondary circuit pressure always satisfy the above relationship (1). That is to say, the pressure difference between the inside and outside of the heat transfer tube 23 is adjusted by reducing the external pressure of the heat transfer tube 23, so as to avoid the heat transfer tube 23, the inlet tube sheet 21 and the outlet tube sheet 22 from bearing too large a pressure difference.

[0049] It should be noted that after the high-temperature gas-cooled reactor is scrammed, the helium pressure in the primary circuit of the reactor is higher than the pressure in the helium storage tank 53, and there is a pressure difference between the helium pressure in the primary circuit of the reactor and the pressure in the helium storage tank 53. This pressure difference can cause the helium in the primary circuit of the reactor to be discharged into the helium storage tank 53 without the drive of the helium compressor 52. When the helium pressure in the primary circuit of the reactor drops to the same as the pressure in the helium storage tank 53, it is necessary to drive the helium in the primary circuit of the reactor into the helium storage tank 53 through the helium compressor 52 to further reduce the primary circuit pressure of the reactor.

[0050] In some embodiments, step S2 is specifically as follows: the housing 24 is cooled by compressed air. To perform this step, an air cooler 30 is specifically designed. Air is ejected onto the outer wall surface of the housing 24 through the air cooler 30, and the air flows along the outer wall surface of the housing 24 to cool the housing 24. Specifically, the air cooler 30 includes a compressed air system 31, an air main pipe 32, and air delivery branch pipes 33. The air main pipe 32 and the air delivery branch pipes 33 are arranged at the outer wall surface of the housing 24. The air delivery branch pipes 33 are uniformly arranged in the circumferential direction of the housing 24, and the axial direction of the air delivery branch pipes 33 is parallel to the axial direction of the housing 24. The compressed air system 31 feeds normal-temperature compressed air into the air main pipe 32, with a flow rate of 0 - 40 Nm3 / min. Then the compressed air enters the air delivery branch pipes 33 and is ejected onto the outer wall surface of the housing 24 through small holes formed in the pipe walls of the air delivery branch pipes 33 to cool the housing 24. After that, the air continues to flow upward in the channel formed between the housing 24 and the outer thermal insulation layer 41, converges at the upper part of the steam generator 20, and is finally transported to the air return opening 42 of the air conditioner. After being cooled by the air conditioning system, part of the air is discharged to the environment 45 by the negative pressure ventilation system 43, and the other part of the air enters the cabin 44. When the temperature of the outlet tube sheet 22 drops to the same as the temperature of the uniform-temperature steam (see Tables 1 and 2), this step ends.

[0051] When the high-temperature gas-cooled reactor is shut down emergently, when the internal components of the steam generator 20 are still in a high-temperature and high-pressure state, by cooling the housing 24 with compressed air, starting from the relatively cooler housing 24 of the steam generator 20, and utilizing the heat conduction and natural convection inside the steam generator, the relatively hotter outlet tube sheet 22 and the heat transfer tubes 23 can be cooled, which can avoid the outlet tube sheet 22 and the heat transfer tubes 23 from suffering cold shocks, reduce the thermal stress during the cooling process, and is beneficial to the safety of the equipment.

[0052] In some embodiments, step S3 is specifically as follows: the water stored in the heat transfer tubes 23 and the main feed water pipeline 73 is drained into the discharge buffer tank 62, and then the water in the discharge buffer tank 62 is drained into the condenser 76 or the secondary circuit drainage monitoring pool 64 by a drainage pump 63.

[0053] Since after the high-temperature gas-cooled reactor is shut down emergently, there is secondary circuit circulating water in both the lower part of the heat transfer tubes 23 and the main feed water pipeline 73. In addition, after step S2, part of the steam in the heat transfer tubes 23 will also condense into liquid water. To perform the subsequent operation steps, it is necessary to drain all this stored water. After the high-temperature gas-cooled reactor is shut down emergently, the feed water isolation valve 74 is closed to isolate the main feed water pipeline 73 and the steam generator 20. Therefore, the heat transfer tubes 23 and the main feed water pipeline 73 are drained separately.

[0054] The heat transfer tube 23 and the main feed water pipe 73 are respectively connected to the discharge buffer tank 62. Since the steam generator 20 has been cooled by the air cooler for a long time before draining, the stored water inside is saturated water at a relatively low pressure (1.1 - 2.5 MPa.a). After flowing through the orifice plate and the valve, it further cools down, reduces pressure, and vaporizes, and finally enters the discharge buffer tank 62 in the state of atmospheric pressure steam-water mixture. The stored water in the main feed water pipe 73 cools down and reduces pressure to saturated water at atmospheric pressure after upstream drain and pressure relief, and drains to the discharge buffer tank 62 by gravity. The demineralized water system 61 produces normal temperature demineralized water and transports it to the discharge buffer tank 62, where it is mixed with the water discharged from the heat transfer tube 23 and the main feed water pipe 73, and then is transported to the secondary circuit drain monitoring pool or the condenser 76 through the drain pump 63 and the downstream pipeline (the pipeline between the condenser 76 and the drain pump 63 is not drawn in Figure 1 . The amount of demineralized water ensures that the inlet temperature of the drain pump 63 is lower than 60 °C.

[0055] By draining the stored water in the heat transfer tube 23 and the main feed water pipe 73, it is possible to prevent the equalizing steam from carrying water to the relatively high-temperature outlet tube sheet 22 during the subsequent equalizing process, and prevent the outlet tube sheet 22 from suffering cold shock.

[0056] In some embodiments, step S4 is specifically: introducing the equalizing steam into the heat transfer tube 23 through the main feed water pipe 73, and after exchanging heat with the heat transfer tube 23, the inlet tube sheet 21 and the outlet tube sheet 22, discharging it from the steam generator 20.

[0057] After steps S2 and S3 are completed, the main structure temperature of the steam generator 20 has been significantly reduced. At this time, steam should be quickly introduced for equalizing to reduce the temperature difference between the main feed water pipe 73, the inlet tube sheet 21, the outlet tube sheet 22, the heat transfer tube 23 and the connected metal components. The equalizing steam enters the steam generator 20 through the auxiliary steam system 72, the main feed water pipe 73 and the feed water isolation valve 74, enters the steam-water separator 75 after heat exchange, and finally is discharged into the condenser 76.

[0058] Furthermore, the flow rate of the equalizing steam is less than 1 t / h, the equalizing steam is slightly superheated steam, the superheat degree of the slightly superheated steam is 5 - 10 °C, and the duration of the equalizing process is more than 8 h. Among them, according to the number of operation modules, the parameters of the equalizing steam are different, as shown in Table 1 and Table 2. The control error of the equalizing steam flow rate ≤ 0.01 kg / s, and the pressure control error ≤ 0.05 MPa.

[0059] Through the above specific step S4, the temperature difference between the main feed water pipe 73, the inlet tube sheet 21, the outlet tube sheet 22, the heat transfer tube 23 and the connected metal components can be effectively reduced, and the temperature of the steam generator 20 can be made as balanced as possible.

[0060] In some embodiments, step S5 is specifically as follows: Start the main feed water system 71, inject water into the heat transfer tubes 23 and the connecting pipes communicating with the heat transfer tubes 23 through the main feed water pipe 73, and boost the pressure to establish a stable large-flow circulation.

[0061] Specifically, after step S4, the temperatures of the inlet tube sheet 21, the outlet tube sheet 22, the heat transfer tubes 23 and the connected metal components are already close to the steam temperature. At this time, fill the heat transfer tubes 23 of the steam generator 20 and the connected pipes with water, start the main feed water system, and the water passes through the main feed water pipe 73, the feed water isolation valve 74, the steam generator 20, the steam-water separator 75 and the condenser 76, and returns to the main feed water system 71 after cooling. Increase the pressure and flow rate to the values required in Table 1 and Table 2 until the core 10 and the steam generator 20 are cooled. The control error of the feed water flow rate is ≤2 kg / s, the control error of the pressure is ≤0.2 MPa, and the control error of the temperature is ≤2 °C.

[0062] Before water injection, the temperatures of some pipe sections of the main feed water pipe 73 are already relatively low. To prevent some pipe sections of the main feed water pipe 73 from affecting the water temperature at the inlet of the steam generator 20, warming measures should be taken for some pipe sections of the main feed water pipe 73. Before supplying water to the steam generator 20, raise the temperature of the main feed water pipe 73 to the required feed water temperature (Table 1 and Table 2), and stabilize the feed water temperature. The warming measures should be carried out in advance so as to quickly switch to step S5 after step S4 ends.

[0063] Table 1: Mean temperature steam and feed water parameters (at least 1 module is operating normally)

[0064]

[0065] Table 2: Mean temperature steam and feed water parameters (all modules are stopped)

[0066]

[0067] In some embodiments, step S6 is specifically as follows: Utilize the pressure difference between the pressure in the helium storage tank 53 and the helium pressure in the primary loop of the reactor or the helium compressor 52 to discharge the helium in the helium storage tank 53 into the primary loop of the reactor, so that the internal and external pressure difference of the heat transfer tubes 23 satisfies the relational expression (1). In this way, the heat-carrying capacity of helium can be improved, the heat transfer coefficient on the outer side of the core 10 and the heat transfer tubes 23 can be increased, and the cooling speed of the core 10 can be accelerated.

[0068] It should be noted that due to the flow rate limitation of the helium compressor 52, the process of helium filling and pressure regulation takes a relatively long time.

[0069] In some embodiments, step S7 is specifically as follows: After the helium purification system 51 and the helium compressor 52 are started, the helium compressor 52 drives the helium in the helium storage tank 53 into the primary loop of the reactor, exchanges heat with the reactor core 10 and the steam generator 20 successively, transfers the heat of the reactor core 10 to the water in the heat transfer tubes 23, and finally returns to the helium purification system 51 for cooling.

[0070] Specifically, a small-flow helium circulation is started in the primary loop of the reactor to cool the reactor core 10. After being cooled in the helium purification system 51, the helium enters the primary loop of the reactor through the upper part of the steam generator 20 under the drive of the helium compressor 52; it is heated during the flow through the reactor core 10, then flows to the steam generator 20 through the bottom structure of the reactor core 10, flows downward outside the heat transfer tubes 23 from top to bottom, transfers the heat to the subcooled water in the heat transfer tubes 23, is cooled and then descends to the bottom of the steam generator 20 and flows out of the steam generator 20, and then re-enters the helium purification system 51. At the same time, the feed water temperature and pressure of the steam generator 20 are maintained unchanged (the values are shown in step S5).

[0071] When the temperature of the hot helium gas at the reactor outlet drops to 275 °C, the whole cooling process of the reactor core 10 and the steam generator 20 ends. At this time, the reactor core 10 and the steam generator 20 already have the conditions for restart. In the initial stage of restart, the absolute value of the difference between the feed water temperature and the outlet tube sheet 22 temperature of the steam generator 20 is less than 25 °C, and the following parameters are gradually adjusted:

[0072] (1) If there are other modules running, the feed water flow rate is not less than 30 kg / s and the feed water temperature is not less than 205 °C;

[0073] (2) If there are no other modules running, the feed water flow rate is not less than 60 kg / s and the feed water temperature is not less than 160 °C;

[0074] (3) After the feed water parameters are stable, increase the helium flow rate in the primary loop of the reactor to 8 kg / s.

[0075] After operating stably according to the above parameters for fifteen minutes, the reactor power and flow rate can be gradually increased.

[0076] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0077] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor, characterized in that, It includes the following steps: S1: Discharge the helium in the primary circuit of the reactor to adjust the pressure difference between the inside and outside of the heat transfer tubes of the steam generator; S2: Cool the shell of the steam generator; S3: Drain the water in the steam generator and the main feed water pipeline; S4: Pass uniform temperature steam through the steam generator to perform uniform temperature treatment on the steam generator; S5: Inject water into the heat transfer tubes and the connecting pipelines connected to the heat transfer tubes and boost the pressure to establish a stable large-flow circulation; S6: Charge helium into the primary circuit of the reactor to increase the helium pressure and density in the primary circuit of the reactor; S7: Start the helium purification system and the helium compressor to establish a small-flow helium circulation in the primary circuit of the reactor to cool the reactor core.

2. The method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor according to claim 1, wherein Step S1 is specifically: Utilize the pressure difference between the helium pressure in the primary circuit of the reactor and the pressure in the helium storage tank or the helium compressor to discharge the helium in the primary circuit of the reactor to the helium storage tank, so that the pressure difference between the inside and outside of the heat transfer tubes satisfies the following relational expression: -8.0 ≤ P1 - P2 ≤ 2.5 (1) Where P1 is the pressure outside the heat transfer tube; P2 is the pressure inside the heat transfer tube; the unit is MPa.a.

3. The method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor according to claim 1, wherein Step S2 is specifically: Cool the shell with compressed air.

4. The method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor according to claim 3, characterized in that Step S2 is more specifically: Spray compressed air onto the outer wall surface of the shell through an air cooler, and the compressed air flows along the outer wall surface of the shell to cool the shell.

5. The method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor according to claim 1, wherein Step S3 is specifically: Drain the water in the heat transfer tubes and the main feed water pipeline to the discharge buffer tank, and then drain the water in the discharge buffer tank to the condenser or the drainage monitoring water tank through a drainage pump.

6. The method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor according to claim 1, wherein Step S4 is specifically: Pass the uniform temperature steam into the heat transfer tubes through the main feed water pipeline, exchange heat with the heat transfer tubes, the inlet tube sheet and the outlet tube sheet, and then discharge from the steam generator.

7. The method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor according to claim 6, characterized in that, The flow rate of the uniform temperature steam is less than 1 t / h, the uniform temperature steam is slightly superheated steam, the degree of superheat of the slightly superheated steam is 5 - 10 °C, and the duration of the uniform temperature treatment is more than 8 h.

8. The method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor according to claim 1, wherein Step S5 is specifically: Start the main feed water system, inject water into the heat transfer tubes and the connecting pipelines connected to the heat transfer tubes through the main feed water pipeline and boost the pressure to establish a stable large-flow circulation.

9. The method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor according to claim 2, characterized in that, Step S6 is specifically: Utilize the pressure difference between the pressure in the helium storage tank and the helium pressure in the primary circuit of the reactor or the helium compressor to discharge the helium in the helium storage tank to the primary circuit of the reactor, so that the pressure difference between the inside and outside of the heat transfer tubes satisfies the relational expression (1).

10. The method for cooling the reactor core and steam generator after an emergency shutdown of a high-temperature gas-cooled reactor according to claim 1, wherein Step S7 is specifically: After the helium purification system and the helium compressor are started, the helium compressor drives the helium in the helium storage tank into the primary circuit of the reactor, exchanges heat with the reactor core and the steam generator in sequence, transfers the heat of the reactor core to the water in the heat transfer tubes, and finally returns to the helium purification system for cooling.

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