A stepwise pressure relief device and a secondary loop heat sink system of a steam generator

Abstract

The present invention relates to a stepped pressure relief device, which includes a steam inlet pipeline, a silencing module and a heat energy recovery module. The steam inlet pipeline includes a first pipeline, a second pipeline and a third pipeline. The first pipeline is respectively communicated with the silencing module and the heat energy recovery module. The second pipeline and the third pipeline are both communicated with the heat energy recovery module and are both communicated with the atmosphere. The silencing module is respectively communicated with the heat energy recovery module and the atmosphere. The heat energy recovery module is respectively communicated with the atmosphere and each user. The present invention also provides a secondary loop heat sink system of a steam generator. By adopting the stepped pressure relief device and the secondary loop heat sink system of the steam generator of the present invention, the economy can be improved, and the economy and safety of the power plant can be enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of nuclear power plants, and particularly relates to a stepwise pressure relief device and a secondary loop heat sink system of a steam generator. Background Art

[0002] In the past nuclear engineering design process, the secondary loop heat sink system of the steam generator mainly relied on the active feed water and steam transfer and discharge systems to cope with design basis accidents. This places high requirements on the redundancy and reliability of the pumps and water sources of the active feed water system, and also poses high requirements on the measures for bypass discharge of the steam turbine, requiring it to be able to act as a reliable secondary loop heat sink for a long time to export the heat of the reactor coolant system. The comprehensive consideration of various aspects such as the grading, capacity, redundancy, and diversity of the above configurations poses great challenges in terms of personnel and equipment costs, construction and layout space, and a large amount of construction, resulting in poor economy. In addition, for the steam of the secondary loop steam transfer and discharge system of the steam generator, except for being used to drive the steam turbine during normal operation, during other start-up and shutdown conditions, a lot of steam discharged through valves is wasted, resulting in a large amount of heat energy loss. In addition, the pressure relief and discharge devices on the secondary side of the steam generator have not been considered overall, and there are still many limitations in the design of valve selection, configuration, setting values, and discharge pipelines. The use of the same discharge setting value for multiple valves results in a large spray force and enhanced vibration, and there are also problems such as excessive valve redundancy and excessive discharge capacity, which are not conducive to improving the economy and safety of the power plant. Summary of the Invention

[0003] Aiming at the defects existing in the prior art, the purpose of the present invention is to provide a stepwise pressure relief device and a secondary loop heat sink system of a steam generator to cope with the secondary loop heat sink of design basis accidents, and at the same time, adopt the design of a defense-in-depth heat sink to further improve the reliability of heat conduction in the power plant. In addition, by using the stepwise pressure relief device 10, the steam discharge is more stable and the vibration is smaller. At the same time, the heat energy of the high-temperature steam is recovered and reused, which not only improves the economy of the power plant but also improves the safety of the power plant.

[0004] To achieve the above object, the technical solution adopted by the present invention is: a step-down pressure relief device, comprising a steam inlet pipeline, a silencing module and a heat energy recovery module. The steam inlet pipeline includes a first pipeline, a second pipeline and a third pipeline. The first pipeline is respectively communicated with the silencing module and the heat energy recovery module. The second pipeline and the third pipeline are both communicated with the heat energy recovery module and are both communicated with the atmosphere. The silencing module is respectively communicated with the heat energy recovery module and the atmosphere. The heat energy recovery module is respectively communicated with the atmosphere and each user; wherein, a regulating valve group and a first isolation valve are arranged between the first pipeline and the silencing module and the heat energy recovery module. A silencing isolation valve is arranged between the silencing module and the heat energy recovery module; a safety valve and a second isolation valve are sequentially arranged between the second pipeline and the third pipeline and the heat energy recovery module. The safety valve is arranged at the inlets of the second pipeline and the third pipeline. The second isolation valve is arranged between the section where the second pipeline and the third pipeline are communicated with the atmosphere and the heat energy recovery module. Heat energy isolation valves are respectively arranged at the places where the heat energy recovery module is communicated with the atmosphere and each user.

[0005] Further, the regulating valve group includes a third isolation valve and a silencing regulating valve arranged in sequence to achieve the effect of regulating and isolating the exhaust steam.

[0006] Further, the second pipeline and the third pipeline are both divided into at least two columns, respectively discharging to the atmosphere or being communicated with the heat energy recovery module. The second isolation valve is arranged at the part where the second pipeline and the third pipeline are communicated with the heat energy recovery module.

[0007] Further, the second pipeline includes a first communication section and a first discharge section that are communicated with each other. Among them, the first communication section is communicated with the heat energy recovery module, and the first discharge section discharges to the atmosphere; the third pipeline includes a second communication section and a second discharge section that are communicated with each other. Among them, the second communication section is communicated with the heat energy recovery module, and the second discharge section discharges to the atmosphere. The second isolation valves are respectively arranged on the first communication section and the second communication section.

[0008] The present invention also provides a secondary loop heat sink system for a steam generator, comprising: a steam generator, a water supply pipeline, a heat exchange loop, a steam delivery and pressure relief pipeline, and a stepwise pressure relief device. The water supply pipeline is connected to the steam generator to supply water into the steam generator. The steam generator is connected to the stepwise pressure relief device and is connected to the steam delivery and pressure relief pipeline through the stepwise pressure relief device. The heat exchange loop includes a steam pipeline, a condensate pipeline, at least one heat exchanger, and at least one heat exchange water tank. The steam pipeline is respectively connected to the steam generator and the heat exchanger. The condensate pipeline is respectively connected to the heat exchanger and the water supply pipeline. The heat exchanger is located inside the heat exchange water tank. Wherein, a normally open steam isolation valve is provided on the steam pipeline, and at least two first condensate isolation valves in series and normally closed are provided on the condensate pipeline.

[0009] Further, at least one wide-range liquid level measuring instrument and at least one narrow-range liquid level measuring instrument are provided on the steam generator to monitor the liquid level inside the steam generator.

[0010] Further, at least one differential pressure flow measuring instrument is provided between the steam generator and the stepwise pressure relief device.

[0011] Further, the water supply pipeline includes a main feed water pipeline and a start-stop feed water pipeline. Both the main feed water pipeline and the start-stop feed water pipeline are connected to the steam generator to supply water to the steam generator 4. The condensate pipeline is respectively connected to the main feed water pipeline and the start-stop feed water pipeline, and a second condensate isolation valve and a third condensate isolation valve are respectively provided at the connection points.

[0012] Further, a feed water flow measuring device, a feed water regulating valve, a feed water isolation valve, and a feed water check valve are sequentially provided on the main feed water pipeline. At least one feed water sensor is also provided on the feed water flow monitoring device.

[0013] Further, a start-stop flow measuring device, a start-stop regulating valve, a start-stop isolation valve, and a start-stop check valve are sequentially provided on the start-stop feed water pipeline. At least one start-stop sensor is also provided on the start-stop flow measuring device.

[0014] The effects of the present invention are as follows: Through comprehensive considerations in aspects such as grading, capacity, redundancy, and diversity configured in the secondary loop heat sink system of the steam generator, the personnel and equipment costs are reduced, the construction and layout space is saved, and the economy is increased. At the same time, by using the stepwise pressure relief device, the heat energy of the steam discharged through the valve during other start-stop conditions except for driving the steam turbine during normal operation is recovered. And the economy and safety of the power plant are improved through the design of valve selection, configuration, setting value, and discharge pipeline, etc. Description of the Drawings

[0015] Figure 1 It is a schematic diagram of a module of a step - down pressure - relief device in the present invention;

[0016] Figure 2 It is a schematic diagram of a module of a secondary - loop heat sink system of a steam generator in the present invention.

[0017] Explanation of reference numerals:

[0018] 10. Step - down pressure - relief device; 1. Steam inlet pipeline; 2. Silencing module; 3. Heat - energy recovery module; 11. First pipeline; 12. Second pipeline; 13. Third pipeline; 111. Control valve; 112. First isolation valve; 21. Silencing isolation valve; 14. Safety valve; 113. Second isolation valve; 114. Silencing control valve; 115. Second isolation valve; 121. First communication section; 122. First discharge section; 131. Second communication section; 132. Second discharge section;

[0019] 4. Steam generator; 40. Water supply pipeline; 50. Heat - exchange loop; 60. Steam transmission and pressure - relief pipeline; 51. Steam pipeline; 52. Condensate pipeline; 53. Heat exchanger; 54. Heat - exchange water tank; 511. Steam isolation valve; 521. First condensate isolation valve; 401. Wide - range liquid - level measuring instrument; 402. Narrow - range liquid - level measuring instrument; 403. Differential - pressure flow - measuring instrument; 41. Main feed - water pipeline; 42. Start - stop feed - water pipeline; 522. Second condensate isolation valve; 523. Third condensate isolation valve; 411. Feed - water flow - measuring device; 412. Feed - water control valve; 413. Feed - water isolation valve; 414. Feed - water check valve; 415. Feed - water sensor; 421. Start - stop flow - measuring device; 422. Start - stop control valve; 423. Start - stop isolation valve; 424. Stop check valve; 425. Start - stop sensor. Detailed implementation manners

[0020] The present invention will be further described below in conjunction with the drawings and detailed implementation manners.

[0021] As Figure 1-2 shown, a step - down pressure - relief device 10 provided by the present invention is arranged on the steam transmission and pressure - relief pipeline of the secondary - loop heat sink of a steam generator, and includes a steam inlet pipeline 1, a silencing module 2 and a heat - energy recovery module 3 that are connected to the exhaust pipe on the steam transmission and pressure - relief pipeline. The steam inlet pipeline 1 includes a first pipeline 11, a second pipeline 12 and a third pipeline 13. The first pipeline 11 is respectively connected to the silencing module 2 and the heat - energy recovery module 3. The second pipeline 12 and the third pipeline 13 are both connected to the heat - energy recovery module 3 and are both connected to the atmosphere. The silencing module 2 is respectively connected to the heat - energy recovery module 3 and the atmosphere. The heat - energy recovery module 3 is respectively connected to the atmosphere and each user.

[0022] Among them, regulating valve groups 111 and first isolation valves 112 are respectively arranged between the first pipeline 11, the silencing module 2 and the heat energy recovery module 3, and a silencing isolation valve 21 is arranged between the silencing module 2 and the heat energy recovery module 3. Safety valves 14 and second isolation valves 113 are successively arranged between the second pipeline 12 and the third pipeline 13 and the heat energy recovery module 3. The safety valve 14 is arranged at the inlets of the second pipeline 12 and the third pipeline 13, and the second isolation valve 113 is arranged between the sections of the second pipeline 12 and the third pipeline 13 communicating with the atmosphere and the heat energy recovery module 3. Heat energy isolation valves 31 are respectively arranged at the connections of the heat energy recovery module 3 with the atmosphere and each user.

[0023] It can be understood that after the steam in the steam transportation and pressure relief pipelines enters from the steam inlet pipeline 1, it enters the silencing module 2 through the first pipeline 11 via the regulating valve group 111, and is discharged to the atmosphere through the silencing module 2 for pressure relief. When the silencing isolation valve 21 is opened, the steam can also enter the heat energy recovery module 3, and the waste heat of the steam is recovered by the heat energy recovery module 3.

[0024] It can be understood that the two safety valves 14 on the second pipeline 12 and the third pipeline 13 are respectively designed according to different discharge pressure settings, and are both equipped with nuclear-grade seismic power supply. When the pressure of the steam reaches the discharge pressure setting, the steam enters the second pipeline 12 and / or the third pipeline 13 and is discharged into the atmosphere to achieve the effect of staged pressure relief. When the second isolation valve 113 is opened, the steam can also enter the heat energy recovery module 3, and the waste heat of the steam is recovered by the heat energy recovery module 3.

[0025] Furthermore, the regulating valve group 111 includes a second isolation valve 115 and a silencing regulating valve 114 arranged in sequence to achieve the effects of regulating and isolating the exhaust steam.

[0026] It can be understood that the third isolation valve 115 can be an electric isolation valve, a pneumatic isolation valve, a pilot quick-opening valve, etc.

[0027] Furthermore, the second pipeline 12 and the third pipeline 13 are each divided into at least two columns, and are respectively discharged to the atmosphere or communicated with the heat energy recovery module 3. The second isolation valve 113 is arranged at the part where the second pipeline 12 and the third pipeline 13 are communicated with the heat energy recovery module 3.

[0028] Furthermore, the second pipeline 12 includes a first connection section 121 and a first discharge section 122 that are connected to each other. Among them, the first connection section 121 is communicated with the heat energy recovery module 3, and the first discharge section 122 is discharged to the atmosphere.

[0029] The third pipeline 13 includes a second communication section 131 and a second discharge section 132 that communicate with each other. Among them, the second communication section 131 communicates with the heat recovery module 3, the second discharge section 132 discharges to the atmosphere, and the second isolation valve 113 is respectively arranged on the first communication section 121 and the second communication section 131.

[0030] The present invention also provides a steam generator secondary loop heat sink system, which includes a steam generator 4, a water supply pipeline 40, a heat exchange loop 50, a steam transmission and pressure relief pipeline 60, and a stepwise pressure relief device 10. The water supply pipeline 40 communicates with the steam generator 4 to supply water to the steam generator 4. The steam generator 4 communicates with the stepwise pressure relief device 10 and communicates with the steam transmission and pressure relief pipeline 60 through the stepwise pressure relief device. The heat exchange loop 50 includes a steam pipeline 51, a condensate pipeline 52, at least one heat exchanger 53, and at least one heat exchange water tank 54. The steam pipeline 51 communicates with the steam generator 4 and the heat exchanger 53 respectively, the condensate pipeline 52 communicates with the heat exchanger and the water supply pipeline 40 respectively, and the heat exchanger 53 is located in the heat exchange water tank 54.

[0031] Among them, an always-open steam isolation valve 511 is arranged on the steam pipeline 51, and at least two series-connected and normally-closed first condensate isolation valves 521 are arranged on the condensate pipeline 52.

[0032] It can be understood that in this embodiment, the steam generated by the steam generator 4 is discharged to the steam turbine to supply steam to the steam turbine after being depressurized and heat recovered by the stepwise pressure relief device.

[0033] Furthermore, at least one wide-range liquid level measuring instrument 401 and at least one narrow-range liquid level measuring instrument 402 are arranged on the steam generator 4 to monitor the liquid level in the steam generator 4.

[0034] Furthermore, at least one differential pressure flow measuring instrument 403 is arranged between the steam generator 4 and the stepwise pressure relief device.

[0035] It can be understood that the flow signal measured by the differential pressure flow measuring instrument 403 can be sent to the power plant reactor protection system to trigger a safety protection signal.

[0036] Furthermore, the water supply pipeline 40 includes a main feed water pipeline 41 and a start-stop feed water pipeline 42. Both the main feed water pipeline 41 and the start-stop feed water pipeline 42 communicate with the steam generator 4 to supply water to the steam generator 4.

[0037] Furthermore, the condensate pipeline 52 communicates with the main feed water pipeline 41 and the start-stop feed water pipeline 42 respectively, and a second condensate isolation valve 522 and a third condensate isolation valve 523 are respectively arranged at the connection points.

[0038] Furthermore, a water flow measuring device 411 , a water supply regulating valve 412 , a water supply isolation valve 413 and a water supply check valve 414 are sequentially arranged on the main water supply pipeline 41 , and at least one water supply sensor 415 is also arranged on the water flow monitoring device 411 .

[0039] Furthermore, a start-stop flow measuring device 421 , a start-stop regulating valve 422 , a start-stop isolation valve 423 and a start-stop return valve 424 are sequentially arranged on the start-stop water supply pipeline 42 , and at least one start-stop sensor 425 is also arranged on the start-stop flow measuring device 421 .

[0040] It can be understood that the feedwater flow measurement device 411 is located in the earthquake-resistant plant and is designed as a nuclear-grade earthquake-resistant device. The flow signal measured by the feedwater sensor 415 can be sent to the power plant reactor protection system to trigger the safety protection signal. The feedwater regulating valve 412 is a pneumatic valve and is designed to be closed in case of air failure. It can realize both the regulation function and the rapid isolation function. The feedwater isolation valve 413 can be an electric isolation valve or a gas-liquid linkage fast-closing isolation valve. The feedwater regulating valve 412 and the feedwater isolation valve 413 both receive the feedwater isolation signal. According to the hydraulic transient results caused by the actual closure, staged isolation can be adopted. The feedwater isolation valve 413 and the feedwater regulating valve 412 both receive the feedwater isolation signal. According to the hydraulic transient results caused by the actual closure, staged isolation can be adopted. The feedwater isolation valve 413 is arranged as close to the containment penetration as possible, and the feedwater check valve 414 is arranged as close to the steam generator 4 as possible, and is located upstream of the heat exchange circuit pipe 50.

[0041] It can be understood that the start-stop flow measurement device 421 is located in the earthquake-resistant plant and is designed as a nuclear-grade earthquake-resistant device. The flow signal measured by the start-stop sensor 425 can be sent to the power plant reactor protection system to trigger the safety protection signal. The start-stop regulating valve 422 is a pneumatic valve and is designed to be closed when air is lost. It can realize both the regulation function and the rapid isolation function. The start-stop isolation valve 423 can use either an electric isolation valve or a gas-liquid linkage fast-closing isolation valve. The start-stop regulating valve 422 and the start-stop isolation valve 423 both receive the water supply isolation signal. According to the hydraulic transient results caused by the actual closure, staged isolation can be adopted. The start-stop isolation valve 423 and the start-stop regulating valve 422 both receive the water supply isolation signal. According to the hydraulic transient results caused by the actual closure, staged isolation can be adopted. The start-stop isolation valve 423 is arranged as close to the containment penetration as possible, and the start-stop return valve 424 is arranged as close to the steam generator 4 as possible, and is located upstream of the heat exchange circuit pipe 50.

[0042] In this embodiment, under the normal operating conditions of the nuclear power plant, water is supplied to the steam generator 4 through the main feed water supply pipeline 41. After heat exchange on the secondary side of the steam generator 4, it enters the direction of the steam turbine through the steam transmission and pressure relief pipeline 60, serving as the secondary side heat sink during the normal operation of the power plant. Under the start-up and shutdown operating conditions of the nuclear power plant, water is supplied to the steam generator 4 through the start-up and shutdown feed water pipeline. After heat exchange on the secondary side of the steam generator 4, when the normal steam cannot be discharged to the condenser, the steam is discharged through the stepped pressure relief device 10, serving as the secondary side heat sink during the start-up and shutdown operation of the power plant. The regulating valve on the water supply pipeline 40 is used to adjust the flow rate of water supplied to the steam generator 4.

[0043] When the steam is discharged through the stepped pressure relief device 10, the stepped pressure relief device 10 is mainly used during the start-up and shutdown of the power plant or during some long-term hot standby stages, and when the steam is non-radioactive. When the steam passes through the regulating valve group 111, it first enters the silencing module 2 for noise reduction treatment, and then the steam is discharged into the heat energy recovery module 3. It can also directly discharge the steam into the heat energy recovery module 3 without reducing the noise according to the needs of the heat exchange users. Multiple high-pressure energy storage modules can be set in the heat energy recovery module 3. Finally, according to the needs of the users, heat distribution is carried out by switching and adjusting the isolation valves and regulating valves on the pipelines leading to each user, and the steam is transported to each user. Each user can further cool down and reduce the pressure of the received steam for use as needed.

[0044] The opening setting value of the safety valve 14 in the stepped pressure relief device 10 is higher than the discharge setting value of the regulating valve group 111, and the opening setting values of the safety valves 14 are different and increase gradually. In different transient situations, the safety valves 14 will open gradually according to the system pressure change, and the highest opening pressure setting value should ensure that the secondary side does not exceed the pressure limit under different accident conditions. At the same time, the discharge pipelines of the safety valves 14 are arranged symmetrically in two columns, which can balance the reaction force at the valve outlet, reduce the load on the main steam pipeline, minimize the vibration when the valve opens, and optimize the operation of different numbers of valves for different accidents. This makes the steam discharge more reliable, more stable, and with less vibration.

[0045] The discharge capacity of the safety valve 14 in the stepped pressure relief device 10 is relatively large. In addition to discharging heat as a heat sink, it is mainly used for overpressure protection. The steam generally discharges directly to the atmosphere through the safety valve 14. On the premise of not affecting the completion of the above functions, the discharge of the safety valve 14 can also be discharged into the heat energy recovery module 3, and the discharges of different safety valves 14 are arranged at different heights, and the discharge diameters can also gradually increase or decrease the discharge back pressure. Such a setting can avoid the impact force and local pressure surge caused by the discharge concentration in the same area.

[0046] In the case of a design basis accident at a nuclear power plant, first, the loss of off-site power and other situations lead to the loss of main feed water supply, and the main feed water pipeline 41 is isolated. Then, the start-stop feed water pipeline 42 is used to supply water to the steam generator 4. After heat exchange on the secondary side of the steam generator 4, when the normal steam discharge to the condenser is unavailable, the steam is discharged through the stepwise pressure relief device 10, serving as the secondary side heat sink for in-depth defense during the shutdown of the power plant due to the accident. This avoids the operation of the passive heat exchange system and further improves the safety and reliability of the power plant. Among them, when the steam is discharged through the stepwise pressure relief device 10, according to the actual situation analysis of the accident, if the steam is non-radioactive and can remain in the recovery period for a long time, heat recovery and utilization can be considered; otherwise, it is directly discharged.

[0047] In the case of a design basis accident at a nuclear power plant, first, the loss of off-site power and other situations lead to the loss of main feed water supply, and the main feed water pipeline 41 is isolated. Then, the start-stop feed water pipeline 42 is used to supply water to the steam generator 4. If the start-stop feed water supply is lost, the start-stop feed water pipeline 42 is isolated. The low-flow feed water signal on the start-stop feed water pipeline 42 is sent to the reactor protection system to be used for combining and triggering the valves that need to be closed and opened for the operation of the passive heat exchange loop. A closing signal needs to be sent to the regulating valve and isolation valve on the main feed water pipeline 41, a closing signal needs to be sent to the feed water regulating valve 412 and feed water isolation valve 413 on the start-stop feed water pipeline 42, and a closing signal needs to be sent to the main steam isolation valve. An opening signal needs to be sent to the two normally closed first condensate isolation valves 521 connected in series on the condensate pipeline 52 in the heat exchange loop 50 and the normally open third condensate isolation valve 523 on the condensate pipeline 52 leading to the start-stop feed water pipeline 42. These valves and signals are all powered by nuclear-grade reliable batteries. Even if a single failure occurs in the above-mentioned normally closed electric valves or closed pneumatic valves, the other valve can still isolate the boundary of the passive heat exchange loop operation. After the heat exchange loop 50 is put into operation, the steam in the secondary circuit enters the heat exchanger 54 through the steam pipeline 51, then transfers heat to the heat exchange water tank 55, the steam is condensed into water, and then through the condensate pipeline 52, the condensed water is supplied to the steam generator 4 through the start-stop water supply pipeline 42. If a failure occurs in the start-stop water supply pipeline 42 loop, this pipeline can be isolated, and then by opening the second condensate isolation valve 522 on the condensate pipeline 52 connecting to the main feed water pipeline 41, the water supply to the steam generator 4 can continue, forming a passive closed natural circulation. The heat exchange loop 50 serves as the secondary side heat sink of the steam generator under the design basis accident, ensuring the safe operation of the nuclear power plant in case of an accident.

[0048] In the case of a transient or accident in a nuclear power plant, the opening setting value of the regulating valve group 111 in the stepwise pressure relief device 10 is relatively low. In addition to regulating the steam discharge capacity and stabilizing the pressure of the primary and secondary circuits, it is also used to achieve the function of heat removal in the defense-in-depth and avoid the operation of the passive heat exchange circuit. Moreover, it is also used to achieve the function of overpressure protection in the defense-in-depth and avoid the operation of the safety valve 14.

[0049] During a nuclear power plant accident, such as in the case of SGTR, when radioactivity is detected and signals such as a high water level in the steam generator 4 are present, the feed water isolation valve 413 and the start-stop isolation valve 423 of the accident steam generator 4 are closed to isolate the steam generator 4. At this pressure, the safety valve 14 and the discharge valve in the stepwise pressure relief device 10 can be in a closed state, realizing the automatic isolation of the damaged steam generator 4 and avoiding the release of radioactivity to the outside. This ensures the safety of personnel, the power plant, and the environment.

[0050] The stepwise pressure relief device 10 of this system optimizes the number of valves opened in transient and accident situations, avoids the vibration caused by the simultaneous opening of valves for discharge or pressure relief, and can recover the heat of some high-temperature and high-pressure steam. At the same time, the recovered heat energy of the high-temperature steam is reused, which not only improves the economy of the power plant but also enhances the safety of the power plant.

[0051] It can be seen from the above embodiments that the advantages of the present invention are as follows:

[0052] (1) A passive heat exchange circuit 450 that forms a natural circulation by using the density difference and gravity is adopted, which is safer and more reliable, as the secondary circuit heat sink for coping with design basis accidents. At the same time, when the main feed water pipeline 41 is lost, the start-stop feed water pipeline 42 is used in cooperation with the steam transmission and stepwise pressure relief device 10 for heat conduction as the defense-in-depth heat sink of the steam generator secondary circuit, avoiding the operation of the passive heat exchange circuit 50, further improving the safety and reliability of the power plant. It avoids the cumbersome and complex design brought about by using active systems to cope with design basis accidents in the past, and avoids the economic improvement caused by comprehensive considerations in various aspects such as equipment classification, capacity, redundancy, and diversity in the above design, including personnel and equipment costs, construction and layout space, and a large amount of construction. This set of secondary circuit heat sink system as a whole improves the economy and safety of the power plant.

[0053] (2) A step - down pressure relief device 10 is adopted. This device includes at least one valve adjustment group 111 that can adjust and isolate the exhaust pressure relief, and at least two safety valves 14 that can directly discharge. The number of valves should be optimized and determined according to the discharge capacity of the valves and accident analysis. The above - mentioned discharge valves are all designed according to different opening pressure set values. The highest opening pressure set value of the step - down pressure relief device 10 should ensure that the secondary side does not exceed the pressure limit under different accident conditions. At the same time, the discharge pipelines of the safety valves 14 are arranged symmetrically in two rows, which can balance the reaction force at the valve outlet, reduce the load on the main steam pipeline, minimize the vibration when the valves open, and optimize the operation of different numbers of valves for different accidents. This makes the steam discharge more reliable, more stable, and with less vibration.

[0054] (3) A step - down pressure relief device 10 is adopted. This device includes at least one silencing module and at least one heat energy recovery module. Among them, the silencer module 2 can be set with multiple - stage silencers according to the power plant's requirements, and modules with different silencing capabilities can be set. This flexible setting can consider different degrees of silencing treatment according to the on - site requirements of users, optimize the equipment as much as possible according to user needs, and is conducive to improving the economy of the power plant. Among them, the heat energy recovery module 3 includes at least one heat storage module. The discharge pipelines discharged into this module comprehensively consider setting their discharge heights at different elevations and setting different discharge pipe diameters. The final dimensions determined through simulation calculations not only meet the discharge requirements and heat recovery requirements but also avoid the problems of excessive impact force and too - fast pressure increase when concentrated discharge occurs at the same position. The recovered heat can be adjusted in flow rate and depressurized through the regulating valve group 111 according to user needs. When necessary, user isolation can be carried out through isolation valves, and a cooling device can also be set within the user range. Through the above configuration, after coming out of the heat energy recovery module 3, it can meet different user needs, including conventional high - temperature and high - pressure steam sterilization in the power plant and cleaning of oil - containing pipelines, as well as thermal deaeration for the second - loop deaerator in the power plant, etc. It can reduce the use time of the electric boiler during the unavailable period of the second loop, save energy, and so on.

[0055] (4) A step - down pressure relief device 10 is adopted. Among them, the third isolation valve 115 and the silencing regulating valve 114 in the regulating valve group 111 that can adjust and isolate the exhaust pressure relief can be combined with various valve types according to the actual situation of the power plant. The safety valve 14 can be a spring - type or pilot - type according to the actual situation of the power plant. The step - by - step discharge of these valves can ensure the integrity of the equipment related to the safety - related functions of isolating the shell side of the steam generator 4, the connected pipelines, and the containment isolation and steam generator 4 isolation under various operating conditions of the power plant. The regulating valve group 111 that can adjust and isolate the exhaust pressure relief can be used not only for heat regulation and derivation but also for controlling the stability of the primary and secondary circuits of the nuclear power plant. It can simultaneously serve as a deep - defense measure for over - pressure protection and decay heat derivation of the second loop, further enhancing the reliability of the power plant.

[0056] (5) The regulating valve of the water supply pipeline 40 has both the functions of regulating and isolating the feed water. Therefore, the regulating valve and the isolation valve are equivalent to two nuclear-grade reliable feed water isolation valves being provided. In the case of a SGTR accident, it prevents the steam generator from overflowing and the main steam pipeline from being flooded with water. It avoids the release of radioactive substances caused by the valves in the stepwise depressurization device 10 discharging the feed water and the reactor coolant to the atmosphere. At the same time, it serves as a reliable boundary isolation valve for the operation of the passive heat exchange loop. The main steam isolation valve on the steam pipeline can be realized by a pneumatic-hydraulic linkage isolation valve with two control loops to achieve reliable steam isolation, and at the same time, it serves as a reliable boundary isolation valve for the operation of the passive heat exchange loop. At the same time, the reliable safety valve is adopted in the stepwise depressurization device 10 on the steam pipeline. When overpressure protection is not required, it can be switched to the closed state and maintained closed to maintain a closed isolation state. The valve group in the stepwise depressurization device 10 that can regulate and isolate the exhaust steam and depressurize adopts the design of an isolation valve plus a regulating valve, which is equivalent to having two isolation measures and maintaining a sealed-edge isolation valve device. The above-mentioned valves in the stepwise depressurization device 10 can serve as reliable boundary isolation valves for the operation of the passive heat exchange loop.

[0057] The device described in the present invention is not limited to the embodiments described in the specific implementation manners. Those skilled in the art can obtain other implementation manners based on the technical solution of the present invention, which also belong to the scope of the technical innovation of the present invention.

Claims

1. A hierarchical pressure relief device is arranged on the steam transmission and pressure relief pipeline. It is characterized in that it includes: a steam inlet pipeline (1), a silencing module (2) and a heat energy recovery module (3). The steam inlet pipeline (1) includes a first pipeline (11), a second pipeline (12) and a third pipeline (13). The first pipeline (11) is respectively communicated with the silencing module (2) and the heat energy recovery module (3). The second pipeline (12) and the third pipeline (13) are both communicated with the heat energy recovery module (3) and are both communicated with the atmosphere. The silencing module (2) is respectively communicated with the heat energy recovery module (3) and the atmosphere. The heat energy recovery module (3) is respectively communicated with the atmosphere and each user; Wherein, a regulating valve group (111) and a first isolation valve (112) are respectively arranged between the first pipeline (11) and the silencing module (2) and the heat energy recovery module (3). A silencing isolation valve (21) is arranged between the silencing module (2) and the heat energy recovery module (3). A safety valve (14) and a second isolation valve (113) are sequentially arranged between the second pipeline (12) and the third pipeline (13) and the heat energy recovery module (3). The safety valve (14) is arranged at the inlets of the second pipeline (12) and the third pipeline (13). The second isolation valve (113) is arranged between the section where the second pipeline (12) and the third pipeline (13) are communicated with the atmosphere and the heat energy recovery module (3). Heat energy isolation valves (31) are respectively arranged at the places where the heat energy recovery module (3) is communicated with the atmosphere and each user; The heat energy recovery module (3) is used for heat distribution to deliver steam to each user.

2. A hierarchical pressure relief device according to claim 1, it is characterized in that: The regulating valve group (111) includes a third isolation valve (115) and a silencing regulating valve (114) arranged in sequence to achieve the effect of regulating and isolating the exhaust steam.

3. A hierarchical pressure relief device according to claim 2, it is characterized in that: Both the second pipeline (12) and the third pipeline (13) are divided into at least two columns, respectively discharging to the atmosphere or being communicated with the heat energy recovery module (3). The second isolation valve (113) is arranged at the part where the second pipeline (12) and the third pipeline (13) are communicated with the heat energy recovery module (3).

4. A hierarchical pressure relief device according to claim 3, it is characterized in that: The second pipeline (12) includes a first communication section (121) and a first discharge section (122) which are communicated with each other. Wherein, the first communication section (121) is communicated with the heat energy recovery module (3), and the first discharge section (122) discharges to the atmosphere; The third pipeline (13) includes a second communication section (131) and a second discharge section (132) that communicate with each other. Among them, the second communication section (131) communicates with the heat recovery module (3), the second discharge section (132) discharges to the atmosphere, and the second isolation valve (113) is respectively arranged on the first communication section (121) and the second communication section (131).

5. A secondary loop heat sink system for a steam generator Characterized in that It includes A steam generator (4), a water supply pipeline (40), a heat exchange loop (50), a steam transmission and pressure relief pipeline (60), and a stepwise pressure relief device (10) as described in any one of claims 1-4. The water supply pipeline (40) communicates with the steam generator (4) to supply water into the steam generator (4). The steam generator (4) communicates with the stepwise pressure relief device (10) and is connected to the steam transmission and pressure relief pipeline (60) through the stepwise pressure relief device (10). The heat exchange loop (50) includes a steam pipeline (51), a condensate pipeline (52), at least one heat exchanger (53), and at least one heat exchange water tank (54). The steam pipeline (51) communicates with the steam generator (4) and the heat exchanger (53) respectively. The condensate pipeline (52) communicates with the heat exchanger (53) and the water supply pipeline (40) respectively. The heat exchanger (53) is located inside the heat exchange water tank (54). Among them, a normally open steam isolation valve (511) is arranged on the steam pipeline (51), and at least two series-connected normally closed first condensate isolation valves (521) are arranged on the condensate pipeline (52).

6. A secondary loop heat sink system for a steam generator as described in claim 5 Characterized in that At least one wide-range liquid level measuring instrument (401) and at least one narrow-range liquid level measuring instrument (402) are arranged on the steam generator (4) to monitor the liquid level inside the steam generator.

7. A secondary loop heat sink system for a steam generator as described in claim 5 Characterized in that At least one differential pressure flow measuring instrument (403) is arranged between the steam generator (4) and the stepwise pressure relief device (10).

8. A secondary loop heat sink system for a steam generator as described in claim 7 Characterized in that The water supply pipeline (40) includes a main water supply pipeline (41) and a start-stop water supply pipeline (42). The main water supply pipeline (41) and the start-stop water supply pipeline (42) are both connected to the steam generator (4) to supply water to the steam generator (4). The condensate pipeline (52) is respectively connected to the main water supply pipeline (41) and the start-stop water supply pipeline (42), and second condensate isolation valves (522) and third condensate isolation valves (523) are respectively arranged at the connection points.

9. A secondary loop heat sink system for a steam generator as described in claim 8 Characterized in that A water supply flow measurement device (411), a water supply regulating valve (412), a water supply isolation valve (413) and a water supply check valve (414) are successively arranged on the main water supply pipeline (41), and at least one water supply sensor (415) is further arranged on the water supply flow measurement device (411).

10. A secondary loop heat sink system of a steam generator according to claim 8 characterized in that ; A start-stop water supply flow measurement device (421), a start-stop regulating valve (422), a start-stop isolation valve (423) and a start-stop check valve (424) are successively arranged on the start-stop water supply pipeline (42), and at least one start-stop sensor (425) is further arranged on the start-stop water supply flow measurement device (421).

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