A pool reactor safety management system and method

Abstract

A pool reactor safety management system comprises a shutdown device, a passive residual heat removal device, a main circulation device, an auxiliary circulation device and a passive circulation device, wherein the shutdown device is used to realize shutdown under accident conditions; the passive residual heat removal device forms natural circulation between a reactor pool and an external heat sink; the main circulation device provides a circulation pipeline and drives the circulation of cooling water under normal conditions; the auxiliary circulation device comprises an auxiliary circulation pump connected in parallel with the main circulation pump; and the passive circulation device comprises a natural circulation valve arranged in a lower chamber of the reactor. The system can effectively avoid overheating of the cooling water under accident conditions, quickly switch the flow direction of the cooling water from forced convection under normal conditions to natural convection under accident conditions, prevent flow stagnation, and effectively improve the safety and reliability of the pool reactor. The application also provides a pool reactor safety management method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of nuclear power, and particularly relates to a pool reactor safety management system and method. BACKGROUND

[0002] The pool reactor is a small reactor with a reactor placed in a large pool, and has the advantages of simple structure and flexible use, and is widely used in the fields of physics and engineering test, and has a good prospect in the field of nuclear energy heating application. Due to the difference in structure and volume, the special safety system of the pool reactor is different from that of the conventional pressurized water reactor, mainly relying on the external power support of the active system, and the pool reactor is usually used for scientific research or test purpose, and the human resources and external support are limited compared with the conventional nuclear power plant, and the safety margin of the special safety system of the existing pool reactor still has room for optimization and improvement. Therefore, it is of positive significance to provide a safety management system for the structural characteristics of the pool reactor, which can effectively improve the safety and reliability of the pool reactor. SUMMARY

[0003] The present application aims to provide a pool reactor safety management system to improve the safety of the pool reactor. The present application also provides a pool reactor safety management method.

[0004] According to an embodiment of one aspect of the present application, a pool reactor safety management system is provided, which comprises: a shutdown device, a passive residual heat removal device, a main circulation device, an auxiliary circulation device and a passive circulation device. The shutdown device is used to intervene in the reactor core under accident conditions to achieve shutdown. The passive residual heat removal device comprises a pool heat exchanger, an external heat exchanger and an external heat sink. The pool heat exchanger is arranged in the reactor pool, the external heat exchanger is arranged in the external heat sink, the pool heat exchanger and the external heat exchanger are connected to form a circulation loop, and natural circulation is formed when the temperature of the pool heat exchanger is higher than that of the external heat exchanger. The main circulation device comprises a main circulation pump and a circulation pipeline. The main circulation pump drives the circulation of cooling water under normal conditions. The two ends of the circulation pipeline are connected to the reactor lower chamber, respectively, and a siphon breaking hole is arranged at a position upstream of the reactor lower chamber and higher than the reactor core. An isolation device is arranged upstream of the reactor lower chamber in the circulation pipeline. When the isolation device is closed, the cooling water in the circulation pipeline flows into the reactor pool through the isolation device. When the isolation device is opened, at least part of the cooling water in the circulation pipeline flows into the reactor lower chamber through the isolation device. The auxiliary circulation device comprises an auxiliary circulation pump, which is connected in parallel with the main circulation pump. The passive circulation device comprises a natural circulation valve arranged in the reactor lower chamber.

[0005] The system can combine the active safety management device and the passive safety management device under the accident condition, realize the shutdown and the core cooling, switch the cooling water flow direction in the pool from top to bottom under the normal condition to bottom to top under the accident condition, avoid the cooling water flow stagnation when the main circulating pump stops, and improve the safety of the reactor.

[0006] Further, in some embodiments, the shutdown device comprises a control rod assembly and / or a heavy water tank, the control rod assembly comprises neutron absorber control rods, and the control rod assembly is capable of inserting the neutron absorber control rods into the core; the heavy water tank stores heavy water, and the heavy water tank is capable of injecting the heavy water into the core in a passive manner.

[0007] Further, in some embodiments, the external heat sink is further provided with an external heat sink cooling device for reducing the temperature of the external heat sink.

[0008] Further, in some embodiments, the isolation device comprises a main system inlet pipe ejector and an ejector isolation valve; the main system inlet pipe ejector comprises a nozzle, a suction chamber, a throat, and a diffuser pipe. The nozzle is connected to the upstream circulating pipeline; the suction chamber is in the shape of a flared bell mouth at one end towards the nozzle and is connected to the reactor pool, and the other end is connected to the throat; one end of the diffuser pipe is connected to the throat, and the other end is gradually expanded in diameter and connected to the ejector isolation valve. The main system inlet pipe ejector is connected to the reactor lower chamber through the ejector isolation valve, when the ejector isolation valve is closed, the cooling water in the circulating pipeline flows back into the reactor pool through the main system inlet pipe ejector; when the ejector isolation valve is opened, at least part of the cooling water in the circulating pipeline and part of the cooling water in the reactor pool flow into the reactor lower chamber through the main system inlet pipe ejector.

[0009] The main system inlet pipe ejector can introduce the cooling water in the reactor pool into the reactor lower chamber, thereby improving the circulation efficiency of the cooling water.

[0010] Further, in some embodiments, the flow ratio of the main system inlet pipe ejector is 1.05-1.2.

[0011] Further, in some embodiments, the circulating pipeline is further provided with a main system outlet pipe ejector downstream of the reactor lower chamber, the main system outlet pipe ejector comprises a nozzle, a suction chamber, a throat, and a diffuser pipe; the nozzle is connected to the upstream circulating pipeline; the suction chamber is in the shape of a flared bell mouth at one end towards the nozzle and is connected to the reactor pool, and the other end is connected to the throat; one end of the diffuser pipe is connected to the throat, and the other end is gradually expanded in diameter and connected to the circulating pipeline.

[0012] Further, in some embodiments, the system further comprises a spray system comprising a passive water storage tank capable of spraying cooling water to the reactor building in accident conditions.

[0013] Further, in some embodiments, the system further comprises a filtered exhaust system for filtering radioactive contaminants and exhausting gas in the reactor building.

[0014] Further, in some embodiments, the pool-type reactor is configured with a high-temperature and high-pressure irradiation pipeline, and the pool-type reactor safety management system comprises a pressure-containing compartment, the high-temperature and high-pressure irradiation pipeline is enclosed in the pressure-containing compartment, and the wall of the pressure-containing compartment is provided with a heat-conducting plate to conduct heat out of the pressure-containing compartment; the pressure-containing compartment further comprises a pressure-suppression pipe, one end of the pressure-suppression pipe is communicated with the pressure-containing compartment and the other end is immersed in the cooling water of the reactor pool, and the pressure-suppression pipe is provided with a check valve and a bubbler.

[0015] Further, in some embodiments, the pressure-containing compartment is further provided with a burst disc, and when the burst disc is detonated, the pressure-containing compartment is depressurized.

[0016] According to an embodiment of another aspect of the present application, a pool-type reactor safety management method is provided, which uses the pool-type reactor safety management system provided in any of the foregoing embodiments, and comprises the following steps:

[0017] Step a): starting the shutdown device to achieve shutdown;

[0018] Step b): using the auxiliary circulating pump to force the cooling water to circulate to the reactor core when the decay heat is reduced to below a first threshold of the rated power;

[0019] Step c): opening the isolation device to shut down the downstream pipeline of the reactor lower chamber, and enabling the auxiliary circulating pump to drive the cooling water to flow into the reactor lower chamber through the isolation device and flow out of the reactor upper chamber, so as to reverse the flow direction of the cooling water in the reactor core;

[0020] Step d): after the flow direction of the cooling water in the reactor core is reversed, the auxiliary circulating pump is closed, and natural circulation is performed;

[0021] Step e): when the decay heat of the reactor core is reduced to below a second threshold of the rated power, the natural circulation valve is opened.

[0022] Further, in some embodiments, the first threshold is 2% of the rated power of the reactor core; and the second threshold is 1% of the rated power of the reactor core. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Structure diagram of a pool type reactor safety management system for one embodiment;

[0024] Figure 2 Structure diagram of a pool type reactor safety management system for another embodiment;

[0025] Figure 3 Structure diagram of an ejector for one embodiment.

[0026] Meaning of reference numerals: 10 - reactor core; 11 - reactor lower plenum; 111 - main system outlet pipe; 112 - main system inlet pipe; 12 - delay tank; 13 - main circulation pump; 14 - auxiliary circulation pump; 15 - main circulation pump isolation valve; 16 - auxiliary circulation pump isolation valve; 17 - main circulation pump post check valve; 18 - auxiliary circulation pump post check valve; 19 - main heat exchanger; 20 - irradiation loop pressurized vessel; 21 - irradiation loop pressurizer; 22 - irradiation loop main heat exchanger; 23 - irradiation loop circulation pump; 24 - irradiation loop hot leg section; 241 - irradiation loop hot leg section injection isolation valve; 25 - irradiation loop transition section; 26 - irradiation loop cold leg section; 261 - irradiation loop cold leg section injection isolation valve; 27 - irradiation loop emergency afterheat removal heat exchanger; 28 - irradiation loop storage pressurization injection tank; 29 - irradiation loop injection pump; 30 - reactor pool; 31 - siphon break valve; 32 - hump pipe section; 33 - siphon break valve outlet pipe end; 34 - siphon break hole; 35 - main system inlet pipe ejector; 351 - nozzle; 352 - suction chamber; 353 - throat; 354 - diffuser; 36 - ejector isolation valve; 37 - natural circulation valve; 38 - reactor lower plenum outlet isolation valve; 39 - main system outlet ejector pipe; 40 - external heat exchanger; 41 - afterheat removal outlet line isolation valve; 42 - afterheat removal inlet line isolation valve; 43 - afterheat removal outlet line; 44 - afterheat removal inlet line; 45 - pool heat exchanger; 50 - control rod assembly; 51 - heavy water tank; 52 - heavy water discharge isolation valve; 53 - heavy water discharge tank; 60 - pressurized compartment; 61 - compartment spray water tank; 62 - compartment spray isolation valve; 63 - compartment spray header; 64 - compartment pressure suppression pipe check valve; 65 - bubbler; 66 - burst disc; 70 - reactor building; 71 - building spray water tank; 72 - building spray isolation valve; 73 - building spray header; 74 - building active filtration exhaust; 80 - external heat sink; 81 - external heat sink cooling device.

[0027] The above-described drawings are intended to provide a detailed description of the present application so that those skilled in the art can understand the technical idea of the present application, and are not intended to limit the present application. For the sake of brevity, the above-described drawings only schematically draw structures related to technical features of the present application, and do not strictly draw complete structures and all details according to actual proportions. DETAILED DESCRIPTION

[0028] The application will be further described in detail below with reference to the accompanying drawings.

[0029] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment. The appearances of the phrase "in an embodiment" in various places in the specification are not necessarily referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will understand that an embodiment described herein can be incorporated in some embodiments and can be eliminated in other embodiments without affecting the general applicability of the present application.

[0030] In the description of the present application, unless otherwise clearly specified and limited, the technical terms "mount", "connect", "connection" and the like should be understood in a broad sense, for example, they can be mechanical structural connection, or signal connection; they can be active connection, or fixed connection or integral. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0031] In the description of the present application, the terms indicating the orientation or position relationship such as "upper", "lower", "left", "right", "transverse", "vertical", "height", "length", "width" and the like are intended to accurately describe the embodiments and simplify the description, and are not intended to limit the parts or structures involved to have a specific orientation, to be installed or operated in a specific orientation, and cannot be understood as a limitation on the embodiments described herein.

[0032] In the description of the present application, the terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating relative importance or limiting the number, specific order or primary and secondary relationship of the technical features described. In the description of the present application, "a plurality of" means at least two.

[0033] The pool type reactor has a simple structure and flexible use, and can be used for carrying out various physical or engineering tests. The pool type reactor is connected with the pool, and in normal working condition, the heat of the reactor core is led out by the loop to the heat exchanger, so as to realize heat supply, gas supply or steam generation for power generation, etc. In some application scenarios, in order to carry out fuel and material irradiation test research by using the radiation generated by the reactor core, the pool type reactor is also provided with a high temperature and high pressure irradiation loop, the fuel or material to be tested is placed in the loop, and the heat in the loop is led out by a special cooling system.

[0034] In the accident condition, when the main heat exchanger of the pool type reactor is unavailable, the residual heat of the reactor core cannot be removed by conventional means. If a main system pressure boundary break accident occurs, the reactor loses a large amount of cooling water, which may cause the heat transfer of the bare reactor core to deteriorate. In addition, if there is no means to export heat after the accident, the reactor building may continue to rise in pressure, especially for reactors with high-temperature and high-pressure irradiation loops. The rupture of the high-temperature and high-pressure irradiation loop will cause further temperature and pressure rise, and even lead to overpressure failure of the reactor building and damage to the radioactive barrier.

[0035] However, due to the limitations of reactor size and actual conditions, the existing dedicated safety systems of pool type reactors all use active systems and rely on external power. Once the external power is lost, the active safety system will not be able to function normally. On the other hand, after an accident occurs, when the main circulating pump stops, the pool type reactor needs to use the cooling water in the pool to naturally circulate and remove the heat of the reactor core. However, under normal conditions, the cooling water in the reactor core flows from top to bottom, while under natural circulation, the cooling water needs to flow from bottom to top. During the reversal of the flow direction of the cooling water, there may be a flow stagnation state, causing short-term heat transfer deterioration of the reactor core. At the same time, pool type reactors usually do not have the reinforced concrete structure or steel containment of pressurized water reactors, and have weak pressure-bearing capacity, so they have limited ability to withstand the rise in temperature and pressure in the building.

[0036] To solve the above problems, an embodiment of one aspect of the present application provides a pool type reactor safety management system.

[0037] In a preferred embodiment, as shown in Figure 1 The reactor core 10 of the pool type reactor is placed in the reactor pool 30, and a reactor lower chamber 11 is formed below the reactor core 10. The reactor lower chamber 11 is provided with a reactor lower chamber outlet pipe isolation valve 38 connected to the main system outlet pipe 111, and then connected to the delay tank 12. The delay tank 12 is arranged outside the reactor pool 30 and connected to the main circulating pump 13 through a pipeline. The downstream pipeline of the main circulating pump 13 is provided with a main circulating pump post check valve 17 and a main circulating pump isolation valve 15, and connected to the inlet of the main heat exchanger 19. The outlet of the main heat exchanger 19 is connected to the main system inlet pipe injector 35 through the main system inlet pipe 112. The main system inlet pipe injector 35 and the reactor lower chamber 11 are provided with a normally closed injector isolation valve 36. The main circulating pump and its upstream and downstream circulating pipelines constitute the main circulating device of the safety management system, which is used to drive the flow of cooling water under normal conditions.

[0038] The delay tank 12 is connected in parallel with the main heat exchanger 19 and the main circulating pump 13, and an auxiliary circulating pump 14 is provided as a safety class device, and an auxiliary circulating pump post-check valve and an auxiliary circulating pump always-open isolation valve 16 are provided at the outlet of the auxiliary circulating pump 14. The auxiliary circulating pump 14 is used as an auxiliary circulating device to maintain the flow of cooling water after the main circulating pump 13 is stopped in an accident condition.

[0039] A control rod assembly 50 is provided above the reactor core 10, and the control rod assembly 50 includes neutron absorber control rods, and the reactor is shut down by inserting the control rod assembly 50 from top to bottom into the reactor core 10. A heavy water tank 51 is provided around the reactor core 10, and the heavy water tank 51 stores heavy water, and the heavy water tank 51 is configured as a passive device, and is connected to a heavy water discharge tank 53 through a heavy water discharge isolation valve 52, and the heavy water, which is a neutron moderator, can be injected into the reactor core 10 in a passive manner to reduce the reactor power or even shut down the reactor, and the passive manner can be air pressure or gravity. The control rod assembly 50 and the heavy water tank 51 form a shutdown device, which is used to shut down the reactor in an accident condition to prevent the accident from worsening.

[0040] A large amount of cooling water is stored in the reactor pool 30, and the water depth is usually 6-12m. The reactor lower chamber 11 immersed in the bottom of the reactor pool 30 is provided with a natural circulation valve 37, which is connected between the reactor lower chamber 11 and the reactor pool 30 to allow the cooling water to flow between the reactor pool 30 and the reactor lower chamber 11, and the natural circulation valve 37 is always closed in normal conditions. The natural circulation valve 37 is used as a passive circulation device to assist the cooling water in the reactor pool 30 to flow in a natural circulation manner to carry away the heat of the reactor core 10 in an accident condition.

[0041] The reactor pool 30 is further provided with a pool heat exchanger 45, which is connected to an external heat exchanger 40 outside the reactor building 70 through a residual heat removal outlet line 43 and a residual heat removal inlet line 44. One end of the residual heat removal outlet line 43 is connected to an outlet of the external heat exchanger 40, and the other end is connected to an inlet of the pool heat exchanger 45. The residual heat removal outlet line 43 is provided with a residual heat removal outlet line isolation valve 41. One end of the residual heat removal inlet line 44 is connected to an inlet of the external heat exchanger 40, and the other end is connected to an outlet of the pool heat exchanger 45. The residual heat removal inlet line 44 is provided with a residual heat removal inlet line isolation valve 42. The external heat exchanger 40 is disposed in an external heat sink 80 outside the reactor building 70. In some embodiments, the external heat sink 80 is provided as a reservoir. In preferred embodiments, the heat storage capacity of the external heat sink 80 can meet the demand of residual heat removal from the reactor core for at least 30 days. In the event of an accident, the temperature of the reactor pool 30 rises, and the temperature of the pool heat exchanger 45 is higher than that of the external heat exchanger 40. A circulation loop is formed through the residual heat removal inlet line 44 and the residual heat removal outlet line 43, and natural circulation is achieved. In further preferred embodiments, the external heat sink 80 is further provided with an external heat sink cooling device 81 to further improve the cooling capacity of the external heat sink 80 for removing heat from the reactor pool 30.

[0042] The main system outlet pipe 111 is further provided with a main system outlet pipe ejector 39, which is disposed between the reactor lower chamber outlet isolation valve 38 and the delay tank 12, and is located above the top of the reactor core 10 and below the highest point of the main system outlet pipe 111.

[0043] The main system outlet pipe ejector 39 has substantially the same structure as the main system inlet pipe ejector 35. Taking the main system inlet pipe ejector 35 as an example, the structure of the ejector is described below. Figure 3 The ejector includes a nozzle 351, a suction chamber 352, a throat 353, and a diffuser pipe 354. The nozzle 351 is connected to the upstream circulation line. The suction chamber 352 has a flared end facing the nozzle 351 and is connected to the reactor pool 30, and the other end is connected to the throat 353. The diffuser pipe 354 is connected to the throat at one end and gradually expands in diameter at the other end and is connected to the downstream circulation line through the downstream line. The cooling water is ejected from the nozzle 351 into the suction chamber 352. The suction chamber 352 receives the cooling water ejected from the nozzle 351 and also sucks part of the cooling water from the reactor pool 30. The cooling water enters the diffuser pipe 354 through the throat 353, and then flows out of the ejector. The diffuser pipe 354 can output a higher flow rate of cooling water than the flow rate of cooling water ejected from the nozzle 351, thereby achieving the effect of accelerating the circulation of cooling water. In preferred embodiments, the flow ratio of the ejector can reach 1.05-1.2 through the design of the ejector structure.

[0044] The main system inlet pipe 112 is inserted into the cooling water in the reactor pool 30, and the main system inlet pipe 112 is provided with a siphon breaking hole 34, which can be provided with one or more in different embodiments, and the single opening area is not greater than 35% of the diameter of the main system inlet pipe 112. The siphon breaking hole 34 is submerged below the cooling water level, and the immersion depth is usually 1-2 m, and the height is higher than the top of the reactor core 10 and not lower than the height of the main system outlet pipe ejector 39. The main system outlet pipe 111 is led out from the reactor lower chamber 11, including an upward segment extending to the cooling water surface and a downward segment extending to the bottom of the reactor pool 30, and a hump pipe segment 32 is formed between the upward segment and the downward segment, and the hump pipe segment 32 is protruded upward, and the protrusion height is not less than 0.5 times the diameter of the main system outlet pipe 111. In the preferred embodiment, the hump pipe segment 32 is submerged below the cooling water level. The top of the hump pipe segment 32 is connected with a branch pipeline, which is provided with a siphon breaking valve 31, and the end of the branch pipeline is provided with a siphon breaking valve outlet segment 33, which is also submerged below the cooling water level, and the immersion depth is usually 1-2 m, which is used to prevent the siphon breaking valve 31 from being opened by mistake to cause air to be sucked into the main system outlet pipe 111 under normal working conditions.

[0045] In the preferred embodiment, a plant spray water tank 71 is arranged in the reactor plant building 70, which stores cooling water and is pressurized by 0.5-5 MPa nitrogen gas, and a normally closed plant spray isolation valve 72 is arranged between the plant spray water tank 71 and the plant spray header 73. The reactor plant building 70 is also provided with a mobile filter exhaust 74.

[0046] In some embodiments, the reactor core 10 is provided with a high-temperature high-pressure irradiation loop, and the irradiation loop pressure vessel 20 is connected with the reactor core 10 through the irradiation loop heat pipe segment 24. Figure 2 For the pool-type reactor provided with a high-temperature high-pressure irradiation loop, the outlet of the irradiation loop pressure vessel 20 is connected with the inlet of the irradiation loop main heat exchanger 22 through the irradiation loop heat pipe segment 24; the outlet of the irradiation loop main heat exchanger 22 is connected with the inlet of the irradiation loop circulating pump 23 through the irradiation loop transition segment 25; the outlet of the irradiation loop circulating pump 23 is connected with the inlet of the irradiation loop pressure vessel 20 through the irradiation loop cold pipe segment 26; and the irradiation loop pressure stabilizer is connected with the irradiation loop heat pipe segment 24. In some embodiments, the high-temperature high-pressure irradiation loop is submerged in the reactor pool 30 and can be directly cooled and cooled by the cooling water; and in other embodiments, the high-temperature high-pressure irradiation loop is arranged in the reactor lower chamber 11 and is cooled by the cooling water in the reactor pool 30. Figure 2As shown, the high temperature and high pressure irradiation loop is arranged in the pressure-containing compartment 60, which is arranged outside the reactor pool 30. The pressure-containing compartment 60 is connected with the bubbler 65 through the pressure-suppressing pipe check valve 64, the bubbler 65 is immersed below the liquid surface of the reactor pool 30, usually the immersion depth is 2m-4m, and the pressure-suppressing pipe check valve 64 can prevent the water in the reactor pool 30 from entering the pressure-containing compartment 60. The wall surface of the pressure-containing compartment 60 is provided with a metal plate, and the thickness of the metal plate can be usually set to 4mm-10mm to play the role of pressure bearing and heat conduction. The wall body of the pressure-containing compartment 60 is further provided with a rupture disc 66, which is detonated when the pressure in the pressure-containing compartment 60 exceeds the limit value, so as to realize the pressure relief of the pressure-containing compartment 60. A compartment spray water tank 61 is arranged in the pressure-containing compartment 60 or in the reactor building 70, and stores cooling water pressurized by nitrogen. A normally closed compartment spray isolation valve 62 is arranged between the compartment spray water tank 61 and the compartment spray header 63. In the accident condition, the pressure-containing compartment 60 can be sprayed and cooled by the compartment spray header 63.

[0047] The irradiation loop emergency residual heat removal heat exchanger 27 is connected in parallel with the irradiation loop main heat exchanger 22, and the outlet of the irradiation loop pressurized injection tank 28 is connected with the irradiation loop hot pipe section 24 and the irradiation loop cold pipe section 26 respectively. The irradiation loop pressurized injection tank stores cooling water and is pressurized by 3MPa-5MPa nitrogen. The outlet of the irradiation loop injection pump 29 is also connected with the irradiation loop hot pipe section 24 and the irradiation loop cold pipe section 26 respectively. The irradiation loop injection pump can be a combination of a high-pressure injection pump and a low-pressure injection pump, or can only include a low-pressure injection pump. The irradiation loop pressurized injection tank 28 and the irradiation loop hot pipe section 24 are provided with a normally closed irradiation loop hot pipe section injection isolation valve 241; the irradiation loop cold pipe section 26 and the irradiation loop injection pump 29 are provided with a normally closed irradiation loop cold pipe section injection isolation valve 261. The irradiation loop hot pipe section injection isolation valve 241 and the irradiation loop cold pipe section injection isolation valve 261 can be check valves or isolation valves.

[0048] Under normal operating conditions, the main circulating pump 13 provides the forced circulation flow of the primary system, the cooling water is inputted into the main heat exchanger 19 by the main circulating pump 13 for heat exchange, and then enters the main system inlet pipe 112, part of the cooling water leaks through the siphon breaking device 34, and the rest flows to the main system inlet pipe ejector 35. Since the injector isolation valve 36 downstream of the main system inlet pipe ejector 35 is in a pipe wall state, the cooling water entering the suction chamber 352 from the nozzle 351 of the main system inlet pipe ejector 35 flows back into the reactor pool 30. The cooling water flows from the top to the bottom of the reactor core 10 into the reactor lower chamber 11 and carries away the heat generated by the reactor core 10, and then enters the main system outlet pipe 111 through the reactor lower chamber outlet isolation valve 38, and then enters the delay tank 12 through the main system outlet pipe ejector 39 and the hump pipe section 32. The cooling water flowing through the main system outlet pipe ejector 39 will suck part of the extra cooling water from the reactor pool 30 into the suction chamber 352 under the action of the injection, and the flow ratio of the main system outlet pipe ejector 39, i.e. the ratio of the diffuser outlet flow to the nozzle inlet flow, is 1.05-1.2. In the delay tank 12, the radioactive substances in the cooling water are weakened to a certain extent, and then are pumped into the main circulating pump 13 for continuous circulation.

[0049] Under accident conditions, the main circulating pump 13 is a non-safety class device and cannot ensure normal operation. The safety control process includes the following steps:

[0050] First, the control rod assembly 50 is inserted into the reactor core 10 and / or the heavy water discharge isolation valve 52 is opened to inject the heavy water in the heavy water tank 51 into the reactor core 10 in a passive manner, so as to achieve reactor shutdown by absorbing or slowing down the neutrons in the reactor core 10.

[0051] Next, the residual discharge outlet pipe line isolation valve 41 and the residual discharge inlet pipe line isolation valve 42 are opened, so that a closed circulation loop is formed between the external heat exchanger 40 and the pool heat exchanger 45 relying on natural circulation, the heat of the reactor pool is taken out to the external heat sink 80, and it is ensured that the cooling water in the reactor pool 30 does not boil after the accident. In the preferred embodiment, the heat carrying capacity of the external heat exchanger 40 and the pool heat exchanger 45 is 1%-3% of the rated power of the core. The heat capacity of the external heat sink 80 at least meets the requirement of residual heat removal of the core for thirty days, and in the case of further cooling by the external heat sink cooling device 81, the cooling process can be carried out stably for a long time. The medium flowing in the external heat exchanger 40 and the pool heat exchanger 45 can be liquid or gas, for example, cooling water or evaporative medium in a heat pipe can be used.

[0052] Since the post-accident main circulation pump 13 is not a safety class equipment, it cannot be guaranteed to operate, and the post-accident operation of the auxiliary circulation pump 14 is used to provide forced circulation for the main system. Since the auxiliary circulation pump 14 operates in the stage after the reactor is shut down, and the decay heat of the reactor core is much smaller than the core power in normal operation, the flow of the auxiliary circulation pump 14 can be much smaller than that of the main circulation pump 13. To cope with single failure, at least two parallel auxiliary circulation pumps 14 are provided, and the rated flow of a single auxiliary circulation pump 14 is not more than 20% of the total flow in normal operation.

[0053] When the decay heat of the reactor core decreases to a first threshold value (1% to 2% of the rated power of the reactor core), the ejector isolation valve 36 is opened, and the reactor lower plenum outlet isolation valve 38 is closed (to prevent misoperation, the opening action of the ejector isolation valve 36 and the closing action of the reactor lower plenum outlet isolation valve 38 are interlocked). At this time, the flow from the auxiliary circulation pump 14 can pass through the main system inlet pipe ejector 35 and the ejector isolation valve 36 into the reactor lower plenum 11, and then flow from the reactor core 10 downward and upward into the reactor pool 30, realizing a rapid reversal of the flow direction of the reactor core. The water entering the reactor pool 30 can enter the main system outlet pipe 111 from the suction chamber of the main system outlet pipe ejector 39, re-enter the inlet of the auxiliary circulation pump 14, and realize circulation. Since the entire process is driven by the forced flow of the auxiliary circulation pump, compared with relying on the natural circulation drive, flow stagnation when the flow direction of the reactor core is reversed is avoided.

[0054] When the flow direction of the reactor core is reversed from downward to upward, the auxiliary circulation pump 14 can be closed, so that the forced circulation from the main system loop is converted to natural circulation in the reactor pool, i.e., the water in the reactor pool 30 enters the suction chamber of the main system inlet pipe ejector 35, passes through the ejector isolation valve 36 into the reactor lower plenum 11, and then flows from the reactor core 10 downward and upward into the reactor pool 30, and then re-enters the suction chamber of the main system inlet pipe ejector 35. When the decay heat of the reactor core continues to decrease (below 1% of the rated power of the reactor core), to further reduce the resistance of the natural circulation, the natural circulation valve 37 can be opened again. To cope with single failure, at least two parallel natural circulation valves 37 are provided. The flow passage diameter of the natural circulation valve 37 is not less than the throat diameter of the main system inlet pipe ejector 35.

[0055] For a LOCA accident, if the break location is in the part of the main system outlet pipe 111 and the main system inlet pipe 112 located in the reactor pool 30, the reactor pool 30 will not lose water inventory.

[0056] If the break location is outside the reactor pool 30, the siphon break valve 31 can be opened to deal with single failure, and at least two siphon break valves 31 are provided in parallel. When the water level in the reactor pool 30 drops below the siphon break valve outlet pipe end 33, air will be introduced into the hump pipe section 32 of the main system outlet pipe 111 to block the flow path, thereby preventing the water in the reactor pool 30 from further losing from the break. Due to the high elevation and small volume of the hump top of the hump pipe section 32, air accumulation is facilitated, and the siphon break effect is good. In addition, as an optional design, if all siphon break valves 31 fail to open due to failure, air can also enter the main system outlet pipe 111 from the main system outlet pipe ejector 39 suction chamber once the water level in the reactor pool 30 drops below the main system outlet pipe ejector 39 suction chamber, which also plays a siphon break role. Since the main system outlet pipe ejector 39 is a passive component, it has very high reliability.

[0057] If the break location is outside the reactor pool 30 of the main system outlet pipe 112, when the water level in the reactor pool 30 drops below the siphon break hole 34, air will be introduced into the main system outlet pipe 112 to block the flow path through the siphon break hole 34, thereby preventing the water in the reactor pool 30 from further losing from the break. Since the siphon break hole 34 is a passive component, it has very high reliability.

[0058] When the post-accident reactor building 70 pressure is high, the building spray isolation valve 72 can be opened, so that the cooling water in the building spray tank 71 is pushed by the accumulated gas to spray cooling water into the reactor building 70 through the building spray head 73, rapidly reducing the pressure in the reactor building 70 in a short time, and the pressure is lower than the external atmospheric pressure. In addition, the building active filtration exhaust 74 can be opened at the same time to continuously discharge filtered gas from the reactor building 70, avoiding the pressure in the reactor building 70 exceeding the limit value in the long-term stage after the building spray tank 71 is exhausted, and the pressure is always lower than the external atmospheric pressure.

[0059] For the pool type reactor design with high temperature and high pressure irradiation loop, when the high temperature and high pressure irradiation loop is designed to be immersed in the reactor pool 30, the high temperature and high pressure irradiation loop will be immersed and condensed by the cooling water of the reactor pool 30 after the accident of the high temperature and high pressure irradiation loop causing the release of high temperature and high pressure fluid. When the high temperature and high pressure irradiation loop is arranged outside the reactor pool 30, the high temperature and high pressure irradiation loop is arranged in the pressure-containing compartment 60, so that the high temperature and high pressure fluid released from the high temperature and high pressure irradiation loop is contained in the pressure-containing compartment 60. For the high temperature and high pressure fluid released into the pressure-containing compartment 60, on the one hand, it is condensed by entering the reactor pool 30 through the compartment pressure suppression pipe check valve 64 and the bubbler 65; on the other hand, the compartment spray isolation valve 62 can be opened, so that the cooling water in the compartment spray water tank 61 is sprayed into the pressure-containing compartment 60 under the push of the pressure gas through the compartment spray head 63, rapidly reducing the pressure of the pressure-containing compartment 60 in a short time. In addition, the inner surface of the wall of the pressure-containing compartment 60 is attached with a metal plate (thickness 4mm-10mm), which not only can absorb the heat of the high temperature and high pressure fluid in the compartment, but also can ensure that the pressure-containing compartment 60 has higher pressure-bearing capacity. Finally, in the extreme case, even if the pressure of the pressure-containing compartment 60 exceeds a certain limit, the rupture disc 66 can be opened to release the high temperature and high pressure fluid in the compartment into the reactor building 70 to prevent the overpressure of the pressure-containing compartment 60. And after the high temperature and high pressure fluid is released into the reactor building 70, the reactor building 70 can also ensure that it will not cause overpressure of the reactor building 70 and the pressure is lower than the external atmospheric pressure through the diffusion and dilution effect (the volume of the reactor building 70 is much larger than that of the pressure-containing compartment 60), the building spray, the building mobile filtering exhaust and the like.

[0060] For the pool type reactor design with high temperature and high pressure irradiation loop, when a non-LOCA accident occurs, heat can be led out through the irradiation loop emergency residual heat removal heat exchanger 27, which can be active or passive; when a LOCA accident occurs, due to the reduction of the system pressure of the high temperature and high pressure irradiation loop, the irradiation loop heat pipe section injection isolation valve 241 and the irradiation loop cold pipe section injection isolation valve 261 can be opened, and the irradiation loop pressure accumulation injection tank 28 can supplement the coolant into the loop under the push of the pressure gas, and when the irradiation loop pressure accumulation injection tank 28 is exhausted, the irradiation loop injection pump 29 can continue to supplement the coolant into the loop, and the source of the coolant can be the reactor pool 30. The irradiation loop pressure accumulation injection tank 28 and the irradiation loop injection pump 29 supplement the coolant to the irradiation loop heat pipe section 24 and the irradiation loop cold pipe section 26 by passing through the irradiation loop heat pipe section injection isolation valve 241 and the irradiation loop cold pipe section injection isolation valve 261 at the same time, so as to ensure that the coolant enters the loop regardless of whether the break occurs in the irradiation loop heat pipe section 24 or the irradiation loop cold pipe section 26.

[0061] The pool type reactor safety management method provided by the above embodiment combines active safety technology and passive safety technology, and can effectively realize rapid shutdown and residual heat removal under accident conditions, prevent the reactor core from being overheated due to stagnation of the reactor core cooling water after shutdown of the main circulating pump, reduce the risk of radioactive material leakage, and effectively improve the safety and reliability of the pool type reactor.

[0062] The purpose of the above embodiment is to make a further detailed description of the present application in combination with the drawings, so that those skilled in the art can understand the technical concept of the present application. Within the scope of the present application, optimization or equivalent replacement of the structures of the parts involved or the method steps, and combination of the implementation manners in different embodiments without structural and principle conflicts, all fall within the protection scope of the present application.

Claims

1. A pool-type reactor safety management system, characterized in that: include: Shutdown device, passive residual heat removal device, main circulation device, auxiliary circulation device and passive circulation device, among which, The shutdown device is used to intervene in the reactor core to achieve shutdown under accident conditions; The passive residual heat removal device includes a water pool heat exchanger, an external heat exchanger and an external heat sink, wherein the water pool heat exchanger is arranged in the reactor water pool, and the external heat exchanger is arranged in the external heat sink. The water pool heat exchanger and the external heat exchanger are connected to form a circulation loop, and a natural circulation is formed when the temperature of the water pool heat exchanger is higher than that of the external heat exchanger; The main circulation device includes a main circulation pump and a circulation pipeline. The main circulation pump drives the cooling water circulation under normal operating conditions. The two ends of the circulation pipeline are respectively connected to the lower chamber of the reactor. A siphon breaking hole is provided at a position upstream of the lower chamber of the reactor and higher than the reactor core. The circulation pipeline is provided with an isolation device upstream of the lower chamber of the reactor. When the isolation device is closed, the cooling water in the circulation pipeline flows into the reactor water pool through the isolation device. When the isolation device is opened, at least part of the cooling water in the circulation pipeline flows into the lower chamber of the reactor through the isolation device. The auxiliary circulation device includes an auxiliary circulation pump, which is connected in parallel to the main circulation pump; The passive circulation device includes a natural circulation valve arranged in the lower chamber of the reactor.

2. The pool-type reactor safety management system according to claim 1, characterized in that: The shutdown device includes a control rod assembly and / or a heavy water tank. The control rod assembly includes a neutron absorber control rod, and the control rod assembly is capable of inserting the neutron absorber control rod into the core; the heavy water tank stores heavy water, and the heavy water tank is capable of injecting the heavy water into the core in a passive manner.

3. The pool-type reactor safety management system according to claim 1 or 2, characterized in that: The external heat sink is further provided with an external heat sink cooling device for reducing the temperature of the external heat sink.

4. The pool-type reactor safety management system according to claim 1 or 2, characterized in that: The isolation device includes a main system inlet pipe ejector and an ejector isolation valve; The main system inlet pipe ejector includes a nozzle, a suction chamber, a throat, and a diffuser; The nozzle is connected to the upstream circulation pipeline; the suction chamber is in a bell-shaped shape with an enlarged diameter at one end toward the nozzle and is connected to the reactor water pool, and the other end is connected to the throat; one end of the diffuser is connected to the throat, and the other end gradually enlarges in diameter and is connected to the ejector isolation valve; The main system inlet pipe ejector is connected to the lower chamber of the reactor through an ejector isolation valve. When the ejector isolation valve is closed, the cooling water in the circulation pipeline flows back into the reactor water pool through the main system inlet pipe ejector; when the ejector isolation valve is opened, at least part of the cooling water in the circulation pipeline and part of the cooling water in the reactor water pool flow into the lower chamber of the reactor through the main system inlet pipe ejector.

5. The pool-type reactor safety management system according to claim 4, characterized in that: The drainage ratio of the main system inlet pipe ejector is 1.05-1.

2.

6. The pool-type reactor safety management system according to claim 1 or 2, characterized in that: The circulation pipeline is further provided with a main system outlet pipe injector downstream of the reactor lower chamber, and the main system outlet pipe injector includes a nozzle, a suction chamber, a throat and a diffuser; The nozzle is connected to the upstream circulation pipeline; the suction chamber is in a trumpet shape with an enlarged diameter at one end toward the nozzle and is connected to the reactor water pool, and the other end is connected to the throat; one end of the diffuser is connected to the throat, and the other end has a gradually enlarged diameter and is connected to the circulation pipeline.

7. The pool-type reactor safety management system according to claim 1 or 2, characterized in that: It also includes a spray system, which includes a passive water storage tank. The passive water storage tank can spray cooling water to the plant where the reactor is located under accident conditions.

8. The pool-type reactor safety management system according to claim 7, characterized in that: It also includes a filtering and exhaust system, which is used to filter radioactive pollutants and discharge the gas in the plant where the reactor is located.

9. The pool-type reactor safety management system according to claim 1 or 2, characterized in that: The pool reactor is equipped with high-temperature and high-pressure irradiation piping; The pool-type reactor safety management system includes a pressure compartment, the high-temperature and high-pressure irradiation pipeline is enclosed in the pressure compartment, and the wall of the pressure compartment is provided with a heat conducting plate to dissipate the heat in the pressure compartment; the pressure compartment also includes a pressure suppression tube, one end of the pressure suppression tube is connected to the pressure compartment and the other end is immersed in the cooling water of the reactor pool, and is provided with a check valve and a bubbler.

10. The pool-type reactor safety management system according to claim 9, characterized in that: The pressure-bearing compartment is further provided with a bursting disc, and when the bursting disc explodes, the pressure-bearing compartment is depressurized.

11. A pool-type reactor safety management method, characterized in that: A pool-type reactor safety management system according to any one of claims 1 to 10 is used, and comprises the following steps: In accident conditions, Step a): activating the shutdown device to achieve shutdown; Step b): using the auxiliary circulation pump to force cooling water to circulate until the core decay heat is reduced to below a first threshold value of the rated power; Step c): opening the isolation device, shutting off the downstream pipeline of the lower chamber of the reactor, and allowing the auxiliary circulation pump to drive cooling water through the isolation device into the lower chamber of the reactor and out of the upper part of the reactor, thereby reversing the flow direction of the core cooling water; Step d): after the flow direction of the core cooling water is reversed, the auxiliary circulation pump is turned off to allow natural circulation; Step e): when the core decay heat decreases below a second threshold value of the rated power, opening the natural circulation valve.

12. The pool reactor safety management method according to claim 11, characterized in that: The first threshold is 2% of the rated power of the core; the second threshold is 1% of the rated power of the core.

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