CN220651664U - Passive safety system and ATF fuel-based reactor - Google Patents

Abstract

The utility model discloses an passive safety system and a reactor based on ATF fuel, the passive safety system comprises: the reactor coolant system comprises a pressure vessel, a steam generator, a hot pipe section and a cold pipe section, wherein the inlet end and the outlet end of the steam generator are respectively connected with the pressure vessel through the hot pipe section and the cold pipe section to form a coolant circulation loop; and the safety injection system comprises an injection pipeline, a long-time safety injection box for injecting water into the pressure vessel through the injection pipeline, a refueling water tank and a pit. On one hand, the reactor core adopts ATF fuel with accident fault tolerance capability, so that the safety and economy of nuclear power are effectively improved. On the other hand, the long-time-effect safety injection box, the material-changing water tank and the pit are adopted to be matched with the safety injection system, so that the system can be simplified, and the cost can be saved; secondly, the long-time-effect safety injection box can effectively cope with small-size break accidents, and the safety and the economy are further improved.

Description

Passive safety system and ATF fuel-based reactor

Technical Field

The utility model relates to the technical field of nuclear power, in particular to a passive safety system and a reactor based on ATF fuel.

Background

The reactor core of the conventional nuclear power station in the related technology is loaded with the conventional uranium zirconium (UO 2-Zr) fuel, namely the pellet material is uranium dioxide, and the cladding material is zirconium alloy; after a water loss accident, the fuel pellets and the cladding can be quickly heated, and the zirconium alloy cladding reacts with high-temperature water/steam to generate zirconium water, so that a large amount of reaction heat is released, and the fuel pellets and the cladding are easy to fail.

In addition, after a water loss accident occurs in the nuclear power station, coolant is injected into the reactor core through the injection system to ensure the sufficient cooling of the reactor core, but the injection system in the related art has the following disadvantages:

firstly, an injection system consists of a high-pressure injection system, a medium-pressure injection system and a low-pressure injection system, so that the system is complex and complicated;

secondly, the safety injection system injects a large flow of coolant, and part of coolant can enter the safety shell to bypass through the break, so that the safety injection water is wasted; and for small-sized break accidents, coolant is difficult to enter the pressure vessel, so that the reactor core is dry and damaged.

Disclosure of Invention

The utility model aims to solve the technical problem of providing a passive safety system and a reactor based on ATF fuel.

The technical scheme adopted for solving the technical problems is as follows:

there is provided an passive safety system comprising:

the reactor coolant system comprises a pressure vessel, a steam generator, a hot pipe section and a cold pipe section, wherein the inlet end and the outlet end of the steam generator are respectively connected with the pressure vessel through the hot pipe section and the cold pipe section to form a coolant circulation loop; and

the safety injection system comprises a long-time safety injection box, a refueling water tank, a pit and an injection pipeline, wherein a safety injection point is arranged on the pressure container, and the long-time safety injection box, the refueling water tank and the pit are connected with the safety injection point through the injection pipeline so as to inject coolant into the pressure container.

In some embodiments, the water level of the refueling water tank and the water level of the pit are higher than the plane of the safety injection point.

In some embodiments, the injection line comprises a first injection line, two ends of the first injection line are respectively connected to the safety injection point and the refueling water tank; a first branch point and a second branch point are arranged on the first injection pipeline, and the distance from the first branch point to the safety point is greater than the distance from the second branch point to the safety point; and a first explosion valve and a first check valve which are connected in series are arranged between the first branch point and the second branch point.

In some embodiments, the injection line comprises a second injection line, two ends of the second injection line are respectively connected to the pit and the first branch point; and a second explosion valve and a second check valve which are connected in series are arranged on the second injection pipeline.

In some embodiments, the injection line comprises a third injection line, two ends of the third injection line are respectively connected to the long-term safety injection box and the second branch point; the third injection pipeline is provided with an electric valve and a third check valve which are connected in series; the water pressure in the long-time-effect safety injection box is larger than the pressure of the safety injection point.

In some embodiments, the passive safety system further comprises a secondary side waste heat removal system comprising a heat exchanger, a cooling water tank, an inlet channel, and an outlet channel, the steam generator further comprising a steam line and a water supply line, the steam generator being connected to the inlet channel and the outlet channel by the steam line and the water supply line, respectively; the heat exchanger is arranged in the cooling water tank, the inlet end and the outlet end of the heat exchanger are respectively connected with the inlet channel and the outlet channel, the plane of the outlet end is higher than the plane of one end of the water supply pipeline connected with the steam generator, and the inlet end is higher than or flush with the outlet end so as to form an passive water vapor circulation loop.

In some embodiments, the secondary side waste heat removal system further comprises a plurality of water replenishment tanks disposed in parallel with the heat exchanger, the water replenishment tanks having inlet ends higher than outlet ends, the inlet ends being connected to the inlet channels, and the outlet ends being connected to the outlet channels.

In some embodiments, the inlet end of the water replenishing tank is provided with a diffuser, a plurality of small holes are formed in the diffuser, and water vapor in the inlet channel enters the water replenishing tank through the diffuser so as to reduce the rate of water vapor entering the water replenishing tank.

In some embodiments, the reactor coolant system further comprises a pressurizer, the passive safety system further comprises an automatic pressure relief valve comprising a first stage pressure relief valve, a second stage pressure relief valve, a first pressure relief line, and a second pressure relief line, and a containment vessel; the pressure stabilizer is connected to the hot pipe section, two ends of the first pressure relief pipeline are respectively connected to the pressure stabilizer and the reloading water tank, a sprayer is arranged at one end connected with the reloading water tank, and the sprayer is immersed in water of the reloading water tank; two ends of the second pressure relief pipeline are respectively connected with the hot pipe section and the inner space of the containment; the first stage pressure relief valve is disposed on the first pressure relief line and the second stage pressure relief valve is disposed on the second pressure relief line.

Also provided is an ATF fuel-based reactor comprising an ATF fuel assembly and the passive safety system, the ATF fuel assembly being disposed within the pressure vessel, and a fuel rod in the ATF fuel assembly comprising a pellet and an envelope, the pellet being a UO2-BeO pellet made of a UO2 material and added with a BeO material, and/or the envelope being a SiC envelope made of a SiC material.

The implementation of the utility model has the following beneficial effects: on one hand, ATF fuel with accident fault tolerance is used as a reactor core, so that the safety and economy of nuclear power are effectively improved. On the other hand, the long-time-effect safety injection box, the material-changing water tank and the pit matched safety injection system are adopted, so that the system is simplified and the cost is saved; secondly, the long-time-effect safety injection box can effectively cope with the water loss accident of small-size break, and further improves the safety and the economical efficiency.

Drawings

The utility model will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a schematic illustration of the passive safety system and ATF fuel based reactor configuration in some embodiments of the present utility model;

FIG. 2 is a schematic illustration of the connection of the reactor coolant system and the automatic pressure relief valve of the passive safety system shown in FIG. 1;

FIG. 3 is a schematic diagram of a connection structure between the safety injection system and the pressure vessel of the passive safety system shown in FIG. 1;

FIG. 4 is a schematic diagram of a connection structure between the secondary side waste heat removal system of the passive safety system shown in FIG. 1 and a steam generator;

fig. 5 is a schematic structural view of a water replenishing tank of the secondary side residual heat removal system shown in fig. 4.

Detailed Description

For a clearer understanding of technical features, objects and effects of the present utility model, a detailed description of embodiments of the present utility model will be made with reference to the accompanying drawings. In the following description, it should be understood that the directions or positional relationships indicated by "front", "rear", "upper", "lower", "left", "right", "longitudinal", "transverse", "vertical", "horizontal", "top", "bottom", "inner", "outer", "head", "tail", etc. are configured and operated in specific directions based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present utility model, and do not indicate that the apparatus or element to be referred to must have specific directions, and thus should not be construed as limiting the present utility model.

It should also be noted that unless explicitly stated or limited otherwise, terms such as "mounted," "connected," "secured," "disposed," and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. When an element is referred to as being "on" or "under" another element, it can be "directly" or "indirectly" on the other element or one or more intervening elements may also be present. The terms "first," "second," "third," and the like are used merely for convenience in describing the present utility model and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated, whereby features defining "first," "second," "third," etc. may explicitly or implicitly include one or more such features. The specific meaning of the above terms in the present utility model can be understood by those of ordinary skill in the art according to the specific circumstances.

In the following description, for purposes of explanation and not limitation, specific details are set forth such as the particular system architecture, techniques, etc., in order to provide a thorough understanding of the embodiments of the present utility model. It will be apparent, however, to one skilled in the art that the present utility model may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present utility model with unnecessary detail.

Fig. 1 illustrates an ATF fuel based reactor in some embodiments of the utility model, which may include an passive safety system a and an ATF fuel assembly B. The passive safety system A is used for coping with water loss accidents of the nuclear reactor, and the ATF fuel assembly B is used for accommodating core fuel of the nuclear reactor.

As also shown in fig. 1, passive safety system a may include, in some embodiments, a reactor coolant system 1, an injection system 2, a secondary side waste heat removal system 3, an automatic pressure relief valve 4, and a containment 5. The reactor coolant system 1 is arranged inside a containment vessel 5 for providing a coolant circulation loop for the containment system. The injection system 2 is arranged inside the containment vessel 5 for injecting a coolant (e.g. water) into the reactor cooling system 1. The secondary side waste heat removal system 3 is arranged outside the containment 5 and is used for providing a water vapor circulation loop for the containment. An automatic pressure relief valve 4 is connected to the reactor coolant system 1 for rapidly relieving pressure in the primary loop after a pipe segment breach to ensure that the injection system 2 is smoothly injecting water into the reactor core. The containment vessel 5 is used to prevent the escape of radioactive materials after an accident.

As further shown in fig. 2, the reactor coolant system 1 may include, in some embodiments, a pressure vessel 11, a steam generator 12, a hot leg 13, a cold leg 14, a main pump 15, and a pressurizer 16. A pressure vessel 11 is provided at the bottom of the containment vessel 5 for use as an important pressure boundary for the reactor-loop. The steam generator 12 is provided with an inlet end and an outlet end, and the inlet end and the outlet end are respectively connected with the pressure vessel 11 through a hot pipe section 13 and a cold pipe section 14; the steam generator 12 is used as a boundary between the primary loop and the secondary loop to transfer the heat generated by the reactor core to the secondary side; the hot pipe section 13 is used for delivering high-temperature and high-pressure water in the pressure vessel 11 to the steam generator 12, and the cold pipe section 14 is used for delivering cooled water in the steam generator 12 to the pressure vessel 11. A main pump 15 is provided between the outlet end of the steam generator 12 and the cold leg 14 for powering the water circulation within the reactor coolant system 1. A pressure regulator 16 is connected to the hot leg 13 for stabilizing the pressure of the primary circuit.

The reactor coolant system 1 is formed with a coolant circulation loop, specifically, water as a coolant absorbs heat generated by nuclear fission in a reactor core in the pressure vessel 11, and then enters a U-shaped pipe of the steam generator 12 along the hot pipe section 13 to transfer the heat to water outside the U-shaped pipe to be saturated steam; the cooled water in the U-shaped pipe is pushed back into the pressure vessel 11 by the main pump 15 to absorb the heat generated by the reactor core again, and the water is circulated in this way, so that a closed heat absorption and release circulation process is formed.

As shown in fig. 3, the safety injection system 2 may include, in some embodiments, a refueling water tank 21, a pit 22, a long-term safety injection tank 23, and an injection line 24. The long-term safety injection tank 23 is used for providing low-flow water injection for the reactor core, the refueling water tank 21 is used for providing high-flow water injection for the reactor core, and the pit 22 is used for providing long-time recycling water injection for the reactor core; the refueling water tank 21, the pit 22 and the long-term safety injection tank 23 are respectively connected to a pressure vessel direct injection (DVI) nozzle (not shown) provided on the side wall of the pressure vessel 11 through injection lines 24; it will be appreciated that the connection point of the injection line 24 to the nozzle is the safety point 111 where the safety injection system 2 injects water for the reactor coolant system 1.

In some embodiments, the water level of the refueling water tank 21 and the water level of the pit 22 are higher than the plane of the Yu An injection point 111, so as to ensure that the water in the refueling water tank 21 and the pit 22 can automatically flow into the pressure container 11 by utilizing the height difference, thereby realizing the passive operation of the safety injection system 2. In addition, the ATF fuel assembly B is disposed inside the pressure vessel 11, and the injection point 111 is located at a plane higher than the top plane of the ATF fuel assembly B, so as to ensure that the ATF fuel assembly B is immersed in the water in the pressure vessel 11.

In some embodiments, the refueling water tank 21 is a high level water tank placed in a containment vessel with a height difference of more than 10m from the filling point 111 at the bottom and a water volume of about 2000m inside ³ 。

In some embodiments, the pit 22 is provided with a pit screen (not shown) through which water within the pit 22 is injected into the pressure vessel 11 to prevent debris from pipe break out from clogging the injection line 24.

In some embodiments, in the early stage of a small-sized break accident, the pressure relief effect of the automatic pressure relief valve 4 is limited, and the long-term safety injection tank 23 may be provided with nitrogen pressurization, and the initial pressure of nitrogen may be 2Mpa, so as to ensure that the internal water pressure of the long-term safety injection tank 23 is greater than the pressure of the safety injection point 111 during operation, and the coolant can be smoothly injected into the pressure vessel 11; a resistance adjusting orifice plate (not shown) is arranged on the water outlet line of the long-time-effect safety injection box 23 and is used for adjusting the resistance of the water outlet line; after a loss of water accident, the long-term safety injection tank 23 can provide a long-term (for example, thousands of seconds) small flow of water for the reactor core under the action of nitrogen and the resistance adjusting orifice plate.

As also shown in fig. 3, injection line 24 may include a first injection line 241, a second injection line 242, and a third injection line 243 in some embodiments. Both ends of the first injection line 241 are respectively connected to the safety injection point 111 and the refueling water tank 21; the first injection pipeline 241 is provided with a first branch point 2411 and a second branch point 2412, and the distance between the first branch point 2411 and the safety point 111 is greater than the distance between the second branch point 2412 and the safety point 111. Both ends of the second injection line 242 are connected to the first branch point 2411 and the pit 22, respectively. Both ends of the third injection line 243 are respectively connected to the second branch point 2412 and the long-term safety injection tank 23.

In some embodiments, two ends of the first injection line 241 are respectively communicated with the charge water tank 21 and the pressure vessel 11, two ends of the second injection line 242 are respectively communicated with the pit 22 and the first injection line 241, preferably, a port at one end of the first injection line 241 connected with the charge water tank 21 is arranged at the bottom of the charge water tank 21, and a port at one end of the second injection line 242 connected with the pit 22 is arranged at the bottom of the pit 22, so as to ensure that water in the charge water tank 21 and the pit 22 automatically flows into the injection line 24 by gravity. It will be appreciated that the port at the end of the second injection line 242 that is connected to the pit 22 is not limited to being located at the bottom of the pit 22, as long as it is ensured that the water within the pit 22 is submerged in the pit screen and passes through the pit screen into the second injection line 242.

As also shown in fig. 3, in some embodiments, a first burst valve 2413 and a first check valve 2414 are disposed between a first branching point 2411 and a second branching point 2412 on the first injection line 241, a second burst valve 2421 and a second check valve 2422 are disposed on the second injection line 242, and an electric valve 2431 and a third check valve 2432 are disposed on the third injection line 243, which are disposed and arranged for effectively coping with water loss accidents of different size breaches.

Specifically, in the early stage of a water loss accident (for example, a small break with a size of 2.5cm occurring in a cold pipe section), the pipelines where the first burst valve 2413 and the first check valve 2414 are located and the pipelines where the second burst valve 2421 and the second check valve 2422 are located are in a closed state, the pipelines where the electric valve 2431 and the third check valve 2432 are located are in a conducting state, and the long-term water tank 23 performs unidirectional water injection into the pressure vessel 11 through the injection pipeline 24; the water injection process has the characteristics of long time and small flow, wherein the long time water injection prevents the reactor core from drying and damaging, in addition, the small flow water injection can avoid the bypass of excessive water injection from the breach to the containment 5 to cause waste, so the injection process has long timeliness.

In the event of a water loss accident with a large-size break, or in the event of a water loss accident with a small-size break and after the water injection of the long-term water tank 23, the pipelines where the first explosion valve 2413 and the first check valve 2414 are located are in a conducting state, the pipelines where the second explosion valve 2421 and the second check valve 2422 are located are in a sealing state, and the reload water tank 21 performs self-flow and unidirectional water injection into the pressure vessel 11 through the injection pipeline 24, and the water injection has the characteristic of larger flow.

When the water level in the refueling water tank 21 drops to the low water level setting value, the second explosion valve 2421 and the second check valve 2422 are in a conducting state, and the pit 23 is self-flowed and one-way filled with water through the injection line 24 into the pressure vessel 11; the water injection process has the characteristic of recycling, namely, the pit 23 is used for collecting the coolant and condensed reflux water in the containment 5 and then injecting the coolant and condensed reflux water into the reactor core, so that the long-term cooling effect of the reactor core is realized, and the operator is not required to intervene within 72 hours after the water loss accident occurs.

As shown in fig. 4, the secondary side waste heat removal system 3 may include an inlet channel 31, an outlet channel 32, a heat exchanger 33, and a cooling water tank 34 in some embodiments. The steam generator 12 is provided with a steam outlet and a water feed mouth in some embodiments, the steam outlet is arranged at the top of the steam generator 12, and a steam pipeline 121 is connected for outputting steam for the secondary side waste heat discharging system 3; the water feed mouth is connected to a water feed line 122 for supplying water to the steam generator 12. Both ends of the inlet passage 31 are connected to the steam line 121 and the inlet end of the heat exchanger 33, respectively, and both ends of the outlet passage 32 are connected to the water supply line 122 and the outlet end of the heat exchanger 33, respectively.

The heat exchanger 33 is disposed in the cooling water tank 34 and immersed in the water body of the cooling water tank 34 for exchanging heat with the cooling water tank 34. The water volume of the cooling water tank 34 is large enough to ensure the effect of carrying core decay heat out within 72 hours; a water replenishment line 341 is connected to the bottom of the cooling water tank 34 in some embodiments for replenishing the cooling water tank 34.

The secondary side waste heat discharging system 3 forms a water-gas circulation loop, specifically, the water in the U-shaped pipe of the steam generator 12 transfers heat to the water outside the U-shaped pipe to be changed into water vapor, the water vapor enters the heat exchanger 33 through the steam pipeline 121 and the inlet channel 31, the heat exchanger 33 transfers the heat of the water vapor to the cooling water tank 34 and the atmosphere, the water vapor is cooled into condensed water, and the condensed water flows into the steam generator 12 through the outlet channel 32 and the water supply pipeline 122 to be reheated, and the circulation is repeated in such a way to form a closed heat absorption and heat release circulation process.

As further shown in fig. 4, the secondary side waste heat removal system 3 also includes a makeup tank 35 and an isolation valve 36 in some embodiments. The water replenishing tank 35 is arranged in parallel with the heat exchanger 33, i.e. the inlet end and the outlet end of the water replenishing tank 35 are respectively connected with the inlet channel 31 and the outlet channel 32; the water supplementing tank 35 is used for ensuring that enough water is injected into the loop after the secondary side waste heat discharging system 3 is started, so that the water in the U-shaped pipe of the steam generator 12 is cooled more effectively, natural circulation is built more quickly, and effective carrying-out of decay heat is ensured.

As shown in fig. 5, the inlet end of the water replenishing tank 35 is provided with a diffuser 351, i.e., hundreds of small holes with diameters of about 1cm are provided at the opening end, and water vapor in the inlet channel 31 enters the water replenishing tank 35 through the diffuser 351 to reduce the flow rate of the vapor entering the water replenishing tank 35, thereby effectively reducing the possibility that water in the water replenishing tank 35 contacts with the vapor to generate water hammer and avoiding damage to equipment.

The isolation valves 36 are respectively disposed on the inlet channel 31, the outlet channel 32, and the branch channel where the water replenishment tank 35 is located, for controlling the conduction of the circuit.

In some embodiments, the inlet end of the heat exchanger 33 is higher than the outlet end thereof, the inlet end of the water replenishing tank 35 is higher than the outlet end thereof, and the outlet end of the heat exchanger 33 and the outlet end of the water replenishing tank 35 are higher than the plane of the water feeding mouth of the steam generator 12, so as to ensure that the water in the heat exchanger 33 and the water replenishing tank 35 can automatically flow into the steam generator 12 by utilizing the height difference, thereby realizing passive operation in the water vapor circulation loop. In addition, the inlet end of the heat exchanger 33 may be flush with the outlet end thereof, as long as the passive operation of the water vapor circulation circuit is not affected.

Referring to fig. 1 and 2 in combination, the automatic pressure relief valve 4 may include a first stage pressure relief valve 41, a second stage pressure relief valve 42, a first pressure relief line 43, and a second pressure relief line 44 in some embodiments. The first stage pressure relief valve 41 is disposed on the first pressure relief pipeline 43, and is used for rapidly releasing pressure of the primary loop after the pipeline is broken, so as to ensure that the passive injection system 2 can smoothly inject water into the reactor core; two ends of the first pressure relief pipeline 43 are respectively connected with the pressure stabilizer 16 and the reloading water tank 21, and one end connected with the reloading water tank 21 is provided with a sprayer 431 and immersed in water of the reloading water tank 21; the first pressure relief line 43 is further provided with an electrically operated valve 432 in series with the first pressure relief valve 41 for controlling the communication of the first pressure relief line 43.

A second pressure relief valve 42 is provided on a second pressure relief line 44 for further pressure relief of the primary circuit; the second pressure relief line 44 has both ends connected to the inner spaces of the hot pipe section 13 and the containment vessel 5, respectively.

By the arrangement of the two-stage pressure relief valve, the function of quickly relieving the pressure of the first loop can be realized, and as can be understood, when a water loss accident occurs, the first-stage pressure relief valve 41 is opened, and high-temperature water and water vapor of the first loop are sprayed into water of the charge water tank 21 through the first pressure relief pipeline 43 so as to reduce the pressure of the first loop and increase the water pressure in the charge water tank 21, and the water in the subsequent charge water tank 21 can be ensured to be smoothly injected into the pressure container 11; when the pressure relief speed of the first stage pressure relief valve 41 does not meet the demand, the second stage pressure relief valve 42 is opened, and the high temperature water and water vapor of the first circuit are sprayed into the inner space of the containment vessel 5 through the second pressure relief line 44 to further relieve the pressure of the first circuit.

As shown in fig. 1, the ATF fuel assembly B is an accident tolerant fuel, which is disposed inside the pressure vessel 11 and near the bottom of the pressure vessel 11; the fuel rod of ATF fuel assembly B in some embodiments includes pellets (not shown) and an envelope (not shown) that is wrapped around the pellets. The core block adopts UO ₂ UO made of (uranium dioxide) material and added with BeO (beryllium oxide) material ₂ BeO pellets, with conventional UO ₂ Compared with the pellet, the thermal conductivity of the pellet is greatly improved, and the initial temperature of the pellet and the peak temperature of the cladding after water loss accidents can be effectively reduced. The cladding is made of SiC (silicon carbide) material, and compared with the traditional Zr cladding (zinc cladding), the cladding has the advantages that the heat generated by the reaction with water is greatly reducedThe peak temperature of the cladding after the water loss accident is greatly reduced due to the low temperature. The ATF fuel assembly B thus has good fault tolerance.

In some embodiments, the ATF fuel assembly B is placed at a lower location in the pressure vessel 11 than in conventional power plants to ensure that the core is submerged in water faster after a loss of water accident, effectively reducing the peak cladding temperature after the accident.

The passive safety system A in some embodiments of the present utility model may be operated by the following steps:

s1: after the loss of coolant accident, as the coolant flows out from the break, the primary side pressure continuously drops, the voltage stabilizer 16 detects abnormal working conditions and generates a low pressure signal to trigger the actions of reactor shutdown, turbine shutdown, main water supply isolation and the like;

s2: the low pressure signal of the pressure regulator 16 triggers an arming signal that triggers the opening of the automatic pressure relief valve 4 to relieve the pressure in the primary circuit; when the pressure of the primary circuit drops to a certain degree, the safety injection system 2 starts to inject water into the reactor coolant system 1;

s3: the safety injection signal triggers the opening of the isolation valve 36 to conduct a water vapor circulation loop in the secondary side waste heat discharging system 3, and the water vapor circulation loop is matched with a coolant circulation loop in the reactor coolant system 1 to form a circulation process of absorbing heat and releasing heat;

s4: when the water level of the refueling water tank 21 drops to a low water level setting value, the second blast valve 2421 on the second injection line 242 is opened, and the pit 21 collects the coolant and condensed reflux water in the containment vessel 5 and injects the coolant and condensed reflux water into the pressure vessel 11 through the pit screen to achieve a long-term cooling effect on the reactor core.

Further, the S2 step may include the following steps in some embodiments:

s21: the safety injection signal triggers the opening of the first-stage pressure relief valve 41 and the electric valve 432, and the first-stage pressure relief valve 41 sprays the high temperature water and the water vapor of the first circuit into the refueling water tank 21 through the first pressure relief pipeline 43 and the sprayer 431;

s22: a first burst valve 2413 on the first water injection line 241 is opened;

s23: after the first-stage pressure relief valve 41 is opened and delayed for a certain time, the second-stage pressure relief valve 42 is opened, and the high-temperature water and the water vapor of the first circuit are sprayed into the inner space of the containment vessel 5 through the second pressure relief pipeline 44, and the pressure of the primary side continuously drops;

s24: when the pressure at the injection point 111 is lower than the gravity head of the water in the refueling water tank 21, the water in the refueling water tank 21 begins to flow automatically into the reactor core within the pressure vessel 11.

Specifically, before step S2, the method further includes:

s20: at the early stage of a water loss accident of a small-sized breach, the safety injection signal triggers the opening of the electric valve 2431 on the third injection line 243, and water in the long-term aging water tank 23 enters the pressure vessel 11 for a long time at a small flow rate, so as to prevent the core from being dry and damaged, and avoid excessive safety injection from flowing from the breach to the bypass of the containment vessel 5 to cause waste.

Further, the step S3 may include the following steps in some embodiments:

s31: the water in the pressure vessel 11 absorbs heat energy generated by nuclear fission in the reactor core to become water at high temperature and high pressure, and then enters the U-shaped pipe of the steam generator 12 along the hot pipe section 13 to transfer the heat to the water outside the U-shaped pipe, the water in the U-shaped pipe releases heat to reduce the temperature, and the water outside the U-shaped pipe absorbs heat to become water vapor;

s32: the water vapor outside the U-shaped pipe of the steam generator 12 enters the heat exchanger 33 through the steam pipeline 121 and the inlet channel 31, the heat exchanger 33 transfers the heat of the water vapor to the cooling water tank 34 and the atmosphere, the water vapor in the heat exchanger 33 is cooled into condensed water, and flows back to the outside of the U-shaped pipe of the steam generator 12 through the outlet channel 32 and the water supply pipeline 122 and is reheated into the water vapor;

s33: the water injected into the outlet channel 32 by the water supplementing tank 33 is converged with the condensed water phase in the heat exchanger 33, and automatically flows into the steam generator 12 by utilizing the height difference so as to increase the water quantity in the loop and accelerate the establishment of water vapor circulation;

s34: the water in the U-shaped pipe of the steam generator 12 is cooled in step S31 and is pushed back into the reactor core in the pressure vessel 11 by the main pump 15 through the cold pipe section 14 for reheating.

In some embodiments, the reactor coolant system 1 is provided with two trains, i.e. with a pair of steam generators 12, to form two coolant circulation loops. The safety injection system 2 is provided with a pair of injection lines 24, the pair of injection lines 24 being connected in common to one of the refueling water tanks 21 and one of the pit 22, and to two of the long-term safety injection tanks 23, respectively. The secondary side waste heat discharging system 3 is provided with two series so as to form two water vapor circulation loops, and the two water vapor circulation loops correspond to the two coolant circulation loops respectively; in either series of water vapor circulation circuits, a pair of parallel makeup tanks 35 are provided. The automatic pressure relief valve 4 is provided with two series, specifically, a pair of first pressure relief lines 43 are commonly connected to one of the charge water tanks 21 and one of the pressure regulators 16, and a pair of first-stage pressure relief valves 41 are provided on the pair of first pressure relief lines 43, respectively; a pair of second pressure relief lines 44 are connected to the pair of heat pipe sections 13, respectively, and a pair of parallel second stage pressure relief valves 42 are provided on either second pressure relief line 44.

It will be appreciated that the series of reactor coolant systems 1 are arranged to ensure the circulation effect of the coolant, the series of injection systems 2 are arranged to ensure the injection effect, the series of secondary side waste heat removal systems 3 are arranged to ensure the heat rejection effect, and the series of automatic pressure relief valves 4 are arranged to ensure the pressure relief effect, the arrangement of the series being not limited to the number and arrangement illustrated, as long as the same or similar functions can be achieved.

It is to be understood that the above examples only represent preferred embodiments of the present utility model, which are described in more detail and are not to be construed as limiting the scope of the utility model; it should be noted that, for a person skilled in the art, the above technical features can be freely combined, and several variations and modifications can be made without departing from the scope of the utility model; therefore, all changes and modifications that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims (10)

1. An passive safety system, comprising:

reactor coolant system (1) comprising a pressure vessel (11), a steam generator (12), a hot pipe section (13) and a cold pipe section (14), the inlet and outlet ends of the steam generator (12) being connected to the pressure vessel (11) via the hot pipe section (13) and the cold pipe section (14), respectively, to form a coolant circulation loop; and

safety injection system (2), including long-term ageing safety injection case (23), reload water tank (21), pit (22) and injection line (24), be provided with safety injection point (111) on pressure vessel (11), long-term ageing safety injection case (23) reload water tank (21) with pit (22) pass through injection line (24) connect in safety injection point (111), with coolant injection pressure vessel (11).

2. Passive safety system according to claim 1, characterized in that the water level of the refueling water tank (21) and the water level of the pit (22) are higher than the plane of the safety point (111).

3. Passive safety system according to claim 1, characterized in that said injection line (24) comprises a first injection line (241), both ends of said first injection line (241) being connected to said safety point (111) and to said refueling water tank (21), respectively; a first branch point (2411) and a second branch point (2412) are arranged on the first injection pipeline (241), and the distance from the first branch point (2411) to the safety point (111) is greater than the distance from the second branch point (2412) to the safety point (111); a first explosion valve (2413) and a first check valve (2414) which are connected in series are arranged between the first branch point (2411) and the second branch point (2412).

4. A passive safety system according to claim 3, characterized in that the injection line (24) comprises a second injection line (242), both ends of the second injection line (242) being connected to the pit (22) and the first branch point (2411), respectively; the second injection pipeline (242) is provided with a second explosion valve (2421) and a second check valve (2422) which are connected in series.

5. A passive safety system according to claim 3, characterized in that the injection line (24) comprises a third injection line (243), the ends of the third injection line (243) being connected to the long-term safety injection tank (23) and the second fulcrum (2412), respectively; the third injection pipeline (243) is provided with an electric valve (2431) and a third check valve (2432) which are connected in series; the water pressure in the long-time-effect safety injection box (23) is larger than the pressure of the safety injection point (111).

6. The passive safety system according to claim 1, characterized in that the passive safety system (a) further comprises a secondary side waste heat removal system (3), the secondary side waste heat removal system (3) comprising a heat exchanger (33), a cooling water tank (34), an inlet channel (31) and an outlet channel (32), the steam generator (12) further comprising a steam line (121) and a water supply line (122), the steam generator (12) being connected to the inlet channel (31) and the outlet channel (32) by the steam line (121) and the water supply line (122), respectively; the heat exchanger (33) is arranged in the cooling water tank (34), an inlet end and an outlet end of the heat exchanger (33) are respectively connected with the inlet channel (31) and the outlet channel (32), the plane of the outlet end is higher than that of one end of the water supply pipeline (122) connected with the steam generator (12), and the inlet end is higher than or flush with the outlet end so as to form a passive water vapor circulation loop.

7. The passive safety system according to claim 6, wherein the secondary side residual heat removal system (3) further comprises a plurality of water replenishment tanks (35), the water replenishment tanks (35) being arranged in parallel with the heat exchanger (33), the water replenishment tanks (35) having inlet ends higher than outlet ends, the inlet ends being connected to the inlet channels (31), the outlet ends being connected to the outlet channels (32).

8. The passive safety system according to claim 7, wherein the inlet end of the water replenishment tank (35) is provided with a diffuser (351), the diffuser (351) is provided with a plurality of small holes, and water vapor in the inlet channel (31) enters the water replenishment tank (35) through the diffuser (351) to reduce the rate of water vapor entering the water replenishment tank (35).

9. The passive safety system according to claim 1, wherein the reactor coolant system (1) further comprises a pressure stabilizer (16), the passive safety system (a) further comprising an automatic pressure relief valve (4) and a containment vessel (5), the automatic pressure relief valve (4) comprising a first stage pressure relief valve (41), a second stage pressure relief valve (42), a first pressure relief line (43) and a second pressure relief line (44); the pressure stabilizer (16) is connected to the hot pipe section (13), two ends of the first pressure relief pipeline (43) are respectively connected to the pressure stabilizer (16) and the reloading water tank (21), a sprayer (431) is arranged at one end connected with the reloading water tank (21), and the sprayer (431) is immersed in water of the reloading water tank (21); both ends of the second pressure relief pipeline (44) are respectively connected with the inner spaces of the hot pipe section (13) and the containment vessel (5); the first stage pressure relief valve (41) is disposed on the first pressure relief line (43), and the second stage pressure relief valve (42) is disposed on the second pressure relief line (44).

10. An ATF fuel based reactor comprising an ATF fuel assembly (B) and a passive safety system (a) according to any of claims 1 to 9, the ATF fuel assembly (B) being arranged inside the pressure vessel (11) and the fuel rods in the ATF fuel assembly (B) comprising pellets and cladding, the cladding being a SiC cladding made of SiC material.