CN210956182U - Safe injection system and nuclear power system - Google Patents

Abstract

The embodiment of the utility model provides a safe injection system and nuclear power system relates to nuclear power technical field; the safety injection system is applied to a nuclear power system, the nuclear power system comprises a primary loop and a secondary loop, the primary loop comprises a reactor pressure vessel RPV and a loop structure connected to the RPV, the secondary loop comprises a steam pipeline, and the loop structure and the steam pipeline are both connected to a steam generator; the safety injection system comprises: a pressure vessel connected to the RPV directly injects into a DVI line; a safety injection pump installed on the DVI pipeline; and a relief valve mounted on the steam line. The embodiment of the utility model provides a safe injection system has reduced the demand to the ann notes subsystem of different injection pressure, and then has reduced the manufacturing cost of whole safe injection system.

Description

Safe injection system and nuclear power system

Technical Field

The utility model relates to a nuclear power technology field especially relates to a safe injection system and nuclear power system.

Background

The nuclear power system of the pressurized water reactor nuclear power plant generally comprises a primary loop and a secondary loop, wherein a flowing medium in the primary loop can absorb heat of a reactor core and transfer the heat to the flowing medium in the secondary loop to generate steam, and the temperature of the reactor core is controlled. In order to ensure the safety of the reactor core, in the design of the nuclear power system, the working conditions that may occur, such as Loss of Coolant Accident (LOCA) caused by the breakage of the primary pipeline, and primary supercooling Accident (SLB) caused by the breakage of the Steam pipeline, etc., are generally considered. In order to deal with the accident condition, a Safety Injection System (Safety Injection System) is usually provided for the reactor.

The safety injection system usually needs to be put into use when the pressure in a primary circuit is reduced to a specific value, and in practical application, the pressure reduction value or the pressure reduction speed of the primary circuit caused by different accident conditions are not consistent.

SUMMERY OF THE UTILITY MODEL

An embodiment of the utility model provides a safe injection system and nuclear power system to solve current pressurized water reactor nuclear power plant nuclear power system and need set up a plurality of different injection pressure's ann notes subsystem simultaneously, and then lead to the higher problem of manufacturing cost of whole ann notes system.

In order to solve the technical problem, the utility model discloses a realize like this:

the embodiment of the utility model provides a safe injection system is applied to nuclear power system, nuclear power system includes one loop and two return circuits, one loop includes reactor pressure vessel RPV and is connected to the loop structure of RPV, two return circuits include the steam conduit, the loop structure with the steam conduit all is connected to steam generator;

the safety injection system comprises:

a pressure vessel connected to the RPV directly injects into a DVI line;

a safety injection pump installed on the DVI pipeline; and the number of the first and second groups,

a relief valve mounted on the steam line.

Optionally, the safety injection system further comprises a safety injection tank ACC, the ACC being connected to the DVI line.

Optionally, the safety injection system further comprises a suction line and a refueling water tank;

the DVI pipelines are arranged in parallel and communicated to the reloading water tank through the suction pipeline;

and each DVI pipeline is provided with the safety injection pump.

Optionally, the number of suction lines is plural.

Optionally, the safety injection pump is a medium pressure safety injection pump.

Optionally, the release valve is a spring loaded safety valve.

The embodiment of the utility model also provides a nuclear power system, including a primary circuit, a secondary circuit and the above-mentioned safe injection system;

the primary circuit comprises an RPV and a loop structure connected to the RPV, the secondary circuit comprises a steam pipe, and the loop structure and the steam pipe are both connected to a steam generator;

the DVI line is connected to the RPV, and the relief valve is mounted on the vapor conduit.

Optionally, a plurality of said loop structures are connected to said RPV;

the loop structure comprises a heat pipe section, a cold pipe section and a main pump;

the first interface and the second interface of the steam generator are respectively connected with the RPV through a heat pipe section and a cold pipe section, and the main pump is installed on the cold pipe section.

In the embodiment of the utility model, the safe injection system adopts DVI technique on the one hand, has reduced the flow requirement to the safety injection pump, and on the other hand sets up the relief valve on two return circuits steam conduit, reduces the pressure requirement to the safety injection pump through releasing steam and cooling decompression to one return circuit; therefore, the safety injection subsystems of the same type can adapt to more types of accident conditions, the requirements on the safety injection subsystems with different injection pressures are reduced, and the manufacturing cost of the whole safety injection system is further reduced. In addition, the DVI pipeline is adopted to directly inject into a loop, and a safety injection system is not influenced by a loop accident, so that the usability and the reliability are higher.

Drawings

Fig. 1 is a schematic structural diagram of a safety injection system according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a safety injection system according to an embodiment of the present invention in a preferred embodiment;

FIG. 3 is a flow chart of a safe injection method for use in a nuclear power system;

FIG. 4 is a flow chart of the operation of the relief valve and the safety injection pump.

The figures show that: DVI line 110, suction line 111, safety injection tank 120, safety injection pump 130, relief valve 140, first isolation valve 151, second isolation valve 152, check valve 153, reactor pressure vessel 210, loop structure 220, hot pipe section 221, cold pipe section 222, main pump 223, steam conduit 300, steam generator 400, refueling water tank 500, containment vessel 600.

Detailed Description

In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following detailed description will be given with reference to the accompanying drawings and specific embodiments. In the following description, specific details are provided, such as specific configurations and components, merely to facilitate a thorough understanding of embodiments of the invention. Thus, it will be apparent to those skilled in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

The embodiment of the utility model provides a safe injection system is applied to nuclear power system, as shown in fig. 1, nuclear power system includes one loop and two return circuits, one loop includes Reactor Pressure Vessel (RPV) 210 and is connected to RPV's loop structure 220, two return circuits include steam conduit 300, loop structure 220 with steam conduit 300 all is connected to steam generator 400;

the safety injection system comprises: a Direct Vessel Injection (DVI) line 110 connected to the RPV; a safety injection pump 130 installed on the DVI line 110; and a relief valve 140 installed on the steam pipe 300.

The safety injection system in the prior art mostly injects water from a main loop pipeline, and under the working condition that a large break LOCA accident occurs in the main loop pipeline, the water injected into the main break pipeline is completely lost, so that one column of the safety injection system is completely invalid, and the requirement on the number of the configured columns of the safety injection system and the flow requirement on a safety injection pump on a perfect main pipeline are improved. In the present embodiment, DVI technology is used, i.e., the safety injection pump 130 can directly inject water into a loop from the DVI line 110 independent of the main pipeline of the loop. Even if a large-break LOCA accident of the main pipeline of the primary circuit occurs, the safety injection subsystem cannot be failed, and the requirements on the number of columns of the safety injection subsystem and the flow of the safety injection pump 130 are reduced.

Under the LOCA accident condition of various sizes of crevasses, cooling water (generally boron-containing water) can be injected into a loop through the safety injection pump 130, the water level of the reactor core is technically restored and maintained, the effective cooling of the reactor core is ensured, and the overheating damage and the radioactive release of the reactor core are prevented. Under the working condition of a primary circuit supercooling accident such as an SLB accident, boron-containing water can be injected into the primary circuit through the safety injection pump 130 to compensate the positive reactivity introduced by primary circuit cooling, so that the reactor core is ensured to be in a subcritical state and to keep sufficient shutdown depth, and the safety of the reactor core is ensured.

The present embodiment provides the safety injection system in which the relief valve 140 is installed on the steam pipe 300. Under normal conditions, relief valve 140 is closed and steam in steam line 300 is used to drive the steam turbine. When the pressure relief valve 140 is opened under the accident condition, steam in the two loops is released to the external environment at a large flow rate, and then the temperature and the pressure of the loop can be rapidly reduced. Under the LOCA accident condition with a medium or small break, or the supercooling condition of the primary circuit such as the SLB accident condition, the pressure drop rate in the primary circuit is slow, or the pressure cannot drop to the threshold value for triggering the operation of the safety injection subsystem, the release valve 140 can be opened to rapidly cool and reduce the pressure of the primary circuit, so as to trigger the operation of the safety injection subsystem.

In the embodiment, on one hand, the safety injection system adopts DVI technology to reduce the flow requirement on the safety injection pump, and on the other hand, the release valve is arranged on the steam pipeline of the two loops to reduce the temperature and pressure of the loop by releasing steam, so as to reduce the pressure requirement on the safety injection pump; therefore, the safety injection subsystems of the same type can adapt to more types of accident conditions, the requirements on the safety injection subsystems with different injection pressures are reduced, and the manufacturing cost of the whole safety injection system is further reduced. In addition, the DVI pipeline is adopted to directly inject into a loop, and a safety injection system is not influenced by a loop accident, so that the usability and the reliability are higher.

Optionally, the above safety injection system further includes an Accumulator (ACC) 120, which is connected to the DVI pipeline 110.

The ACC may be a container storing boron-containing water covered with nitrogen, and is generally automatically opened when the pressure in the primary circuit decreases to a certain value (for example, 5 MPa). ACC is passive equipment, and its operation does not rely on external power, can effectively guarantee boron-containing water and pour into reliability.

Optionally, the ACC is connected to the DVI line 110 at a location between the safety pump 130 and the RPV.

Optionally, the safety injection system further comprises a suction line 111 and a refueling water tank 500; a plurality of DVI pipelines 110 are arranged in parallel and communicated to the refueling water tank 500 through the suction pipeline 111; the safety injection pump 130 is installed on each DVI pipeline 110.

The diameter of the DVI line 110 to which the RPV is connected is typically much smaller than the diameter of the primary loop main pipe of the prior art, e.g., for DVI line 110, the size specification may be set to DN150, whereas the size specification of the primary loop main pipe of the prior art may typically reach DN 760. In view of the influence of the size of the opening on the RPV strength, compared with the existing primary loop main pipe structure, more DVI pipelines 110 can be arranged to communicate with the RPV in the embodiment, and a safety injection pump 130 can be installed on each DVI pipeline 110. The increase of the number of the safety injection pumps 130 can effectively improve the injection efficiency of the cooling water and improve the reliability of a safety injection system.

Optionally, the number of the suction lines 111 is plural.

The above-mentioned plurality of suction lines 111 are connected to a refueling water tank 500. Each suction line 111, the corresponding DVI line 110, the corresponding safety injection pump 130, and the like can be used as a row, and a plurality of suction lines 111 are arranged, that is, a plurality of rows of the above-mentioned structures are correspondingly arranged, so that the single failure design principle is mainly considered, that is, when one row of the safety injection system fails, other rows still exist and can operate independently. Of course, the provision of a plurality of suction lines 111 can also improve the injection efficiency of the cooling water.

Optionally, the safety injection pump 130 is a medium pressure safety injection pump.

The operating pressure range of the medium-pressure Safety Injection pump is generally 0.1-8.0 MPa, and the medium-pressure Safety Injection pump and the corresponding DVI pipeline 110 and the like together form a medium-pressure Safety Injection (MHSI) subsystem. Under the normal operating condition of nuclear power plant, the pressure of a circuit is about 15.5MPa, and when accident conditions such as LOCA, circuit subcooling appear, the pressure can reduce in a circuit, when pressure drops to a definite value, will trigger safe injection signal, when pressure continues to drop to the operating pressure of medium pressure safety pump, for example 8.0MPa, the MHSI subsystem begins to pour into the cooling water into a circuit. In practical application, when the pressure in the primary circuit is continuously reduced to 5.0MPa, cooling water can be injected into the primary circuit through the ACC.

In this embodiment, because relief valve 140 can carry out rapid cooling depressurization to a return circuit, each row of safe injection system all can set up a plurality of safety injection pumps 130 simultaneously, effectively guarantees water injection efficiency, consequently, all safety injection pumps 130 all can set to middling pressure safety injection pumps to avoided setting up the safety injection subsystem of many different injection pressures, effectively reduced whole safe injection system's design and manufacturing cost.

Of course, in some possible embodiments, the MHSI subsystem may be replaced by a High Head Safety Injection (HHSI) subsystem or a Low pressure Safety Injection (LHSI) subsystem. In contrast, the HHSI subsystem can operate at a higher value for the loop pressure, but on the one hand, in the HHSI subsystem, the flow rate of the high-pressure safety injection pump is smaller and the water injection efficiency is lower; on the other hand, in response to a Steam Generator Tube Rupture (SGTR) event, the higher injection pressure of the HHSI subsystem causes more coolant to leak from one circuit to the second circuit, causing the Steam Generator 400 to flood and release more radioactivity into the ambient environment. For the LHSI subsystem, it is necessary to operate when the pressure in the circuit drops to a low value, for example, for a common low pressure safety injection pump, the operating pressure is typically below 2 MPa. When a large-break LOCA accident occurs, the pressure drop amplitude of a primary circuit is large, and the low-pressure safety injection pump can efficiently inject water; however, when the LOCA is a small and medium break or other accident conditions which do not cause the primary circuit to be greatly reduced in pressure, the primary circuit needs to be reduced in pressure in an auxiliary mode; taking the release valve 140 in the above embodiment as an example, it takes a long time to trigger the LHSI subsystem to operate, and the action is not timely enough, which is likely to cause a more serious safety problem; and for accident conditions where the circuit pressure reduction is not significant, it is difficult to reduce the pressure in the circuit to the operating pressure of the LHSI subsystem via the relief valve 140.

Optionally, the release valve 140 is a spring-loaded relief valve.

Based on the above embodiment, when a small break LOCA or the like occurs to make the pressure of the primary circuit difficult to drop to an accident condition of triggering the operation pressure of the safety injection subsystem, the pressure of the primary circuit needs to be reduced. In the prior art, the pressure of a primary circuit is usually relieved by sequentially opening valves of a multi-stage automatic pressure relief system, and the damage degree of a pressure boundary of the primary circuit is artificially increased, so that a large amount of reactor coolant is lost; a large amount of coolant with high radioactivity which flows out from a crevasse and an automatic pressure relief system valve enters a containment vessel to cause serious pollution of the containment vessel, so that the recovery after a nuclear power plant accident is extremely difficult. Meanwhile, the four-stage pressure relief valve of the automatic pressure relief system generally adopts a blast valve, and the failure probability is high.

In this embodiment, on one hand, the spring-loaded safety valve is located on the second loop, and after the spring-loaded safety valve is opened, the water vapor in the second loop is discharged to reduce the temperature and pressure of the first loop, so that the loss of the coolant of the reactor is avoided; on the other hand, spring-loaded safety valves have a higher reliability than burst valves. Of course, the release valve 140 may be another type of pressure relief valve, and may release the steam in the steam pipeline 300. Furthermore, in the above-described embodiment, the relief valve 140 is preferably provided on the main steam line of the two circuits.

As shown in FIGS. 1 and 2, in a preferred embodiment, four DVI lines 110 on the RPV, DVI-A, DVI-B, DVI-C and DVI-D, respectively; each DVI pipeline 110 is provided with one ACC and a corresponding second isolation valve 152 and a corresponding check valve 153, the four ACCs are respectively defined as ACC-A, ACC-B, ACC-C and ACC-D, the ACC can be a boron-containing water storage container covered by nitrogen, and the initial covering pressure of the nitrogen can be about 5.0 MPa; the safety injection pump 130 can be selected as a medium-pressure safety injection pump, and the medium-pressure safety injection pump for injecting water into each DVI pipeline 110 is respectively a medium-pressure safety injection pump A, a medium-pressure safety injection pump B, a medium-pressure safety injection pump C and a medium-pressure safety injection pump D; the DVI pipeline 110 where each medium-pressure safety injection pump is located is provided with a first isolation valve 151. The water intake source of the four medium-pressure safety injection pumps is a refueling water tank 500, and the refueling water tank 500 is a boron-containing water storage tank arranged in the containment 600. The four medium-pressure safety injection pumps are divided into two rows, the medium-pressure safety injection pump A and the medium-pressure safety injection pump B are in one row (row A), share one row of emergency alternating-current power supply and equipment cooling water system, the medium-pressure safety injection pump C and the medium-pressure safety injection pump D are in the other row (row B), and share the other row of emergency alternating-current power supply and equipment cooling water system. When the pressure of the primary loop needs to be reduced, the release valve 140 on the secondary loop steam pipeline 300 is opened, so that the secondary loop steam is released into the external environment at a large flow rate, and the primary loop is rapidly cooled and reduced in pressure.

In the preferred embodiment, the safety injection system comprises a DVI pipeline, a medium-pressure safety injection pump, an ACC and a release valve positioned on a two-loop steam pipeline, the expected safety function can be effectively executed without an HHSI subsystem and an LHSI subsystem, the system design and the process flow are greatly simplified, required equipment is greatly reduced, and the economical efficiency is good. Due to the adoption of the DVI technology, a reactor Core water replenishing Tank (Core Makeup Tank, CMT) possibly used in the prior art is omitted, only two independent lines are needed to be configured to meet the single fault design principle, only two lines are needed to be configured for corresponding support systems such as an emergency alternating current power supply and an equipment cooling water system, the system configuration and the support systems are also greatly simplified, and the economy of the nuclear power plant is further improved.

Of course, alternatively, the number of columns included in the safety injection system may be three or more, and the number is set according to actual needs.

The embodiment of the utility model provides a safe injection system adopts the DVI technique and locates the relief valve structure on two return circuits steam conduit, under the prerequisite of guaranteeing that safe injection system can effectively carry out its anticipated safety function, simplifies safe injection system design, reduces the requirement to its support system, reduces hardware cost and running cost, is guaranteeing effectively to improve economic nature simultaneously of nuclear power plant safety.

The embodiment of the utility model provides a nuclear power system is still provided, as shown in fig. 1, including the primary circuit, two return circuits and the safe injection system as above; the primary circuit comprises an RPV and a loop structure 220 connected to the RPV, the secondary circuit comprises a steam pipe 300, and both the loop structure 220 and the steam pipe 300 are connected to a steam generator 400; the DVI line 110 is connected to the RPV, and the relief valve 140 is installed on the vapor pipe 300.

In the nuclear power system provided by the embodiment, on one hand, the safety injection system adopts DVI technology to reduce the flow requirement on the safety injection pump, and on the other hand, the release valve is arranged on the two-loop steam pipeline to reduce the temperature and pressure of the first loop by releasing steam to reduce the pressure requirement on the safety injection pump; therefore, the safety injection subsystems of the same type can adapt to more types of accident conditions, the requirements on the safety injection subsystems with different injection pressures are reduced, and the manufacturing cost of the whole safety injection system is further reduced. In addition, the DVI pipeline is adopted to directly inject into a loop, and a safety injection system is not influenced by a loop accident, so that the usability and the reliability are higher.

Optionally, a plurality of said loop structures are connected to said RPV; the loop structure 220 includes a hot pipe section 221, a cold pipe section 222, and a main pump 223; the first interface and the second interface of the steam generator are respectively connected with the RPV through a heat pipe section and a cold pipe section, and the main pump is installed on the cold pipe section.

The hot pipe section 221 and the cold pipe section 222 are respectively connected to the RPV, the primary coolant conducts heat generated by the core to the steam generator 400 through the hot pipe section 221, and the cooled primary coolant is pumped back to the RPV through the cold pipe section 222 by the primary pump 223. In this embodiment, the loop structure 220 does not include a safety injection pump, a safety injection tank and other structures for safe injection, and the DIV technology is adopted to replace the existing main pipe technology, so that higher safety is achieved.

The plurality of loop structures 220 are connected in parallel across the RPV. For example, a pressurized water reactor nuclear power plant with about 1000MW of electric power generally has 2 to 3 loop structures 220, and fig. 1 shows a cooling condition of one loop structure 220 and a corresponding two-loop release valve 140 when the two-loop release valve is opened, where SG1 is a Steam Generator (i.e., Steam Generator, SG) provided in the loop structure 220, and HL-1 and CL-1 respectively represent a heat pipe section and a cold pipe section included in the loop structure 220; accordingly, HL-2 and HL-3 represent hot pipe segments in the other loop structures 220, and CL-2 and CL-3 represent cold pipe segments in the other loop structures 220; HL-2 and CL-2 are connected to a steam generator SG2 (not shown), and HL-3 and CL-3 are connected to a steam generator SG3 (not shown).

In practical applications, of course, a corresponding number of loop structures 220 may be selected to match the heat exchange power to the electrical power required by the pressurized water reactor nuclear power plant.

As shown in fig. 3, by further improving on the hardware structure provided by the above-mentioned nuclear power system, the following safety injection method can be applied:

step S10, acquiring a pressure value in the loop;

step S20, when the pressure value in the loop is lower than a first pressure threshold value, generating a safe injection signal;

step S30, when the pressure value in the loop is lower than a second pressure threshold value, controlling the safety injection pump to operate according to the safety injection signal;

wherein the first pressure threshold is greater than the second pressure threshold.

Under the normal operation condition of a nuclear power plant, the pressure of a primary circuit is about 15.5MPa generally, and when the pressure of the primary circuit is reduced to a first pressure threshold value, such as 11.5MPa, due to a crack LOCA or a supercooling accident, a safety injection signal is triggered; for example, for a safety injection system with an MHSI subsystem, when the pressure of a primary circuit is reduced to 8MPa or other set values, according to the safety injection signal, the safety injection pump starts to inject cooling water into the primary circuit to cool the core or ensure that the core is in a subcritical state, thereby ensuring the safety of the nuclear power system. Of course, the first pressure threshold and the second pressure threshold may be adjusted according to actual needs.

Optionally, as shown in fig. 4, in step S30, when the pressure value in the primary circuit is lower than a second pressure threshold, controlling the safety injection pump to operate according to the safety injection signal includes:

step S31, when the pressure value in the circuit is lower than a first pressure threshold value and the duration time of the pressure value not lower than a second pressure threshold value exceeds a time threshold value, controlling the release valve to be opened;

and step S32, when the pressure value in the loop is lower than a second pressure threshold value, controlling the safety injection pump to operate according to the safety injection signal.

Under some accident conditions, such as a medium or small break LOCA or a primary circuit supercooling accident condition caused by an SLB accident, the pressure in the primary circuit may not drop to the pressure triggering the safety injection pump to operate; or the pressure can be reduced to the pressure triggering the operation of the safety injection pump, but the safety injection pump cannot respond in time due to the slow pressure reduction rate. In consideration of the accident condition, when the pressure value in the primary circuit is lower than the first pressure threshold and the duration time not lower than the second pressure threshold exceeds the time threshold, the release valve is controlled to be opened, the primary circuit is rapidly cooled and depressurized through the release of steam in the secondary circuit, the operation of the safety injection pump is triggered, the time of the safety injection system participating in the accident condition treatment is shortened, and the safety and the reliability of the nuclear power system are further improved.

And when the pressure in the loop is reduced to a second pressure threshold value, triggering the safety injection pump to operate so as to improve the injection efficiency of the cooling water.

Optionally, the safety injection method further includes: and controlling the ACC to operate when the pressure value in the circuit is lower than a third pressure threshold value. For example, the third pressure threshold is 5.0 MPa. In practical application, when the pressure in the loop is reduced to a low value, the valve on the pipeline where the ACC is located can be opened, so that the boron-containing water in the ACC is injected into the loop in a passive mode, and the efficiency and the reliability of the safe injection process are improved.

The specific application of the safe injection method in the nuclear power system is as follows:

(1) and (4) responding to LOCA accidents of medium and small crevasses. Under the normal operation condition of a nuclear power plant, the pressure of a primary circuit is about 15.5MPa, under the LOCA accident working condition of a middle and small break, the pressure of the primary circuit is reduced due to the release of the break, when the pressure is reduced to about 13.5MPa, a reactor shutdown signal is triggered, and a control rod is inserted into a reactor core to shut down the reactor. The safety injection signal is triggered when the loop pressure continues to decrease to about 11.5 MPa. But because the size of the break is smaller, the pressure reduction effect on the primary circuit is limited, and the pressure of the primary circuit cannot be reduced to the pressure at which the medium-pressure safety injection pump and the safety injection tank can be put into operation. Therefore, when a safe injection signal appears, a release valve opening signal on the main steam pipeline of the two loops can be triggered, the release valve is automatically opened, steam in the two loops is released from the release valve in a large flow to enter the external environment, and the primary loop is rapidly cooled and depressurized. When the pressure of a primary circuit is reduced to the pressure which can be input by the medium-pressure safety injection pump and the safety injection tank, the MHSI subsystem and the ACC inject cooling water into the primary circuit, the water level of the reactor core is quickly recovered, and the reactor core is ensured to be submerged and cooled.

(2) And the LOCA accident with a large break can be dealt with. Under the LOCA accident condition with a large break, the reactor shutdown is similar to the medium and small LOCA accidents. The large size of the break causes the pressure in the primary circuit to be reduced rapidly, and the pressure in the primary circuit can be reduced to the pressure for the MHSI subsystem and the ACC operation without the need of steam release cooling of the secondary circuit. The MHSI subsystem and the ACC inject cooling water into the primary circuit, the water level of the reactor core of the reactor is quickly recovered, and the reactor core is ensured to be submerged and cooled.

(3) To deal with primary circuit subcooling such as SLB accidents. The SLB accident causes the temperature and pressure of a primary circuit to be reduced, when the pressure of the primary circuit is reduced to about 13.5MPa, a reactor shutdown signal is triggered, and a control rod is inserted into a reactor core to shut down the reactor. But the primary loop will continue to cool, and due to the negative moderator temperature coefficient and doppler temperature coefficient reactivity feedback effect, the reactor core will continue to introduce positive reactivity, with the risk of re-critical core. The continuous cooling of the loop causes the pressure of the loop to continuously reduce to about 11.5MPa to trigger a safe injection signal, but the pressure of the loop cannot reduce to the pressure which can be input by the MHSI subsystem. Therefore, when a safe injection signal appears, a release valve opening signal on the main steam pipeline of the two loops can be triggered, the release valve is automatically opened, steam of the two loops of the intact loop is released from the release valve at a large flow rate to enter the external environment, and the loop is rapidly cooled and depressurized. When the pressure of a primary circuit is reduced to the pressure which can be input by a medium-pressure safety injection pump, the MHSI subsystem injects boron water into the primary circuit to compensate the positive reaction introduced by the cooling of the primary circuit, so that the reactor core is ensured to be in a subcritical state and maintain enough shutdown depth.

The foregoing is directed to the preferred embodiments of the present invention, and it will be understood by those skilled in the art that various changes and modifications may be made without departing from the principles of the invention, and that such changes and modifications are intended to be included within the scope of the invention.

Claims (8)

1. A safe injection system is applied to a nuclear power system and is characterized in that the nuclear power system comprises a primary loop and a secondary loop, wherein the primary loop comprises a Reactor Pressure Vessel (RPV) and a loop structure connected to the RPV, the secondary loop comprises a steam pipeline, and the loop structure and the steam pipeline are both connected to a steam generator;

the safety injection system comprises:

a pressure vessel connected to the RPV directly injects into a DVI line;

a safety injection pump installed on the DVI pipeline; and the number of the first and second groups,

a relief valve mounted on the steam line.

2. The safety injection system of claim 1, further comprising a safety injection tank ACC connected to the DVI line.

3. The safety injection system of claim 1, further comprising a suction line and a refill tank;

the DVI pipelines are arranged in parallel and communicated to the reloading water tank through the suction pipeline;

and each DVI pipeline is provided with the safety injection pump.

4. A safety infusion system according to claim 3, wherein said suction line is plural in number.

5. The safety infusion system of any one of claims 1 to 4, wherein the safety infusion pump is a medium pressure safety infusion pump.

6. The safety injection system of claim 1, wherein the release valve is a spring-loaded safety valve.

7. A nuclear power system comprising a primary circuit, a secondary circuit and a safety injection system as claimed in any one of claims 1 to 6;

the primary circuit comprises an RPV and a loop structure connected to the RPV, the secondary circuit comprises a steam pipe, and the loop structure and the steam pipe are both connected to a steam generator;

the DVI line is connected to the RPV, and the relief valve is mounted on the vapor conduit.

8. The nuclear power system of claim 7 wherein a plurality of the loop structures are connected to the RPV;

the loop structure comprises a heat pipe section, a cold pipe section and a main pump;

the first interface and the second interface of the steam generator are respectively connected with the RPV through a heat pipe section and a cold pipe section, and the main pump is installed on the cold pipe section.

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