Patent Description:
The main function of the special safety system is to mitigate the consequences of accidents. For example, in case of primary circuit water loss, secondary circuit steam/feed water pipeline rupture, steam generator heat transfer tube rupture, power loss and low pressure reactor melting, the corresponding special safety system is activated to limit and mitigate the consequences of the accident and ensure the nuclear safety function:.

The third generation nuclear power unit represented by AP1000 usually adopts the structure of steel containment and containment top water tank, as well as the secondary-side passive cooling system. Through the steel wall containment or heat exchanger, the passive cooling of the containment atmosphere and the secondary loop can be realized. However, it is difficult to apply the design to the second generation nuclear power units, and the transformation is difficult and the cost is high.

The containment cooling system is provided in the AP1000, and its main function is to remove the containment heat and reduce the containment pressure and temperature under the design basis accidents that lead to the increase of containment pressure and temperature.

The new containment high-level water tank (containing about <NUM> tons of water) and the passive Containment Heat Removal System (EHR) immersed in the water tank, the secondary-side Passive Residual Heat Removal System (PRS), the reactor cavity water injection cooling system and other passive safety systems are added to HPR10001 of CGN. These systems transfer energy from the steam generator <NUM> or containment atmosphere to the high-level water tank through closed circuit pipelines. However, a large number of pipelines in these systems are located at the high elevation of the containment, and the mechanical analysis, pipeline anti-swing and embedded parts design are complex, which brings a lot of trouble to the construction and equipment installation.

The HPR1000 of CGN is also newly added with a high-level containment water tank (containing <NUM>,<NUM> tons of water) and a secondary-side Passive Residual Heat Removal System (PRS) immersed in the water tank. And without any passive containment heat removal system. The functionality of this section is realized by two pumps and heat exchangers of the containment heat removal system (EHR). In the pit water injection function, the active water injection is realized by the EHR system water pump, and the passive water injection is realized by the pit water injection tank in the containment.

In the related art, such as a Passive special safety system for Nuclear Power Plants (Application No. is <CIT>. ) The invention discloses a special passive safety system for a nuclear power plant, which comprises a secondary-side passive residual heat removal heat exchanger, a steam condensate tank, a passive reactor cavity water injection system, a passive high-pressure reactor core water replenishing tank and related valves and pipelines. When a design basis accident or an accident exceeding the design basis occurs in the nuclear power station, a series of passive and active safety facilities are put into operation step by step to effectively cool the primary loop and the reactor core of the reactor in time and rapidly, so that the nuclear power station can smoothly enter a safe cold shutdown state, the serious accident consequences of the reactor are inhibited or relieved, the accident hazard are reduced, and the safety of the nuclear power station is improved. A Passive Engineered Safety Device for a Nuclear Power Plant (Application No. is <CIT>. ) This invention provides a passive engineered safety device for a nuclear power plant, comprising: discharge pipelines; a heat exchanger; a diffuser; a quick relief valve; and an injection manifold. The passive special safety facility for the nuclear power station provided by the invention is different from the traditional special safety facility for the nuclear power station, the connecting pipelines of the passive special safety facility are intensively arranged on the pressure vessel, and the passive special safety facility is used for directly cooling and injecting water into the reactor core, so that the natural circulation capacity is increased, and a safety protection system is safer and more reliable.

Although the related technologies listed above can effectively cool the primary loop and core of the reactor in a timely and rapid manner, enable the nuclear power plant to enter a safe cold shutdown state smoothly, inhibit or mitigate the consequences of serious reactor accidents, reduce accident hazard and improve the safety of the nuclear power plant. But in case of failure of the passive containment cooling system, the secondary-side cooling system, the safety injection system and/or the containment spraying system, the effective cooling of the reactor primary circuit and core cannot be continued.

The technical problem to be solved by the present invention is to provide an improved passive special safety system and a water supply system for a nuclear power plant. The problem underlying the present application is solved by a water supply system for passive special safety system of a nuclear power plant having the features of claim <NUM>, as well as by a passive special safety system for a nuclear power plant having the features of claim <NUM>.

A water supply system according to the invention is defined in claim <NUM>.

Brief description of that drawing the invention will now be further described by way of example with reference to the accompany drawings in which:
<FIG> is a schematic block diagram of a passive special safety system for a nuclear power plant in accordance to an embodiment of the present invention.

For a clearer understanding of the technical features, objects, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

<FIG> illustrates a preferred embodiment of a passive special safety system for a nuclear power plant of the present invention. After the accident of the reactor, when the active special safety system fails, the passive special safety system of the nuclear power plant is used as the standby passive special safety system to establish the core cooling capacity, ensure the radioactive containment, limit and mitigate the consequences of the accident, and ensure the nuclear safety. At the same time, it can replace the high-level water tank of the containment of the third-generation nuclear power unit, reduce the load of the containment and improve the safety of the containment.

As shown in <FIG>, in some embodiments, the passive special safety system of the nuclear power plant may include a containment <NUM>, a reactor core assembly <NUM>, a passive containment cooling system <NUM>, a secondary-side passive cooling system <NUM>, a steam generator <NUM>, a spraying system <NUM>, and a water supply system <NUM>. The containment <NUM> may be used to house a reactor core assembly <NUM>, a passive containment cooling system <NUM>, and a steam generator <NUM>. The reactor core assembly <NUM> may be disposed in the containment <NUM> and may be connected to the steam generator <NUM>. The passive containment cooling system <NUM> may be disposed in the upper space of the containment <NUM> and opposite to the reactor core assembly <NUM> for cooling the reactor core assembly <NUM>. The secondary-side passive cooling system <NUM> may be disposed at an upper portion of the containment <NUM>, and may be connected to the steam generator <NUM> and the passive containment cooling system <NUM>. In some embodiments, the secondary-side passive cooling system <NUM> can be divided into two groups, wherein one group can be connected with the steam generator <NUM>, and the other group can be connected with the passive containment cooling system <NUM>. In some embodiments, the steam generator <NUM> may be coupled to the reactor core assembly <NUM> and the steam generator <NUM>. In some embodiments, the spraying system <NUM> may be disposed in the upper space of the containment <NUM>, may be disposed opposite to the reactor core assembly <NUM>, and may cool the reactor core assembly <NUM> by spraying. In some embodiments, the water supply system may be connected to and supply water to the passive containment cooling system <NUM>, the secondary-side passive cooling system <NUM>, the spraying system <NUM>, and the reactor core assembly <NUM>. Of course, it is understood that, in other embodiments, it may only be connected to the passive containment cooling system <NUM>, the secondary-side passive cooling system <NUM>, the spraying system <NUM>, or the reactor core assembly <NUM>.

Further, in some embodiments, a reactor core assembly <NUM> may be disposed at a lower portion of the containment <NUM>, and may include a pressure vessel <NUM>, which may be a nuclear fuel reaction vessel. The pressure vessel <NUM> may be placed in the reactor pit and the coolant inlet of the pressure vessel <NUM> may be connected to a low pressure safety injection system <NUM> and the reactor pit may be connected to a reactor pit water injection system <NUM>. The coolant outlet of the pressure vessel <NUM> may be connected to a steam generator <NUM>.

Further, in some embodiments, the passive containment cooling system <NUM> may include a helical coiled tube disposed in the dome region of the containment <NUM> and may be coupled to the secondary-side passive cooling system <NUM>, specifically, in some embodiments, the helical coiled tube may be connected to the heat exchanger <NUM> of the secondary-side passive cooling system <NUM>.

Further, in some embodiments, the secondary-side passive cooling system <NUM> may include a water tank <NUM> and a heat exchanger <NUM> disposed in the water tank <NUM>. The water tank <NUM> may be connected to the water supply system <NUM>, and the water supply system <NUM> may supply water to the water tank <NUM>. The heat exchanger <NUM> may be disposed in the water tank <NUM> to exchange heat with the water in the water tank <NUM>. In some embodiments, one set of the heat exchangers <NUM> of the secondary-side passive cooling system <NUM> may have an outlet connected to an inlet of the passive containment cooling system <NUM>, an inlet connected to an outlet of the passive containment cooling system <NUM>, a cooled body of water delivered to the passive containment cooling system, the other group of the heat exchanger <NUM> of the secondary-side passive cooling system <NUM> receives the high-temperature water formed after the passive containment cooling system <NUM> cools the containment <NUM>, the inlet end of the heat exchanger <NUM> can be connected with the steam outlet of the steam generator <NUM>, and the outlet end of the heat exchanger <NUM> can be connected with the water supply system <NUM> to cool the steam output by the steam generator <NUM>. And convey that cooled water to the water supply system <NUM> for recycling.

Further, in some embodiments, the number of the steam generators <NUM> may be three. Of course, it is understood that in other embodiments, the number of the steam generators <NUM> may not be limited to three. The steam outlet pipelines <NUM> of the three steam generators <NUM> may be connected to each other. Each steam generator <NUM> may include a housing and a heat exchange tube provided in the housing. The inlet end of the housing may be connected to the water supply <NUM>, which may deliver water to the inlet end of the housing. The steam outlet end of the housing may be connected to a steam outlet pipeline <NUM>, and the steam outlet pipeline <NUM> may be connected to a steam output pipeline <NUM> to deliver steam to the steam turbine to drive the steam turbine to work. In some embodiments, the steam outlet pipeline <NUM> may be provided with a pressure discharge pipeline <NUM>, and the pressure discharge pipeline <NUM> may be provided with an atmosphere discharge valve <NUM>. The atmosphere discharge valve <NUM> is opened to discharge pressure to the steam outlet pipeline <NUM> in time. The steam output pipeline <NUM> can be connected to one end of the steam-pressurizing main pipeline <NUM>, and the other end of the steam-pressurizing main pipeline <NUM> can be connected to the water supply system <NUM>, so as to transmit the steam to the water supply system <NUM> to pressurize the water supply system <NUM>, so that the water supply system <NUM> outputs the water. In some embodiments, the steam-pressurizing main pipeline <NUM> may be provided with a main steam isolation valve <NUM> that opens to deliver steam to the water supply <NUM>.

Further, in some embodiments, the spraying system <NUM> may be disposed below the passive containment cooling system <NUM>, may be located above the reactor core assembly <NUM>, and may spray the reactor core assembly <NUM> to cool the reactor core assembly <NUM>. In some embodiments, the spraying system <NUM> may be connected to the water supply <NUM> and may be supplied with water from the water supply <NUM>.

According to the invention the water supply system <NUM> includes at least one steam-pressurizing water tank <NUM>, at least one steam-pressurizing pipeline <NUM>, at least one water replenishment pipeline <NUM>, and a drain pipeline <NUM>. The steam-pressurizing water tank <NUM> is connected to the steam generated by the steam generator <NUM>, and is pressurized by the steam to drive the water in the steam-pressurizing water tank <NUM> to be delivered out. The steam-pressurizing pipeline <NUM> is connected to the steam-pressurizing water tank <NUM> and the steam generator <NUM>, specifically, in some embodiments, each steam-pressurizing pipeline <NUM> may be connected to the steam-pressurizing main pipeline <NUM> and a pressurized steam inlet of the steam-pressurizing water tank <NUM>. A water replenishment pipeline <NUM> is connected to a steam-pressurizing water tank <NUM> and an external water source to supply water to the steam-pressurizing water tank <NUM> in time. According to the invention, the drain pipeline <NUM> is connected to all the steam-pressurizing water tanks <NUM>, and may be connected to the passive containment cooling system <NUM>, the secondary-side passive cooling system <NUM>, the spraying system <NUM>, and the reactor core assembly <NUM>. Of course, it is understood that in other embodiments, the drain pipelines <NUM> may be connected only to the passive containment cooling system <NUM>, the secondary-side passive cooling system <NUM>, the spraying system <NUM>, or the reactor core assembly <NUM>.

Further, according to the invention, a steam-pressurizing water tank <NUM> includes a tank body <NUM> and a plurality of partition plates <NUM>. The tank body <NUM> is a horizontal tank, and the plurality of partition plates <NUM> is disposed in the tank body <NUM> at intervals along the length direction of the tank body <NUM>, and form a predetermined included angle with the bottom wall of the tank body <NUM>, so as to guide water and divide the space in the tank body <NUM> into a plurality of water chambers <NUM>. Specifically, in some embodiments, the tank body <NUM> may include a bottom wall and a top wall disposed opposite the bottom wall. A plurality of partition plates <NUM> are disposed on the bottom wall, and a plurality of partition plates <NUM> are disposed on the top wall. The plurality of partition plates <NUM> on the bottom wall can extend toward the top wall and be perpendicular to the bottom wall to form a vertical flow guide design, and the plurality of partition plates <NUM> on the top wall can extend toward the bottom wall and be perpendicular to the top wall to form a vertical flow guide design. The height of the partition plates <NUM> may be smaller than the height of the tank body <NUM>, and the plurality of partition plates <NUM> on the top wall and the plurality of partition plates <NUM> on the lower wall may be arranged in a staggered manner, so that the plurality of water chambers <NUM> are communicated with each other to guide the steam from the lower end of one water chamber <NUM> to the upper end of another water chamber, wherein the vertical flow guide design has the advantage of avoiding excessive contact between the hot steam and the cold water and reducing steam consumption. By using the characteristic that the higher the temperature of water is, the smaller the density is, the steam or hot water is always above the cold water, so as to limit the contact area between the steam and the cold water, reduce the steam consumption and reduce the water temperature rise. According to the invention, the upper part of the left water chamber <NUM> of the tank body <NUM> is provided with a pressurized steam inlet, and the pressurized steam inlet is connected to the steam-pressurizing pipelines <NUM>. The lower part of the right water chamber <NUM> of the tank body <NUM> is provided with a drain outlet, and the drain outlet is connected to the drain pipeline <NUM>. In some embodiments, each water chamber <NUM> may be provided with a exhaust pipeline <NUM> that may be used to vent steam from each water chamber <NUM>. In some embodiments, the exhaust pipeline <NUM> may be provided with an exhaust valve <NUM>, which opens to allow the steam in the water chamber <NUM> to be exhausted from the exhaust pipeline <NUM>. After the tank body <NUM> is emptied, the exhaust valve <NUM> can be opened to discharge the high-pressure steam in the tank body <NUM> and relieve the pressure of the water tank.

Further, in some embodiments, the steam-pressurizing pipelines <NUM> may be arranged in one-to-one correspondence with the steam-pressurizing water tanks <NUM>, and may be connected to the pressurized steam inlets at the upper portions of the water chambers <NUM> of the steam-pressurizing water tanks <NUM>, so that the high pressure steam may enter from the upper portions of each water chamber <NUM> to pressurize the water downward, From the drain pipeline <NUM> to the passive containment cooling system <NUM>, the secondary-side passive cooling system <NUM>, the spraying system <NUM>, and the reactor core assembly <NUM>, and also to the next stage steam-pressurizing water tank <NUM> through the series pipeline <NUM>. In some embodiments, asteam-pressurizing pipeline <NUM> may be provided with a bypass valve <NUM>. When the bypass valve <NUM> is opened, the steam in the steam-pressurizing main pipeline <NUM> may be output to the steam-pressurizing pipeline <NUM> and input to the steam-pressurizing water tanks <NUM>. In some embodiments, a steam-pressurizing pipeline <NUM> may also be connected to an external steam system. The external steam system can be the auxiliary steam system (SVA) and the main steam system of the adj acent unit. A steam-pressurizing pipeline <NUM> is fed from the steam generator <NUM> of the passive special safety system of the plant or from an external steam system. Wherein, when the steam generator <NUM> is used for air supply, the atmospheric discharge valve <NUM> may be opened to reduce the steam pressure to <NUM> bar. G, when the steam supply by the auxiliary steam of the SVA, the pressure is not reduced.

Further, in some embodiments, a water replenishing pipeline <NUM> may be arranged in one-to-one correspondence with a steam-pressurizing water tank <NUM>. Of course, it is understood that, in other embodiments, a water replenishing pipeline <NUM> may not be limited to being arranged in one-to-one correspondence with a steam-pressurizing water tank <NUM>. One end of a water replenishing pipeline <NUM> may be connected to a water inlet at a lower portion of a water chamber <NUM> at the left end of the tank <NUM>, and the other end of a water replenishing pipeline <NUM> may be connected to an external water source. Specifically, in some embodiments, one end of a water replenishing pipeline <NUM> may be connected to the overhead water tank and/or the in-plant demineralized water tank, so that replenishing water may be supplied to the steam-pressurizing water tank <NUM> in time. In some embodiments, a water replenishing pipeline <NUM> may be provided with a water replenishing valve <NUM>, when the water replenishing valve <NUM> is opened, and the water replenishing pipeline <NUM> may supply water to the steam-pressurizing water tank <NUM>. Since the steam-pressurizing water tanks <NUM> are installed at the ground level, the water level of the demineralized water tank in the plant is higher, and the water tank is generally located on the hill in the plant area, and the position is higher. Therefore, after the pressure of a steam-pressurizing water tank <NUM> is completely released, the water replenishing valve <NUM> may be opened to replenish water by gravity. After the water is replenished, the water replenishing valve <NUM> is closed, and the steam-pressurizing water tank <NUM> can be put into operation again or placed in a standby state.

Further, in some embodiments, one end of a drain pipeline <NUM> may be connected to a water outlet at a lower portion of the water chamber at the right end of the pressurized steam water tank <NUM>, and a drain pipeline <NUM> may be provided with a plurality of branch pipelines respectively connected to the passive containment cooling system <NUM>, the secondary-side passive cooling system <NUM>, the spraying system <NUM>, and the reactor core assembly <NUM>. In some embodiments, a drainage valve <NUM> may be provided on a drain pipelines <NUM>, and the drainage valve <NUM> may be opened to drain the passive containment cooling system <NUM>, the secondary-side passive cooling system <NUM>, the spraying system <NUM>, and the reactor core assembly <NUM>. In some embodiments, a drainage valve <NUM> may be correspondingly disposed on a branch pipeline of the drain pipeline <NUM>.

Further, in some embodiments, there may be a plurality of steam-pressurizing water tanks <NUM>, and the plurality of steam-pressurizing water tanks <NUM> may be connected in sequence to form a multi-stage water tank group. Specifically, in some embodiments, the number of the steam-pressurizing water tanks <NUM> may be four. Of course, it is understood that in other embodiments, the number of the steam-pressurizing water tanks <NUM> is not limited to four, and may be one or more than four. Further, in some embodiments, the water supply system further includes one or more series pipelines <NUM>. A series pipeline <NUM> may be disposed between two adjacent steam-pressurizing water tanks <NUM>, and may be used to connect the two adjacent steam-pressurizing water tanks <NUM>, so that the two adjacent steam-pressurizing water tanks <NUM> may be communicated. In some embodiments, a series pipeline <NUM> may be provided with a series valve <NUM>, and a series valve <NUM> may be used to connect or isolate two adjacent steam-pressurizing water tanks <NUM>. When all the series valves <NUM> are opened, the plurality of steam-pressurizing water tanks <NUM> may form a multi-stage water tank, and when all the series valves <NUM> are closed, each steam-pressurizing water tank <NUM> is an independent water tank. In some embodiments, a series pipelines <NUM> may also be connected to a drain pipeline <NUM>, and in some embodiments, an outlet valve <NUM> may be provided at an end of a series pipelines <NUM> connected to a drain pipeline <NUM>. The open of a outlet valve <NUM> places a series pipeline <NUM> in communication with a drain pipeline <NUM>. Through a series valve <NUM> and a outlet valve <NUM>, the steam-pressurizing water tanks can be operated in series, and the steam-pressurizing water tank can be cut/isolated and put into operation. According to the water storage condition of a steam-pressurizing water tank <NUM>, the steam-pressurizing water tank <NUM> can be operated independently or in parallel by using the outlet valves <NUM> and the series valves <NUM> of the steam-pressurizing water tank <NUM>, or the steam-pressurizing water tank <NUM> can be emptied or the steam-pressurizing water tank <NUM> can be cut/isolated in case of water shortage.

The passive special safety system of the nuclear power plant, according to an embodiment of the present invention, may inject the water in a steam-pressurizing water tank <NUM> into the passive containment cooling system <NUM>, the secondary-side passive cooling system <NUM>, the spraying system <NUM> and the reactor core assembly <NUM> in a passive manner by using the high-temperature and high-pressure steam generated by the external steam system and/or the steam generator. The operation of the passive special safety system of the nuclear power plant may include three steps, namely, separating and depressurizing the steam generators, pressurizing a steam-pressurizing water tank <NUM> to supply water to users, and refilling a steam-pressurizing water tank with water. The specific operation is as follows:.

According to the requirements of accident control strategy, the passive special safety system, according to an embodiment of the present invention, may have six operation modes, including "Safety Injection Mode", "Containment Spray Mode", "Containment Cooling Mode", "Secondary-side Water Resupplying Mode ", "Secondary-side Passive Cooling Mode" and "Reactor Pit Injection Mode", as follows:.

When a primary circuit breaks, if the safety injection system is activated, the primary circuit water inventory is restored. If the safety injection system fails due to equipment or external disasters, the water supply system <NUM> of the present invention can be used to inject water into the reactor core assembly <NUM>. After the water supply system <NUM> of the invention is put into operation, the water temperature at the outlet of the water tank is about <NUM>, the pressure is 15bar. G or 12bar. G, the pressure head is the same as that of the outlet of the low-pressure safety injection pump, and the outlet water temperature is close to that of the refueling water tank, so it can be used as a low-pressure safety injection train.

When a primary break, if the containment spraying system is activated, the containment pressure is reduced. If the containment spraying system fails due to equipment or external disasters, the water supply system <NUM> of the present invention can be used to spray water to the containment. After the water supply system <NUM> of the invention is put into operation, the water temperature at the outlet of the water tank is about <NUM>, the pressure is 15bar. G or 12bar. G, the pressure head is the same as the pressure head at the outlet of the containment spray pump, and the outlet water temperature is close to the water temperature of the refueling water tank, so it can be used as a row of containment spray.

For the power plant installed with the passive cooling system of the containment, the high-level water tank of the containment can be cancelled in the design, and only a heat exchanger <NUM> and a water tank <NUM> soaking the heat exchanger <NUM> are reserved. When the passive cooling system of the containment needs to be put into operation, the water tank <NUM> soaking the heat exchanger <NUM> is filled with water through one or more steam-pressurizing water tanks <NUM> or the active water pump, so as to reduce the load of the containment.

In the event of a total loss of feedwater accident, for a nuclear power plant without a secondary-side passive cooling system installed, the passive special system can be used as a means of mitigating the total loss of feedwater accident of the unit by using the steam-pressurizing water tank <NUM> to replace the main feedwater system (ARE) or the auxiliary feedwater system (ASG) to make up the SG before the "feed and bleed" is put into operation. Withdraw the primary circuit to the connection state of the residual heat removal system, so as to avoid the operation of the "feed and bleed".

In the event of a total loss of feedwater accident, for a nuclear power plant equipped with a secondary-side passive cooling system, a heat exchanger <NUM> and a water tank <NUM> soaking the heat exchanger <NUM> can be retained, and the water tank <NUM> with a smaller volume can be replaced to maintain operation for several hours. When the secondary-side passive cooling system is put into operation, one or more steam-pressurizing water tanks <NUM> provide continuous replenishing water. Or directly replace the secondary-side passive cooling system.

When a severe accident occurs in the power plant (the reactor core outlet temperature reaches <NUM>), the reactor cavity water injection system (RPF) can fill the reactor cavity with water within half an hour at the stage of large flow (greater than 360m3/H) (the reactor cavity height is -<NUM> ~ <NUM>, and the space volume is about 180m3). Then it will be transferred to the water supplement stage with small flow (about 40m3/H) to compensate the evaporation loss. This stage will last for about <NUM> hours. When the fire water distribution system (JPD) cannot supply water or cannot supply enough water, it is considered to add a temporary water injection interface on the system to take water from one or more steam-pressurizing water tanks <NUM> and inject it into the reactor cavity.

The nuclear power plant passive special safety system, according to an embodiment of the present invention, can be used to mitigate the consequences of a reactor accident in the event of:.

When the primary circuit break accident, the safety injection system and the spraying system will automatically start according to the parameters such as the temperature and pressure of the primary circuit and the pressure of the containment <NUM>, the water inventory of the primary circuit will be restored, and the pressure of the containment <NUM> will also drop. For plants with the containment <NUM> passive cooling system installed, the containment <NUM> atmosphere is cooled by a high-level water tank on the containment <NUM>, through the steel wall containment <NUM>, or a heat exchanger, when the containment <NUM> pressure and temperature increase. If the equipment of the safety injection system fails or cannot operate due to external disasters, the primary water inventory cannot be restored, which will lead to the exposure of the core. If the equipment of containment <NUM> spray devices fails or cannot operate due to external disasters, the third barrier of the reactor has the risk of rupture, and the risk of radioactive leakage increases.

The passive special safety system is simple to operate, does not depend on external resources (such as a water source and a power supply), and can be quickly put into operation after an accident to relieve the consequences of the accident. Therefore, the commissioning of the passive special safety system should serve as an effective backup to the safety injection system and the spraying system <NUM> in the containment <NUM> following a "primary break".

For the power plant equipped with the passive cooling system of the containment <NUM>, when the present invention is adopted, the high-level water tank of the containment <NUM> can be eliminated in design, and only a heat exchanger <NUM> and a water tank <NUM> soaking the heat exchanger <NUM> are reserved; when the passive cooling system of the containment needs to be put into operation, the water tank <NUM> soaking the heat exchanger <NUM> is filled with water through one or more steam-pressurizing water tanks <NUM> or the active water pump, And thus reduce that load on the containment <NUM>.

Following a "total loss of feedwater" accident, the existing accident management strategy will use the "feed and bleed" to maintain core cooling and fall back. The strategy is implemented in two steps: <NUM>. Waitting; <NUM>. Opening the pressurizer relief pipeline and starting the safety injection; <NUM>. Putting the containment <NUM> spray into operation, and transfering the heat to the component cooling water system (RRI) through the containment spraying system (EAS) cooler, and then transfer the heat to the sea through the essential service water system (SEC). This strategy can effectively bring the unit to the state of connecting the residual heat removal system, but there is also a greater damage to the unit. After the implementation of "feed and bleed " operation, the unit may face the consequences of long-term shutdown for system equipment maintenance, or even direct retirement.

For a nuclear power plant without a secondary-side passive cooling system, the passive special system can be used as a mitigation means for a unit total loss of feedwater accident; before "feed and bleed" is put into operation, the passive special system is used for establishing the water supply of steam generator <NUM>, and a loop is withdrawn to a residual heat removal system connection state, So as to avoid the input of the "feed and bleed". For the nuclear power plant installed with the secondary-side passive cooling system, the heat exchanger and the water tank soaking the heat exchanger can be reserved and soaked, and the volume of the water tank can be reduced to maintain operation for several hours. When the secondary-side passive cooling system is put into operation, the steam-pressurizing water tank can provide continuous replenishing water or directly replace the secondary-side passive cooling system.

The passive special safety system is simple to operate, does not depend on external resources (such as a water source and a power supply), and can be quickly put into operation after an accident to relieve the consequences of the accident. Therefore, for the nuclear power plant without the secondary-side passive cooling system, the commissioning of the passive special safety system should be the preferred response after the "total loss of feedwater accident". For the nuclear power plant installed with the secondary-side passive cooling system, a heat exchanger <NUM> and a water tank <NUM> soaking the heat exchanger <NUM> can be reserved and the a smaller water tank can be replaced to maintain operation for several hours. When the secondary-side passive cooling system is put into operation, one or more steam-pressurizing water tanks <NUM> provide continuous replenishing water.

In that event of a severe accident in the power plant, when the molten core falls into the low head of the reactor pressure vessel (RPV) <NUM>, water is injected into the reactor cavity to cool the outside of the reactor pressure vessel <NUM>, and the reactor cavity and other safety functions (such as primary loop pressure relief, etc.) act simultaneously to maintain the integrity of the RPV, so that the molten core fragment are retained in the pressure vessel <NUM>, prevents most ex-core phenomena (direct heating of the containment <NUM>, steam explosions, melt-concrete reactions, etc.) That could threaten the integrity of the containment <NUM>.

For the nuclear power plant equipped with the reactor cavity water injection system (RPF), the reactor cavity can be filled with water within half an hour in the large flow phase of the RPF, and then the reactor cavity can be filled with water in the small flow phase to compensate the evaporation loss. This phase lasts for about <NUM> hours. When the fire water distribution system (JPD) cannot supply water or cannot supply enough water, a temporary water injection interface can be added to the system. Water is taken from the steam-pressurizing water tank <NUM> of the present invention and injected into the reactor cavity.

As shown in <FIG>, a primary circuit break accident occurs in a passive special safety system in which four steam-pressurizing water tanks <NUM> are installed in a generation III unit in which a containment high level water tank <NUM> is installed.

Cooling the core requires sufficient water as the cooling medium. Sufficient water supply is required for the cooling and depressurization of containment <NUM> as a source of spray water. In this case, the demineralized water in the plant is used as the cooling water source.

After the accident, the main steam generated by a steam generator <NUM> still has the energy of high temperature and high pressure, which can be used as the water injection power after being decompressed by a atmospheric discharge valve <NUM> to drive the low-pressure water in a steam-pressurizing water tank <NUM> to be injected into the system requiring cooling water.

When a steam generator <NUM> is isolated, it is necessary to open the water injection passage as soon as possible, and open a discharge valve <NUM> directly connected to a steam-pressurizing water tank <NUM> of the relevant system.

The system is put into operation according to the three steps in the technical scheme.

Step <NUM>: separating and depressurizing the steam generator. Perform main steam isolation and close the main steam isolation valves of the three steam generators <NUM>. The steam pressure is reduced to 15bar. G through the pressure reducing valve. When supplying steam through the auxiliary steam of the SVA, pressure is not reduced.

Step <NUM>: The steam-pressurizing water tank <NUM> pressurizes water to the reactor core assembly <NUM>, the passive containment cooling system <NUM>, the secondary-side passive cooling system <NUM>, the steam generator <NUM>, and/or the spraying system <NUM>. When the water supply system is put into operation, the steam-pressurizing valve <NUM> of a first steam-pressurizing water tank <NUM> is opened, and the steam-pressurizing water tank <NUM> is pressurized to an operating pressure. The outlet valve <NUM> of a last steam-pressurizing water tank <NUM> is opened, and water stored in the steam-pressurizing water tank <NUM> is output from a drain pipeline <NUM> to supply water to the reactor core assembly <NUM>, the passive containment cooling system <NUM>, the secondary-side passive cooling system <NUM>, the steam generator <NUM>, and/or the spraying system <NUM>.

Step <NUM>: The steam-pressurizing water tank <NUM> is refilled with water. After a steam-pressurizing water tank <NUM> is emptied, the inside is filled with high-pressure steam. Isolate it from other steam-pressurizing water tanks <NUM>, and open the exhaust pipelines <NUM> corresponding to each water chamber <NUM> for pressure relief. As the steam-pressurizing water tank is installed at the ground level, the water level of the demineralized water tank in the plant is relatively high. Generally, there is a water tank on the hill in the plant area, and the position is higher. Therefore, after the pressure of the steam-pressurizing water tank <NUM> is completely released, a water replenishing valve <NUM> may be opened to replenish water by gravity. After the water is replenished, the water replenishing valve is closed, and the water can be put into the steam-pressurizing water tank <NUM> again or placed in a standby state.

Step <NUM>: separating and depressurizing the steam generator. Perform main steam isolation and close the main steam isolation valves of the three steam generators <NUM>. The steam pressure is reduced to 15bar. G through a pressure reducing valve. When supplying steam through the auxiliary steam of the SVA, pressure is not reduced.

Step <NUM>: The steam-pressurizing water tank <NUM> pressurizes water to the reactor core assembly <NUM>, the passive containment cooling system <NUM>, the secondary-side passive cooling system <NUM>, the steam generator <NUM>, and/or the spraying system <NUM>. When the water supply system is put into operation, the steam-pressurizing valve <NUM> of a first steam-pressurizing water tank <NUM> is opened, and the steam-pressurizing water tank <NUM> is pressurized to an operating pressure. The outlet valve <NUM> of a last steam-pressurizing water tank <NUM> is opened, and water stored in the steam-pressurizing water tank <NUM> is output from the drain pipelines <NUM> to supply water to the reactor core assembly <NUM>, the passive containment cooling system <NUM>, the secondary-side passive cooling system <NUM>, the steam generator <NUM>, and/or the spraying system <NUM>.

Step <NUM>: The steam-pressurizing water tank <NUM> is refilled with water. When a steam-pressurizing water tank <NUM> is emptied, the inside is filled with high-pressure steam. Isolate it from other steam-pressurizing water tanks <NUM>, and open the exhaust pipeline <NUM> corresponding to each water chamber <NUM> for pressure relief. As the steam-pressurizing water tank is installed at the ground level, the water level of the demineralized water tank in the plant is relatively high. Generally, there is a water tank on the hill in the plant area, and the position is higher. Therefore, when the pressure of a steam-pressurizing water tank <NUM> is completely released, a water replenishing valve <NUM> may be opened to replenish water by gravity. After the water is replenished, the water replenishing valve is closed, and the water can be put into the steam-pressurizing water tank <NUM> again or placed in a standby state.

The beneficial effects of the passive special safety system of the nuclear power plant are as follows:.

Claim 1:
A water supply system (<NUM>) for a passive special safety system of a nuclear power plant, which is connected to a passive containment cooling system (<NUM>), a secondary-side passive cooling system (<NUM>), a spraying system (<NUM>) and/or a reactor core assembly (<NUM>) of the passive special safety system of the nuclear power plant, wherein :
said water supply system comprises at least one steam-pressurizing water tank (<NUM>), at least one steam-pressurizing pipeline (<NUM>), at least one water replenishing pipeline (<NUM>) and a drain pipeline (<NUM>);
each steam-pressurizing water tank (<NUM>), in use, is connected to the steam generated by the steam generator (<NUM>) and is pressurized by the steam to drive the water in the steam-pressurizing water tank (<NUM>) to be delivered out;
each steam-pressurizing pipeline (<NUM>) is connected with a steam-pressurizing water tank (<NUM>) and, in use, is connected to
a steam generator (<NUM>) in the passive special safety system of the nuclear power plant and/or an external steam system;
each water replenishing pipeline (<NUM>) is connected with a steam-pressurizing water tank (<NUM>) and, in use, is connected to an external water source;
the drain pipeline (<NUM>) is connected to the steam-pressurizing water tanks (<NUM>) and, in use, is connected to to the passive containment cooling system (<NUM>), the secondary-side passive cooling system (<NUM>), the spraying system (<NUM>), and/or the reactor core assembly (<NUM>),
wherein each steam-pressurizing water tank (<NUM>) comprises a tank body (<NUM>), a plurality of partition plates (<NUM>) and a plurality of water chambers (<NUM>);
characterized in that
the tank body (<NUM>) is a horizontal tank;
the plurality of the partition plates (<NUM>) are provided in the tank body (<NUM>) and are arranged at intervals along the length direction of the tank body (<NUM>), partitioning a space in the tank body (<NUM>) into a plurality of water chambers (<NUM>);
the plurality of water chambers (<NUM>) comprises a left water chamber (<NUM>) and a right water chamber (<NUM>) arranged along the length direction of the tank body (<NUM>);
the upper part of the left water chamber (<NUM>) of the tank body (<NUM>) is provided with a pressurized steam inlet, connected to a steam-pressurizing pipeline (<NUM>); and
the lower part of the right water chamber (<NUM>) of the tank body (<NUM>) is provided with a drain outlet, connected to the drain pipeline (<NUM>).