WO2022168504A1

WO2022168504A1 - Safety system for nuclear power plant

Info

Publication number: WO2022168504A1
Application number: PCT/JP2021/048682
Authority: WO
Inventors: 隆久松崎; 智彦池側; 宏昌千年; 聖平野
Original assignee: 日立Ｇｅニュークリア・エナジー株式会社
Priority date: 2021-02-05
Filing date: 2021-12-27
Publication date: 2022-08-11
Also published as: JP7431184B2; JP2022120630A

Abstract

This safety system for a nuclear power plant comprises: an IC cooling water pool installed outside a reactor container; an intermediate tank positioned inside the reactor container and lower than the IC cooling water pool, the intermediate tank receiving and being capable of storing cooling water discharged from the IC cooling water pool; a drain line that leads cooling water from the IC cooling water pool to the intermediate tank; a drain valve provided on the drain line; a pressure reduction line, one side of which is connected to a reactor pressure vessel, and the other side of which opens at a position lower than the water level assumed when cooling water from the IC cooling water pool is stored in the intermediate tank; and a pressure reduction valve provided on the pressure reduction line. The drain valve and the pressure reduction valve open in accordance with the degree of pressure in the reactor pressure vessel.

Description

Nuclear plant safety system

The present invention relates to the safety system of nuclear power plants.

In a nuclear power plant, when it is necessary to stop the plant, such as during periodic inspections or when there is a problem with a part of the plant, the nuclear fission reaction is stopped by inserting control rods, which are reactivity control systems, into the core. Shut down the furnace. Since the core generates heat due to decay heat even after the reactor is shut down, it is necessary to release the decay heat from the reactor to the outside of the system.

One of the devices that releases decay heat to the outside of the system to cool the reactor is the isolation condenser (hereinafter referred to as IC). The IC has a heat exchanger placed in a cooling water pool installed at a position higher than the core. In the IC, the steam generated by the decay heat of the core is guided to the heat exchanger, cooled by the cooling water in the cooling water pool, and condensed. By condensing the steam from the reactor pressure vessel or steam generator, the increase in temperature and pressure of the reactor pressure vessel or steam generator is suppressed. Decay heat removal can continue as the water condensed in the IC heat exchanger is fed back to the reactor pressure vessel or steam generator by gravity. Since the operation of the IC does not require an emergency power supply or active equipment, plant safety is improved and plant equipment costs can be reduced. The amount of heat removed by the IC decreases as the reactor pressure vessel or steam generator pressure decreases. Therefore, in order to maintain the heat removal function of the IC, it is generally necessary to keep the reactor pressure vessel at a pressure of 1 MPa or higher.

Some boiling water reactors (BWR) are equipped with an automatic depressurization system for depressurizing the reactor pressure vessel in addition to the IC (see Patent Document 1, for example). The automatic depressurization system depressurizes the reactor pressure vessel by releasing the steam in the reactor pressure vessel to a pressure suppression pool provided in the reactor containment vessel. Since the steam from the reactor pressure vessel is discharged into the cooling water and condensed in the pressure suppression pool, pressure rise in the reactor containment vessel can be suppressed. The automatic depressurization system depressurizes the reactor pressure vessel to 0.5 MPa or less by forcibly opening a safety valve provided in the main steam pipe.

JP-A-2002-122689

When a pressure suppression pool is provided in the reactor containment vessel as in the boiling water nuclear power plant described in Patent Document 1, the structure of the reactor containment vessel becomes complicated, increasing costs. If the suppression pool can be eliminated, the structure of the reactor containment vessel can be simplified, and costs can be reduced.

Also, in order to reduce the cost of nuclear power plants, it is important to eliminate dynamic equipment such as water injection pumps and emergency power sources. By eliminating the active equipment and the emergency power supply, the cost of the active equipment and the emergency power supply itself can be reduced, and the cost associated with their maintenance can also be reduced.

In the case where both an automatic pressure reducing system and an IC are provided as in the boiling water nuclear power plant described in Patent Document 1, if the automatic pressure reducing system malfunctions, the reactor pressure vessel will be depressurized. There is a concern that a state in which the thermal function cannot be effectively used may occur. Therefore, a plant concept has been proposed in which the automatic depressurization system including the safety valve is eliminated, emphasizing the utilization of the heat removal function of the IC. A plant concept that makes the most of the IC's capabilities eliminates the pressure suppression pool and eliminates the need for an emergency power supply or water injection pump, thereby reducing costs.

In this plant concept, ICs are multiplexed from the viewpoint of safety. Therefore, it is extremely unlikely that all ICs will not work. However, in the unlikely event that all the ICs do not operate, it is assumed that the reactor pressure vessel cannot be depressurized in this concept plant because the automatic depressurization system is omitted. Failure to depressurize the reactor pressure vessel may eventually lead to the reactor pressure vessel being damaged by the high pressure. Therefore, it is necessary to consider depressurizing the reactor pressure vessel when assuming that the IC is inoperative.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its object is to simplify the structure of the reactor containment vessel, and to provide the same even when the emergency condenser is inoperative. A nuclear plant safety system is provided that can depressurize a reactor pressure vessel or steam generator without using dynamic equipment.

The present application includes a plurality of means for solving the above-mentioned problems, but if one example is given, the steam from the reactor pressure vessel or the steam generator stored in the reactor containment vessel is condensed by cooling and the above-mentioned atomic A safety system for a nuclear plant comprising an emergency condenser returning to a reactor pressure vessel or said steam generator, comprising a water source for storing cooling water located outside said reactor containment vessel, and said reactor containment vessel. a reservoir positioned inside a container and positioned below the water source and capable of receiving and storing cooling water discharged from the water source; a first line leading to a reservoir, a first valve provided on the first line for switching the first line to an open state or a closed state, one side directly to the reactor pressure vessel or the steam generator a second line connected directly or indirectly and having the other side open at a position lower than an assumed water level when the cooling water from the water source is stored in the storage section; and a second valve for switching the second line between an open state and a closed state, the first valve and the second valve depending on the pressure inside the reactor pressure vessel or the steam generator. characterized in that it is configured to open the valve by

According to the present invention, even if the pressure in the reactor pressure vessel or the steam generator rises outside the normal range due to non-operation of the isolation condenser, the first valve and the second valve can be opened. Since the steam from the reactor pressure vessel or the steam generator is introduced into the cooling water discharged from the water source to the reservoir and condenses, the reactor pressure vessel can be installed without providing a pressure suppression pool in the reactor containment vessel. Depressurization is possible. That is, the structure of the reactor containment vessel can be simplified, and the reactor pressure vessel can be depressurized without using dynamic equipment even when the isolation condenser is inoperative.
Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

1 is a schematic system diagram showing a boiling water nuclear power plant equipped with a first embodiment of a nuclear power plant safety system according to the present invention; FIG. FIG. 2 is a schematic diagram showing an example of the structure of a drain valve and a pressure reducing valve that constitute a part of the first embodiment of the nuclear plant safety system of the present invention shown in FIG. 1; FIG. 3 is a schematic diagram showing an operating state (valve open state) of the drain valve and the pressure reducing valve shown in FIG. 2 when IC is not operated; FIG. 2 is a schematic diagram showing an example of the structure of a fusion valve forming part of the first embodiment of the nuclear plant safety system of the present invention shown in FIG. 1; FIG. 2 is a schematic system diagram showing an operating state of an isolation condenser (IC) in the first embodiment of the nuclear plant safety system of the present invention shown in FIG. 1; FIG. 2 is a schematic system diagram showing an operating state when an IC is not operating in the first embodiment of the safety system of the nuclear power plant of the present invention shown in FIG. 1; FIG. 2 is a schematic system diagram showing a nuclear power plant equipped with a second embodiment of a safety system for a nuclear power plant according to the present invention; FIG. 5 is a schematic system diagram showing a nuclear plant equipped with a third embodiment of the nuclear plant safety system of the present invention; FIG. 10 is a schematic system diagram showing a nuclear power plant equipped with a fourth embodiment of the safety system of the nuclear power plant of the present invention; FIG. 11 is a schematic system diagram showing a nuclear plant equipped with a fifth embodiment of the nuclear plant safety system of the present invention; FIG. 5 is a block diagram showing a modification of the valve drive system for driving the pressure reducing valves forming part of the first to fifth embodiments of the nuclear plant safety system of the present invention; FIG. 12 is a block diagram showing a state when the pressure reducing valve is operating (opening) in the modification of the pressure reducing valve driving system shown in FIG. 11; FIG. 5 is a block diagram showing a modification of the valve drive system for driving the drain valves constituting part of the first to fifth embodiments of the nuclear plant safety system of the present invention; FIG. 14 is a block diagram showing a state when the drain valve is actuated (opened) in the modification of the drain valve drive system shown in FIG. 13; 1 is a schematic system diagram showing a pressurized water type nuclear power plant equipped with an embodiment of a nuclear power plant safety system according to the present invention; FIG.

An embodiment of a safety system for a nuclear power plant according to the present invention will be described below with reference to the drawings. First to fifth embodiments described below are examples in which the present invention is applied to a boiling water reactor (BWR).

[First embodiment]
A configuration of a nuclear power plant equipped with a first embodiment of a safety system for a nuclear power plant according to the present invention will be described with reference to FIG. FIG. 1 is a schematic system diagram showing a boiling water nuclear power plant equipped with a first embodiment of a nuclear power plant safety system according to the present invention. Note that FIG. 1 shows the state of the plant during normal operation.

In FIG. 1, a reactor pressure vessel 13 containing a reactor core 12 is stored in a reactor containment vessel 11 of a nuclear power plant 1 . The pressure inside the reactor containment vessel 11 is substantially the same as the atmospheric pressure outside the reactor containment vessel 11 during normal operation. The reactor pressure vessel 13 is a region where steam is generated by nuclear fission reaction heat or decay heat of the reactor core 12, and a liquid phase portion 13a is formed on the lower side and a gas phase portion 13b (mainly steam) is formed on the upper side. A main steam pipe 14 is connected to the reactor pressure vessel 13 to send steam generated in the reactor pressure vessel 13 to a turbine (not shown). The main steam pipe 14 penetrates the reactor containment vessel 11 . Main steam isolation valves 15 capable of shutting off the main steam pipe 14 are installed inside and outside the reactor containment vessel 11 in the main steam pipe 14 .

The nuclear plant 1 has an emergency recovery system that releases thermal energy outside the system (outside the reactor containment vessel 11) as a safety system for maintaining the nuclear plant 1 in a safe state when an abnormality occurs in the nuclear reactor. It further comprises a water vessel 30 (hereinafter referred to as IC) and a depressurization protection system 40 for depressurizing the reactor pressure vessel 13 when the IC 30 does not operate. Since the nuclear power plant 1 is provided with the decompression protection system 40, the conventional automatic decompression system including the pressure suppression pool for decompressing the reactor pressure vessel 13 is eliminated.

The IC 30 condenses steam from the reactor pressure vessel 13 by cooling and returns it to the reactor pressure vessel 13 again. The IC 30 includes an IC cooling water pool 31 that stores cooling water, an IC heat exchanger 32 arranged in the IC cooling water pool 31, an inlet (upper side) of the IC heat exchanger 32, and the main steam pipe 14 (nuclear reactor The IC steam supply line 33 connecting the gas phase portion 13b) of the pressure vessel 13, the outlet (lower side) of the IC heat exchanger 32 and the lower portion of the reactor pressure vessel 13 (the portion corresponding to the liquid phase portion 13a) and an IC return line 34 connecting the An IC start valve 35 for starting the IC 30 is installed on the IC return line 34 .

The IC cooling water pool 31 is installed outside the reactor containment vessel 11 and is positioned above the reactor core 12, precisely at a position higher than the normal water level 13c in the reactor pressure vessel 13. . The IC cooling water pool 31 has, for example, an opening 31a and is open to the atmosphere. The IC steam supply line 33 supplies steam in the reactor pressure vessel 13 to the IC heat exchanger 32 . The IC heat exchanger 32 cools and condenses the steam from the reactor pressure vessel 13 supplied through the IC steam supply line 33 with the cooling water in the IC cooling water pool 31 . The IC return line 34 returns water produced in the IC heat exchanger 32 to the reactor pressure vessel 13 . The IC start-up valve 35 is closed during normal operation, but is opened when the pressure of the reactor pressure vessel 13 rises above a predetermined value, for example, when a signal indicating a pressure rise is input. is configured to

In the nuclear plant 1, the IC30 is multiplexed to improve the safety of the nuclear plant 1. For example, three to four ICs 30 (only one is shown in FIG. 1) are installed.

The depressurization protection system 40 protects the reactor pressure vessel 13 by depressurizing the reactor pressure vessel 13 when the IC 30 does not operate and the pressure inside the reactor pressure vessel 13 deviates from the normal range and rises. It is configured to start using the steam whose pressure has increased in the reactor pressure vessel 13 . Specifically, the decompression protection system 40 is positioned inside the IC cooling water pool 31 of the IC 30 as a water source for storing cooling water, and inside the reactor containment vessel 11 and below the IC cooling water pool 31. an intermediate tank 41; a drain line 42 connecting the IC cooling water pool 31 and the intermediate tank 41; a drain valve 43 and a check valve 44 provided on the drain line 42; 41 and a pressure reducing valve 46 provided on the pressure reducing line 45 .

The intermediate tank 41 is configured in an empty state in which cooling water is not stored during normal operation, and receives and stores the cooling water discharged from the IC cooling water pool 31 only when the IC 30 does not operate. It is a tank installed to function as a reservoir that allows The weight of the intermediate tank 41 is reduced because it does not store cooling water during normal operation. Therefore, the intermediate tank 41 has a reduced load during an earthquake that may cause failure. The intermediate tank 41 is located away from the reactor pressure vessel 13 , for example, directly below the IC cooling water pool 31 . Control rods and a large number of pipes (not shown) are often arranged below and around the reactor pressure vessel 13, and this is suitable when the installation space for the intermediate tank 41 cannot be secured.

The drain line 42 guides at least part of the cooling water stored in the IC cooling water pool 31 to the intermediate tank 41 . For example, one side of the drain line 42 is connected to the bottom of the IC cooling water pool 31, and the other side is opened at a position higher than the assumed water level 41a when the intermediate tank 41 stores the cooling water from the cooling water tank. is configured to The drain line 42 is arranged inside the reactor containment vessel 11 over its entire length, for example.

A check valve 44 and a drain valve 43 are arranged on the drain line 42 in this order from the upper side (upstream side). The check valve 44 and the drain valve 43 are arranged inside the reactor containment vessel 11, for example.

The check valve 44 is configured to allow flow from the IC cooling water pool 31 toward the intermediate tank 41 while blocking flow from the intermediate tank 41 toward the IC cooling water pool 31 . The check valve 44 prevents the gas inside the reactor containment vessel 11 from being released to the outside of the reactor containment vessel 11 through the drain line 42 .

The drain valve 43 switches the drain line 42 between an open state and a closed state. The drain valve 43 is closed during normal operation, and is configured to open (activate) when the pressure inside the reactor pressure vessel 13 deviates from the normal range and rises. The drain valve 43 is opened by utilizing the pressure of steam generated in the reactor pressure vessel 13. For example, the steam pressure in the reactor pressure vessel 13 is transmitted through the pressure transmission pipe 70. Thus, the valve is configured to be switched between the valve open state and the valve closed state according to the pressure. The structure of the drain valve 43 will be described later. The pressure transmission pipe 70 connects the upper portion (the gas phase portion 13b) of the reactor pressure vessel 13 and a later-described valve opening/closing mechanism 54 (see FIGS. 2 and 3 described later) of the drain valve 43. It is a pipe that transmits the pressure of the container 13 to the drain valve 43 .

One side of the decompression line 45 is indirectly connected to the upper portion (gas phase portion 13b) of the reactor pressure vessel 13 via the main steam pipe 14, and the other side receives cooling water from the IC cooling water pool 31. It is installed so as to open at a position lower than the assumed water level 41 a when stored in the intermediate tank 41 . The decompression line 45 guides part of the steam in the reactor pressure vessel 13 to the intermediate tank 41 and introduces it into the cooling water from the IC cooling water pool 31 stored in the intermediate tank 41 .

The pressure reducing valve 46 switches the pressure reducing line 45 between an open state and a closed state. The pressure reducing valve 46 is closed during normal operation, and is configured to open (activate) when the pressure inside the reactor pressure vessel 13 deviates from the normal range and rises. The pressure reducing valve 46 is opened using the pressure of the steam generated in the reactor pressure vessel 13. For example, the pressure inside the reactor pressure vessel 13 is transmitted through the pressure transmission pipe 70. , the valve is configured to be switched between an open state and a closed state according to the pressure. The pressure reducing valve 46 is configured to open at a pressure higher than that of the drain valve 43 . That is, the pressure reducing valve 46 is configured to start later than the drain valve 43 . The structure of the pressure reducing valve 46 will be described later. The pressure transmission pipe 70 connects the upper portion (the gas phase portion 13b) of the reactor pressure vessel 13 and a later-described valve opening/closing mechanism 54 (see FIGS. 2 and 3 described later) of the pressure reducing valve 46. It is a pipe that transmits the pressure of the container 13 to the pressure reducing valve 46 .

A floor water injection line 47 is connected to the intermediate tank 41 . The floor surface water injection line 47 discharges the stored cooling water discharged from the IC cooling water pool 31 to the intermediate tank 41 to the floor surface 11 a of the reactor containment vessel 11 . The floor surface water injection line 47 extends from the bottom of the intermediate tank 41 toward the floor surface 11 a of the reactor containment vessel 11 , for example. The floor surface water injection line 47 is configured assuming a case where a core meltdown occurs.

A melting valve 48 that closes the floor surface water injection line 47 is provided on the floor surface water injection line 47 . The melting valve 48 is arranged, for example, at the end of the floor surface water injection line 47 near the floor surface 11a. The melting valve 48 is normally closed, and is configured to be opened (activated) by being melted by the heat around the melting valve 48 . The structure of the melting valve 48 will be described later.

Next, an example of the structure of the drain valve and the pressure reducing valve, which constitute a part of the first embodiment of the nuclear plant safety system of the present invention, will be described with reference to FIGS. 2 and 3. FIG. FIG. 2 is a schematic diagram showing an example of the structure of a drain valve and a pressure reducing valve that constitute a part of the first embodiment of the nuclear plant safety system of the present invention shown in FIG. FIG. 3 is a schematic diagram showing an operating state (valve open state) of the drain valve and the pressure reducing valve shown in FIG. 2 when the IC is not operated. The structures of the drain valve and pressure reducing valve are similar. The difference between the drain valve and the pressure reducing valve is that the piping to be installed is different and the working pressure (valve opening pressure) is different.

In FIG. 2, the drain valve 43 and the pressure reducing valve 46 have a valve seat 51 provided in the drain line 42 (the pressure reducing line 45 in the case of the pressure reducing valve 46) and a valve body 52 that can be brought into contact with and separated from the valve seat 51. , a valve spring 53 that biases the valve body 52 toward the valve seat 51 (in the valve closing direction), and a valve opening/closing mechanism 54 that displaces the valve body 52 with respect to the valve seat 51 . The valve seat 51 has an opening 51a (see also FIG. 3) that forms part of the flow path of the drain line 42 (the pressure reducing line 45 in the case of the pressure reducing valve 46). The opening 51a is closed when the valve body 52 is seated. During normal operation of the nuclear power plant 1 , the drain valve 43 and the pressure reducing valve 46 are configured such that the valve body 52 is pressed against the valve seat 51 by the biasing force of the valve spring 53 to open the drain line 42 (the pressure reducing line 45 in the case of the pressure reducing valve 46 ). is configured to close the The valve opening/closing mechanism 54 is configured to be directly operated by the pressure of the steam generated in the reactor pressure vessel 13 supplied through the pressure transmission pipe 70 .

Specifically, the valve opening/closing mechanism 54 includes a cylinder tube 55 to which the pressure of the reactor pressure vessel 13 is input, a piston 56 slidably arranged in the cylinder tube 55, the piston 56, and the valve body 52. and a piston rod 57 connecting the The piston 56 divides the interior of the cylinder tube 55 into a first chamber 55a and a second chamber 55b, and is displaced within the cylinder tube 55 by receiving the pressure in the first chamber 55a and the pressure in the second chamber 55b. The piston rod 57 extends from the first chamber 55 a side of the piston 56 to the outside of the cylinder tube 55 and is connected to the valve body 52 . A pressure transmission pipe 70 is connected to the first chamber 55 a of the cylinder tube 55 to supply steam in the reactor pressure vessel 13 . The second chamber 55b has an opening 55c and is open to the outside of the cylinder tube 55 (inside the reactor containment vessel 11).

A latch 58 with which the piston 56 engages is provided in the cylinder tube 55, as shown in FIG. The latch 58 mechanically holds the piston 56 when the piston 56 is displaced toward the second chamber 55b of the cylinder tube 55 and the valve body 52 is released. That is, the latch 58 maintains the open state in which the drain valve 43 or the pressure reducing valve 46 is operated.

The opening pressure of the drain valve 43 and the pressure reducing valve 46 is adjusted by adjusting the biasing force of the valve spring 53 . That is, the drain valve 43 and the pressure reducing valve 46 are opened when the pressure of the steam inside the reactor pressure vessel 13 transmitted through the pressure transmission pipe 70 rises above the threshold value. The valve opening pressures (threshold values) of the drain valve 43 and the pressure reducing valve 46 are set to be higher than the maximum pressure of the reactor pressure vessel 13 when the IC 30 is in operation. This setting can prevent loss of the heat removal function of the IC 30 due to malfunction of the drain valve 43 and the pressure reducing valve 46 . Also, the opening pressure of the drain valve 43 is set to be lower than the opening pressure of the pressure reducing valve 46 . That is, the drain valve 43 is configured to start earlier than the pressure reducing valve 46 .

When the IC 30 does not operate for some reason and the pressure in the reactor pressure vessel 13 rises, the high pressure state in the reactor pressure vessel 13 causes the pressure transmission pipe 70 to flow through the first chamber 55a of the cylinder tube 55 shown in FIG. 3, the piston 56 in the cylinder tube 55 is displaced toward the second chamber 55b against the biasing force of the valve spring 53. As shown in FIG. As the piston 56 is displaced, the valve body 52 is displaced away from the valve seat 51, so that the opening 51a of the valve seat 51 closed by the valve body 52 is opened. As described above, the drain valve 43 and the pressure reducing valve 46 are configured so that the pressure in the reactor pressure vessel 13 is transmitted to the first chamber 55a of the cylinder tube 55 through the pressure transmission pipe 70. When the pressure in the reactor pressure vessel 13 becomes a high pressure state deviating from the normal range, the valve is automatically opened without any operation by the operator and without using dynamic equipment. Further, the piston 56 is displaced toward the second chamber 55b and engaged with the latch 58, so that the valve body 52 can be maintained in the open state.

Next, an example of the structure of the fusion valve, which constitutes part of the first embodiment of the safety system of the nuclear power plant of the present invention, will be described with reference to FIG. FIG. 4 is a schematic diagram showing an example of the structure of a fusion valve forming part of the first embodiment of the nuclear plant safety system of the present invention shown in FIG.

In FIG. 4, a melting valve 48 is provided at the end of the floor water injection line 47 . The melting valve 48 includes, for example, an end plug 61 capable of closing an end opening of the floor water injection line 47, a swing arm 62 rotatably attached to the end of the floor water injection line 47, and a floor water injection line. 47 and capable of supporting the swing arm 62; a swing lever 64 rotatably attached to the swing arm 62; and a weight 66 attached to the swing lever 64 via a wire 65. , and a low melting point mounting member 67 for mounting the weight 66 to the end of the floor water injection line 47 .

One end of the swing arm 62 is rotatably attached to the end of the floor surface water injection line 47 via a rotating pin 62a, and the other end is detachably supported by a support arm 63. An end plug 61 is fixed to the swing arm 62 so as to close the end opening of the floor surface water injection line 47 when the swing arm 62 is supported by the support arm 63 . The support arm 63 has an engaging portion 63a with which the other end of the swing arm 62 engages. One end of the swing lever 64 is rotatably attached to the other end of the swing arm 62 via a pivot pin 64a, and one end of a wire 65 is joined to the other end. The low-melting-point mounting member 67 is made of a low-melting-point metal, and is broken by melting or softening when a predetermined temperature is exceeded.

When the temperature around the melting valve 48 rises and the low-melting-point mounting member 67 melts, the weight 66 drops due to its own weight, and the impact load of the weight 66 dropping is transmitted to the swing lever 64 via the wire 65 . As a result, the swing lever 64 rotates around the pivot pin 64a so as to push out the support arm 63, and as a result, the engagement between the engaging portion 63a of the support arm 63 and the swing arm 62 is released. The swing arm 62 disengaged from the support arm 63 is no longer supported by the support arm 63, so that the weight 66 hangs down. As the swing arm 62 rotates, the end plug 61 is disengaged from the opening of the floor surface water injection line 47, and the floor surface water injection line 47 is opened. In this way, when the temperature in the vicinity of the melt valve 48 in the reactor containment vessel 11 becomes a high temperature state deviating from the normal range, the melt valve 48 uses dynamic equipment without being operated by an operator. automatically open without

Next, the operation of the safety system of the nuclear power plant according to the first embodiment of the present invention will be explained using FIGS. 1 to 6. FIG. FIG. 5 is a schematic system diagram showing the operating state of the IC in the first embodiment of the nuclear plant safety system of the present invention shown in FIG. FIG. 6 is a schematic system diagram showing the operating state when the IC is not in operation in the first embodiment of the nuclear plant safety system of the present invention shown in FIG.

In the nuclear power plant 1 shown in FIG. 1, when the plant is to be stopped for periodic inspections, etc., or when an event (for example, an earthquake) that may adversely affect the plant occurs, nuclear fission in the core 12 is stopped by inserting control rods. to stop the plant. At that time, if there is a possibility that a turbine (not shown) or the like is malfunctioning due to an earthquake or the like, the main steam isolation valve 15 is closed and the steam is discharged from the reactor pressure vessel 13 to the outside of the containment vessel 11. to prevent it from leaking out.

Even after the reactor is shut down, steam continues to be generated inside the reactor pressure vessel 13 due to the decay heat of the core 12 . If this state continues, the pressure in the reactor pressure vessel 13 will rise. When the pressure rise of the reactor pressure vessel 13 is detected, the IC start valve 35 of the IC 30 opens (starts) as shown in FIG. By opening the IC start-up valve 35 , the steam in the reactor pressure vessel 13 is supplied to the IC heat exchanger 32 through the IC steam supply line 33 . Since the IC heat exchanger 32 is cooled by the cooling water in the surrounding IC cooling water pool 31, the steam flowing into the IC heat exchanger 32 is condensed by cooling and returns to water. The condensed water generated in the IC heat exchanger 32 returns to the reactor pressure vessel 13 through the IC return line 34 due to gravity due to the difference in density from the steam in the IC steam supply line 33, and is used to cool the reactor core 12 again. .

In this way, the IC 30 returns the steam from the reactor pressure vessel 13 to water only by opening the IC start-up valve 35, and supplies it to the reactor pressure vessel 13 again by its own weight, thereby releasing the decay heat of the core 12. keep removing. That is, the IC 30 can release the decay heat of the core 12 to the outside of the system without using a pump (dynamic device) or an emergency power supply for driving the pump.

The IC30 is multiplexed to improve safety. However, it is assumed that all the ICs 30 do not operate, although it is very unlikely. In this case, the decay heat of the core 12 cannot be removed, so the pressure rise in the reactor pressure vessel 13 continues.

When such a situation occurs and the pressure of the reactor pressure vessel 13 rises above the threshold, the pressure of the reactor pressure vessel 13 is transmitted to the drain valve 43 via the pressure transmission pipe 70, thereby , the drain valve 43 opens (see also FIG. 3). When the drain valve 43 is opened, the cooling water in the IC cooling water pool 31 is drained through the drain line 42 by gravity into the intermediate tank 41 which is empty during normal operation. As a result, the cooling water discharged from the IC cooling water pool 31 is stored in the intermediate tank 41 to form a water surface 41b.

Further, the pressure in the reactor pressure vessel 13 is transmitted to the pressure reducing valve 46 via the pressure transmission pipe 70, thereby opening the pressure reducing valve 46. In the present embodiment, the opening pressure of the pressure reducing valve 46 is set to be higher than the opening pressure of the drain valve 43 , so the pressure reducing valve 46 opens later than the drain valve 43 . Become.

By opening the decompression valve 46 , the steam in the reactor pressure vessel 13 is discharged to the intermediate tank 41 through the main steam pipe 14 and the decompression line 45 . As a result, the pressure in the reactor pressure vessel 13 is reduced, and high-pressure damage to the reactor pressure vessel 13 can be prevented. In the present embodiment, the end opening of the decompression line 45 is positioned below the water surface 41 b of the intermediate tank 41 . As a result, the steam discharged from the reactor pressure vessel 13 to the intermediate tank 41 is introduced into the cooling water stored in the intermediate tank 41 and condensed. It shifts to the cooling water inside. Therefore, compared with the case where the steam in the reactor pressure vessel 13 is released into the space inside the reactor containment vessel 11 as it is, the pressure rise in the reactor containment vessel 11 can be suppressed.

When the steam discharged to the intermediate tank 41 is condensed by the cooling water, most of the radioactive substances contained in the steam are captured by the cooling water in the intermediate tank 41 due to the scrubbing effect and retained in the cooling water. Therefore, even if steam is released outside the containment vessel 11 thereafter, the amount of radioactive substances released outside the containment vessel 11 can be suppressed. In this embodiment, the containment vessel 11 is not provided with a pressure suppression pool. However, the intermediate tank 41 that stores the cooling water discharged from the IC cooling water pool 31 can exhibit the same function as the pressure suppression pool.

It should be noted that when the flow rate of steam flowing into the intermediate tank 41 through the decompression line 45 is very large, the speed of pressure increase in the reactor containment vessel 11 increases. Therefore, it is preferable to design the diameter of the decompression line 45 so that the rate of decompression of the reactor pressure vessel 13 is as slow as possible. Alternatively, by providing an orifice (not shown) in the middle of the pressure reducing line 45, it is possible to restrict the steam flow rate passing through the pressure reducing line 45. Further, a configuration is also possible in which a flow rate restrictor (not shown) originally provided in the main steam pipe 14 is used to limit the flow rate of steam flowing into the intermediate tank 41 .

This embodiment uses the IC cooling water pool 31 as a water source for injecting water into the intermediate tank 41 . The decompression protection system 40 operates when the IC 30 does not operate. Therefore, substantially all of the cooling water in the IC cooling water pool 31 remains when the decompression protection system 40 is activated. By injecting the cooling water from the unused IC cooling water pool 31 into the intermediate tank 41, the cooling water can be used without waste. There is no

In this way, when the IC 30 does not operate and the pressure in the reactor pressure vessel 13 rises above the threshold value, the depressurization protection system 40 causes the pressure-increased steam in the reactor pressure vessel 13 to open the drain valve 43 and the pressure reducing valve. 46 is opened to introduce steam in the reactor pressure vessel 13 into the cooling water discharged from the IC cooling water pool 31 to the intermediate tank 41 . As a result, the reactor pressure vessel 13 is decompressed to prevent high-pressure damage of the reactor pressure vessel 13, and the pressure increase in the reactor containment vessel 11 can be suppressed.

The nuclear power plant 1 according to the present embodiment includes a depressurization protection system 40 for depressurizing the reactor pressure vessel 13 when the IC 30 is inoperative, but does not include a system for injecting water into the reactor pressure vessel 13. . The reason for this is that the pressure of the reactor pressure vessel 13 is 7 MPa or more, so if water is to be injected into the reactor pressure vessel 13 by gravity, the water source must be placed at a position higher than the reactor pressure vessel 13 by 700 m or more. Because it is unrealistic.

Therefore, if the IC 30 does not operate, the core 12 may melt due to decay heat without being cooled. The molten core melts and damages the lower portion of the reactor pressure vessel 13 . When the lower portion of the reactor pressure vessel 13 is damaged, the molten core drops and spreads on the floor surface 11a of the reactor containment vessel 11, raising the ambient temperature of the reactor containment vessel 11.

When the temperature of the atmosphere in the containment vessel 11 becomes abnormally high due to the thermal energy of the molten core, the melting valve 48 opens. By opening the melting valve 48 , the cooling water discharged and stored in the intermediate tank 41 is discharged to the molten core on the floor 11 a of the containment vessel 11 through the floor water injection line 47 . This cooling water cools the molten core, and the severe accident ends. In this way, even if the IC 30 does not operate, the melt valve 48 is opened without any operation by the operator, and the cooling water is injected into the molten core by its own weight without using any dynamic equipment, thereby converging the accident. can be made

As described above, the safety system of the nuclear power plant 1 according to the first embodiment cools and condenses the steam from the reactor pressure vessel 13 stored in the reactor containment vessel 11, The IC 30 is provided with an IC 30 that returns to the reactor containment vessel 11, and an IC cooling water pool 31 of the IC 30 as a water source for storing cooling water installed outside the reactor containment vessel 11, and an IC An intermediate tank 41 as a storage unit positioned below the cooling water pool 31 (water source) and capable of receiving and storing cooling water discharged from the IC cooling water pool 31 (water source), and the IC cooling water pool. 31 (water source) to lead the cooling water of the IC cooling water pool 31 (water source) to the intermediate tank 41 (reservoir), and provided on the drain line 42 (first line) A drain valve 43 (first valve) that switches the drain line 42 (first line) to an open state or a closed state, one side of which is indirectly connected to the reactor pressure vessel 13, and the other side of which is connected to the IC cooling water The pressure reduction line 45 (second line) that opens at a position lower than the assumed water level 41a when the cooling water from the pool 31 (water source) is stored in the intermediate tank 41 (storage section), and the pressure reduction line 45 (second line) ) and a pressure reducing valve 46 (second valve) for switching the pressure reducing line 45 (second line) between an open state and a closed state. The drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are configured to open according to the height of the pressure inside the reactor pressure vessel 13 .

According to this configuration, even if the pressure in the reactor pressure vessel 13 deviates from the normal range and rises due to non-operation of the IC 30, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are opened. As a result, the cooling water discharged from the IC cooling water pool 31 (water source) to the intermediate tank 41 (reservoir) is introduced with steam from the reactor pressure vessel 13 and condensed. The reactor pressure vessel 13 can be depressurized without providing a pressure suppression pool. That is, the structure of the reactor containment vessel 11 can be simplified, and the reactor pressure vessel 13 can be depressurized without using dynamic equipment even when the IC 30 is inoperative.

Further, in the present embodiment, the IC 30 includes an IC cooling water pool 31 that stores cooling water for cooling the steam from the reactor pressure vessel 13, and the IC cooling water pool 31 also serves as the water source described above. . According to this configuration, since it is not necessary to separately install a cooling water tank as a water source of the decompression protection system 40 that stores cooling water to be discharged to the intermediate tank 41 in advance, the configuration of the safety system of the nuclear power plant 1 can be simplified. can be

Also, in the present embodiment, the above-described storage section is the intermediate tank 41 (tank) installed inside the reactor containment vessel 11 . According to this configuration, it is possible to easily secure the reservoir in the containment vessel 11 .

Furthermore, in this embodiment, the intermediate tank 41 is arranged at a position away from the reactor pressure vessel 13 . According to this configuration, the intermediate tank 41 can be arranged in an area around the reactor pressure vessel 13 where a large number of devices are arranged.

Further, the safety system of the nuclear power plant 1 according to the present embodiment is connected to the intermediate tank 41 and discharges the cooling water discharged from the IC cooling water pool 31 (water source) to the intermediate tank 41 to the floor surface 11a of the reactor containment vessel 11. and a melting valve 48 (third valve ). The melting valve 48 (third valve) is configured to open upon receiving heat from the surroundings of the melting valve 48 (third valve).

According to this configuration, even if the molten core spreads above the floor surface 11a of the containment vessel 11, the heat of the molten core opens the melting valve 48 without the operator's operation, and the intermediate tank 41 The accident can be resolved by injecting water into the molten core using the weight of the stored cooling water without using dynamic equipment.

Further, in the present embodiment, the pressure at which the pressure reducing valve 46 (second valve) opens is set to be higher than the pressure at which the drain valve 43 (first valve) opens. According to this configuration, after the drain valve 43 (first valve) is opened and the cooling water from the IC cooling water pool 31 is stored in the intermediate tank 41, the pressure reducing valve 46 (second valve) is opened. Therefore, the steam in the reactor pressure vessel 13 can be reliably introduced into the cooling water in the intermediate tank 41 and condensed. Therefore, since the energy of the steam in the reactor pressure vessel 13 is transferred to the cooling water, the pressure rise in the reactor containment vessel 11 can be reliably suppressed.

Further, in the present embodiment, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are configured to open using the pressure of the steam generated in the reactor pressure vessel 13. there is According to this configuration, when the steam pressure in the reactor pressure vessel 13 rises due to the non-operation of the IC 30, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are operated without the operator's operation. can be automatically opened.

Further, in the present embodiment, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are supplied with the steam generated in the reactor pressure vessel through the pressure transmission pipe 70, thereby It is designed to be directly actuated by pressure. According to this configuration, if the pressure transmission pipe 70 is used as a valve driving system for driving the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) using the steam in the reactor pressure vessel 13, Therefore, the valve drive system can be configured simply.

In addition, the safety system of the nuclear power plant 1 according to the present embodiment is provided on the drain line 42 (first line) and allows the flow toward the intermediate tank 41 (reservoir), while the IC cooling water pool 31 ( There is also a check valve 44 that prevents flow towards the water source. According to this configuration, it is possible to prevent the gas inside the reactor containment vessel 11 from being discharged to the outside of the reactor containment vessel 11 via the drain line 42 .

[Second embodiment]
Next, a second embodiment of a safety system for a nuclear power plant according to the present invention will be described with reference to FIG. FIG. 7 is a schematic system diagram showing a nuclear power plant equipped with a second embodiment of the nuclear power plant safety system of the present invention. In FIG. 7, parts having the same reference numerals as those shown in FIGS. 1 to 6 are the same parts, so detailed description thereof will be omitted.

The safety system of the nuclear power plant according to the second embodiment of the present invention shown in FIG. Instead of the intermediate tank 41 of the depressurization protection system 40 of the first embodiment, the bottom of the containment vessel 11 including the floor surface 11a is used as the reservoir of 40A. The depressurization protection system 40A of the present embodiment discharges the cooling water of the IC cooling water pool 31 directly to the floor surface 11a of the reactor containment vessel 11, and stores the discharged cooling water at the bottom of the reactor containment vessel 11. Let

Specifically, the depressurization protection system 40A includes an IC cooling water pool 31 as a water source similar to that of the first embodiment, and an IC cooling water pool 31 extending from the IC cooling water pool 31 to the vicinity of the floor surface 11a of the reactor containment vessel 11. a drain line 42A, a drain valve 43 and a check valve 44 similar to those in the first embodiment arranged on the drain line 42A, and a main steam pipe 14 branched from the floor surface 11a of the reactor containment vessel 11. and a pressure reducing valve 46 similar to that of the first embodiment installed on the pressure reducing line 45A. The drain line 42A directly injects at least part of the cooling water stored in the IC cooling water pool 31 to the floor surface 11 a of the reactor containment vessel 11 . The decompression line 45A is configured to open at a position lower than the assumed water level 11b when the cooling water from the IC cooling water pool 31 is stored in the bottom of the reactor containment vessel 11 . That is, the decompression line 45A introduces the steam inside the reactor pressure vessel 13 into the cooling water from the IC cooling water pool 31 stored at the bottom of the reactor containment vessel 11 .

In this embodiment, when the ICs 30 of all systems do not operate, the pressure of the reactor pressure vessel 13 is transmitted to the drain valve 43 through the pressure transmission pipe 70, as in the first embodiment. As a result, the drain valve 43 is opened. By opening the drain valve 43, the cooling water in the IC cooling water pool 31 is discharged directly onto the floor surface 11a of the reactor containment vessel 11 through the drain line 42A, and flows from the IC cooling water pool 31 to the bottom of the reactor containment vessel 11. The discharged cooling water is stored.

Furthermore, as in the first embodiment, the pressure of the reactor pressure vessel 13 is transmitted via the pressure transmission pipe 70, so that the pressure reducing valve 46 opens later than the drain valve 43. By opening the decompression valve 46, the steam in the reactor pressure vessel 13 is introduced through the decompression line 45A into the cooling water stored in the bottom of the containment vessel 11 and condensed. is transferred to the cooling water. As a result, the reactor pressure vessel 13 is decompressed to prevent high-pressure damage of the reactor pressure vessel 13, and the pressure increase in the reactor containment vessel 11 can be suppressed. Also, most of the radioactive substances contained in the steam are captured by the scrubbing effect of the cooling water stored at the bottom of the containment vessel 11 and retained in the cooling water.

In the present embodiment, cooling water is spread over the floor surface 11a of the reactor containment vessel 11 before core meltdown occurs. Therefore, when a core meltdown occurs, the molten core falls into the cooling water that has already spread over the floor surface 11a, so that it is atomized and solidified into granules. Since the atomized molten core has an increased contact area with cooling water and is efficiently cooled, a severe accident can be contained more quickly.

In the present embodiment, the decompression line 45A is configured to open below the surface of the cooling water stored in the bottom of the reactor containment vessel 11 (position lower than the assumed water level 11b). Therefore, when the depressurization protection system 40A is activated, the steam in the reactor pressure vessel 13 is blown into the cooling water stored in the bottom of the reactor containment vessel 11, resulting in a large number of air bubbles (also called voids) in the cooling water. ) is included. It is known that when voids are contained in the water, the risk of a steam explosion due to the molten core falling into the cooling water can be reduced.

In the present embodiment, the water level of the cooling water drained from the IC cooling water pool 31 to the floor surface 11 a of the reactor containment vessel 11 is set to reach the bottom surface of the reactor pressure vessel 13 . By setting the amount, it becomes possible to directly cool the bottom of the reactor pressure vessel 13 from the outside with the cooling water discharged from the IC cooling water pool 31 when the depressurization protection system 40A is activated. In this case, even if a core meltdown occurs, the molten core can be cooled while remaining inside the reactor pressure vessel 13, and the molten core can be severely cooled without falling onto the floor surface 11a of the containment vessel 11. accidents can be brought to an end. Therefore, post-accident treatment such as removal of molten fuel is facilitated.

In the safety system of the nuclear power plant according to the second embodiment described above, as in the case of the first embodiment, the pressure in the reactor pressure vessel 13 deviates from the normal range due to the non-operation of the IC 30. Even if it rises, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are opened, so that the water flows from the IC cooling water pool 31 (water source) to the bottom (reservoir) of the reactor containment vessel 11. Since steam from the reactor pressure vessel 13 is introduced into the discharged cooling water and condensed, the reactor pressure vessel 13 can be depressurized without providing a pressure suppression pool in the reactor containment vessel 11 . That is, the structure of the reactor containment vessel 11 can be simplified, and the reactor pressure vessel 13 can be depressurized without using dynamic equipment even when the IC 30 is inoperative.

In addition, in the present embodiment, the above-described storage section is the bottom section including the floor surface 11a of the containment vessel 11 . According to this configuration, the decompression protection system 40A of the present embodiment has a configuration in which the intermediate tank 41 is omitted from the configuration of the decompression protection system 40 of the first embodiment. By effectively utilizing the space occupied by the intermediate tank 41, the size of the reactor containment vessel 11 can be reduced.

[Third embodiment]
Next, a third embodiment of a safety system for a nuclear power plant according to the present invention will be described with reference to FIG. FIG. 8 is a schematic system diagram showing a nuclear power plant equipped with a nuclear power plant safety system according to a third embodiment of the present invention. In FIG. 8, parts having the same reference numerals as those shown in FIGS. 1 to 7 are the same parts, and detailed description thereof will be omitted.

The third embodiment of the nuclear plant safety system of the present invention shown in FIG. Instead of the intermediate tank 41 of the depressurization protection system 40 of the first embodiment, a pressure vessel cooling tank 41B is installed in the area where the bottom of the reactor pressure vessel 13 is located as a reservoir. The depressurization protection system 40B of the present embodiment discharges the cooling water from the IC cooling water pool 31 to the pressure vessel cooling tank 41B, and the cooling water from the IC cooling water pool 31 stored in the pressure vessel cooling tank 41B reduces the reactor pressure. It is configured to directly cool the bottom of the container 13 from the outside.

Specifically, the depressurization protection system 40B includes a pressure vessel cooling tank 41B arranged in the reactor containment vessel 11, a drain line 42B connecting the IC cooling water pool 31 and the pressure vessel cooling tank 41B, and a drain line 42B. The same drain valve 43 and check valve 44 as in the above first embodiment, the pressure reduction line 45B branched from the main steam pipe 14 and connected to the pressure vessel cooling tank 41B, and the first and a pressure reducing valve 46 similar to the embodiment of . The pressure vessel cooling tank 41B stores the cooling water discharged from the IC cooling water pool 31 as a water source. is positioned below the surface of the cooling water. The drain line 42B guides at least part of the cooling water stored in the IC cooling water pool 31 to the pressure vessel cooling tank 41B. The decompression line 45B is configured to open at a position lower than the assumed water level 41a when the cooling water from the IC cooling water pool 31 is stored in the pressure vessel cooling tank 41B. That is, the decompression line 45B introduces the steam inside the reactor pressure vessel 13 into the cooling water from the IC cooling water pool 31 stored in the pressure vessel cooling tank.

In this embodiment, when the ICs 30 of all systems do not operate, the drain valve 43 is opened by the pressure of the reactor pressure vessel 13, as in the first embodiment. By opening the drain valve 43, the cooling water in the IC cooling water pool 31 is drained through the drain line 42B into the pressure vessel cooling tank 41B, and the cooling water discharged from the IC cooling water pool 31 is stored in the pressure vessel cooling tank 41B. be.

Furthermore, as in the case of the first embodiment, the pressure in the reactor pressure vessel 13 causes the pressure reducing valve 46 to open later than the drain valve 43 . By opening the decompression valve 46, the steam in the reactor pressure vessel 13 is introduced into the cooling water stored in the pressure vessel cooling tank 41B through the decompression line 45B and is condensed. energy is transferred to the cooling water. As a result, the reactor pressure vessel 13 is decompressed to prevent high-pressure damage of the reactor pressure vessel 13, and the pressure increase in the reactor containment vessel 11 can be suppressed. Also, most of the radioactive substances contained in the steam are captured by the scrubbing effect of the cooling water in the pressure vessel cooling tank 41B and retained in the cooling water.

In this embodiment, the pressure vessel cooling tank 41B is arranged in the area where the bottom of the reactor pressure vessel 13 is located. Therefore, even if a core meltdown occurs and the molten core falls to the bottom of the reactor pressure vessel 13, the depressurization protection system 40B is already operating, so the reactor pressure is maintained by the cooling water stored in the pressure vessel cooling tank 41B. The molten core that collects at the bottom of vessel 13 can be cooled from the outside. Therefore, the severe accident can be brought to an end while the molten reactor core remains in the reactor pressure vessel 13 without falling onto the floor 11a of the containment vessel 11. becomes easier.

In addition, in the present embodiment, before the molten core drops to the bottom of the reactor pressure vessel 13, the cooling water stored in the pressure vessel cooling tank 41B is discharged from the reactor pressure vessel 13 through the decompression line 45B. It is heated by the released steam. Therefore, when the molten core falls to the bottom of the reactor pressure vessel 13, the already heated cooling water in the pressure vessel cooling tank 41B quickly boils. Therefore, the cooling water in the pressure vessel cooling tank 41B can efficiently cool the bottom of the reactor pressure vessel 13 from the outside by boiling heat transfer.

In the safety system of the nuclear power plant according to the third embodiment described above, as in the case of the first embodiment, the pressure in the reactor pressure vessel 13 deviates from the normal range due to the non-operation of the IC 30. Even if it rises, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are opened, so that the IC cooling water pool 31 (water source) is discharged to the pressure vessel cooling tank 41B (reservoir). Since steam from the reactor pressure vessel 13 is introduced into the cooled water and condensed, the reactor pressure vessel 13 can be depressurized without providing a pressure suppression pool in the reactor containment vessel 11 . That is, the structure of the reactor containment vessel 11 can be simplified, and the reactor pressure vessel 13 can be depressurized without using dynamic equipment even when the IC 30 is inoperative.

Further, in the present embodiment, when the pressure vessel cooling tank 41B stores cooling water from the IC cooling water pool 31 (water source), the bottom of the reactor pressure vessel 13 is positioned below the surface of the cooling water. are placed in According to this configuration, when the depressurization protection system 40B is activated due to the inactivation of the IC 30, the cooling water discharged from the IC cooling water pool 31 (water source) and stored in the pressure vessel cooling tank 41B is used to cool the reactor pressure vessel 13. The bottom can be cooled externally.

[Fourth embodiment]
Next, a fourth embodiment of a safety system for a nuclear power plant according to the present invention will be described with reference to FIG. FIG. 9 is a schematic system diagram showing a nuclear power plant equipped with a nuclear power plant safety system according to a fourth embodiment of the present invention. In FIG. 9, parts having the same reference numerals as those shown in FIGS. 1 to 8 are the same parts, and detailed description thereof will be omitted.

The fourth embodiment of the nuclear plant safety system of the present invention shown in FIG. 9 differs from the first embodiment in that the drain valve 43C and check valve 44C of the decompression protection system 40C is located outside the Specifically, the drain line 42C of the depressurization protection system 40C extends from the bottom side of the side wall of the IC cooling water pool 31 to the outside of the containment vessel 11 and then to the intermediate tank 41 inside the containment vessel 11. exist. The drain valve 43C and the check valve 44C are provided at a portion of the drain line 42C that extends outside the containment vessel 11 . Since the drain valve 43C is arranged outside the containment vessel 11 , a portion of the pressure transmission pipe 70C for driving the drain valve 43C extends to the outside of the containment vessel 11 . Other configurations and structures are similar to those of the first embodiment.

In the nuclear plant safety system according to the fourth embodiment described above, as in the case of the first embodiment, the structure of the reactor containment vessel 11 can be simplified, and the IC 30 is unnecessary. Even in operation, the reactor pressure vessel 13 can be depressurized without the use of dynamic equipment.

In this embodiment, the drain valve 43C (first valve) is arranged outside the reactor containment vessel 11 . According to this configuration, access to the drain valve 43C (first valve) is easier than in the case of the first embodiment in which the drain valve 43 (first valve) is arranged inside the reactor containment vessel 11. easier. Therefore, the drain valve 43C (first valve) can be opened by an operator's operation, and maintenance of the drain valve 43C (first valve) is facilitated.

[Fifth embodiment]
Next, a fifth embodiment of the nuclear plant safety system of the present invention will be described with reference to FIG. FIG. 10 is a schematic system diagram showing a nuclear plant equipped with a nuclear plant safety system according to a fifth embodiment of the present invention. In FIG. 10, parts having the same reference numerals as those shown in FIGS. 1 to 9 are the same parts, so detailed description thereof will be omitted.

The fifth embodiment of the safety system for a nuclear power plant of the present invention shown in FIG. A cooling water storage tank 49 is separately provided instead of the IC cooling water pool 31 as a water source for 40D. The depressurization protection system 40D of the present embodiment discharges the cooling water in the cooling water storage tank 49 to the intermediate tank 41 , and the cooling water from the cooling water storage tank 49 stored in the intermediate tank 41 is used to restore steam in the reactor pressure vessel 13 . is condensed. Specifically, the cooling water storage tank 49 of the depressurization protection system 40D is installed at a position higher than the intermediate tank 41 outside the reactor containment vessel 11 . The drain line 42D connects the cooling water storage tank 49 and the intermediate tank 41 and guides the cooling water in the cooling water storage tank 49 to the intermediate tank 41 . Other configurations of the reduced pressure protection system 40D are the same as those of the first embodiment.

In the present embodiment, when the ICs 30 of all systems do not operate, the pressure of the reactor pressure vessel 13 causes the drain valve 43 to open, and The stored cooling water is drained to the intermediate tank 41 through the drain line 42D, and the cooling water discharged from the cooling water storage tank 49 is stored in the intermediate tank 41. FIG.

Furthermore, as in the case of the first embodiment, the pressure in the reactor pressure vessel 13 causes the pressure reducing valve 46 to open later than the drain valve 43 , and the steam in the reactor pressure vessel 13 flows through the pressure reducing line 45 . It is introduced into the cooling water stored in the intermediate tank 41 through which it condenses. As a result, the reactor pressure vessel 13 is decompressed to prevent high-pressure damage of the reactor pressure vessel 13, and the pressure increase in the reactor containment vessel 11 can be suppressed.

In the safety system of the nuclear power plant according to the fifth embodiment described above, as in the case of the first embodiment, the pressure in the reactor pressure vessel 13 deviates from the normal range due to the non-operation of the IC 30. Even if it rises, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are opened, so that the cooling water discharged from the cooling water storage tank 49 (water source) to the intermediate tank 41 (storage section) Since steam from the reactor pressure vessel 13 is introduced into the water and condensed, the reactor pressure vessel 13 can be depressurized without providing a pressure suppression pool in the reactor containment vessel 11 . That is, the structure of the reactor containment vessel 11 can be simplified, and the reactor pressure vessel 13 can be depressurized without using dynamic equipment even when the IC 30 is inoperative.

[Modification of valve drive system for pressure reducing valve]
Next, the configuration of a modification of the valve drive system for driving the pressure reducing valves constituting a part of the first to fifth embodiments of the nuclear plant safety system of the present invention will be described with reference to FIG. . FIG. 11 is a block diagram showing a modification of the valve drive system for driving the pressure reducing valve, which constitutes a part of the first to fifth embodiments of the nuclear plant safety system of the present invention. In FIG. 11, parts having the same reference numerals as those shown in FIGS. 1 to 10 are the same parts, and detailed description thereof will be omitted.

The modified example of the valve drive system for the pressure reducing valve 46 shown in FIG. Instead of the high-pressure steam from the reactor pressure vessel 13, a pressure source that supplies a high-pressure gas different from the high-pressure steam in the reactor pressure vessel 13 is used. In the valve drive system of the pressure reducing valve 46 of the first to fifth embodiments, the pressure of the reactor pressure vessel 13 is controlled by the pressure reducing valve 46 via the pressure transmission pipe 70 directly connected to the reactor pressure vessel 13. is configured to be transmitted to the valve opening/closing mechanism 54 (see FIGS. 2 and 3). Therefore, it may become difficult to arrange the piping from the reactor pressure vessel 13 to the pressure reducing valve 46 . Therefore, in the valve drive system 70E1 of this modified example, a pressure source that can be arranged in the vicinity of the pressure reducing valve 46 is separately installed.

The pressure reducing valve 46 is composed of a gas-actuated valve that is operated by a gas such as air or nitrogen. It is operated using a pressure source different from the steam in the reactor pressure vessel 13 when it rises. Specifically, the pressure reducing valve driving system 70E1 includes a high-pressure gas generator 71 that generates a high-pressure gas G (air, nitrogen, etc.) having a pressure equal to or higher than a first predetermined value, and a high-pressure gas G generated by the high-pressure gas generator 71. A gas pressure accumulator 72 that accumulates pressure, a breakable rupture disk 73, a fluid pressure converter 74 that breaks the rupture disk 73 according to the input pressure, and a switching that switches the flow path according to the pressure on the upstream side. A valve 75 is provided.

The high pressure gas generator 71 is connected to the primary side of the fluid pressure converter 74 via the first supply line 81 . The gas pressure accumulator 72 is connected to the primary side of the fluid pressure converter 74 and the high pressure gas generator 71 via a second supply line 82 connected to the first supply line 81. For example, a cylinder can be used. . A first check valve 76 and a second check valve 77 are provided upstream and downstream of the connection point with the second supply line 82 on the first supply line 81 . The primary side of the fluid pressure converter 74 is also connected via a third supply line 83 to the valve opening/closing mechanism 54 (see FIGS. 2 and 3) of the pressure reducing valve 46 . The fluid pressure converter 74 communicates between the second check valve 77 and the rupture disk 73 via the primary side. The high-pressure gas generator 71 and the gas pressure accumulator 72 supply a high-pressure gas G of a first predetermined value or higher to the valve opening/closing mechanism 54 of the pressure reducing valve 46 via the first supply line 81, the second supply line 82, and the third supply line 83. (see FIGS. 2 and 3).

The secondary side of the fluid pressure converter 74 is connected to the reactor pressure vessel 13 via a bleed line 84 connected to the pressure reducing line 45 . The bleed line 84 introduces the steam from the reactor pressure vessel 13 supplied to the decompression line 45 to the fluid pressure converter 74 . The bleed line 84 can be connected to the decompression line 45 in the vicinity of the installation position of the decompression valve 46, and the routing of the piping up to the fluid pressure converter 74 is the pressure transmission of the decompression protection system 40 of the first embodiment. Easier than with tube 70 . In the fluid pressure converter 74, the pressure of the fluid F1 input to the secondary side through the bleed line 84 reaches the second threshold value (the same value as the valve opening pressure of the pressure reducing valve 46 in the first to fifth embodiments). When exceeded, the rupture disk 73 is broken by the gas from the high-pressure gas generator 71 or the gas pressure accumulator 72 . The switching valve 75 is installed on the third supply line 83 . When gas having a pressure equal to or higher than a second predetermined value flows into the third supply line 83 on the downstream side of the rupture disk 73, the switching valve 75 switches the flow path to allow the third supply line 83 to communicate with the gas. In this case, the third supply line 83 is cut off. The second predetermined value which is the switching pressure of the switching valve 75 is set to a pressure sufficiently lower than the first predetermined value of the high pressure gas G generated by the high pressure gas generator 71 .

Next, the operation of the modification of the pressure reducing valve driving system will be explained using FIG. FIG. 12 is a block diagram showing a state of the pressure reducing valve operating (opening) in the modification of the pressure reducing valve drive system shown in FIG. In FIG. 12, the shape of the rupture disk schematically shows that it is in a fractured state.

When the IC 30 (see FIG. 1) is operating, the removal of decay heat from the core 12 continues, so the pressure in the reactor pressure vessel 13 will not rise abnormally. In this case, even if the pressure of the fluid F1 (steam) supplied from the reactor pressure vessel 13 to the decompression line 45 is input to the secondary side of the fluid pressure converter 74 via the extraction line 84, as shown in FIG. Moreover, the rupture disk 73 is not broken. If the normal state of the rupture disk 73 is maintained, the rupture disk 73 blocks the supply of the high pressure gas G from the high pressure gas generator 71 and the gas pressure accumulator 72 to the pressure reducing valve 46 . Therefore, when the IC 30 is operating, the pressure reducing valve 46 will not operate.

On the other hand, when the ICs 30 of all systems do not operate and the pressure of the reactor pressure vessel 13 exceeds the second threshold value, the second pressure of the fluid F1 (steam) supplied from the reactor pressure vessel 13 to the extraction line 84 When the pressure exceeding the threshold is input to the secondary side of the fluid pressure converter 74, as shown in FIG. The disk 73 is acted upon and fractured. When the rupture disk 73 is broken, the high-pressure gas G from the high-pressure gas generator 71 or the gas pressure accumulator 72 flows into the third supply line 83, and the switching valve 75 is switched so that the third supply line 83 is communicated. By switching the switching valve 75, the high-pressure gas G is supplied to the valve opening/closing mechanism 54 (see FIGS. 2 and 3) of the pressure reducing valve 46, and the pressure reducing valve 46 is opened. By opening the decompression valve 46 to open the decompression line 45, the steam in the reactor pressure vessel 13 is released into the cooling water in the intermediate tank 41 through the decompression line 45, and the reactor pressure vessel 13 is decompressed. be.

Here, it is assumed that after the rupture disk 73 is broken, the pressure of the fluid F1 supplied from the reactor pressure vessel 13 drops below the second threshold due to activation of the pressure reducing valve 46 . In this case, in the pressure reducing valve drive system 70E1, the rupture disk 73 has already broken, so the supply of the high pressure gas G by the high pressure gas generator 71 is continued unless power loss occurs. Moreover, even when power supply is lost, the supply of the high-pressure gas G from the gas pressure accumulator 72 is continued. Therefore, the communication state of the third supply line 83 is maintained by switching the flow path of the switching valve 75, so that the pressure reducing valve 46 is maintained in the open state. Therefore, the steam from the reactor pressure vessel 13 continues to be released into the cooling water in the intermediate tank 41, and pressure rise in the reactor pressure vessel 13 can be suppressed.

It should be noted that in the pressure reducing valve drive system 70E1 of this modified example, the high pressure gas G is accumulated in the gas pressure accumulator 72 . Therefore, even if the pressure reducing valve drive system 70E1 loses power, the supply of the high pressure gas G to the pressure reducing valve 46 can be maintained for a period of time corresponding to the volume of the gas pressure accumulator 72 .

As described above, in this modification, the pressure reducing valve 46 (second valve) is configured to operate when gas having a pressure equal to or higher than the first predetermined value (predetermined value) is supplied from the valve drive system 70E1. It is. The valve drive system 70E1 includes a high-pressure gas generator 71 and a gas pressure accumulator 72 as gas supply sources that supply gas having a pressure equal to or higher than a first predetermined value (predetermined value), and a high-pressure gas generator 71 and a gas pressure accumulator 72 (

supply line

81, 82, 83 for guiding the gas from the gas supply source) to the pressure reducing valve 46 (second valve), a rupture disk 73 provided to close the supply line 83, and the gas from the reactor pressure vessel 13 When steam is introduced and the pressure of the steam exceeds a second threshold (threshold value), a fluid pressure converter 74 as a rupture operation unit that ruptures the rupture disk 73, and pressure reduction from the rupture disk 73 on the

supply lines

81, 82, 83 Provided on the valve 46 (second valve) side, when the gas supplied from the high-pressure gas generator 71 or the gas pressure accumulator 72 (gas supply source) flows downstream from the rupture disk 73, the third supply line 83 is shut off. and a switching valve 75 for switching from the communication state to the communication state.

According to this configuration, the high pressure gas generator 71 and the gas pressure accumulator 72 (gas supply source) for driving the pressure reducing valve 46 (second valve) can be arranged in the vicinity of the pressure reducing valve 46 (second valve). , the degree of freedom in routing of piping (supply line) for supplying pressure to the pressure reducing valve 46 (second valve) can be increased.

[Modified Example of Valve Drive System for Drain Valve]
Next, a modified example of the valve drive system for driving the drain valve, which constitutes a part of the first to fifth embodiments of the nuclear plant safety system of the present invention, will be described with reference to FIGS. 13 and 14. do. FIG. 13 is a block diagram showing a modification of the valve drive system for driving the drain valves, which constitutes a part of the first to fifth embodiments of the nuclear plant safety system of the present invention. FIG. 14 is a block diagram showing a state of the drain valve operating (opening) in the modification of the drain valve driving system shown in FIG. 13 and 14, the parts having the same reference numerals as those shown in FIGS. 1 to 12 are the same parts, and detailed description thereof will be omitted. In FIG. 14, the shape of the rupture disk schematically shows that it is in a fractured state.

The modification of the valve drive system for the drain valve 43 shown in FIG. Instead of the steam from the vessel 13, a pressure source that supplies a high pressure gas different from the high pressure steam in the reactor pressure vessel 13 is used. The drain valve driving system 70E2 that drives the drain valve 43 has the same configuration as the pressure reducing valve driving system 70E1, and includes a pipe (drain line 42) in which the drain valve 43 is installed and a pipe (drain line 42) in which the pressure reducing valve 46 is installed. Only part of the configuration is different due to the fact that the decompression line 45) is different.

Specifically, the drain valve drive system 70E2 includes a high-pressure gas generator 71, a gas pressure accumulator 72, a rupture disk 73, a fluid pressure converter 74, and a switching valve 75, similar to the pressure reducing valve drive system 70E1. The secondary side of the fluid pressure converter 74 is connected to the reactor pressure vessel 13 via a bleed line 84E2 connected to the main steam pipe 14 or the reduced pressure line 45 . In the fluid pressure converter 74, the pressure of the fluid F2 input to the secondary side through the bleed line 84E2 reaches the first threshold value (the same value as the opening pressure of the drain valve 43 in the first to fifth embodiments). When exceeded, the rupture disk 73 is broken by the gas from the high-pressure gas generator 71 or the gas pressure accumulator 72 . The steam bleed line 84E2 introduces steam from the reactor pressure vessel 13 supplied to the main steam pipe 14 or the decompression line 45 to the fluid pressure converter 74 . The extraction line 84E2 can be connected to a portion of the main steam pipe 14 or the decompression line 45 near the installation position of the drain valve 43, and the routing of the piping up to the fluid pressure converter 74 is similar to that of the first embodiment. This is easier than with the pressure transmission tube 70 of the decompression protection system 40 . The third supply line 83E2 is connected to the valve opening/closing mechanism 54 of the drain valve 43 (see FIGS. 2 and 3).

When the ICs 30 of all systems do not operate and the pressure of the reactor pressure vessel 13 rises above the first threshold, as shown in FIG. Since the pressure of the fluid F2 (steam) that is being pumped exceeds the first threshold is input to the secondary side of the fluid pressure converter 74 via the bleed line 84E2, the rupture disk 73 ruptures. By breaking the rupture disk 73, the high-pressure gas G from the high-pressure gas generator 71 or the gas pressure accumulator 72 flows into the third supply line 83E2, and the flow path of the switching valve 75 is switched so that the third supply line 83E2 is communicated. be done. By switching the switching valve 75, the high-pressure gas G is supplied to the valve opening/closing mechanism 54 (see FIGS. 2 and 3) of the drain valve 43, and the drain valve 43 is opened. By opening the drain valve 43 and connecting the drain line 42 , the cooling water in the IC cooling water pool 31 or the cooling water storage tank 49 is discharged through the drain line 42 .

As described above, in the present modification, the drain valve 43 (first valve) is configured to operate when gas having a pressure equal to or higher than the first predetermined value (predetermined value) is supplied from the valve drive system 70E2. It is a thing. The valve driving system 70E2 includes a high-pressure gas generator 71 and a gas pressure accumulator 72 as gas supply sources that supply gas having a pressure equal to or higher than a first predetermined value (predetermined value), and a high-pressure gas generator 71 and a gas pressure accumulator 72 ( gas supply source) to the drain valve 43 (first valve), a rupture disk 73 provided to close the supply line 83E2, A fluid pressure converter 74 as a breaking operation unit that breaks the rupture disk 73 when steam is introduced and the pressure of the steam exceeds a first threshold (threshold value), and

supply lines

81, 82, 83E2 than the rupture disk 73. Provided on the drain valve 43 (first valve) side, the third supply line 83E2 is cut off when the gas supplied from the high-pressure gas generator 71 or the gas pressure accumulator 72 (gas supply source) flows downstream from the rupture disk 73. and a switching valve 75 for switching from the state to the communication state.

According to this configuration, the high-pressure gas generator 71 and the gas pressure accumulator 72 (gas supply source) for driving the drain valve 43 (first valve) can be arranged in the vicinity of the drain valve 43 (first valve). , the degree of freedom in handling of the piping (supply line) for supplying pressure to the drain valve 43 (first valve) can be increased.

[others]
In addition, in the first to fifth embodiments described above, an example in which the present invention is applied to a boiling water reactor has been shown, but the present invention can also be applied to a pressurized water reactor (PWR). . An embodiment applied to a pressurized water reactor will be described with reference to FIG. FIG. 15 is a schematic system diagram showing a pressurized water nuclear plant equipped with an embodiment of the nuclear plant safety system of the present invention. In FIG. 15, parts having the same reference numerals as those shown in FIGS. 1 to 14 are the same parts, so detailed description thereof will be omitted.

In FIG. 15, a reactor pressure vessel 23 containing a core 12 and a steam generator 24 for generating steam are installed in the reactor containment vessel 11F of the pressurized water nuclear power plant 1F. The reactor pressure vessel 23 and the steam generator 24 are connected so that cooling water circulates.

The IC30F as a safety system of the pressurized water type nuclear power plant 1F condenses the steam from the steam generator 24 by cooling and returns it to the steam generator 24 again. The components of IC30F are the same as those of IC30 of the boiling water nuclear power plant 1 . However, the IC steam supply line 33 connects the inlet (upper side) of the IC heat exchanger 32 and the upper part of the steam generator 24 (gas phase portion 24b). The IC return line 34 connects the outlet (lower side) of the IC heat exchanger 32 and the lower portion of the steam generator 24 (liquid phase portion 24a).

A decompression protection system 40F as a safety system of the pressurized water nuclear power plant 1F depressurizes the steam generator 24 when the IC 30F does not operate and the pressure inside the steam generator 24 rises outside the normal range. and protects the steam generator 24 with the steam generator 24, and is configured to be activated using the steam whose pressure has increased. Components of the depressurization protection system 40F are the same as those of the depressurization protection system 40 of the boiling water nuclear power plant 1 . However, the decompression line 45 introduces part of the steam in the steam generator 24 into the cooling water stored in the intermediate tank 41 . Also, the drain valve 43 and the pressure reducing valve 46 are configured to open using the steam pressure of the steam generator 24 . One side of the pressure transmission pipe 70 is connected to the upper portion of the steam generator 24 (gas phase portion 24b). The operation of the depressurization protection system 40F is similar to that of the depressurization protection system 40 of the boiling water nuclear power plant 1 . Therefore, the depressurization protection system 40F of the pressurized water nuclear power plant 1F can also obtain the same effects as the depressurization protection system 40 of the boiling water nuclear plant 1.

As described above, the safety system of the nuclear power plant 1F according to the present embodiment applied to the PWR condenses the steam from the steam generator 24 stored in the reactor containment vessel 11F by cooling and condenses the steam generator 24 again. It is equipped with an IC 30F that returns to the reactor containment vessel 11F, is installed outside the reactor containment vessel 11F, and is located inside the IC 30F IC cooling water pool 31 and the reactor containment vessel 11F as a water source for storing cooling water. An intermediate tank 41 as a storage unit positioned below the IC cooling water pool 31 (water source) and capable of receiving and storing the cooling water discharged from the IC cooling water pool 31 (water source), and the IC cooling water. A drain line 42 (first line) that is connected to the pool 31 (water source) and guides the cooling water of the IC cooling water pool 31 (water source) to the intermediate tank 41 (reservoir), and on the drain line 42 (first line) A drain valve 43 (first valve) is provided to switch the drain line 42 (first line) to an open state or a closed state, and one side is directly or indirectly connected to the steam generator 24, and the other side is connected to the IC A pressure reduction line 45 (second line) that opens at a position lower than the assumed water level 41a when the cooling water from the cooling water pool 31 (water source) is stored in the intermediate tank 41 (reservoir), and a pressure reduction line 45 (second line) and a pressure reducing valve 46 (second valve) for switching the pressure reducing line 45 (second line) between an open state and a closed state. The drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are configured to open according to the height of the pressure inside the steam generator 24 .

According to this configuration, even if the pressure in the steam generator 24 deviates from the normal range and rises due to non-operation of the IC 30F, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are opened. By doing so, the cooling water discharged from the IC cooling water pool 31 (water source) to the intermediate tank 41 (reservoir) is introduced with the steam from the steam generator 24 and condensed, so the pressure in the reactor containment vessel 11F is suppressed. The steam generator 24 can be depressurized without providing a pool. That is, the structure of the reactor containment vessel 11F can be simplified, and the pressure of the steam generator 24 can be reduced without using dynamic equipment even when the IC 30F is inoperative.

Also, the present invention is not limited to the first to fifth embodiments described above, and includes various modifications. The above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the described configurations. For example, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Moreover, it is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

For example, in the first to fifth embodiments and other embodiments, the pressure of steam generated in the reactor pressure vessel 13 or the steam generator 24 is used to operate the drain valves 43, 43C and the pressure reducing valve 46. An example configured to open the valve is shown. However, the drain valve and pressure reducing valve may be configured to open without using the steam generated in the reactor pressure vessel 13 or the steam generator 24 . For example, by outputting a valve opening command based on a detection signal from a pressure sensor that detects the pressure of the reactor pressure vessel 13 or the steam generator 24, it is possible to open the drain valve and the pressure reducing valve. be.

Further, in the first to fifth embodiments and other embodiments, examples of configurations in which the decompression line 45 is indirectly connected to the reactor pressure vessel 13 or the steam generator 24 via the main steam pipe 14 showed that. However, configurations are also possible in which the vacuum line is directly connected to the reactor pressure vessel 13 or the steam generator 24 .

11, 11F... Reactor containment vessel, 11a... Floor surface (reservoir), 13... Reactor pressure vessel, 24... Steam generator, 30, 30F... Isolation condenser, 31... IC cooling water pool (water source) 41... intermediate tank (reservoir; tank), 41B... pressure vessel cooling tank (reservoir; tank), 42, 42A, 42B, 42C, 42D... drain line (first line), 43, 43C... drain valve ( 1st valve), 44, 44C... check valve, 45, 45A, 45B... decompression line (second line), 46... decompression valve (second valve), 47... floor water injection line (third line), 48 ...melting valve (third valve), 49...cooling water storage tank (water source), 70...pressure transmission pipe, 70E1...reducing valve drive system (valve drive system), 70E2...drain valve drive system (valve drive system), 71 ... high-pressure gas generator (gas supply source), 72 ... gas accumulator (gas supply source), 73 ... rupture disk, 74 ... fluid pressure converter (breaking operation unit), 75 ... switching valve, 81 ... first supply line ( supply line), 82... second supply line (supply line), 83, 83E2... third supply line (supply line), 11b, 41a... assumed water level

Claims

Safety of a nuclear power plant equipped with an emergency condenser that condenses steam from a reactor pressure vessel or steam generator housed in a reactor containment vessel by cooling and returns it to the said reactor pressure vessel or said steam generator again is a system,
a water source that is arranged outside the reactor containment vessel and stores cooling water;
a reservoir located inside the reactor containment vessel and below the water source, capable of receiving and storing cooling water discharged from the water source;
a first line connected to the water source and guiding cooling water from the water source to the reservoir;
a first valve provided on the first line for switching the first line between an open state and a closed state;
One side is directly or indirectly connected to the reactor pressure vessel or the steam generator, and the other side is located at a position lower than the assumed water level when the cooling water from the water source is stored in the reservoir. a second line that opens at
A second valve provided on the second line and switching the second line to an open state or a closed state,
A safety system for a nuclear plant, wherein the first valve and the second valve are configured to open according to the pressure level within the reactor pressure vessel or the steam generator.
In the nuclear plant safety system according to claim 1,
The isolation condenser includes a cooling water pool that stores cooling water for cooling steam from the reactor pressure vessel or the steam generator,
The safety system of a nuclear power plant, wherein the cooling water pool of the isolation condenser also serves as the water source.
In the nuclear plant safety system according to claim 1,
A nuclear plant safety system, wherein the storage unit is a tank installed inside the reactor containment vessel.
In the nuclear plant safety system according to claim 3,
A safety system for a nuclear plant, wherein the tank is arranged at a position distant from the reactor pressure vessel or the steam generator.
In the nuclear plant safety system according to claim 4,
a third line connected to the tank and capable of discharging cooling water discharged from the water source to the tank onto the floor of the containment vessel;
A third valve provided on the third line and closing the third line,
The safety system of a nuclear power plant, wherein the third valve is configured to open by receiving heat around the third valve.
In the nuclear plant safety system according to claim 3,
The tank is arranged so that the bottom of the reactor pressure vessel or the steam generator is positioned below the surface of the cooling water when the cooling water from the water source is stored. Plant safety system.
In the nuclear plant safety system according to claim 1,
A safety system for a nuclear power plant, wherein the storage section is a bottom including a floor surface of the containment vessel.
In the nuclear plant safety system according to claim 1,
A nuclear plant safety system, wherein the first valve is arranged outside the reactor containment vessel.
In the nuclear plant safety system according to claim 1,
A safety system for a nuclear power plant, wherein the pressure at which the second valve opens is set to be higher than the pressure at which the first valve opens.
In the nuclear plant safety system according to claim 1,
A safety system for a nuclear plant, wherein the first valve and the second valve are configured to open using the pressure of steam generated in the reactor pressure vessel or the steam generator. .
In the nuclear plant safety system according to claim 10,
The first valve and the second valve are configured to be directly operated by the pressure of the steam generated in the reactor pressure vessel or the steam generator supplied through a pressure transmission pipe. A safety system of a nuclear power plant characterized by:
In the nuclear plant safety system according to claim 10,
The first valve is configured to operate by being supplied with gas having a pressure equal to or higher than a predetermined value from a valve drive system,
The valve drive system includes:
a gas supply source that supplies a gas having a pressure equal to or higher than the predetermined value;
a supply line that guides gas from the gas supply source to the first valve;
a rupture disk arranged to close the supply line;
a rupture operation unit into which steam is introduced from the reactor pressure vessel or the steam generator, and which ruptures the rupture disk when the pressure of the steam exceeds a threshold value;
a switching valve provided closer to the first valve than the rupture disk on the supply line and switching the supply line to communicate when gas supplied from the gas supply source flows downstream of the rupture disk; A nuclear plant safety system characterized by comprising:
In the nuclear plant safety system according to claim 10,
The second valve is configured to operate by being supplied with gas having a pressure equal to or higher than a predetermined value from a valve drive system,
The valve drive system includes:
a gas supply source that supplies a gas having a pressure equal to or higher than the predetermined value;
a supply line that guides gas from the gas supply source to the second valve;
a rupture disk arranged to close the supply line;
a rupture operation unit into which steam is introduced from the reactor pressure vessel or the steam generator, and which ruptures the rupture disk when the pressure of the steam exceeds a threshold value;
a switching valve provided closer to the second valve than the rupture disk on the supply line and switching the supply line to communicate when gas supplied from the gas supply source flows downstream of the rupture disk; A nuclear plant safety system characterized by comprising:
In the nuclear plant safety system according to claim 1,
A safety system for a nuclear power plant, further comprising: a check valve provided on the first line to allow flow toward the reservoir while blocking flow toward the water source.