JP7431184B2 - Nuclear plant safety system - Google Patents

Description

The present invention relates to a safety system for a nuclear power plant.

In nuclear power plants, when it is necessary to shut down the plant due to periodic inspections or when a malfunction occurs in a part of the plant, control rods, which are part of the reactivity control system, are inserted into the reactor core to stop the nuclear fission reaction. Shut down the furnace. Even after the reactor is shut down, the core still generates heat due to decay heat, so it is necessary to remove the decay heat by releasing it from the reactor to the outside of the system.

An emergency condenser (hereinafter referred to as IC) is one of the devices for cooling a nuclear reactor by releasing decay heat to the outside of the system. An IC has a heat exchanger placed in a cooling water pool located higher than the reactor core. In the IC, steam generated by the decay heat of the core is guided to a heat exchanger, cooled by cooling water in a cooling water pool, and condensed. By condensing steam from the reactor pressure vessel or steam generator, increases in temperature and pressure in the reactor pressure vessel or steam generator are suppressed. The water condensed in the IC heat exchanger is fed back to the reactor pressure vessel or steam generator by gravity, so that decay heat removal can be continued. Since no emergency power supply or dynamic equipment is required to operate the IC, plant safety can be improved and plant equipment costs can also be reduced. The amount of heat removed by the IC decreases as the pressure in the reactor pressure vessel or steam generator decreases. Therefore, in order to maintain the heat removal function by the IC, it is generally necessary to maintain the reactor pressure vessel at a pressure of 1 MPa or more.

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

Japanese Patent Application Publication No. 2002-122689

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

In order to reduce the cost of nuclear power plants, it is also important to eliminate dynamic equipment such as water injection pumps and emergency power sources. By eliminating dynamic equipment and emergency power supplies, the costs of the dynamic equipment and emergency power supplies themselves can be reduced, as well as the costs associated with their maintenance.

If the boiling water nuclear power plant described in Patent Document 1 is equipped with both an automatic depressurization system and an IC, if the automatic depressurization system malfunctions, the reactor pressure vessel will be depressurized. There is a concern that a situation may arise in which the thermal function cannot be used effectively. Therefore, a plant concept has been proposed that emphasizes the use of the heat removal function of the IC and eliminates the automatic pressure reduction system including the safety valve. The plant concept, which makes full use of the IC's capabilities, eliminates the pressure suppression pool and eliminates the need for an emergency power source or water injection pump, making it possible to reduce costs.

In this plant concept, ICs are multiplexed from the viewpoint of safety. Therefore, it is highly unlikely that all ICs will fail. However, in the unlikely event that all ICs fail to operate, it is assumed that the reactor pressure vessel will not be able to be depressurized because the automatic depressurization system has been removed in a plant based on this concept. If the reactor pressure vessel cannot be depressurized, there is a risk that the reactor pressure vessel will eventually break due to high pressure. Therefore, it is necessary to consider reducing the pressure in the reactor pressure vessel when assuming that the IC is inoperative.

The present invention was made in order to solve the above problems, and its purpose is to simplify the structure of the reactor containment vessel, and to make it possible to simplify the structure of the reactor containment vessel even when the emergency condenser is not in operation. The present invention provides a safety system for a nuclear power plant 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 problems, and one example is to condense the steam from the reactor pressure vessel or steam generator stored in the reactor containment vessel by cooling and re-incorporate the above-mentioned atoms. A safety system for a nuclear power plant comprising an emergency condenser that returns to a reactor pressure vessel or the steam generator, the water source being arranged outside the reactor containment vessel and storing cooling water, and the reactor containment vessel. a storage section located inside the container and located below the water source and capable of receiving and storing cooling water discharged from the water source; a first line leading to the storage section; a first valve provided on the first line for switching the first line to an open state or a closed state; and one side directly connected to the reactor pressure vessel or the steam generator. and a second line that is connected directly or indirectly, and the other side is provided on the second line and opens at a lower position than the assumed water level when the cooling water from the water source is stored in the storage section. and a second valve that switches the second line to an open state or a closed state, and the first valve and the second valve are configured to switch the second line in accordance with the height of the pressure in the reactor pressure vessel or the steam generator. The valve is configured to open when the valve is opened.

According to the present invention, even if the pressure inside the reactor pressure vessel or the steam generator rises beyond the normal range due to the inoperation of the emergency condenser, the first valve and the second valve can be opened. In this case, steam from the reactor pressure vessel or steam generator is introduced into the cooling water discharged from the cooling water tank to the storage section and condensed, so the reactor pressure can be reduced without providing a pressure suppression pool in the reactor containment vessel. The container can be evacuated. That is, the structure of the reactor containment vessel can be simplified, and even when the emergency condenser is inactive, the pressure of the reactor pressure vessel can be reduced without using dynamic equipment.
Problems, configurations, and effects other than those described above will be made clear by the following description of the embodiments.

1 is a schematic system diagram showing a boiling water type nuclear power plant equipped with a first embodiment of the nuclear power plant safety system of the present invention. 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 power plant safety system of the present invention shown in FIG. 1. FIG. FIG. 3 is a schematic diagram showing the operating state (open state) of the drain valve and pressure reducing valve shown in FIG. 2 when the IC is not activated. FIG. 2 is a schematic diagram showing an example of the structure of a melting valve that constitutes a part of the first embodiment of the nuclear power plant safety system of the present invention shown in FIG. 1; FIG. 2 is a schematic system diagram showing the operating state of an emergency condenser (IC) in the first embodiment of the nuclear power plant safety system of the present invention shown in FIG. 1. FIG. FIG. 2 is a schematic system diagram showing an operating state when an IC is not activated in the first embodiment of the nuclear power plant safety system of the present invention shown in FIG. 1. FIG. FIG. 2 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. FIG. 2 is a schematic system diagram showing a nuclear power plant equipped with a third embodiment of the nuclear power plant safety system of the present invention. It is a schematic system diagram showing a nuclear power plant provided with a fourth embodiment of the nuclear power plant safety system of the present invention. It is a schematic system diagram showing a nuclear power plant provided with a fifth embodiment of a nuclear power plant safety system of the present invention. FIG. 7 is a block diagram showing a modification of a valve drive system for driving a pressure reducing valve that constitutes a part of the first to fifth embodiments of the nuclear power plant safety system of the present invention. FIG. 12 is a block diagram showing a state when the pressure reducing valve is activated (opened) in a modification of the pressure reducing valve drive system shown in FIG. 11; FIG. 3 is a block diagram showing a modification of a valve drive system for driving a drain valve that constitutes a part of the first to fifth embodiments of the nuclear power plant safety system of the present invention. 14 is a block diagram showing a state when the drain valve is operated (opened) in a modified example of the drain valve drive system shown in FIG. 13. FIG. 1 is a schematic system diagram showing a pressurized water type nuclear power plant equipped with an embodiment of the nuclear power plant safety system of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a safety system for a nuclear power plant according to the present invention will be described below with reference to the drawings. The first to fifth embodiments described below are examples in which the present invention is applied to a boiling water reactor (BWR).

[First embodiment]
The configuration of a nuclear power plant including a first embodiment of the nuclear power plant safety system of the present invention will be described using FIG. 1. FIG. 1 is a schematic system diagram showing a boiling water type nuclear power plant equipped with a first embodiment of the nuclear power plant safety system of 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 housed in a reactor containment vessel 11 of a nuclear power plant 1 . The pressure inside the reactor containment vessel 11 is approximately 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, which sends 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 that can shut off the main steam pipe 14 are installed inside and outside the reactor containment vessel 11 in the main steam pipe 14, respectively.

The nuclear power plant 1 has an emergency recovery system that releases thermal energy outside the system (outside the reactor containment vessel 11) as a safety system to maintain the nuclear power plant 1 in a safe state when an abnormality occurs in the reactor. It further includes a water container 30 (hereinafter referred to as IC) and a reduced pressure protection system 40 that reduces the pressure in the reactor pressure vessel 13 when the IC 30 does not operate. This nuclear power plant 1 includes a decompression protection system 40, so that the conventional automatic decompression system including a pressure suppression pool for depressurizing the reactor pressure vessel 13 is omitted.

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 a main steam pipe 14 (reactor). The IC steam supply line 33 connects the gas phase part 13b) of the pressure vessel 13, the outlet (lower side) of the IC heat exchanger 32, and the lower part of the reactor pressure vessel 13 (the part corresponding to the liquid phase part 13a). and an IC return line 34 for connecting to the IC. An IC starting 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 located above the reactor core 12, more 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 within the reactor pressure vessel 13 to the IC heat exchanger 32. The IC heat exchanger 32 cools and condenses steam supplied from the reactor pressure vessel 13 via the IC steam supply line 33 using cooling water in the IC cooling water pool 31 . The IC return line 34 returns water generated in the IC heat exchanger 32 to the reactor pressure vessel 13. The IC start valve 35 is closed during normal operation, but opens when the pressure in the reactor pressure vessel 13 rises above a predetermined value, for example, when a signal indicating a pressure rise is input. It is composed of

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

The decompression protection system 40 protects the reactor pressure vessel 13 by reducing the pressure in the reactor pressure vessel 13 when the IC 30 does not operate and the pressure inside the reactor pressure vessel 13 rises beyond the normal range. The reactor pressure vessel 13 is configured to start up by using steam whose pressure has increased. Specifically, the reduced pressure protection system 40 is located inside the reactor containment vessel 11 and the IC cooling water pool 31 of the IC 30 as a water source for storing cooling water, and is located 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, and a drain line 42 that branches from the main steam pipe 14 to the intermediate tank. 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 no cooling water is stored during normal operation, and is configured to receive and store cooling water discharged from the IC cooling water pool 31 only when the IC 30 does not operate. This is a tank installed to function as a storage area that can store water. The weight of the intermediate tank 41 is small because it does not store cooling water during normal operation. Therefore, the load on the intermediate tank 41 during an earthquake that may cause a failure is reduced. The intermediate tank 41 is located away from the reactor pressure vessel 13 , for example, right 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 a portion 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 cooling water from the cooling water tank. It is composed of For example, the drain line 42 is arranged within the reactor containment vessel 11 over its entire length.

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 a flow from the IC cooling water pool 31 to the intermediate tank 41, while blocking a flow from the intermediate tank 41 to the IC cooling water pool 31. The check valve 44 prevents gas within the reactor containment vessel 11 from being discharged to the outside of the reactor containment vessel 11 via 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 (start) when the pressure within the reactor pressure vessel 13 rises beyond the normal range. The drain valve 43 is opened using the pressure of steam generated in the reactor pressure vessel 13, and for example, the pressure of steam in the reactor pressure vessel 13 is transmitted via the pressure transmission pipe 70. Thus, the valve is configured to be switched between an open state and a closed state depending on the pressure. The structure of the drain valve 43 will be described later. The pressure transmission pipe 70 connects the upper part (gas phase part 13b) of the reactor pressure vessel 13 and the later-described valve opening/closing mechanism 54 of the drain valve 43 (see FIGS. 2 and 3 described later), and transmits the reactor pressure. This 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 part (gas phase part 13b) of the reactor pressure vessel 13 via the main steam pipe 14, and the other side is connected to the cooling water from the IC cooling water pool 31. It is installed so that it opens at a position lower than the assumed water level 41a when stored in the intermediate tank 41. The decompression line 45 guides a 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 (start) when the pressure within the reactor pressure vessel 13 rises beyond the normal range. The pressure reducing valve 46 is opened using the pressure of steam generated in the reactor pressure vessel 13, and for example, the pressure in the reactor pressure vessel 13 is transmitted via the pressure transmission pipe 70 to open the pressure reducing valve 46. The valve is configured to be switched between an open state and a closed state depending on the pressure. The pressure reducing valve 46 is configured to open at a higher pressure than 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 part (gas phase part 13b) of the reactor pressure vessel 13 and the later-described valve opening/closing mechanism 54 of the pressure reducing valve 46 (see FIGS. 2 and 3 described later), and transmits the reactor pressure. This is a pipe that transmits the pressure in the container 13 to the pressure reducing valve 46.

A floor water injection line 47 is connected to the intermediate tank 41 . The floor water injection line 47 discharges the cooling water discharged from the IC cooling water pool 31 into the intermediate tank 41 and stored therein to the floor surface 11a of the reactor containment vessel 11. The floor water injection line 47 extends, for example, from the bottom of the intermediate tank 41 toward the floor 11a of the reactor containment vessel 11. The floor water injection line 47 has a configuration based on the assumption that a core meltdown occurs.

A melting valve 48 for closing the floor water injection line 47 is provided on the floor water injection line 47 . The melting valve 48 is arranged, for example, at the end of the floor water injection line 47 near the floor surface 11a. The melting valve 48 is normally closed, and is configured to open (start) by receiving heat around the melting valve 48 and melting it. The structure of the melt valve 48 will be described later.

Next, 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 power plant safety system of the present invention will be described using FIGS. 2 and 3. 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 power plant safety system of the present invention shown in FIG. FIG. 3 is a schematic diagram showing the operating state (open state) of the drain valve and pressure reducing valve shown in FIG. 2 when the IC is not activated. The structures of the drain valve and pressure reducing valve are similar. The difference between a drain valve and a pressure reducing valve is that the installed piping is different and the operating pressure (valve opening pressure) is different.

In FIG. 2, the drain valve 43 and the pressure reducing valve 46 include a valve seat 51 provided in the drain line 42 (in the case of the pressure reducing valve 46, the pressure reducing line 45), and a valve body 52 that can be moved into and out of contact with the valve seat 51. , a valve spring 53 that urges the valve body 52 toward the valve seat 51 (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 (in the case of the pressure reducing valve 46, the pressure reducing line 45). The opening 51a is closed when the valve body 52 is seated. In the drain valve 43 and the pressure reducing valve 46, during normal operation of the nuclear power plant 1, the valve body 52 is pressed against the valve seat 51 by the urging force of the valve spring 53, and the drain line 42 (in the case of the pressure reducing valve 46, the pressure reducing line 45) is configured to close. The valve opening/closing mechanism 54 is configured to be operated directly by the pressure of the steam generated in the reactor pressure vessel 13 by being supplied through the pressure transmission pipe 70 .

Specifically, the valve opening/closing mechanism 54 includes a cylinder tube 55 into which the pressure of the reactor pressure vessel 13 is input, a piston 56 slidably disposed within the cylinder tube 55, and the piston 56 and the valve body 52. It has a piston rod 57 that connects. The piston 56 separates the inside of the cylinder tube 55 into a first chamber 55a and a second chamber 55b, and is displaced within the cylinder tube 55 in response to the pressure inside the first chamber 55a and the pressure inside the second chamber 55b. The piston rod 57 extends from the first chamber 55a 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 55a of the cylinder tube 55, and steam within the reactor pressure vessel 13 is supplied thereto. 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).

As shown in FIG. 3, a latch 58 is provided within the cylinder tube 55, with which the piston 56 engages. 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 unseated. In other words, the latch 58 maintains the drain valve 43 or the pressure reducing valve 46 in an activated, open state.

The opening pressures of the drain valve 43 and the pressure reducing valve 46 are adjusted by adjusting the urging force of the valve spring 53. That is, the drain valve 43 and the pressure reducing valve 46 open when the pressure of the steam inside the reactor pressure vessel 13 transmitted via the pressure transmission pipe 70 rises above a threshold value. The 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 activated. With this setting, it is possible to prevent the heat removal function of the IC 30 from being lost due to malfunction of the drain valve 43 and the pressure reducing valve 46. Further, 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.

If the IC 30 does not operate and the pressure in the reactor pressure vessel 13 rises for some reason, the high pressure inside the reactor pressure vessel 13 may cause the pressure transmission pipe 70 to flow into 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. With the displacement of the piston 56, the valve body 52 is displaced in a direction away from the valve seat 51, thereby opening the opening 51a of the valve seat 51, which had been closed by the valve body 52. In this way, the drain valve 43 and the pressure reducing valve 46 are configured so that the pressure inside the reactor pressure vessel 13 is transmitted to the first chamber 55a of the cylinder tube 55 via the pressure transmission pipe 70, so that the pressure in the reactor pressure vessel 13 is transmitted to the first chamber 55a of the cylinder tube 55. When the pressure in the reactor pressure vessel 13 becomes a high pressure state that deviates from the normal range, the valve is automatically opened without any operation by an operator and without using dynamic equipment. Furthermore, the piston 56 is displaced toward the second chamber 55b and engaged with the latch 58, thereby maintaining the open state of the valve body 52.

Next, an example of the structure of a melting valve that constitutes a part of the first embodiment of the nuclear power plant safety system of the present invention will be described using FIG. 4. FIG. 4 is a schematic diagram showing an example of the structure of a melting valve that constitutes a part of the first embodiment of the nuclear power 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 that can close the end opening of the floor water injection line 47, a swing arm 62 that is rotatably attached to the end of the floor water injection line 47, and a swing arm 62 that is rotatably attached to the end of the floor water injection line 47. 47, a support arm 63 that can support the swing arm 62, a swing lever 64 that is rotatably attached to the swing arm 62, and a weight 66 that is attached to the swing lever 64 via a wire 65. , and a low melting point attachment member 67 for attaching the weight 66 to the end of the floor water injection line 47.

The swing arm 62 has one end rotatably attached to the end of the floor water injection line 47 via a pivot pin 62a, and the other end supported by the support arm 63 so as to be detachable. An end plug 61 is fixed to the swing arm 62 so as to close the end opening of the floor 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 rotation pin 64a, and one end of a wire 65 is joined to the other end. The low-melting point attachment member 67 is made of a metal with a low melting point, and breaks due to melting or softening when a predetermined temperature is exceeded.

When the temperature around the melting valve 48 rises and the low melting point attachment member 67 is fused, the weight 66 falls due to its own weight, and the impact load of the weight 66 falling is transmitted to the swing lever 64 via the wire 65. As a result, the swing lever 64 rotates about the rotation pin 64a so as to push out the support arm 63, and as a result, the engagement between the engagement portion 63a of the support arm 63 and the swing arm 62 is released. The swing arm 62 that has been disengaged from the support arm 63 rotates about the rotation pin 62a so that the weight 66 is in a hanging state because the support arm 63 no longer supports it. As the swing arm 62 rotates, the end plug 61 comes off the opening of the floor water injection line 47, and the floor water injection line 47 becomes open. In this way, when the temperature near the melting valve 48 in the reactor containment vessel 11 reaches a high temperature state that deviates from the normal range, the melting valve 48 can be operated without being operated by an operator and using dynamic equipment. The valve opens automatically without any trouble.

Next, the operation of the first embodiment of the nuclear power plant safety system of the present invention will be explained using FIGS. 1 to 6. FIG. 5 is a schematic system diagram showing the operating state of the IC in the first embodiment of the nuclear power 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 activated in the first embodiment of the nuclear power plant safety system of the present invention shown in FIG.

In the nuclear power plant 1 shown in Fig. 1, nuclear fission in the reactor core 12 is stopped when the plant is stopped for periodic inspections, when an event that may have a negative impact on the plant occurs (for example, an earthquake), or when a control rod is inserted. Stop the plant by stopping it. At that time, if there is a possibility that a malfunction has occurred in the turbine (not shown) due to an earthquake or the like, the main steam isolation valve 15 is closed and steam is transferred from the reactor pressure vessel 13 to the outside of the reactor containment vessel 11. prevent leakage.

Even after the nuclear reactor is shut down, steam continues to be generated within the reactor pressure vessel 13 due to the decay heat of the reactor core 12. If this state continues, the pressure in the reactor pressure vessel 13 will increase. When a pressure increase in the reactor pressure vessel 13 is detected, as shown in FIG. 5, the IC starting valve 35 of the IC 30 opens (starts). When the IC startup valve 35 is opened, 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 by gravity due to the density difference with the steam in the IC steam supply line 33, and is used again to cool the reactor core 12. .

In this way, the IC 30 recovers the decay heat of the reactor core 12 by returning the steam from the reactor pressure vessel 13 to water and supplying it to the reactor pressure vessel 13 again by its own weight just by opening the IC startup valve 35. Continue removing. That is, the IC 30 can release the decay heat of the reactor core 12 to the outside of the system without using a pump (dynamic equipment) or an emergency power source for driving the pump.

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

When such a situation occurs and the pressure in the reactor pressure vessel 13 rises above the threshold value, the pressure in the reactor pressure vessel 13 is transmitted to the drain valve 43 via the pressure transmission pipe 70, causing the pressure in the reactor pressure vessel 13 to rise above the threshold value. As shown in FIG. 3, 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 discharged by gravity through the drain line 42 to the intermediate tank 41 which is empty during normal operation. Thereby, the cooling water discharged from the IC cooling water pool 31 is stored in the intermediate tank 41, and a water surface 41b is formed.

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 this 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.

When the pressure reducing valve 46 is opened, steam in the reactor pressure vessel 13 is discharged to the intermediate tank 41 through the main steam pipe 14 and the pressure reducing line 45. Thereby, the pressure of the reactor pressure vessel 13 is reduced, and high-pressure damage to the reactor pressure vessel 13 can be prevented. In this embodiment, the end opening of the decompression line 45 is located at a position lower than the water level 41b 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, and the energy of the steam in the reactor pressure vessel 13 is transferred to the intermediate tank 41. into the cooling water inside. Therefore, the pressure increase in the reactor containment vessel 11 can be suppressed compared to the case where the steam in the reactor pressure vessel 13 is directly released into the space inside the reactor containment vessel 11.

When the steam discharged into 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 are retained in the cooling water. Therefore, even if steam is released to the outside of the reactor containment vessel 11 after this, the amount of radioactive material released to the outside of the reactor containment vessel 11 can be suppressed. In this embodiment, the reactor 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 perform the same function as the pressure suppression pool.

Note that when the flow rate of steam flowing into the intermediate tank 41 through the decompression line 45 is very large, the rate of pressure rise in the reactor containment vessel 11 becomes faster. Therefore, it is preferable to design the diameter of the pressure reduction line 45 so that the speed of pressure reduction in the reactor pressure vessel 13 is as slow as possible. Alternatively, by providing an orifice (not shown) in the middle of the decompression line 45, it is possible to restrict the flow rate of steam passing through the decompression line 45. It is also possible to limit the flow rate of steam flowing into the intermediate tank 41 by using a flow restrictor (not shown) originally provided in the main steam pipe 14.

In this embodiment, the IC cooling water pool 31 is used as a water source for injecting water into the intermediate tank 41. The reduced pressure protection system 40 is activated when the IC 30 is not activated. Therefore, when the reduced pressure protection system 40 is activated, substantially all of the cooling water in the IC cooling water pool 31 remains. 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 wasting it, and there is no need to provide a new tank to store the cooling water to be injected into the intermediate tank 41. There is no

In this way, the reduced pressure protection system 40 is configured such that when the IC 30 is not activated and the pressure inside the reactor pressure vessel 13 rises above a threshold value, the drain valve 43 and the pressure reducing valve are 46 opens, and steam from the reactor pressure vessel 13 is introduced 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 depressurized and high-pressure damage to the reactor pressure vessel 13 can be prevented, and an increase in pressure 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 that depressurizes the reactor pressure vessel 13 when the IC 30 is inactive, but does not include a system for injecting water into the reactor pressure vessel 13. . The reason for this is that the pressure in the reactor pressure vessel 13 is 7 MPa or more, so if you try to inject water into the reactor pressure vessel 13 by gravity, the water source needs to be placed at a position 700 m or more higher than the reactor pressure vessel 13. This is because it is unrealistic.

Therefore, if the IC 30 does not operate, the core 12 may not be cooled and may melt due to decay heat. The molten core melts and damages the lower part of the reactor pressure vessel 13. When the lower part of the reactor pressure vessel 13 is damaged, the molten core falls onto the floor surface 11a of the reactor containment vessel 11 and spreads, raising the atmospheric temperature of the reactor containment vessel 11.

When the atmospheric temperature of the reactor containment vessel 11 reaches an abnormally high temperature due to the thermal energy of the molten core, the melt valve 48 opens. When the melting valve 48 is opened, the cooling water discharged and stored in the intermediate tank 41 is discharged into the molten core on the floor 11a of the reactor containment vessel 11 via the floor water injection line 47. This cooling water cools the molten core, and the severe accident is brought to an end. In this way, even in a situation where the IC30 does not operate, the melting valve 48 opens without any operation by the operator, and water is injected into the melted core using the weight of the cooling water without using dynamic equipment, thereby bringing the accident to an end. can be done.

As described above, the safety system of the nuclear power plant 1 according to the first embodiment condenses steam from the reactor pressure vessel 13 stored in the reactor containment vessel 11 by cooling, and then returns the steam to the reactor pressure vessel 13. The IC 30 is equipped with an IC 30 that is installed outside the reactor containment vessel 11 and serves as a water source for storing cooling water, and an IC cooling water pool 31 that is located inside the reactor containment vessel 11 and serves as a water source for storing cooling water. An intermediate tank 41 as a storage section located 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 an IC cooling water pool. A drain line 42 (first line) is connected to the IC cooling water pool 31 (water source) and leads the cooling water of the IC cooling water pool 31 (water source) to the intermediate tank 41 (storage section), and a drain line 42 (first line) is provided on the drain line 42 (first line). and a drain valve 43 (first valve) that switches the drain line 42 (first line) to an open state or a closed state, and one side is indirectly connected to the reactor pressure vessel 13, and the other side is connected to the IC cooling water. A reduced pressure line 45 (second line) opens at a position lower than the assumed water level 41a when cooling water from the pool 31 (water source) is stored in the intermediate tank 41 (storage section); ), and a pressure reducing valve 46 (second valve) that switches the pressure reducing line 45 (second line) to an open state or a closed state. The drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are configured to open depending on the height of the pressure within the reactor pressure vessel 13.

According to this configuration, even if the pressure inside the reactor pressure vessel 13 increases beyond the normal range due to the inoperation of the IC 30, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are opened. By closing the valve, steam from the reactor pressure vessel 13 is introduced into the cooling water discharged from the IC cooling water pool 31 (water source) to the intermediate tank 41 (storage part) 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 even when the IC 30 is inactive, the pressure of the reactor pressure vessel 13 can be reduced without using dynamic equipment.

Furthermore, in this embodiment, the IC 30 includes an IC cooling water pool 31 that stores cooling water for cooling steam from the reactor pressure vessel 13, and the IC cooling water pool 31 also serves as the above-mentioned water source. . According to this configuration, there is no need to separately install a cooling water tank as a water source for the decompression protection system 40 that stores cooling water to be discharged into the intermediate tank 41 in advance, so the configuration of the safety system of the nuclear power plant 1 is simplified. can be converted into

Further, in the present embodiment, the storage section described above is an intermediate tank 41 (tank) installed within the reactor containment vessel 11. According to this configuration, a storage section can be easily secured within the reactor containment vessel 11.

Furthermore, in the present embodiment, intermediate tank 41 is located at a position away from reactor pressure vessel 13. According to this configuration, the area around the reactor pressure vessel 13 where a large number of devices are arranged can be avoided as the location of the intermediate tank 41, so that it is easy to secure a space for the arrangement of the intermediate tank 41.

In addition, the safety system of the nuclear power plant 1 according to the present embodiment supplies the cooling water connected to the intermediate tank 41 and 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. a melting valve 48 (third valve) that is installed on the floor water injection line 47 (third line) and closes the floor water injection line 47 (third line). ). The melting valve 48 (third valve) is configured to open upon receiving heat around the melting valve 48 (third valve).

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

Further, in this 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 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, the energy of the steam in the reactor pressure vessel 13 is transferred to the cooling water, so that the pressure increase in the reactor containment vessel 1 can be reliably suppressed.

Further, in this embodiment, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are configured to open using the pressure of steam generated in the reactor pressure vessel 13. There is. According to this configuration, when the steam pressure in the reactor pressure vessel 13 increases due to the inoperation of the IC 30, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) can be opened automatically.

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

Further, 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 flow toward the intermediate tank 41 (storage section), while the IC cooling water pool 31 ( It further includes a check valve 44 for blocking the flow toward the water source. According to this configuration, gas in the reactor containment vessel 11 can be prevented from being released to the outside of the reactor containment vessel 11 via the drain line 42.

[Second embodiment]
Next, a second embodiment of the safety system for a nuclear power plant according to the present invention will be described using FIG. 7. 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. Note that in FIG. 7, parts having the same reference numerals as those shown in FIGS. 1 to 6 are similar parts, so detailed explanations will be omitted.

The difference between the safety system of a nuclear power plant according to the second embodiment of the present invention shown in FIG. 40A is to use the bottom of the reactor containment vessel 11, including the floor surface 11a, instead of the intermediate tank 41 of the reduced pressure protection system 40 of the first embodiment. The reduced pressure protection system 40A of this embodiment directly discharges the cooling water from the IC cooling water pool 31 onto 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 reduced pressure protection system 40A includes an IC cooling water pool 31 as a water source similar to the first embodiment, and extends 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 drain line 42A branched from the main steam pipe 14 to the floor surface 11a of the reactor containment vessel 11. It includes a pressure reduction line 45A extending to the vicinity of the pressure reduction line 45A, and a pressure reduction valve 46 similar to the first embodiment installed on the pressure reduction line 45A. The drain line 42A is for directly injecting at least a portion of the cooling water stored in the IC cooling water pool 31 onto the floor surface 11a 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 cooling water from the IC cooling water pool 31 is stored at the bottom of the reactor containment vessel 11. That is, the depressurization line 45A introduces steam within the reactor pressure vessel 13 into cooling water from the IC cooling water pool 31 stored at the bottom of the reactor containment vessel 11.

In this embodiment, when the IC 30 of the entire system does not operate, the pressure in the reactor pressure vessel 13 is transmitted to the drain valve 43 via the pressure transmission pipe 70, as in the first embodiment. This opens the drain valve 43. By opening the drain valve 43, the cooling water in the IC cooling water pool 31 is directly discharged onto the floor surface 11a of the reactor containment vessel 11 through the drain line 42A, and the cooling water is discharged 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 in 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. When the pressure reducing valve 46 is opened, the steam in the reactor pressure vessel 13 is introduced into the cooling water stored at the bottom of the reactor containment vessel 11 through the pressure reduction line 45A and condensed. The energy of the steam is transferred to the cooling water. As a result, the reactor pressure vessel 13 is depressurized and high-pressure damage to the reactor pressure vessel 13 can be prevented, and an increase in pressure in the reactor containment vessel 11 can be suppressed. Furthermore, 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 reactor containment vessel 11 and retained in the cooling water.

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

In this embodiment, the decompression line 45A is configured to open below the surface of the cooling water stored at the bottom of the reactor containment vessel 11 (at a 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 at the bottom of the reactor containment vessel 11, so there are many bubbles (also called voids) in the cooling water. ) will be included. There is knowledge that if the water contains voids, the risk of a steam explosion due to the fall of the molten core into the cooling water can be reduced.

In this embodiment, the IC cooling water pool 31 is stored such that the water level of the cooling water drained from the IC cooling water pool 31 to the floor surface 11a of the reactor containment vessel 11 reaches 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 reduced pressure 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 cooled without falling onto the floor 11a of the reactor containment vessel 11. Accidents can be brought under control. Therefore, post-accident processing such as removing molten fuel becomes easier.

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 inside the reactor pressure vessel 13 deviates from the normal range due to the inoperation of the IC 30. Even if the rise occurs, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) open, allowing water to flow from the IC cooling water pool 31 (water source) to the bottom (storage part) 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 even when the IC 30 is inactive, the pressure of the reactor pressure vessel 13 can be reduced without using dynamic equipment.

Further, in the present embodiment, the above-mentioned storage portion is the bottom portion of the reactor containment vessel 11 including the floor surface 11a. According to this configuration, the reduced pressure protection system 40A of the present embodiment has a structure in which the intermediate tank 41 is omitted from the structure of the reduced pressure protection system 40 of the first embodiment. By effectively utilizing the space occupied by the intermediate tank 41, it is possible to downsize the reactor containment vessel 11.

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

The third embodiment of the safety system for a nuclear power plant according to the present invention shown in FIG. Instead of the intermediate tank 41 of the reduced pressure protection system 40 of the first embodiment, a pressure vessel cooling tank 41B is installed as a storage section in the region where the bottom of the reactor pressure vessel 13 is located. The reduced pressure protection system 40B of this embodiment discharges the cooling water from the IC cooling water pool 31 to the pressure vessel cooling tank 41B, and uses the cooling water from the IC cooling water pool 31 stored in the pressure vessel cooling tank 41B to reduce the reactor pressure. It is configured to directly cool the bottom of the container 13 from the outside.

Specifically, the reduced pressure 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. A drain valve 43 and a check valve 44 similar to those in the first embodiment above, a pressure reduction line 45B branched from the main steam pipe 14 and connected to the pressure vessel cooling tank 41B, and a first drain valve on the pressure reduction line 45B. A pressure reducing valve 46 similar to that of the embodiment is provided. The pressure vessel cooling tank 41B stores the cooling water discharged from the IC cooling water pool 31 as a water source, and when the cooling water from the IC cooling water pool 31 is stored, the bottom of the reactor pressure vessel 13 is located below the surface of the cooling water. The drain line 42B guides at least a portion 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 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 within 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 are not activated, 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 into the pressure vessel cooling tank 41B through the drain line 42B, and the cooling water discharged from the IC cooling water pool 31 is stored in the pressure vessel cooling tank 41B. Ru.

Further, as in the first embodiment, the pressure reducing valve 46 opens later than the drain valve 43 due to the pressure in the reactor pressure vessel 13. When the pressure reducing valve 46 is opened, the steam in the reactor pressure vessel 13 is introduced into the cooling water stored in the pressure vessel cooling tank 41B through the pressure reduction line 45B and condensed. energy is transferred to the cooling water. As a result, the reactor pressure vessel 13 is depressurized and high-pressure damage to the reactor pressure vessel 13 can be prevented, and an increase in pressure in the reactor containment vessel 11 can be suppressed. Furthermore, 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 a region 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 has already been activated, so the cooling water stored in the pressure vessel cooling tank 41B will reduce the reactor pressure. The molten core that accumulates at the bottom of the vessel 13 can be cooled from the outside. Therefore, a severe accident can be brought to an end while the molten core remains within the reactor pressure vessel 13 without falling onto the floor 11a of the reactor containment vessel 11, and post-accident processing such as removal of molten fuel can be carried out. becomes easier.

Furthermore, in this embodiment, before the molten core falls to the bottom of the reactor pressure vessel 13, the cooling water stored in the pressure vessel cooling tank 41B is transferred from the reactor pressure vessel 13 via the decompression line 45B. It is heated by the steam released. 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 through 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 inside the reactor pressure vessel 13 deviates from the normal range due to the inoperation of the IC 30. Even if the water rises, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) open, thereby draining the IC cooling water pool 31 (water source) into the pressure vessel cooling tank 41B (storage section). Since steam from the reactor pressure vessel 13 is introduced into the cooled 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 even when the IC 30 is inactive, the pressure of the reactor pressure vessel 13 can be reduced without using dynamic equipment.

Furthermore, in this 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. It is located in According to this configuration, when the reduced pressure protection system 40B is activated due to the inoperation of the IC 30, the reactor pressure vessel 13 is cooled by the cooling water discharged from the IC cooling water pool 31 (water source) to the pressure vessel cooling tank 41B and stored. The bottom can be cooled externally.

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

The fourth embodiment of the nuclear power 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 reduced pressure protection system 40C are It is located outside of the Specifically, the drain line 42C of the reduced pressure protection system 40C extends from the bottom side of the side wall of the IC cooling water pool 31 outside the reactor containment vessel 11 to the intermediate tank 41 inside the reactor containment vessel 11. There is. The drain valve 43C and the check valve 44C are provided on a portion of the drain line 42C that extends outside the reactor containment vessel 11. Since the drain valve 43C is disposed outside the reactor containment vessel 11, a portion of the pressure transmission pipe 70C for driving the drain valve 43C extends to the outside of the reactor containment vessel 11. The other configurations and structures are similar to those of the first embodiment.

In the safety system of a nuclear power plant according to the fourth embodiment described above, the structure of the reactor containment vessel 11 can be simplified and the IC 30 can be eliminated, as in the case of the first embodiment. Even in the case of operation, the reactor pressure vessel 13 can be depressurized without using 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 first embodiment in which the drain valve 43 (first valve) is arranged inside the reactor containment vessel 11. It becomes easier. Therefore, the drain valve 43C (first valve) can be opened by the operation of the operator, and maintenance of the drain valve 43C (first valve) becomes easy.

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

The fifth embodiment of the nuclear power plant safety system of the present invention shown in FIG. 10 differs from the first embodiment in that it is a reduced pressure protection system that stores cooling water in advance to be discharged into an intermediate tank 41 as a storage section. Instead of the IC cooling water pool 31, a cooling water storage tank 49 is separately provided as a water source for the 40D. The reduced pressure protection system 40D of this embodiment discharges the cooling water in the cooling water storage tank 49 to the intermediate tank 41, and uses the cooling water from the cooling water storage tank 49 stored in the intermediate tank 41 to steam the reactor pressure vessel 13. It condenses the Specifically, the cooling water storage tank 49 of the reduced pressure protection system 40D is installed at a higher position 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 from the cooling water storage tank 49 to the intermediate tank 41. The other configuration of the reduced pressure protection system 40D is the same as that of the first embodiment.

In this embodiment, when the IC 30 of the entire system does not operate, the drain valve 43 is opened by the pressure of the reactor pressure vessel 13, and the cooling water storage tank 49 is drained, as in the first embodiment. The stored cooling water is drained into 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.

Further, as in 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 45B. The cooling water is introduced into the cooling water stored in the intermediate tank 41 and condensed. Thereby, the reactor pressure vessel 13 is depressurized, and high-pressure damage to the reactor pressure vessel 13 can be prevented, and the pressure increase in the reactor containment vessel 11 can be suppressed.

In the nuclear power plant safety system according to the fifth embodiment described above, as in the case of the first embodiment, the pressure inside the reactor pressure vessel 13 deviates from the normal range due to the inoperation of the IC 30. Even if the water rises, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) open, so that the cooling water discharged from the cooling water storage tank 49 (water source) to the intermediate tank (storage section) Since the steam from the reactor pressure vessel 13 is introduced 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 even when the IC 30 is inactive, the pressure of the reactor pressure vessel 13 can be reduced without using dynamic equipment.

[Modified example of valve drive system of pressure reducing valve]
Next, the configuration of a modified example of the valve drive system for driving the pressure reducing valve that constitutes a part of the first to fifth embodiments of the nuclear power plant safety system of the present invention will be explained using FIG. 11. . FIG. 11 is a block diagram showing a modification of a valve drive system for driving a pressure reducing valve that constitutes a part of the first to fifth embodiments of the nuclear power plant safety system of the present invention. Note that in FIG. 11, parts having the same reference numerals as those shown in FIGS. 1 to 10 are similar parts, so a detailed explanation thereof will be omitted.

The modification 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 of the reactor pressure vessel 13 is used. In the valve drive system for the pressure reducing valve 46 of the first to fifth embodiments, the pressure in the reactor pressure vessel 13 is transmitted to the pressure reducing valve 46 via the pressure transmission pipe 70 directly connected to the reactor pressure vessel 13. The signal is transmitted to the valve opening/closing mechanism 54 (see FIGS. 2 and 3). Therefore, it may become difficult to route the piping from the reactor pressure vessel 13 to the pressure reducing valve 46. Therefore, in the valve drive system 70E1 of this modification, a pressure source that can be placed near the pressure reducing valve 46 is separately installed.

The pressure reducing valve 46 is composed of a gas-operated valve that is operated by gas such as air or nitrogen, and the pressure reducing valve drive system 70E1 that drives the pressure reducing valve 46 operates when the pressure of steam in the reactor pressure vessel 13 exceeds a second threshold value. When the pressure rises, a pressure source different from that of the steam in the reactor pressure vessel 13 is used for operation. Specifically, the pressure reducing valve drive system 70E1 includes a high pressure gas generator 71 that generates high pressure gas G (air, nitrogen, etc.) with a pressure equal to or higher than a first predetermined value, and a high pressure gas generator 71 that generates high pressure gas G generated by the high pressure gas generator 71. a gas pressure accumulating device 72 that accumulates pressure, a ruptureable rupture disk 73, a fluid pressure converter 74 that performs a rupture operation of the rupture disk 73 according to the input pressure, and a switch that switches the flow path according to the upstream pressure. A valve 75 is provided.

The high-pressure gas generator 71 is connected to the primary side of the fluid pressure converter 74 via a 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, and for example, a cylinder can be used. . A first check valve 76 and a second check valve 77 are provided on the upstream and downstream sides 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 to the valve opening/closing mechanism 54 (see FIGS. 2 and 3) of the pressure reducing valve 46 via a third supply line 83. 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 accumulator 72 supply 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 reduction line 45 . The bleed line 84 introduces 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 pressure reducing line 45 near the installation position of the pressure reducing valve 46, and the piping to the fluid pressure converter 74 is routed in the same manner as the pressure transmission of the reduced pressure protection system 40 of the first embodiment. This is easier than with tube 70. The fluid pressure converter 74 is configured such that the pressure of the fluid F1 input to the secondary side via the bleed line 84 reaches a second threshold value (the same value as the opening pressure of the pressure reducing valve 46 in the first to fifth embodiments). If the rupture disk 73 is exceeded, the rupture operation section is configured to rupture the rupture disk 73 with 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 with 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 connect the third supply line 83, while connecting the third supply line 83 with the other one. 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 that is 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 a modified example of the pressure reducing valve drive system will be described using FIG. 12. FIG. 12 is a block diagram showing a state when the pressure reducing valve is activated (opened) in a modification of the pressure reducing valve drive system shown in FIG. 11. 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 reactor core 12 continues, so the pressure in the reactor pressure vessel 13 does 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 bleed line 84, as shown in FIG. Therefore, the rupture disk 73 will not be broken. If the rupture disk 73 is maintained in a normal state, the rupture disk 73 prevents the high pressure gas G from being supplied from the high pressure gas generator 71 and the gas 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, if the IC 30 of the entire system does not operate and the pressure of the reactor pressure vessel 13 rises above the second threshold, the second When the pressure exceeding the threshold is input to the secondary side of the fluid pressure converter 74, the fluid pressure converter 74 ruptures the high pressure gas G from the high pressure gas generator 71 or the gas accumulator 72, as shown in FIG. It acts on the disk 73 to break it. Due to the rupture of the rupture disk 73, the high pressure gas G from the high pressure gas generator 71 or the gas accumulator 72 flows into the third supply line 83, and the switching valve 75 is switched so that the third supply line 83 is in communication. 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 opens. By opening the pressure reducing valve 46 and communicating the pressure reducing line 45, the steam in the reactor pressure vessel 13 is released into the cooling water in the intermediate tank 41 via the pressure reducing line 45, and the reactor pressure vessel 13 is depressurized. Ru.

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

In the pressure reducing valve drive system 70E1 of this modification, high pressure gas G is accumulated in the gas pressure accumulation device 72. Therefore, even if the pressure reducing valve drive system 70E1 loses power, the supply of 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 accumulating device 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 something. The valve drive system 70E1 includes a high-pressure gas generator 71 and a gas accumulator 72 as a gas supply source that supplies gas with a pressure equal to or higher than a first predetermined value (predetermined value), and a high-pressure gas generator 71 and a gas accumulator 72 ( Supply lines 81, 82, 83 that lead gas from a gas supply source) to the pressure reducing valve 46 (second valve), a rupture disk 73 provided to close the supply line 83, and a rupture disk 73 that leads gas from the reactor pressure vessel 13. Steam is introduced, and when the pressure of the steam exceeds a second threshold (threshold), a fluid pressure converter 74 serves as a rupture operation unit that ruptures the rupture disk 73, and a pressure is reduced 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 generation device 71 or the gas accumulator 72 (gas supply source) flows downstream from the rupture disk 73, the third supply line 83 is cut off. It has a switching valve 75 that switches from the state to the communication state.

According to this configuration, the high-pressure gas generation device 71 and the gas accumulator 72 (gas supply source) that drive the pressure reducing valve 46 (second valve) can be arranged near the pressure reducing valve 46 (second valve). , the degree of freedom in routing the piping (supply line) that supplies pressure to the pressure reducing valve 46 (second valve) can be increased.

[Modified example of the valve drive system of the drain valve]
Next, a modification of the valve drive system for driving the drain valve, which constitutes a part of the first to fifth embodiments of the nuclear power plant safety system of the present invention, will be explained using FIGS. 13 and 14. do. FIG. 13 is a block diagram showing a modified example of a valve drive system for driving a drain valve that constitutes a part of the first to fifth embodiments of the nuclear power plant safety system of the present invention. FIG. 14 is a block diagram showing a state when the drain valve is operated (opened) in a modification of the drain valve drive system shown in FIG. 12. Note that in FIGS. 13 and 14, the same reference numerals as those shown in FIGS. 1 to 12 refer to similar parts, so a detailed explanation thereof will be omitted. In FIG. 14, the shape of the rupture disk schematically shows that it is in a fractured state.

The difference between the modified example of the valve drive system of the drain valve 43 shown in FIG. 13 and the valve drive system of the drain valve 43 of the first to fifth embodiments is that the pressure source for driving the drain valve 43 is reactor pressure. Instead of the steam from the vessel 13, a pressure source that supplies a high pressure gas different from the high pressure steam of the reactor pressure vessel 13 is used. The drain valve drive system 70E2 that drives the drain valve 43 has the same configuration as the pressure reducing valve drive 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 a part of the structure is different due to the difference in the decompression line 45).

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, like 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 decompression line 45. The fluid pressure converter 74 is configured such that the pressure of the fluid F1 inputted to the secondary side via the bleed line 84 reaches a first threshold value (the same value as the opening pressure of the drain valve 43 in the first to fifth embodiments). If the rupture disk 73 is exceeded, the rupture operation section is configured to rupture the rupture disk 73 with gas from the high-pressure gas generator 71 or the gas pressure accumulator 72. The bleed line 84E2 introduces steam from the reactor pressure vessel 13 supplied to the main steam pipe 14 or the pressure reduction line 45 to the fluid pressure converter 74. The bleed air line 84E2 can be connected to the main steam pipe 14 or the pressure reduction line 45 near the installation position of the drain valve 43, and the piping to the fluid pressure converter 74 is routed in the same manner as in the first embodiment. This is easier than in the case of the pressure transmission pipe 70 of the reduced pressure 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).

If the IC 30 of the entire system does not operate and the pressure of the reactor pressure vessel 13 rises above the first threshold value, as shown in FIG. Since the pressure of the fluid F2 (steam) exceeding 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. Due to the rupture of the rupture disk 73, the high pressure gas G from the high pressure gas generator 71 or the gas 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 in communication. It will 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. When the drain valve 43 is opened and the drain line 42 is brought into communication, 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 this 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 something that The valve drive system 70E2 includes a high-pressure gas generator 71 and a gas accumulator 72 as a gas supply source that supplies gas with a pressure equal to or higher than a first predetermined value (predetermined value), and a high-pressure gas generator 71 and a gas accumulator 72 ( Supply lines 81, 82, 83E2 that lead gas from a gas source (gas supply source) to the drain valve 43 (first valve), a rupture disk 73 provided to close the supply line 83E2, and a rupture disk 73 that leads gas from the reactor pressure vessel 13 A fluid pressure converter 74 as a rupture operation unit that ruptures the rupture disk 73 when steam is introduced and the pressure of the steam exceeds a first threshold (threshold), and a rupture disk 73 on the supply lines 81, 82, 83E2. It is provided on the drain valve 43 (first valve) side and shuts off the third supply line 83E2 when the gas supplied from the high-pressure gas generation device 71 or the gas pressure accumulator 72 (gas supply source) flows downstream from the rupture disk 73. It has a switching valve 75 that switches from the state to the communicating state.

According to this configuration, the high-pressure gas generation device 71 and the gas accumulator 72 (gas supply source) that drive the drain valve 43 (first valve) can be arranged near the drain valve 43 (first valve). , the degree of freedom in routing the piping (supply line) that supplies pressure to the drain valve 43 (first valve) can be increased.

[others]
In addition, in the first to fifth embodiments described above, an example was shown in which the present invention was applied to a boiling water reactor, 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 using FIG. 15. FIG. 15 is a schematic system diagram showing a pressurized water type nuclear power plant equipped with an embodiment of the nuclear power plant safety system of the present invention. Note that in FIG. 15, the same reference numerals as those shown in FIGS. 1 to 14 refer to similar parts, so a detailed explanation will be omitted.

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

The IC 30F as a safety system of the pressurized water type nuclear power plant 1F condenses 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 (gas phase portion 24b) of the steam generator 24. Further, the IC return line 34 connects the outlet (lower side) of the IC heat exchanger 32 and the lower part (liquid phase portion 24a) of the steam generator 24.

The depressurization protection system 40F as a safety system of the pressurized water type nuclear power plant 1F reduces the pressure of the steam generator 24 when the IC 30F does not operate and the pressure inside the steam generator 24 rises beyond the normal range. The steam generator 24 is protected by the steam generator 24, and the steam generator 24 is activated by using the steam whose pressure has increased. The components of the reduced pressure protection system 40F are the same as those of the reduced pressure protection system 40 of the boiling water type nuclear power plant 1. However, the decompression line 45 introduces a portion of the steam in the steam generator 24 into the cooling water stored in the intermediate tank 41. Further, the drain valve 43 and the pressure reducing valve 46 are configured to open using the pressure of steam from the steam generator 24. One side of the pressure transmission pipe 70 is connected to the upper part of the steam generator 24 (gas phase section 24b). The operation of this reduced pressure protection system 40F is similar to the operation of the reduced pressure protection system 40 of the boiling water type nuclear power plant 1. Therefore, the same effect as the reduced pressure protection system 40 of the boiling water type nuclear power plant 1 can be obtained also in the reduced pressure protection system 40F of the pressurized water type nuclear power plant 1F.

As described above, the safety system of the nuclear power plant 1F according to the present embodiment applied to PWR condenses steam from the steam generator 24 stored in the reactor containment vessel 11F by cooling, and then returns the steam to the steam generator 24. It is equipped with an IC30F that is installed outside the reactor containment vessel 11F and serves as a water source for storing cooling water, and an IC cooling water pool 31 that is located inside the reactor containment vessel 11F. An intermediate tank 41, which is located below the IC cooling water pool 31 (water source) and serves as a storage section capable of receiving and storing cooling water discharged from the IC cooling water pool 31 (water source), and an IC cooling water A drain line 42 (first line) connected to the pool 31 (water source) and leading the cooling water of the IC cooling water pool 31 (water source) to the intermediate tank 41 (storage section); A drain valve 43 (first valve) is provided to switch the drain line 42 (first line) into 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 an IC. A reduced pressure line 45 (second line) opens at a position lower than the assumed water level 41a when cooling water from the cooling water pool 31 (water source) is stored in the intermediate tank 41 (storage section); A pressure reducing valve 46 (second valve) is provided on the pressure reducing line 45 (second line) and switches the pressure reducing line 45 (second line) to an open state or a closed state. The drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are configured to open depending on the height of the pressure within the steam generator 24.

According to this configuration, even if the pressure inside the steam generator 24 increases beyond the normal range due to the inoperation of the IC 30F, the drain valve 43 (first valve) and the pressure reducing valve 46 (second valve) are opened. By doing so, steam from the steam generator 24 is introduced into the cooling water discharged from the IC cooling water pool 31 (water source) to the intermediate tank 41 (storage section) and condensed, so that pressure is suppressed in the reactor containment vessel 11F. 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 even when the IC 30F is inactive, the steam generator 24 can be depressurized without using dynamic equipment.

Further, the present invention is not limited to the first to fifth embodiments described above, and includes various modifications. The embodiments described above have been described in detail to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. For example, it is possible to replace a 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. Furthermore, it is also possible to add, delete, or replace some of the configurations of each embodiment with other configurations.

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

In the first to fifth embodiments and other embodiments, 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, a configuration in which the pressure reduction line is directly connected to the reactor pressure vessel 13 or the steam generator 24 is also possible.

11, 11F... Reactor containment vessel, 11a... Floor surface (storage part), 13... Reactor pressure vessel, 24... Steam generator, 30, 30F... Emergency condenser, 31... IC cooling water pool (water source) , 41... Intermediate tank (storage part; tank), 41B... Pressure vessel cooling tank (storage part; tank), 42, 42A, 42B, 42C, 42D... Drain line (first line), 43, 43C... Drain valve ( 44, 44C... Check valve, 45, 45A, 45B... Pressure reducing line (second line), 46... Pressure reducing 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...Pressure reducing valve drive system (valve drive system), 70E2...Drain valve drive system (valve drive system), 71 ...High pressure gas generation device (gas supply source), 72...Gas pressure accumulator (gas supply source), 73...Rupture disk 73...Fluid pressure converter (rupture operation part), 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 (14)

Safety of a nuclear power plant equipped with an emergency condenser that condenses steam from a reactor pressure vessel or steam generator stored in a reactor containment vessel by cooling and returns it to the reactor pressure vessel or the steam generator. system,
a water source located outside the reactor containment vessel and storing cooling water;
a storage section located inside the reactor containment vessel and located below the water source, and 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 storage section;
a first valve provided on the first line and switching the first line to an open state or a closed state;
One side is directly or indirectly connected to the reactor pressure vessel or the steam generator, and the other side is at a position lower than the expected water level when cooling water from the water source is stored in the storage section. A second line opening at
and a second valve provided on the second line to switch the second line to an open state or a closed state,
The safety system for a nuclear power plant, wherein the first valve and the second valve are configured to open depending on the height of pressure within the reactor pressure vessel or the steam generator. In the nuclear plant safety system according to claim 1,
The emergency 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 for a nuclear power plant, wherein the cooling water pool of the emergency condenser also serves as the water source. In the nuclear plant safety system according to claim 1,
The safety system for a nuclear power plant, wherein the storage section is a tank installed inside the reactor containment vessel. In the nuclear plant safety system according to claim 3,
The safety system for a nuclear power plant, characterized in that the tank is located at a location away 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 releasing cooling water discharged from the water source into the tank onto the floor surface of the reactor containment vessel;
further comprising a third valve provided on the third line and closing the third line,
A safety system for a nuclear power plant, wherein the third valve is configured to open upon receiving heat around the third valve. In the nuclear plant safety system according to claim 3,
The nuclear power plant is characterized in that the tank is arranged such that when cooling water from the water source is stored, the bottom of the reactor pressure vessel or the steam generator is located below the surface of the cooling water. Plant safety system. In the nuclear plant safety system according to claim 1,
The safety system for a nuclear power plant, wherein the storage section is a bottom portion including a floor surface of the reactor containment vessel. In the nuclear plant safety system according to claim 1,
The safety system for a nuclear power plant, wherein the first valve is disposed outside the reactor containment vessel. In the nuclear plant safety system according to claim 1,
A safety system for a nuclear power plant, wherein a pressure at which the second valve opens is set to be higher than a pressure at which the first valve opens. In the nuclear plant safety system according to claim 1,
The safety system for a nuclear power 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 operated directly by the pressure of steam generated in the reactor pressure vessel or the steam generator by being supplied through a pressure transmission pipe. A nuclear power plant safety system characterized by: In the nuclear plant safety system according to claim 10,
The first valve is configured to operate when gas at a pressure equal to or higher than a predetermined value is supplied from the valve drive system,
The valve drive system includes:
a gas supply source that supplies gas at a pressure equal to or higher than the predetermined value;
a supply line that directs gas from the gas source to the first valve;
a rupture disk configured to close the supply line;
a rupture operation unit that ruptures the rupture disk when steam from the reactor pressure vessel or the steam generator is introduced and the pressure of the steam exceeds a threshold;
a switching valve provided on the supply line closer to the first valve than the rupture disk, and configured to switch the supply line into communication when the gas supplied from the gas supply source flows downstream from the rupture disk; A safety system for a nuclear power plant characterized by having the following. In the nuclear plant safety system according to claim 10,
The second valve is configured to operate when gas at a pressure equal to or higher than a predetermined value is supplied from the valve drive system,
The valve drive system includes:
a gas supply source that supplies gas at a pressure equal to or higher than the predetermined value;
a supply line that directs gas from the gas source to the second valve;
a rupture disk configured to close the supply line;
a rupture operation unit into which steam from the reactor pressure vessel or the steam generator is introduced, and when the pressure of the steam exceeds a threshold value, the rupture disk is ruptured by gas from the gas supply source;
a switching valve provided on the supply line closer to the second valve than the rupture disk, and configured to switch the supply line into communication when the gas supplied from the gas supply source flows downstream from the rupture disk; A safety system for a nuclear power plant characterized by having the following. 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, which allows a flow toward the storage section, while blocking a flow toward the water source.

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