JP2021043080A - Boric acid water injection device - Google Patents

Abstract

To provide a boric acid water injection device which can be made simpler in constitution by omitting the dynamic equipment.SOLUTION: Disclosed is a boric acid water injection device which injects boric acid water 14 in a nuclear power plant provided with a reactor containment vessel 1 storing a reactor pressure vessel 3 containing a core 2 and which includes a boric acid water tank 13 for storing the boric acid water 14 therein. The boric acid water tank 13 is arranged inside the reactor containment vessel 1. Further, a reactor containment vessel bottom injection line 19 is preferably provided for guiding the boric acid water 14 stored in the boric acid water tank 13 vertically downward from the lower end of the reactor pressure vessel 3.SELECTED DRAWING: Figure 1

Description

The present invention relates to a boric acid water injection device, which is one of the safety equipment of a nuclear power plant.

Patent Document 1 describes the first and second nuclear power plants for the purpose of providing a boric acid water injection facility that can be shared between two nuclear power plants to reduce the construction cost of the nuclear power plant and rationalize the facilities. An SLC tank, a test tank, and an SLC pump are provided so that they can be shared between the nuclear power plants of the nuclear power plant, and each of them is connected by piping via a sluice valve, an injection valve, a switching valve, and an electric stop valve. It is stated that the function of this system is also satisfied in the nuclear power plant of.

Japanese Unexamined Patent Publication No. 09-274902

In a nuclear plant, when it becomes necessary to stop the plant, such as in the case of periodic inspections or when a part of the plant malfunctions, a control rod, which is a reactivity control system, can be inserted into the core. Stop the fission reaction and shut down the reactor. Since it is necessary to have a function to stop the plant, the reliability of these control rods and their drive mechanism is extremely high.

Further, especially in a boiling water reactor, a boric acid water injection device (hereinafter referred to as ATWS) as a retrofit reactivity control system should be prepared in case the control rod insertion fails (hereinafter referred to as ATWS), although the probability is extremely low. It is also called SLC).

When this boric acid water injection device detects ATWS, it injects boric acid water containing boron into the core inside the reactor pressure vessel, absorbs neutrons with boron contained in boric acid, and stops the reaction in the core. However, it is a device that has the function of shutting down the reactor.

In Patent Document 1 described above, a tank of boric acid water is provided outside the reactor containment vessel, and when ATWS is detected, a pump for injecting boric acid water is started to inject boric acid water into the core. Since the reliability of the control rods and their drive mechanism is extremely high, the cost is reduced by sharing the boric acid water injection device, which is rarely used, with two or more reactors.

Here, it is important to remove dynamic equipment such as pumps, emergency power supplies, and heaters for rationalization of nuclear power plants. By deleting the dynamic device, it is possible to reduce the inspection items at the time of periodic inspection and reduce the burden of inspection, and it is possible to operate the equipment at an early stage and shorten the interruption of the operation period. Further, the cost of the equipment itself and the cost of maintenance of the equipment can be reduced.

In Patent Document 1 described above, rationalization per reactor is realized by sharing the boric acid water injection device among two or more reactors. However, the number of dynamic devices such as pumps, power supplies, and heaters has not been reduced.

An object of the present invention is to provide a boric acid water injection device that can be configured in a simpler manner by omitting a dynamic device.

The present invention includes a plurality of means for solving the above problems. For example, boric acid water is used in a nuclear power plant provided with a reactor containment vessel containing a reactor pressure vessel containing a core. It is a boric acid water injection device for injecting, and is characterized in that a boric acid water tank for storing the boric acid water is provided inside, and the boric acid water tank is arranged inside the reactor containment vessel.

According to the present invention, a dynamic device can be omitted to form a simpler configuration. Issues, configurations and effects other than those mentioned above will be clarified by the description of the following examples.

It is a figure which shows the outline of the main system of the boiling water reactor and the boric acid water injection apparatus which concerns on Example 1 of this invention. It is a schematic diagram which shows the piping structure of the bottom of the reactor containment vessel of the boric acid water injection apparatus which concerns on Example 1 of this invention. It is a figure which shows the outline of the main system of the boiling water reactor and the boric acid water injection apparatus which concerns on Example 2 of this invention. It is a figure which shows the outline of the main system of the boiling water reactor and the boric acid water injection apparatus which concerns on Example 3 of this invention. It is a schematic diagram which shows the structure and operation of the boric acid water injection valve provided in the boric acid water injection apparatus which concerns on Example 3 of this invention. It is a schematic diagram which shows the structure and operation of the boric acid water injection valve provided in the boric acid water injection apparatus which concerns on Example 3 of this invention. It is a schematic diagram which shows the piping structure of the bottom of the reactor containment vessel of the boric acid water injection apparatus which concerns on Example 4 of this invention. It is a figure which shows the outline of the main system of the boiling water reactor and the boric acid water injection apparatus which concerns on Example 5 of this invention. It is a figure which shows the outline of the main system of the boiling water reactor and the boric acid water injection apparatus which concerns on Example 6 of this invention. It is a schematic diagram of the bottom injection line and the lower dry well boric acid water injection valve of the reactor containment vessel which concerns on Example 6 of this invention.

Hereinafter, examples of the boric acid water injection device of the present invention will be described with reference to the drawings.

The reactor includes a boiling water reactor and a pressurized water reactor, and all of them will be described by taking a boiling water reactor as an example in the present invention, but the present invention can also be applied to a pressurized water reactor.

<Example 1>
Example 1 of the boric acid water injection device of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a main system diagram of a boiling water reactor according to the first embodiment of the present invention. FIG. 2 is a schematic view showing a piping structure at the bottom of the reactor containment vessel of the boric acid water injection device according to the first embodiment of the present invention.

The boric acid water injection device shown in FIG. 1 is an example applied to the improved boiling water reactor 100, and has the following system configuration. As shown in FIG. 1, in the boiling water reactor 100, a core 2 in which a plurality of fuel assemblies (omitted for convenience of illustration) are loaded in a grid pattern is contained in the reactor pressure vessel 3. The reactor pressure vessel 3 is connected to a main steam pipe 4 (not shown), a water supply pipe (not shown), and the like that send steam generated in the reactor pressure vessel 3 to a turbine (not shown).

In the reactor pressure vessel 3, steam is generated by boiling the cooling water that has flowed into the core 2 by the heat generated by the nuclear fission generated in the fuel assembly in the core 2.

The inside of the reactor containment vessel 1 is divided into a dry well 5 and a suppression chamber 7 by a reinforced concrete diaphragm floor 12. Of the dry wells 5, the lower portion of the reactor pressure vessel 3 is referred to as a lower dry well 5a. The suppression chamber 7 refers to an area in which pool water is stored. The pool in the suppression chamber 7 is called a suppression pool 8. The dry well 5 and the suppression chamber 7 are communicated with each other by a vent pipe 11, and the vent pipe exhaust portion 11a opens below the water surface of the suppression pool 8 in the suppression chamber 7.

In a nuclear power plant, when the plant is stopped due to periodic inspections or when an event that may adversely affect the plant (for example, an earthquake) occurs, the control rod 36 is inserted into the core 2 and the nuclear fission is stopped to stop the plant. Stop it.

However, although there is a very low probability, in the unlikely event that the insertion of the control rod 36 fails (when ATWS occurs), the boric acid water 14 stored in the boric acid water tank 13 is taken from the boric acid water tank 13 to the core. By injecting into the inside of 2, the fission reaction is stopped and the plant is stopped.

In this embodiment, the boric acid water injection device for this purpose includes the boric acid water tank 13 shown in FIG. 1, the pressurizing device 15, the control rod insertion failure detection mechanism 24, the boric acid water injection valve 16, and the reactor pressure vessel injection. It is composed of a line 17 and an injection line 19 at the bottom of the reactor containment vessel.

Here, in order to prevent the precipitation of boric acid, in the existing boric acid water injection device, a heater is installed to keep the boric acid water 14 at 30 ° C. or higher.

On the other hand, in the boiling water reactor 100 of this embodiment, the boric acid water tank 13 is installed inside the reactor containment vessel 1. Due to the heat escaping from the reactor pressure vessel 3 to the reactor containment vessel 1, the inside of the reactor containment vessel 1 is always in an environment of 30 ° C. or higher, so that a heater for heating the boric acid water 14 becomes unnecessary.

Further, in the boiling water reactor 100 of the present embodiment, the boric acid water tank 13 is pressurized even during normal operation by a pressurizing device 15 such as a gas cylinder filled with an inert gas such as nitrogen. It is assumed that the pressure has been accumulated.

In this embodiment, the reactor pressure vessel injection line 17 is provided as a line for sending the boric acid water 14 to the core 2 in the reactor pressure vessel 3, and the boric acid water tank 13 and the reactor pressure vessel are provided. It communicates with 3.

A boric acid water injection valve 16 is arranged on the reactor pressure vessel injection line 17, and the reactor pressure vessel injection line 17 is closed by the boric acid water injection valve 16 during normal operation.

In this embodiment, the boric acid water injection valve 16 uses an blast valve that opens when a control rod insertion failure event occurs. By using such a blast valve, it is possible to prevent the boric acid water from flowing into the reactor pressure vessel 3 during normal operation due to valve leakage.

Here, a known configuration can be adopted as the configuration for opening the boric acid water injection valve 16, but for example, the control rod insertion failure detection mechanism 24 detects the presence or absence of ATWS, and ATWS is generated. When it is detected, the boric acid water injection valve 16 is made to output an open signal from the control rod insertion failure detection mechanism 24, and the explosive of the blast valve is ignited so that the boric acid water injection valve 16 is opened. When the boric acid water injection valve 16 is opened, the boric acid water 14 is injected into the core portion in the reactor pressure vessel 3 by using the pressure accumulated in the boric acid water tank 13 as a drive source.

For the boric acid water injection valve 16, an electric valve or an air-operated valve that can be opened by the operator can be used instead of the above-mentioned blast valve.

In this case, it is necessary to prepare a power source such as a battery for driving the electric valve or the air-operated valve, but since it is only necessary to drive the electric valve or the like once, it is sufficient to prepare a small battery.

Further, an electric valve and an air-operated valve are installed in parallel with the blast valve, and even if the blast valve does not start, the boric acid water 14 is injected into the core 2 by opening the electric valve or the air-operated valve. can do.

The above-mentioned reactor pressure vessel injection line 17 can be a line connected to the reactor pressure vessel 3 via another pipe such as an emergency core cooling system connected to the reactor pressure vessel 3.

Further, in the boiling water reactor 100 of the present embodiment, even if the control rods are successfully inserted, the core is not sufficiently cooled due to some factor, and the core may be melted by the decay heat. There is sex. In this case, the core 2 becomes a molten core (also called corium) while melting the control rods 36, and falls to the lower part of the reactor pressure vessel 3.

If the molten core continues to be uncooled thereafter, the reactor pressure vessel 3 may be damaged and the melt core may fall onto the bottom 18 of the reactor containment vessel directly below the reactor pressure vessel 3. After that, if appropriate water injection is performed into the reactor containment vessel 1 and the molten core is submerged, the molten core is cooled and solidified, and the accident is resolved.

On the other hand, in the borate water injection device of the present embodiment, in addition to the reactor pressure vessel injection line 17 from the borate water tank 13 to the reactor pressure vessel 3, the reactor pressure vessel 3 from the borate water tank 13 A reactor containment vessel bottom injection line 19 is provided toward the reactor containment vessel bottom 18 which is vertically downward from the lower end of the reactor.

The injection line 19 at the bottom of the reactor containment vessel is composed of a general metal pipe such as SUS.

Further, as shown in FIG. 2, the reactor containment vessel bottom injection line 19 is located on the surface of the reactor containment vessel bottom 18, and is the central portion of the reactor containment vessel bottom 18 which is directly below the reactor pressure vessel 3 in the vertical direction. After being guided to, the end is made into a dead end structure. The reactor containment bottom injection line 19 may be arranged inside a groove or the like formed on the surface of the reactor containment bottom 18.

When the melt core falls from the reactor pressure vessel 3 onto the bottom 18 of the containment vessel directly below, the melt core also falls on or around the injection line 19 at the bottom of the containment vessel. Further, even if the meltdown core falls only at a position deviated from the center of the reactor containment vessel bottom 18, the meltdown core expands on the reactor containment vessel bottom 18, so that the meltdown core expands on the reactor containment vessel bottom 18 in the process of expansion. Very likely to come into contact with the injection line 19.

The pipe of the injection line 19 at the bottom of the reactor containment vessel is heated by the dropped molten core, and the heat damages the piping.

When damaged, boric acid water 14 flows out from the damaged hole, boric acid is supplied to the molten core, and the boric acid reduces the risk of re-criticality.

In the boiling water reactor 100 of this embodiment, the following mechanism is provided as a cooling mechanism of the molten core in addition to the boric acid water injection device.

The vent pipe 11 and the lower dry well 5a are communicated with each other by the lower dry well water injection line 21. Further, a lower drywell water injection valve 20 is provided on the lower drywell water injection line 21 so as to be in a closed state during normal operation. It is desirable that the lower dry well water injection valve 20 be a melting valve.

With such a configuration, the atmosphere of the lower dry well 5a is heated when the molten core falls to the bottom 18 of the reactor containment vessel. The temperature rise in this atmosphere heats the lower drywell water injection valve 20. The lower drywell water injection valve 20 as a melting valve opens due to this temperature rise, and the cooling water of the suppression pool 8 is injected into the bottom 18 of the reactor containment vessel through the vent pipe 11 and the lower drywell water injection line 21. To. This water injection is done by gravity only and does not require power. The molten core is cooled by the injected cooling water, but since the boric acid water is supplied to the molten core by the above-mentioned boric acid water injection device, the re-criticality at the time of injecting the cooling water into the molten core is critical. The risk is further reduced.

Water may be injected into the melt core from the outside of the reactor containment vessel 1 (not shown), but even in this case, the boric acid water is supplied to the melt core by the boric acid water injection device of the present invention. The risk of re-criticality when injecting cooling water into the meltdown core is further reduced.

Further, in a nuclear power plant, even when the control rod 36 is inserted and the reactor is shut down, steam is generated in the core 2 due to the decay heat of the fuel. Further, since the main steam isolation valve 4a is closed, the pressure in the reactor pressure vessel 3 rises.

In such a case, the pressure rise of the reactor pressure vessel 3 is detected, the emergency condenser start valve (omitted for convenience of illustration) is opened, and the steam of the reactor pressure vessel 3 is used for emergency condenser. The steam flows into the vessel and is cooled by the emergency condenser pool water (omitted for convenience of illustration) and returned to water. After returning to water, it returns to the inside of the reactor pressure vessel 3 by gravity, contributes to the cooling of the core 2 again, and the pressure of the reactor pressure vessel 3 decreases.

Since the temperature of the emergency condenser pool water is low at the initial stage of starting the emergency condenser, the cooling capacity is limited until the emergency condenser pool water starts boiling. In such a case, if the pressure of the reactor pressure vessel 3 rises further, the main steam relief safety valve 6 opens, and the steam of the reactor pressure vessel 3 is guided to the surplus space in the suppression chamber 7. As a result, the steam is released into the suppression pool 8 in the suppression chamber 7 through the steam escape safety valve exhaust pipe 9 and the quencher 10 and condensed to suppress the pressure rise in the reactor pressure vessel 3.

Next, the effect of this embodiment will be described.

The boric acid water injection device of the first embodiment of the present invention described above is a device for injecting boric acid water 14 in a nuclear power plant provided with a reactor containment vessel 1 for storing a reactor pressure vessel 3 including a core 2. Therefore, a boric acid water tank 13 for storing the boric acid water 14 is provided inside, and the boric acid water tank 13 is arranged inside the reactor containment vessel 1.

According to the present invention, the heater for preventing the precipitation of boric acid can be removed from the conventional boric acid water injection device, the inspection items at the time of periodic inspection can be reduced, and the burden of inspection can be reduced. It can be put into operation at an early stage. Further, the cost of the equipment itself and the cost related to the maintenance of the equipment can be reduced. In addition, since a heater that requires power for operation is not required in an emergency, it is possible to improve safety in the event of power loss.

In the unlikely event that an accident at a nuclear plant progresses, the core melts, the reactor pressure vessel eventually breaks, and the molten core (hereinafter referred to as the molten core) melts on the floor of the reactor containment vessel. It may fall.

When the meltdown core falls on the floor surface of the reactor containment vessel in this way, the cooling water in the reactor containment vessel and the cooling water in the tank held outside are poured onto the floor surface of the reactor containment vessel to fill the floor. It is necessary to cool the melting core that has fallen on the surface and end the accident.

Here, when the core melts, the control rods in the vicinity of the core also melt at the same time, so that the molten core often contains boron contained in the control rods. Therefore, even if the molten core is cooled with cooling water, the possibility of re-criticality occurring is extremely low, but the boric acid water 14 stored in the boric acid water tank 13 is guided downward in the vertical direction from the lower end of the reactor pressure vessel 3. By further providing the reactor containment vessel bottom injection line 19, the possibility of this re-criticality occurring can be further reduced, and the safety in the event of an accident can be further improved.

Further, the reactor containment vessel bottom injection line 19 is arranged so as to pass directly below the reactor pressure vessel 3 in the vertical direction, so that the reactor containment vessel bottom is located at a position where the meltdown core is most likely to fall. The injection line 19 is arranged to increase the possibility of contact with the melting core. Therefore, the probability of injecting boric acid water can be further increased, so that the safety can be further enhanced.

Further, the boric acid water 14 stored in the boric acid water tank 13 is arranged on the reactor pressure vessel injection line 17 and the reactor pressure vessel injection line 17 for sending the boric acid water 14 to the reactor pressure vessel 3, and is operated normally. By further providing a boric acid water injection valve 16 that is closed at the time, boric acid can be effectively injected into the core 2 when ATWS occurs with a simple configuration.

Further, the boric acid water injection valve 16 is an blast valve that opens when a control rod insertion failure event occurs, so that power such as a pump for valve operation is not required. As a result, the pump and the emergency power supply for driving the pump can be removed, and the cost can be reduced. In addition, since power is not required for operation, safety can be improved in the event of power loss.

Further, since the boric acid water injection valve 16 is an electric valve or an air-operated valve that can be opened by the operator, boric acid water can be injected into the core 2 in an emergency without using a large-scale configuration. Can be configured.

Further, since the boric acid water injection valve 16 is composed of at least two or more valves arranged in parallel on the reactor pressure vessel injection line 17, it is more reliable that the boric acid water is not injected in an emergency. Since it can be avoided, it is possible to further improve the safety.

Further, the boric acid water tank 13 has a pressurizing device 15, and is pressurized and accumulated during normal operation, so that power for valve operation is not required, and an emergency drive is used. The power supply can be removed and the cost can be reduced. In addition, since power is not required for operation, safety can be improved in the event of power loss.

Further, since the boric acid water injection device is for a boiling water reactor, it is a very effective boric acid water injection device for a boiling water reactor whose containment vessel size is basically small.

<Example 2>
The boric acid water injection device of Example 2, which is one of the preferred examples for achieving the above-mentioned object, will be described with reference to FIG. FIG. 3 is a main system diagram of a boiling water reactor and a boric acid water injection device according to a second embodiment of the present invention. The same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. The same applies to the following examples.

Also in the second embodiment, the configuration of the entire plant and the shapes of the reactor pressure vessel injection line 17 and the reactor containment vessel bottom injection line 19 are the same as those of the first embodiment, and only the differences from the first embodiment will be described here. To do.

In the boiling water reactor 100A of the second embodiment, the boric acid water is so that the water surface position of the boric acid water 14 stored in the boric acid water tank 13A is higher than the water surface position of the reactor pressure vessel 3. The tank 13A is installed at a higher position in the vertical direction as compared with the first embodiment.

Further, the gas phase portion of the reactor pressure vessel 3 and the gas phase portion of the boric acid water tank 13 are connected by a pressure equalizing line 22, and the reactor pressure vessel 3 and the boric acid water tank 13 have the same pressure during normal operation. I keep it in.

In this embodiment having such a configuration, when the occurrence of ATWS is detected, an open signal is sent to the boric acid water injection valve 16 to open the blast valve. At this time, since the water level of the boric acid water 14 in the boric acid water tank 13 is higher than the water level in the reactor pressure vessel 3, the boric acid water 14 is injected into the reactor pressure vessel 3 due to the difference in head.

Other configurations and operations are substantially the same as those of the boric acid water injection device of the first embodiment described above, and details will be omitted.

The boric acid water injection device of Example 2 of the present invention also has almost the same effect as the boric acid water injection device of Example 1 described above.

Further, since the boric acid water tank 13A is arranged at a position where the water surface of the boric acid water 14 is vertically higher than the water surface in the reactor pressure vessel 3, no power is required for its operation. It is also possible to improve safety in the event of power loss. In addition, the pump and the emergency power supply for driving the pump can be deleted, and the cost can be further reduced. Further, as compared with the first embodiment, the boric acid water tank 13 which is a heavy object needs to be arranged at a higher position, but the pressurizing device 15 is not required, so that the cost can be further reduced.

<Example 3>
The boric acid water injection device of Example 3, which is one of the preferred examples for achieving the above-mentioned object, will be described with reference to FIGS. 4 to 6. FIG. 4 is a main system diagram of the boiling water reactor according to the third embodiment. 5 and 6 are schematic views showing the structure and operation of the boric acid water injection valve of the boric acid water injection device according to the third embodiment.

Also in the boiling water reactor 100B of Example 3, the structure other than around the boric acid water injection valve 16B is the same as that of Example 1 or Example 2, and here, only the difference from Example 1 or Example 2 is shown. explain.

First, the structure of the boric acid water injection valve 16B of this embodiment will be described with reference to FIG. In FIG. 4, the gas phase portion of the reactor pressure vessel 3 and the boric acid water injection valve 16B are connected by a pressure transmission pipe 23 so that the pressure of the reactor pressure vessel 3 is transmitted to the boric acid water injection valve 16B.

Next, the structure and operation of the boric acid water injection valve 16B will be described with reference to FIGS. 5 and 6.

In the normal state, as shown in FIG. 5, the valve body 26 of the boric acid water injection valve 16 is pressed against the valve seat 33 by the valve spring 27, and the flow path is closed during the normal operation. The valve body 26 is connected to the piston 28. Further, a pressure transmission pipe 23 is connected to one side of the piston 28, and the piston 28 has a structure in which a pressure difference between the reactor pressure vessel 3 and the reactor containment vessel 1 is applied.

Further, when ATWS occurs, the pressure in the reactor pressure vessel 3 rises significantly. Since the pressure in the reactor pressure vessel 3 is transmitted through the pressure transmission pipe 23, when the pressure in the reactor pressure vessel 3 rises and the pressure difference from the reactor storage vessel 1 becomes large, the piston 28 moves and the valve When the body 26 separates from the valve seat 33, the borate water injection valve 16B opens, and borate water 14 is injected into the core 2 in the reactor pressure vessel 3 via the reactor pressure vessel injection line 17.

Other configurations and operations are substantially the same as those of the boric acid water injection device of the first embodiment described above, and details will be omitted.

The boric acid water injection device of Example 3 of the present invention also has almost the same effect as the boric acid water injection device of Example 1 described above.

Further, when the boric acid water injection valve 16 is used as an blast valve as in the first embodiment, a control rod insertion failure detection mechanism 24 and a mechanism for generating a start signal of the blast valve are required. A boric acid water injection valve 16B, which is closed during normal operation and is configured to open in response to an increase in pressure inside the reactor pressure vessel 3, is like a blast valve. Since the valve can be passively opened during ATWS and the boric acid water 14 can be injected without a mechanism, a simpler configuration can be obtained.

As in the first embodiment, the boric acid water injection valve 16B that opens by pressure, the blast valve, the electric valve, and the air actuated valve are installed in parallel, and the boric acid water injection valve 16B that opens and closes by pressure does not start. In this case as well, the structure can be such that boric acid water is injected by opening the blast valve, electric valve, or the like.

<Example 4>
The boric acid water injection device of Example 4, which is one of the preferred examples for achieving the above-mentioned object, will be described with reference to FIG. 7. FIG. 7 is a schematic view showing a piping structure at the bottom of the reactor containment vessel of the boric acid water injection device according to the fourth embodiment of the present invention.

Also in the boiling water reactor 100C of Example 4, any one of Examples 1 to 3 is carried out except for the shape of the reactor containment vessel bottom injection line 19C extending horizontally on the reactor containment vessel bottom 18. Similar to the example. Further, the boric acid water injection valve 16 may have the structure of the third embodiment. Here, only the differences from the first to third embodiments will be described.

In the fourth embodiment, as shown in FIG. 7, the shape of the reactor containment vessel bottom injection line 19C on the reactor containment vessel bottom 18 is simply a dead end as in the reactor containment vessel bottom injection line 19 of the first embodiment. It is not a structure, but a loop shape at the lower part of the reactor pressure vessel 3 in the vertical direction.

Other configurations and operations are substantially the same as those of the boric acid water injection device of the first embodiment described above, and details will be omitted.

The boric acid water injection device of Example 4 of the present invention also has almost the same effect as the boric acid water injection device of Example 1 described above.

Further, the reactor containment vessel bottom injection line 19C has a loop shape at the lower part in the vertical direction of the reactor pressure vessel 3, so that the meltdown core has fallen to a position deviated from the center of the reactor containment vessel bottom 18. Even in this case, the meltdown core and the reactor containment vessel bottom injection line 19C can be brought into contact with each other at an earlier timing. Therefore, the boric acid water 14 can be more reliably injected into the bottom 18 of the reactor containment vessel, and the possibility that recriticality will occur earlier can be reduced.

<Example 5>
The boric acid water injection device of Example 5, which is one of the preferred examples for achieving the above-mentioned object, will be described with reference to FIG. FIG. 8 is a main system diagram of the boiling water reactor and the boric acid water injection device according to the fifth embodiment of the present invention.

The boiling water reactor 100D of Example 5 is also the same as that of any one of Examples 1 to 4 except for the shape of the reactor containment vessel bottom injection line 19D in the lower dry well 5a. Here, only the differences from the first to fourth embodiments will be described.

In the fifth embodiment, as shown in FIG. 8, the reactor containment bottom injection line 19D in the lower dry well 5a is branched from the reactor containment bottom injection line 19D, and the end thereof is an atom. A boric acid water pre-filling line 25 that is open in the reactor containment vessel 1 is provided.

Further, on the boric acid water pre-water filling line 25, a boric acid water pre-water filling valve 29 composed of an electric valve or the like that can be manually opened and closed by the operator is provided.

Other configurations and operations are substantially the same as those of the boric acid water injection device of the first embodiment described above, and details will be omitted.

The boric acid water injection device of Example 5 of the present invention also has almost the same effect as the boric acid water injection device of Example 1 described above.

In addition, when an event occurs in which the molten core may fall to the bottom 18 of the reactor containment vessel during operation of the nuclear power plant, water is injected from the outside of the reactor containment vessel 1 in advance and water is filled in advance. There is also.

On the other hand, as in this embodiment, the boric acid water pre-filling line 25, which is branched from the reactor containment vessel bottom injection line 19D and whose end is open in the reactor containment vessel 1, and the atom. The meltdown core may fall to the bottom 18 of the containment vessel due to the addition of the boric acid water pre-filling valve 29, which is located on the injection line 19D at the bottom of the containment vessel and can be operated by the operator. When a certain event occurs, the boric acid water pre-filling valve 29 can be opened by the operator's operation to supply boric acid water to the bottom 18 of the reactor containment vessel in advance before the meltdown core falls. Therefore, the risk of re-criticality can be further reduced even at the time of pre-filling.

<Example 6>
The boric acid water injection device of Example 6, which is one of the preferred examples for achieving the above-mentioned object, will be described with reference to FIGS. 9 and 10. FIG. 9 is a main system diagram of the boiling water reactor and the boric acid water injection device according to the sixth embodiment of the present invention, and FIG. 10 is the bottom injection line and the lower dry well ho of the reactor containment vessel according to the sixth embodiment of the present invention. It is a schematic diagram of the acid water injection valve.

The boiling water reactor 100E of Example 6 is also the same as that of any one of Examples 1 to 5 except for the shape of the reactor containment vessel bottom injection line 19E in the lower dry well 5a. Here, only the difference from the first to fifth embodiments will be described.

In the sixth embodiment, as shown in FIG. 9, the reactor containment bottom injection line 19E in the lower dry well 5a does not have a piping portion extending horizontally on the reactor containment bottom 18, and the piping portion thereof is not present. A lower drywell boric acid water injection valve 30 is provided at the end of the lower drywell 5a of the reactor containment vessel bottom injection line 19E. Further, the lower dry well boric acid water injection valve 30 is used as a melting valve.

The detailed structure of the lower drywell boric acid water injection valve 30 will be described with reference to FIG.

As shown in FIG. 10, in the lower drywell boric acid water injection valve 30, the end of the reactor containment vessel bottom injection line 19 is closed by the end plug 39 before the meltdown core falls. The weight 31 for opening the end plug 39 is fixed to the injection line 19 at the bottom of the reactor containment vessel by a melting valve fixing pin 38 made of a low melting point metal.

Therefore, when the melting core falls to the bottom 18 of the reactor containment vessel, the melting valve fixing pin 38 made of the low melting point metal is heated and melted. When the melting valve fixing pin 38 is heated and melted, the weight 31 falls under its own weight. The impact load at the time of this drop is transmitted to the swing lever 37 via the wire 32, and the arm 34 is rotated so as to push out the arm 34 around the fulcrum 40, and the swing arm 35 and the end plug 39 are released from being fixed by the arm 34. .. By releasing the fixing of the end plug 39, the boric acid water 14 is injected from the injection line 19 at the bottom of the reactor containment vessel.

The structure of the lower drywell boric acid water injection valve 30 is the same as that of the lower drywell boric acid water injection valve 20.

When the molten core falls to the bottom 18 of the reactor containment vessel in the reactor equipped with the boric acid water injection device of this embodiment, the atmosphere of the lower dry well 5a is heated. Due to the temperature rise in this atmosphere, the lower drywell boric acid water injection valve 30 is heated, the melting valve fixing pin 38 is blown, the valve is opened, and the boric acid water 14 is injected from the bottom injection line 19E of the reactor containment vessel. ..

Other configurations and operations are substantially the same as those of the boric acid water injection device of the first embodiment described above, and details will be omitted.

The boric acid water injection device of Example 6 of the present invention also has almost the same effect as the boric acid water injection device of Example 1 described above.

Further, since the reactor containment vessel bottom injection line 19E has a lower drywell boric acid water injection valve 30 at its end, the piping extending horizontally on the reactor containment vessel bottom 18 is deleted. This can improve workability when working in the reactor containment vessel for periodic inspections and the like.

<Others>
The present invention is not limited to the above examples, and includes various modifications. The above-mentioned examples have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations.

It is also 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. It is also possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

1: Reactor storage vessel 2: Core 3: Reactor pressure vessel 4: Main steam pipe 4a: Main steam isolation valve 5: Drywell 5a: Lower drywell 6: Main steam relief safety valve 7: Suppression chamber 8: Suppression pool 9 : Steam relief safety valve Exhaust pipe 10: Quencher 11: Vent pipe 11a: Vent pipe exhaust part 12: Diaphragm floor 13, 13A: Borate water tank 14: Borate water 15: Pressurizing device 16, 16B: Borate water injection valve (2nd valve)
17: Reactor pressure vessel injection line (third pipe)
18: Reactor containment bottom 19, 19C, 19D, 19E: Reactor containment bottom injection line (first pipe)
20: Lower dry well water injection valve 21: Lower dry well water injection line 22: Pressure equalizing line 23: Pressure transmission pipe 24: Control rod insertion failure detection mechanism 25: Boric acid water pre-filling line (second pipe)
26: Valve body 27: Valve spring 28: Piston 29: Boric acid water pre-filled valve (first valve)
30: Lower dry well boric acid water injection valve (melting valve)
31: Weight 32: Wire 33: Valve seat 34: Arm 35: Swing arm 36: Control rod 37: Swing lever 38: Melting valve fixing pin 39: End plug 40: Support point 100, 100A, 100B, 100C, 100D, 100E: Boiling water reactor

Claims (15)

A boric acid water injection device that injects boric acid water in a nuclear power plant equipped with a reactor containment vessel that stores a reactor pressure vessel containing a core.
A boric acid water tank for storing the boric acid water is provided inside.
A boric acid water injection device, characterized in that the boric acid water tank is arranged inside the reactor containment vessel. In the boric acid water injection device according to claim 1,
A boric acid water injection device further provided with a first pipe for guiding the boric acid water stored in the boric acid water tank vertically downward from the lower end of the reactor pressure vessel. In the boric acid water injection device according to claim 2.
The boric acid water injection device is characterized in that the first pipe is arranged so as to pass directly below the reactor pressure vessel in the vertical direction. In the boric acid water injection device according to claim 3,
The first pipe is a boric acid water injection device characterized by having a dead end structure. In the boric acid water injection device according to claim 3,
The first pipe is a boric acid water injection device characterized in that the lower portion of the reactor pressure vessel in the vertical direction has a loop shape. In the boric acid water injection device according to claim 3,
The first pipe is a boric acid water injection device characterized by having a melting valve at its end. In the boric acid water injection device according to claim 3,
A second pipe that is branched from the first pipe and whose end is open in the reactor containment vessel.
A boric acid water injection device which is arranged on the second pipe and further includes a first valve which can be operated by an operator. In the boric acid water injection device according to claim 1,
A third pipe for sending the boric acid water stored in the boric acid water tank to the reactor pressure vessel, and
A boric acid water injection device further provided with a second valve arranged on the third pipe and closed during normal operation. In the boric acid water injection device according to claim 8.
The second valve is a boric acid water injection device, which is a blast valve that opens when a control rod insertion failure event occurs. In the boric acid water injection device according to claim 8.
The boric acid water injection device is characterized in that the second valve is closed during normal operation and is configured to open in response to an increase in pressure inside the reactor pressure vessel. In the boric acid water injection device according to claim 8.
The second valve is a boric acid water injection device characterized by being an electric valve or an air-operated valve that can be opened and operated by an operator. In the boric acid water injection device according to claim 8.
The boric acid water injection device, wherein the second valve is composed of at least two or more valves arranged in parallel on the third pipe. In the boric acid water injection device according to claim 1,
The boric acid water tank has a pressurizing device, and is characterized in that the boric acid water injection device is pressurized and accumulated even during normal operation. In the boric acid water injection device according to claim 1,
The boric acid water tank is a boric acid water injection device characterized in that the water surface of the boric acid water is arranged at a position higher in the vertical direction than the water surface in the reactor pressure vessel. In the boric acid water injection device according to claim 1,
The boric acid water injection device is a boric acid water injection device for a boiling water reactor.

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