JPH05264771A - Vent device for reactor containment - Google Patents

Abstract

PURPOSE:To release gas within a reactor storage container to a surrounding environment safely without expecting operation by a drive. CONSTITUTION:A first separation valve 17 is connected onto the upper side surface of a dry well 5a of a reactor containment 4 and a second separation valve 18 is connected onto the upper side surface of a suppression chamber 5b. The output sides of the first and second separation valves 17 and 18 are connected to an input side piping 25 of a main exhaust cylinder 11 and then a third separation valve 21 is connected to the output side of the input side piping 25. The output side of a third separation valve 21 is connected to the main exhaust cylinder 11. A water-level detection element 19 is provided at the input side piping 25, the water-level detection element 19 is connected to first and second control elements 20a and 20b, and then the first control element 20a and the second control element 20b are connected to the first separation valve 17 and the second separation valve 18, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor containment vessel for ensuring the integrity of the reactor containment vessel by safely discharging the gas inside the reactor containment vessel when the reactor is abnormal. Regarding the vent device.

[0002]

2. Description of the Related Art A boiling water nuclear power plant is protected by multiple defense facilities so that a large amount of radioactivity will not be released to the surrounding environment in the event of a nuclear reactor accident.

That is, as shown in FIG. 7, a reactor core 1
Is contained in a reactor pressure vessel 3 filled with cooling water 2, and the reactor pressure vessel 3 is contained in a reactor containment vessel 4 including a dry well 5a and a suppression chamber 5b. The dry well 5a and the suppression chamber 5b are connected by a vent pipe 14.

Usually, the heat generated from the core 1 is transferred to the cooling water 2 and used to rotate the power generation turbine. In the unlikely event that the pipe connected to the reactor pressure vessel 3 is broken and the cooling water 2 is cooled by the reactor pressure vessel 3. If it leaks out from the core, the core 1 will not be cooled, and the core 1 will be damaged by heat (referred to as decay heat).

In this case, the radioactivity contained in the reactor core 1 fills the reactor containment vessel 4 from the breakage of the pipe, while the decay heat generated from the reactor core 1 still causes the reactor containment vessel 4 to The internal temperature and pressure rise, eventually leading to destruction.

In order to prevent such a situation, in the existing boiling water nuclear power plant, the cooling water 6 stored in the suppression chamber 5b is supplied to the reactor pressure vessel 3 through the pump 7 and the heat exchanger 8. Water injection, core 1
There is provided equipment (called ECCS) for cooling the.

Therefore, if the ECCS is operating normally, an accident that damages the reactor core 1 does not occur. However, if the ECCS does not operate, the core 1 will not be cooled and will become hot, and the core 1 itself will melt and fall to the bottom of the reactor pressure vessel 3, and the core will also melt and melt. Will reach the bottom of the dry well 5a.

Since the molten core contains a large amount of radioactivity, in such a situation, the reactor containment vessel 4
The inside will be filled with a large amount of radioactivity together with a large amount of steam generated from the core. In this case, the reactor containment vessel 4
If it is damaged, radioactivity will come out of the containment vessel 4,
Large amounts of radioactivity may be released to the environment around the plant.

It is considered that such a situation that normally occurs when the ECCS does not operate normally is not possible, but studies are underway to cope with such a situation. That is, as shown in FIG. 7, the dry well 5a and the suppression chamber 5b are connected to the main exhaust pipe 11
Are connected with pipe 9 and a double isolation valve is provided in the middle of pipe 9.
A facility equipped with 10a and 10b is considered.

This is because when ECCS does not operate normally,
As described above, even if the internal pressure of the reactor containment vessel 4 rises, by opening the isolation valves 10a and 10b, the gas in the reactor containment vessel 4 is released to the atmosphere via the pipe 9. It is possible to prevent damage due to an excessive rise in the internal pressure of the reactor containment vessel 4.

The equipment including the pipe 9, the isolation valves 10a and 10b, the main exhaust pipe 11 and the like is called a reactor containment vessel vent device. Further, as another facility for dealing with the case where the ECCS does not operate normally, the external water source 12 to the water supply pump 13,
Dry well 5a through water pipe and other isolation valve 10c
A water injection facility for the reactor containment vessel for injecting cooling water into the reactor and cooling the reactor containment vessel 4 is also under study.

Here, the operation method of the reactor containment vessel vent device and the reactor containment vessel water injection equipment will be described.
In the unlikely event that the ECCS does not operate normally, the cooling water is supplied from the water injection facility of the PCV 4 to the external water source.
The water is pumped into the dry well 5a from 12 through the water supply pipe by the water supply pipe 13. The cooling water flows from the dry well 5a into the suppression chamber 5b through the vent pipe 14, and the amount of the cooling water 6 stored in the suppression chamber 5b gradually increases.

On the other hand, when the internal pressure of the reactor containment vessel 4 rises, the isolation valve 10b on the suppression chamber side is opened, and the gas in the suppression chamber 5b is discharged into the main exhaust pipe 11
Perform the operation of releasing from the outside. For this reason,
When the amount of the cooling water 6 exceeds the outlet nozzle 15 of the suppression chamber 5b, the cooling water flows out through the pipe 9 and the radioactivity contained in the cooling water is released to the external environment. ..

Therefore, the water level of the cooling water 6 is determined by the outlet nozzle.
Isolation valve 10 on the suppression chamber side at a height of 15
It is necessary to take an operating method of releasing the pressure in the reactor containment vessel 4 by closing b and closing the isolation valve 10a on the drywell side.

It should be noted that releasing the gas from the suppression chamber 5b side is a measure for reducing the amount of radioactivity released to the external environment as much as possible, since the radioactivity has the property of being easily collected by water. ..

[0016]

As described above, the venting device for the reactor containment vessel first vents from the suppression chamber 5b side during operation, and then the cooling water 6 in the suppression chamber 5b increases. However, if the suppression chamber 5b side cannot continue venting, the operation of venting from the dry well 5a side is required, and the operator's work such as water level monitoring and valve operation is required.

However, in the unlikely event that the operator fails to operate, the cooling water containing radioactivity will be released to the outside, and this has the problem of exerting a great influence on the surrounding environment. Expensive equipment is desired.

The present invention has been made in order to solve the above problems, and switches the vent position from the suppression chamber to the dry well without expecting the operation of the operator to safely surround the gas inside the reactor containment vessel. An object is to provide a vent device for a containment vessel for release to the environment.

[0019]

According to the present invention, a first isolation valve is connected to an upper side surface of a drywell of a reactor containment vessel,
A second isolation valve is connected to an upper side surface of the suppression chamber, outlet sides of the first and second isolation valves are connected to an inlet side pipe of a main exhaust pipe, and an outlet side of the inlet side pipe is a third side. Isolation valve is connected, the outlet side of the third isolation valve is connected to the main exhaust pipe, a water level detecting element is provided in the inlet side pipe, and the water level detecting element is the first and second control elements. And the first control element is electrically connected to the first isolation valve, and the second control element is electrically connected to the second isolation valve.

[0020]

When the gas in the reactor containment vessel is vented, the source of vent gas is changed from the suppression chamber side to the drywell side without requiring operator's operation.

[0021] For example, a venting method at the time of a severe accident is generally to vent from a suppression chamber,
Operate the valve to vent from the drywell when the suppression chamber is full.

A dry well side isolation valve or a suppression chamber side isolation valve is opened / closed by a water level gauge and a controller provided in a pipe between the suppression chamber and the main exhaust pipe. As a result, the burden on the operator can be reduced and erroneous operation can be prevented, which contributes to improving the reliability of the plant.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vent device for a containment vessel according to the present invention will be described with reference to FIGS. 1 to 6. In the figure, the same parts as those in FIG. 7 are designated by the same reference numerals, and overlapping description will be omitted.

The first isolation valve 17 is connected to the pipe 16a extending from the upper side surface of the dry well 5a of the reactor containment vessel 4, and the second isolation valve 18 is connected to the pipe 16b extending from the upper side surface of the suppression chamber 5b. Connecting. The outlet side of the first and second isolation valves 17 and 18 is connected to the inlet side pipe 25 of the main exhaust pipe 11.
The third isolation valve 21 is connected to the outlet side of the inlet side pipe 25. The outlet side of the third isolation valve 21 is connected to the main exhaust pipe 11.

A water level detection element 19 is provided in the middle of the inlet side pipe 25 located between the first isolation valve 17 and the second isolation valve 18. The water level detection element 19 is replaced with the first and second control elements 20.
Connect to a and 20b. The first control element 20a is electrically connected to the first isolation valve 17, and the second control element 20b is electrically connected to the second isolation valve 18.

However, the reactor containment vessel venting apparatus of this embodiment has the first and second isolation valves 17, 18 which can be operated remotely and which are installed on the pipes 16a, 16b from the dry well 5a and the suppression chamber 5b. , Inlet side pipe 25, water level detection element installed in the horizontal part of the inlet side pipe 25
19, control elements 20a, 20 for controlling the opening / closing operations of the first and second isolation valves 17, 18 by receiving signals from the water level detecting element 19
b, the remotely operable third isolation valve 21 and the main exhaust pipe 11 installed in the inlet side pipe 25 where the pipe 16a and the pipe 16b are joined.
Composed of.

Next, the operation of this embodiment will be described. As shown in FIG. 2, the first isolation valve 17 is closed and the second isolation valve 17 is closed.
When 18 is opened to vent the gas in the suppression chamber 5b, and when the cooling water is injected into the reactor containment vessel 4 by the water injection facility of the reactor containment vessel described above, the suppression chamber 5b becomes full, and the suppression chamber side outlet. Water rises from the nozzle 15 into the pipe 16b. At this time, as shown in FIG. 2, the difference between the water level 22 in the reactor containment vessel 4 and the water level 23 in the pipe 16b is equal to that obtained by converting the pressure in the dry well 5a expressed in gauge pressure into the water head. Become. (For example, if the inside of the dry well is 1 kg / cm ² g, the difference between the water level 22 and the water level 23 is 10 m).

If water injection and venting are continued thereafter, the water level 23 becomes equal to the installation height of the water level detecting element 19, as shown in FIG. In this state, the first control element 20a is operated by the signal from the water level detection element 19, and the first isolation valve 17 which was in the closed state until then is opened.

Then, the gas in the dry well 5a is piped.
Since the pressure released from 16a and equal to that in the dry well 5a is applied to the surface of the water level 23 in the pipe 16b, the water level 23 is pushed down from the state of FIG. 3 as shown in FIG. 4 and the water level 22 in the dry well 5a and the pipe. The water level 23 in 16b becomes equal.

The time from the state where the water level detecting element 19 shown in FIG. 3 captures the water level to the state where the two water levels (22 and 23) shown in FIG. 4 coincide with each other is about several seconds to 1 minute. The second isolation valve 18 is closed by a second control element 20b, which has a timer connected to the water level detection element 19 to be considered (FIG. 4).

If water is continuously supplied to the dry well 5a after that, the water level 22 of the dry well 5a becomes higher than the water level 23 in the pipe 16b as shown in FIG. Finally, as shown in FIG. 6, when the water level reaches the outlet nozzle 24 of the dry well 5a, water again flows to a certain point of the water level detection element 19 and an appropriate operation such as stopping water injection according to the signal is performed. carry out.

The pipes 16a and 16b need to be filled with water (there cannot be a pool of air) in order for the above operation to be performed without problems, so the pipes 16a and 16b are used as main exhaust pipes.
It is necessary that the piping structure does not have a downward slope on the 11th side.

As described above, in the reactor containment vessel venting apparatus according to this embodiment, when water enters the inlet side pipe connected to the main exhaust pipe, the water level is detected and the isolation valve is operated appropriately. Therefore, it is possible to more reliably prevent the cooling water containing radioactivity from being discharged to the outside of the containment vessel.

[0034]

According to the present invention, the water level detecting element is provided in the inlet side pipe connecting to the main exhaust pipe, and the dry well side isolation valve and the suppression chamber side isolation valve are operated by the signal of the element. Therefore, the vent source can be switched from the suppression chamber to the dry well without requiring the operation of an operator.

Therefore, the risk of releasing cooling water containing radioactivity to the surrounding environment can be reduced, which greatly contributes to the improvement of the reliability of the nuclear power plant.

[Brief description of drawings]

FIG. 1 is a piping system diagram showing an embodiment of a vent device for a containment vessel according to the present invention.

FIG. 2 is a piping system diagram showing an operating state of the vent device in FIG. 1 over time.

FIG. 3 is a piping system diagram showing a state in which the water level detecting element has captured the water level from the state of FIG.

FIG. 4 is a piping system diagram showing a state in which two water levels coincide with each other from the state of FIG.

FIG. 5 is a piping system diagram showing a state in which the water level of the dry well has increased from the state of FIG.

FIG. 6 is a piping system diagram showing a state in which the water level reaches the outlet nozzle of the dry well from the state of FIG.

FIG. 7 is a piping system diagram showing a conventional reactor containment head device.

[Explanation of symbols]

1 ... Reactor core, 2 ... Cooling water, 3 ... Reactor pressure vessel, 4 ... Reactor containment vessel, 5a ... Dry well, 5b ... Suppression chamber, 6 ... Cooling water, 7 ... Pump, 8 ... Heat exchanger,
9 ... Piping, 10a-10c ... Isolation valve, 11 ... Main exhaust pipe, 12 ... External water source, 13 ... Water supply pump, 14 ... Vent pipe, 15 ... Suppression chamber side outlet nozzle, 16a, 16b ... Piping, 17 ...
1st isolation valve, 18 ... 2nd isolation valve, 19 ... Water level detection element,
20a, 20b ... Control element, 21 ... Third isolation valve, 22, 23 ... Water level, 24 ... Drywell side outlet nozzle, 25 ... Inlet side piping.

Claims (1)

[Claims] 1. A first isolation valve is connected to an upper side surface of a dry well of a nuclear reactor containment vessel, and a second isolation valve is connected to an upper side surface of a suppression chamber. The outlet side is connected to the inlet side pipe of the main exhaust pipe, the outlet side of the inlet side pipe is connected to a third isolation valve, and the outlet side of the third isolation valve is connected to the main exhaust pipe, A water level detecting element is provided in the inlet side pipe, the water level detecting element is connected to first and second control elements, the first control element is provided in the first isolation valve, and the second control element is provided. Are electrically connected to the second isolation valves, respectively, and a vent device for a containment vessel.