JPH0377095A - Vent device of reactor container - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a nuclear reactor containment vent device used in a nuclear power plant.

(Prior art) A reactor containment vessel (hereinafter referred to as a containment vessel) used in a nuclear power plant isolates a nuclear reactor in the event of an accident, and prevents radioactive fission products (hereinafter referred to as FP) from entering the reactor pressure vessel. Even if the FP is released to the outside, it acts as a barrier to the release of FP into the external environment, and is installed for the purpose of preventing radioactivity from being released into the external environment.

The containment vessel of a boiling water reactor (hereinafter referred to as BWR) is generally divided into a dry well and a wet well, and pressure suppression water is stored in the wet well. When designing a containment vessel, Japan's guidelines require that the design basis accident be strictly assumed, which is a loss of coolant accident (hereinafter referred to as LOCA) due to rupture of the reactor-subsystem piping. At the time of the LOCA, the water vapor in the dry well is guided into the pressure suppression water via the vent pipe, cooled and condensed, and the structure is designed to suppress the pressure increase in the containment vessel.

In a nuclear power plant with such a containment vessel, an abnormal event occurs, which is realistically impossible.
An accident in which the means for supplying cooling water into the reactor pressure vessel is lost for both regular and emergency purposes, resulting in a complete loss of the core cooling function, or an accident in which the heat removal function from the containment vessel is completely lost ( (hereinafter referred to as a "severe accident"), it is possible to take measures to ensure that the safety of nuclear power plants is not compromised.

Assuming a severe accident in which the core cooling function is completely lost or heat removal from the containment vessel is completely lost, the molten core (hereinafter referred to as molten core) and the concrete in the drywell will react. Co, which sometimes occurs
Non-condensable gases such as H2 accumulate within the containment vessel.

Pressure increases due to this phenomenon, or pressure due to steam generated in the reactor pressure vessel or wet well accumulating in the containment vessel due to the inability to remove decay heat energy from the reactor core from within the containment vessel. If the rise continues for a long time, there is a risk of overpressure damage to the containment vessel. In the event of such a severe accident, it is conceivable that the function of the containment vessel will be lost and FP will eventually be released into the environment.

As one of the devices to prevent damage to the containment vessel in the event of a severe accident, FP is removed using a filter or the like before the containment vessel reaches pressure that would cause overpressure damage.

Containment vessel venting devices have been developed for the purpose of releasing atmospheric gas within the containment vessel to the environment and suppressing increases in the internal pressure of the containment vessel, and have been proposed in some plants in other countries in recent years.

In addition, in nuclear power plants where multiple plants are located, gas in the wet well or dry well atmosphere of the plant that caused the severe accident is transferred to the dry well or wet well of the adjacent plant before the containment vessel suffers overpressure failure. A method has been proposed in which the gas containing FP is confined within the containment vessel of an adjacent plant. Furthermore, if the internal pressure of the containment vessel in the adjacent plant increases, particulate FP contained in the gas can be removed by guiding the gas led to the dry well of the adjacent plant into the pressure suppression water via the vent pipe. After being removed by scrubbing, the atmospheric gas transferred to the wet well gas phase is removed from the atmosphere outlet (
By releasing it into the environment from the exhaust tower), it suppresses the rise in internal pressure of the plant's containment vessel, which led to the severe accident. A containment vessel vent system is being considered.

(Problem S that 9i Akira is trying to solve) It is thought that in a severe accident, the containment vessel will be damaged by overpressure and a large amount of FP will be released into the environment.

Although the probability of a severe accident occurring is extremely small, considering the importance of the consequences, it is desirable to maintain the integrity of the containment vessel and prevent a large amount of FP from being released.

However, with conventional containment vessel venting equipment for adjacent plants at nuclear power plants where multiple plants are located, FP
Since the atmospheric gas containing FP is introduced into the dry well of the adjacent plant where the accident did not occur, FP adheres to the surfaces of various structures and equipment installed in the dry well.

Therefore, in order to reuse the adjacent plant, there was a problem in terms of property protection, in that sufficient cleaning and other treatments had to be carried out. Also, when venting, high temperatures and
When a large amount of high-pressure gas flows into the dry well of an adjacent plant, a large jet load acts on structures and equipment installed in the dry well, potentially causing damage to the structures and equipment. There was a safety problem in that the secondary load caused by the damaged equipment becoming a missile caused the loss of functions of systems and equipment important for safety.

The purpose of the present invention is to solve property protection problems and safety problems that may occur in adjacent plants by simply adding simple and low-cost equipment such as piping and valves in a nuclear power plant where multiple plants are located. It is an object of the present invention to provide a containment vessel venting device which avoids this and prevents the safety of a nuclear power plant from being lost even in the event of a severe accident.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a dry well that constitutes a part of the reactor containment vessel and accommodates the reactor pressure vessel, and a wet well that accommodates pressure suppression water. Well and
The dry well and the wet well are connected, and a vent pipe whose one end is opened into the pressure suppression water contained in the wet well is connected to the wet well gas phase part of the plant and the wet well of the adjacent plant. A first pipe that guides the gas in the wet well gas phase into the pressure suppression water of an adjacent plant, and a first valve that is installed in the first pipe and operates to open when guiding the gas from the plant to the adjacent plant. and a second pipe that connects the dry well of the plant and the wet well of the adjacent plant and leads the gas in the dry well of the plant into the pressure suppression water of the adjacent plant; A second valve that opens when guiding gas to an adjacent plant, and a third pipe that connects the wet well gas phase part and the atmosphere release port of the adjacent plant and leads the gas in the wet well gas phase part to the atmosphere release port. and a third valve that is installed in the third pipe and opens when releasing gas from an adjacent plant to the atmosphere.

(Function) In a containment vessel having a containment vent device configured in this manner, in the event of a severe accident, the core melts and the reactor pressure vessel is melted and FP is released into the dry well of the reactor containment vessel. If the internal pressure increases, the FP in the dry well
After passing through the pressure suppression water through the vent pipe, the gas containing the gas is led to the wet well gas phase. When the gas containing FP passes through the pressure-suppressing water, the process of rising through the water on bubbles removes the FP (scrubbing effect).

The gas that has reached the wet well gas phase is transferred to the first valve by opening the first valve installed in the first pipe that connects the wet well gas phase to the wet well of the adjacent plant where the accident has not occurred. It is led directly via piping to the pressure suppressed water stored in the wet well of the adjacent plant, without going through the dry well of the adjacent plant. As a result, after being scrubbed again in the pressure-suppressing water, the gas that reached the wet well gas phase will break the vacuum connecting the dry well and wet well gas phases as the pressure in the wet well gas phase increases. Flow into the drywell via a valve.

In addition, if the pressure inside the containment vessel of the adjacent plant increases after a sufficiently long period of time has elapsed in this way, a pipe installed in the third pipe connecting the wet well gas phase and the atmospheric release port (exhaust tower) will be removed. When the third valve is opened, the liquid is discharged to the outside environment through the third pipe. At this time, the gas in the dry well atmosphere is passed through the vent pipe and scrubbed again in the pressure suppression water, and then released from the wet well gas phase to the outside environment.

Furthermore, in the course of the resolution of the severe accident, the water level of the wet well of the plant in question rose, causing damage to the gas phase of the wet well of the plant and the web of adjacent plants. If the pipe connecting the towell is submerged in water, the gas in the dry well can be removed from the second pipe by opening a second valve installed in the second pipe connecting the dry well and the wet well of the adjacent plant. In the case where the gas is directly led to the pressure suppression water stored in the wet well of the adjacent plant through the wet well without passing through the dry well of the adjacent plant, the subsequent process is when the gas is led from the wet well gas phase to the wet well of the adjacent plant. It is similar to

In this way, in the event of a severe accident, when using the containment vessel of an adjacent plant to attenuate radionuclides including rare gases by alleviating the increase in pressure inside the containment vessel and delaying the release of FP to the external environment, By directing the gas directly into the pressure suppression water, rather than into a dry well in an adjacent plant,
Particulate F of atmospheric gas in the dry well of the adjacent plant
The P concentration is extremely reduced, making it possible to maintain structures and equipment within the dry well.

In addition, since the high temperature and high pressure gas during venting flows directly into the pressure suppression water, it may cause damage to systems and equipment important for safety due to jet loads in the dry well where various structures and equipment are installed. Damage and loss of function can be prevented.

(Example) An embodiment of the present invention will be described below with reference to FIG.

The reactor containment vessel 30 of the plant A is divided into two compartments: a dry well 2 and a wet well 3. The reactor pressure volume D1 is housed in the dry well 2, and the pressure suppression water 4 is housed in the wet well 3. A vent pipe 5 is installed between the dry well 2 and the wet well 3 to guide the atmospheric gas inside the dry well into the pressure suppression water 4 when the internal pressure of the dry well increases. A first pipe 6 that guides gas from the gas phase part of the wet well 3 into the pressure suppression water 10 accommodated in the wet well 9 in the reactor containment vessel 31 of the adjacent plant B.
is installed between the gas phase part of the wet well 3 and the wet well 9 of the adjacent plant B.

A first valve 7, which is normally closed and opens when the containment vessel is vented, is disposed in the first pipe 6. Furthermore, in order to guide the gas in the dry well 2 into the pressure suppression water IO of the adjacent plant B when the wet well 4 is flooded, a second pipe 15 is connected between the dry well 2 and the wet well 9 of the adjacent plant B. Connected with This second pipe 15 is normally closed, but when the pressure of the containment vessel increases, gas is transferred from the dry well 2 to the pressure suppression water 10 of the adjacent plant B.
A second valve 16 is provided which is opened when it is necessary to drain the water into the tank. In FIG. 1, two valves are connected in parallel as the first valve 7 or the second valve 16 from the viewpoint of improving reliability.
A valve is installed, but it is also possible to use a construction valve.

In the adjacent plant B, when the pressure in the wet well 9 increases, the gas in the wet well gas phase passes through the vacuum breaker valve 1.
7 into the dry well 8. Furthermore, when the internal pressure of the containment vessel in adjacent plant B increases, the wet well 9
In order to guide the atmospheric gas to the atmosphere discharge port (exhaust tower) 14, the gas phase part of the wet well 9 and the atmosphere discharge port (exhaust tower)
A third pipe 12 is installed between the pipes 14 and 14. This third pipe 12 is provided with a third valve 13 that is normally closed and opens when the containment vessel is vented. Note that this third valve 13 is configured as two valves in series from the viewpoint of preventing accidental opening.
It is also possible to use an L valve.

The first valve 7J, the second valve 16, and the third valve 13 use DC electric valves so that they can function even when all AC power is lost.
A variety of options are available, including the use of air-operated valves and loveture discs. In addition, a gas discharge device [18 in the shape of a straight pipe,
Various shapes such as a spherical shape with many small holes, a cross-shaped quencher, etc. are possible. In FIG. 1, reference numeral 11 indicates a vent pipe of an adjacent plant.

Next, a second embodiment of the present invention will be described with reference to FIGS. 2 and 3. FIG. 2 shows an embodiment in which the containment vessel vent system of the present invention is applied to an existing plant having a Mark-II type containment vessel.

When applying the vent system of the present invention to an existing plant, it is important to reuse existing piping and existing containment vessel penetrations in order to limit the scope of modification work. This makes it possible to avoid the major construction work of opening a new pipe through-hole in the containment vessel. The difference from the vent device shown in FIG. rather than being drawn directly into the adjacent plant B
A vent pipe 33 with one open end in the dry well 8 of
It is to be inserted or coupled within the dry well 8.

One method is to insert the first pipe 32 into the vent pipe 33 and extend it as it is to lead it into the pressure suppression water 10. Alternatively, the first pipe 32 can be connected directly to the vent pipe 33 by covering it. Another way is to do it. However, in both of these methods, the vent pipe 33
L, which is a design basis accident, reduces the opening area of L.
There is also a possibility that the original safety function of the vent pipe 33 may be impaired when OCA occurs. Therefore, more specifically, the following coupling method is used.

FIG. 3 is a detailed view showing details of one embodiment of the coupling portion. In FIG. 2, the dry well 8 of the vent pipe 33
The inner end branches into two, and one side is connected to a pipe 6 that leads gas from the wet well gas phase part 3 of the plant A to the pressure suppression water 10 of the adjacent plant B, and when the containment vessel is vented, , the gas is pressure-suppressed through the vent pipe 33 and the water 1
Lead to 0. The other end is open into the dry well 8, and is the original purpose of the vent pipe during LOCA within the dry well 8. This serves as a steam inlet 34 of a vent pipe 33 for guiding the steam in the dry well 8 into the pressure suppression water 10 for cooling and condensation. In addition, a valve 19 is installed at the fork in order to ensure that the gas (indicated by the solid line arrow in the figure) flowing into the vent pipe 33 from either of the gas inflow ports is introduced into the pressure suppression water 10. It is installed so that it operates in the direction of the arrow.

FIGS. 4(a) and 4(b) are a plan view and a longitudinal sectional view showing another embodiment of FIG. 3. In FIG. 4, the pipe 6 and the vent pipe 33 of the adjacent plant are connected via a check valve 20 in order to guide the atmospheric gas in the wet well gas phase section 3 into the pressure suppression water 10 of the adjacent plant B. The vent pipe 33 has two openings 35 that are connected to the dry well atmosphere via the check valve 20. Therefore, when a LOCA occurs in adjacent plant B, even if a single failure of the check valve 21 is assumed, the one on the healthy side of the check valve 21 will operate normally, so the function will be normal. It becomes possible to perform the function without any difference from the vent pipe 33. Furthermore, assuming a single failure (failure to open) of the check valve 20, it is also possible to divide the pipe 6 into two in the dry well 8 of the adjacent plant B and connect it to the two vent pipes 33. Furthermore, although the above-mentioned embodiment for an existing plant has been described as an example for a Mark-■ type containment vessel, it can be used in exactly the same manner for a Mark-1 type containment vessel employed in an existing plant.

〔Effect of the invention〕

If a severe accident occurs in a nuclear power plant that has this reactor containment vessel, and FP is released into the reactor containment vessel and its internal pressure rises at the same time, the free space of the reactor containment vessel of an adjacent plant When attenuating all FPs containing rare gases by using the volume to alleviate the increase in internal pressure in the reactor containment vessel of the plant, the gases contained in the FPs are directly guided into the pressure suppression water of the adjacent plant and removed by scrubbing. As a result, the amount of FP in the gas leading to the wet well gas phase and the dry well is extremely reduced, and there is almost no radionuclide contamination of structures and equipment in the dry well, making it possible to maintain the structures and equipment and protect property. This will have very beneficial effects from this point of view.

Furthermore, when the containment vessel is vented, systems and equipment important for safety in the dry well of an adjacent plant can be prevented from being damaged by high-temperature and high-pressure jet loads, thereby preventing loss of functionality. As a result, in the event of a severe accident, overpressure damage to the containment vessel can be prevented, and a large amount of FP can be prevented from being released into the environment.

[Brief explanation of drawings]

Fig. 1 is a schematic system diagram of a reactor containment vessel vent system showing a first embodiment of the present invention, and Fig.
- System outline diagram showing the second embodiment applied to a plant having a type II containment vessel, Fig. 3 is a detailed longitudinal section showing an enlarged view of part 0 of Fig. ) are the third
FIG. 7 is a plan view and a vertical sectional view showing a third embodiment of the portion corresponding to the figure. l... Reactor pressure vessel 2, 8... Dry well 3.9... Wet well 4.10... Pressure suppression water 6... First piping 12... Third piping 14 ...Atmospheric discharge port 16...Second valve A...The plant 5.11.33...Vent pipe 7...First valve 13...Third valve 15... 2nd piping B...adjacent plant Figure 3 C(L) Cb) Figure

Claims (1)

[Claims] A dry well that constitutes a part of the reactor containment vessel and accommodates the reactor pressure vessel; a wet well that accommodates pressure suppression water; A first pipe that connects a vent pipe opened into the pressure suppression water, the wet well gas phase part of the plant concerned, and the wet well of an adjacent plant, and guides the gas in the wet well gas phase part of the plant into the pressure suppression water of the adjacent plant. When installing the first pipe and guiding gas from the plant to the adjacent plant,
a first valve that operates to open; a second pipe that connects the dry well of the plant and the wet well of the adjacent plant and guides gas in the dry well of the plant into the pressure suppression water of the adjacent plant; The second pipe is installed in the piping and opens when guiding gas from the plant to the adjacent plant.
a third pipe that connects the wet well gas phase part and the atmospheric discharge port of the adjacent plant and guides the gas in the wet well gas phase part to the atmospheric discharge port; The third part opens when releasing gas to the atmosphere.
A nuclear reactor containment vessel venting device comprising: a valve;