JPH06222182A - Static containment cooling system - Google Patents

Abstract

PURPOSE:To maintain long-term cooling performance so as to enhance the safety of a nuclear reactor by reducing the rate of pressure buildup within a suppression chamber without impeding the functions of a gravity drop type cooling system pool. CONSTITUTION:A heat exchanger 9a is provided within a static containment cooling system pool 8 and a condensed water line 11a and a gas vent pipe 12a are connected to the respective portions of the heat exchanger 9a. The condensed water line 11a is provided with a check valve 16. The check valve 16 prevents pool water in the gravity drop type cooling system pool 16 from flowing into a suppression pool 4. A gas bent branch pipe having a pressure regulating valve 18 is connected to the gas vent pipe 12a. Therefore uncondensed steam is not allowed to flow into a suppression chamber 5, while incondensible nitrogen shifts into the suppression chamber 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormal cooling system for a nuclear reactor, and more particularly to a static containment cooling system suitable as a long-term containment cooling system that does not use a pump.

[0002]

2. Description of the Related Art As a static containment vessel cooling system, there are known two types of configurations as shown in FIG. 4, for example. Figure 4
Is the first of two different types separated from the center line CL to the left and right
And the configuration of the second static containment cooling system A, B.

That is, the first static containment cooling system A shown on the right side and the second static containment cooling system B shown on the left side.
In both cases, a reactor pressure vessel 3 having a core 2 is installed in a containment vessel 1. Further, the inside of the storage container 1 has a space portion called a dry well 7.

A static containment vessel cooling system pool 8 is provided above the containment vessel 1, and heat exchangers 9a and 9b are installed in the pool 8 by being immersed in pool water.
Below the static containment vessel cooling system pool 8, a gravity drop type cooling system pool 6 and a suppression pool 4 are provided in two layers. The suppression pool 4 is provided in the suppression chamber 5.

Steam pipes 10a, 10b are provided in the heat exchangers 9a, 9b.
, Condensed water pipes 11a and 11b, and gas vent pipes 12a and 12b
Is connected to the first static containment vessel cooling system A side steam pipe
10a is the dry well 7 and the second static containment cooling system B
The side steam pipe 10b is connected to the main steam pipe 13.

The condensed water pipe 11a on the side of the first static containment cooling system A is connected to the gravity drop type cooling system pool 6, and the condensed water pipe 11b on the side of the second static containment cooling system B is connected. It is connected to the reactor pressure vessel 3. The gas vent pipes 12 a and 12 b are connected to the suppression pool 4, and their outlets are located below the water level of the suppression pool 4.

On the side of the second static containment cooling system B in which the steam pipe 10b is connected to the main steam pipe 13, the low water level signal in the reactor pressure vessel 3 is caused by the condensed water pipe 11b and the gas vent pipe 12b. The condensate water pipe control valve 14 and the gas vent pipe control valve 15 to be opened are connected.

However, at the time of abnormality due to breakage of the main steam pipe 13, the steam discharged to the dry well 7 is the steam pipe for both the first and second static containment cooling systems A and B.
After being condensed in the heat exchangers 9a and 9b through the heat exchangers 10a and 10b, and separated into a liquid phase and a gas phase in the lower plenum of the heat exchanger, the condensed water flows through the condensate water pipes 11a and 11b into the gravity drop cooling system pool 6 and the atom. It flows into the furnace pressure vessel 3.

Nitrogen which is a non-condensable gas and a part of uncondensed vapor which is filled in the containment vessel 1 which is sucked into the heat exchangers 9a and 9b together with the vapor is passed through the gas vent pipes 12a and 12b. It flows into the suppression pool 4. Particularly, after the breakage, the heat exchanger 9a,
The vapor that cannot be completely condensed in 9b remains, and in order to prevent the pressure in the suppression chamber 5 from rising, the outlets of the gas vent pipes 12a and 12b are submerged in water so that the uncondensed vapor is condensed by the water in the suppression pool 4. Immerse yourself.

[0010]

However, in the first and second static containment cooling systems A and B as described above, immediately after the main steam pipe 13 is broken, the pressure in the dry well 7 is reduced to the suppression chamber. Much higher than the pressure of 5. Therefore, the water in the gravity drop cooling system pool 6 flows into the suppression pool 4 through the condensed water pipe 11a, the lower plenum of the heat exchanger 9a, and the gas vent pipe 12a.

As a result, not only the pool water of the gravity drop type cooling system decreases, but also the amount of water in the suppression pool 4 increases and the pressure in the suppression chamber 5 rises.

[0012] Therefore, the conventional static containment cooling system has a problem in safety because it may impede the function of the gravity drop type cooling system and cause an increase in pressure of the suppression chamber 5.

Further, after a lapse of time after the occurrence of breakage,
Since the pressure in the gas vent pipes 12a, 12b is below the head of the suppression pool 4, the gas vent pipes 12a, 12b
Is in a water-sealed state. As a result, the gas vent pipe 12
The insides of a and 12b are filled with nitrogen, and finally the heat exchanger 9
The insides of a and 9b are also filled with nitrogen.

It is known that when the non-condensable gas remains in the heat exchanger, the vapor condensing performance is deteriorated. Therefore, the conventional first and second static containment cooling systems A and B are stored for a long time. There is a disadvantage in terms of container cooling.

The present invention has been made in order to solve the above problems, and prevents the flow of cooling water from the gravity drop type cooling system pool to the suppression pool at the initial stage of an abnormal state, thereby achieving a cooling performance longer than the conventional one. It is to provide a static containment cooling system that does not degrade.

[0016]

According to a first aspect of the present invention, a static containment vessel cooling system pool is provided above a reactor containment vessel.
A gravity drop type cooling system pool and a suppression pool are provided in two layers below the static containment vessel cooling system pool, and a heat exchanger is installed in the static containment vessel cooling system pool. Is connected to a gas vent pipe communicating with the suppression pool and a condensed water pipe communicating with the gravity drop cooling system pool, and the condensed water pipe is provided with a check valve or a flow restrictor. To do.

According to a second aspect of the present invention, a static containment vessel cooling system pool is provided above the reactor containment vessel, and a gravity drop type cooling system pool and a suppression pool are provided below the static containment vessel cooling system pool in two stages. A heat exchanger is installed in the static containment vessel cooling system pool, and the heat exchanger is a gas vent pipe communicating with the suppression pool and a condensate pipe communicating with the gravity drop cooling system pool. And a gas vent branch pipe branching from above the suppression pool and having a pressure control valve is provided in the gas vent pipe, and the outlet of the gas vent branch pipe is shallower than the outlet of the gas vent pipe. Characterized by being immersed in the pool.

According to a third aspect of the invention, a static containment vessel cooling system pool is provided above the reactor containment vessel, and a gravity drop type cooling system pool and a suppression pool are provided in two stages below the static containment vessel cooling system pool. A heat exchanger is installed in the static containment vessel cooling system pool, and the heat exchanger is a gas vent pipe communicating with the suppression pool and a condensate pipe communicating with the gravity drop cooling system pool. And a gas vent branch pipe having a pressure control valve branched from above the suppression pool is provided in the gas vent pipe, and an outlet of the gas vent branch pipe is located in the suppression chamber. And

[0019]

With the check valve or the flow restrictor provided in the condensed water pipe, it becomes possible to prevent the flow of water from the gravity drop type cooling system pool to the suppression pool in the early stage of an abnormality due to breakage of the main steam pipe.

Further, since the pressure control valve of the gas vent branch pipe opens only within a set range of the pressure in the gas vent pipe and the pressure in the suppression chamber, the pressure difference is large for a while after the break with a large amount of uncondensed vapor flow. Therefore, the pressure control valve is closed and the pressure in the suppression chamber is not increased.

After that, as the pressure difference becomes smaller, the pressure control valve opens, so that the nitrogen does not fill the gas vent pipe and moves to the suppression chamber through the gas vent branch pipe, and the nitrogen is introduced into the heat exchanger of the static containment cooling system. Does not accumulate, so the condensation performance does not deteriorate over a long period of time.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First to third embodiments of a static containment cooling system according to the present invention will be described with reference to FIGS.
Note that FIG. 1 is also applied to second and third embodiments described later.

In FIG. 1, a reactor pressure vessel 3 containing a core 2 is housed in a containment vessel indicated by reference numeral 1 in the figure. A static containment vessel cooling system pool 8 is provided above the containment vessel 1, and a gravity drop type cooling system pool 6 and a suppression pool 4 in a suppression chamber 5 are provided below the pool 8 in a two-tiered manner. ing.

In the static containment vessel cooling system pool 8, a heat exchanger 9a is installed so as to be immersed in the pool water. The steam pipe 10a connected to the heat exchanger 9a is a dry well in the containment vessel 1. It communicates with 7.

The tip of the condensed water pipe 11a connected to the heat exchanger 9a is immersed in the pool water in the gravity drop type cooling system pool 6. A check valve 16 is connected to the condensed water pipe 11a.

The tip of the gas vent pipe 12a connected to the heat exchanger 9a is immersed in the pool water of the suppression pool 4. A gas vent branch pipe 17 having a pressure control valve 18 is branched from a portion of the gas vent pipe 12a located inside the suppression chamber 5, and the tip end of the gas vent branch pipe 17 is shallowly immersed in the pool water.

A cooling water passage pipe 22 having a check valve 23 is connected between the lower part of the gravity drop type cooling system pool 6 and the lower part of the reactor pressure vessel 3 to cool the cooling water pool 6. The pool water flows into the reactor pressure vessel 3 to cool the core 2.

In the second embodiment, in the above configuration, the check valve 16 connected to the condensed water pipe 11a of the static containment cooling system.
Has the function of opening when the pressure on the heat exchanger 9a side of the valve is higher than the pressure on the gravity drop type cooling system pool 6 side. A flow restrictor may be connected instead of the check valve 16.

The gas vent pipe 12a is provided with a gas vent branch pipe 17 that branches from above the suppression pool 4, and the outlet thereof is connected to the suppression pool 4 by the gas vent pipe 12a.
It is immersed in a position shallower than the outlet of a.

In the third embodiment, in the above structure, the outlet of the gas vent branch pipe 17 is opened to the suppression chamber 5. The gas vent branch pipe 17 is provided with a pressure control valve 18. Other parts are the same as those in the first embodiment.

FIG. 2 shows an example of the analysis result when the main steam pipe 13 is broken in a certain reactor having a conventional static containment cooling system, in the gas vent pipe 12a and the suppression chamber 5. It shows the difference in the pressure. The pressure difference is large from about 5000 seconds to 10,000 seconds, and during this time, uncondensed vapor is discharged to the suppression pool 4 through the gas vent pipe 12a.

Therefore, in the static containment cooling system of this nuclear reactor, the pressure control valve 18 of the gas vent branch pipe 17 is set to 13 kPa.
If a valve with a mechanism that closes above a certain degree and opens below that is used, uncondensed vapor will not be released to the suppression chamber 5 and its pressure will not rise.

Further, in order to prevent backflow from the suppression chamber 5, the outlet of the gas vent branch pipe 17 is immersed in the suppression pool 4, and the depth thereof is about 10 ° C. after the end of the flow of uncondensed vapor as shown in FIG. Since there is a pressure difference of 3 kPa, it should be set below the equivalent water head (about 3 cm).

However, this value is a case of the static containment cooling system showing the analysis result of FIG. 2 and differs depending on its design.
In addition, the suppression chamber 5 to the gas vent branch pipe
In the case of a reactor and static containment cooling system design with no or little backflow to 17, it is also possible to open the outlet of the gas vent branch 17 to the suppression chamber as in the third invention.

The second and third embodiments can also be applied to a static containment cooling system of the type in which the steam pipe is connected to the main steam pipe.

By the way, as the pressure control valve 18 of the gas vent branch pipe 17, for example, the structure shown in FIG. 3 can be adopted. That is, the inclined pipe 17a of the gas vent branch pipe 17 branched from the gas vent pipe 12a is provided so as to be oblique to the upper left with respect to the horizontal direction. A spherical valve 19, a valve seat 20 with a gradually decreasing flow passage, and a valve drop prevention tool 21 in which the flow passage is secured are inserted into the inclined pipe 17a.

When the pressure on the gas vent pipe 12a side is high, a valve
When the valve 19 is lifted and comes into contact with the valve seat 20, the flow passage is closed, and when the pressure is reduced and the load of the valve is relatively increased, it rolls down to the valve fall prevention tool 21 and the flow passage is opened. By adjusting the size of the valve, the mass, and the angle of the flow path with respect to the horizontal direction, the valve can be opened and closed with a set pressure difference.
As the other pressure control valve, a mechanical or electric valve using a differential pressure gauge can be used.

In the static containment cooling system for a nuclear reactor constructed as in the above embodiment, the pressure in the dry well 7 immediately after breakage is considerably higher than the pressure in the suppression chamber 5, so that the gravity drop cooling system pool 6 That the pool water of the condensate pipe 11a may flow into the suppression pool 4.
It can be prevented by the check valve 16 provided in the or the flow restrictor.

Further, in order to prevent uncondensed vapor from flowing into the suppression chamber 5, the gas vent pipe 12a, which is water-sealed in the suppression pool 4, is connected to the gas vent pipe 12a.
After a long period of time, the non-condensable nitrogen is filled, and finally the heat exchanger 9a is also filled with nitrogen.

Therefore, the heat exchange performance deteriorates because the gas vent branch pipe 17 having the pressure control valve 18 prevents uncondensed vapor from flowing into the suppression chamber 5.
After the uncondensed vapor flow disappears, the nitrogen is transferred to the suppression chamber 5, and the time until the heat exchanger 9a is filled with nitrogen becomes long.

[0041]

According to the present invention, in the static containment cooling system, the pressure rise of the suppression chamber is suppressed without impairing the function of the gravity drop type cooling system, and the condensing performance in the heat exchanger is maintained for a long time. Because it can be maintained, safety is increased.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing first to third embodiments of a static containment cooling system according to the present invention.

FIG. 2 is a characteristic diagram showing an example of an analysis result relating to a difference between a pressure inside a gas vent pipe and a pressure inside a suppression chamber.

FIG. 3 is a vertical sectional view showing a gas vent branch pipe and a pressure control valve relating to the static containment cooling system of the present invention.

FIG. 4 is a configuration diagram showing two examples of a conventional static containment vessel cooling system.

[Explanation of symbols]

1 ... Containment vessel, 2 ... Reactor core, 3 ... Reactor pressure vessel, 4 ... Suppression pool, 5 ... Suppression chamber, 6
… Gravity drop type cooling system pool, 7… Drywell, 8… Static containment vessel cooling system pool, 9a, 9b… Heat exchanger, 10
a, 10b ... Steam pipe, 11a, 11b ... Condensed water pipe, 12a, 12
b ... Gas vent pipe, 13 ... Main steam pipe, 14 ... Condensate pipe control valve, 15 ... Gas vent pipe control valve, 16 ... Check valve, 17 ... Gas vent branch pipe, 18 ... Pressure control valve, 19 ... Valve, 20 ... Valve seat, 21 ...
Valve drop prevention device, 22 ... Cooling water flow pipe, 23 ... Check valve.

Claims (3)

[Claims] 1. A static containment vessel cooling system pool is provided above the reactor containment vessel, and a gravity drop type cooling system pool and a suppression pool are provided in two layers below the static containment vessel cooling system pool. A heat exchanger is installed in the static containment vessel cooling system pool, and the heat exchanger is connected to a gas vent pipe communicating with the suppression pool and a condensed water pipe communicating with the gravity drop cooling system pool. A static containment cooling system, wherein the condensed water pipe is provided with a check valve or a flow restrictor. 2. A static containment vessel cooling system pool is provided above the reactor containment vessel, and a gravity drop type cooling system pool and a suppression pool are provided in two layers below the static containment vessel cooling system pool. A heat exchanger is installed in the static containment vessel cooling system pool, and the heat exchanger is connected to a gas vent pipe communicating with the suppression pool and a condensed water pipe communicating with the gravity drop cooling system pool. The gas vent pipe is provided with a gas vent branch pipe branched from above the suppression pool and having a pressure control valve, and the outlet of the gas vent branch pipe is immersed in the suppression pool at a position shallower than the outlet of the gas vent pipe. A static containment cooling system characterized by being. 3. A static containment vessel cooling system pool is provided above the reactor containment vessel, and a gravity drop type cooling system pool and a suppression pool are provided in two layers below the static containment vessel cooling system pool. A heat exchanger is installed in the static containment vessel cooling system pool, and the heat exchanger is connected to a gas vent pipe communicating with the suppression pool and a condensed water pipe communicating with the gravity drop cooling system pool. The gas vent pipe is provided with a gas vent branch pipe branching from above the suppression pool and having a pressure control valve, and the outlet of the gas vent branch pipe is located in the suppression chamber. Containment vessel cooling system.