JPH04157396A - Natural cooling type container - Google Patents

Abstract

PURPOSE:To attain efficient thermal transfer from a drywell to a pressure suppression pool by providing a drywell opening of a vent pipe at a height whereat a water level in the drywell becomes equal to the water level in the pressure suppression pool on the occasion of an accident. CONSTITUTION:On the occasion of an accident wherein cooling water is lost, water of an accumulated water tank 17 flows into a reactor pressure vessel 2. When a water level in the vessel 2 becomes the same with a submergence level in a drywell 3, the water flows out from an opening on the drywell 3 side into a pressure suppression pool 6, and submergence cooling of a core 1 is attained first of all. On the occasion, a time for submergence is shortened and the necessary quantity of water is reduced by a structure 25 provided at the submergence level or below, and therefore the capacity of the tank 17 can also be reduced. Besides, an outflow into the pool 6 begins with the water of the highest temperature in the upper part of the drywell 3, and when the water level in the pool 6 reaches the submergence level, heat-transfer areas of the pool 6 and an outer peripheral pool 10 of a container and also the water temperature of the pool 6 become the maximum. Therefore a temperature difference between the two pools 6 and 10 becomes large, the amount of heat transmission can be made large and thus thermal transfer can be attained efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vent pipe structure from a dry well to a pressure suppression pool of a naturally cooled containment vessel, and the capacity of a water injection tank.

[Conventional technology]

As a conventional example A, as described in JP-A-63-191096 (see Fig. 2), for example, the main steam pipe 13 is ruptured and the water in the reactor pressure vessel 2 is blown down into the dry well 3. In this case, water is injected into the reactor pressure vessel 2 to flood the reactor core 1, and this water further overflows from the rupture port and is discharged into the dry well 3. This blowdown water and overflowing water cause the vent pipe to leak. After the water level in the dry well 3 rises to the 18 dry well 3 openings (opening above the pressure suppression chamber 7 space), these hot water flows into the pressure suppression pool 6 through the vent pipe 8. become.

In this case, since the opening of the dry well 3 of the vent pipe 8 is located high, the amount of water accumulated in the dry well 3 is large, and the rise in the water level of the pressure suppression pool 6 is small, so the contact area with the containment vessel outer peripheral pool IO is also constant. Not only is the size of the pressure suppression pool 6 limited, but also because a large amount of hot water accumulates in the dry well 3, the temperature rise of the pressure suppression pool 6 water is slow, and the temperature difference with the containment vessel outer peripheral pool 10 is small. Heat transfer from the pool 6 to the containment vessel outer peripheral pool 10 is also reduced. In other words, the cooling capacity of the containment vessel will also be kept low.

If the dry well opening of the vent pipe 8 is lowered, the amount of water accumulated in the dry well 3 will be reduced, the amount of water in the pressure suppression pool 6 will also be increased, and the amount of heat transferred to the containment vessel outer peripheral pool 10 will also be increased. In this case, even if the pressure inside the dry well 3 increases due to the hot water accumulated inside the dry well 3, the water level inside the dry well 3 cannot be pushed down easily (Pascal's (principle), the pressure inside the dry well 3 would rise excessively, reducing the safety of the containment vessel.

Therefore, it is necessary to specify the position to which the opening of the dry well 3 of the vent pipe 8 can be appropriately lowered.

Conventional example B described in Japanese Patent Application Laid-Open No. 58-2691 (see Fig. 3) is a containment vessel in which the dry well 3 is divided into an upper dry well and a lower dry well (CRD chamber). In addition to the vent pipe 8 from above, a vent pipe 26 from the lower dry well is provided, and the opening part of this vent pipe 26 on the dry well side! (Height) is made higher than the normal water surface of the pressure suppression pool 6 to prevent water from the pressure suppression pool 6 from flowing back into the dry well 3, which is different in structure and concept from the present invention. It is something.

However, the performance when the structure of Conventional Example B is applied to the vent pipe of the naturally cooling type containment vessel of the present invention will be compared with the present invention for reference.

As shown in FIG. 4, two types of vent pipes 8 and 26 are set up with different heights of the dry well side openings of the vent pipes.

The opening on the dry well 3 side of the lower vent pipe 26 has a design pressure difference of 1 in general between the dry well 3 and the pressure suppression chamber 7.
psid, which is about 0.7 m when converted to static water head, so it is considered here that it is located about 0.7 m above the water surface of the pressure suppression pool 6 in normal conditions. When the core coolant is blown down into the dry well 3 from the fracture opening 22, the water level in the dry well 3 rises, and when it reaches the height of the vent pipe 26 at the low opening, blowdown water flows into the water in the pressure suppression pool 6. The water level in the dry well 3 will not rise until the water level in the pressure suppression pool 6 reaches the low vent pipe 26 opening height. The water level in dry well 3 and the water level in pressure suppression pool 6 rise at almost the same level.

Eventually, the water injected into the reactor core will be stopped at the point where it satisfies the core submergence water level, so the opening of the high vent pipe 8 opens into the dry well 3 space, so it is necessary to An excessive pressure increase within the dry well 3 does not occur.

However, after the water level inside the dry well 3 reaches the vent pipe 26 population at the low opening, the blowdown water flows out into the pressure suppression pool 6, and as a result, the water level inside the dry well 3 and the water level of the pressure suppression pool 6 become the same. As the water level rises to
The time required for the water to reach the flood level will be significantly delayed. In addition, even after the dry well 3 is flooded, the hottest water at the top of the water in the dry well 3 does not transfer to the pressure suppression pool 6, so heat transfer from the dry well 3 to the pressure suppression pool 6 is Capacity decreases.

Therefore, even in the case of this conventional example B, the lower vent pipe 2
Unless the height of the 6 openings is set to an appropriate height according to the present invention, the performance of the naturally cooled containment vessel according to the present invention will not be achieved.

The conventional example C described in Japanese Patent Application Laid-Open No. 1-28479 has an opening 27 and a check valve 28 on the dry well side in the middle of the vent pipe, but is basically the same as the conventional example B. The same can be said. However, the water level inside the dry well 3 and the water level in the pressure suppression pool 6 are at the opening 2 in the middle of the vent pipe 8.
After exceeding 7, that is, after being immersed in water, the same phenomenon as in the conventional example A occurs, so it is possible that the pressure inside the dry well increases excessively.

[Problem to be solved by the invention]

As described above, in the conventional technology (Example A), the water level in the dry well reaches the flooding level quickly due to the blowdown water, but
Pressure suppression pool water level rise is small.

From the point of view of natural release from the containment vessel over a medium to long term, a large amount of heat transfer from the pressure suppression pool to the outer circumferential pool of the containment vessel cannot be achieved.

Further, in the conventional techniques (Example B) and (Example C), the water level in the dry well must reach the flooding level immediately after the accident for the purpose of cooling the core, but there is a drawback that there is a delay.

The present invention provides a pressure suppression pool to allow the water level in the dry well to reach the flooding level immediately after an accident to cool the reactor core, and to efficiently dissipate heat from the containment vessel, which is required in the medium to long term. It is an object of the present invention to provide a vent pipe structure that can increase the water level to the maximum extent and increase the heat transfer area to the outer peripheral pool of the containment vessel in contact with the pressure suppression pool.

Another object of the present invention is to selectively transfer the high-temperature water above the water inside the dry well to the pressure suppression pool, thereby increasing the temperature difference between the pressure suppression pool water and the containment vessel outer peripheral pool water. The aim is to improve the heat dissipation effect from the containment vessel.

[Means to solve the problem]

In order to achieve the above objective, the capacity W of the pressure accumulation water tank used for core cooling is set to [amount of water submerged in the dry well W,) +
[Amount of water required to make the pressure suppression pool water level the same as the flooding level in the dry well (pressure suppression pool water increase amount) W2]
And so.

In addition, the vent should be set so that [height of the opening of the vent pipe on the dry well side] = [dry well flooding level] = [normal pressure suppression pool water level + (pressure suppression pool water increase amount Wz/pressure suppression pool surface area)] The structure was such that the height of the opening on the dry well side of the tube was set.

Furthermore, a structure made of concrete or the like was installed in a space below the flooding level in the drywell to reduce the amount of flooding Wx in the drywell.

[Operation] If an accident occurs in which the reactor coolant (water) in the reactor pressure vessel is lost due to a rupture in piping, water in the pressure accumulator tank will flow into the reactor pressure vessel and cause the rupture. The water level in the dry well rises by flowing out from the mouth into the dry well. By the time the water level inside the dry well reaches the rupture port, the pressure inside the reactor pressure vessel has been sufficiently reduced. The water level also rises in the same way as the water level in the dry well, reaching the same level as the flooded level in the dry well. Therefore, although the flooding level of the dry well depends on the structure of the reactor pressure vessel, it is set sufficiently above the height of the reactor core inside the reactor pressure vessel, and the level of water in the dry well is set sufficiently above the height of the reactor core inside the reactor pressure vessel. If the rupture level of the 0M slave reactor pressure vessel, which is designed to adequately cope with evaporation, is higher than the flooding level of the dry well, the amount of water remaining in the reactor pressure vessel will increase accordingly, and eventually The amount of water transferred to the pressure suppression pool will be reduced by 9, but this will not affect the majority of people.

After the water level in the dry well reaches the submergence level, the water from the fracture will flow out from the opening on the dry well side of the vent pipe into the pressure suppression pool, allowing submergence cooling of the reactor core to be achieved directly. . At this time, the flooding time is further shortened by concrete and other structures installed below the flooding level in the drywell, and the amount of water required for flooding is also small, so the capacity of the pressure water tank, etc. that injects water into the reactor core is also reduced. I'll try it.

Next, the hot water at the top, which has the highest temperature in the dry well, flows through the vent pipe into the pressure suppression pool, and the pressure suppression pool water level and water temperature begin to rise until they reach the same level as the dry well side opening of the vent pipe. When the water level of the pressure suppression pool reaches the vicinity, the water in the pressure storage tank runs out, so water stops flowing into the reactor pressure vessel and also stops flowing into the pressure suppression pool.

As a result, the water level of the pressure suppression pool can reach the submergence level of the dry well, and the heat transfer area between the pressure suppression pool and the outer peripheral pool of the containment vessel can be expanded to the maximum extent. Moreover, since the pressure suppression pool water temperature is also maximized, the temperature difference between the pressure suppression pool and the containment vessel outer peripheral pool becomes large, so that the amount of heat transfer can also be increased.

In addition, heat dissipation from the containment vessel does not need to be effective immediately after an accident, but only after several tens of minutes or hours.
The present invention's sequence of first flooding the drywell (ie, core flooding cooling) and then transferring water to the suppression pool is most preferred.

〔Example〕

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

Figure 1 shows a naturally cooled containment vessel, in which a reactor pressure vessel 2 containing a reactor core 1 is located in a dry well 3, and a CRD chamber 4 located below the reactor pressure vessel 2.
and communicates with each other via the inner space of the gamma shield body 5. A pressure suppression chamber 7 having a pressure suppression pool 6 is located outside the dry well 3 , and the dry well 3 and the pressure suppression pool 6 are communicated through a vent pipe 8 . The opening height of the vent pipe 8 on the dry well 3 side is set at the submergence cooling level set above the reactor core 1, and the outlet on the pressure suppression pool 6 side is set at an appropriate water depth based on steam condensation experiments. ing.

The outer walls of the pressure suppression pool 6 and the pressure suppression chamber 7 are a steel containment vessel 9, and a containment vessel outer peripheral pool 1 is provided on the outside of the steel containment vessel 9.
0 is placed. The water depth of this containment vessel peripheral pool is set to increase the efficiency of heat transfer from the pressure suppression pool 6.
It is set to sufficiently cover the water depth of the pressure suppression pool 6 after the accident. After an accident, the temperature of the outer circumferential pool 10 of the containment vessel rises, and a discharge pipe 11 and a valve 12 are installed to release the generated water vapor to the outside.

Steam generated within the reactor pressure vessel 2 is sent to a turbine (not shown) through the main steam pipe 13, and is finally turned into water and returned to the reactor pressure vessel 2 through the water supply pipe 14. In the event of an accident, main steam isolation valve (MSIV) 15
is closed, and a check valve 16 is installed in the water supply pipe 14 to stop coolant such as water and steam from flowing out from the reactor pressure vessel 2. However, these MSIV1
5 or check valve 16, the reactor coolant in the reactor pressure vessel 2 will be released into the dry well 3, exposing the reactor core 1 and causing serious damage. This may lead to a serious accident (coolant loss accident).
Water can be injected into the reactor pressure vessel 2 from the pressure water tank 17 through an injection pipe 19 having a valve 18 .

This pressure water tank 17 is of the type that is pressurized from the beginning, or that connects the gas phase part of the reactor pressure vessel 2 and the pressure water tank 17 with a separate pipe only during injection, eliminating the pressure difference and increasing the reactor pressure only by the head. There are types that are injected into the reactor pressure vessel 2, and types that are injected after releasing the internal pressure of the reactor pressure vessel 2 and reducing the pressure with a safety valve (not shown). is an unnecessary configuration, so
Here, the pressure water tank 17, valve 18, and injection pipe 1 are simply explained.
Only 9 is listed. In addition, even if the injection is performed using a pump, there is basically no difference if the injection amount can be specified, so it can be handled in the same way.

Further, the pressure suppression chamber 7 and the dry well 3 are connected to the dry well 3 by a communication pipe 21 via a check valve 20.
It communicates only in the direction of.

Furthermore, in order to maintain the water level in the reactor pressure vessel 2 and the water level in the dry well 3 at the flooding level for a long period of time after the accident, a communicating pipe 25 and valves 23 and 24 are provided.

In this embodiment, a structure made of concrete or the like is installed along the outer wall of the dry well 3 by filling an empty base below the opening of the vent pipe 8 on the dry well 3 side to the extent that it does not impair workability such as installation and periodic inspection. 25 are installed. As a result, the water level in the dry well 2 after an accident quickly reaches the flooding level, and the capacity of the pressure water tank 17 can be reduced.

If the water supply plumber 4 were to break, the coolant (water and steam) in the reactor pressure vessel 2 would be released into the dry well 3 through the break port 22. Water among the released high-temperature coolant flows into the CRD chamber 4 at the bottom of the dry well 3, and the water level rises.

Since the released steam increases the pressure within the dry well 3, the water level within the vent pipe 8 is pushed down.

The atmosphere within the dry well 3 passes into the pressure suppression pool 6 water and transfers to the pressure suppression chamber 7. During this time, the steam in the atmosphere is condensed into water by the water in the pressure suppression pool 6, so
Only the air in the dry well 3 moves to the pressure suppression chamber 7,
The pressure increases by this amount. Due to an increase in the pressure in the dry well 3 or a decrease in the water level in the reactor pressure vessel 2, the reactor is automatically stopped, the MSIV 15 is closed, the steam supply is stopped, and the water supply from the water supply pipe 14 is also stopped. Then, the valve 18 is opened, and water is injected from the pressure water tank 17 into the reactor pressure vessel 2, and in the event of an abnormality in the reactor pressure vessel 2, a drop in water level is avoided, and core damage due to core overheating is prevented.

The temperature of the water injected into the reactor pressure vessel 2 rises due to the decay heat from the reactor core 1 and continues to flow into the dry well 2 from the fracture opening 22 as hot water. The water level rises and further reaches the inside of the dry well 2 and rises to the height of the opening of the vent pipe 8 on the dry well 2 side. Furthermore, since the hot water continues to flow out from the fracture opening 22, the hot water flows from the inside of the dry well 2 through the vent pipe 8 into the water of the pressure suppression pool 6, and the water level and water temperature of the pressure suppression pool 6 rise. When the water level of this pressure suppression pool 6 rises to the level of the dry well 2 side opening of the vent pipe 8, the accumulated water tank 17 becomes empty and the outflow from the break port 22 stops, so the water level of the pressure suppression pool 6 also rises. Stop.

Note that as the water level of the pressure suppression pool rises, the pressure in the pressure suppression chamber 7 also rises, but the check valve 20 operates due to the differential pressure between the pressure suppression chamber 7 and the dry well 3, and the pressure in the pressure suppression chamber 7 flows into the dry well 3. Since the air is returned and the pressure balance is maintained, the rise in the water level of the pressure suppression pool 6 is not hindered.

As the water temperature in the pressure suppression pool 6 increases, the steel containment vessel 9
Heat is transferred to the containment vessel outer peripheral pool 1o through the containment vessel outer peripheral pool 1o, and water vapor evaporated due to the rise in water temperature of the containment vessel outer peripheral pool 10 is released from the discharge pipe 11 by opening the valve 12.

When water is no longer injected from the pressure storage tank 17, the water level in the reactor pressure vessel 2, the water level in the dry well 3, and the pressure suppression pool 6 are at the same level, as shown in FIG.

After that, the decay heat generation from the reactor core 1 weakens, but the water in the reactor pressure vessel 2 continues to be heated and evaporated by the heat. Therefore, the pressure in the reactor pressure vessel 2 increases due to the generated steam. 1 The generated steam is released into the water of the pressure suppression pool 6 by a relief safety valve (not shown), or is released into the dry well 3 as hot water or steam from the fracture, and the pressure inside the dry well 3 increases. ,
The water in the vent pipe 8 will be forced down and discharged into the pressure suppression boule 6 where it will condense. Then, this heat continues to transfer to the containment vessel outer peripheral pool 1o and is radiated.

On the other hand, the water in the reactor pressure vessel 2 decreases due to evaporation, but if the valve 23 is opened in response to a drop in the water level, water from the pressure suppression pool 6 will flow into the reactor pressure vessel 2 due to the difference in water head. However, the water level in the reactor pressure vessel 2 recovers. Also, valve 2
4 is also opened, the water levels of the reactor pressure vessel 2, dry well 3, and pressure suppression pool 6 are maintained at the same flooding level.

As described above, according to this embodiment, in the event of an accident, the water level in the dry well 2 can quickly reach the flooding level, and the opening on the dry well 3 side of the vent pipe 8 can be prevented from being flooded. Since the water level of pressure suppression pool 6 can be raised to the maximum level, ■ core submersion cooling can be achieved quickly, and ■
The upper part of the dry well 2 where the water temperature is high should be transferred to the pressure suppression boule 6, and in the long term, the vent pipe 8
Since the internal water can be easily pushed down, steam condensation in the water in the pressure suppression pool 6 facilitates heat transfer from the dry well 3 to the pressure suppression pool 6, and furthermore, ■ from the pressure suppression boule 6 to the containment vessel outer peripheral pool 10. It is possible to secure a wide heat transfer area for heat transfer, and the temperature difference between the pressure suppression pool water and the containment vessel outer circumferential pool is also increased.

These allow core cooling, heat transfer from the dry well 2 to the pressure suppression pool 6, and pressure suppression pool 6.
Since heat transfer from the air to the containment vessel outer peripheral pool 10 can be efficiently achieved, the safety of the naturally cooled containment vessel is greatly improved.

Furthermore, since the water level inside the dry well 2 can be lowered than before, the capacity of the pressure water tank 17 can be reduced in addition to the installation of the structure 24 inside the dry well 2.

〔Effect of the invention〕

The present invention is constructed as described in one or more ways and provides the advantages described below.

Heat can be efficiently transferred from the dry well 3 to the pressure suppression pool 6, and the amount of heat transferred from the pressure suppression pool 6 to the outer circumferential pool of the containment vessel is greatly improved, so the performance as a naturally cooled reactor containment vessel is improved. , safety is greatly improved.

Furthermore, since the amount of water accumulated in the dry well 3 can be reduced, the core can be cooled quickly with water, improving the health of the reactor and further reducing the capacity of the pressure water tank 17.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a naturally cooled containment vessel according to an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view of a reactor containment facility according to a known example of the prior art (Example A), and FIG. 3 is a vertical cross-sectional view of a reactor containment facility according to the prior art. FIG. 4 is a vertical cross-sectional view of a reactor containment vessel according to a known example (Example B), and FIG. , FIG. 5 is a longitudinal sectional view showing a part of a reactor containment vessel of a known example (Example C) of the prior art. 1... Reactor core, 2... Reactor pressure vessel, 3... Dry well, 4... CRD chamber, 5... Gamma shield, 6... Pressure suppression pool, 7... Pressure Suppression room, 8
...Vent pipe. 9...Steel containment vessel-10...Containment vessel outer circumferential pool, 11...Discharge pipe, 12...Valve, 13...Main steam piping. 14...Water supply piping, 15...Main steam isolation valve (MSI)
V), 16... Check valve, 17... Pressure water tank, 1
8...Valve, 19...Water injection pipe, 20...Check valve,
21...Communication pipe, 22...Break port, 23...Valve,
24... Valve, 25... Structure, 26... Vent pipe for lower dry well, 27... Opening, 28... Check valve.

Claims (1)

[Scope of Claims] 1. In a naturally cooled containment vessel having a dry well, a pressure suppression pool, a vent pipe communicating the two, and a containment vessel outer peripheral pool installed in contact with the pressure suppression pool, A naturally cooled containment vessel characterized in that a dry well opening of a vent pipe is provided at a height where the water level in the dry well and the pressure suppression pool water level due to the release of reactor primary system coolant and core injection water are equal. 2. In the naturally cooled containment vessel of claim 1, water injection having [amount of water in the dry well W_1 equal to or higher than the core flooding level] + [amount of water W_2 required for the pressure suppression pool water level to be at the same level as the water level in the dry well] A naturally cooled containment vessel characterized by the provision of a tank. 3. In the natural cooling type containment vessel according to claim 2, the height h of the opening of the vent pipe on the dry well side is h=W_2/Apool, where h is the height from the water surface of the pressure suppression pool in normal times. W_2 is an increment in the amount of water in the pressure suppression pool; W_2 in claim 2
Same as. A naturally cooled containment vessel characterized by: