JPH02251794A - Cooling system for naturally heat releasing containment vessel - Google Patents

Abstract

PURPOSE:To enable a stable cooling-down after a loss-of-coolant accident by connecting a cooling device of cooling water circulation type to an upper pool with a circulation pipe. CONSTITUTION:An inside of a nuclear reactor containment vessel 6 is vertically divided into a dry well 3 and a wet well 5 having a suppression pool 4, and an upper pool 8 is provided above the containment vessel 6. Upper and lower plenum parts 9a and 9b of a cooling device 10, are connected to the upper pool 8 by an embedded piping 13a and 13b, and the piping 13a is extended into a water region of the pool 8. Also, one end of an atmospheric vent tube 12 is connected to an upper part of the pool 8, and another end is connected to a discharging tower 14. When a pipe breakage accident occurs, a steam filling the dry well 3 pushes down a water in the vent tube 7 and flows into the pool 4 to be condensed, with transferring a heat to a water in the pool 4. In case that the condensation progresses and a pressure goes down and therewith the steam does not flow into the pool 4, a stable heat removal can be always conducted even if a steam pressure in the dry well decreases, while supplying a low temperature water to a heat transfer tube 10a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a natural heat dissipation type containment cooling system suitable for cooling a reactor containment vessel in the event of a loss of coolant accident.

(Prior Art) A conventional reactor containment cooling system will be described using a boiling water reactor (hereinafter abbreviated as BWR) as an example.

FIG. 4 is a schematic diagram showing the main components of the cooling system of the containment vessel of a conventional BWR. A reactor pressure vessel 2 containing a reactor core 1 and a reactor containment vessel 6 containing primary system high pressure piping are partitioned into upper and lower parts by a diaphragm floor. The upper part of the reactor containment vessel 6 is called a dry well 3, and the lower part is called a wet well 5. The wet well 5 is provided with a suppression pool 4, and the pool 4 holds a large amount of cooling water. .

When the high-pressure piping in the primary reactor system ruptures and coolant spouts into the dry well 3, such as in a loss of coolant accident (LOCA), steam is guided into the suppression pool 4 through the vent pipe 7, Condensed by cooling water. The water temperature in the suppression pool 4 gradually rises due to decay heat released from the core 1 into the dry well 3 by emergency core cooling water. When the temperature of the cooling water in the suppression pool 4 rises, it becomes difficult for steam from the dry well 3 to condense, and the pressure in the reactor containment vessel 6 transfers the heat in the suppression pool 4 to the outer peripheral pool 11 of the containment vessel. By moving it, heat is released to the outside of the containment vessel, and the temperature of the water in the suppression pool 4 is prevented from rising.

(Problem to be Solved by the Invention) In the cooling system having the above configuration, in order to release the heat of the steam filling the dry well 3 to the containment vessel outer peripheral pool 11 through the wall of the reactor containment vessel 6, it is necessary to The water level of the vessel outer peripheral pool 11 must be made higher than the height of the wall surface of the reactor containment vessel 6 in which the dry well 3 is stored.

Therefore, the reactor containment vessel 6 needs to have a structure strong enough to withstand the water pressure of the containment vessel outer peripheral pool 11.

In addition, in the containment vessel outer peripheral pool 11, the heat transfer area is limited and there is less freedom in the installation location, resulting in poor heat transfer efficiency.
The temperature of the water in the suppression pool 4 increases, making it difficult for condensation to occur, and the pressure in the reactor containment vessel 6 may increase.

On the other hand, the high-temperature, high-pressure steam filling the dry well 3 passes through the vent pipe 7, pushes down the water in the vent pipe 7, flows into the suppression pool 4, transfers heat to the water, and condenses. As the condensation progresses, the pressure of the steam decreases, and there is no longer enough pressure to push down the water in the suppression pool 4, making it impossible to expect the water in the suppression pool 4 to remove heat.

In the event of an accident in which high-temperature, high-pressure steam leaks into the reactor containment vessel from pipes such as main steam, the present invention efficiently transfers the heat of the leaked steam through heat transfer tubes installed inside the reactor containment vessel. It is an object of the present invention to provide a cooling system for a natural heat dissipation type containment vessel, which allows rapid, stable and long-term cooling after a loss of coolant accident by allowing the coolant to escape to the upper pool.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a reactor pressure vessel, a wet well having a dry well and a suppression pool for storing the reactor pressure vessel, and a dry well and a sub-suppression pool. Natural heat dissipation type containment consisting of a vent pipe that connects the ledge complex pool, a reactor containment vessel that includes the vent pipe, dry well and wet well, and reactor pressure vessel, and a cooling device that cools the inside of the reactor containment vessel. In the vessel cooling system, an upper pool provided at the upper part of the reactor containment vessel, a cooling water circulation type cooling device provided in the dry well, and circulation piping connecting the cooling water inlet/outlet of the cooling device and the upper pool. It is characterized by consisting of.

(Operation) In the event of a loss of coolant accident (LOCA), etc., when the high-pressure piping in the sub-reactor system ruptures and coolant spews out into the dry well, or from the main steam piping etc. inside the reactor containment vessel. If an accident occurs in which high-temperature, high-pressure steam leaks, the heat of the leaked steam will be dissipated into the upper pool by the heat transfer tubes of the cooling device installed inside the dry well. Furthermore, even if the pressure of the leaked steam decreases, by efficiently dissipating heat to the upper pool through the heat transfer tubes, rapid cooling can be achieved after a loss of coolant accident.

(Embodiment) An embodiment of the cooling system for a natural heat dissipation type containment vessel according to the present invention will be described with reference to FIGS. 1 and 2.

Note that the same parts in the figure as in FIG. 4 will be described with the same reference numerals.

That is, in FIG. 1, a reactor pressure vessel 2 containing a reactor core 1 is housed within a reactor containment vessel 6. As shown in FIG. The reactor containment vessel 6 is installed in a concrete reactor building, and the steel plate is divided into lining≠well 5. An upper pool 8 is provided above the reactor containment vessel 6 . A cooling device 10 is provided within the dry well 3.

As shown in FIG. 2, this cooling device 10 has a large number of heat exchanger tubes 10a with their upper and lower ends connected to upper and lower plenum portions 9a.

9b, and circulation pipes 13a and 13b are connected to the upper and lower plenum parts, respectively. These circulation pipes 13a and 13b are connected to the external pool 8, and the upper circulation pipe 13a extends into the pool water of the external pool 8. One end of an atmospheric vent pipe 12 is connected above the upper pool 8, and the other end of the atmospheric vent pipe 12 is connected to a discharge base 14.

In the above-mentioned cooling system, if a piping rupture accident occurs for some reason during reactor operation, the steam filling the dry well 3 will be transferred to the vent pipe 7.
The high-temperature, high-pressure steam transfers heat to the water in the suppression pool 4 and condenses. As the condensation progresses, the pressure of the steam decreases, pushing down the water in the vent pipe 7 so that it no longer flows into the suppression pool 4, thereby reducing the heat removal effect of the water in the suppression pool 4.

On the other hand, external pool 8. Plenum part 9 and heat exchanger tube 10a
The inside is filled with water, and the heat of the steam filling the dry well 3 is transferred to the water in the heat exchanger tube 10a by the heat exchanger tube 10a. Therefore, the heated water is transferred to the upper plenum part 9a.
flows into the upper pool 8 through the water, diffuses, and transfers its heat to the water in the upper pool 8. The amount of water that has flowed into the upper pool 8 flows from the upper pool 8 through the lower plenum portion 9b and into the heat transfer tube 10a. In this case, low-temperature water flows into the heat transfer tube 10a, and even if the pressure of the steam in the dry well 3 decreases, stable heat removal can be performed at all times.

According to this embodiment, an upper pool 8 provided at the upper part of the reactor containment vessel 6, a plenum part 9a in the dry well 3,
A cooling device 10 having heat exchanger tubes 10a with heat exchanger tubes 9b attached to both upper and lower ends, the plenum parts 9a, 9b and an external pool 8.
Circulation piping 13a that connects.

13b@74, the heat of the steam is transferred to the water in the external pool 8 through the heat transfer tube 10a without affecting the pressure of the steam filling the dry well 3. This allows for rapid cooling of the reactor containment vessel in the event of loss of coolant, for example.

FIG. 3 shows another example of the cooling device shown in FIG. 2, and the same parts as in FIG. 2 are designated by the same reference numerals.

The difference between the example in FIG. 3 and FIG. 2 is that the heat exchanger tube tOa in FIG. 2 is pipe-shaped, and the upper and lower plenum parts 9a,
While 9b was composed of hemispherical parts, the 3rd
In the figure, the heat exchanger tube 10a has a flat plate shape, and upper and lower plenum parts 9
A and 9b are formed into rectangular shapes to increase the heat transfer area.

By forming the heat exchanger tube 10a and the plenum parts 9a, 9b of the cooling device 10 into square shapes in this manner, the same effect as in the example shown in FIG. 2 can be brought about, and the cooling efficiency can be further improved.

, that is, the upper pool 8. Plenum part 9a.

9b and the square heat exchanger tube 10a are filled with water, and the square heat exchanger tube 10a transfers the heat of the steam filling the dry well 3 to the water in the square heat exchanger tube 10a. The heated water flows into the upper pool 8 through the upper plenum portion 9a and is transmitted to the water in the upper pool 8. The water flowing into the upper pool 8 flows from the upper pool 8 to the lower plenum part 9b.
and flows into the rectangular heat exchanger tube 10a. In this case, stable heat removal can always be performed even if the steam pressure decreases.

According to this example, an upper pool 8 provided at the upper part of the reactor containment vessel 6, a rectangular heat exchanger tube 10a with a plenum part 9 attached in the dry well 3, and a circulation connecting the plenum part 9 and the upper pool 8. Piping 13a.

By providing 13b, the heat of the steam can be transferred to the water in the upper pool 8 through the rectangular heat transfer tube 10a without affecting the pressure of the steam filling the dry well 3.

[Effects of the Invention] According to the present invention, the heat of the steam leaking into the reactor containment vessel can be efficiently dissipated into the external pool without being affected by the pressure drop of the steam through the heat transfer tubes, thereby reducing the A natural heat dissipation type containment vessel capable of stable cooling after a loss accident can be provided.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical sectional view showing an embodiment of the cooling system for a natural heat dissipation type containment vessel according to the present invention, and FIGS.
The figures are a perspective view showing the cooling device used in Fig. 1, and Fig. 4 is a schematic vertical sectional view showing a conventional natural heat dissipation type containment vessel. 1...Reactor core 2...Reactor pressure vessel 3...Dry well 4...Suppression pool 5...Wet well 6...Reactor containment vessel 7...Vent pipe 8...Upper part Pools 9a, 9b...Plenum part 10...Cooling device 10a...Heat transfer tubes 11...Containment vessel outer circumferential pool 12...Atmospheric vent pipes 13a, 13b...Circulation piping 14...Release base (8733> Agent: Patent Attorney Yohan Yoshiaki (1 idiot) Me 1st Figure 4

Claims (2)

[Claims] (1) A reactor pressure vessel, a wet well containing a dry well and a suppression pool that stores this reactor pressure vessel, a vent pipe that connects this dry well and suppression pool, and this vent pipe/dry well and In a natural heat dissipation type containment cooling system consisting of a reactor containment vessel that includes a wet well and a reactor pressure vessel, and a cooling device that cools the inside of this reactor containment vessel, a cooling system is provided in the upper part of the reactor containment vessel. A cooling system for a natural heat dissipation type containment vessel, comprising an upper pool, a cooling water circulation type cooling device provided in the dry well, and circulation piping connecting the cooling water inlet/outlet of the cooling device and the upper pool. (2) The cooling system for a natural heat dissipation type containment vessel according to claim 1, wherein the cooling device comprises a plurality of heat exchanger tubes, both ends of which are tied together in a plenum.