JPH0534484A - Nuclear power plant cooling equipment - Google Patents

Abstract

(57) [Abstract] [Purpose] Exhaust the non-condensable gas in the heat transfer tube of the heat exchanger to transfer heat even when there is no difference between the drywell pressure in the reactor containment vessel and the suppression chamber pressure. Efficient decay heat removal is achieved by avoiding the accumulation of non-condensable gas in the tube. [Structure] Reactor pressure vessel 1 inside the PCV 11 and cooling water pool 6 for drywell cooler outside the PCV 11
A cooling water chamber 20 is installed between the inside and the heat exchanger 4. With this cooling water chamber 20, the heat exchanger 4, and the condensed water return pipe 17, the cooling water chamber 20
And the reactor pressure vessel 1 are connected by an emergency cooling system water injection pipe 19. Here, the height h ₁ of the connection point a of the condensed water return pipe 17 is higher than the height h ₂ of the connection point b of the emergency water injection pipe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer pipe of a heat exchanger in which steam generated by decay heat is stored in a cooling water pool outside a reactor containment vessel when an accident such as pipe breakage occurs. The present invention relates to a cooling facility for a nuclear power plant having a function of cooling the reactor containment vessel by condensing it and then returning it to the reactor pressure vessel again.

[0002]

2. Description of the Related Art In a boiling water nuclear power plant, as shown in FIG. 3, a reactor pressure vessel 1 accommodating a core 18 is installed in order to suppress the release of radioactive substances into the atmosphere at a sufficiently low level in the event of a coolant loss accident. A reactor containment vessel 11 is provided so as to surround it. This reactor containment vessel 11 is a reactor pressure vessel 1
Of the dry contain 7 and the steam and mixture discharged into the dry well 7 at the time of the loss of coolant by cooling and condensing with pool water through the pressure suppression vent pipe 9 to prevent excessive pressure in the reactor containment vessel 11. And a suppression chamber 8 for suppressing the rise of

An isolation capacitor is a system for removing decay heat without using a dynamic device such as a pump in the event of a nuclear reactor accident. As shown in FIG. 3, this is a steam supply that branches from the main steam pipe 2 connected to the reactor pressure vessel 1 and supplies steam to the steam chamber 14 of the heat transfer pipe provided at the inlet of the heat exchanger 4. Tube 3, heat exchanger 4 having a bundle of heat transfer tubes contained in a cooling water pool 6 outside the reactor containment vessel 11, a water chamber for heat transfer tubes provided at the outlet of the heat exchanger 4 for circulating condensed water 16, a condensed water return pipe 5 connecting the reactor pressure vessel 1, a water chamber 16 of the heat transfer pipe for exhausting the non-condensable gas accumulated in the heat transfer pipe, and an exhaust pipe 10 connecting the suppression chamber. It Note that reference numeral 12
Is a condensate return pipe valve, and 13 is an exhaust pipe valve.

By the way, the steam generated in the reactor pressure vessel 1 due to decay heat at the time of a nuclear reactor accident passes through the steam supply pipe 3 branched from the main steam pipe 2 into the cooling pool 6 outside the reactor containment vessel. The steam is guided to the heat transfer tube bundle of the heat exchanger 4 housed therein, and while the steam passes through the heat exchanger 4, heat is transferred between the steam and the pool water through the wall of the heat transfer tube, and the steam is condensed. Condensed water generated by this is returned by gravity to the reactor pressure vessel 1 through the condensed water return pipe 5. When the main steam pipe 2 is broken, the non-condensable gas present in the dry well 7 is passed through the broken main steam pipe 2 to the heat exchanger 4
Although mixed in the heat transfer tube inside, the non-condensable gas deteriorates the heat transfer performance, and thus is exhausted to the suppression chamber 8 via the exhaust tube 10. The isolation condenser starts heat removal by opening the valve 12 of the condensed water return pipe and the valve 13 of the exhaust pipe.

Since this system does not use a dynamic device such as a pump, it has a feature that high operation reliability can be expected.

A dry well cooler is known as another example of a system for performing decay heat of a nuclear reactor. For example, as shown partially in FIG. 1, a cooling water chamber 20 is provided at a position higher than the core 18 in the reactor pressure vessel 1,
In the event of a loss of coolant, the cooling water in the cooling water chamber 20 is injected into the reactor pressure vessel 1 via the water injection pipe 19 by using gravity as the final driving force. In a nuclear reactor having such an emergency core cooling system, a so-called gravity drop type water injection system, the drywell cooler is a steam supply pipe for supplying steam from the drywell 7 to the steam chamber 14 of the heat transfer tube.
15, a heat exchanger 4 in which a bundle of heat transfer tubes contained in a cooling pool 6 outside the reactor containment vessel, a water chamber 16 for heat transfer tubes for circulating condensed water and an emergency cooling system cooling water chamber 20 It is composed of a condensate return pipe 17 connected thereto and an exhaust pipe 10 connecting the water chamber 16 of the heat transfer pipe and the suppression chamber 8 for exhausting the non-condensable gas accumulated in the heat transfer pipe. In the drywell cooler, all the valves installed in each pipe are normally opened, and when the pipe breaks, the pressure in the reactor containment vessel rises due to the loss of the coolant through the broken pipe. Since the decay heat removal is started automatically, the valve does not need to be operated compared to the isolation condenser, and higher reliability can be expected. Further, water generated by condensation in the heat exchanger is finally returned to the reactor pressure vessel 1 through the emergency cooling system water injection pipe 19 of the gravity water injection system.

[0007]

In the drywell cooler, when the non-condensable gas present in the drywell 7 flows into the heat transfer tube of the heat exchanger 4 via the steam supply tube 15, the heat transfer tube is thereby heated. There is a problem that the condensation heat transfer on the wall deteriorates. The deterioration of heat conduction due to the non-condensable gas is characterized in that the heat transfer is greatly impeded even by the presence of a slight amount of the non-condensable gas.

That is, it has been experimentally confirmed that when the mass ratio of the non-condensable gas is 10% of that of the steam, the heat transfer coefficient deteriorates to about 20% of that in the absence of the non-condensable gas. Therefore, in order not to deteriorate the heat removal characteristics of the drywell cooler, it is desirable to eliminate accumulation of non-condensable gas in the heat transfer tube as much as possible.

An exhaust pipe 10 is provided as a means for exhausting the non-condensable gas. The exhaust pipe 10 is opened to the pool water in the suppression chamber 8, and the depth of submersion in the pool water is shallower than that of the pressure suppression vent pipe 9. Sufficient exhaust is performed in a situation where the drywell pressure is higher than the pressure in the suppression chamber 8, but in a situation where there is no difference between the pressure in the drywell 7 and the pressure in the suppression chamber 8, the exhaust pipe 10 Since the pool water of the suppression chamber 8 is sucked into the open end and the exhaust pipe 10 is sealed with water, sufficient exhaust may not be performed. In addition, dry well 7
In such a situation that the pressure in the drywell 7 decreases due to the cooling of the pool, intake of pool water into the exhaust pipe 10 increases,
As the water level in the exhaust pipe 10 rises, the non-condensable gas existing in the exhaust pipe 10 is pushed back to the heat transfer pipe side, and the gas accumulation in the heat transfer pipe is accelerated.

The present invention has been made to solve the above problems, and its purpose is to transfer heat to a heat exchanger even in a situation where there is no difference between the pressure in the drywell in the containment vessel and the pressure in the suppression chamber. It aims to provide a cooling facility for a nuclear power plant that can efficiently perform decay heat removal by exhausting the non-condensable gas in the heat pipe and avoiding the accumulation of the non-condensable gas in the heat transfer pipe. ..

[0011]

The present invention is directed to a reactor pressure vessel for accommodating a core, a reactor containment vessel for accommodating the reactor pressure vessel, and a reactor vessel in the reactor containment vessel and higher than the core. A cooling water chamber for storing emergency cooling water provided at a position, an emergency cooling system water injection pipe connecting the lower part of the cooling water chamber and the reactor pressure vessel, and provided outside the reactor containment vessel A heat exchanger stored in the cooling water pool, a steam supply pipe connecting the dry well of the reactor containment vessel and the steam chamber at the heat transfer pipe inlet of the heat exchanger, and the heat transfer of the heat exchanger. An exhaust pipe that connects the water chamber at the heat pipe outlet and the suppression chamber in the reactor containment vessel, and condensed water that connects the water chamber at the heat transfer pipe outlet of the heat exchanger and the cooling water chamber that stores the emergency cooling water. It consists of a return pipe and the emergency cooling system water injection pipe Connection height at serial cooling water chamber is characterized by being located below the connection level of the cooling water chamber of the condensate return pipe.

[0012]

According to the present invention, the cooling water chamber 20 of the condensed water return pipe 17 is
Due to the connection height to the emergency cooling system water injection pipe 19 and the cooling water chamber 20 being higher than the following, the following situation occurs. That is, the water level in the cooling water chamber 20 of the emergency core cooling system decreases as the water injection of the emergency cooling system progresses, and finally the water level is the connection height between the emergency cooling system water injection pipe 19 and the water chamber 20. As a result, the water level eventually becomes lower than the opening height of the condensed water return pipe 17 of the drywell cooler to the cooling water chamber 20, and the open end of the condensed water return pipe 17 to the cooling water chamber 20 is the cooling water chamber 20. It will be opened to the space. When the pressure in the dry well 7 is higher than the pressure in the suppression chamber 8, sufficient exhaust is performed through the exhaust pipe 18 leading to the suppression chamber 8. On the other hand, even in a situation where there is no difference between the pressure in the dry well 7 and the pressure in the suppression chamber 8 and the open end of the exhaust pipe 18 leading to the suppression chamber 8 is water-sealed, the cooling water chamber of the condensed water return pipe 17
Since the open end to 20 is open to the space of the cooling water chamber,
Since the cooling water chamber 20 is exhausted together with the condensed water through the condensed water return pipe 17, efficient decay heat removal can be performed while avoiding the accumulation of non-condensable gas in the heat transfer pipe.

In FIG. 2, the opening height of the condensed water return pipe 17 to the emergency cooling system cooling water chamber 20 is lower than the suction height of the emergency water injection system pipe 19, and the open end of the condensed water return pipe 17 is always sealed with water. 2 shows a comparison of the pressure change in the reactor containment vessel 11 when the main steam pipe 2 is broken when the cooling equipment of the present invention is used.

In the present invention, as is apparent from FIG. 2, it is recognized that good cooling is maintained even after the drywell pressure matches the suppression chamber pressure, and the pressure in the reactor containment vessel is reduced.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the cooling equipment for a nuclear power plant according to the present invention will be described with reference to FIGS. 1 and 2. In addition,
1, those parts which are the same as those corresponding parts in FIG. 3 are designated by the same reference numerals, and a description of the overlapping parts will be omitted.

This embodiment is different from the conventional example in that a cooling water chamber 20 is installed between the reactor pressure vessel 1 and the heat exchanger 4 in the cooling water pool 6, and the cooling water chamber 20 and the heat exchanger 4 are installed. 4 is a condensed water return pipe 17, and the cooling water chamber 20 and the reactor pressure vessel 1 are connected by an emergency cooling system water injection pipe 19.

Here, the height h ₁ of the connection point a between the cooling water chamber 20 and the condensed water return pipe 17 from the bottom of the cooling water chamber 20 is the connection point between the emergency cooling system injection pipe and the cooling water chamber 20. It must be higher than the height h ₂ from the bottom surface of the cooling water chamber 20 of b.

Next, the operation of the above embodiment will be described.

In FIG. 1, when a pipe rupture accident occurs, most of the non-condensable gas existing in the upper part of the dry well 7 is steam that flows out from the reactor pressure vessel 1 to the dry well 7 in several tens of seconds after the rupture. With pressure suppression vent pipe 9
Then, through the exhaust pipe 10 of the drywell cooler, it is transferred to the suppression chamber 8.

Therefore, except for immediately after the break, the heat exchanger 4
Although the content of non-condensable gas in the steam flowing into the heat transfer tube is small, there is a possibility that the non-condensable gas may accumulate in the heat transfer tube due to the condensation of the steam in the heat transfer tube. The condensable gas also causes the deterioration of heat transfer as described above.

When a loss of coolant accident (LOCA) occurs, high-pressure reactor water flows from the reactor pressure vessel 1 through the broken pipe into the reactor containment vessel, and as the pressure in the reactor containment vessel rises, the dryness increases. The mixture of steam and non-condensable gas flows into the heat exchanger 4 of the well cooler, and the heat removal by the dry well cooler is automatically started. At this time, when the pressure in the dry well 7 is higher than the pressure in the suppression chamber 8, sufficient exhaust is performed through the exhaust pipe 10 that communicates with the suppression chamber 8, so that non-condensable gas accumulates in the heat exchanger 4. Does not occur and good cooling is maintained.

On the other hand, as the reactor pressure vessel 1 is depressurized, water is injected from the emergency cooling system, and the reactor pressure vessel is supplied from the emergency cooling system cooling water chamber 20 through the emergency cooling system water injection pipe 19. The cooling water is replenished to No. 1. At this time, the water level of the cooling water chamber 20 decreases as the water injection progresses, but the opening height of the condensed water return pipe 17 to the cooling water chamber 20 is higher than the suction height h ₂ of the water injection pipe 19. Because h ₁ is high,
The water level finally drops to h ₂ , and the open end of the condensed water return pipe 17 is opened to the space of the water chamber 20.

Drywell 7 by drywell cooler
When the dry well pressure becomes equal to the wet well pressure, the pool water in the suppression chamber 8 is sucked into the exhaust pipe 1 leading to the suppression chamber 8 from the open end, and the open end of the exhaust pipe 10 becomes water. To be sealed. In such a situation, exhaust is not performed through the exhaust pipe 10, but since the condensed water return pipe 17 is open to the space part of the water chamber 20, the non-condensable gas together with the condensed water is cooled by the cooling water chamber 20. And the accumulation of non-condensable gas in the heat transfer tube is avoided. Even when the non-condensable gas existing in the exhaust pipe 10 recirculates through the exhaust pipe 10 as the pressure in the dry well 7 advances and the water level in the exhaust pipe 10 rises, Exhausted via the condensed water return pipe 17.

[0024]

According to the present invention, the non-condensable gas is exhausted from the heat transfer tube of the heat exchanger regardless of the magnitude relation between the pressure of the dry well and the pressure of the suppression chamber. Good cooling is achieved without accumulation of non-condensable gas.

[Brief description of drawings]

FIG. 1 is a piping system diagram schematically showing an embodiment of a cooling facility for a nuclear power plant according to the present invention.

FIG. 2 is a curve diagram for explaining the function and effect in FIG.

FIG. 3 is a piping system diagram schematically showing a cooling facility of a conventional nuclear power plant.

[Explanation of symbols]

1 ... Reactor pressure vessel, 2 ... Main steam pipe, 3 ... Steam supply pipe,
4 ... Heat exchanger, 5 ... Condensate return pipe, 6 ... Cooling water pool,
7 ... dry well, 8 ... suppression chamber, 9 ...
Pressure suppression vent pipe, 10 ... Exhaust pipe, 11 ... Reactor containment vessel,
12 ... Condensed water return pipe valve, 13 ... Exhaust pipe valve, 14 ... Heat transfer pipe steam chamber, 15 ... Steam supply pipe, 16 ... Heat transfer pipe water chamber, 17 ... Condensed water return pipe, 18 ... Core, 19 … Emergency cooling system water injection pipe, 20… Emergency cooling system cooling water chamber.

Claims (1)

Claim: What is claimed is: 1. A reactor pressure vessel for accommodating a core, a reactor containment vessel for accommodating the reactor pressure vessel, and a position higher than the core in the reactor containment vessel. A cooling water chamber for storing the provided emergency cooling water, an emergency cooling system water injection pipe connecting the lower part of the cooling water chamber and the reactor pressure vessel, and provided outside the reactor containment vessel A heat exchanger stored in a cooling water pool, a steam supply pipe connecting a dry well of the reactor containment vessel and a steam chamber at a heat transfer pipe inlet of the heat exchanger, and a heat transfer pipe output of the heat exchanger And an exhaust pipe connecting the suppression chamber of the reactor containment vessel, and a condensed water return pipe connecting the water chamber at the heat transfer pipe outlet of the heat exchanger and the cooling water chamber containing the emergency cooling water. Consisting of the cooling of the emergency cooling system injection pipe Nuclear power plant cooling equipment connected in the chamber height and being located below the connection level of the cooling water chamber of the condensate return pipe.