JPH085772A - Reactor containment - Google Patents

Abstract

PURPOSE:To reduce the heat conduction area by forcedly sendings team mixed with inert gas during loss-of-coolant accidents, letting the steam forcedly touch the heat conduction pipe wall and raising the condensation efficiency. CONSTITUTION:When the coolant is discharged and the water level in a reactor pressure vessel 2 is lowered, a comparator opens a shut-off valve 51 by way of a valve operation controller from the comparison between the value of water level meter in the pressure vessel 2 and the value of low water level reference signal set in advance. By this, steam in the pressure vessel 2 is injected from a main steam pipe 78 into the drive port of a jet pump 52. Then the velocity of steam mixed with inert gas injected from the jet pump 52 into a condenser 80 increases. Due to the increase of the flow velocity, the inert gas and steam flow are disturbed and the steam easily touch the heat conduction pipe wall and the condensation effect thus increases.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a containment vessel for a nuclear reactor, and more particularly to a containment vessel for a nuclear reactor that suppresses a pressure increase in the containment vessel.

[0002]

2. Description of the Related Art Reactor equipment that removes decay heat generated from the core by a passive cooling mechanism that does not use dynamic equipment such as pumps when the coolant is lost, which must be assumed in the safety design of the reactor Proposed.

Japanese Patent Laid-Open No. 4-230893 discloses a structure in which vapor is sucked into a condenser from a dry well and condensed water generated in the condenser is supplied to a gravity falling water tank for injecting water into a core portion by using gravity as a driving force. There is a description about
The non-condensable gas that flows into the condenser together with the vapor and the uncondensed vapor that has not been completely condensed are discharged into the pressure suppression pool water through the gas discharge pipe, the non-condensable gas moves to the wet well, and the uncondensed vapor becomes Reactor equipment has been proposed that becomes part of the pressure suppression pool water by condensing in water.

[0004]

The dry well of the containment vessel is previously filled with nitrogen, which is a non-condensable gas,
In the event of an accident, there is a possibility that it will mix with the vapor discharged into the drywell and flow.

In the configuration of Japanese Patent Laid-Open No. 4-230893 of the above-mentioned known example, there is a route for discharging the non-condensable gas to the wet well, but during the discharge, the pressure of the dry well and the pressure of the wet well are changed. The difference becomes small, and the flow velocity of the non-condensable gas mixed vapor in the condenser decreases.

Then, the non-condensable gas comes to flow between the wall surface of the heat transfer tube and the steam, and the condensation of the steam is hindered.

As a result, the amount of heat radiation may be significantly reduced.

An object of the present invention is to provide a reactor containment vessel which can reduce the heat transfer area in the condenser.

[0009]

A characteristic constitution of the present invention for achieving the above-mentioned object is to provide a means for supplying the fluid in the dry well into the condenser when the coolant is lost.

[0010]

In the present invention, the non-condensable gas mixed vapor is forcibly sent to the condenser in the event of a coolant loss accident, which is an expected event.

As a result, the flow velocity of the non-condensable gas mixed vapor in the condenser increases, and the flow of the non-condensable gas and vapor in the heat transfer tube is disturbed.

The efficiency of condensation is increased by disturbing the flow and forcing the steam to contact the wall surface of the heat transfer tube.

Therefore, the wall surface area of the heat transfer tube can be reduced.

[0014]

1 and 2, the reactor containment vessel is a dry well 3, a pressure suppression chamber 4, and a gravity falling water tank 26.
, Jet pump 52, condenser 80, and piping 6
It consists of three.

The dry well 3 contains a nuclear reactor pressure vessel 2 containing the reactor core 1.

The pressure suppression chamber 4 is installed on the outer periphery of the dry well 3 and comprises a pressure suppression pool 5 and a wet well 6 which is a vapor phase space above the pressure suppression pool 5.

The gravity falling water tank 26 is located above the reactor core 1, and is connected to the reactor pressure vessel 2 via a pipe 27 provided with a check valve 29.

The jet pump 52 has a suction port 61 opened to the dry well 3, a discharge port 62 connected to a condenser 80 by a suction pipe 90, and a drive port 60 connected to a main steam pipe 78 via a shutoff valve 51. There is.

The main steam pipe 78 is connected to the reactor pressure vessel 2.

The condenser 80 is installed outside the dry well 3 and in the water of a condenser cooling pool 81 installed at a position higher than the core 1.

The gas discharge pipe 73 for discharging the non-condensable gas from the condenser 80 is inserted into the water in the pressure suppression chamber 4.

A condensed water discharge pipe 72 for discharging condensed water from the condenser 80 is inserted into the water in the gravity falling water tank 26.

The operation of this embodiment will be described with reference to FIGS. 1, 2 and 3.

The coolant loss accident is caused by damage to the reactor pressure vessel 2, piping, etc., and the cooling water in the reactor pressure vessel 2 is discharged into the drywell 3 as high-temperature and high-pressure steam from the damaged portion. .

This vapor is mixed with nitrogen, which is a non-condensable gas filled in the dry well 3, and becomes a non-condensable gas mixed vapor.

The dry well 3 is initially provided after the occurrence of the cooling accident.
Is higher than the pressure of the opening communicating with the pressure suppression pool 5 of the vent pipe 7, the non-condensable gas mixed vapor of the dry well 3 flows into the pressure suppression pool 5 through the vent pipe 7, and the vapor is pressurized. The non-condensable gas is condensed in the suppression pool 5 and accumulated in the wet well 6.

In the pressure suppression pool 5, the pool water near the outlet of the vent pipe 7 is gradually heated by the latent heat generated during vapor condensation, and the pool water temperature above the outlet of the vent pipe 7 becomes almost uniform by convection. To rise.

As this temperature rises, evaporation occurs from the pool surface, the vapor partial pressure in the wet well 6 also rises, and the pressure in the space rises, so that the non-condensable gas mixed vapor does not flow from the vent pipe 7.

The non-condensable gas mixed vapor also flows into the condenser 80 from the suction port 61 of the jet pump 52 through the suction pipe 90.

The driving force of this inflow is caused by the pressure difference between the dry well 3 and the wet well 6 and the instantaneous volume reduction due to the vapor condensation in the condenser 80.

Of the non-condensable gas mixed vapor flowing into the condenser 80, the vapor condenses and flows into the gravity falling water tank 26 through the condensed water discharge pipe 72, but the non-condensable gas flows through the gas discharge pipe 73. Through which it is discharged into the water of the pressure suppression pool 5.

The reason why the gas and water can be separated in this way is also due to the difference in the connection method between each discharge pipe and the condenser 80.

The difference is that the condensed water discharge pipe 72 is connected to the bottom surface of the condenser 80, whereas the non-condensable gas discharge pipe 73 is connected in a state of being inserted into the condenser 80. is there.

As a result, the condensed water accumulated on the bottom surface of the condenser 80 flows into the inlet end of the condensed water discharge pipe 72 at a position lower than the inlet end of the noncondensable gas discharge pipe 73, and conversely the noncondensable gas. Does not flow into the condensation discharge pipe 72 filled with water, but flows into the non-condensable gas discharge pipe 73.

At this time, the melting valve 64 installed at the tip of the pipe 63 is set to melt at the temperature at the time of the accident of loss of coolant but not at the temperature at the time of the accident of loss of coolant, so that it is in the closed state. The flow through the pipe 63 does not occur.

After that, since the coolant is discharged with the passage of time, the water level in the reactor pressure vessel 2 drops.

Then, the value of the water level gauge 83 for measuring the water level in the pressure vessel 2 shown in FIG. 3 is compared with the value of the preset low water level reference signal 85, and when the signal of the water level gauge 83 is small, the comparison circuit 84 Issues a valve opening signal to the valve actuation controller 86.

In response to this valve opening signal, the valve operation controller 86 opens the shut-off valve 51 which is normally closed.

As a result, the steam in the reactor pressure vessel 2 is injected from the main steam pipe 78 into the drive port 60 of the jet pump 52.

As shown in FIG. 4, this control system can be constructed so that it operates by measuring the pressure instead of measuring the water level.

The configuration of FIG. 4 differs from that of FIG. 3 in that a pressure measuring device 87 for measuring the pressure of the dry well 3 is provided in place of the water level gauge 83, and a preset high water level is used in place of the low water level reference signal 85. The pressure reference signal 88 is provided.

The operation of the apparatus shown in FIG. 4 will be described.

The value of the pressure measuring instrument 87 and the high pressure reference signal 88
Are compared, and the comparison circuit 84 issues a valve opening signal to the valve operation controller 86 when the signal of the pressure measuring device 87 is large. In response to this valve opening signal, the valve operation controller 86 opens the shutoff valve 51 which is normally closed.

By the operation of this control system, the steam in the pressure vessel 2 is supplied from the main steam pipe 78 to the drive port 60 of the jet pump 52.
Is injected into.

In the jet pump 52 shown in FIG. 2, the velocity and momentum of the steam flowing from the drive port 60 are increased by the nozzle 65 having a narrowed cross section.

The vapor molecules with increased momentum collide with the molecules of the non-condensable gas mixed vapor in the vicinity of the throat 67, and give momentum forward.

As a result, the suction of the non-condensable gas mixed vapor from the suction port 61 having a negative pressure is promoted.

The mixed gas is discharged from the discharge port 62 toward the suction pipe 90 after the pressure is restored by converting the speed head and the pressure head by the diffuser 66.

Due to the action of the jet pump 52 as described above, the flow rate of the non-condensable gas mixed vapor sucked from the suction port 61 is increased, and the pressure of the dry well 3 is increased.
Even when the pressure becomes lower than the pressure at the tip of the condenser, the pressure at the discharge port 62 of the jet pump 52 is high, so the condenser 8
The non-condensable gas in 0 is discharged to the pressure suppression pool 4 through the non-condensable gas discharge pipe 73.

After the accident of loss of coolant, the control rod 70
Is inserted and the fission reaction is stopped, but decay heat is generated for a long period of time thereafter, and the evaporation of the coolant and the discharge to the dry well 3 are continued.

Even at that time, since the vapor is continuously condensed by the above configuration, the pressure increase in the dry well 3 is also suppressed.

After the shutoff valve 51 is opened, the steam in the reactor pressure vessel 2 is discharged from the main steam pipe 78 to the outside of the reactor pressure vessel 2 through the shutoff valve 51. Gradually decreases.

As the pressure drops, the gravity falling water tank 2
Since the cooling water is poured into the reactor pressure vessel 2 from 6 by the gravity difference, the flooding of the core 1 is maintained.

Even after this water injection, the condenser 80
Operation continues, the condensed water is gravity falling water tank 2
6 is continuously injected into the container through the check valve 29,
Cool the core.

In the condenser cooling pool 81, the water in the condenser cooling pool 81 is heated by the latent heat of condensation transmitted from the heat transfer tube of the condenser 80, and the water temperature rises due to natural convection.

As this temperature rises, evaporation occurs from the surface of the water in the condenser cooling pool 81, and steam is generated in the communication pipe 5.
5 and the condenser exhaust pipe 76 to the outside of the reactor building.

Although the water in the condenser cooling pool 81 is reduced by the evaporation of the pool water, a plurality of condenser cooling pools are made to communicate with each other in water by the communication pipe 56 to reduce the rate of decrease of the water level, and there is after the accident. The water level of the pool is maintained so that the heat transfer tube portion of the condenser 80 is not exposed within the time.

According to this embodiment, the flow rate of the non-condensable gas mixed vapor injected into the condenser 80 by the jet pump 52 increases.

As the flow velocity increases, the flow of the non-condensable gas and steam in the heat transfer tube is disturbed and the steam easily comes into contact with the wall surface of the heat transfer tube, so that the efficiency of condensation increases.

Further, when the flow velocity in the pipe increases, the heat conductivity of condensation increases, which also increases the efficiency of condensation.

Therefore, the area of the wall surface of the heat transfer tube can be reduced.

The pressure in the reactor pressure vessel 2 and the dry well 3 can be reduced by condensing the vapor in the reactor pressure vessel 2 and the dry well 3.

Since the jet pump 52 is opened in the dry well 3, the pressure of the fluid introduced into the condenser 80 is lower than that in the case where the vapor is introduced from the reactor pressure vessel 2 directly into the condenser 80.

Therefore, the wall pressure of the heat transfer tube can be reduced.

This embodiment can also cope with a severe accident as well as a loss of coolant accident, where the core 1 of the reactor pressure vessel 2 is exposed and melted from the water surface and falls from the inside of the reactor pressure vessel 2.

In this severe accident, hydrogen generated by the reaction of water and zirconium, carbon monoxide generated by the melting of concrete which is a structural material, etc. become hot gas and fill the dry well 3.

Drywell 3 at the beginning of the severe accident
Since the pressure of the wet well 6 is lower than the pressure of the above, the gas is discharged to the wet well 6 via the condenser 80 or the vent pipe 7 by using this pressure difference as a driving force, but soon the pressure of the wet well 6 rises. No gas is emitted.

By the way, in a severe accident, since the core 1 is exposed from the water surface, steam is not generated, and the jet pump 52 using steam as a driving force does not function.

The gas in the dry well 3 is heated from the core melt under the dry well 3 to form a natural circulation flow in the dry well 3 and the whole is heated.

Then, the melting valve 64, which is set in the space below the dry well 3 and does not melt at the time of the accident of loss of the coolant, and which is preset so as to melt quickly at the time of severe accident, reaches the melting temperature, melts and becomes the open state. .

As a result, the low-temperature gas having a large specific gravity staying in the condenser 80 descends due to gravity, and the pipe 6
Through the melting valve 64 to the lower part of the dry well 3.

The cooled gas is heated from the core melt to rise in the dry well 3 and flow from the suction port 61 of the jet pump 52 in the upper space to the condenser 80 via the suction pipe 90. Inhaled and cooled again.

By opening the melting valve 64 in this manner, the gas heated by the core melt in the lower part of the dry well 3 is transferred to the condenser 80 above the dry well 3.
Since the natural circulation flow path for cooling is formed and the gas is cooled, the soundness of the storage container can be maintained.

Next, another embodiment of the present invention will be described with reference to FIG.

This embodiment differs from the embodiment described with reference to FIG. 1 in that a plurality of jet pumps 52 are installed in parallel.

The operation when the present embodiment is performed is the same as the shutoff valve 5
Until 1 operates, it is the same as the case of the embodiment described with reference to FIG.

When the shutoff valve 51 is opened, the capacity of the jet pump 52 increases because a plurality of jet pumps 52 are installed in parallel.

Therefore, a larger amount of vapor can be discharged from the main vapor pipe 78, and a larger amount of non-condensable gas mixed vapor can be sucked from the dry well 3 and supplied to the condenser 80.

As a result, it is possible to increase the heat radiation amount to a certain limit.

The limit appears when the heat input amount of the steam flowing into the condenser 80 exceeds the condensing capacity of the condenser 80, but at that time, a part of the steam is discharged into the gas discharge pipe 73.
Is released into the water of the pressure suppression pool 5.

This uncondensed vapor condenses by directly contacting water in the pressure suppression pool 5, but raises the water temperature in the pressure suppression pool 5, resulting in the wet well 6
It is not desirable because it will increase the pressure.

From this point of view, the capacity and the radix of the jet pump 52 are determined in balance with the heat dissipation capacity of the condenser 80.

Next, another embodiment of the present invention will be described with reference to FIG.

The present embodiment differs from the embodiment described with reference to FIG. 1 in that a plurality of melting valves 64 installed in the pipe 63 are installed at different heights.

As a result, even if some of the melting valves are shielded from the high temperature gas in the dry well 3 due to the partial flooding or the influence of obstacles, the other melting valves are melted and opened to allow the natural circulation. It becomes possible to secure a flow path.

Still another embodiment of the present invention will be described with reference to FIG.

The present embodiment differs from the embodiment described with reference to FIG. 1 in that the pipe 63 is branched from the condensed water discharge pipe 72.

During a supposed severe accident, the amount of steam generated is small because the core 1 is exposed, but the water partially present in the dry well 3 evaporates when it comes into contact with the naturally circulating high temperature gas, May be water vapor.

If the gas contains water vapor, it is condensed by the condenser 80 and becomes condensed water, which falls from the condensed water discharge pipe 72, but the pipe communicating with the gravity falling water pool 26 is a horizontal pipe. The condensed water flows down through the descending pipe 63 and is poured from the melting valve 64 in the open state to the lower part of the dry well 3.

By this water injection, the core melt in the lower part of the dry well 3 can be cooled, and the steam evaporated there is cooled again by the condenser 80, so that the cooling operation continues.

In general, the condensation heat transfer coefficient is larger than the convection heat transfer coefficient of gas, so that the cooling effect of the reactor containment vessel is larger in this embodiment as compared with the embodiment described with reference to FIG. .

[0092]

As described above, according to the present invention, the non-condensable gas mixture in the condenser is forced by forcibly feeding the non-condensable gas mixed vapor into the condenser in the event of a coolant loss accident, which is an expected event. The steam flow rate increases.

As a result, the flow of the non-condensable gas and steam in the heat transfer tube is disturbed, and the steam is forcibly brought into contact with the wall surface of the heat transfer tube, thereby improving the efficiency of condensation.

Therefore, the heat transfer area can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a reactor containment vessel according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a jet pump 52.

FIG. 3 is a block diagram of a control system of a shutoff valve 51.

FIG. 4 is another block diagram of the control system of the shutoff valve 51.

FIG. 5 is a partial vertical cross-sectional view of a reactor containment vessel according to another embodiment of the present invention.

FIG. 6 is a partial vertical sectional view of a reactor containment vessel according to still another embodiment of the present invention.

FIG. 7 is a partial vertical cross-sectional view of a reactor containment vessel according to still another embodiment of the present invention.

[Explanation of symbols]

1 ... Reactor core, 2 ... Reactor pressure vessel, 3 ... Dry well, 4
... pressure suppression chamber, 5 ... pressure suppression pool, 6 ... wet well, 7 ... vent pipe, 26 ... gravity falling water tank, 27, 6
3 ... Piping, 29 ... Check valve, 51 ... Shutoff valve, 52 ... Jet pump, 55, 56 ... Communication pipe, 60 ... Drive port, 61 ...
Intake port, 62 ... Ejection port, 64 ... Melting valve, 66 ... Diffuser, 67 ... Throat, 70 ... Control rod, 72 ... Condensate discharge pipe, 73 ... Gas discharge pipe, 76 ... Condenser exhaust pipe,
78 ... Main steam pipe, 80 ... Condenser, 81 ... Condenser cooling pool, 83 ... Water level gauge, 84 ... Comparison circuit, 85 ... Low water level reference signal, 86 ... Valve actuator, 87 ... Pressure measuring instrument, 8
8 ... High pressure reference signal, 90 ... Suction pipe.

Claims (8)

[Claims] 1. A sealed dry well for containing a reactor pressure vessel, a pressure suppression chamber for holding water, a condenser installed outside the dry well, and a condenser connected to and discharged from the condenser. A reactor containment vessel having a fluid discharge pipe for guiding the fluid into water in the pressure suppression chamber, comprising fluid supply means for supplying the fluid in the dry well into the condenser when a coolant is lost. Reactor containment vessel. 2. The reactor containment vessel according to claim 1, wherein the fluid supply means is a jet pump that connects the main steam pipe connected to the reactor pressure vessel via a valve and the condenser. 3. The reactor containment vessel according to claim 2, further comprising a control system for opening the valve in response to a coolant loss accident occurrence signal. 4. The reactor containment vessel according to claim 1, wherein a melting valve is installed at a tip end of the fluid discharge pipe, and the pipe is branched from an intermediate portion of the fluid discharge pipe and can communicate with the inside of the dry well. . 5. The reactor containment vessel according to claim 2, wherein a plurality of jet pumps are provided in parallel. 6. The reactor containment vessel according to claim 4, wherein the fluid discharge pipe is a gas discharge pipe for discharging non-condensable gas. 7. The reactor containment vessel according to claim 4, wherein the fluid discharge pipe is a condensed water discharge pipe for discharging condensed water. 8. The reactor containment vessel according to claim 4, wherein a plurality of the melting valves are installed at different heights of the fluid discharge pipes.