JP2006047089A - Reactor container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a rise in ultimate pressure and temperature of reactor container and raise safety by surely cooling core melt in a short time when fall of core melt in a drywell occurs in the situation that failure occurring in core cooling systems in a reactor pressure vessel due to pipe rupture accident and emergency core cooling system and other water injection system for core can not be used. <P>SOLUTION: In the reactor container 1 consisting of a drywell 5 containing the reactor pressure vessel 2, a suppression chamber 6 partitioned with a wall 5a from the drywell 5 and storing pool water 8 and vent pipe 9 for connecting the drywell 5 and the suppression chamber 6, the temperature of wall of the reactor pressure vessel 2 is measured and monitored, a part of a pedestal 5a partitioning the drywell 5 and the suppression chamber 6 is destroyed by a destruction device 16 when an abnormal temperature rise is detected, to let pool water 8 stored in the suppression chamber 6 flow in the drywell 5 and cool the core melt 13. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a nuclear reactor containment vessel that suppresses extreme pressure and temperature rise inside the vessel and maintains safety even when a severe accident occurs in the reactor.

  FIG. 6 shows a sectional view of a conventional reactor containment vessel. The reactor containment vessel 1 is made of a cylindrical reinforced concrete lined with a steel liner (not shown). The reactor pressure vessel 2 is housed in the center, the upper and lower sides are partitioned by a diaphragm floor 3, and the upper part is an upper dry well 4. The lower part is the lower dry well 5.

  The periphery of the lower dry well 5 is constructed on a base 7 as a cylindrical suppression chamber 6 partitioned by a diaphragm floor 3 and a wall 5 a of the lower dry well 5.

  Pool water 8 is stored in the suppression chamber 6. The upper dry well 4, the lower dry well 5, and the suppression chamber 6 are formed at the vent pipe 9 formed at the pedestal 5 a serving as a wall and at the tip thereof. The discharge pipe 10 communicates with the pool water 8.

  In general, in a water-cooled nuclear reactor such as a boiling water nuclear power plant, when a failure occurs in the core cooling system in the reactor pressure vessel 2 due to a piping accident (not shown) or the like, the nuclear reactor is emergency stopped. The safety design is such that the emergency core cooling device immediately and automatically injects cooling water into the reactor, drains the fuel to prevent overheating, and prevents core melting accidents.

  Further, a mixture of high-temperature steam and water is discharged into the upper dry well 4 and the lower dry well 5 from the pipe portion that has been broken up to the function of the emergency core cooling device, and the upper dry well 4 and the lower dry well 5 are discharged. The pressure and temperature inside the well 5 increase.

  Accordingly, a part of the pool water 8 in the vent pipe 9 is pushed through the discharge pipe 10 into the pool water 8 of the suppression chamber 6 due to the pressure inside the dry well that has risen, and then the upper dry well 4 and the lower dry well. 5 is introduced into the pool water 8 through the vent pipe 9 and the discharge pipe 10, and the steam is condensed in the pool water 8.

  Due to this function, the increase in the internal pressure of the containment vessel 1 is suppressed, so that the safety of the containment vessel 1 is maintained, and radioactive substances that may be released from the reactor pressure vessel 2 are contained in the containment vessel. 1 can be appropriately sealed.

  In this way, in a boiling water nuclear power plant, even if a severe accident such as loss of coolant occurs, various emergency core cooling facilities are provided, and the reactor is put into a cold shutdown state. It is designed to be safe so that it can be transitioned and kept safe.

However, although the probability is very low, it can be assumed that the emergency core cooling device does not operate and water injection devices for other cores cannot be used.
In such a case, since the fuel in the core is not cooled by the coolant, it is conceivable that the fuel rod temperature rises due to decay heat generated even after the reactor is shut down, and eventually the core melts.

When this happens, the hot core melt (corium) moves to the lower part of the reactor pressure vessel 2 and falls into the lower plenum.
When this state continues, the temperature of the lower mirror 11 of the reactor pressure vessel 2 rises, and in the worst case, the core melt melts through the lower mirror 11 and falls onto the floor surface of the lower dry well 5. there is a possibility.

  At this time, the molten core melt at a high temperature melts the steel liner of the lower dry well 5 and comes into contact with the concrete on the base 7 to generate heat and chemical reaction, and carbon dioxide, hydrogen and radioactive gas are rapidly generated. To do.

Due to the pressure and temperature of the generated gas, the pressure in the reactor containment vessel 1 is increased, and there is a possibility that the reactor containment vessel 1 may be damaged in a remarkable case.
Moreover, there is a possibility that the floor of the reactor containment vessel 1 is directly eroded and damaged.
Therefore, there is a possibility that radioactive materials are released from the reactor containment vessel 1 to the external environment.

  The erosion reaction of concrete due to the fall of the core melt and the adverse effects associated therewith can be mitigated by injecting water or other coolant appropriately when the core melt falls onto the dry well floor.

  Although a coolant injection device for this core melt drop is usually installed, there is still a possibility that it will not operate as the emergency core cooling device in the reactor pressure vessel as described above.

Therefore, there is a need for a passive cooling device that is inherently unlikely to fail.
Conventionally, as such a passive core melt cooling device, for example, as shown in FIG. 7, a valve 12 made of a fusible metal is provided on a pedestal 5a that partitions a lower dry well 5 and a suppression chamber 6, and this valve 12 is It is considered that the core melt 13 dropped on the floor surface of the lower dry well 5 is melted by the heat, and the pool water 8 in the suppression chamber 6 is poured into the core melt 13 to be cooled. (For example, refer to Patent Document 1).

Further, as shown in FIG. 8, the floor surface of the lower dry well 5 is formed by the metal plate 14, the position thereof is configured to be lower than the water level of the pool water 8, and the suppression chamber 6 is communicated with the lower side of the metal plate 14. It is also considered that the water is cooled by the pool water 8.
With such a configuration, the core melt 13 that has melted and penetrated the lower mirror 11 and dropped onto the floor surface of the lower dry well 5 comes into contact with the metal plate 14 cooled by the pool water 8 and is cooled.

Further, when the core melt 13 melts the floor metal plate 14 of the lower dry well 5 by its heat, the pool is passively caused by the head difference between the floor metal plate 14 of the lower dry well 5 and the pool water 8. Water 8 flows into the lower dry well 5 from the melt-damaged portion, and cools the core melt 13 (see, for example, Patent Document 2).
JP-A-3-152497 (P675, lower left column, line 11 to P676, upper left column, line 20) JP-A-5-341081 ([0016] to [0025])

  However, in the passive core melt cooling apparatus shown in FIG. 7, the fusible metal valve 12 provided on the wall 5 a melts and penetrates the lower mirror 11 of the reactor pressure vessel 2 to form the lower dry well 5. Since it melts and opens with the heat of the core melt 13 dropped on the floor surface, the valve 12 does not melt and water injection cannot be performed unless the core melt 13 reaches the height of the valve 12, at least in the vicinity thereof.

  On the contrary, if the position of the valve 12 is set low, if the melt amount of the core melt 13 is large, the mouth of the valve 12 is blocked by the core melt 13 and water injection into the core melt 13 is prevented. There is a possibility that.

For this reason, there has been a problem that the core melt 13 cannot be cooled reliably and promptly.
On the other hand, in the passive core melt cooling apparatus shown in FIG. 8, since only the floor surface of the lower dry well 5 is formed of the metal plate 14, when the amount of the core melt 13 is large, There is a possibility that the concrete below the inner surface of 5a and the core melt 13 may chemically react to generate various gases.
Further, since the core melt 13 is cooled only by the floor metal plate 14 of the lower dry well 5 cooled by the pool water 8, the cooling efficiency is low.

  For this reason, when the amount of the core melt 13 is large, the metal plate 14 is melted and the pool water 8 that has flowed into the lower dry well 5 and the core melt 13 with high energy that is not sufficiently cooled. And a high pressure is generated due to a severe phenomenon such as a steam explosion, and there is a possibility of damaging the reactor containment vessel 1 if it is remarkable.

  The present invention has been made to solve the above problems, and the core melt is reliably cooled in a short time with pool water at the bottom of the dry well, suppressing an increase in the extreme pressure and temperature of the vessel, and being damaged. The purpose is to obtain a highly safe reactor containment vessel that has been prevented.

  In order to achieve the above object, a reactor containment vessel according to the present invention includes a dry well that houses a reactor pressure vessel, a suppression chamber that is partitioned by the dry well and a wall and stores pool water, and the dry containment vessel. A reactor containment vessel comprising a vent pipe communicating with a well and a suppression chamber, characterized in that a destruction device is provided for breaking the wall and allowing pool water to flow into a dry well when the reactor pressure vessel is abnormal. And

  The reactor containment vessel according to the present invention includes a dry well for storing a reactor pressure vessel, a suppression chamber that is partitioned by the dry well and a wall, communicates under the floor of the dry well, and stores pool water. And a reactor containment vessel comprising a vent pipe communicating the dry well and the suppression chamber, the floor plate metal plate comprising a metal floor plate portion and a side plate portion covering the lower inner surface of the dry well in the dry well. And the floor plate portion of the dry well is supported by a column disposed in the pool water at a position lower than the pool water level in the suppression chamber.

  The reactor containment vessel according to the present invention reliably cools the core melt in a short time with pool water at the bottom of the dry well, suppresses an extreme increase in pressure and temperature of the containment vessel, and damages the containment vessel Can be prevented and safety can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the embodiment, the same parts as those shown in FIG. 6 are denoted by the same reference numerals, and detailed description thereof is omitted.

FIG. 1 is a view showing a reactor containment vessel according to a first embodiment of the present invention. In FIG. 1, a cylindrical suppression chamber 6 has a floor 15 lifted at least partially. A space 5b that extends under the floor of the suppression chamber 6 and communicates with the lower dry well 5 is formed.
A destruction device 16 such as a blasting device for breaking a part of the wall 5a and opening a hole is attached to the pedestal 5a corresponding to the position where the space 5b is formed.

  The position where the destruction device 16 is attached is below the water level of the pool water 8 stored in the suppression chamber 6, and a considerable amount of the pool water 8 passes through the discharge pipe 10 and the vent pipe 9 from the hole vacated by the head difference. It is attached at such a position as to flow into the lower dry well 5.

Next, the operation of the first embodiment of the present invention will be described.
Usually, the temperature of the wall of the pressure vessel 2 is measured and monitored from the viewpoint of safety management.
If an accident such as loss of coolant occurs, the temperature of the wall of the pressure vessel 2 suddenly rises and shows an abnormal value.
When this state continues, in the reactor pressure vessel 2, as shown in FIG. 2, the core melt 13 melts through the lower mirror 11 and falls onto the floor surface of the lower dry well 5.

  However, when an abnormal temperature rise in the wall of the reactor pressure vessel 2 is detected, a blast command is issued to the destruction device 16 attached to the pedestal 5a of the lower dry well 5 to operate it, and a part of the pedestal 5a is blasted. As shown in FIG. 2, the pool water 8 flows into the lower dry well 5 from this explosion location 5 c due to a water head difference.

  The pool water 8 that has flowed into the lower dry well 5 flows into the space 5b that spreads under the floor of the suppression chamber 6 into which the core melt 13 has flowed, and the core melt with a larger amount of water and an increased surface area to be cooled than before. 13 penetrates and cools.

As a result of conventional research, the pool water 8 for cooling the core melt 13 does not penetrate into the core melt 13 at all, and the upper limit of the core melt thickness for cooling the core melt 13 only by heat conduction. Is considered to be about 20cm.
For example, if the entire core material of an improved boiling water reactor with an output of 1.35 million kWe is formed as a core melt, its volume is about 37.8 m ³ .

Accordingly, the floor area of the lower dry well 5 necessary for cooling the core melt 13 is about 189 m ² . The area of about 189 m ² is about 30% considering the cross-sectional area of the containment vessel 1 is about 700 m ² , and can be said to be a feasible value.

  According to the present embodiment, the abnormality of the reactor pressure vessel 2 is detected, the wall 5a of the lower dry well 5 is destroyed by the destruction device, the pool water 8 is poured into the lower dry well 5, and the core melt 13 Since it was made to cool, it can cool reliably in a short time.

  Further, since the space of the lower dry well 5 is expanded under the floor of the suppression chamber 6, the cooling surface area increases, and the core melt 13 can be cooled in a short time with a larger amount of pool water 8.

Next, a second embodiment of the present invention will be described with reference to FIG.
In FIG. 3, reference numeral 17 denotes a floor plate metal plate of the lower dry well 5, and is composed of a floor plate portion 17a and a side plate portion 17b covering the lower inner surface of the wall 5a.

  The floor plate metal plate 17 is formed to be appropriately separated from the base 7 and communicates with the suppression chamber 6 via the discharge pipe 10 between the base 7 and a lower suppression chamber 18 in which pool water 8 is stored. ing.

The floor plate metal plate 17 of the lower dry well 5 is supported by a plurality of columns 19 provided between the floor plate of the lower suppression chamber 18 and separates the lower dry well 5 and the lower suppression chamber 18.
A plurality of fins 20 are attached to the support column 19 in order to improve the cooling performance.

Next, the operation of the second exemplary embodiment of the present invention will be described.
As shown in FIG. 3, when the core melt 13 melts and penetrates the lower mirror 11 of the reactor pressure vessel 2 and falls onto the floor plate portion 17a of the floor plate metal plate 17 of the lower dry well 5, the core melt 13 It is cooled by the floor plate metal plate 17 that has been cooled in advance by the pool water 8 stored in the suppression chamber 18.

At that time, the heat transmitted from the core melt 13 to the floor plate metal plate 17 is transmitted from the support plate 19 and the fins 20 to the pool water 8 in the lower suppression chamber 18 in addition to the floor plate metal plate 17. The cooling performance of the melt 13 can be improved compared to the case where there is simply a metal floor board.
Since the temperature of the core melt 13 is very high, the core melt 13 may be cooled and eroded while melting the floor plate portion 17a of the floor plate metal plate 17 formed of metal.

  However, if the floor plate portion 17a of the floor plate metal plate 17 is melted by the core melt 13 and has a hole, pool water accumulated in the suppression chambers 18 and 6 from the hole 21 as shown in FIG. 8 flows into the lower dry well 5 at a stretch due to a water head difference.

  At this time, since the core melt 13 has already been sufficiently cooled by the floor plate metal plate 17, the support column 19, and the fins 20 and has a low temperature, even if it comes into contact with the pool water 8, it does not suffer from a severe phenomenon such as a steam explosion. Absent.

  Further, since not only the floor surface of the lower dry well 5 but also the lower inner surface of the pedestal 5a is covered with the side plate portion 17b of the metal plate 17 made of metal, the contact between the wall concrete and the core melt 13 is prevented. It can be avoided and the occurrence of chemical reaction can be suppressed.

Next, a third embodiment of the present invention will be described with reference to FIG.
In FIG. 5, a reactor core having a mountain shape (cone or pyramid etc.) is formed on the floor of the lower suppression chamber 18 below the floor surface of the lower dry well 5 so that the apex is arranged toward the floor plate metal plate 17 of the lower dry well 5. A melt guide plate 22 is provided.

  With such a configuration, the core melt 13 that has melted and eroded the floor plate metal plate floor 17 of the lower dry well 5 and dropped into the lower suppression chamber 18 is guided by the chevron-shaped induction plate 22 to form the chevron. It spreads in a shape that spreads across the base.

  As a result, the core melt 13 that has fallen into the lower suppression chamber 18 is not solidified and diffused more widely, so that the area in contact with the pool water 8 in the lower suppression chamber 18 increases, and the core melt 13 is cooled quickly.

1 is a longitudinal sectional view showing a reactor containment vessel according to a first embodiment of the present invention. The longitudinal cross-sectional view which shows the state at the time of core melt fall of the nuclear reactor containment vessel by the 1st Embodiment of this invention. The longitudinal cross-sectional view which shows the nuclear reactor containment vessel by the 2nd Embodiment of this invention. The longitudinal cross-sectional view which shows the state at the time of core melt fall of the nuclear reactor containment vessel by the 2nd Embodiment of this invention. The longitudinal cross-sectional view which shows the nuclear reactor containment vessel by the 3rd Embodiment of this invention. The longitudinal cross-sectional view which shows the conventional general nuclear reactor containment vessel. The longitudinal cross-sectional view which shows an example of the reactor containment vessel provided with the conventional passive type core melt cooling device. The longitudinal cross-sectional view which shows the reactor containment vessel provided with another conventional passive type core melt cooling device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reactor containment vessel, 2 ... Reactor pressure vessel, 3 ... Diaphragm floor, 4 ... Upper dry well, 5 ... Lower dry well, 5a ... Pedestal, 5b ... Space, 5c ... Destruction place, 6 ... Suppression chamber, 7 ... Base, 8 ... Pool water, 9 ... Vent pipe, 10 ... Discharge pipe, 11 ... Lower mirror, 13 ... Core melt, 15 ... Suppression chamber floor, 16 ... Destruction device, 17 ... Floor plate metal plate, 17a ... Floor plate Part, 17b ... side plate part, 18 ... lower suppression chamber, 19 ... strut, 20 ... fin, 21 ... hole, 22 ... guide plate.

Claims (5)

In a reactor containment vessel comprising a dry well for storing a reactor pressure vessel, a suppression chamber partitioned by the dry well and a wall and storing pool water, and a vent pipe communicating with the dry well and the suppression chamber,
A reactor containment vessel provided with a destruction device for breaking the wall and flowing pool water into a dry well when the reactor pressure vessel is abnormal.   The reactor containment vessel according to claim 1, wherein a space extending under the floor of the suppression chamber is provided in at least a part of the dry well below the reactor pressure vessel.   A dry well that stores the reactor pressure vessel, a partition that is partitioned by the dry well and a wall, communicates under the floor of the dry well, and stores a pool water, and a vent that communicates the dry well and the suppression chamber. In a reactor containment vessel comprising a tube, a floor plate metal plate comprising a metal floor plate portion and a side plate portion covering a lower inner surface of the dry well is provided in the dry well, and the floor plate portion of the dry well is disposed in the suppression chamber. A reactor containment vessel supported by a support post disposed in the pool water at a position lower than the pool water level.   The reactor containment vessel according to claim 3, wherein fins are formed on the support columns. 4. A reactor containment vessel according to claim 3, wherein an induction plate of a chevron-shaped core melt is provided on the floor of the suppression chamber below the dry well floor, with the apex facing the dry well floor. .

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