JP2010237070A - Leakage water collector, nuclear power plant and leakage monitoring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce risks on the breakdown of a core catcher due to a delay in water injection in case of a core damage accident and those on steam explosion in case of a drop of a molten core. <P>SOLUTION: A nuclear power plant includes a corium holding vessel 62 which is placed below a reactor vessel 1 inside a containment vessel 2 and opens upward, structures such as pedestal walls 14 forming a cooling flow channel 50 extending along outside faces to exit below the rim of the opening of the vessel, feedwater piping 12 for supplying cooling water to the cooling flow channel 50, feedwater valves 8 mounted on the feedwater piping 12, and a drain accumulation lid 5 for covering the opening. The use of the cooling flow channel 50 as a drain waste liquid sump brings the full-time existence of the cooling water in the cooling flow channel 50. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a leakage water collecting apparatus that collects leakage water from a device and a valve provided inside a containment vessel that stores a reactor vessel that houses a reactor core, a nuclear power plant using the leakage water collecting device, and a leakage monitoring method.

  In a boiling water reactor, a dry well floor drain waste liquid sump water amount measuring device is provided as one of monitoring equipment for leakage from a reactor coolant pressure boundary to a containment vessel. The dry well floor drain waste liquid sump water amount measuring device detects a leak by measuring the water level of the dry well floor drain waste liquid sump where the leaked liquid finally collects.

  The dry well floor drain waste sump is provided by digging down the concrete floor surface of the lower dry well and lining the liner. There are two types of dry well floor drain waste sump: dry well low conductivity waste (LCW) sump and dry well high conductivity waste (HCW) sump.

  The LCW sump is connected to each device / valve by drain piping and accumulates the drain water. The HCW sump also collects leaked water from portions where the leak location cannot be specified, such as leaked water from the control rod drive mechanism flange, leaked valve flange, and reactor water coolant. The LCW sump and HCW sump water levels are constantly monitored, and an alarm is displayed when the rate of change of the water level increases.

  In water-cooled reactors, when cooling water is lost due to the stoppage of water supply to the reactor pressure vessel or the breakage of piping connected to the reactor pressure vessel, the reactor water level drops and the core is exposed. Cooling may be insufficient. Assuming such a case, the reactor is automatically shut down in response to a water level lowering signal, and the core is submerged and cooled by injecting coolant through the emergency core cooling system to prevent a core melting accident. It is like that.

  However, although the probability is very low, it may be assumed that the emergency core cooling device does not operate and the water injection device for other cores cannot be used. In such a case, the core is exposed due to a decrease in the reactor water level, and sufficient cooling is not performed, and the fuel rod temperature rises due to decay heat that continues to occur after the reactor shuts down, eventually leading to core melting. It is possible.

  When such a situation progresses, the high-temperature core melt (corium) melts into the lower part of the reactor pressure vessel, and further melts through the reactor pressure vessel lower mirror and falls onto the floor in the containment vessel. If the reaction between the concrete forming the containment floor and corium continues, the containment vessel may be damaged, and radioactive substances in the containment vessel may be released to the outside environment. In order to suppress such a reaction between corium and concrete, a facility called a core catcher has been proposed. This is equipment for receiving corium dropped from the pressure vessel with a heat-resistant material and cooling the corium in combination with water injection means (see, for example, Patent Document 1 and Patent Document 2).

Japanese Patent No. 3150451 JP 2007-232529 A JP 2007-225356 A

  Conventionally, the dry well floor drain waste sump is provided by digging up concrete on the lower dry well floor surface and lining the liner. However, when the core catcher is installed in the lower dry well, it is difficult to install the drain waste liquid sump directly on the floor surface of the dry well. Patent Document 3 discloses a method of providing a drain sump on the upper surface of a core catcher.

  In addition, if cooling water is present inside the core catcher when the corium is dropped, a steam explosion may occur due to the interaction between the high-temperature corium and water. The conventional core catcher has a structure in which cooling water is supplied after the corium falls in order to avoid the risk of steam explosion.

  In the case of an accident that leads to core melting, there is a high possibility that dynamic equipment cannot be used due to factors such as power loss. A gravity drop type water supply method using a melting valve has been proposed so that cooling water can be supplied even in such a case. However, if the operation of the melting valve is delayed or if a predetermined amount of water injection cannot be ensured, the temperature of the core catcher will rise, the cooling channel will be damaged, and corium will come into contact with the concrete on the PCV floor There is a fear.

  Therefore, an object of the present invention is to reduce the risk of damage to the core catcher due to water injection delay at the time of a core damage accident and the risk of steam explosion when the molten core falls.

  In order to achieve the above-mentioned object, the present invention provides a leakage water collecting apparatus for collecting leakage water from a device and a valve provided inside a containment vessel that houses a reactor vessel that houses a reactor core. A corium holding vessel disposed below the reactor vessel and opened upward, and a cooling flow path extending along the outer surface of the corium holding vessel to an outlet at a position lower than an edge of the opening of the corium holding vessel. It has the structure to form, the water supply piping which supplies cooling water to the said cooling flow path, the water supply valve provided in the said water supply piping, and the drain accumulation cover which covers the said opening part, It is characterized by the above-mentioned.

  Further, the present invention relates to a nuclear reactor plant containing a nuclear reactor vessel, a containment vessel for housing the nuclear reactor vessel, and a corium that is disposed below the reactor vessel inside the containment vessel and opens upward. A holding container, a structure that forms a cooling channel extending along the outer surface of the corium holding container to an outlet at a position lower than an edge of the opening of the corium holding container, a drain accumulation lid that covers the opening, It has a water supply pipe which supplies cooling water to the cooling channel, and a water supply valve provided in the water supply pipe.

  Further, the present invention relates to a leakage monitoring method for monitoring leakage of water from a device and a valve provided inside a containment vessel that houses a reactor vessel that houses a reactor core. Leakage water that is disposed below and falls toward the corium holding container opened upward is received by a drain accumulation cover that covers the opening of the corium holding container, and the outlet at a position lower than the edge of the opening of the corium holding container Leading to a cooling channel formed along the outer surface of the corium holding container, and discharging water from the cooling channel when the water level of the cooling channel exceeds a predetermined height. It is characterized by having.

  ADVANTAGE OF THE INVENTION According to this invention, the damage risk of the core catcher by the water injection delay at the time of a core damage accident, and the steam explosion risk at the time of a molten core fall can be reduced.

1 is an elevational sectional view of a reactor containment vessel in a first embodiment of a boiling water nuclear power plant according to the present invention. It is an II-II arrow plane sectional view of FIG. FIG. 3 is a sectional view taken along the line III-III in FIG. 2. FIG. 4 is a sectional view taken along the line IV-IV in FIG. 2. FIG. 5 is a sectional view taken along line VV in FIG. 2. FIG. 6 is a sectional view taken along the line VI-VI in FIG. 2. 1 is a perspective view of the vicinity of a drain accumulation lid in a first embodiment of a boiling water nuclear power plant according to the present invention. It is a plane sectional view near the core catcher in the second embodiment of the boiling water nuclear power plant according to the present invention. It is IX-IX arrow standing sectional drawing of FIG. It is an elevation sectional view near the core catcher in the third embodiment of the boiling water nuclear power plant according to the present invention. It is an elevation sectional view near the core catcher in the containment vessel atmospheric pressure condition assumed at the time of the pressure vessel bottom part failure of the core melting accident in the third embodiment of the boiling water nuclear power plant according to the present invention.

  An embodiment of a leakage water collecting apparatus according to the present invention will be described with reference to the drawings, taking a boiling water nuclear power plant as an example. In addition, the same code | symbol is attached | subjected to the same or similar structure, and the overlapping description is abbreviate | omitted.

[First Embodiment]
FIG. 1 is an elevational sectional view of a reactor containment vessel in a first embodiment of a boiling water nuclear power plant according to the present invention. 2 is a cross-sectional view taken along the line II-II in FIG. 3 is a sectional view taken along the line III-III in FIG. 4 is a sectional view taken along the line IV-IV in FIG. FIG. 5 is a sectional view taken along line VV in FIG. 6 is a sectional view taken along the line VI-VI in FIG. FIG. 7 is a perspective view of the vicinity of the drain accumulation lid in the present embodiment.

  The boiling water nuclear power plant according to the present embodiment has a reactor pressure vessel 1, a containment vessel 2, and a leaked water collecting device. The reactor core 40 is formed inside the reactor pressure vessel 1. The reactor pressure vessel 1 is stored in a containment vessel 2. The leaking water collecting device includes a core catcher 3 and a drain collecting lid 5.

  The containment vessel 2 has a pedestal floor 41 and a cylindrical pedestal wall 14 extending upward from the pedestal floor 41. The reactor pressure vessel 1 is supported by the pedestal wall 14. A region surrounded by the pedestal wall 14 below the reactor pressure vessel 1 is called a dry well region. A maintenance platform 6 for maintaining a control rod drive mechanism for inserting a control rod into the core 40 is provided at the lower part of the reactor pressure vessel 1.

  A pressure suppression pool 42 is formed outside the pedestal wall 14. A vent pipe 15 is embedded in the pedestal wall 14. The vent pipe 15 is a pipe for guiding water vapor to the pressure suppression pool 42 when a large amount of water vapor is released into the dry well 11 in an accident such as a pipe break.

  The core catcher 3 is disposed on the pedestal floor 41 and directly below the reactor pressure vessel 1. The core catcher 3 has a corium holding container 62 opened upward. The corium holding container 62 has, for example, a shape in which a conical bottom portion opened upward and a cylindrical wall are coupled.

  On the outside of the corium holding container 62, a cooling channel 50 for cooling the corium deposited on the corium holding container 62 from the bottom surface is formed along the bottom surface and the side surface. The cooling channel 50 is formed by the pedestal wall 14, the corium holding container 62, and other structures. The outlet of the cooling channel 50 is formed at a position lower than the edge of the opening of the corium holding container 62. The outlet of the cooling flow path 50 is formed in a ring shape along the outer periphery of the corium holding container 62, for example.

  The core catcher 3 also has a water supply pipe 43 that supplies cooling water to the cooling flow path 50. The water supply pipe 43 branches from the vent pipe 15, for example, and extends between the pressure suppression pool 42 and an opening facing downward at the upper part of the outlet of the cooling flow path 50. A water supply valve 8 is provided in the middle of the water supply pipe 43. The water supply valve 8 is a melting valve that operates by detecting, for example, a temperature rise when corium is dropped.

  A heat exchanger 9 immersed in pool water is provided on the upper part of the storage container 2. The heat exchanger 9 is connected to a steam supply pipe 10 opened to the dry well 11 and a condensed water drain pipe 12 connected to the cooling flow path 50.

  The drain accumulation lid 5 covers the opening of the corium holding container 62. The drain accumulating lid 5 is suspended by a support pillar 13 extending downward from the maintenance platform 6 of the control rod drive mechanism, and includes a central portion and a slope toward the peripheral portion lower than the central portion. The drain accumulation lid 5 is a watertight plate such as a metal plate formed in a shape bent along an elliptical short axis, and is supported by a support member 16. The drain accumulation lid 5 is provided with a communication port 24 that passes through the drain accumulation lid 5. The communication port 24 is, for example, a pipe that extends through the drain accumulation lid 5 from an opening that opens at the lower side of the drain accumulation lid 5 to an opening that opens downward at the upper side of the drain accumulation lid 5.

  The corium holding container 62 further includes a heat-resistant weir 17 that extends along the outer edge of the drain accumulation lid 5 to a position higher than the outer edge. The inside of the heat resistant weir 17 is covered with a heat resistant material. The joint between the drain accumulation lid 5 and the heat-resistant weir 17 is sealed so as to be watertight. A drain hole 19 is formed in the heat-resistant weir 17 at a portion facing the lowest position of the outer edge of the drain accumulation lid 5. The heat-resistant weir 17 may be formed integrally with the corium holding container 62 or may be attached to the corium holding container 62.

  A space between the upper end of the heat-resistant weir 17 and the pedestal wall 14 is covered with a ring-shaped porous plate 18. The perforated plate 18 is, for example, grating.

  The leaked water collecting apparatus further includes a drain pipe 20 that guides leaked water from devices and valves provided in the containment vessel 2 to the cooling flow path 50. The drain pipe 20 extends through, for example, the drain sump cover 23 to an opening directed downward at the upper part of the outlet of the cooling channel 50. The drain sump cover 23 is formed in a ring shape along the inner surface of the pedestal wall 14 and is provided on the outlet of the cooling channel 50.

  The leaked water collecting apparatus further includes a water level measuring device 44 and a sump pump 7. The water level measuring device 44 measures the water level of the cooling channel 50. The sump pump 7 cools from the cooling flow path 50 along the cooling water discharge path indicated by H in the figure when the water level of the cooling flow path 50 measured by the water level measuring instrument 44 exceeds a predetermined height. This is a cooling water discharger that discharges water. The cooling water discharged by the sump pump 7 is sent to a waste liquid treatment system (not shown), for example.

  The water supply valve 8 and the sump pump 7 are disposed between the drain sump cover 23 and the porous plate 18.

  Further, the leakage water collecting device includes a thermometer 21 provided in the vicinity of the drain hole 19 for measuring the temperature of the leakage water flowing out from the drain hole 19, and a drain pipe for measuring the temperature of the leakage water discharged from the drain pipe 20. And a thermometer 22 provided in the vicinity of 20 outlets.

  In such a boiling water nuclear power plant, the corium holding vessel 62 is covered with the drain accumulation lid 5 during normal operation. For this reason, the leakage water of the reactor coolant does not accumulate inside the corium holding vessel 62.

  Further, since the drain accumulation lid 5 has a central portion and a slope toward the peripheral portion lower than the central portion, the drain water falling on the drain accumulation lid 5 flows along the slope toward the peripheral portion. Go. Although a heat-resistant weir 17 is provided on the outer edge of the drain accumulation lid 5, a drain hole 19 is formed at the lowest position, so that drain water that has flowed to the periphery of the drain accumulation lid 5 19 flows into the cooling flow path 50 provided on the outside.

  Further, leakage water from each device / valve in the dry well 11 is collected in the cooling flow path 50 through the drain pipe 20. Therefore, leaked water collected by the drain pipe 20 passes through the drain pipe 20, and other leaked water not collected by the drain pipe 20 is collected by the drain collecting lid 5 in the cooling flow path 50. In this way, the cooling channel 50 is filled with sump water during normal operation.

  The water level in the cooling channel 50 is constantly monitored by the water level measuring device 44. When the fluctuation of the water level in the cooling flow path 4 is larger than the specified value, an alarm is displayed in the central control room. Further, when the water level in the cooling flow path 4 exceeds a predetermined value of a predetermined height, the sump pump 7 discharges the sump water in the cooling flow path 50. That is, the cooling channel 50 of the core catcher 3 is used as a drain waste liquid sump during normal operation.

  The operation time and start interval of the sump pump 7 are monitored, and an alarm is displayed in the central control room when the specified value is exceeded. An alarm is also displayed in the central control room when the thermometers 21 and 22 detect a temperature rise exceeding a specified value. By providing the thermometers 21 and 22 in the vicinity of the drain pipe 20 and in the vicinity of the drain hole 19, it is possible to detect a temperature increase due to leaked water with high sensitivity.

  At the time of the core melting accident, the bottom of the reactor pressure vessel 1 is damaged and corium falls onto the drain accumulation lid 5. Even if the corium dropped on the drain accumulation lid 5 moves toward the peripheral portion along the slope, the corium is dammed by the heat-resistant weir 17 and is less likely to flow into the cooling flow path 50. The drain hole 19 provided in the heat-resistant weir 17 has a size large enough to allow drain water to pass through and has a size small enough to solidify the infiltrated corium with the heat capacity of the heat-resistant weir 17. By designing, passage of the corium drain hole 19 can be prevented. The drain accumulation lid 5 is melted and damaged by the heat of corium, and the corium falls into the corium holding container 62 of the core catcher 3.

  The outer surface of the corium holding container 62 is cooled by the sump water filled in the cooling flow path 4, and the structural material of the core catcher 3 does not immediately become high temperature. In addition, the water vapor generated in the cooling flow path 50 as the corium is cooled is condensed in the heat exchanger 9 provided on the upper portion of the dry well 11 and returns to the cooling flow path as cooling water. When the atmosphere temperature rises due to the heat of corium and radiation from the corium is added to open the water supply valve 8, the cooling water in the pressure suppression pool 42 is supplied to the cooling flow path 4. When the cooling water of the volume or more is supplied to the cooling flow path 4, the cooling water overflows into the inside of the corium holding container 62 through the perforated plate 18 and cools the corium from the upper surface.

  By using the cooling channel 50 of the core catcher 3 as the drain waste liquid sump, cooling water is always present in the cooling channel 50, and the risk of damage to the core catcher 3 due to a delay in water injection in the event of core damage is reduced. The Furthermore, since the water level of the cooling flow path 50 is always controlled as a drain waste sump, the probability of corium falling into the water at the time of a core damage accident is suppressed, and the risk of steam explosion at the time of corium falling can be extremely reduced. .

  During the leak test of the containment vessel 2, the atmosphere of the containment vessel 2 is pressurized. At this time, since the drain collection lid 5 is provided with the communication port 24, the atmospheric gas flows from the space portion of the storage container 2 into the corium holding container 62 of the core catcher 3 through the communication port 24. For this reason, even if the inside of the storage container 1 is pressurized during the leakage test of the storage container 2, the pressure of the corium holding container 62 of the core catcher 3 covered with the drain accumulation lid 5 is almost the same as the atmosphere of the storage container 2. It becomes. Therefore, damage to the drain accumulation lid 5 due to the internal / external differential pressure can be suppressed.

  The drain accumulation lid 5 that also serves as the lid of the core catcher 3 is supported by being suspended from the maintenance platform 6 of the control rod drive mechanism. For this reason, there is little possibility of damaging the heat-resistant material laid inside the corium holding container 62 of the core catcher 3. In addition, since the drain accumulation lid 5 has a shape that is bent along the minor axis of the ellipse, the core catcher 3 up to the upper end of the heat-resistant weir 17 is compared with the case where an elliptical flat drain accumulation surface having the same inclination angle is used. The container height can be lowered. For this reason, the quantity of the inside of the storage container 2 can be reduced.

  The porous plate 18 functions as a gantry for installing the sump pump 7 and a working scaffold during normal operation. Further, the porous plate 18 serves as a filter so that foreign matter does not flow into the cooling flow path of the core catcher in the event of a core melting accident.

[Second Embodiment]
FIG. 8 is a plan sectional view of the vicinity of the core catcher in the second embodiment of the boiling water nuclear power plant according to the present invention. 9 is a sectional view taken along the line IX-IX in FIG.

  In the boiling water nuclear power plant of the present embodiment, the cooling flow paths 51 and 52 are divided into two regions by the partition plate 25. Leaked water from the drain pipe 20 flows into one cooling channel 51. Leaked water collected by the drain accumulation lid 5 flows into the other cooling flow path 52. The drain sump cover 23 is provided so as to cover the ring-shaped opening between the pedestal wall 14 and the heat-resistant weir 17, and leakage water other than the leakage water from the drain pipe 20 flows into the cooling channel 51. To prevent.

  In such a boiling water nuclear power plant, leakage detection can be performed by distinguishing leakage water from the drain pipe 20 from other leakage water. That is, it is possible to perform leakage monitoring using a dry well low conductivity waste liquid (LCW) sump and a dry well high conductivity waste liquid (HCW) sump.

[Third Embodiment]
FIG. 10 is an elevational sectional view in the vicinity of the core catcher in the third embodiment of the boiling water nuclear power plant according to the present invention.

  In the present embodiment, the drain accumulation lid 4 is formed of a stretchable film. The drain collecting lid 4 separates the area inside the corium holding container 62 of the core catcher from the atmosphere in the storage container. During normal operation, the pressure P1 in the region inside the corium holding container 62 is maintained higher than the pressure P2 in the atmosphere in the containment vessel. Thereby, at the time of normal operation, the drain accumulation lid 4 is kept in a convex state.

  When the bottom of the pressure vessel is damaged due to a core melting accident, the pressure P2 in the containment vessel rises to about several atmospheres. The pressure P1 in the inner region of the corium holding vessel 62 is reduced or reversed in the internal and external pressure difference from the normal operation under the containment vessel atmosphere pressure condition assumed when the bottom of the pressure vessel in the core melting accident is broken, and the drain accumulation lid 4 The value is such that is depressed.

  FIG. 11 is an elevational sectional view of the vicinity of the core catcher under the containment vessel atmospheric pressure condition assumed when the bottom of the pressure vessel is damaged in the core melting accident in the present embodiment.

  During normal operation, the drain water is accumulated in the cooling flow path 50 by the drain accumulation lid 4 that is convex upward. During the leakage test of the containment vessel 2, the pressure P2 of the containment vessel atmosphere increases. At this time, the way in which the drain accumulation lid 4 swells changes depending on the value of the internal / external differential pressure (ΔP = P1−P2), but the stress applied to the drain accumulation lid 4 does not increase.

  At the time of the core melting accident, the atmospheric pressure in the containment vessel is expected to rise to several atmospheres, and at this time, the drain accumulation lid 4 is in a concave state. Corium dropped from the pressure vessel is accumulated at the center by the drain accumulation lid 4 while the structure of the drain accumulation lid 4 is maintained, and after the drain accumulation lid 4 is melted by the heat of corium, the corium holding vessel 62 is collected. Fall into.

  In such a boiling water nuclear power plant, since a support column and a support material for supporting the drain accumulation lid 4 are unnecessary, the construction becomes easy and the quantity can be reduced. Further, the drain accumulation lid 4 is prevented from being damaged by the differential pressure during the containment vessel leak test. In the event of a core melting accident, corium can be accumulated and then dropped onto the core catcher 3.

[Other embodiments]
The above-described embodiments are merely examples, and the present invention is not limited to these. For example, it can be applied to other types of reactor facilities such as a pressurized water reactor. Moreover, you may implement combining the characteristic of each embodiment.

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Containment vessel, 3 ... Core catcher, 4 ... Drain accumulation lid, 5 ... Drain accumulation lid, 6 ... Maintenance platform, 7 ... Sump pump, 8 ... Water supply valve, 9 ... Heat exchanger DESCRIPTION OF SYMBOLS 10 ... Steam supply piping, 11 ... Dry well, 12 ... Condensate drain piping, 13 ... Support pillar, 14 ... Pedestal wall, 15 ... Vent pipe, 16 ... Support material, 17 ... Heat-resistant weir, 18 ... Perforated plate, 19 DESCRIPTION OF SYMBOLS ... Drain hole, 20 ... Drain piping, 21 ... Thermometer, 22 ... Thermometer, 23 ... Drain sump cover, 24 ... Communication port, 25 ... Partition plate, 40 ... Core, 41 ... Pedestal floor, 42 ... Pressure suppression pool, DESCRIPTION OF SYMBOLS 43 ... Supply pipe, 44 ... Water level measuring device, 50 ... Cooling flow path, 51 ... Cooling flow path, 52 ... Cooling flow path, 62 ... Corium holding container, H ... Cooling water discharge path

Claims (13)

In the leaked water collection device that collects leaked water from the equipment and valves provided inside the containment vessel that stores the reactor vessel that stores the reactor core,
A corium holding vessel that is arranged below the reactor vessel inside the containment vessel and opened upward;
A structure that forms a cooling channel extending along the outer surface of the corium holding container to an outlet at a position lower than an edge of the opening of the corium holding container;
A water supply pipe for supplying cooling water to the cooling flow path;
A water supply valve provided in the water supply pipe;
A drain accumulation lid covering the opening;
A leaking water collecting apparatus characterized by comprising:   The leak water collecting apparatus according to claim 1, wherein the drain accumulation lid includes a central portion and a slope toward a peripheral portion lower than the central portion.   The leakage water collecting apparatus according to claim 2, further comprising a weir provided along the outer edge of the drain accumulation lid and having a drain hole penetrating at a portion facing the peripheral portion.   The leakage water collecting apparatus according to claim 3, further comprising a first thermometer for measuring a temperature of leakage water flowing out of the drain hole.   The drain accumulation lid is formed of a stretchable film, and during normal operation of a nuclear reactor, the space surrounded by the vessel and the drain accumulation lid is set to have a higher pressure than the outside thereof. The leaked water collection device according to any one of claims 1 to 4.   The leak water collecting apparatus according to any one of claims 1 to 5, wherein the drain accumulation lid is suspended by a support column.   The leakage water collecting apparatus according to any one of claims 1 to 6, further comprising a drain pipe for guiding leakage water from devices and valves in the containment vessel to the cooling flow path. .   The leakage water collecting apparatus according to claim 7, wherein the cooling channel is divided into a region for collecting leakage water from the drain pipe and a region for collecting other leakage water.   The leakage water collecting apparatus according to claim 7 or 8, further comprising a second thermometer for measuring a temperature of leakage water discharged from the drain pipe. A water level measuring device for measuring the water level of the cooling channel;
A cooling water discharger for discharging the cooling water from the cooling flow path when the water level of the cooling flow path exceeds a predetermined height;
The leakage water collecting device according to any one of claims 1 to 9, characterized by comprising:   The leak water collecting apparatus according to claim 1, further comprising a perforated plate that covers the outlet. A reactor vessel containing the reactor core;
A containment vessel for housing the reactor vessel;
A corium holding vessel that is arranged below the reactor vessel inside the containment vessel and opened upward;
A structure that forms a cooling channel extending along the outer surface of the corium holding container to an outlet at a position lower than an edge of the opening of the corium holding container;
A drain accumulation lid covering the opening;
A water supply pipe for supplying cooling water to the cooling flow path;
A water supply valve provided in the water supply pipe;
A nuclear power plant characterized by comprising: In a leakage monitoring method for monitoring leakage of water from equipment and valves provided inside a containment vessel that stores a reactor vessel that houses a reactor core,
Leakage water falling toward the corium holding vessel that is disposed below the reactor vessel inside the containment vessel and opens upward is received by a drain accumulation lid that covers the opening of the corium holding vessel, and the corium holding vessel Leading to a cooling flow path formed along the outer surface of the corium holding container to an outlet at a position lower than the edge of the opening of
Discharging water from the cooling channel when the water level of the cooling channel exceeds a predetermined height;
A leakage monitoring method characterized by comprising:

Images