KR19990044931A - Nuclear Reactor Joint Overflow Concept for Power Plants with Low Head Core Instruments - Google Patents

Abstract

A reactor cavity, an in-core-instrument (ICI) vertical chase, an ICI tube connected to the lower end of the reactor vessel and extending through the ICI vertical passage, and between the reactor cavity and the ICI vertical passage A method is provided for flooding a reactor vessel cavity, including a barrier mounted thereon, and a flooding system for use in reactor vessels, the barrier allowing each ICI tube to pass through a barrier plate and In order to minimize leakage, an opening for each ICI tube and a close fitting spherical bearing located within each opening are used. Together with a water supply and a recirculator that sends water from the main source to the reactor cavity, the cooler is provided at a location remote from barrier means that allow the cooled air to pass into the reactor cavity.

Description

Reactor cavity flooding concept for power plants with low head core instruments

The present invention provides a flooding system for use in a reactor vessel cavity including a reactor vessel, an in-core-instrument (ICI) vertical chase, an ICI tube, and a barrier plate. ) And methods thereof.

Related References

This specification claims the rights of US Provisional Application No. 60 / 064,037, filed November 3, 1997.

The existing "System 80" and "System 80+" cavity flooding system design, illustrated in FIG. 1, allows cooling air to flow from the ICI vertical passages up around the vessel and out of the top of the reactor cavity 101. It communicates with each other in an open state between the bottom of the reactor cavity 101 and the ICI vertical passageway 102. In order to support the ICI tube 108 and also to allow the cooling air of the cavity to flow up into the reactor cavity 101 from the ICI vertical passageway, an open network of I beams 109 running between the ICI tubes 108 may be used. It is located below the container 107. The network of I beams 109 is often called a support plate, although the network does not form a plate at all.

The accident prevention approach of the existing system (80/80 +) design is first to provide a guarantee of coolant flow to the core inside the vessel to prevent core melting.

The second accident prevention approach is to provide a means under the container to flood the ICI vertical passageway 102 in a very rare case of design base core melting significantly off the container 107. This is attempted by providing water from the inside containment refueling water storage tank (hereinafter referred to as IRWST) 103 to the ICI vertical passageway 102. The water in the IRWST 103 passes through the IRWST spillway 110 and the holdup flow channel 105 into the retention tank 104. From the retention tank 104, water enters the ICI vertical passage through the reactor cavity waterway 106.

This design problem exists because the volume of the ICI vertical passage is so large that it requires more water than is adequately available to flood the reactor cavity with the combined ICI vertical passage to the level of the vessel above the top of the core. to be.

Accordingly, an object of the present invention is to provide a cavity flooding system that more effectively allows air cooling of the reactor vessel and flooding of the ICI vertical passages, including immersion of at least a portion of the reactor vessel when the core is melted. To provide.

It is a further object of the present invention to modify the presently available cavity flooding system to achieve the above objectives in a simple and relatively low cost manner.

A flooding system for use in a reactor vessel comprising a reactor cavity meets the above requirements, the reactor cavity being connected to the reactor vessel, an ICI vertical passage disposed below the reactor cavity, and to the bottom of the reactor vessel. And barrier means mounted between the ICI tube and the reactor cavity and the ICI vertical passageway extending through the ICI vertical passageway. The barrier means can be a solid plate that can be mounted using a metal plate sandwiched in a sandwiched manner with the peripheral edge of the plate.

The barrier means includes means for allowing each of the ICI tubes to pass through the solid barrier plate, wherein the solid barrier plate includes means for supporting the ICI tube and minimizing leakage. Means for allowing each of the ICI tubes to pass through the barrier means may comprise an opening, the diameter of the opening being approximately equal to the outer diameter of each of the ICI tubes. Means for supporting the ICI tube and minimizing leakage may include a close fitting spherical bearing located within each opening.

Flooding systems are also located far from barrier means, cooling means for passing cooled air to the reactor cavity, means for supplying water from the main source to the reactor cavity, and over barrier means for returning to the reactor cavity. Means for recycling the amount of water that leaks.

The supply means and the recirculation means together a pump, a supply channel for supplying water to the pump from the main source, and an injection channel for supplying water from the pump to fill the space of the reactor vessel cavity surrounding the reactor vessel and located above the solid barrier plate. And a recirculation channel for supplying the amount of water leaking through the solid barrier plate to the injection channel through the pump. The main source from which the feed channel draws water may be IRWST.

The first valve may be arranged in the supply channel. When the water supplied from the main source fills the reactor vessel cavity to a predetermined level, the valve is optionally sealable. The second valve may be arranged in the recirculation channel. When water leaks past the barrier means, the second valve is selectively openable. Optionally a sealable air valve may be disposed in the cooling air duct.

The above and other needs are also met by a method for flooding the reactor vessel cavity, which method comprises an ICI located below the reactor vessel cavity using a barrier plate for the reactor vessel cavity, and thus the reactor vessel. Separating from the vertical passage and passing through the opening of the barrier plate a plurality of ICI tubes connected to the lower end of the reactor vessel and extending through the ICI vertical passage. The method also includes providing spherical bearings, each closely fitting around each ICI tube in each opening, to support the ICI tube and minimize leakage through the openings, and a design base core significantly deviated from the vessel. Sending water from the main source to the reactor vessel cavity for any event, such as melting, and desalting a portion of the reactor vessel with water sent to the reactor vessel cavity. The sending may include pumping up water and the main source may be IRWST. The method also includes recycling water supplied from the ICI vertical passage to the reactor vessel cavity to return to the reactor vessel cavity.

Methods for flooding a reactor vessel cavity include providing an air duct in open communication with the reactor vessel cavity and the ICI tube at a location remote from the barrier plate, and through the air duct prior to core melting. The method may further include cooling the cavity with air.

The method may further comprise selectively stopping the sending of water to the reactor vessel cavity prior to selectively commencing recycling the water to return to the reactor vessel cavity. Both sending and recycling steps can be performed using a single pump. Moreover, the method may include selectively stopping the air cooling of the reactor vessel cavity prior to selectively commencing sending water to the reactor vessel cavity.

Because of the heat released by the reactor vessel during normal operation, the method may include sandwiching the peripheral edge of the barrier plate between the metal mounting plates in a sandwiched manner to allow thermal expansion of the barrier plate.

1 is a schematic diagram illustrating a cavity flooding system currently known in the art.

Figure 2 is a schematic diagram showing a cavity flooding system according to the present invention.

3 is a plan view from above of a solid barrier plate and in-core-instrument (ICI) tube according to the present invention;

4 is an enlarged view of a portion of a solid barrier plate and openings contained therein;

<Explanation of symbols for the main parts of the drawings>

11: reactor cavity 12: reactor vessel

13: ICI vertical passage 14: ICI tube

15: solid barrier plate 16: metal plate

17: opening 18: bearing

19: barrier means 20: duct

21: IRWST 22: Pump

24: feed channel 25: injection channel

26: T 27: Recirculation channel

The overflow system used in the reactor vessel as shown in FIG. 2 satisfies the above requirements. The reactor cavity 11 includes a reactor vessel 12 and is disposed above the ICI vertical passage 13. The ICI tube 14 is connected to the lower end of the reactor vessel 12 and extends through the ICI vertical passage 13. The barrier means 19 is located between the reactor cavity 11 and the ICI vertical passage 13. The barrier means 19 comprise a solid plate 15 rather than an I beam grid present in some existing systems. The plate 15 is shown in its preferred embodiment in FIGS. 3 and 4.

Since the solid plate 15 is near the reactor vessel 12, the plate 15 may be heated to take off during normal operation of the nuclear power plant. In order to allow thermal expansion of the barrier plate 15, the plate can be mounted using a metal plate 16 sandwiching the peripheral edge of the plate 15 in a sandwich manner.

Each ICI tube 14 includes an opening 17 that passes through the barrier plate 15 and extends through the ICI vertical passage 13. In a preferred embodiment, closely fit spherical bearings 18 are located in each opening 17. The bearing 18 supports the ICI tube 14 without damaging the opening 17 while minimizing leakage through the opening 17.

A 60-foot (1 foot = 30.48 cm) hydrostatic head passes through the mounting sheet 16 and ICI tube 14 made of metal sandwiching the periphery of the barrier plate 15 and bearing 18. When placed on the barrier plate 15 described above comprising an opening 17 in this opening 17, only a few gallons per minute (1 gallon = 3.78543 L) of water will leak through the barrier means 19. will be. When a 60 foot head is placed on the barrier plate 15, the reactor vessel 12 can be cooled to a significantly improved state compared to conventional systems because the vessel 12 is exposed to water quickly and directly. have.

The cooled air passes through the air duct 20 to the reactor cavity during normal operation of the nuclear power plant. Since the air duct 20 is provided through the wall adjacent to the ICI vertical passage 13 and the reactor vessel cavity 11, it bypasses the solid plate 15 which functions as part of the barrier means 19.

Water in the IRWST 21 is supplied to the reactor vessel cavity 11 using a pump 22. The IRWST 21 is the main source of water for the vessel cavity 11. Although in the preferred embodiment, the pump 22 is provided in the safety infusion pump chamber 23 under the IRWST 21, the pump 22 may be located in any dry area. This is advantageous because the pump 22 is located at a lower point than all water sources of the system. Thus, water will flow naturally into the vacuum pump 22, and another pump need not be used to counter gravity.

Water is supplied from the IRWST 21 to the pump 22 through the feed channel 24. Pump 22 then pumps water through reactor channel 25 into reactor vessel cavity 11. Water supplied to the vessel cavity 11 partially surrounds the reactor vessel 12 and fills the space of the reactor vessel cavity 11 located above the solid barrier plate 15. The solid barrier plate 15 is strong enough to carry enough water to freshen a portion of the reactor vessel 12. As noted above, a relatively minimal amount of water leaks past the barrier plate 15. In order to dewater a portion of the reactor vessel 12, a sump 26 is provided for collecting the leaked water, and the recirculation channel 27 supplies the water returned through the pump 22 to the inlet channel 27. do.

Valves are provided as part of the overflow system. One valve 28 is disposed in the supply channel 24. When water fills the reactor vessel cavity 11 from the IRWST 21, the valve 28 opens. When the water fills the reactor vessel cavity 11 at a predetermined level, ie when a portion of the reactor vessel 12 is sufficiently fresh, the valve 28 is closed. Another valve 29 is disposed in the recirculation channel 27. When only water is required to be supplied from the IRWST 21 to the container cavity 11, the valve 29 is closed until water also leaks past the barrier plate 15. When water leaks past the barrier means 19 and enters the keg 26 located below the ICI vertical passageway, and when it is required to return the leaked water to the reactor vessel cavity 11, the valve 29 Open.

The air valve 30 is disposed in each cooling air duct. When air is blown through the ICI vertical passage 13, these air valves 30 open. However, once water is directed to the reactor vessel cavity 11 or if water leaks through the cooling air duct 20 into the ICI vertical passage 13, the valve 30 must be closed.

The above requirements and other requirements are also met by retrofitting existing flooding systems, which are connected to the reactor vessel, the ICI vertical passage located below the reactor vessel cavity, and the bottom of the reactor vessel and the ICI vertical It includes a plurality of ICI tubes extending through the passage. In order to achieve this adaptation, the barrier means 19 described above is provided with an ICI tube 14, with spherical bearings 18 closely fitted around each ICI tube 14 in each opening 17. ) And to minimize leakage through the opening 17. 2 shows how the present flooding system is bypassed using the channeled system of the present invention. This further comprises a pump 22 from the IRWST 21. The addition of channels 24, 25, 27 sufficiently avoids the use of the IRWST channel, the retention channel, and the reactor cavity channel in the system shown in FIG.

The air duct 20 must be added to the existing system. The air duct 20 communicates with the reactor vessel cavity 11 and the ICI vertical passage 13 in the open state.

While embodiments of the invention have been described, it should be understood that the invention is not limited to one of the precise embodiments described herein. Various modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (21)

In a flooding system for reactor vessels, A reactor cavity including the reactor vessel, An in-core-instrument (ICI) vertical chase disposed below the reactor cavity, An ICI tube connected to the lower end of the reactor vessel and extending through the ICI vertical passage; A solid barrier plate mounted between said reactor cavity and said ICI vertical passage, Openings for each of the ICI tubes, A close fitting spherical bearing positioned within each of the openings to support the ICI tube and to minimize leakage through the openings; A peripheral edge portion, whereby the solid barrier plate is mounted using a metal plate sandwiched in the peripheral edge portion with the solid barrier plate, One or more cooling air ducts separated from the solid barrier plate and connected to the reactor vessel cavity at a first end and connected to the ICI vertical passage at a second end; A cooling gas blown through the at least one cooling air duct, With pump, A supply channel for supplying water to the pump from a main source, An injection channel for supplying the water from the pump to surround the reactor vessel and to fill the space of the reactor vessel cavity above the solid barrier plate; and And a recirculation channel for supplying the amount of water leaking past the solid barrier plate through the pump to the injection channel. The reactor vessel of claim 1, further comprising a first valve that is selectively sealable when the water supplied from the primary source fills the reactor vessel cavity at a predetermined level and is disposed in the feed channel. Flooding system for use. 2. The overflow system of claim 1 further comprising a second valve selectively openable when water leaks past said solid barrier plate and disposed in said recirculation channel. The system of claim 1 wherein the primary source is an inside-containment refueling water storage tank (IRWST). 10. The system of claim 1, further comprising an optionally sealable air valve disposed in said cooling air duct. 2. The overflow system of claim 1, wherein the pump is located below the primary source and under a sump to collect recycled water. In the overflow type system used for the reactor vessel, A reactor cavity including the reactor vessel, An ICI vertical passage disposed below said reactor cavity, An ICI tube connected to the lower end of the reactor vessel and extending through the ICI vertical passage; Barrier means mounted between the reactor cavity and the ICI vertical passage, the barrier means including means for causing each of the ICI tubes to pass through the barrier means; Cooling means separate from said barrier means, through which cooled air passes into said reactor cavity, Means for supplying water from the primary source to the reactor cavity, and Means for recycling the amount of water leaking past the barrier means to return to the reactor cavity. 8. The system of claim 7, wherein said means for passing said ICI tube through said solid barrier plate comprises means for supporting said ICI tube and minimizing leakage. . 8. The method of claim 7, wherein the supply means and the recirculation means are together With just one pump, A supply channel for supplying water to the pump from a main source, An injection channel for supplying the water from the pump to surround the reactor vessel and to fill the space of the reactor vessel cavity above the solid barrier plate; and And a recirculation channel for supplying the amount of water leaking past the solid barrier plate through the pump to the injection channel. 10. The reactor vessel of claim 9, further comprising a first valve disposed in the feed channel that is selectively sealable when water supplied from the primary source fills the reactor vessel cavity to a predetermined level. Flooding system used. 10. The overflow system of claim 9, further comprising a second valve disposed in said recirculation channel that is selectively openable as water leaks past said barrier means. 10. The overflow system of claim 9, wherein the primary source is an internal containment refueling water storage tank (IRWST). 10. The overflow system of claim 9, further comprising an optionally sealable air valve disposed in the cooling air duct. 10. The overflow system of claim 9, wherein the pump is located below the primary source and under a canister for collecting recycled water. A method for flooding a reactor vessel cavity, Separating the reactor vessel cavity including the reactor vessel from an ICI vertical passage located below the reactor vessel cavity using a barrier plate, Passing through the opening of the barrier plate a plurality of ICI tubes connected to a lower end of the reactor vessel and extending through the ICI vertical passageway; Providing spherical bearings each closely fitted around each ICI tube in each of said openings to support said ICI tubes and minimize leakage through said openings; Sending water from the primary source to the reactor vessel cavity in case of an event, Desalination of a portion of the reactor vessel with the water sent to the reactor vessel cavity; and And recirculating the water supplied to said reactor vessel cavity in said sending step from said ICI vertical passage to return to said reactor vessel cavity. The method of claim 15, Providing an air duct in communication with the reactor vessel cavity portion and the ICI vertical passage open, wherein the air duct is located far from the barrier plate; Prior to said failure, further comprising air cooling said reactor vessel cavity through said air duct. 16. The method of claim 15, wherein said sending comprises pumping up said water and said main source is an internal containment refueling water storage tank (IRWST). The method of claim 15, Selectively stopping the sending step prior to selectively starting the recycling step. The method of claim 15, Selectively stopping said air cooling prior to selectively starting said sending step. 16. The method of claim 15, wherein said sending and recycling are performed using means for pumping up water. The method of claim 15, And allowing thermal expansion of the barrier plate by sandwiching the peripheral edge portion of the barrier plate between metal mounting plates in a sandwiched manner.