WO2025121574A1 - Emergency recirculation valve of small module reactor operating in differential pressure type - Google Patents

Abstract

The present invention relates to a small module reactor capable of increasing operation reliability of an emergency recirculation valve for recirculation of cooling water in an emergency core cooling system, wherein an emergency recirculation valve (240) provided in the emergency core cooling system of the small module reactor including a reactor vessel (210) and a containment vessel (220), comprises: a valve body (241) provided in the reactor vessel (210) and provided with a disk (242) which is opened and closed by a differential pressure between the reactor vessel (210) and the containment vessel (220) to regulate the flow of coolant; a first elastic body (245) which elastically supports the disk (242) in the valve body (241); a stopper member (246) provided in the driving direction of the disk (242) to limit the driving of the disk (242); and a chamber (243) in which a diaphragm (244) connected to the stopper member (246) is accommodated and control pressure is supplied to one space partitioned by the diaphragm (244).

Description

Emergency recirculation valve for small modular reactors operating in differential pressure mode

The present invention relates to a small modular reactor, and more particularly, to an emergency recirculation valve of a small modular reactor (SMR) that operates in a differential pressure type capable of operating in a mechanical environment by excluding measuring equipment from an emergency core cooling system.

Nuclear power generation is a power generation method that can produce large outputs stably and economically. However, it has the disadvantages of being difficult to control output, limited methods of cooling the reactor, high power plant construction costs, and limited locations.

Nuclear technology is being developed in a way that improves safety, economy, and nuclear non-proliferation, and development of SMRs as improved next-generation reactors is expanding.

Small modular reactors refer to small and medium-sized reactors with a smaller capacity (300 MWe or less) than existing nuclear power plants, and collectively refer to various small and medium-sized nuclear power plants such as light water reactors, heavy water reactors, fast reactors, and high-temperature reactors.

The Emergency Core Cooling System (ECCS) of the innovative SMR (i-SMR) currently under development in Korea adopts a method of cooling the reactor core using natural circulation, unlike existing commercial nuclear power plants.

The emergency core cooling system of a small modular reactor includes a reactor vessel in which the core is placed and filled with coolant, and a containment vessel that accommodates the reactor vessel. The reactor vessel is provided with an emergency relief valve for depressurization in the event of a coolant loss accident, and an emergency recirculation valve for recirculating the coolant.

When a Loss of Coolant Accident (LOCA) occurs, an ECCS operation signal is generated, the Emergency Depressurization Valve (EDV) and Emergency Recirculation Valve (ERV) are opened, and the steam and coolant inside the reactor vessel are released into the containment vessel, causing the pressure of the reactor vessel to decrease and the pressure of the containment vessel to increase. Meanwhile, the steam inside the containment vessel is condensed by the passive containment vessel cooling system and accumulates in a liquid state at the bottom of the containment vessel. Afterwards, when the pressure between the reactor vessel and the containment vessel becomes equilibrium and the water level inside the containment vessel becomes higher than that of the reactor vessel, a head difference is generated, causing coolant to flow from the containment vessel into the reactor vessel through the emergency recirculation valve, and the reactor core is cooled by natural circulation.

In such emergency core cooling systems, when the emergency recirculation valve is used as a valve that operates in the existing instrumentation and control environment (e.g., an electrically driven valve), the reliability of the valve operation is reduced due to malfunction of the instrument.

Next, if the emergency pressure relief valve and emergency recirculation valve open simultaneously in the event of a loss of coolant accident, the pressure in the reactor vessel is initially higher than that of the containment vessel, so the reactor coolant is released into the containment vessel through the emergency recirculation valve. At this time, the coolant may flow backwards in the reactor core, possibly causing damage to the nuclear fuel due to denuclearization boiling (DNB).

[Prior art literature]

[Patent Document]

(Patent Document 1) Korean Patent Publication No. 10-2014-0016104 (Publication Date: 2014.02.07)

The present invention is intended to improve the problems of the prior art, and to provide an emergency recirculation valve for a small modular reactor that can prevent malfunction and increase operational reliability by excluding the configuration of electrical components such as measuring instruments in the emergency core cooling system and implementing it in a mechanical manner.

In order to achieve these purposes, the emergency recirculation valve of a small modular reactor according to the present invention is an emergency recirculation valve provided in an emergency core cooling system of a small modular reactor including a reactor vessel and a containment vessel, comprising: a valve body provided with a disk that is provided in the reactor vessel and interrupts the flow of coolant between the reactor vessel and the containment vessel; a chamber provided with a diaphragm connected to the disk and in which the internal pressure of the containment vessel and a control pressure by air pressure are applied through the diaphragm; and an elastic body that elastically supports the diaphragm within the chamber.

Preferably, the elastic body elastically supports the diaphragm so that the disk is opened when the pressure of the reactor vessel acting on the disk and the pressure of the containment vessel acting by the diaphragm within the chamber are in equilibrium.

According to another embodiment of the present invention, an emergency recirculation valve for a small modular reactor is an emergency recirculation valve provided in an emergency core cooling system of a small modular reactor including a reactor vessel and a containment vessel, the valve comprising: a valve body provided in the reactor vessel and having a disk that opens and closes by a differential pressure between the reactor vessel and the containment vessel to cut off a flow of coolant; a first elastic body that elastically supports the disk within the valve body; a stopper member that is provided in a driving direction of the disk to limit driving of the disk; and a chamber in which a diaphragm connected to the stopper member is accommodated and a control pressure is supplied to one side of a space defined by the diaphragm.

Preferably, the first elastic body elastically supports the disk so that the disk can be opened when the pressure of the reactor vessel acting on the disk and the pressure of the containment vessel are in equilibrium, and further preferably, the second elastic body further includes elastically supporting the diaphragm.

More preferably, the second elastic body elastically supports the diaphragm so that the stopper member and the disk are separated during normal operation of the reactor.

Preferably, it includes a pneumatic circuit provided outside the containment vessel to apply control pressure to the chamber.

More preferably, the pneumatic circuit section further includes a first solenoid valve connected to the chamber and provided in a first passage through which a control pressure greater than the internal pressure of the containment vessel is applied to open and close the passage; and a second solenoid valve connected to the chamber and provided in a second passage through which air is discharged to open and close the passage.

More preferably, the first solenoid valve is a fail close type valve, and the second solenoid valve is a fail open type valve.

The emergency relief valve of a small modular reactor of the present invention is an emergency recirculation valve provided in an emergency core cooling system of a small modular reactor including a reactor vessel and a containment vessel, the emergency relief valve comprising: a valve body provided in the reactor vessel and having a disk for cutting off the flow of coolant between the reactor vessel and the containment vessel; a chamber provided with a diaphragm connected to the disk and in which the internal pressure of the containment vessel and a control pressure by air pressure are applied through the diaphragm; and an elastic body for elastically supporting the diaphragm within the chamber, thereby implementing an emergency recirculation valve capable of operating in a mechanical environment by excluding measuring equipment, thereby preventing malfunction of the valve due to measuring equipment and improving reliability.

In addition, in the small modular reactor of the present invention, the emergency recirculation valve is opened at the point in time when the pressure between the reactor vessel and the containment vessel is equalized after the emergency pressure relief valve is operated first when a LOCA occurs, thereby minimizing improper core cooling caused by reverse flow of the reactor coolant.

FIG. 1 is a schematic diagram of a small modular reactor including an emergency recirculation valve according to an embodiment of the present invention.

Figure 2 is a configuration diagram of an emergency recirculation valve of a small modular reactor according to an embodiment of the present invention.

FIG. 3 is a schematic diagram showing the operation of an emergency recirculation valve in the event of an accident in a small modular reactor according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of an emergency recirculation valve of a small modular reactor according to another embodiment of the present invention.

FIG. 5 is a schematic diagram for explaining the operation of an emergency recirculation valve in the event of an accident in a small modular reactor according to another embodiment of the present invention.

The specific structural and functional descriptions presented in the embodiments of the present invention are merely exemplified for the purpose of explaining embodiments according to the concept of the present invention, and the embodiments according to the concept of the present invention may be implemented in various forms. In addition, it should not be construed as being limited to the embodiments described in this specification, but should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

Meanwhile, in the present invention, the terms first and/or second, etc. may be used to describe various components, but the components are not limited to the terms. The terms are used only for the purpose of distinguishing one component from other components, for example, within the scope of the rights according to the concept of the present invention, the first component may be named the second component, and similarly, the second component may also be named the first component.

When it is said that an element is "connected" or "connected" to another element, it should be understood that it may be directly connected or connected to that other element, but that there may be other elements in between. On the other hand, when it is said that an element is "directly connected" or "in direct contact with" another element, it should be understood that there are no other elements in between. Other expressions used to describe the relationship between elements, such as "between" and "directly between" or "adjacent to" and "directly adjacent to", should be interpreted similarly.

The terminology used herein is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. It should be understood that the terms "comprises" or "has" as used herein specify that there is a feature, number, step, operation, component, part, or combination thereof implemented, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, specific embodiments of the present invention will be described with reference to the attached drawings. It should be understood that the sizes of components or the coupling between components may be exaggerated or omitted to aid understanding.

FIG. 1 is a schematic diagram of a small modular reactor including an emergency recirculation valve according to an embodiment of the present invention.

Referring to FIG. 1, a small modular reactor according to an embodiment of the present invention includes a reactor vessel (110) and a containment vessel (120) that accommodates the reactor vessel (110). The reactor vessel (110) is provided with an emergency pressure relief valve (130) for depressurization in the event of a coolant loss accident, and an emergency recirculation valve (140) for recirculating the coolant.

The reactor vessel (110) has a core placed at the bottom center and is filled with cooling water to operate at a pressure above a certain level.

The containment vessel (120) is a steel vessel designed to surround the reactor vessel (110) at a set interval, and the space between the reactor vessel (110) and the containment vessel (120) is vacuum, and in the event of a coolant loss accident, the space between the reactor vessel (110) and the containment vessel (120) is filled with coolant. The containment vessel (120) may have a passive cooling heat exchanger (121) provided on the inner wall, and the passive cooling heat exchanger (121) is connected to an external cooling water storage tank (not shown) to perform heat exchange, so that when an accident occurs, steam released from the reactor vessel (110) to the containment vessel (120) is condensed by the passive cooling heat exchanger (121) to remove heat from the containment vessel (120).

The reactor vessel (120) is provided with an emergency pressure relief valve (130) as a pressure relief system at the top. The emergency pressure relief valve (130) is closed during normal operation of the reactor, and opens in the event of an accident to reduce the pressure of the reactor vessel (120).

The reactor vessel (120) is provided with an emergency recirculation valve (140) at approximately the bottom side, and the emergency recirculation valve (140) induces recirculation of coolant in the event of a coolant loss accident.

Preferably, the emergency recirculation valve (140) includes a valve body (141) provided with a disk (142) that is installed in the reactor vessel (110) and cuts off the flow of coolant between the reactor vessel (110) and the containment vessel (120), a chamber (143) provided with a diaphragm (144) connected to the disk (142) and in which the pressure of the containment vessel (120) and the control pressure by air pressure are applied through the diaphragm (144), and an elastic body (145) that elastically supports the diaphragm (144) within the chamber (143).

Preferably, the apparatus further includes a pneumatic circuit (146)(147) provided outside the containment vessel (120) to apply a control pressure to the chamber (143), and this pneumatic circuit (146)(147) may be provided by a solenoid valve, but is not limited thereto.

Figure 2 is a configuration diagram of an emergency recirculation valve of a small modular reactor according to an embodiment of the present invention.

Specifically, referring to FIG. 2, a valve body (141) is installed in a reactor vessel (110) and has a flow hole (141a) provided therein that connects the space between the reactor vessel (110) and the containment vessel (120), and a disk (142) that opens and closes the flow hole (141a) is provided.

The disk (142) is fixed to the diaphragm (144) by the valve stem (142a), and the diaphragm (144) is elastically supported by an elastic body (145) within the chamber (143) to enable up and down movement.

The chamber (143) is divided into upper and lower spaces by a diaphragm (144), and the upper part of the diaphragm (144) is provided with an elastic body (145) and a first port (143a) that communicates with the internal space of the containment vessel (120), and the lower part is provided with a second port (143b) that connects the pneumatic circuit (146) (147).

The diaphragm (144) moves up and down between the first port (143a) and the second port (143b) within the chamber (143), and a stopper protrusion (143c) may be provided on the inside of the chamber (143) to limit the up and down movement of the diaphragm (144) between the first port (143a) and the second port (143b). In this embodiment, only the stopper protrusion (143c) located at the upper end of the second port (143b) to limit the lower movement range of the diaphragm (144) is exemplified, but a stopper protrusion may also be provided at the lower end of the first port (143a) to limit the upper movement range of the diaphragm (133). Preferably, the diaphragm (144) may be provided with a known sealing member to partition the upper and lower parts of the chamber (143) and seal the upper and lower spaces.

The pneumatic circuit (146)(147) includes a first solenoid valve (146) provided in a first passage (146a) connected to a first port (143b) to supply control pressure, and a second solenoid valve (147) provided in a second passage (147a) connected to the first port (143b) to discharge air.

Preferably, the first solenoid valve (146) is a fail close type valve, and the second solenoid valve (147) is a fail open type valve.

The emergency recirculation valve (140) of the present invention configured as described above is maintained in a closed state during normal operation. For reference, during normal operation, the internal pressure (P _RV ) of the reactor vessel (110) is the highest (~155 bar), the interior of the containment vessel (120) is in a vacuum (or below atmospheric pressure), and the pneumatic circuit (146)(147) is arranged outside the containment vessel (120) and is placed in an atmospheric pressure state. When the internal pressure of the containment vessel (120) is described as P _CV and the atmospheric pressure outside the containment vessel (120) is described as P _AT , the pressure state during normal operation becomes P _RV > P _CV > P _AT .

Meanwhile, the first solenoid valve (146) is used when the emergency recirculation valve (140) is forcibly kept closed due to the need for planned preventive maintenance, etc., and the first solenoid valve (156) is opened and a pressure greater than the internal pressure (P _CV ) of the containment vessel (120) is applied as a control pressure to forcibly keep the emergency recirculation valve (140) closed. At this time, the second solenoid valve (147) is closed.

During normal operation of the reactor, the first solenoid valve (146) is closed, the second solenoid valve (147) is open, and at this time, the diaphragm (144) is maintained in the closed state by the pressure difference between the reactor vessel (110) and the containment vessel (120). Specifically, the pressure acting on the diaphragm (144) during normal operation of the reactor is as shown in the following [Mathematical Formula 1].

[Mathematical formula 1]

A _D is the cross-sectional area of the disk (142), A _d is the cross-sectional area of the diaphragm (144), and F _S is the tension of the elastic body.

FIG. 3 is a schematic diagram showing the operation of an emergency recirculation valve in the event of an accident in a small modular reactor according to an embodiment of the present invention.

Referring to FIG. 3, in the event of an accident such as a loss of coolant accident (LOCA), the coolant leaks outside the reactor vessel (110), causing the internal pressure (P _RV ) of the reactor vessel (110) to decrease and the pressure (P _CV ) of the containment vessel (120) to increase. Thereafter, when the internal pressure (P _RV ) of the reactor vessel (110) decreases below a certain level and the pressure (P _CV ) of the containment vessel (120) increases above a certain level and the condition of the following [Mathematical Formula 2] is satisfied, the emergency recirculation valve (140) is opened.

[Mathematical formula 2]

When the emergency recirculation valve (140) is opened, the cooling water condensed in the containment vessel (120) flows into the reactor vessel (110), thereby cooling the reactor core.

Meanwhile, the opening time of the emergency recirculation valve (140) can be determined by the tension of the elastic body (145).

FIG. 4 is a configuration diagram of an emergency recirculation valve of a small modular reactor according to another embodiment of the present invention.

Referring to FIG. 4, a small modular reactor according to another embodiment of the present invention includes a reactor vessel (210) and a containment vessel (220) for accommodating the reactor vessel (210). The reactor vessel (210) is provided with an emergency pressure relief valve for depressurization in the event of a coolant loss accident and an emergency recirculation valve for recirculating the coolant, which is the same as in the previous embodiment.

The emergency recirculation valve (240) of the present embodiment includes a valve body (241) equipped with a disk (242) that opens and closes by differential pressure to cut off the flow of coolant, a first elastic body (245) that elastically supports the disk (242), a stopper member (246) that can limit the operation of the disk (242), and a chamber (243) in which a diaphragm (244) connected to the stopper member (246) is accommodated and the stopper member (246) is driven by a control pressure applied to the diaphragm (244).

The valve body (241) is provided in the reactor vessel (210) and includes a disk (242) that opens and closes a flow hole by the differential pressure between the reactor vessel (210) and the containment vessel (220) to control the flow of coolant.

The valve body (241) is provided with a disk guide (241a) for guiding the motion of the disk (242) around the euro hole, and further, the disk (242) is provided with an auxiliary disk (242a), and the auxiliary disk (242a) is elastically supported by a first elastic body (245). The valve body (241) may be provided with an auxiliary disk guide (242b) into which the auxiliary disk (242a) and the first elastic body (245) are inserted to guide the motion of the auxiliary disk (242a). The disk guide (241a) or the auxiliary disk guide (242b) may be provided with a stopper projection (not shown) that can limit the upper and lower motion range of the disk (242) or the auxiliary disk (242a).

Preferably, the first elastic body (245) elastically supports the disk (242) so that the disk (242) is opened when the pressure (P _RV ) of the reactor vessel (210) and the pressure (P _CV ) of the containment vessel (220) acting on the disk (242) are in equilibrium.

A stopper member (246) is provided on the same axis as the driving direction of the disk (242) to limit the driving of the disk (242). This stopper member (246) is connected to a diaphragm (244) within the chamber (243) and is operated by a control pressure supplied within the chamber (243).

The chamber (243) is divided into upper and lower parts by a diaphragm (244), and a port (243a) to which a pneumatic circuit (251)(252) is connected is provided at the upper part.

Preferably, the chamber (243) includes a second elastic body (247) that elastically supports the diaphragm (244). The second elastic body (247) supports the diaphragm (244) upwardly so that the stopper member (246) and the disk (242) are kept spaced apart during normal operation of the reactor.

Preferably, the diaphragm (244) may be provided with a known sealing member (not shown) for sealing between the upper space and the lower space by dividing the upper and lower parts of the chamber (243). In particular, in the chamber (243) of the present embodiment, the upper space and the lower space divided by the diaphragm (144) do not come into contact with a high temperature/high pressure fluid (cooling water), so that, unlike the previous embodiment, the sealing member of the diaphragm (244) can prevent a decrease in sealability that may occur due to direct exposure to high temperature/high pressure.

The pneumatic circuit (251)(252) includes a first solenoid valve (251) provided in a first passage (251a) connected to a port (243a) to supply control pressure, and a second solenoid valve (252) provided in a second passage (252a) connected to the port (243a) to discharge air.

Preferably, the first solenoid valve (251) is a fail close type valve, and the second solenoid valve (252) is a fail open type valve.

The emergency recirculation valve (240) of this embodiment configured as described above is kept closed during normal operation, and as described above, during normal operation, the internal pressure (P _RV ) of the reactor vessel (210) is the highest (~155 bar), the interior of the containment vessel (220) is in a vacuum (or below atmospheric pressure), and the pneumatic circuit (251)(252) is arranged outside the containment vessel (120) and is placed in an atmospheric pressure state.

In this embodiment, the first solenoid valve (251) and the second solenoid valve (252) can operate in the same manner as in the previous embodiment. For example, in a case where it is necessary to forcibly maintain the emergency recirculation valve (240) in a closed state, such as during planned preventive maintenance, the first solenoid valve (251) is opened so that high-pressure compressed air is supplied into the chamber (243) as a control pressure, and the stopper member (246) is lowered to press and fix the disk (242), thereby forcibly maintaining the emergency recirculation valve (140) in a closed state. Meanwhile, in this process, the lower space of the diaphragm (244) of the chamber (243) is sealed and compressed, and the second elastic body (247) is also compressed.

FIG. 5 is a schematic diagram for explaining the operation of an emergency recirculation valve in the event of an accident in a small modular reactor according to another embodiment of the present invention.

P_CV)인 경우에 제1탄성체(245)에 의해 디스크(242)가 개방되어 격납용기(220)에서 응축된 냉각수는 원자로 용기(210)로 유입되어 원자로 노심 냉각이 이루어진다.Referring to Fig. 5, in the event of an accident such as a loss of coolant accident (LOCA), the coolant leaks outside the reactor vessel (210), so that the internal pressure (P _RV ) of the reactor vessel (210) decreases and the pressure (P _CV ) of the containment vessel (220) increases. Afterwards, the internal pressure (P _RV ) of the reactor vessel (210) decreases below a certain level and the pressure (P _CV ) of the containment vessel (220) increases above a certain level, so that the internal pressures of the reactor vessel (210) and the containment vessel (220) are in a balanced state (P _RV

In the case of P _CV , the disk (242) is opened by the first elastic body (245) and the cooling water condensed in the containment vessel (220) flows into the reactor vessel (210), thereby cooling the reactor core.

The present invention described above is not limited to the above-described embodiments and the attached drawings, and it will be apparent to a person skilled in the art to which the present invention pertains that various substitutions, modifications, and changes are possible within a scope that does not depart from the technical spirit of the present invention.

[Explanation of symbols]

100: Small modular reactor 110, 210: Reactor vessel

120, 220: Containment vessel 130: Emergency pressure relief valve

140, 240: Emergency recirculation valve 141, 241: Valve body

142, 242 : Disc 143, 243 : Chamber

144, 244 : Diaphragm 145 : Elastic

146, 251: 1st solenoid valve 147, 252: 2nd solenoid valve

245: First elastic body 246: Stopper member

247: Second elastic body

Claims (9)

An emergency recirculation valve provided in an emergency core cooling system of a small modular reactor including a reactor vessel and a containment vessel. A valve body having a disc provided in the reactor vessel to control the flow of coolant between the reactor vessel and the containment vessel; A chamber in which a diaphragm connected to the above disk is provided and in which the internal pressure of the containment vessel and the control pressure by air pressure are applied through the diaphragm; An emergency recirculation valve for a small modular reactor comprising an elastic body elastically supporting the diaphragm within the chamber. An emergency recirculation valve for a small modular reactor, characterized in that in the first paragraph, the elastic body elastically supports the diaphragm so that the disk is opened when the pressure of the reactor vessel acting on the disk and the pressure of the containment vessel acting by the diaphragm within the chamber are in equilibrium. An emergency recirculation valve provided in an emergency core cooling system of a small modular reactor including a reactor vessel and a containment vessel. A valve body having a disc provided in the reactor vessel and opened and closed by the differential pressure between the reactor vessel and the containment vessel to cut off the flow of coolant; A first elastic body that elastically supports the disk within the valve body; A stopper member provided in the driving direction of the above disk to limit the driving of the above disk; An emergency recirculation valve for a small modular reactor, comprising a chamber in which a diaphragm connected to the stopper member is accommodated and a control pressure is supplied to one side space partitioned by the diaphragm. An emergency recirculation valve for a small modular reactor, characterized in that in the third paragraph, the first elastic body elastically supports the disk so that the disk is opened when the pressure of the reactor vessel acting on the disk and the pressure of the containment vessel are in equilibrium. An emergency recirculation valve for a small modular reactor, further comprising a second elastic body that elastically supports the diaphragm in the third paragraph. An emergency recirculation valve for a small modular reactor, characterized in that in the fifth paragraph, the second elastic body elastically supports the diaphragm so that the stopper member and the disk are separated during normal operation of the reactor. An emergency recirculation valve for a small modular reactor, comprising a pneumatic circuit section provided outside the containment vessel and configured to apply control pressure to the chamber, in claim 1 or 3. In the seventh paragraph, the pneumatic circuit part, A first solenoid valve connected to the chamber and provided in a first path to which a control pressure greater than the internal pressure of the containment vessel is applied to open and close the path; An emergency recirculation valve for a small modular reactor, comprising a second solenoid valve connected to the chamber and provided in a second passage through which air is discharged, to open and close the passage. An emergency recirculation valve for a small modular reactor, characterized in that in claim 8, the first solenoid valve is a fail close type valve, and the second solenoid valve is a fail open type valve.

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