SMR core lower flow optimization system and method

Abstract

An SMR core lower flow optimization system according to one embodiment of the present invention comprises: a reactor vessel which accommodates a core; a plurality of steam generators which are arranged at the upper part of the core inside the reactor vessel and generate steam by heat exchange between cooling water and a reactor coolant circulating inside the reactor vessel; and a lower flow optimization unit which is disposed at the lower portion of the core and optimizes the internal flow of the reactor coolant discharged from the plurality of steam generators, wherein the lower flow optimization unit changes the shape of a flow path control hole through which the reactor coolant moves according to changes in flow conditions of the lower portion of the core according to the changes in the overall flow characteristics when proceeding from an initial high-temperature shutdown state to start-up and finally to full-power normal-state operation.

Description

SMR core bottom flow optimization system and method

[0001] The present invention relates to a system and method for optimizing the flow under the core of an SMR, and more particularly, to a system and method for optimizing the flow under the core of an SMR, which can quickly perform the initial start-up from a high-temperature shutdown state of an SMR by optimizing the internal flow during initial start-up and normal operation, can prevent the formation of thermal stratification of the internal coolant of an SMR, and can perform stable output operation during normal operation.

[0002] The main design concepts and characteristics of SMRs (small modular reactors) under development at home and abroad can be divided into forced circulation and natural circulation types according to the type of coolant circulation.

[0003] In the case of natural circulation type, NuScale, IRIS, CAREM, mPower, and KEPCO E&C's Bandi can be mentioned, and the reactor coolant system can increase its inherent safety by utilizing the natural circulation principle.

[0004] In the case of forced circulation type, large commercial reactors (over 1,000 MW) have flow skirts installed at the bottom of the core to form a flow so that the cooling water flowing into the core is distributed horizontally and evenly, but this is not known for SMR.

[0005] SMRs are typically manufactured very compactly due to considerations such as transportability and manufacturability. Consequently, whether natural circulation or forced circulation (using RCP), SMRs exhibit less smooth internal flow than large commercial reactors. A particularly problematic issue is the limited internal space beneath the SMR, making it difficult to install a flow skirt (as in large commercial reactors, vertical leveling plates are impossible), making flow leveling impossible.

[0006] The present invention has been devised to solve such problems, and the purpose of the present invention is to provide an SMR core bottom flow optimization system and method capable of optimizing the internal flow of coolant rising from the bottom of the core, taking into consideration the compactness, transportability, and manufacturability of the SMR.

[0007] The purpose of the present invention is to provide a system and method for optimizing the flow under the core of an SMR, which can quickly perform an initial start-up from a high-temperature shutdown state of an SMR by optimizing the internal flow of the SMR during initial start-up and normal operation, can prevent the formation of thermal stratification of the internal coolant of the SMR, and can perform stable output operation during normal operation.

[0008] According to one embodiment of the present invention, a system for optimizing the flow of a lower part of an SMR reactor core comprises: a reactor vessel accommodating a reactor core; a plurality of steam generators disposed on an upper portion of the reactor core inside the reactor vessel and configured to heat-exchange a cooling water and a reactor coolant circulating inside the reactor vessel to generate steam; and a lower part flow optimization unit disposed on the lower portion of the core and configured to optimize the internal flow of the reactor coolant discharged from the plurality of steam generators, wherein the lower part flow optimization unit is characterized in that it changes the shape of a flow path control hole through which the reactor coolant moves in accordance with a change in the flow conditions of the lower portion of the core due to a change in the overall flow characteristics when the reactor proceeds from an initial high-temperature shutdown state to a start-up state and finally to a full-power steady-state operation.

[0009] A method for optimizing the flow in the lower part of an SMR reactor core according to one embodiment of the present invention is characterized by including the steps of: a step of a control unit determining the start-up and operation conditions of an SMR reactor; a step of determining a heat distribution or a temperature distribution according to the start-up and operation conditions of the SMR reactor core; a step of rotating at least one of an upper lower flow control plate body or a lower lower flow control plate body among lower flow control plate bodies installed in the lower part of the core and having a flow control hole formed therein so as to respond to a change in a flow path partially affected by the lower part of the core; and a step of adjusting the size and shape of the flow path control hole in the lower part of the core during the initial start-up and power increase of the SMR reactor and during full power operation so as to optimize the flow in the lower part of the SMR reactor core.

[0010] According to an embodiment of the present invention, the system and method for optimizing the flow under the SMR core can optimize the internal flow of the SMR during initial startup and normal operation, thereby enabling the SMR to quickly perform initial startup from a high-temperature shutdown state, prevent the formation of thermal stratification of the internal coolant of the SMR, and perform stable output operation during normal operation.

[0011] Figure 1 is a cross-sectional view of the SMR core lower flow optimization system.

[0012] Figure 2 is an enlarged view of part A of Figure 1;

[0013] Figure 3 is an exploded view of the core lower flow optimization unit;

[0014] Figure 4 is a flowchart illustrating a core lower flow optimization method according to one embodiment of the present invention.

[0015] Hereinafter, embodiments disclosed in this specification will be described in detail with reference to the attached drawings. Regardless of the drawing numbers, identical or similar components will be given the same reference numbers, and redundant descriptions thereof will be omitted. The suffixes "module" and "part" used for components in the following description are assigned or used interchangeably only for the convenience of writing the specification, and do not in themselves have distinct meanings or roles. In addition, when describing the embodiments disclosed in this specification, if it is determined that a specific description of a related known technology may obscure the gist of the embodiments disclosed in this specification, a detailed description thereof will be omitted. In addition, the attached drawings are only intended to facilitate easy understanding of the embodiments disclosed in this specification, and the technical ideas disclosed in this specification are not limited by the attached drawings, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention.

[0016] Terms that include ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely to distinguish one component from another.

[0017] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0018] Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0019] In this application, terms such as “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but should be understood not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0020] Referring to FIGS. 1 to 3, an SMR core bottom flow optimization system according to one embodiment of the present invention is described.

[0021] FIG. 1 is a cross-sectional view of a lower core flow optimization SMR reactor according to one embodiment of the present invention, FIG. 2 is an enlarged view of section A of FIG. 1, and FIG. 3 is an exploded perspective view of a lower core flow optimization unit.

[0022] As shown in FIGS. 1 and 2, the SMR reactor (10) is configured to include a reactor vessel (11), a core (12), a steam generator (13), a reactor coolant pump (14), a pressurizer (15), a core support barrel (17), and a control rod drive device (18).

[0023] The reactor vessel (11) can form the exterior of the SMR reactor (10).

[0024] The reactor vessel (11) may be a pressure vessel made of carbon steel to load nuclear fuel and allow a chain nuclear fission reaction to occur safely.

[0025] The reactor vessel (11) may be composed of an upper vessel body (11a), a lower vessel body (11b), and a reactor head (11c).

[0026] The upper container body (11a) may be formed in a cylindrical shape. The upper container body (11a) may be formed to be open in the vertical direction.

[0027] The upper container body (11a) may have a receiving space for receiving a steam generator (13).

[0028] The lower vessel body (11b) may be formed in a cylindrical shape. The reactor vessel (11) may be formed to have a vertical length longer than its diameter.

[0029] A hemispherical lower head can be mounted on the lower part of the lower container body (11b).

[0030] The reactor head (11c) may be connected to a flange using stud bolts to cover the upper portion of the upper vessel body (11a). A control rod drive device may be mounted on the exterior of the reactor head (11c) for inserting or withdrawing control rods that control the nuclear fission reaction rate.

[0031] The primary system is a system that cools the core (12) by directly transferring heat from the core (12) by circulating the reactor coolant, which is the primary system fluid. The primary system includes a steam generator (13), a reactor coolant pump (14), a pressurizer (15), etc.

[0032] A secondary system is a system that maintains a pressure boundary with the primary system and generates electricity using heat transferred from the primary system. The secondary system is equipped with a turbine and a generator, which generates electricity.

[0033] The core (12) is placed at the bottom of the reactor vessel (11). The core (11) is where nuclear fuel is loaded and may be composed of a nuclear fuel assembly.

[0034] Inside the reactor vessel (11), a core support barrel (17), which is an internal structure that can be separated from each other, can be installed.

[0035] The core support barrel (17) is designed to support the nuclear fuel from below.

[0036] The interior of the reactor vessel (11) is filled with primary system fluid, and heat received from the core (12) is transferred to the secondary system fluid in the steam generator (13).

[0037] A plurality of nozzles are formed to penetrate the reactor vessel (10) in the thickness direction. A steam generator (13) and a reactor coolant pump (14) can be installed in the plurality of nozzles.

[0038] The reactor coolant pump (14) can be installed on top of the steam generator (13).

[0039] The impeller of the reactor coolant pump (14) is connected to the electric motor via a rotating shaft. As the electric motor operates, the impeller rotates to circulate the reactor coolant.

[0040] The steam generator (13) may be located above the core (12). The steam generator (12) may be located higher than the core (12).

[0041] A plurality of steam generators (13) can be arranged spaced apart from each other in the circumferential direction inside the reactor vessel (10).

[0042] The core support barrel (17) and upper guide structures (not shown) such as the shroud and riser can form a circulation path for the reactor coolant inside the reactor vessel (10).

[0043] A circulation path can be formed to move from the core (12) to the steam generator (13) through the core support barrel (17) and the upper guide structure.

[0044] The reactor coolant rises along the circulation path in the core (12) and can flow into the upper part of the steam generator (13).

[0045] According to this configuration, the reactor coolant of the primary system circulates in the order of the core (12), the reactor coolant pump, the steam generator (13), and the core (12), and the heat generated in the core (12) can be transferred to the steam generator (13).

[0046] The lower part of the steam generator (13) is connected to the water supply system through a water supply pipe (13a), and receives water from the water supply system.

[0047] A water supply valve is installed in the water supply pipe (13a), so that the water supply pipe (13a) can be opened and closed.

[0048] The upper part of the steam generator (13) is connected to the turbine system through a steam pipe (13b), and supplies steam generated in the steam generator (13) to the turbine system.

[0049] Likewise, a steam valve is installed in the steam pipe (13b), so that the steam pipe (13b) can be opened and closed.

[0050] In normal operation of an SMR reactor, feedwater is supplied from the feedwater system to the steam generator (13) through the feedwater pipe (13a), and the steam generator (13) generates steam using the heat transferred from the core (12). The steam is supplied to the turbine system through the steam pipe (13b), and the turbine system generates electricity using the supplied steam.

[0051] A lower core flow optimization SMR reactor according to one embodiment of the present invention may further install a lower core flow optimization unit (100) at the lower part of the core (105).

[0052] The above second circulation path extends from the lower part of the steam generator (13) to the lower flow optimization unit (100).

[0053] The reactor coolant can flow down from the steam generator (13) along the second circulation path and into the lower flow optimization unit (100).

[0054] Since the reactor coolant descends directly downward from the steam generator (13), the reactor coolant discharged from the steam generators (13) of different zones (A, B) is not mixed.

[0055] For example, because the reactor coolant descending from the steam generator (13) in section A and the reactor coolant descending from the steam generator (13) in section B do not mix with each other, different parts of the core (12) may be subjected to different thermal influences.

[0056] The lower flow optimization unit (100) can optimize the lower flow for reactor coolant discharged from steam generators (13) in different zones.

[0057] The lower flow optimization unit (100) can be installed to be accommodated inside the lower head (11c).

[0058] As shown in FIG. 3, the lower flow optimization unit (100) comprises a core lower flow forming body (130) formed in a ring shape, a frame (110) coupled to the frame (110) and having an inlet (131) into which reactor coolant discharged from the steam generator (13) flows in, a storage body (133) in which reactor coolant flowing in through the inlet (131) is stored, and an outlet (135) formed above the storage body (133) to discharge reactor coolant toward the core (12) above the storage body (133), a lower flow control plate body (150) installed at the outlet (135) of the core lower flow forming body (130) via the frame (110), and a rotation control plate body (150) that controls the rotation of the lower flow control plate body (150). It includes a rotary drive member (170) and a control unit (190) that controls the operation of the rotary drive member (170).

[0059] The above frame (110) may include an upper frame (111) and a lower frame (112) in a ring shape, and an upper lower flow control plate body (151) and a lower lower flow control plate body (153) constituting the lower flow control plate body (150) may be rotatably installed on the upper frame (111) and the lower frame (112), respectively.

[0060] The upper lower flow control plate body (151) and the lower lower flow control plate body (153) are configured as circular plate bodies and can be installed in a balanced manner by overlapping each other vertically.

[0061] The upper lower flow control plate body (151) and the lower lower flow control plate body (153) are installed at the lower part of the core and have flow control holes (151a, 153a) formed therein, respectively, so that the flow can be controlled for the lower part of the core (12).

[0062] The above-mentioned flow control holes (151a, 153a) may be formed to have different sizes in the central region, middle region, and outer region of the upper lower flow control plate body (151) and the lower lower flow control plate body (153).

[0063] For example, the above-described euro adjustment holes (151a, 153a) can be configured to have the smallest diameter in the central region, the largest diameter in the middle region, and an intermediate diameter in the outer region.

[0064] The above control unit (190) uses the rotation driving member (170) installed in one or both of the upper lower flow control plate body (151) and the lower lower flow control plate body (153) to rotate the upper lower flow control plate body (151) in one direction or in the opposite direction relative to the lower lower flow control plate body (153), thereby controlling the size and shape of the deformable flow control hole (155a) formed by overlapping the flow control holes (151a, 153a).

[0065] For example, in the case where the flow control holes (151a, 153a) of the upper lower flow control plate body (151) and the lower lower flow control plate body (153) are configured to coincide with each other, and when at least one of the upper lower flow control plate body (151) and the lower lower flow control plate body (153) is rotated so that the flow control holes (151a, 153a) are misaligned with each other, they can have different sizes and shapes so as to be adjusted to optimize the flow in the lower part of the core.

[0066] The above control unit (190) can be linked with a database (191) that stores flow data of the lower part of the core according to the speed, size, and shape of the flow control hole (155a) that is deformed accordingly, and the operating speed and rotation direction of the rotary drive member (170) that optimizes the flow of the lower part of the core with respect to the size and shape of the flow control hole (151a, 153a) of the lower part of the core (12) during initial startup and power increase of the SMR and during full power operation.

[0067] At least two inlets (131) through which the reactor coolant discharged from the steam generator (13) flows in are arranged on the side of the cylindrical storage body (133), and if possible, at least two can be installed at positions symmetrical to each other.

[0068] The reactor coolant introduced through the inlet (131) is mixed in the storage space (133a) of the storage body (133) and flows out to the lower part of the SMR core through the outlet (135). The flow velocity may increase in the part where the flow velocity control holes (151a, 153a) are formed small by the flow velocity control holes (151a, 153a) formed in the lower flow control plate body (150), and the flow velocity may decrease in the part where the flow velocity control holes (151a, 153a) are formed larger, so that the flow velocity can be controlled in the lower part of the core (12).

[0069] When the coolant cooled after heat exchange in the steam generator (13) passes through the core support barrel assembly (SCSB) at the bottom of the SMR core (12) and is collected at the bottom of the reactor and rises to the core (12), the upper lower flow control plate body (151) or the lower lower flow control plate body (153) among the lower flow control plate bodies (150) having the flow control holes (151a, 153a) formed at the bottom of the core (12) can be rotated to adjust the size and shape of the flow control holes (151a, 153a) at the bottom of the core (12) during the initial startup and power increase of the SMR and during full power operation, thereby optimizing the internal flow of the coolant rising from the bottom of the core.

[0070] Referring to FIG. 4, the control unit (190) determines the start-up and operation conditions of the SMR reactor (10) (S10), determines the heat distribution or temperature distribution according to the start-up and operation conditions of the SMR reactor core (12) (S20), and rotates at least one of the upper lower flow control plate body (151) or the lower lower flow control plate body (153) among the lower flow control plate bodies (150) in which the flow control holes (151a, 153a) are formed at the lower portion of the core (12) to respond to changes in the flow path that are partially affected at the lower portion of the core (12) (S30), thereby adjusting the size and shape of the flow control holes (151a, 153a) at the lower portion of the core (12) during the initial start-up and power increase of the SMR and during full power operation.

[0071] That is, according to the SMR core bottom flow optimization system and method according to one embodiment of the present invention, by optimizing the internal flow of the SMR, the internal flow during initial startup and normal operation can be optimized, thereby quickly performing initial startup from a high-temperature shutdown state of the SMR, preventing the formation of thermal stratification of the internal coolant of the SMR, and performing stable output operation during normal operation.

[0072] According to an embodiment of the present invention, the system and method for optimizing the flow under the SMR core can optimize the internal flow of the SMR during initial startup and normal operation, thereby enabling the SMR to quickly perform initial startup from a high-temperature shutdown state, prevent the formation of thermal stratification of the internal coolant of the SMR, and perform stable output operation during normal operation.

Claims

1. Reactor vessel that houses the core; A plurality of steam generators arranged on top of the core inside the reactor vessel and generating steam by heat-exchanging the cooling water and the reactor coolant circulating inside the reactor vessel; and It comprises a lower flow optimization unit disposed at the lower part of the core and optimizing the internal flow of the reactor coolant discharged from the plurality of steam generators. The above-mentioned lower core flow optimization unit is an SMR core lower core flow optimization system that changes the shape of the flow path control hole through which the reactor coolant moves according to the change in the flow conditions of the lower core due to the change in the overall flow characteristics when the reactor proceeds from an initial high-temperature shutdown state to start-up and finally to full-power steady-state operation.

2. In paragraph 1, The lower flow optimization unit includes at least two lower flow control plate bodies having the above flow path control holes formed therein, a rotation driving member for controlling the rotation of the lower flow control plate bodies, and a control unit for controlling the operation of the rotation driving member, wherein the control unit is linked to a database of shapes of flow path control holes through which the reactor coolant moves according to changes in flow conditions of the lower part of the core due to changes in overall flow characteristics when the reactor proceeds from an initial high-temperature shutdown state to a start-up state and finally to a full-power steady-state operation.

3. In paragraph 2, The above lower flow control plate body is an SMR core lower flow optimization system in which a circular upper lower flow control plate body and a lower lower flow control plate body are installed so as to be able to rotate with each other by overlapping each other vertically.

4. In paragraph 3, The upper lower flow control plate body and the lower lower flow control plate body each have a flow control hole formed therein for controlling the flow to the lower part of the core. The above-mentioned Euro control holes are formed in different sizes in the center region, middle region, and outer region, and are an SMR core lower flow optimization system.

5. In paragraph 4, An SMR core bottom flow optimization system, wherein the above-mentioned euro control hole is configured to have the smallest diameter in the center region, the largest diameter in the middle region, and an intermediate diameter in the outer region.

6. In paragraph 4, The above-mentioned rotary driving member is a motor, and is installed on one or both of the upper lower flow control plate body and the lower lower flow control plate body to rotate in one direction or in opposite directions to adjust the size and shape of the deformable flow control hole formed by overlapping the flow control holes. An SMR core lower flow optimization system.

7. The step where the control unit determines the start-up and operating conditions of the SMR reactor. A step for determining the heat distribution or temperature distribution according to the start-up and operating conditions of the above SMR reactor core; A step of rotating at least one of the upper lower flow control plate body or the lower lower flow control plate body among the lower flow control plate bodies installed at the lower part of the core and having a flow control hole formed therein to respond to changes in the flow path partially affected by the lower part of the core; and A method for optimizing the flow at the bottom of an SMR reactor core, comprising the step of adjusting the size and shape of the flow path adjustment hole at the bottom of the core to optimize the flow at the bottom of the SMR reactor core during initial startup and power ramp-up and full power operation.

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