Fast power reduction methods, systems, and pressurized water reactors based on regulating rod assemblies

Abstract

This application provides a method, system, and pressurized water reactor for rapid power reduction based on control rod groups, relating to the field of nuclear reactor technology. This application achieves rapid power reduction by selecting target rod groups for rapid power reduction from gray rod groups and at least some black rod groups within the control rod group according to a target order. The target order is a rod dropping sequence determined based on the insertion order of the gray rod groups and at least some of the black rod groups. This results in minimal disturbance to the reactor core after rod dropping, reducing the impact on the unit's shutdown capability and core power distribution.

Description

Technical Field

[0001] This application relates to the field of nuclear reactor technology, and in particular to a rapid power reduction method, system and pressurized water reactor based on a control rod assembly. Background Technology

[0002] The Rapid Power Reduction System (RPRS) is a critical safety barrier for reactors in response to abnormal operating conditions. Its core function is to rapidly reduce the core power in a controlled manner when the reactor power rises abnormally or requires emergency adjustment, thus preventing the reactor from reaching safety limits.

[0003] Existing fast power reduction systems typically rely on stop rod assemblies to achieve rapid power reduction. However, stop rods are primarily used for performing shutdown functions, and using them in a fast power reduction system weakens the control rods' ability to shut down the reactor. Furthermore, dropping high-value stop rod assemblies into the reactor core has a significant impact on the core power distribution. Summary of the Invention

[0004] In view of this, this application provides a rapid power reduction method, system and pressurized water reactor based on control rods to reduce the impact on unit shutdown capability and core power distribution.

[0005] In a first aspect, this application provides a method for rapid power reduction based on a control rod assembly, comprising:

[0006] Determine whether the current power of the reactor core is greater than the target power;

[0007] In response to the current power being greater than the target power, a target rod group for rapid power reduction is selected from the gray rod group and at least a portion of the black rod group in the regulating rod group according to a target order, wherein the target order is the order in which the rods are dropped based on the insertion order of the gray rod group and the at least a portion of the black rod group;

[0008] The target rod group is controlled to fall into the reactor core.

[0009] In one possible implementation, selecting the target rod group for rapid power reduction from the gray rod group and at least a portion of the black rod group in the regulating rod group according to the target order includes:

[0010] The target order is determined based on the insertion order of the gray bar group and the at least part of the black bar group, and the current running bar position. The i-th bar group in the target order includes the running bar group that is not fully inserted into the core and (i-1) bars inserted after the running bar group in the insertion order, where i is an integer and 1≤i≤(N+1), and N is the total number of bar groups inserted after the running bar group in the insertion order included in the gray bar group and the at least part of the black bar group.

[0011] The target rod group is determined according to the target order.

[0012] In one possible implementation, determining the target rod group according to the target order includes:

[0013] Obtain the falling power after the i-th group of bars falls;

[0014] Determine whether the acquired falling power is greater than the target power;

[0015] In response to the acquisition of a falling power being less than or equal to the target power, the falling bar group corresponding to the one that is closer to the target power among the comparison power and the acquisition of a falling power is determined as the target bar group, wherein the comparison power is the falling power after falling into the j-th bar group, and the j-th bar group is the previous bar group in the target sequence corresponding to the acquisition of the falling power.

[0016] In response to the acquisition of the falling power being greater than the target power, for i≤N, the falling power after falling into the (i+1)th group of rods is acquired, and the step of determining whether the acquired falling power is greater than the target power is returned; for i=(N+1), the (N+1)th group of rods is determined to be the target rod group.

[0017] In one possible implementation, a core online monitoring system is used to perform neutronics calculations to search for the core power after falling into the corresponding rod group, and obtain the corresponding falling power.

[0018] In one possible implementation, the gray rod group includes a first group of power regulating rods, a second group of power regulating rods, a third group of power regulating rods, and a fourth group of power regulating rods for power regulation;

[0019] The at least part of the black rod group includes a fifth power regulating rod group for power regulation, or includes a fifth power regulating rod group and a sixth power regulating rod group for power regulation.

[0020] In one possible implementation, the target power is greater than or equal to 40% of the rated stack power.

[0021] In one possible implementation, after controlling the target rod group to fall into the reactor core, the method further includes:

[0022] The insertion sequence is controlled such that the next rod group of the target rod group is inserted into the core in a target step number, so that the next rod group overlaps with the previous rod group of the next rod group in the insertion sequence.

[0023] In one possible implementation, after the target rod group in the control of the insertion sequence has been inserted into the core a target number of steps, the method further includes:

[0024] In response to the primary power of the reactor where the core is located being greater than the secondary power, the corresponding rod groups from the gray rod group and the at least part of the black rod group are controlled to be inserted into the core according to the insertion order, so that the primary power is matched with the secondary power.

[0025] In response to the primary-side power being less than the secondary-side power, the turbine power on the secondary side is reduced to match the primary-side power with the secondary-side power.

[0026] In one possible implementation, after the primary-side power is matched with the secondary-side power, the method further includes:

[0027] Determine whether the currently inserted rod assembly into the core has exceeded the insertion limit;

[0028] In response to the current insertion limit of the rod assembly in the core, boronizing is initiated to restore the current insertion limit of the rod assembly in the core.

[0029] Secondly, this application provides a fast power reduction system. The fast power reduction system includes:

[0030] Gray bar group;

[0031] Black Stick Group;

[0032] A control unit for performing the rapid power reduction method described in the first aspect.

[0033] Thirdly, this application provides a pressurized water reactor. The pressurized water reactor includes a reactor core, a core online monitoring system, and the fast power reduction system described in the second aspect.

[0034] This application achieves rapid power reduction based on the control rod group by selecting target rod groups from the gray rod group and at least some black rod group in the control rod group according to the target order, wherein the target order is the order of dropping the rods determined based on the insertion order of the gray rod group and at least some black rod group. This results in less disturbance to the reactor core after the rods are dropped, reducing the impact on the unit's shutdown capability and core power distribution. Attached Figure Description

[0035] The accompanying drawings are included to provide a further understanding of this application; they are incorporated into and constitute a part of this application. The drawings illustrate embodiments of this application and, together with this specification, serve to explain the principles of this application. In the drawings:

[0036] Figure 1 This is a schematic diagram of the pressurized water reactor provided in the embodiments of this application;

[0037] Figure 2 This is a schematic flowchart of a rapid power reduction method based on a regulating rod assembly provided in an embodiment of this application;

[0038] Figure 3 This is a flowchart illustrating the method for determining target rod groups based on target order provided in an embodiment of this application;

[0039] Figure 4 This is a schematic diagram showing the relationship between the drop bar assembly and the relative power share after the drop bar is provided in the embodiments of this application. Detailed Implementation

[0040] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this application. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0041] As indicated in this application, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0042] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0043] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0044] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0045] Furthermore, it should be noted that the use of terms such as "first" and "second" to define the objects is merely for the purpose of distinguishing the corresponding objects. Unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application. In addition, although the terminology used in this application is selected from commonly known and used terms, some terms mentioned in this application's specification may have been chosen by the applicant according to his or her judgment, and their detailed meanings are explained in the relevant sections of this description. Moreover, this application should be understood not only through the actual terms used, but also through the meaning implied by each term.

[0046] It should be understood that when a component is referred to as "on another component," "connected to another component," "coupled to another component," or "in contact with another component," it can be directly on, connected to, coupled to, or in contact with that other component, or there may be an intervening component. In contrast, when a component is referred to as "directly on another component," "directly connected to," "directly coupled to," or "directly in contact with" another component, there is no intervening component. Similarly, when a first component is referred to as "electrically contacting" or "electrically coupled to" a second component, there is an electrical path between the first and second components that allows current to flow. This electrical path may include capacitors, coupled inductors, and / or other components that allow current to flow, even if there is no direct contact between the conductive components.

[0047] This application uses flowcharts to illustrate the operations performed by an apparatus or device according to embodiments of this application. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, these steps can be processed in reverse order or simultaneously. Furthermore, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0048] Common reactors include pressurized water reactors, heavy water reactors, and high-temperature gas-cooled reactors. The following section uses a pressurized water reactor as an example to briefly introduce the structure of a reactor. Figure 1 This is a schematic diagram of the structure of an exemplary pressurized water reactor 100 provided in an embodiment of this application. It will be understood that the pressurized water reactor 100 is not required to include... Figure 1 All elements shown in the diagram may also be included in the pressurized water reactor 100. Figure 1 Other elements not shown in the text.

[0049] Please refer to Figure 1The pressurized water reactor 100 is physically isolated from radioactive materials via a primary side 110 and a secondary side 120. The primary side 110 includes components such as the reactor core 1101, a core monitoring system (not shown), control rods 1121, and a pressurizer 1103. The secondary side 120 includes components such as a steam turbine 1201 and a condenser 1202. The reactor core 1101, located within the reactor pressure vessel, is composed of fuel assemblies and serves as the core for nuclear fission heat generation. The insertion / extraction of control rods 1121 adjusts the neutron flux to control the core power. The main pump drives coolant through the hot pipe section to the tube side of the steam generator 101. The pressurizer 1103 maintains pressure to prevent boiling, and the coolant is then returned to the reactor core 1101 through the cold pipe section. The core monitoring system monitors the core power distribution in real time. The secondary side 120 is a non-radioactive steam loop. The feedwater on the shell side of the steam generator 101 absorbs heat and converts it into high-pressure steam, driving the turbine 1201 to rotate and converting thermal energy into mechanical energy to generate electricity. The exhaust steam is condensed into liquid water through the condenser 1202, and then pressurized by the main feedwater pump and sent back to the shell side of the steam generator 101 to complete the cycle. During operation, uranium nuclear fission in the reactor core 1101 generates heat, which is transferred from the primary side 110 to the secondary side 120, where energy conversion is achieved.

[0050] When scenarios such as turbine 1201 shedding load, tripping of one main pump, or tripping of one main feedwater pump occur, requiring rapid power reduction on the primary side 110, the rapid power reduction system 1102 receives a trigger signal, and its control unit 1122 generates a rod dropping signal to control the target rod group for rapid power reduction to fall into the reactor core 1101, so as to quickly reduce the reactor power.

[0051] Existing rapid power reduction systems achieve rapid power reduction by dropping shutdown rod groups during power outages. However, such systems present several problems in actual operation. First, because the control rod values ​​required to reduce power from different power levels to the target power level range vary, different shutdown rod groups need to be set up for rapid power reduction at different operating power levels. Since the unit operates at almost full power, the rapid power reduction rod groups are selected based on full power conditions. If the unit experiences load changes, the previously set rod groups for rapid power reduction may no longer be applicable, requiring on-site operators to reselect shutdown rod groups to perform the rapid power reduction function. This increases operational complexity and may affect system stability. Second, when turbine load shedding occurs, it is only required to rapidly reduce power to a certain power range, such as 15%-50% of rated thermal power (i.e., 15% RTP-50% RTP); while when the main pump trips, it is required to rapidly reduce power to a level close to a certain power level, such as reaching and as close as possible to 50% RTP. Existing fast power reduction systems employ high-value shutdown rod assemblies, which cannot achieve the power control precision required to handle main pump tripping conditions. Third, since the power reduction capability of control rods varies with core burnup, existing fast power reduction systems require power plant engineers to periodically calculate and select suitable fast power reduction rod combinations and integrate them into the power plant control system, increasing workload and the risk of human error. Fourth, shutdown rods are primarily used for shutdown functions; using them in fast power reduction systems weakens the shutdown capability of control rods to some extent. Fifth, the dropping of high-value shutdown rod assemblies into the core has a significant impact on core power distribution.

[0052] This application embodiment selects a target rod group for rapid power reduction from the gray rod group and at least some black rod group in the regulating rod group according to the target order, wherein the target order is the rod dropping order determined based on the insertion order of the gray rod group and at least some black rod group, thereby achieving rapid power reduction based on the regulating rod group. After the rods are dropped, the disturbance to the reactor core is small, reducing the impact on the unit's shutdown capability and reactor core power distribution.

[0053] Figure 2 This is a schematic flowchart of an exemplary rapid power reduction method 200 based on an adjustment rod assembly provided in this application. The rapid power reduction method 200 can be used to reduce power consumption... Figure 1 The rapid power reduction on the primary side of the pressurized water reactor 100 shown is achieved through the rapid power reduction system 1102 of the pressurized water reactor 100. For the purposes of discussion, reference will be made to... Figure 1 A fast power reduction method 200 is described. It should be understood that the fast power reduction method 200 can also be used in other types of reactors, and the fast power reduction method 200 may include additional steps not shown and / or some steps shown may be omitted, and the scope of this application is not limited thereto.

[0054] In step S210, it is determined whether the current power of the reactor core is greater than the target power.

[0055] The core online monitoring system of the pressurized water reactor 100 is used to monitor the power distribution of core 1101 online. The current power of the core can be obtained through the core online monitoring system.

[0056] In step S220, in response to the current power being greater than the target power, a target rod group for rapid power reduction is selected from the gray rod group and at least a portion of the black rod group in the regulating rod group according to the target order, wherein the target order is the order of rod dropping determined based on the insertion order of the gray rod group and at least a portion of the black rod group.

[0057] In some embodiments, the gray rod group includes a first power regulation rod group, a second power regulation rod group, a third power regulation rod group, and a fourth power regulation rod group for power regulation. At least a portion of the black rod group includes a fifth power regulation rod group for power regulation, or includes a fifth power regulation rod group and a sixth power regulation rod group for power regulation. Here, power regulation is functionally equivalent to reactivity regulation and temperature regulation. Taking a 1,000 kW third-generation passive pressurized water reactor nuclear power plant as an example, the reactor core includes 37 control rod bundles. The control rod groups include MA (4 bundles), MB (4 bundles), MC (4 bundles), MD (4 bundles), M1 (4 bundles), M2 (8 bundles), and AO (9 bundles). Among them, the M rod groups (MA, MB, MC, MD, M1, and M2 are collectively referred to as the M rod groups) are mainly used to compensate for reactivity changes caused by changes in operating conditions such as burnup, temperature, and power levels. The AO rod groups are mainly used for controlling the axial power distribution of the reactor core. In the control rod group, MA, MB, MC, and MD are the gray rod group (GRCA), and M1, M2, and AO are the black rod group (RCCA). In this application embodiment, the target rod group for rapid power reduction is selected from MA, MB, MC, MD, and M1, or from MA, MB, MC, MD, M1, and M2, without using the AO rod group specifically for performing axial power distribution control. The following explanation uses the selection of the target rod group from MA, MB, MC, MD, M1, and M2 as an example.

[0058] The M-bar group contains two insertion orders: MA-MB-MC-MD-M1-M2 (sequence 1) and MD-MC-MB-MA-M1-M2 (sequence 2).

[0059] For sequence 1, during runtime, MA is inserted first, followed by MB, MC, MD, M1, and M2 in that order. The order in which the bars are dropped is determined based on this insertion order, i.e., the target order. For example:

[0060] a) If MA is not fully inserted into the core, when the fast power reduction system is triggered, MA (the first group of bars in the target order) will be considered first, followed by MA and MB (the second group of bars in the target order), MA, MB and MC (the third group of bars in the target order), MA, MB, MC and MD (the fourth group of bars in the target order), MA, MB, MC, MD and M1 (the fifth group of bars in the target order), and MA, MB, MC, MD, M1 and M2 (the sixth group of bars in the target order).

[0061] b) If MA is fully inserted into the core but MB is not fully inserted into the core, when the fast power reduction system is triggered, MB (the first group of bars in the target order) will be considered first, followed by MB and MC (the second group of bars in the target order), MB, MC and MD (the third group of bars in the target order), MB, MC, MD and M1 (the fourth group of bars in the target order), and MB, MC, MD, M1 and M2 (the fifth group of bars in the target order).

[0062] c) If MA and MB are fully inserted into the core, but MC is not fully inserted into the core, when the fast power reduction system is triggered, the first consideration is to fall into MC (the first group of bars in the target order), followed by MC and MD (the second group of bars in the target order), MC, MD and M1 (the third group of bars in the target order), and MC, MD, M1 and M2 (the fourth group of bars in the target order).

[0063] d) If MA, MB, and MC are fully inserted into the core, but MD is not fully inserted into the core, when the fast power reduction system is triggered, MD (the first group of bars in the target order) will be considered first, followed by MD and M1 (the second group of bars in the target order), and then MD, M1, and M2 (the third group of bars in the target order).

[0064] e) If MA, MB, MC and MD are fully inserted into the core, but M1 is not fully inserted into the core, when the fast power reduction system is triggered, M1 (the first group of bars in the target order) will be considered first, followed by M1 and M2 (the second group of bars in the target order).

[0065] It should be noted that due to the insertion limit, M1 is not allowed to be fully inserted into the core during operation, so only the above five cases a) to e) exist.

[0066] For sequence 2, the order of dropping the rods is determined in a similar way to sequence 1. Simply replace MA~MD in sequence 1 with MD~MA. This will not be explained in detail here.

[0067] When performing rapid power reduction, the target rod group for rapid power reduction is selected based on the above conditions and the rod insertion order. The embodiment of this application determines the target order based on the insertion order, which is simple and efficient, avoids the complex combinations of a large number of rod groups, makes calculations more convenient, and can determine a unique optimal rod group combination.

[0068] In some embodiments, a function for determining the target rod group for rapid power reduction is added to the core online monitoring system of the pressurized water reactor 100 to achieve automatic calculation and judgment of the target rod group. Specifically, in response to the current core power P0 being greater than the target power Pt, a target order is determined based on the insertion order of the gray rod group and at least some of the black rod groups, as well as the current operating rod position. The i-th rod group in the target order includes the operating rod group that is not currently fully inserted into the core and (i-1) rod groups inserted after the operating rod group in the insertion order, where i is an integer and 1 ≤ i ≤ (N+1), and N is the total number of rod groups inserted after the operating rod group in the insertion order included in the gray rod group and at least some of the black rod groups. Then, the target rod group is determined according to the target order.

[0069] It should be noted that when i=1, the i-th group of bars in the target sequence includes the currently not fully inserted operating bar group and the 0th group of bars inserted after the operating bar group in the insertion sequence. This means that the first group of bars in the target sequence only includes the currently not fully inserted operating bar group, as in case a) above, where the first group of bars in the target sequence includes MA. When i=2, the i-th group of bars in the target sequence includes the currently not fully inserted operating bar group and the 1st group of bars inserted after the operating bar group in the insertion sequence, as in case a) above, where the second group of bars in the target sequence includes MA and MB. And so on, the target sequence corresponding to case a) above includes a total of 6 groups of bars, N=5. Similarly, the target sequence corresponding to case b) above includes a total of 5 groups of bars, N=4.

[0070] In one exemplary embodiment, the core online monitoring system, based on real-time power plant status parameters, including the current power level of core 1101, the current operating position of control rods 1121 of core 1101, and a core monitoring model of the power plant's actual burnup history, calls the core online monitoring system's calculation core according to preset calculation logic to determine the target rod group corresponding to the current core state, and inputs the result to the control unit 1122 of the fast power reduction system 1102. When the fast power reduction system 1102 receives a trigger signal, it completes the rod dropping according to the target rod group's dropping combination, meeting the transient requirements of the unit's fast power reduction. It should be understood that the function of determining the target rod group for fast power reduction can also be implemented through other systems or calculation modules.

[0071] In some embodiments, please refer to Figure 3 The method 300 for determining the target bar group according to the target order includes the following steps.

[0072] In step S310, the falling power after falling into the i-th group of bars is obtained.

[0073] In some embodiments, the core online monitoring system is used to perform neutronics calculations to search for the core power after falling into the corresponding rod group, thus obtaining the corresponding fall-in power. Power search is an existing function of the core online monitoring system and will not be described in detail here.

[0074] In step S320, it is determined whether the obtained falling power is greater than the target power Pt.

[0075] In step S330, in response to the acquired falling power being less than or equal to the target power Pt, the falling rod group corresponding to the one that is closer to the target power Pt between the comparison power Pj and the acquired falling power is determined as the target rod group, wherein the comparison power Pj is the falling power after falling into the j-th group of rods, and the j-th group of rods is the group of rods preceding the falling rod group corresponding to the acquired falling power in the target sequence.

[0076] It should be noted that for i=1, the target order corresponds to the first group of falling rods, which is the group of falling rods with the obtained falling power. There are no rod groups before the first group, so falling into the j-th group does not require falling rods, and the comparison power Pj is the current power P0 of the reactor core. For i=2, the target order corresponds to the second group of falling rods, which is the group of falling rods with the obtained falling power. The j-th group of falling rods is the group preceding the second group, which is the first group, and the comparison power Pj is the falling power P1 after falling into the first group. For i=3, the target order corresponds to the third group of falling rods, which is the group of falling rods with the obtained falling power. The j-th group of falling rods is the group preceding the third group, which is the second group, and the comparison power Pj is the falling power P2 after falling into the first group.

[0077] In some embodiments, the power that is closer to the target power is determined by comparing the magnitude of a first absolute value of the difference between the acquired falling power and the target power with a second absolute value of the difference between the compared power and the target power. Specifically, if the first absolute value is less than the second absolute value, the acquired falling power is closer to the target power, and the falling rod group corresponding to the acquired falling power is determined as the target rod group. For example, in case a) above, when i=1, the first group of rods is the target rod group, and when i=2, the second group of rods is the target rod group. If the first absolute value is greater than or equal to the second absolute value, the compared power is closer to the target power, and the falling rod group corresponding to the compared power is determined as the target rod group. For example, in case a) above, when i=1, no falling rods are needed, and when i=2, the first group of rods is the target rod group.

[0078] In step S340, in response to the obtained falling power being greater than the target power Pt, for i≤N, the falling power after falling into the (i+1)th group of bars is obtained, and the process returns to step S320, which determines whether the obtained falling power is greater than the target power.

[0079] In step S350, in response to the acquired falling power being greater than the target power Pt, for i=(N+1), the (N+1)th group of rods is determined as the target rod group.

[0080] The following uses case a) above as an example to further illustrate the method 300 for determining the target bar group according to the target order.

[0081] Step 1: Obtain the falling power P1 after falling into the first group of bars.

[0082] 1.1 If P1≤Pt, compare the proximity of P0, P1 and Pt: if P0-Pt≤Pt-P1, then no rod needs to be dropped; if P0-Pt>Pt-P1, then the target rod group is determined to be the first group of rods, i.e., MA. Exit the calculation.

[0083] 1.2 If P1>Pt, then proceed to step 2.

[0084] Step 2: Obtain the falling power P2 after the second set of bars falls into the ground.

[0085] 2.1 If P2 ≤ Pt, then compare the proximity of P1, P2, and Pt: if P1 - Pt ≤ Pt - P2, then determine the target bar group as the first group of bars, i.e., MA; if P1 - Pt > Pt - P2, then determine the target bar group as the second group of bars, i.e., MA and MB. Exit the calculation.

[0086] 2.2 If P2 > Pt, then proceed to step 3.

[0087] Step 3: Obtain the falling power P3 after falling into the third group of bars.

[0088] 3.1 If P3 ≤ Pt, then compare the proximity of P2, P3, and Pt: if P2 - Pt ≤ Pt - P3, then the target bar group is determined to be the second group of bars, i.e., MA and MB; if P2 - Pt > Pt - P3, then the target bar group is determined to be the third group of bars, i.e., MA, MB, and MC. Exit the calculation.

[0089] 3.2 If P3 > Pt, then proceed to step 4.

[0090] Step 4: Obtain the falling power P4 after falling into the 4th group of bars.

[0091] 4.1 If P4 ≤ Pt, then compare the proximity of P3, P4, and Pt: if P3 - Pt ≤ Pt - P4, then the target bar group is determined to be the 3rd bar group, i.e., MA, MB, and MC; if P3 - Pt > Pt - P4, then the target bar group is determined to be the 4th bar group, i.e., MA, MB, MC, and MD. Exit the calculation.

[0092] 4.2 If P4 > Pt, then proceed to step 5.

[0093] Step 5: Obtain the falling power P5 after the fifth set of bars falls into the ground.

[0094] 5.1 If P5 ≤ Pt, then compare the proximity of P4, P5, and Pt: if P4 - Pt ≤ Pt - P5, then the target bar group is determined to be the 4th bar group, i.e., MA, MB, MC, and MD; if P4 - Pt > Pt - P5, then the target bar group is determined to be the 5th bar group, i.e., MA, MB, MC, MD, and M1. Exit the calculation.

[0095] 5.2 If P5 > Pt, then proceed to step 6.

[0096] Step 6: Obtain the falling power P6 after falling into the 6th group of bars.

[0097] 6.1 If P6 ≤ Pt, then compare the proximity of P5, P6, and Pt: if P5 - Pt ≤ Pt - P6, then the target bar group is determined to be the 5th bar group, i.e., MA, MB, MC, MD, and M1; if P5 - Pt > Pt - P6, then the target bar group is determined to be the 6th bar group, i.e., MA, MB, MC, MD, M1, and M2. Exit the calculation.

[0098] 6.2 If P6 > Pt, then the target rod group is determined to be the 6th rod group. Exit the calculation.

[0099] The process ends when the judgment condition is met, or when all M-bar groups have fallen into the core. If, for the case where all M-bar groups have fallen into the core, Pn > Pt, then the target bar group is determined to be all M-bar groups.

[0100] This application's embodiments achieve a selected target rod group that ensures the power output after rod insertion is closest to the target power. Assuming the current power is 100% RTP, the current rod position is sequence 1, and the MA is not fully inserted into the core, Figure 4 The power after dropping different combinations of rods is given. According to the method provided in the embodiments of this application, if the target power is 70% RTP, MA, MB, MC, and MD will be selected as the target rod group; if the target power is 30% RTP, MA, MB, MC, MD, and M1 will be selected as the target rod group.

[0101] This application embodiment can match multiple target power steps and, after triggering the fast power reduction system, can quickly and accurately adjust the power to a specified level by dropping rods in a manner closest to the target power. This prevents the power from deviating significantly from the target power after the rods are dropped, avoiding large deviations in both directions (too high or too low), achieving a faster reactive control response, enabling the reactor to quickly reach steady-state equilibrium, and meeting the transient requirements of rapid power reduction. In some embodiments, the target power is greater than or equal to 40% of the rated reactor power (RTP), i.e., the target power ≥ 40% RTP. This embodiment considers the total value of the control rod assembly used for rapid power reduction, further improving the accuracy of the fast power reduction system.

[0102] In step S230, the target rod group is controlled to fall into the reactor core.

[0103] In some embodiments, after step S230, a step of restoring control rod overlap is further included to prepare for restoring the automatic control function of the corresponding rod group (such as rod group M). Specifically, the subsequent rod group of the target rod group in the insertion sequence is controlled to insert into the core a target number of steps, such that the subsequent rod group overlaps with the preceding rod group in the insertion sequence. In an exemplary embodiment, for sequence 1 above, the target rod groups are MA and MB, then MC is controlled to insert into the core until MC is inserted to the position corresponding to normal overlap with MB, and then the insertion of MC is stopped. This is how the overlap step is restored.

[0104] In some embodiments, after the overlap recovery step, a step of balancing the primary-side power and the secondary-side power is further included. Specifically, in response to the primary-side power of the reactor where the core is located being greater than the secondary-side power, the corresponding rod groups in the gray rod group and at least some of the black rod groups are controlled to be inserted into the core according to the insertion order, so that the primary-side power matches the secondary-side power; in response to the primary-side power being less than the secondary-side power, the turbine power on the secondary side is reduced, so that the primary-side power matches the secondary-side power.

[0105] In some embodiments, after the primary-side power and secondary-side power are matched, a step of restoring the insertion limit is further included. Specifically, it is determined whether the currently inserted rod group in the core has exceeded the insertion limit; in response to the currently inserted rod group exceeding the insertion limit, boronizing is initiated to restore the currently inserted rod group to above the insertion limit. For different initial rod positions, the deeper the initial rod position, the greater the possibility of exceeding the insertion limit after rod insertion; the insertion limit is restored by boronizing.

[0106] This application's embodiments determine the target rod group based on the current power level of the reactor core, making it applicable to various operating power levels and thus having wider applicability. This application's embodiments select the target rod group for rapid power reduction from gray and black rod groups, resulting in less core disturbance after rod removal and reducing the impact on unit shutdown capability and core power distribution. Furthermore, the value of a single rod in the gray and black rod groups is relatively small, allowing for more precise control of power after rod removal. Simultaneously, gray and black rod groups are allowed to be inserted into the core during normal operation, while shutdown rod groups must be completely removed from the core during normal operation; therefore, restoring gray and black rod groups after rod removal is faster than restoring shutdown rod groups. In addition, this application's embodiments determine the target rod group through online calculation, replacing manual calculation and setting, simplifying the work, reducing the risk of human error, and eliminating the error problems caused by core burnup in offline periodic calculation methods.

[0107] One embodiment of this application also proposes a fast power reduction system. This fast power reduction system includes a gray bar group, a black bar group, and a control unit, the control unit being used to perform… Figure 2 The rapid power reduction method 200 is shown.

[0108] One embodiment of this application also proposes a pressurized water reactor. The pressurized water reactor includes a reactor core, a core online monitoring system, and the aforementioned rapid power reduction system.

[0109] The basic concepts have been described above. Obviously, for those skilled in the art, the above disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore remain within the spirit and scope of the exemplary embodiments of this application.

[0110] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0111] Similarly, it should be noted that, in order to simplify the description of the present application and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of the embodiments of the present application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this disclosure method does not imply that the subject matter of the present application requires more features than those mentioned. In fact, the embodiments have fewer features than all the features of the single embodiments disclosed above.

[0112] Although this application has been described with reference to specific embodiments, those skilled in the art should recognize that the above embodiments are only used to illustrate this application, and various equivalent changes or substitutions can be made without departing from the spirit of this application. Therefore, any changes or modifications to the above embodiments within the scope of the essential spirit of this application will fall within the scope of this application.

Claims

1. A fast power-down method based on a group of adjustment rods, characterized in that, The method comprises: determining whether a current power of a reactor core is greater than a target power; in response to the current power being greater than the target power, selecting a target rod bank from among gray rod banks and at least partially black rod banks in the rod banks for rapid power reduction according to a target sequence, wherein the target sequence is a drop rod sequence determined based on insertion sequences of the gray rod banks and the at least partially black rod banks; controlling the target rod bank to drop into the reactor core; wherein the selecting the target rod bank from among the gray rod banks and the at least partially black rod banks according to the target sequence comprises: determining the target sequence according to the insertion sequences of the gray rod banks and the at least partially black rod banks and current operating rod positions, wherein an i-th rod bank in the target sequence comprises an operating rod bank that is not fully inserted into the reactor core and (i-1)-th rod banks in the insertion sequences that are inserted after the operating rod bank, i is an integer and 1≤i≤(N+1), N is a total number of rod banks that are inserted after the operating rod bank in the insertion sequences and are included in the gray rod banks and the at least partially black rod banks; determining the target rod bank according to the target sequence; wherein the determining the target rod bank according to the target sequence comprises: obtaining a drop-in power after an i-th rod bank drops in; determining whether the obtained drop-in power is greater than the target power; in response to the obtained drop-in power being less than or equal to the target power, determining a drop-in rod bank corresponding to one of a comparison power and the obtained drop-in power that is closer to the target power as the target rod bank, wherein the comparison power is a drop-in power after a j-th rod bank drops in, the j-th rod bank being a previous rod bank of the drop-in rod bank corresponding to the obtained drop-in power in the target sequence; in response to the obtained drop-in power being greater than the target power, for i≤N, obtaining a drop-in power after an (i+1)-th rod bank drops in, and returning to the step of determining whether the obtained drop-in power is greater than the target power; for i=(N+1), determining the (N+1)-th rod bank as the target rod bank.

2. The fast power-down method of claim 1, wherein, performing a neutronics calculation using a reactor core in-service monitoring system to search for a reactor core power after a corresponding rod bank drops in, to obtain a corresponding drop-in power.

3. The fast power-down method of claim 1, wherein, the gray rod banks comprise a first group of power regulation rod banks, a second group of power regulation rod banks, a third group of power regulation rod banks, and a fourth group of power regulation rod banks; the at least partially black rod banks comprise a fifth group of power regulation rod banks, or comprise a fifth group of power regulation rod banks and a sixth group of power regulation rod banks.

4. The fast power-down method of claim 1, wherein, the target power is greater than or equal to 40% of a rated reactor core power.

5. The fast power-down method of any of claims 1-4, wherein, after the controlling the target rod bank to drop into the reactor core, the method further comprises: controlling a next rod bank of the target rod bank in the insertion sequences to be inserted into the reactor core by a target number of steps, so that the next rod bank establishes an overlap with a previous rod bank of the next rod bank in the insertion sequences.

6. The fast power-down method of claim 5, wherein, after the controlling the next rod bank of the target rod bank in the insertion sequences to be inserted into the reactor core by the target number of steps, the method further comprises: in response to a primary side power of a reactor in which the core is located being greater than a secondary side power, controlling insertion of respective rod banks among the gray rod bank and the at least partial black rod bank into the core according to the insertion sequence, so that the primary side power matches the secondary side power; in response to the primary side power being less than the secondary side power, reducing a turbine power of the secondary side, so that the primary side power matches the secondary side power.

7. The fast power-down method of claim 6, wherein, after the primary side power matches the secondary side power, further comprising: judging whether a rod bank currently inserted into the core breaks an insertion limit; in response to the rod bank currently inserted into the core breaking the insertion limit, initiating boronization to restore the rod bank currently inserted into the core above the insertion limit.

8. A fast power-down system, characterized by comprising: a gray rod bank; a black rod bank; a control unit configured to perform the fast power reduction method of any one of claims 1-7.

9. A pressurized water reactor, characterized by a reactor comprising a core, an in-core monitoring system, and the fast power reduction system of claim 8.

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