Quick power reduction method and system based on adjusting rod group and pressurized water reactor

Abstract

The invention provides a rapid power reduction method and system based on an adjusting rod group and a pressurized water reactor, and relates to the technical field of nuclear reactors. According to the method and the device, the target rod group for rapid power reduction is selected from the grey rod group and the at least part of the black rod group in the adjusting rod group according to the target sequence, and the target sequence is the rod falling sequence determined based on the insertion sequence of the grey rod group and the at least part of the black rod group, so that rapid power reduction based on the adjusting rod group is realized; and the disturbance on the reactor core is small after the rod is dropped, and the influence on the shutdown capacity of a unit and the power distribution of the reactor core is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear reactors, and in particular to a method and system for rapid power reduction based on a regulating rod bank and a pressurized water reactor. BACKGROUND

[0002] A rapid power reduction system (RPRS) is a key barrier for a reactor to respond to abnormal conditions and ensure safety. Its core function is to rapidly reduce the core power in a controllable manner when the reactor power abnormally rises or needs to be urgently adjusted, so as to avoid reaching a safety limit.

[0003] Existing rapid power reduction systems are usually based on shutdown rod banks to achieve rapid power reduction. However, the shutdown rods are mainly used to perform the shutdown function, and to some extent, the use of the shutdown rods in the rapid power reduction system weakens the shutdown capability of the control rods. Moreover, the falling of the high-value shutdown rod bank into the core has a greater impact on the core power distribution. SUMMARY

[0004] Therefore, the present application provides a method and system for rapid power reduction based on a regulating rod bank and a pressurized water reactor, which reduces the impact on the unit shutdown capability and the core power distribution.

[0005] In a first aspect, the present application provides a method for rapid power reduction based on a regulating rod bank, comprising:

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

[0007] in response to the current power being greater than the target power, selecting a target rod bank for rapid power reduction from a gray rod bank and at least part of a black rod bank in the regulating rod bank according to a target order, wherein the target order is a falling rod order determined based on an insertion order of the gray rod bank and the at least part of the black rod bank;

[0008] controlling the target rod bank to fall into the core.

[0009] In a possible implementation manner, the selecting a target rod bank for rapid power reduction from a gray rod bank and at least part of a black rod bank in the regulating rod bank according to a target order comprises:

[0010] determining the target order according to the insertion order of the gray rod bank and the at least part of the black rod bank and a current operating rod position, wherein the i-th rod bank in the target order comprises a rod bank that is not completely inserted into the core in the current operating rod position and (i-1) rod banks inserted after the operating rod bank in the insertion order, i is an integer and 1≤i≤(N+1), and N is the total number of rod banks inserted after the operating rod bank in the insertion order included in the gray rod bank and the at least part of the black rod bank.

[0011] determining the target rod group according to the target sequence.

[0012] In a possible implementation, the determining the target rod group according to the target sequence comprises:

[0013] obtaining the fall-in power after falling into the i-th group of rods;

[0014] determining whether the obtained fall-in power is greater than the target power;

[0015] in response to the obtained fall-in power being less than or equal to the target power, determining the fall-in rod group corresponding to the fall-in power that is closer to the target power from the comparison power and the obtained fall-in power as the target rod group, wherein the comparison power is the fall-in power after falling into the j-th group of rods, and the j-th group of rods is a previous group of rods of the fall-in rod group corresponding to the obtained fall-in power in the target sequence;

[0016] in response to the obtained fall-in power being greater than the target power, obtaining the fall-in power after falling into the (i+1)-th group of rods for i≤N, and returning to the step of determining whether the obtained fall-in power is greater than the target power; and for i=(N+1), determining the (N+1)-th group of rods as the target rod group.

[0017] In a possible implementation, the in-core monitoring system is used to perform a neutron calculation, and search for the in-core power after falling into a corresponding rod group, to obtain a corresponding fall-in power.

[0018] In a possible implementation, the gray rod group comprises a first group of power regulation rods, a second group of power regulation rods, a third group of power regulation rods, and a fourth group of power regulation rods for power regulation.

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

[0020] In a possible implementation, the target power is greater than or equal to 40% of the rated in-core power.

[0021] In a possible implementation, after the controlling the target rod group to fall into the in-core, the method further comprises:

[0022] controlling a next group of rods of the target rod group in the insertion sequence to be inserted into the in-core for a target number of steps, so that the next group of rods overlaps with a previous group of rods of the next group of rods in the insertion sequence.

[0023] In a possible implementation, after the controlling the next group of rods of the target rod group in the insertion sequence to be inserted into the in-core for the target number of steps, the method further comprises:

[0024] in response to the primary side power of the reactor in which the core is located being greater than the secondary side power, controlling insertion of respective rod banks in the gray rod bank and the at least partial black rod bank into the core according to the insertion order, so that the primary side power matches the secondary side power;

[0025] in response to the primary side power being less than the secondary side power, reducing turbine power of the secondary side, so that the primary side power matches the secondary side power.

[0026] In a possible implementation manner, after the primary side power matches the secondary side power, the method further includes:

[0027] judging whether a rod bank currently inserted into the core breaks through an insertion limit;

[0028] in response to the rod bank currently inserted into the core breaking through the insertion limit, starting boronization to restore the rod bank currently inserted into the core to above the insertion limit.

[0029] In a second aspect, the present application provides a fast power reduction system. The fast power reduction system includes:

[0030] a gray rod bank;

[0031] a black rod bank;

[0032] a control unit configured to execute the fast power reduction method in the first aspect.

[0033] In a third aspect, the present application provides a pressurized water reactor. The pressurized water reactor includes a core, an on-line monitoring system of the core, and the fast power reduction system in the second aspect.

[0034] The present application selects target rod banks for fast power reduction from a gray rod bank and at least partial black rod bank in a regulating rod bank according to a target order, where the target order is a drop rod order determined based on an insertion order of the gray rod bank and the at least partial black rod bank, thereby achieving fast power reduction based on the regulating rod bank, and the disturbance to the core after drop rod is small, and the impact on unit shutdown capacity and core power distribution is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0035] The accompanying drawings are included to provide a further understanding of the present application, and are incorporated in and constitute apart of this application, illustrate embodiments of the present application, and together with the description serve to explain the principles of the present application. In the drawings:

[0036] Figure 1 is a structural schematic diagram of a pressurized water reactor provided by an embodiment of the present application;

[0037] Figure 2 is a flowchart of a fast power reduction method based on a regulating rod bank provided by an embodiment of the present application;

[0038] Figure 3 is a flowchart of a method for determining a target stick group according to a target order provided by an embodiment of the present application;

[0039] Figure 4 is a schematic diagram of the relationship between a falling stick stick group and a relative power share after the falling stick. DETAILED DESCRIPTION

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some examples or embodiments of the present application, and for those skilled in the art, the present application can also be applied to other similar scenarios without creative labor. Unless the context clearly indicates otherwise or otherwise stated, the same reference numbers in the drawings represent the same structure or operation.

[0041] As shown in the present application, unless the context clearly indicates otherwise or otherwise stated, "one", "a", "an", and / or "the" do not specifically refer to the singular, but can also include the plural. Generally speaking, the terms "comprise" and "include" only indicate the inclusion of the steps and elements explicitly identified, and these steps and elements do not constitute an exclusive list, and the method or device can also include other steps or elements.

[0042] Unless otherwise specifically stated, the relative arrangement of the components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that the sizes of the various parts shown in the drawings are not drawn in accordance with the actual proportional relationship. The technology, methods and devices known to those skilled in the relevant art can not be discussed in detail, but under appropriate circumstances, the technology, methods and devices should be considered as part of the specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, and not as a limitation. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0043] In the description of the application, it needs to be understood that the orientation words such as "front, back, up, down, left, right", "transverse, vertical, perpendicular, horizontal" and "top, bottom" and the like indicated orientation or position relationship is generally based on the orientation or position relationship shown in the drawings, only for the convenience of describing the application and simplifying the description, without making the opposite statement, these orientation words do not indicate and imply that the device or element referred to must have a particular orientation or be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the scope of protection of the application; the orientation words "inner, outer" refer to the inner and outer relative to the contour of each component.

[0044] For the convenience of description, spatial relative terms such as "over", "above", "upper surface", "upper" and the like can be used herein to describe the spatial positional relationship of one device or feature with other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device described in the drawings. For example, if the device in the drawing is inverted, the device described as "above" or "over" other devices or structures will be positioned "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0045] In addition, it needs to be explained that the use of "first", "second" and the like to limit the object is only for the convenience of distinguishing the corresponding object, and the above words have no special meaning unless otherwise stated, therefore, it cannot be understood as a limitation on the scope of protection of the application. In addition, although the terms used in the application are selected from the known and common terms, some terms mentioned in the specification of the application may be selected by the applicant according to his or her judgment, and the detailed meaning of each term is explained in the relevant part of the description. In addition, the application is required to be understood not only by the actual terms used, but also by the meaning implied by each term.

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

[0047] Flow diagrams have been used herein to illustrate the operation of apparatus or devices in accordance with embodiments of the present application. It will be understood that the operations previously or hereafter are not necessarily performed in the precise order shown. Rather, these steps can be processed in reverse order, or at the same time, or other operations can be added to, or removed from, these processes, or one or more steps can be omitted.

[0048] Currently common reactors include pressurized water reactors, heavy water reactors, high temperature gas cooled reactors, etc. The structure of a reactor will be briefly introduced below using a pressurized water reactor as an example. Figure 1 is a structural schematic diagram of an exemplary pressurized water reactor 100 provided by embodiments of the present application. It will be understood that the pressurized water reactor 100 need not necessarily include all of the elements shown in Figure 1 , and the pressurized water reactor 100 can also include other elements not shown in Figure 1 .

[0049] Reference is made to Figure 1, the pressurized water reactor 100 is physically isolated by the primary side 110 and the secondary side 120 to prevent radioactive diffusion. The primary side 110 includes a core 1101, an in-core monitoring system (not shown), control rods 1121, and a pressurizer 1103. The secondary side 120 includes a turbine 1201 and a condenser 1202. The core 1101 is located in the reactor pressure vessel and is composed of fuel assemblies, which is the core of nuclear fission heat generation. The control rods 1121 are inserted / extracted to adjust the neutron flux to control the core power. The main pump drives the coolant to flow through the hot leg to the tube side of the steam generator 101, and the pressurizer 1103 maintains the pressure to prevent boiling, and then the coolant is sent back to the core 1101 through the cold leg. The in-core monitoring system monitors the power distribution of the core in real time. The secondary side 120 is a non-radioactive steam loop, and the shell side of the steam generator 101 absorbs heat to convert into high-pressure steam, which drives the turbine 1201 to rotate and converts thermal energy into mechanical energy to generate electricity. The exhaust steam is condensed into liquid water by the condenser 1202, and then pressurized by the main feedwater pump to complete the cycle. When working, the core 1101 generates heat through uranium nuclear fission, the primary side 110 transfers the heat to the secondary side 120, and the secondary side 120 realizes energy conversion.

[0050] When the turbine 1201 is subjected to load rejection, one of the main pumps is tripped, one of the main feedwater pumps is tripped, and other scenarios that require the primary side 110 to quickly reduce power, the fast power reduction system 1102 receives a trigger signal, and its control unit 1122 generates a rod drop signal to control the target rod group for fast power reduction to fall into the core 1101, thereby quickly reducing 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 discussion purposes, 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] At step S210, it is determined whether the current power of the core is greater than the target power.

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

[0056] At step S220, in response to the current power being greater than the target power, a target rod bank for rapid power reduction is selected from the gray rod bank and at least part of the black rod bank in the regulating rod bank according to a target sequence, wherein the target sequence is a drop rod sequence determined based on the insertion sequence of the gray rod bank and at least part of the black rod bank.

[0057] In some embodiments, the gray rod bank includes a first group of power regulating rod bank, a second group of power regulating rod bank, a third group of power regulating rod bank and a fourth group of power regulating rod bank for power regulation. At least part of the black rod bank includes a fifth group of power regulating rod bank for power regulation, or includes a fifth group of power regulating rod bank and a sixth group of power regulating rod bank for power regulation. Here, power regulation is functionally equivalent to reactivity regulation, temperature regulation. Taking a third-generation non-power pressurized water reactor nuclear power plant with a capacity of 1000 MW as an example, the core includes 37 control rods, and the control rod bank includes MA (4 rods), MB (4 rods), MC (4 rods), MD (4 rods), M1 (4 rods), M2 (8 rods) and AO (9 rods), wherein the M rod bank (MA, MB, MC, MD, M1 and M2 are collectively referred to as the M rod bank) is mainly used to compensate for the change of reactivity caused by the change of operating conditions such as burnup, temperature, power level, etc., and the AO rod bank is mainly used for control of the axial power distribution of the core. MA, MB, MC and MD in the control rod bank are gray rod banks (GRCA), and M1, M2 and AO are black rod banks (RCCA). The target rod bank for rapid power reduction in the embodiments of the present application is selected from MA, MB, MC, MD and M1, or selected from MA, MB, MC, MD, M1 and M2, and the AO rod bank which is specially used for axial power distribution control is not used. Hereinafter, an example is described with the target rod bank selected from MA, MB, MC, MD, M1 and M2.

[0058] The M rod bank contains two insertion sequences, namely MA-MB-MC-MD-M1-M2 (sequence 1) and MD-MC-MB-MA-M1-M2 (sequence 2).

[0059] For the case of sequence 1, MA is first inserted into the core during operation, followed by MB, MC, MD, M1 and M2 in turn. The drop rod sequence, i.e. the target sequence, is determined in turn based on this insertion sequence. Exemplarily:

[0060] a) If MA is not fully inserted into the core, the first group of rods to be dropped when the rapid power reduction system is triggered is MA (the first group of rods in the target sequence), followed by MA and MB (the second group of rods in the target sequence), MA, MB and MC (the third group of rods in the target sequence), MA, MB, MC and MD (the fourth group of rods in the target sequence), MA, MB, MC, MD and Ml (the fifth group of rods in the target sequence), MA, MB, MC, MD, Ml and M2 (the sixth group of rods in the target sequence).

[0061] b) If MA is fully inserted into the core, and MB is not fully inserted into the core, the first group of rods to be dropped when the rapid power reduction system is triggered is MB (the first group of rods in the target sequence), followed by MB and MC (the second group of rods in the target sequence), MB, MC and MD (the third group of rods in the target sequence), MB, MC, MD and Ml (the fourth group of rods in the target sequence), MB, MC, MD, Ml and M2 (the fifth group of rods in the target sequence).

[0062] c) If MA and MB are fully inserted into the core, and MC is not fully inserted into the core, the first group of rods to be dropped when the rapid power reduction system is triggered is MC (the first group of rods in the target sequence), followed by MC and MD (the second group of rods in the target sequence), MC, MD and Ml (the third group of rods in the target sequence), MC, MD, Ml and M2 (the fourth group of rods in the target sequence).

[0063] d) If MA, MB and MC are fully inserted into the core, and MD is not fully inserted into the core, the first group of rods to be dropped when the rapid power reduction system is triggered is MD (the first group of rods in the target sequence), followed by MD and Ml (the second group of rods in the target sequence), MD, Ml and M2 (the third group of rods in the target sequence).

[0064] e) If MA, MB, MC and MD are fully inserted into the core, and Ml is not fully inserted into the core, the first group of rods to be dropped when the rapid power reduction system is triggered is Ml (the first group of rods in the target sequence), followed by Ml and M2 (the second group of rods in the target sequence).

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

[0066] For sequence 2, the sequence of dropped rods is determined similarly to sequence 1, and MA to MD in the above sequence 1 are replaced by MD to MA correspondingly, which will not be described in detail here.

[0067] According to the above situation and the falling rod sequence, a target rod group for fast power reduction is selected. Embodiments of the present application determine the target sequence according to the insertion sequence, which is simple and efficient, does not involve complex combinations of a large number of rod groups, makes the calculation more convenient, and can determine a unique optimal rod group combination.

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

[0069] It should be noted that when i=1, the i-th rod group in the target sequence includes the operating rod group that is not fully inserted into the core at present and the 0-th rod group inserted after the operating rod group in the insertion sequence, which means that the first rod group in the target sequence only includes the operating rod group that is not fully inserted into the core at present, as in the above situation a), the first rod group in the target sequence includes MA. When i=2, the i-th rod group in the target sequence includes the operating rod group that is not fully inserted into the core at present and the 1-st rod group inserted after the operating rod group in the insertion sequence, as in the above situation a), the second rod group in the target sequence includes MA and MB. Similarly, the target sequence corresponding to the above situation a) includes a total of 6 rod groups, N=5. Similarly, the target sequence corresponding to the above situation b) includes a total of 5 rod groups, N=4.

[0070] In an exemplary embodiment, the in-core monitoring system determines the corresponding target rod group under the current core state according to the real-time state parameters of the power plant, including the current power level of the core 1101, the current operating rod position of the control rod 1121 of the core 1101, and the core monitoring model of the actual burnup history of the power plant, according to the preset calculation logic, calls the core monitoring system calculation core, determines the corresponding target rod group under 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, i.e., the falling rod combination according to the target rod group is completed, the transient demand of the unit fast power reduction is met. It should be understood that the function of determining the target rod group for fast power reduction can also be realized by other systems or calculation modules.

[0071] In some embodiments, referring to Figure 3 The method 300 of determining the target rod group according to the target sequence includes the following steps.

[0072] At step S310, the drop-in power after falling into the i-th group of rods is obtained.

[0073] In some embodiments, the core on-line monitoring system is used to perform a neutronics calculation, search the core power after falling into the corresponding group of rods, and obtain the corresponding drop-in power. The power search is a function of the core on-line monitoring system, and will not be described in detail here.

[0074] At step S320, it is determined whether the obtained drop-in power is greater than the target power Pt.

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

[0076] It should be noted that for i = 1, the drop-in rod group corresponding to the obtained drop-in power in the target order is the 1st group of rods, and there is no group of rods before the 1st group of rods, so the drop-in j-th group of rods is not required, and the comparison power Pj is the current power P0 of the core. For i = 2, the drop-in rod group corresponding to the obtained drop-in power in the target order is the 2nd group of rods, and the j-th group of rods is the preceding group of rods of the 2nd group of rods, i.e., the 1st group of rods, and the comparison power Pj is the drop-in power P1 after falling into the 1st group of rods. For i = 3, the drop-in rod group corresponding to the obtained drop-in power in the target order is the 3rd group of rods, and the j-th group of rods is the preceding group of rods of the 3rd group of rods, i.e., the 2nd group of rods, and the comparison power Pj is the drop-in power P2 after falling into the 1st group of rods.

[0077] In some embodiments, the one of the comparison power and the obtained drop-in power that is closer to the target power is determined by comparing the first absolute value of the difference between the obtained drop-in power and the target power with the second absolute value of the difference between the comparison power and the target power. Specifically, if the first absolute value is less than the second absolute value, the obtained drop-in power is closer to the target power, and the drop-in rod group corresponding to the obtained drop-in power is determined as the target rod group. For example, for the above case a), when i = 1, the 1st group of rods is the target rod group, and when i = 2, the 2nd group of rods is the target rod group. If the first absolute value is greater than or equal to the second absolute value, the comparison power is closer to the target power, and the drop-in rod group corresponding to the comparison power is determined as the target rod group. For example, for the above case a), when i = 1, no rods need to be dropped, and when i = 2, the 1st group of rods is the target rod group.

[0078] At step S340, in response to the acquired drop-in power being greater than the target power Pt, the drop-in power after the (i+1)th group of rods is acquired for i≤N, and the step S320 of judging whether the acquired drop-in power is greater than the target power is returned to.

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

[0080] The method 300 of determining the target rod group according to the target order is further described below with the above case a) as an example.

[0081] Step 1, the drop-in power P1 after the 1st group of rods is acquired.

[0082] 1.1 If P1≤Pt, the closeness of P0, P1 and Pt is compared: if P0-Pt≤Pt-P1, no rod dropping is needed; if P0-Pt>Pt-P1, the target rod group is determined as the 1st group of rods, i.e. MA. The calculation is exited.

[0083] 1.2 If P1>Pt, Step 2 is entered.

[0084] Step 2, the drop-in power P2 after the 2nd group of rods is acquired.

[0085] 2.1 If P2≤Pt, the closeness of P1, P2 and Pt is compared: if P1-Pt≤Pt-P2, the target rod group is determined as the 1st group of rods, i.e. MA; if P1-Pt>Pt-P2, the target rod group is determined as the 2nd group of rods, i.e. MA and MB. The calculation is exited.

[0086] 2.2 If P2>Pt, Step 3 is entered.

[0087] Step 3, the drop-in power P3 after the 3rd group of rods is acquired.

[0088] 3.1 If P3≤Pt, the closeness of P2, P3 and Pt is compared: if P2-Pt≤Pt-P3, the target rod group is determined as the 2nd group of rods, i.e. MA and MB; if P2-Pt>Pt-P3, the target rod group is determined as the 3rd group of rods, i.e. MA, MB and MC. The calculation is exited.

[0089] 3.2 If P3>Pt, Step 4 is entered.

[0090] Step 4, the drop-in power P4 after the 4th group of rods is acquired.

[0091] 4.1 If P4≤ Pt, compare the closeness of P3, P4 and Pt: if P3-Pt≤ Pt-P4, determine the target rod group as the 3rd group of rods, i.e. MA, MB and MC; if P3-Pt> Pt-P4, determine the target rod group as the 4th group of rods, i.e. MA, MB, MC and MD. Exit the calculation.

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

[0093] Step 5, obtain the landing power P5 after landing in the 5th group of rods.

[0094] 5.1 If P5≤ Pt, compare the closeness of P4, P5 and Pt: if P4-Pt≤ Pt-P5, determine the target rod group as the 4th group of rods, i.e. MA, MB, MC and MD; if P4-Pt> Pt-P5, determine the target rod group as the 5th group of rods, i.e. MA, MB, MC, MD and M1. Exit the calculation.

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

[0096] Step 6, obtain the landing power P6 after landing in the 6th group of rods.

[0097] 6.1 If P6≤ Pt, compare the closeness of P5, P6 and Pt: if P5-Pt≤ Pt-P6, determine the target rod group as the 5th group of rods, i.e. MA, MB, MC, MD and M1; if P5-Pt> Pt-P6, determine the target rod group as the 6th group of rods, i.e. MA, MB, MC, MD, M1 and M2. Exit the calculation.

[0098] 6.2 If P6> Pt, determine the target rod group as the 6th group of rods. Exit the calculation.

[0099] In the above process, if the judgment condition is met, the process ends, or if all M rod groups have landed in the core, the process ends. For the case where all M rod groups have landed in the core, if Pn of all M rod groups landing in the core is greater than Pt, the target rod group is determined as all M rod groups.

[0100] The embodiments of the present application realize that the selected target rod group can make the power after rod landing closest to the target power. Assuming that the current power is 100% RTP, the current rod position is sequence 1 and MA has not completely inserted into the core, Figure 4 The power after rod landing in different combinations is given. According to the method provided by the embodiments of the present 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] The embodiment of the present application can match multiple target power steps, and can quickly and accurately adjust the power to the specified level after triggering the fast power reduction system through the closest rod falling method of the target power, prevent the power from deviating from the target power after the rod falling, avoid large deviation in both high and low directions, achieve faster reactive control response, make the reactor quickly reach steady state balance, and meet the transient demand of fast power reduction of the unit. In some embodiments, the target power is greater than or equal to 40% of the rated reactor power (RTP), that is, the target power is greater than or equal to 40% of the rated reactor power (RTP). The embodiment considers the total value of the control rod group for fast power reduction, and further improves 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 the control rod overlap is further included, to prepare for restoring the automatic control function of the corresponding rod group (such as the M rod group). Specifically, the next rod group of the target rod group in the insertion sequence is controlled to be inserted into the reactor core by a target number of steps, so that the next rod group and the previous rod group of the next rod group in the insertion sequence establish an overlap. In one exemplary embodiment, for sequence 1 described above, the target rod groups are MA and MB, MC is controlled to be inserted into the reactor core until MC is inserted to the position corresponding to the normal overlap with MB, and the insertion of MC is stopped. The overlap step is restored in this way.

[0104] In some embodiments, after the overlap restoring 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 core being greater than the secondary side power, the corresponding rod group in the gray rod group and at least part of the black rod group is controlled to be inserted into the reactor core according to the insertion sequence, so that the primary side power and the secondary side power are matched; in response to the primary side power being less than the secondary side power, the turbine power of the secondary side is reduced, so that the primary side power and the secondary side power are matched.

[0105] In some embodiments, after the primary side power and the secondary side power are matched, a step of restoring the insertion limit is further included. Specifically, it is judged whether the rod group currently inserted into the reactor core has broken through the insertion limit; in response to the rod group currently inserted into the reactor core breaking through the insertion limit, boron is started to be adjusted, and the rod group currently inserted into the reactor core is restored above the insertion limit. For different initial rod positions, the deeper the initial rod position, the greater the possibility of breaking through the insertion limit after the rod falling, and the insertion limit is restored by adjusting the boron.

[0106] The embodiment of the present application determines the target rod group based on the current power level of the core, is suitable for various operation power levels, and thus has wider applicability. The embodiment of the present application selects the target rod group for rapid power reduction from the gray rod group and the black rod group, has smaller disturbance to the core after the rod drop, and reduces the influence on the unit shutdown capability and the core power distribution. Moreover, the single-group rod value of the gray rod group and the black rod group is smaller, and the power after the rod drop can be more accurately controlled. Meanwhile, the gray rod group and the black rod group are allowed to be inserted into the core during normal operation, while the shutdown rod group needs to be completely withdrawn from the core during normal operation, and thus the gray rod group and the black rod group are recovered more quickly than the shutdown rod group after the rod drop. In addition, the embodiment of the present application determines the target rod group through an online calculation method, instead of manual calculation and setting, simplifies the work, reduces the risk of human error, and eliminates the problem of errors in the results caused by core burnup in the offline periodic calculation method.

[0107] An embodiment of the present application also provides a rapid power reduction system. The rapid power reduction system comprises a gray rod group, a black rod group, and a control unit configured to execute the rapid power reduction method 200 shown in the figure. Figure 2

[0108] An embodiment of the present application also provides a pressurized water reactor. The pressurized water reactor comprises a core, a core online monitoring system, and the rapid power reduction system described above.

[0109] The above has described the basic concept, and it is obvious that the above-mentioned disclosure of the application is only used as an example and does not constitute a limitation on the present application. Although the modifications, improvements and corrections of the present application are not explicitly described, the skilled in the art can make various modifications, improvements and corrections to the present application. Such modifications, improvements and corrections are suggested in the present application, and thus such modifications, improvements and corrections still belong to the spirit and scope of the exemplary embodiments of the present application.

[0110] Meanwhile, specific words are used in the present application to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" means a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that the "one embodiment" or "one alternative embodiment" mentioned in different positions in the specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be properly combined.

[0111] ​For simplicity and to facilitate understanding of the terms used herein, a number of features of the embodiments described herein are sometimes grouped together in a single embodiment, figure or description of an embodiment. However, this method of disclosure should not be construed to mean that there are fewer features or less disclosure in the present application than there would otherwise be. Rather, the embodiments described herein have many individual features that are described in many different combinations.

[0112] While the present application has been described with reference to the currently preferred embodiments, those skilled in the art will recognize that various equivalent changes in form and detail can be made therein without departing from the spirit and scope of the application. Accordingly, the disclosed application is intended to be broadly construed and interpreted, to include all such equivalents as well.

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 for rapid power reduction from a gray rod bank and at least a partial black rod bank in the rod banks according to a target sequence, wherein the target sequence is determined based on a drop sequence of the gray rod bank and the at least a partial black rod bank; controlling the target rod bank to drop into the reactor core.

2. The fast power-down method of claim 1, wherein, The selecting a target rod bank for rapid power reduction from a gray rod bank and at least a partial black rod bank in the rod banks according to a target sequence comprises: determining the target sequence according to an insertion sequence of the gray rod bank and the at least a partial black rod bank and a current operating rod position, wherein an i-th rod bank in the target sequence comprises a current operating rod bank and (i-1)-th rod banks in the insertion sequence which are inserted after the current operating rod bank, i is an integer and 1≤i≤(N+1), N is a total number of rod banks which are inserted after the current operating rod bank in the insertion sequence and are included in the gray rod bank and the at least a partial black rod bank; determining the target rod bank according to the target sequence.

3. The fast power-down method of claim 2, wherein, The determining the target rod bank according to the target sequence comprises: obtaining a drop power after an i-th rod bank drops; determining whether the obtained drop power is greater than the target power; in response to the obtained drop power being less than or equal to the target power, determining a drop rod bank corresponding to one of a comparison power and the obtained drop power which is closer to the target power as the target rod bank, wherein the comparison power is a drop power after a j-th rod bank, the j-th rod bank being a previous rod bank of a drop rod bank corresponding to the obtained drop power in the target sequence; in response to the obtained drop power being greater than the target power, for i≤N, obtaining a drop power after a (i+1)-th rod bank drops, and returning to the step of determining whether the obtained drop power is greater than the target power; for i=(N+1), determining the (N+1)-th rod bank as the target rod bank.

4. The fast power-down method of claim 3, wherein, Performing a neutronics calculation using a reactor core in-line monitoring system to search for a reactor core power after a corresponding rod bank drops to obtain a corresponding drop power.

5. The fast power-down method of claim 1, wherein, The gray rod bank comprises 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 a partial black rod bank comprises a fifth group of power regulation rod banks, or comprises a fifth group of power regulation rod banks and a sixth group of power regulation rod banks.

6. 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.

7. The fast power-down method of any of claims 1-6, wherein, After the controlling the target rod bank to drop into the reactor core, the method further comprises: controlling a previous rod bank of the target rod bank in the insertion sequence to be inserted into the reactor core by a target number of steps, so that the previous rod bank and a next rod bank of the previous rod bank in the insertion sequence establish an overlap.

8. The fast power-down method of claim 7, wherein, After the controlling a previous rod bank of the target rod bank in the insertion sequence to be inserted into the reactor core by a 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.

9. The fast power-down method of claim 8, 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.

10. A fast power-down system, comprising: 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 1-9.

11. A pressurized water reactor, characterized by a reactor comprising a core, an in-core monitoring system, and the fast power reduction system of claim 10.

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