A method and device for calculating the control rod worth of a nuclear power plant by the drop rod method

Abstract

The present application relates to the technical field of nuclear power plant safety testing, and particularly relates to a calculation method and a calculation device for measuring the value of a control rod in a nuclear power plant by a falling rod method, comprising the following steps: obtaining the initial time t0 of a control rod to be measured before the falling rod starts, the neutron flux density n0 corresponding to the initial time t0, the time t1 when the falling rod ends, the neutron flux density n1 corresponding to the time t1, and the neutron flux density n2 corresponding to an arbitrary time t2 after the falling rod ends; calculating the period T1 at the time after the falling rod; obtaining the average generation time Λ of prompt neutrons and the total effective share β of delayed neutrons in all fission neutrons; and calculating the value of the control rod to be measured. eff Compared with the traditional method, the present application considers the influence of prompt neutrons, does not need to artificially judge the starting point of a gradual value, and after introducing the influence factor of prompt neutrons, does not need to wait for the neutron flux to approach the gradual value, and can have a wider range of data points for selection.

Description

Technical Field

[0001] This invention relates to the field of nuclear power plant safety testing technology, specifically to a method and apparatus for calculating the value of control rods in nuclear power plants using the drop rod method. Background Technology

[0002] The total value of reactor control rods is directly related to the reactor's shutdown margin. The drop rod method measures the control rod value by obtaining measured shutdown data from a real-time data acquisition system on the power plant's computer, and then calculating the value using an offline digital reactivity analyzer program. The traditional drop rod method makes two assumptions: first, that the density of slow-emission neutron precursor nuclei remains essentially constant within a very short time before and after the drop; and second, that the power level rapidly changes to its asymptotic value after the drop. The advantage of the traditional drop bar method is its simplicity, as shown in formula (1) below. However, its disadvantage is that the second assumption does not consider the influence of instantaneous neutrons, and it is necessary to manually determine the starting point of an asymptotic value, which will introduce measurement errors.

[0003] Summary of the Invention

[0004] The purpose of this invention is to propose a calculation method and device for measuring the value of control rods in nuclear power plants using the drop rod method. This method addresses the technical problem that traditional methods assume the influence of transient neutrons and require manual determination of the starting point of an asymptotic value.

[0005] The technical solution of the present invention:

[0006] The first aspect of this invention provides a method for calculating the value of control rods in nuclear power plants using the drop rod method, the method comprising the following steps:

[0007] Obtain the initial time t0 before the start of the test control rod drop and the corresponding neutron flux density n0, the end time t1 before the start of the drop and the corresponding neutron flux density n1, and any time t2 after the end of the drop and the corresponding neutron flux density n2. Based on the end time t1, the corresponding neutron flux density n1, the arbitrary time t2, and the corresponding neutron flux density n2, and in conjunction with formula (2), calculate the period T1 after the drop.

[0008]

[0009] Obtain the average generation time Λ of instantaneous neutrons and the total effective share β of delayed neutrons in all fission neutrons. eff .

[0010] Based on the neutron flux density n0 at the initial time t0, the mean generation time Λ of instantaneous neutrons, and the total effective share β of delayed neutrons in all fission neutrons. eff The value of the control rod under test, |ρ1|, is calculated using the period T1 after the rod falls, combined with formula (3).

[0011]

[0012] The process involves obtaining the initial time t0 before the start of the test control rod drop and the corresponding neutron flux density n0, the end time t1 before the start of the drop and the corresponding neutron flux density n1, and any time t2 after the drop and the corresponding neutron flux density n2. This includes: confirming that the reactor core is in a critical state before the start of the drop test; recording the initial time t0 before the start of the drop test and the corresponding neutron flux density n0 measured by external nuclear instruments; inserting the test control rod to the bottom of the reactor core at the start of the drop test; and recording the neutron flux density n1 at the end time t1 before the start of the drop test and the corresponding neutron flux density n2 measured by external nuclear instruments at any time t2 after the drop test.

[0013] The difference between the end time t1 and the initial time t0 of the drop bar is less than or equal to 1 second.

[0014] A second aspect of the present invention provides a calculation device for measuring the value of control rods using the drop rod method in nuclear power plants. The device includes an acquisition module and a calculation module. The acquisition module is used to acquire the following parameters for the control rod under test: the initial time t0 before the start of the drop rod and the neutron flux density n0 corresponding to the initial time t0; the end time t1 of the drop rod and the neutron flux density n1 corresponding to the end time t1; any time t2 after the end of the drop rod and the neutron flux density n2 corresponding to any time t2; the average generation time Λ of the instantaneous neutrons; and the total effective share β of delayed neutrons among all fission neutrons. eff .

[0015] The calculation module is used to calculate the period T1 after the rod falls, based on the time t1 at the end of the rod fall, the neutron flux density n1 corresponding to the time t1 at the end of the rod fall, any time t2, and the neutron flux density n2 corresponding to any time t2, and in combination with formula (2).

[0016]

[0017] And based on the neutron flux density n0 at the initial time t0, the mean generation time Λ of the instantaneous neutrons, and the total effective share β of the delayed neutrons in all fission neutrons. effThe value of the control rod under test, |ρ1|, is calculated using the period T1 after the rod falls, combined with formula (3).

[0018]

[0019] A third aspect of the present invention provides a computer-readable storage medium having stored executable instructions of a computer thereon, which, when executed by a processor, implement a method for calculating the value of control rods in a nuclear power plant using the drop rod method.

[0020] A fourth aspect of the present invention provides an electronic device, characterized in that it includes a processor and a memory. The processor is used to execute a calculation method for measuring the value of control rods using the drop rod method in nuclear power plants; and the memory is used to store executable instructions of the processor.

[0021] The beneficial effects of this invention are:

[0022] This invention proposes a method and apparatus for calculating the value of control rods in nuclear power plants using the drop rod method. Compared with traditional methods, it considers the influence of transient neutrons, eliminates the need for manually determining the starting point of an asymptotic value, and introduces an influence factor for transient neutrons. After that, there is no need to wait for the neutron flux to approach the asymptotic value, and there can be a wider range of data points to select. Attached Figure Description

[0023] Figure 1 A flowchart illustrating a method for calculating the value of control rods in nuclear power plants using the drop rod method, provided as an embodiment of the present invention. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0025] like Figure 1 At least one embodiment of the present invention provides a method for calculating the value of control rods in nuclear power plants using the drop rod method. The execution entity of this calculation method can be a processor or a server, etc. The calculation method includes the following steps.

[0026] S1: Obtain the initial time t0 before the start of the test control rod drop and the neutron flux density n0 corresponding to the initial time t0, the end time t1 before the start of the drop and the neutron flux density n1 corresponding to the end time t1, and any time t2 after the end of the drop and the neutron flux density n2 corresponding to any time t2.

[0027] S1.1: Before the drop test begins, confirm that the core is in a critical state.

[0028] S1.2: Record the initial time t0 of the control rod under test before the rod drops begin, and the neutron flux density n0 corresponding to the initial time t0 measured by the external nuclear instrument.

[0029] S1.3: At the start of the drop test, the control rod to be tested is inserted to the bottom of the pile.

[0030] S1.4: After the drop test, record the neutron flux density n1 corresponding to the control rod at the end of the drop test at time t1 and the end of the drop test at time t1 measured by the external nuclear instrument, as well as the neutron flux density n2 corresponding to any time t2 after the drop test and any time t2 measured by the external nuclear instrument.

[0031] S2: Based on the time t1 at which the rod falls, the neutron flux density n1 corresponding to the time t1 at which the rod falls, any time t2, and the neutron flux density n2 corresponding to any time t2, and combined with formula (2), calculate the period T1 at the time after the rod falls.

[0032]

[0033] S3: Obtain the mean generation time Λ of instantaneous neutrons and the total effective share β of delayed neutrons in all fission neutrons. eff .

[0034] S4: Based on the neutron flux density n0 at the initial time t0, the mean generation time Λ of instantaneous neutrons, and the total effective share β of delayed neutrons in all fission neutrons. eff The value of the control rod under test, |ρ1|, is calculated using the period T1 after the rod falls, combined with formula (3).

[0035]

[0036] This calculation method is applicable when the difference between the end time t1 and the initial time t0 of the drop bar is less than or equal to 1 second.

[0037] At least one embodiment of this application also provides a calculation device for measuring the value of control rods using the drop rod method in nuclear power plants. This calculation device includes an acquisition module and a calculation module. The acquisition module is used to acquire the following information for the control rod under test: the initial time t0 before the start of the drop rod and the neutron flux density n0 corresponding to the initial time t0; the end time t1 of the drop rod and the neutron flux density n1 corresponding to the end time t1; any time t2 after the end of the drop rod and the neutron flux density n2 corresponding to any time t2; the average generation time Λ of the instantaneous neutrons; and the total effective share β of delayed neutrons among all fission neutrons. effThe calculation module is used to calculate the period T1 after the rod falls, based on the end time t1, the neutron flux density n1 corresponding to the end time t1, any time t2, and the neutron flux density n2 corresponding to any time t2, and in conjunction with formula (2).

[0038]

[0039] And based on the neutron flux density n0 at the initial time t0, the mean generation time Λ of the instantaneous neutrons, and the total effective share β of the delayed neutrons in all fission neutrons. eff The value of the control rod under test, |ρ1|, is calculated using the period T1 after the rod falls, combined with formula (3).

[0040]

[0041] The computing device is the same as the computing device corresponding to the calculation method for measuring the value of control rods in a nuclear power plant using the drop rod method provided in the above-described embodiments of this application. Therefore, it can at least achieve the above-described corresponding technical effects, which will not be elaborated here.

[0042] At least one embodiment of this application also provides an electronic device, which includes a processor and a memory. The memory is used to store instructions executable by the processor, such as application programs. There can be one or more processors. The application programs stored in the memory can include one or more modules, each corresponding to a set of instructions. Furthermore, the processor is configured to execute instructions to perform the aforementioned method for calculating the value of control rods in a nuclear power plant using the drop rod method.

[0043] The electronic device may also include a power supply component configured for power management, a wired or wireless network interface configured to connect the electronic device to a network, and an input / output (I / O) interface. The electronic device may operate on an operating system stored in memory, such as Windows Server™, Mac OSX™, Unix™, Linux™, FreeBSD™, or similar.

[0044] An embodiment of this application provides a computer-readable storage medium. When the instructions in the storage medium are executed by the processor of the electronic device, the electronic device is able to execute a method for calculating the value of control rods measured by the drop rod method in a nuclear power plant. This calculation method is executed by a proxy program and includes: obtaining the initial time t0 before the start of the drop rod and the neutron flux density n0 corresponding to the initial time t0, the end time t1 of the drop rod and the neutron flux density n1 corresponding to the end time t1, and any time t2 after the drop rod ends and the neutron flux density n2 corresponding to any time t2. Based on the end time t1 of the drop rod, the neutron flux density n1 corresponding to the end time t1, the arbitrary time t2, and the neutron flux density n2 corresponding to the arbitrary time t2, and in conjunction with formula (2), the period T1 after the drop rod is calculated.

[0045]

[0046] Obtain the average generation time Λ of instantaneous neutrons and the total effective share β of delayed neutrons in all fission neutrons. eff Based on the neutron flux density n0 at the initial time t0, the mean generation time Λ of instantaneous neutrons, and the total effective share β of delayed neutrons in all fission neutrons. eff The value of the control rod under test, |ρ1|, is calculated by combining the period T1 after the rod falls with formula (3).

[0047]

[0048] Those skilled in the art will recognize that the algorithmic steps of the various examples described in conjunction with the embodiments disclosed in this application can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0049] In the several embodiments provided in this application, it should be understood that the disclosed computing methods and computing devices can be implemented in other ways. For example, the computing device embodiments described above are merely illustrative. For instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules may be combined or integrated into another system, or some features may be ignored or not executed.

[0050] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the calculation methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program verification codes, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0051] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the computing devices and electronic devices described above can be referred to the corresponding processes in the foregoing computing method embodiments, and will not be repeated here.

[0052] To better understand this invention, the inventive concept is explained based on the principle of the drop rod method, considering the neutron flux density n0 before the drop rod; the neutron flux density n1 after the drop rod; the reactivity ρ0 before the drop rod; the reactivity ρ1 after the drop rod; and the total effective share β of delayed neutrons in all fission neutrons. eff ; mean generation time Λ of instantaneous neutrons; precursor nucleus concentration C of the i-th delayed neutron group at time t. i (t); the intensity q of the external neutron source; the decay constant λ of the i-th group of delayed neutron precursor nuclear fission fragments. i After the rod falls, the reactor period is T1, and the neutron dynamics equation before the rod falls is described as formula (4).

[0053]

[0054] The neutron dynamics equations at the post-drop point are described by formula (5).

[0055]

[0056] Assuming that the density of the slow-emitting neutron precursor nuclei remains essentially unchanged during this extremely short period after the rod is dropped, the above two equations become equation (6).

[0057]

[0058] The formula for the rapid drop bar is then obtained as formula (7).

[0059]

[0060] In the above formula (7), If the bar is in a critical state before it drops, i.e., ρ0 = 0, The above formula then becomes formula (8).

[0061]

[0062] Compared with traditional methods, this invention takes into account the influence of prompt neutrons, eliminates the need to manually determine the starting point of an asymptotic value, and introduces an influence factor for prompt neutrons. After that, there is no need to wait for the neutron flux to approach the asymptotic value, and there can be a wider range of data points to select.

[0063] To verify the accuracy of the improved formula, a comparative analysis is conducted. The reactor is initially in a critical state, assuming an extremely short rod drop time of 1E-4s, a rod drop value of 1000 pcm, and delayed neutron emission data as shown in Table 1.

[0064] Table 1 Delayed Neutron Data

[0065]

[0066] Table 2 shows a comparison between the present invention and conventional techniques for measuring the reactivity of a dropped rod.

[0067] Table 2 Comparison of reactive results after rod drop at instantaneous moment.

[0068]

[0069] As can be seen from Table 2, the optimized dropping rod method, compared with the traditional method, takes into account the influence of transient neutron changes and introduces the influence factor of transient neutrons. Afterward, there is no need to wait for the neutron flux to approach its asymptotic value, allowing for a wider range of data points to be selected. It should be noted that both the traditional method and this calculation method have relatively high requirements for the time of data processing selection. As can be seen from Table 2, when the selection time reaches 1 second, the reaction error of both methods is relatively large. This is because when the time reaches the second level, the influence of delayed neutron emission cannot be ignored.

[0070] The following calculation of reactivity is based on the initial values ​​of t0 = 0, t1 = 0.0001, and t2 = 0.0002.

[0071] The optimized formula for the dropping bar method is as follows: In the formula, Λ and λ i β ieff and β eff All of these are neutronics parameters, considered constants during the experiment, and can be calculated from theoretical data. Here, we take the data from Table 1, where Λ is 2 × 10⁻⁵ s.

[0072] Before the test, the reactor core was confirmed to be in a critical state. At the start of the test, the control rod to be tested was inserted to the bottom of the reactor. Before the rod was dropped, t0 = 0, and the corresponding external nuclear instrument signal value was recorded as n0 = 1. Based on the rod dropping time, the end time of the rod dropping was determined to be t1 = 0.0001, and the corresponding external nuclear instrument signal value was recorded as n1 = 0.980278. Any time after the rod dropping was completed was selected. For ease of example, t2 = 0.0002 was taken, and the corresponding external nuclear instrument signal value was recorded as n2 = 0.93357. Among them, t0 and t1 are determined according to the actual rod dropping time, and t2 can be arbitrarily taken as the time point after the rod dropping. t2 is taken to calculate the period T1 after the rod dropping. The period T1 is calculated by formula (2) as follows.

[0073]

[0074] Substituting the above values ​​and the delayed neutron parameter into formula (3) yields the reactivity after the rod is dropped.

[0075]

[0076] The value of the control rod to be tested is |ρ1| = 1050.4 pcm.

[0077] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for calculating the value of control rods in nuclear power plants using the drop rod method, characterized in that, The method includes the following steps: The initial time t0 before the start of the test control rod drop and the neutron flux density n0 corresponding to the initial time t0, the end time t1 of the drop and the neutron flux density n1 corresponding to the end time t1, and any time t2 after the end of the drop and the neutron flux density n2 corresponding to the end time t2 are obtained. Based on the time t1 at which the rod falls, the neutron flux density n1 corresponding to the time t1, the arbitrary time t2, and the neutron flux density n2 corresponding to the arbitrary time t2, and in conjunction with formula (1), the period T1 after the rod falls is calculated. Obtain the average generation time Λ of instantaneous neutrons and the total effective share β of delayed neutrons in all fission neutrons. eff ; Based on the neutron flux density n0 corresponding to the initial time t0, the average generation time Λ of the instantaneous neutrons, and the total effective share β of the delayed neutrons in all fission neutrons. eff The value |ρ1| of the control rod under test is calculated using formula (2) based on the period T1 after the rod is dropped.

2. The calculation method according to claim 1, characterized in that, The process of acquiring the initial time t0 before the start of the test control rod drop and the neutron flux density n0 corresponding to the initial time t0, the end time t1 before the start of the drop and the neutron flux density n1 corresponding to the end time t1, and any time t2 after the end of the drop and the neutron flux density n2 corresponding to the end time t2 includes: Before the drop test begins, confirm that the reactor core is in a critical state; Record the initial time t0 of the control rod under test before the rod drops begin, and the neutron flux density n0 corresponding to the initial time t0 measured by the external nuclear instrument. At the start of the drop test, the control rod to be tested is inserted to the bottom of the pile; After the drop test, the neutron flux density n1 corresponding to the end time t1 of the drop test and the end time t1 measured by the external nuclear instrument is recorded, as well as the neutron flux density n2 corresponding to any time t2 after the drop test and the end time t2 measured by the external nuclear instrument.

3. The calculation method according to claim 1, characterized in that, The difference between the end time t1 and the initial time t0 of the drop bar is less than or equal to 1 second.

4. A calculation device for determining the value of control rods using the drop rod method in nuclear power plants, characterized in that, include: The acquisition module is used to acquire the initial time t0 before the start of the test control rod drop and the neutron flux density n0 corresponding to the initial time t0, the end time t1 before the start of the drop and the neutron flux density n1 corresponding to the end time t1, any time t2 after the end of the drop and the neutron flux density n2 corresponding to any time t2, the average generation time Λ of the instantaneous neutrons, and the total effective share β of delayed neutrons in all fission neutrons. eff ; The calculation module is used to calculate the period T1 after the rod falls based on the time t1 at which the rod falls, the neutron flux density n1 corresponding to the time t1 at which the rod falls, the arbitrary time t2, and the neutron flux density n2 corresponding to the arbitrary time t2, and in combination with formula (1). And based on the neutron flux density n0 corresponding to the initial time t0, the mean generation time Λ of the instantaneous neutrons, and the total effective share β of the delayed neutrons in all fission neutrons. eff The value |ρ1| of the control rod under test is calculated using formula (2) based on the period T1 after the rod is dropped.

5. A computer-readable storage medium having executable instructions stored thereon, characterized in that, When the executable instructions are executed by the processor, they implement the method for calculating the value of control rods in nuclear power plants using the drop rod method as described in any one of claims 1 to 3.

6. An electronic device, characterized in that, include: A processor for executing the calculation method for determining the value of control rods in nuclear power plants using the drop rod method as described in any one of claims 1 to 3; And a memory for storing the executable instructions of the processor.

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