Nuclear power station reactor control rod position measuring method

Abstract

The invention provides a nuclear power station reactor control rod position measurement method, relates to the technical field of reactor control rod position measurement, and aims to improve the measurement precision of reactor control rod position measurement. The number of the threshold groups of each coil group is the same as the number of the change zones corresponding to the positions of the coil groups, each threshold group comprises a plurality of threshold points, and the values of the threshold points of each coil group are different; and performing rod position detection based on the coding type rod position detector and the threshold group. The method has the advantages of higher measurement precision and higher reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of reactor control rod position measurement, and in particular to a method for measuring the position of a nuclear power plant reactor control rod. Background Art

[0002] The nuclear power plant reactors basically use coded rod position detectors designed based on the differential transformer principle. The electrical components of this type of detector are composed of a primary coil for excitation and a secondary coil for output based on electromagnetic induction, where the secondary coil is divided into an auxiliary coil and a measuring coil.

[0003] The traditional rod position measurement method sets a set of thresholds for each group of coils. When the actual output voltage of the coil group is higher than the threshold, the corresponding code value is logic 1. When the actual output voltage of the coil group is lower than the threshold, the corresponding code value is logic 0. The position of the control rod can be obtained by encoding the combination of each group of coils. The detector output changes with the rod position and the corresponding code value comparison output is as follows Figure 2 As shown in the figure. The position resolution of the measuring rod of this measurement method depends on the arrangement interval of the measuring coils. For example, if the interval between adjacent coils is 8 steps, the position resolution of the measuring rod is 8 steps. The corresponding theoretical optimal value of its measurement accuracy is only ±4 steps. Considering the measurement error, signal processing error, etc., the highest accuracy that can be achieved is generally ±6 steps. It can be seen that the accuracy of the existing measurement method is low.

[0004] Therefore, it is necessary to improve the reactor control rod position measurement method and enhance the measurement accuracy. Summary of the invention

[0005] The object of the present invention is to provide a method for measuring the position of control rods of a nuclear power plant reactor, which can improve the measurement accuracy.

[0006] The embodiments of the present invention are implemented by the following technical solutions:

[0007] A method for measuring the position of a control rod of a reactor in a nuclear power plant. The coded rod position detector comprises five coil groups, including an A coil group, a B coil group, a C coil group, a D coil group and an E coil group. The five coil groups are provided with a plurality of coils, which are numbered 0-m in sequence from the bottom to the top. The coil with the largest number and the coil with the number 0 are connected in series as auxiliary coils. Among the coils other than the auxiliary coils, the A coil group includes all coils with odd numbers, the B coil group includes coils with the number 4*i+2; the C coil group includes coils with the number 8*j+4; the D coil group includes coils with the number 16*p+8; the E coil group includes coils with the number 32*q+16, and i, j, p and q are all integers not less than 0. The method comprises the following steps:

[0008] At least one set of threshold value groups is set for each coil group, the number of threshold value groups for each coil group is the same as the number of change bands corresponding to the position of the coil group, each set of threshold value groups includes multiple threshold points, and the value of the threshold point of each coil group is different;

[0009] Rod position detection is performed based on the coded rod position detector and the threshold group.

[0010] Preferably, each set of the thresholds comprises a first high-pressure threshold point, a second high-pressure threshold point, a first low-pressure threshold point and a second low-pressure threshold point;

[0011] The first high pressure threshold point>the second high pressure threshold point>the second low pressure threshold point>the first low pressure threshold point.

[0012] The first high pressure threshold point>the second high pressure threshold point>the second low pressure threshold point>the first low pressure threshold point.

[0013] Preferably, the E-group coil group is provided with an E-group threshold group, and the E-group threshold group divides the voltage output of the E-group coil group into an E-group low-voltage section, an E-group transition section and an E-group high-voltage section;

[0014] The E group of coils divides the entire control rod travel into two equal parts through different high-pressure sections and low-pressure sections.

[0015] Preferably, a D group threshold group is set for the D group coil group; the D group threshold group divides the voltage output of each coil of the D group coil group into a D group low voltage section, a D group transition section and a D group high voltage section;

[0016] The E coil group and the D coil group divide the entire control rod stroke into four equal parts through different high-pressure sections and low-pressure sections.

[0017] Preferably, a C group threshold group is set for the C group coil group; the C group threshold group divides the voltage output of each coil of the C group coil group into a C group low voltage section, a C group transition section and a C group high voltage section;

[0018] The C coil group, the E coil group and the D coil group divide the entire control rod stroke into 8 equal parts.

[0019] Preferably, a B group threshold group is set for the B group coil group; the B group threshold group divides the voltage output of each coil of the B group coil group into a B group low voltage section, a B group transition section and a B group high voltage section;

[0020] The entire control rod travel is divided into 16 equal parts by the B coil group, the C coil group, the E coil group and the D coil group through different high-pressure sections and low-pressure sections.

[0021] Preferably, a group A threshold group is set for the group A coil group; the group A threshold group divides the voltage output of each coil of the group A coil group into a group A low voltage section, a group A transition section and a group A high voltage section.

[0022] Preferably, the method for performing rod position detection based on the coded rod position detector and the threshold group is: judging the section where the control rod is currently located according to the combination of the high voltage section and the low voltage section of the voltage output of each coil;

[0023] There is at least one corresponding transition section of the coil in any interval. The voltage output of each coil is compared with the single-step threshold of the coil in the corresponding transition section. If the voltage output of a certain coil is within the upper and lower intervals of a certain single-step threshold, the control rod position corresponding to the single-step threshold is the measurement rod position. The single-step threshold is obtained through actual measurement.

[0024] Preferably, the method for obtaining the single-step threshold is:

[0025] gradually obtaining the corresponding relationship between the voltage output of each coil in the entire stroke of the control rod and the position of the control rod at each step through actual measurement;

[0026] The voltage output of each coil corresponding to the position of the control rod in each step is used as a typical value of the voltage output of each coil in this step;

[0027] For each step of the position of the control rod, the average value of the voltage output typical value of the step and the typical values ​​of the voltage output of the two adjacent steps before and after the step is taken as the voltage output boundary value of the corresponding coil of the step, and then the corresponding interval of the voltage output of each coil at each step of the control rod position is obtained, and the corresponding interval is used as the single-step threshold.

[0028] Preferably, the coil with a greater voltage output difference between two adjacent steps has a greater weight;

[0029] For a certain interval, if there are multiple coils with transition sections, the measuring rod position determined by the coil with a higher weight is adopted.

[0030] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0031] The present invention divides each group of coils into high-voltage section, low-voltage section and transition section within the full stroke range of the control rod, and divides the rod position operation interval on this basis. By utilizing the characteristic that there is a unique corresponding relationship between the output voltage of at least one group of coils in the transition section of each interval and the rod position in the interval, the rod position determination with one-step resolution is performed, thereby improving the measurement accuracy.

[0032] The present invention helps to obtain a better value by assigning different weighted values, thereby further improving the rod position measurement accuracy;

[0033] The invention is easy to implement, does not require modification of the existing rod position detector, can be widely used in nuclear power plants that use rod position detectors based on the electromagnetic induction principle, has a very broad market prospect, and is easy to promote and implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic diagram of the structure of the electrical components of the rod position detector provided in Example 1 of the present invention;

[0035] Figure 2 A schematic diagram of the sections of each group of measuring coils of the rod position detector provided in Example 1 of the present invention;

[0036] Figure 3 This is a schematic diagram of the voltage output characteristics of each group of coils during the process of lifting the control rod from the bottom to the top provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0038] Example 1

[0039] This embodiment provides a method for measuring the position of a control rod of a nuclear power plant reactor. Figure 1The coded rod position detector includes 5 coil groups, including a coil group A, a coil group B, a coil group C, a coil group D and a coil group E. The 5 coil groups are provided with a plurality of coils, which are numbered 0-m in sequence from the bottom to the top, and the coil with the largest number and the coil with the number 0 are connected in series as auxiliary coils; among the coils other than the auxiliary coils, the coil group A includes all coils numbered with odd numbers, the coil group B includes coils numbered 4*i+2; the coil group C includes coils numbered 8*j+4; the coil group D includes coils numbered 16*p+8; the coil group E includes coils numbered 32*q+16, where i, j, p and q are all integers not less than 0; specifically, the primary coil is continuously wound from the bottom of the detector to the top of the detector, covering the entire control rod stroke, and providing an excitation magnetic field for the secondary coil. The secondary coils are the five coil groups mentioned above. The secondary coils are evenly arranged at certain intervals (such as 8 mechanical steps, i.e. 127mm) from the bottom of the detector to the top of the detector. It is particularly noted that the coils in the same group are connected in an anti-phase series manner of "head to head, tail to tail", and the last two ends are led out. The output of each group of measurement coils varies with the position of the control rod. Specifically, when the number of coils in a group of coils where the control rod driving rod is even (such as 0, 2, 4, ...), the output voltage of the group of coils is higher; when the number of coils in a group of coils where the control rod driving rod is odd (such as 1, 3, 5, ...), the output voltage of the group of coils is lower.

[0040] The method for measuring the position of control rods of a nuclear power plant reactor in this embodiment comprises the following steps:

[0041] At least one set of threshold value groups is set for each coil group, the number of threshold value groups for each coil group is the same as the number of change bands corresponding to the position of the coil group, each set of threshold value groups includes multiple threshold points, and the value of the threshold point of each coil group is different;

[0042] Rod position detection is performed based on the coded rod position detector and the threshold group.

[0043] The design principle of this embodiment is:

[0044] Corresponding to the number of coils included in each coil group of the detector, the output of each coil group has a corresponding number of variation bands.

[0045] So, for example, see Figure 2 The schematic diagram of the segmentation of each group of measuring coils of the rod position detector is shown in Figure 1. According to the above-mentioned change characteristics of the measuring coils, the output of each group of coils is divided into a low-voltage section, a high-voltage section and a transition section. The low-voltage section refers to the part with lower coil voltage output, corresponding to Figure 2In the dotted line marked part, the low-voltage section coil voltage is stable and maintains a low voltage output, and the voltage difference between adjacent steps is small; the high-voltage section refers to the part where the coil voltage output is higher, corresponding to Figure 2 In the middle dotted line marked part, the high-voltage section coil voltage is stable and maintains a higher voltage output, and the voltage difference between adjacent steps is small; the transition section refers to the part where the coil voltage output changes from high to low, corresponding to Figure 2 In the part marked with single dot line, the voltage difference between adjacent steps in the transition section is large and the voltage in each transition section shows a monotonically increasing or monotonically decreasing characteristic.

[0046] Generally speaking, the division of the three output sections is achieved by setting a voltage threshold, and the threshold is divided into a high-voltage threshold and a low-voltage threshold. When the coil output voltage is higher than the high-voltage threshold, it is considered to be in the high-voltage section, when the coil output is lower than the low-voltage threshold, it is considered to be in the low-voltage section, and when the coil output is between the high-voltage threshold and the low-voltage threshold, it is considered to be in the transition section. However, when the rod position measurement is actually performed, in order to simultaneously meet the purpose of improving the applicability of the rod position measurement (achieved by increasing the transition section, the threshold needs to be closer to the high- and low-voltage boundaries of the coil output, and the high- and low-voltage thresholds are larger) and error prevention (achieved by increasing the high-voltage section and the low-voltage section, the threshold needs to be farther from the high- and low-voltage boundaries of the coil output, and the high- and low-voltage thresholds are smaller), there may be overlapping areas between the three output sections, that is, the high-voltage section and the low-voltage section overlap with the transition section respectively.

[0047] Therefore, in this embodiment, each set of the thresholds includes a first high-pressure threshold point, a second high-pressure threshold point, a first low-pressure threshold point, and a second low-pressure threshold point;

[0048] The first high pressure threshold point>the second high pressure threshold point>the second low pressure threshold point>the first low pressure threshold point.

[0049] When the coil output voltage is higher than the first high-voltage threshold point, it is considered to be in the high-voltage section; when the coil output is lower than the first low-voltage threshold point, it is considered to be in the low-voltage section; when the coil output is between the second high-voltage threshold point and the second low-voltage threshold point, it is considered to be in the transition section. Therefore, there is an overlapping area between the transition section and the high-voltage section, and an overlapping area between the transition section and the low-voltage section, that is, the transition section area is enlarged at the same time, which is mainly used to determine the position of the control rod, that is, the applicability of the rod position measurement is increased, and the high-voltage section and low-voltage section areas are enlarged, which are mainly used for interval division, that is, avoiding the wrong division of the interval caused by the high and low voltage thresholds being set too close to the boundary, and improving the error prevention performance.

[0050] When actually measuring the rod position, for a coil group with multiple transition sections, the outputs of different transition sections are inconsistent. Therefore, in order to further improve the segmentation accuracy and the rod position measurement accuracy, different thresholds can be set for different output sections in different control rod travel intervals. In this embodiment, the preferred threshold setting method for each coil group is as follows:

[0051] First, the E-group coil group is provided with an E-group threshold group, and the E-group threshold group divides the voltage output of the E-group coil group into an E-group low-voltage section, an E-group transition section and an E-group high-voltage section;

[0052] The E group of coils divides the entire control rod travel into two equal parts through different high-pressure sections and low-pressure sections.

[0053] Then, a D group threshold group is set for the D group coil group; the D group threshold group divides the voltage output of each coil of the D group coil group into a D group low voltage section, a D group transition section and a D group high voltage section;

[0054] The E coil group and the D coil group divide the entire control rod stroke into four equal parts through different high-pressure sections and low-pressure sections.

[0055] Secondly, a C group threshold group is set for the C group coil group; the C group threshold group divides the voltage output of each coil of the C group coil group into a C group low voltage section, a C group transition section and a C group high voltage section;

[0056] The C coil group, the E coil group and the D coil group divide the entire control rod stroke into 8 equal parts.

[0057] Next, a B group threshold group is set for the B group coil group; the B group threshold group divides the voltage output of each coil of the B group coil group into a B group low voltage section, a B group transition section and a B group high voltage section;

[0058] The entire control rod travel is divided into 16 equal parts by the B coil group, the C coil group, the E coil group and the D coil group through different high-pressure sections and low-pressure sections.

[0059] Finally, a group A threshold group is set for the group A coil group; the group A threshold group divides the voltage output of each coil of the group A coil group into a group A low-voltage section, a group A transition section and a group A high-voltage section.

[0060] It is particularly noted that the high-pressure section and the low-pressure section of the coil group A do not exist obviously, and there is no need to use the high-pressure section and the low-pressure section to divide the control rod travel interval. Therefore, it can be decided whether to set the high-pressure section and the low-pressure section according to the actual output characteristics. If the high-pressure section and the low-pressure section are not divided, it is only necessary to divide the coil group A into corresponding 16 transition sections according to the 16 intervals determined by the aforementioned coil groups E, D, C and B.

[0061] According to the division of multiple high-voltage sections, low-voltage sections and transition sections of each coil group mentioned above, the outputs of the high-voltage section and the low-voltage section are relatively stable, and are located at the high and low voltage ends respectively. The difference between the high-voltage section and the low-voltage section is large, and can be used to divide the control rod travel interval; any coil transition section can be uniquely identified according to the interval defined by other coils (except for the E group coil, which has only one transition section and is unique); in any transition section, the coil output voltage changes monotonically with the rod position, that is, there is a single corresponding relationship between the control rod position at any step in any transition section and the coil voltage output; therefore, the rod position measurement with one-step resolution can be performed based on the above characteristics of the coil.

[0062] Furthermore, based on the above settings, the method for performing rod position detection based on the coded rod position detector and the threshold group is preferably: judging the current section of the control rod according to the combination of the high voltage section and the low voltage section of the voltage output of each coil;

[0063] In any interval, there is at least one corresponding transition section of the coil. The voltage output of each coil is compared with the single-step threshold of the coil in the corresponding transition section. If the voltage output of a coil is within the upper and lower intervals of a single-step threshold, the control rod position corresponding to the single-step threshold is the measured rod position. The single-step threshold is obtained through actual measurement. In this way, rod position measurement with 1-step resolution is achieved.

[0064] Furthermore, the method for obtaining the single-step threshold is:

[0065] The corresponding relationship between the voltage output of each coil in the entire stroke of the control rod and the position of the control rod at each step is gradually obtained through actual measurement; this process can be obtained through actual measurement, that is, the control rod is lifted and / or inserted throughout the stroke, and the output voltage of each coil corresponding to the position of the control rod at each step is recorded, Figure 3 This is a schematic diagram of the voltage output characteristics of each coil group during the process of lifting a control rod from the bottom to the top. This figure shows the voltage output changes of each coil group during the full stroke of the control rod from the bottom to the top. The curves are E, D, C, B, and A coil groups from top to bottom. It can be seen from the figure that by comparing the voltage of each coil with the threshold, the entire stroke of the control rod can be divided into different intervals. In any interval, there is a situation where a certain coil changes monotonically with the rod position (that is, the coil output has a unique corresponding relationship with the control rod position). Taking the D group coil as an example, the transition section (the circle as an example) has the following characteristics:

[0066] The circle is the transition section of the D group coil group, where the coil voltage increases monotonically with the rod position and has an obvious and identifiable rising process. In the figure, the voltage increases step by step with the rod position.

[0067] The voltage changes with the rod position and presents nonlinear characteristics. The voltage difference between two adjacent steps in the middle of the transition section is relatively obvious, while the voltage difference between two adjacent steps at the edge of the transition section is relatively unobvious.

[0068] The same transition section is divided into two different parts by the interval. Due to measurement errors, threshold settings and other reasons, the division points of the same transition section into different intervals are offset. Therefore, the coil output here may be divided into two adjacent different intervals. In order to improve the measurement accuracy of the rod position, the rod positions at two locations can be calculated separately and compared with the rod position intervals respectively, and the result that is closer to the interval division can be taken as the measurement rod position.

[0069] Therefore, in this embodiment, the voltage output of each coil corresponding to the position of the control rod at each step is used as the typical value of the voltage output of each coil at this step;

[0070] For each step of the position of the control rod, the typical value of the voltage output of the step and the average value of the typical values ​​of the voltage output of the two adjacent steps before and after the step are taken as the voltage output boundary value of the corresponding coil of the step, and then the corresponding interval of the voltage output of each coil of the control rod at each step position is obtained, and the corresponding interval is used as the single-step threshold. It is particularly noted that the first low voltage threshold, the first high voltage threshold, the second low voltage threshold and the second high voltage threshold of each coil and each interval can be set according to the actual output of the detector.

[0071] On the other hand, the coil with a larger voltage output difference between two adjacent steps has a larger weight;

[0072] For a certain interval, if there are multiple coils with transition sections, the measuring rod position determined by the coil with a higher weight is adopted.

[0073] Regarding the above design, according to the coil output characteristics, there is at least one corresponding coil transition segment in any interval. In particular, at some control rod positions, there are two coil transition segments at the same time. For this situation, it is necessary to comprehensively consider the output characteristics of the two transition segments to determine the rod position, for example, taking the average value of the rod positions determined by the two transition segments.

[0074] However, according to the coil output characteristics, the coil output changes nonlinearly with the control rod position. At the edge of the transition section, the voltage difference between two adjacent steps is relatively small, which is more susceptible to interference. The credibility of the rod position judgment based on this part is lower. In the middle of the transition section, the voltage difference between two adjacent steps is relatively large, which is less susceptible to interference. The credibility of the rod position judgment based on this part is higher. Therefore, according to this characteristic, different weights can be assigned to different parts of each transition section, so that the weight of the part with a larger voltage difference between two adjacent steps is higher than the weight of the part with a smaller voltage difference between two adjacent steps. When there are two groups of coils in a certain interval and there is a transition section, the two groups of coils are used to calculate the measurement rod position separately, and the measurement rod position judged by the coil with a higher weight can be trusted.

[0075] In particular, in order to improve the applicability and error prevention of rod position measurement, different thresholds are used for interval division and transition segment division. Therefore, there is a situation where the interval division and the transition segment are inconsistent, that is, the transition segment is divided into two adjacent control rod travel intervals by the interval division. In order to avoid measurement errors caused by this, the rod position can be judged separately for the transition segments of the two intervals, and the rod position closer to the rod position Gray code shall prevail.

[0076] In summary, this embodiment realizes rod position measurement with one-step resolution and ±1-step accuracy through the above process, thereby achieving the purpose of improving the resolution and accuracy of rod position measurement.

[0077] Example 2

[0078] This embodiment provides a practical application case based on the technical solution of Embodiment 1.

[0079] Refer to Table 1, which is a table of the corresponding relationship between coil voltage and rod position collected after actual measurement. This table is the corresponding relationship between each step of the control rod position collected within the full stroke range and the typical value of each group of coil output voltage, as well as the voltage difference between two adjacent steps and the voltage upper and lower limit boundary values ​​calculated based on this, where the boundary value is the average value of the voltage of the two adjacent steps.

[0080] Table 1 Correspondence between coil voltage and rod position

[0081]

[0082]

[0083]

[0084]

[0085]

[0086]

[0087] Refer to Table 2, which shows the setting thresholds for the high-voltage and low-voltage sections of each coil group after an actual complete control rod stroke test.

[0088] Table 2: Setting thresholds for high-voltage and low-voltage sections of each coil group

[0089]

[0090] This table sets the thresholds for the high-voltage and low-voltage sections of each coil, which are the upper and lower limits and the theoretical switching positions of the high-voltage and low-voltage sections. When the coil output is lower than the corresponding lower limit, the output logic is 0, indicating that it is in the low-voltage section. When the coil output is higher than the corresponding upper limit, the output logic is 1, indicating that it is in the high-voltage section. When the coil output is between the upper and lower limits, the output remains unchanged at the previous moment.

[0091] The E coil group has only one set of thresholds, which can be used directly. The D coil group has two sets of thresholds. The specific set to be used depends on the logic output of the E coil group. When the E coil group outputs logic 0, the first set of thresholds is used. When the E coil group outputs logic 1, the second set of thresholds is used. And so on. The thresholds used by the C, B, and A coil groups are determined by their predecessor coil outputs or output combinations.

[0092] Refer to Table 3, which shows the actual measurement accuracy data using the method of this embodiment. From the table, it can be found that the measurement resolution reaches 1 step, the maximum measurement error is ±1 step, and in fact, the measurement error of most positions is 0.

[0093] Table 3 Actual measurement accuracy data

[0094]

[0095]

[0096] The actual measurement method can be as follows:

[0097] The method divides each group of coils into high-voltage section, low-voltage section and transition section within the full stroke range of the control rod, and divides the rod position operation interval on this basis. The method uses the characteristic that there is a unique corresponding relationship between the output voltage of at least one group of coils in the transition section of each interval and the rod position in the interval to perform rod position determination with one-step resolution. The rod position measurement accuracy is further improved by applying a weighted algorithm to the transition section and determining the transition sections of adjacent intervals and taking the better value. Finally, the rod position measurement with one-step resolution and ±1-step accuracy is achieved, which greatly improves the resolution and accuracy of the rod position measurement.

[0098] First, the output voltage of each group of coils of the rod position detector corresponding to each step in the full stroke of the control rod is collected, and the applicable voltage range of this step and the threshold for dividing the control rod stroke interval are calculated based on the collected coil output voltage. In this way, the thresholds required for rod position measurement are obtained.

[0099] The rod position measurement process based on this embodiment is as follows:

[0100] First, the output voltage of each group of coils of the detector is collected;

[0101] Compare the voltage of the coil group E with its interval division threshold. When the coil voltage is higher than the high threshold, the output is logic 1 (indicating that the control rod is in the upper half of the travel interval). When the coil voltage is lower than the low threshold, the output is logic 0 (indicating that the control rod is in the lower half of the travel interval). When the coil voltage is between the high threshold and the low threshold, the output remains unchanged at the previous moment.

[0102] According to the output of the E group coil group, the threshold value of the D group coil group in the corresponding interval is used to divide the rod position operation interval of the D group coil group;

[0103] Similarly, according to the output combination of the coil group E and the coil group D, the threshold value of the coil group C in the corresponding interval is used to divide the rod position operation interval of the coil group C; according to the output combination of the coil group E, the coil group D and the coil group C, the threshold value of the coil group B in the corresponding interval is used to divide the rod position operation interval of the coil group B; according to the output combination of the coil group E, the coil group D, the coil group C and the coil group B, the threshold value of the coil group A in the corresponding interval is used to divide the rod position operation interval of the coil group A;

[0104] Thus, the applicable coils and coil transition sections are determined. Taking the output result of each group of coils divided by the aforementioned interval as EDCBA=10101, it means that the control rod is in the 25th section of the full stroke (the corresponding control rod position interval is 192 steps to 197 steps). This interval is the transition section between the monotonically increasing group B coil group and the monotonically increasing group A coil group.

[0105] Correspondingly, the output voltages of coil group A and coil group B are compared with the voltage thresholds of the two coil groups between steps 192 and 197 for compliance;

[0106] In the example, at a certain moment, the voltage collected by the coil group A is 0.761, and the voltage collected by the coil group B is 0.172, both of which are within the transition voltage range, and fall within the 195-step threshold voltage upper and lower limit intervals of the coil group A and the 194-step threshold voltage upper and lower limit intervals of the coil group B, respectively. However, the corresponding threshold interval upper and lower limit difference of the coil group A is 0.013, and that of the coil group B is 0.056. According to the design of this scheme, the weight of the coil group B is greater because the difference is larger, so the rod position judgment result of the coil group B is adopted;

[0107] At a certain moment, the voltage collected by the coil group A is 0.652, and the voltage collected by the coil group B is 0.065. Only the voltage of the coil group A is within the transition section voltage range. Therefore, only the coil group A is used for single-step rod position judgment. However, at this time, the voltage of the coil group A does not fall within the range of 192 to 197 steps of the control rod position interval corresponding to the EDCBA output 10101, but falls within the range of 186 to 191 steps of the control rod position interval corresponding to the adjacent EDCBA output 10100. Therefore, the result of judgment in the two adjacent intervals is that the threshold of the coil group A in the 24th interval coincides with the 190-step threshold, and there is no corresponding matching threshold in the 25th interval. The difference in the threshold range corresponding to the coil group A at 190 steps is 0.041, which has a large weight and is trusted. Therefore, the judgment result is that the interval division is incorrect due to output signal fluctuations and measurement errors. The 190-step judgment result of the adjacent interval is trusted. Therefore, the rod position is judged to be 190 steps at this moment.

[0108] The determination of the control rod position within the full stroke is similar to this, thus obtaining the control rod position within the full stroke range. The control rod position obtained by this method is highly consistent with the actual rod position, with only a few steps with a measurement error of ±1 step. This method achieves a resolution of 1 step and a measurement error of ±1 step.

[0109] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for measuring the position of a control rod of a nuclear power plant reactor, characterized in that: The coded rod position detector includes 5 coil groups, including coil group A, coil group B, coil group C, coil group D and coil group E. The 5 coil groups are provided with a plurality of coils, which are numbered 0-m in sequence from bottom to top, and the coil with the largest number and the coil with number 0 are connected in series as auxiliary coils; among the coils other than the auxiliary coils, coil group A includes all coils numbered with odd numbers, coil group B includes coils numbered 4*i+2; coil group C includes coils numbered 8*j+4; coil group D includes coils numbered 16*p+8; coil group E includes coils numbered 32*q+16, and i, j, p and q are all integers not less than 0; the following steps are included: At least one set of threshold value groups is set for each coil group, the number of threshold value groups for each coil group is the same as the number of change bands corresponding to the position of the coil group, each set of threshold value groups includes multiple threshold points, and the value of the threshold point of each coil group is different; Rod position detection is performed based on the coded rod position detector and the threshold group.

2. A method for measuring the position of control rods in a nuclear power plant reactor according to claim 1, characterized in that: Each set of the thresholds includes a first high-pressure threshold point, a second high-pressure threshold point, a first low-pressure threshold point, and a second low-pressure threshold point; The first high pressure threshold point>the second high pressure threshold point>the second low pressure threshold point>the first low pressure threshold point.

3. A method for measuring the position of control rods in a nuclear power plant reactor according to claim 1, characterized in that: The E group coil group is provided with an E group threshold group, and the E group threshold group divides the voltage output of the E group coil group into an E group low voltage section, an E group transition section and an E group high voltage section; The E group of coils divides the entire control rod travel into two equal parts through different high-pressure sections and low-pressure sections.

4. A method for measuring the position of control rods in a nuclear power plant reactor according to claim 3, characterized in that: A D group threshold group is set for the D group coil group; the D group threshold group divides the voltage output of each coil of the D group coil group into a D group low voltage section, a D group transition section and a D group high voltage section; The E coil group and the D coil group divide the entire control rod stroke into four equal parts through different high-pressure sections and low-pressure sections.

5. A method for measuring the position of control rods in a nuclear power plant reactor according to claim 4, characterized in that: A C group threshold group is set for the C group coil group; the C group threshold group divides the voltage output of each coil of the C group coil group into a C group low voltage section, a C group transition section and a C group high voltage section; The C coil group, the E coil group and the D coil group divide the entire control rod stroke into 8 equal parts.

6. A method for measuring the position of control rods in a nuclear power plant reactor according to claim 5, characterized in that: A group B threshold group is set for the group B coil group; the group B threshold group divides the voltage output of each coil of the group B coil group into a group B low voltage section, a group B transition section and a group B high voltage section; The B coil group, the C coil group, the E coil group and the D coil group divide the entire control rod stroke into 16 equal parts through different high-pressure sections and low-pressure sections.

7. A method for measuring the position of control rods in a nuclear power plant reactor according to claim 6, characterized in that: A group A threshold group is set for the group A coil group; the group A threshold group divides the voltage output of each coil of the group A coil group into a group A low voltage section, a group A transition section and a group A high voltage section.

8. A method for measuring the position of control rods in a nuclear power plant reactor according to claim 7, characterized in that: The method for performing rod position detection based on the coded rod position detector and the threshold group is: judging the current control rod position interval according to the combination of the high voltage segment and the low voltage segment of the voltage output of each coil; There is at least one corresponding transition section of the coil in any interval. The voltage output of each coil is compared with the single-step threshold of the coil in the corresponding transition section. If the voltage output of a certain coil is within the upper and lower intervals of a certain single-step threshold, the control rod position corresponding to the single-step threshold is the measurement rod position. The single-step threshold is obtained through actual measurement.

9. A method for measuring the position of control rods in a nuclear power plant reactor according to claim 8, characterized in that: The method for obtaining the single-step threshold is: gradually obtaining the corresponding relationship between the voltage output of each coil in the entire stroke of the control rod and the position of the control rod at each step through actual measurement; The voltage output of each coil corresponding to the position of the control rod in each step is used as a typical value of the voltage output of each coil in this step; For each step of the position of the control rod, the average value of the voltage output typical value of the step and the typical values ​​of the voltage output of the two adjacent steps before and after the step is taken as the voltage output boundary value of the corresponding coil of the step, and then the corresponding interval of the voltage output of each coil at each step of the control rod position is obtained, and the corresponding interval is used as the single-step threshold.

10. A method for measuring the position of control rods in a nuclear power plant reactor according to claim 8, characterized in that: The greater the voltage output difference between two adjacent steps, the greater the weight of the coil; For a certain interval, if there are multiple coils with transition sections, the measuring rod position determined by the coil with a higher weight is adopted.

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