A method for measuring the position of control rods in a nuclear power plant reactor

Abstract

The present invention provides a method for measuring the position of reactor control rods in a nuclear power plant, relating to the technical field of reactor control rod position measurement. The method aims to improve the measurement accuracy of reactor control rod position measurement, comprising the following steps: providing at least one threshold value set for each coil assembly, wherein the number of threshold value sets for each coil assembly is equal to the number of variable bands corresponding to the coil assembly position, each threshold value set including multiple threshold points, each having different threshold value values ​​for each coil assembly; and performing rod position detection based on the encoded rod position detector and the threshold value sets. The present invention has the advantages of higher measurement accuracy and 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] Nuclear power plant reactors generally use coded rod position detectors designed based on the differential transformer principle. The electrical components of this type of detector consist of a primary coil for excitation and a secondary coil for output based on electromagnetic induction. The secondary coil is further divided into an auxiliary coil and a measuring coil.

[0003] The traditional rod position measurement method sets a threshold for each coil group. 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 coil group. 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 measuring rod position resolution of this measurement method depends on the spacing of the measuring coils. For example, if the spacing between adjacent coils is 8 steps, the measuring rod position resolution is 8 steps. Consequently, the theoretical optimal measurement accuracy is only ±4 steps. Taking into account measurement errors and signal processing errors, the highest achievable accuracy is generally ±6 steps. This indicates that the existing measurement method has low accuracy.

[0004] Therefore, it is necessary to improve the reactor control rod position measurement method to 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 in a nuclear power plant reactor, which can improve measurement accuracy.

[0006] The embodiments of the present invention are achieved through the following technical solutions:

[0007] A method for measuring the position of control rods in a nuclear power plant reactor. The encoded rod position detector includes five coil groups, including coil group A, coil group B, coil group C, coil group D, and coil group E. The five coil groups are provided with a total of multiple coils, and the coils are numbered 0-m in sequence from bottom to top. The coil with the largest number and the coil numbered 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; and coil group E includes coils numbered 32*q+16, where i, j, p, and q are all integers not less than 0. The method comprises the following steps:

[0008] At least one threshold value group 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 threshold value group includes multiple threshold points, and the threshold value of each coil group is different;

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

[0010] Preferably, each set of 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 group coil assembly and the D group coil assembly 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 eight 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 group coil group, the C group coil group, the E group coil group and the D group 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 detecting the rod position based on the coded rod position detector and the threshold value group is: judging the current range of the control rod according to the combination of the high voltage segment and the low voltage segment of the voltage output of each coil;

[0023] 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 ranges 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.

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

[0025] gradually obtaining, through actual measurement, a correspondence between the voltage output of each coil within the entire stroke of the control rod and the position of the control rod at each step;

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

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

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

[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 solutions of the embodiments of the present invention have at least the following advantages and beneficial effects:

[0031] The present invention divides the control rod position operation range by dividing each group of coils into high-voltage, low-voltage, and transition sections within the full range of the control rod stroke. By utilizing the fact that the output voltage of at least one group of coils in the transition section of each section has a unique correspondence with the rod position within that section, the rod position is determined with one-step resolution, thereby improving measurement accuracy.

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

[0033] The present invention is easy to implement, does not require modification of existing rod position detectors, 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 This is 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 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] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only 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 herein 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 in a nuclear power plant reactor. For an example of a coding rod position detector, refer to Figure 1The coded rod position detector includes five 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 five coil groups are provided with a total of multiple coils, which are numbered 0-m in sequence from bottom to top, and the coil with the largest number and the coil numbered 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; and 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, also known as the five coil groups mentioned above, are evenly spaced from the bottom of the detector to the top, spaced at regular intervals (e.g., 8 mechanical steps, or 127mm). Specifically, coils within a group are connected in anti-phase series, head-to-tail, with the final ends connected. The output of each measurement coil group exhibits a regular pattern of high and low fluctuations depending on the position of the control rod. Specifically, when the control rod drive rod is positioned in a coil group with an even number of coils (e.g., 0, 2, 4, ...), the output voltage of that coil group is higher; when the control rod drive rod is positioned in a coil group with an odd number of coils (e.g., 1, 3, 5, ...), the output voltage of that coil group is lower.

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

[0041] At least one threshold value group 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 threshold value group includes multiple threshold points, and the threshold value of each coil group is different;

[0042] Rod position detection is performed based on the coded rod position detector and the threshold value 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 the figure. According to the above-mentioned variation characteristics of the measuring coils, the output of each group of coils is divided into low voltage section, high voltage section and 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 maintains a stable 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 maintains a stable high 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 segments is achieved by setting a voltage threshold, which 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 segment; when the coil output is lower than the low-voltage threshold, it is considered to be in the low-voltage segment; and when the coil output is between the high-voltage threshold and the low-voltage threshold, it is considered to be in the transition segment. However, when actually measuring the rod position, in order to simultaneously meet the requirements of improving the applicability of the rod position measurement (achieved by increasing the transition segment, requiring the threshold to be closer to the high- and low-voltage boundaries of the coil output, and the high- and low-voltage thresholds to be larger) and error prevention (achieved by increasing the high- and low-voltage segments, requiring the threshold to be farther from the high- and low-voltage boundaries of the coil output, and the high- and low-voltage thresholds to be smaller), there may be overlapping areas between the three output segments, that is, the high-voltage segment and the low-voltage segment overlap with the transition segment 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 above the first high-voltage threshold, it is considered to be in the high-voltage segment. When the coil output is below the first low-voltage threshold, it is considered to be in the low-voltage segment. When the coil output is between the second high-voltage threshold and the second low-voltage threshold, it is considered to be in the transition segment. Therefore, there is an overlap between the transition segment and the high-voltage segment, and between the transition segment and the low-voltage segment. This increases the transition segment area, which is primarily used to determine control rod position, thus improving the applicability of rod position measurement. The high-voltage and low-voltage segment areas are also increased, primarily for interval demarcation. This avoids incorrect interval demarcation caused by setting the high and low voltage thresholds too close to the boundaries, thus improving error prevention.

[0050] When actually measuring the rod position, for a coil group with multiple transition sections, the outputs of different transition sections may be inconsistent. Therefore, to further improve the accuracy of segmentation and the rod position measurement, 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 group coil assembly and the D group coil assembly 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 eight 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 group coil group, the C group coil group, the E group coil group and the D group 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 low-pressure section of the coil group A are not obvious, and there is no need to use the high-pressure section and low-pressure section to divide the control rod travel interval. Therefore, whether to set the high-pressure section and low-pressure section can be determined based on the actual output characteristics. If the division of the high-pressure section and low-pressure section is not performed, it is only necessary to divide the coil group A into corresponding 16 transition sections based on the 16 intervals determined by the coil groups E, D, C, and B.

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

[0062] Based on the above configuration, the method for detecting the rod position based on the coded rod position detector and the threshold value group is preferably as follows: determining the current control rod position interval based on the combination of the high voltage segment and the low voltage segment of the voltage output of each coil;

[0063] In any interval, there is at least one corresponding transition segment of the coil. The voltage output of each coil is compared with the single-step threshold of the coil within the corresponding transition segment. If the voltage output of a coil is within the upper or lower range 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. This achieves rod position measurement with a resolution of one step.

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

[0065] The corresponding relationship between the voltage output of each coil and the position of the control rod at each step within the entire stroke of the control rod 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 entire stroke, and the output voltage of each coil corresponding to the position of the control rod at each step is recorded. Figure 3 This diagram shows the voltage output characteristics of each coil group during the process of raising a control rod from bottom to top. The diagram shows the voltage output changes of each coil group during the full lifting process of the control rod, with the curves representing coil groups E, D, C, B, and A from top to bottom. As can be seen from the diagram, by comparing each coil voltage with a threshold, the entire control rod travel can be divided into different intervals. Within any interval, there is a situation where a coil's voltage changes monotonically with rod position, either increasing or decreasing (i.e., the coil output has a unique correspondence with control rod position). Taking coil group D as an example, the transition section (circled) exhibits the following characteristics:

[0066] The circle is the transition section of coil group D. The coil voltage at this section increases monotonically with the rod position and has a clear 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 insignificant.

[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 interval respectively, and the result closer to the interval division can be taken as the measured rod position.

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

[0070] For each step of the control rod position, the average of the typical voltage output value for that step and the typical voltage output values ​​for the two steps preceding and following it is taken as the voltage output boundary value for the coil corresponding to that step. This then yields the corresponding range of voltage outputs for each coil at each control rod position step. This corresponding range serves as the single-step threshold. It should be noted that the first low-voltage threshold, first high-voltage threshold, second low-voltage threshold, and second high-voltage threshold for each coil and each range can be set based on the actual detector output.

[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, based on the coil output characteristics, there is at least one corresponding coil transition segment in any interval. In particular, at certain control rod positions, there are two coil transition segments simultaneously. In this case, it is necessary to comprehensively analyze the output characteristics of the two transition segments to determine the rod position, for example, taking the average 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 rod position separately, and the rod position judgment of the coil with a higher weight can be trusted.

[0075] In particular, 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 transition segment are inconsistent, that is, the transition segment is divided into two adjacent control rod travel intervals by the interval division. 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 is used as the standard.

[0076] In summary, this embodiment achieves 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 shows the relationship between coil voltage and rod position, collected after actual measurement. This table shows the relationship between each control rod position within the full range of control, and the typical output voltage values ​​of each coil group. It also includes the calculated voltage difference between two adjacent steps and the upper and lower voltage limits. The limit value here is the average of the two adjacent step voltages.

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

[0081]

[0082]

[0083]

[0084]

[0085]

[0086]

[0087] Refer to Table 2, which shows the threshold values ​​for dividing 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 lists the thresholds for high- and low-voltage segments for each coil, including upper and lower limits and the theoretical switching positions for the high- and low-voltage segments. When the coil output is below the corresponding lower limit, the output is a logic 0, indicating the low-voltage segment. When the coil output is above the corresponding upper limit, the output is a logic 1, indicating the high-voltage segment. When the coil output is between the upper and lower limits, the output remains unchanged from the previous moment.

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

[0092] Refer to Table 3, which shows the actual measurement accuracy data using the method of this embodiment. From the table, it can be seen 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] This 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. 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 is determined with one-step resolution. By applying a weighted algorithm to the transition section and determining the transition sections of adjacent intervals and taking the better value, the rod position measurement accuracy is further improved. 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 set of coils in the rod position detector is collected for each step of the control rod's full travel. Based on the collected coil output voltages, the applicable voltage range for that step and the thresholds for dividing the control rod's travel intervals are calculated. This results in the various sets of thresholds required for rod position measurement.

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

[0100] First, collect the output voltage of each coil group of the detector;

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

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

[0103] Similarly, based on the output combination of the coil groups E and 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; based on the output combination of the coil groups E, D, and 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; based on the output combination of the coil groups E, D, C, and 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] The applicable coils and coil transition sections are thus determined. For example, the output result of each coil group divided by the aforementioned interval, EDCBA = 10101, indicates that the control rod is in the 25th section of the full stroke (corresponding to the control rod position interval of steps 192 to 197). This interval is the transition section between the monotonically increasing coil group B and the monotonically increasing coil group A.

[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;

[0106] In this example, at a certain moment, the voltage collected by coil group A is 0.761, and the voltage collected by 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 limits of coil group A and the 194-step threshold voltage upper and lower limits of coil group B, respectively. However, the corresponding threshold interval upper and lower limits of coil group A are 0.013, and that of coil group B is 0.056. According to this design scheme, the larger the difference, the greater the weight, so the coil group B has a higher weight. Therefore, the rod position judgment result of coil group B is adopted;

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

[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 having 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 merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for measuring the position of control rods in a nuclear power plant reactor, characterized in that: The coded rod position detector includes five 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 five coil groups are provided with a total of multiple coils, and the coils are numbered 0-m in sequence from bottom to top. The coil with the largest number and the coil numbered 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; and the following steps are included: At least one threshold value group 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 threshold value group includes multiple threshold points, and the threshold value of each coil group is different; Performing rod position detection based on the coded rod position detector and the threshold value group; The method for detecting the rod position based on the coded rod position detector and the threshold value group is as follows: 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; 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 ranges 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. The method for obtaining the single-step threshold is: gradually obtaining, through actual measurement, a correspondence between the voltage output of each coil within the entire stroke of the control rod and the position of the control rod at each step; The voltage output of each coil corresponding to the position of the control rod at each step is used as a typical value of the voltage output of each coil at that step; For each step of the control rod position, the average value of the voltage output typical value of that step and the typical values ​​of the voltage outputs of the two adjacent steps before and after it is taken as the voltage output boundary value of the coil corresponding to that step, thereby obtaining the corresponding interval of the voltage output of each coil at each step of the control rod position, and the corresponding interval is used as the single-step threshold.

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 said 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; 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. The method for measuring the position of control rods in a nuclear power plant reactor according to claim 1, wherein: 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 group coil assembly and the D group coil assembly 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 eight 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. The method for measuring the position of control rods in a nuclear power plant reactor according to claim 1, wherein: 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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