Method for improving reliability of reactor over-temperature and over-power delta T protection
By introducing axial power deviation calculations for four power range channels in the reactor and switching to other channels in case of channel failure or abnormality, the problem of reactor over-temperature and over-power protection logic being easily affected is solved, thus improving the stability and economy of the unit.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CNNC FUJIAN FUQING NUCLEAR POWER
- Filing Date
- 2024-11-21
- Publication Date
- 2026-06-09
AI Technical Summary
In existing technologies, reactor over-temperature and over-power protection logic is susceptible to abnormalities or malfunctions in external nuclear monitoring system channels, leading to unnecessary reactor shutdowns and threatening unit stability and economic efficiency.
The axial power deviation of the four power range channels is incorporated into the over-temperature and over-power logic calculation. When one channel fails or malfunctions, it automatically or manually switches to other channels to participate in the calculation, ensuring that each loop selects a different channel and performs signal correction when necessary, thus avoiding the introduction of higher reactor shutdown risks.
It improves the reliability of reactor over-temperature and over-power protection, reduces unnecessary reactor shutdowns, and enhances the stability and economy of the unit.
Smart Images
Figure CN119673493B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of reactor protection technology, and in particular to a method for improving the reliability of reactor over-temperature and over-power ΔT protection. Background Technology
[0002] Over-temperature and over-power (ΔT) protection is a commonly used emergency shutdown protection logic in pressurized water reactors. Currently, 1000MW pressurized water reactors typically have three coolant circulation loops. The over-temperature and over-power protection logic uses the average coolant temperature, pressurizer pressure, main pump speed, and axial power deviation of the power range closest to that loop as input signals for each coolant circulation loop. Each loop independently performs over-temperature and over-power calculations and comparisons, generating its own over-temperature and over-power signal. The over-temperature and over-power signals from the three loops are then used in a 2-out-of-3 logic to generate the final shutdown signal.
[0003] The off-core nuclear measurement system has four detectors for power range measurement. Axial power deviation signals generated by channels one, two, and three are used for over-temperature and over-power protection. When a power range channel generates a test or fault signal, the over-temperature and over-power protection logic degrades to a two-out-of-one approach. Alternatively, if a fault in the equipment causes the axial power deviation to exceed a certain range, that channel generates a loop over-temperature and over-power signal. In this case, the final over-temperature and over-power signal is actually determined by the other two loops through a two-out-of-one logic.
[0004] As the units are operational, multiple units at multiple power plants have experienced flickering fluctuations in axial power deviation signals or flickering channel fault alarms caused by abnormalities in the external nuclear measurement system channels. Since the external nuclear measurement system requires periodic testing according to the periodic test supervision outline, during the testing, the tested channel triggers a test signal. As mentioned above, the over-temperature and over-power protection systems trigger logic degradation. If, at this time, the other two power range channels involved in the calculation experience channel faults or axial power deviation fluctuations exceeding a certain range, it will lead to a reactor shutdown, threatening the stable and economical operation of the unit. Because this type of shutdown is caused by a measurement equipment malfunction, rather than a protection signal generated by the actual operation of the reactor core, this situation should be avoided as much as possible. Summary of the Invention
[0005] The technical problem this invention aims to solve is to provide a method for improving the reliability of reactor over-temperature and over-power ΔT protection by incorporating the axial power deviation of the four power range channels into the over-temperature and over-power logic calculation. When an anomaly occurs in any channel of the power range, it will not introduce a higher risk of reactor shutdown into the over-temperature and over-power protection logic, thereby improving the stability and economy of the unit.
[0006] This invention provides a method for improving the reliability of reactor over-temperature and over-power ΔT protection, comprising the following steps: all four power range channels participate in the over-temperature and over-power protection logic calculation; when one power range channel fails or has an anomaly, it is disconnected; the over-temperature and over-power protection logic of each of the three loops selects a new power range channel from the remaining three power range channels without anomalies to participate in the calculation; the selection method is to select the nearest power range channel within a range of 90° clockwise or 90° counterclockwise from the loop itself, and to ensure that each loop selects a different power range channel.
[0007] In one specific implementation, when all four power range channels are normal, the first loop of over-temperature and over-power calculation is performed by the first power range channel, the second loop by the second power range channel, and the third loop by the third power range channel.
[0008] In one specific implementation, when a power range channel malfunctions or experiences an anomaly, the disconnection process is divided into four scenarios:
[0009] In the first scenario, when the fourth power range channel malfunctions or is abnormal, the participation of the first, second, and third power range channels in the calculation of over-temperature and over-power in the first, second, and third loops remains unchanged.
[0010] In the second scenario, when the first power range channel malfunctions or is abnormal, the power range channel involved in the first loop over-temperature and over-power calculation is automatically or manually switched to the fourth power range channel. At the same time as the switching, the axial power deviation signal of the four channels is corrected.
[0011] In the third scenario, when the second power range channel malfunctions or is abnormal, the power range channel involved in the second-ring over-temperature and over-power calculation will be automatically or manually switched to the fourth power range channel. At the same time as the switching, the axial power deviation signal of the four channels will be corrected.
[0012] In the fourth scenario, if the third channel of the power range malfunctions or is abnormal, the channel participating in the second-ring over-temperature and over-power calculation will be automatically or manually switched to the fourth channel of the power range. At the same time as the switch, the axial power deviation signal of the fourth channel of the power range will be corrected. The channel participating in the third-ring over-temperature and over-power calculation will be switched to the second channel of the power range. At the same time as the switch, the axial power deviation signal of the second channel of the power range will be corrected.
[0013] In one specific implementation, in the second, third, and fourth cases, when a fault occurs, the power range channel is switched automatically or manually; when there is no fault but the signal is abnormal, the range channel is switched manually.
[0014] In one specific implementation, when the power range channel detector reselected by the loop has an angle with the original detector position, the axial power deviation signal of the newly selected power range is corrected.
[0015] In one specific implementation, when a switch has already occurred due to a power range channel failure or abnormality, and one or more power range channels used by each loop fail again after the switch, the process is handled according to normal logic degradation, i.e., from two out of three to one out of two and then to triggering a shutdown signal.
[0016] In one specific embodiment, the arrangement structure of the power range channel is as follows:
[0017] Four power range channels are arranged around the pressure vessel, with the first power range channel and the second power range channel arranged opposite each other, and the third power range channel and the fourth power range channel arranged opposite each other.
[0018] Compared with existing technologies, this invention introduces the axial power deviation of the four power range channels into the over-temperature and over-power logic calculation. By selecting and cutting off the axial power deviation signals of the power range channels, the axial power deviation signals of all four power range channels can participate in the over-temperature and over-power protection logic calculation when necessary, while cutting off the faulty or untrusted channel. Therefore, when one power range is abnormal or faulty, it will not introduce a higher risk of reactor shutdown to the over-temperature and over-power protection logic, thereby improving the stability and economy of the unit. Attached Figure Description
[0019] Figure 1 A schematic diagram showing the arrangement of the coolant loop and power range channel detectors;
[0020] In the diagram, 1-pressure vessel; 2-power range channel 1; 3-power range channel 3; 4-power range channel 2; 5-power range channel 4; 6-second ring coolant inlet; 7-second ring coolant outlet; 8-third ring coolant inlet; 9-third ring coolant outlet; 10-first ring coolant inlet; 11-first ring coolant outlet. Detailed Implementation
[0021] To further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the present invention.
[0022] This invention discloses a method for improving the reliability of reactor over-temperature and over-power ΔT protection. All four power range channels can participate in the over-temperature and over-power protection logic calculation. When a power range channel experiences a fault, a test signal, or an abnormality in the channel signal, the protection system automatically or manually reselects the power range channel participating in each loop's over-temperature and over-power protection logic. The axial power deviation signal is appropriately corrected based on the angle change between the new and original channels.
[0023] The method to reselect the channel is:
[0024] 1. Faulty or untrusted channels are switched (i.e., no longer selected by any of the three loops).
[0025] Second, ensure that the power range channels selected for each loop are different.
[0026] 3. Each loop should be selected from the nearest point within a 90° clockwise or 90° counterclockwise radius.
[0027] In short, any power range channel that is faulty or abnormal is disconnected. The three over-temperature and over-power loops each select a new power range channel from the remaining power range channels without abnormalities to participate in the calculation. The selection method is to select the nearest power range channel within a range of 90° clockwise or 90° counterclockwise from itself for each loop, and to ensure that each loop selects a different power range channel.
[0028] When all four power range channels are functioning normally, the first loop of over-temperature and over-power calculations is performed by the first power range channel, the second loop by the second power range channel, and the third loop by the third power range channel.
[0029] When a power range channel is faulty or malfunctioning, there are four scenarios when it is disconnected:
[0030] In the first scenario, when the fourth power range channel malfunctions or is abnormal, the participation of the first, second, and third power range channels in the calculation of over-temperature and over-power in the first, second, and third loops remains unchanged.
[0031] In the second scenario, when the first power range channel malfunctions or is abnormal, the power range channel involved in the over-temperature and over-power calculation of the first loop will be automatically or manually switched to the fourth power range channel. Since the angle between the detectors of the first loop and the fourth and first power range channels is different, the axial power deviation signal of the four channels will be corrected during the switching. The power range channels selected for the second and third loops remain unchanged.
[0032] In the third scenario, when the second power range channel malfunctions or is abnormal, the power range channel involved in the second-ring over-temperature and over-power calculation will be automatically or manually switched to the fourth power range channel. Since the angles between the second-ring and the fourth and second power range channels are different, the axial power deviation signal of the four channels will be corrected during the switching. The power range channels selected for the first and third rings will remain unchanged.
[0033] In the fourth scenario, if the third power range channel malfunctions or exhibits an anomaly, the channel participating in the second-ring over-temperature and over-power calculation will be automatically or manually switched to the fourth power range channel. Due to the different angles between the second-ring and the detectors of the fourth and second power range channels, the axial power deviation signal of the fourth power range channel will be corrected during the switching process. Similarly, the channel participating in the third-ring over-temperature and over-power calculation will be switched to the second power range channel. Due to the different angles between the third-ring and the detectors of the third and second power range channels, the axial power deviation signal of the second power range channel will be corrected during the switching process.
[0034] In case of a general fault, it can be operated automatically or manually; if there is no fault but the signal is abnormal, it can be operated manually.
[0035] If a switch has already occurred due to a power range channel failure or abnormality, and one or more power range channels used by each loop fail again after the switch, the process is handled according to normal logic degradation, i.e., from two out of three to one out of two and then to triggering a shutdown signal.
[0036] Figure 1 This is a schematic diagram of the coolant loop and power range channel detector arrangement for a certain pressurized water reactor model. The arrangement structure of the power range channel is as follows:
[0037] Four power range channels are arranged around the pressure vessel 1. The first power range channel 2 and the second power range channel 4 are arranged opposite each other, and the third power range channel 3 and the fourth power range channel 5 are arranged opposite each other.
[0038] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.
[0039] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for improving the reliability of reactor over-temperature and over-power ΔT protection, characterized in that, Includes the following steps: All four power range channels participate in the over-temperature and over-power protection logic calculation. When a power range channel fails or has an anomaly, it is disconnected. The over-temperature and over-power protection logic of each of the three loops selects a new power range channel from the remaining three power range channels without anomalies to participate in the calculation. The selection method is to select the nearest power range channel within a range of 90° clockwise or 90° counterclockwise from the loop itself, and to ensure that each loop selects a different power range channel. When all four power range channels are normal, the first loop of over-temperature and over-power calculation is performed by the first power range channel, the second loop by the second power range channel, and the third loop by the third power range channel. When a power range channel malfunctions or malfunctions, the disconnection process falls into four categories: In the first scenario, when the fourth power range channel malfunctions or is abnormal, the participation of the first, second, and third power range channels in the calculation of over-temperature and over-power in the first, second, and third loops remains unchanged. In the second scenario, when the first power range channel malfunctions or is abnormal, the power range channel involved in the first loop over-temperature and over-power calculation is automatically or manually switched to the fourth power range channel. At the same time as the switching, the axial power deviation signal of the four channels is corrected. In the third scenario, when the second power range channel malfunctions or is abnormal, the power range channel involved in the second-ring over-temperature and over-power calculation will be automatically or manually switched to the fourth power range channel. At the same time as the switching, the axial power deviation signal of the four channels will be corrected. In the fourth scenario, when the third channel of the power range malfunctions or is abnormal, the channel participating in the second-ring over-temperature and over-power calculation will be automatically or manually switched to the fourth channel of the power range. At the same time as the switch, the axial power deviation signal of the fourth channel of the power range will be corrected. The channel participating in the third-ring over-temperature and over-power calculation will be switched to the second channel of the power range. At the same time as the switch, the axial power deviation signal of the second channel of the power range will be corrected. In the second, third, and fourth scenarios, when a fault occurs, the power range channel is switched automatically or manually; when there is no fault but the signal is abnormal, the range channel is switched manually. When the newly selected power range channel detector has an angle with the original detector position, the axial power deviation signal of the newly selected power range is corrected. If a switch has already occurred due to a power range channel failure or abnormality, and one or more power range channels used by each loop fail again after the switch, the process is handled according to normal logic degradation, i.e., from two out of three to one out of two and then to triggering the shutdown signal. The arrangement structure of the power range channel is as follows: Four power range channels are arranged around the pressure vessel, with the first power range channel and the second power range channel arranged opposite each other, and the third power range channel and the fourth power range channel arranged opposite each other.