A method for automatically searching for the movement of control rods in the peak-shaving process of a pressurized water reactor

Abstract

The application discloses a method for automatically searching for the movement of a control rod in a peak-shaving process of a pressurized water reactor, and the method comprises the following steps: first, using a core physical analysis software to perform core burnup calculation to obtain core burnup distribution and poison atomic nucleus density distribution information; second, according to the peak-shaving demand of a power grid, determining and setting corresponding power levels, temperature regulation rod group rod position low-low limits, AO reference values and primary loop boron dilution speed limits at different time points of core operation; third, adjusting the control rod position according to the normal AO control requirement; fourth, performing critical boron concentration search and poison distribution calculation; fifth, judging the AO; and sixth, judging the primary loop boron dilution speed. The application is suitable for automatically searching for the movement of a control rod in a peak-shaving process of a commercial pressurized water reactor, can quickly obtain the movement of each control rod in the peak-shaving process, avoids the large amount of time spent in the calculation of the control rod by the traditional mode through experience and manual setting, and provides efficient and reliable technical support for the peak-shaving of the commercial pressurized water reactor.

Description

Technical Field

[0001] This invention relates to the field of commercial pressurized water reactor operation optimization technology, specifically to an automatic search method for control rod movement during the peak shaving process of a pressurized water reactor. Background Technology

[0002] With the increasing number of pressurized water reactor (PWR) nuclear power units in my country, the proportion of nuclear power in the overall power system will grow rapidly, facing high-frequency and high-amplitude grid peak-shaving requirements. Due to the inherent characteristics of nuclear power reactors, power increases and decreases pose safety risks to reactor control. To ensure the safe operation of nuclear power plants during reactor start-up, shutdown, and load adjustment, and to avoid reactive events, effective reactive management is necessary. Currently, after receiving peak-shaving requirements from the grid, PWR nuclear power plants first rely on engineers in the technical support department to manually set control rod positions at different times based on their personal experience to obtain targeted control rod movements. This approach often takes several hours, is highly dependent on expert experience, and is difficult to meet the high-frequency and high-amplitude demands of PWR nuclear power units. Summary of the Invention

[0003] To meet the urgent needs of my country's commercial pressurized water reactor (PWR) nuclear power plants for high-frequency, high-amplitude grid peak shaving in the future, this invention proposes an automatic search method for control rod movement during PWR peak shaving. Based on the core burnup distribution, toxic atom nucleus density distribution information calculated by the burnup module of the core physics analysis software, along with different power levels and durations, AO (axial power offset) reference values, and primary loop boron dilution rate limits, and in accordance with basic reactivity management requirements, the method automatically searches for control rod movement. This invention avoids the drawbacks of traditional methods that heavily rely on expert experience and are time-consuming, and can automatically and efficiently obtain the control rod position, thus meeting the significant high-frequency, high-amplitude requirements of PWR nuclear power units.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] An automatic search method for control rod movement during peak shaving in a pressurized water reactor (PWR) system can automatically search for control rod movement based on grid peak shaving requirements by setting different power levels and durations, AO reference values, and primary loop boron dilution rate limits. The method includes the following steps:

[0006] Step 1: Use core physics analysis software to calculate core burnup and obtain the core burnup distribution and poison nucleus density distribution information output by the core physics analysis software.

[0007] Step 2: Based on the grid peak-shaving requirements, determine and set the corresponding power level, temperature regulating rod position low limit, AO reference value, and primary loop boron dilution rate limit at different times of core operation.

[0008] Step 3: Adjust the position of the control rod according to the normal AO control requirements;

[0009] The insertion signal is triggered when a boron dilution rate exceeding the limit is received, or when no boron dilution rate exceeding the limit is received but the AO error is greater than zero. Under the conditions of the insertion signal triggering: if the temperature regulating rod group is above the low limit, the temperature regulating rod group is inserted first; if the temperature regulating rod group is at the low limit, the power compensation rod group is inserted.

[0010] If no signal of boron dilution rate exceeding the limit is received and the AO error is less than zero, the rod lifting signal is triggered. Under the triggering conditions of the rod lifting signal: if the power compensation rod group is in the insertion state, the power compensation rod group is lifted first; if the power compensation rod group is in the fully lifted state, the temperature regulating rod group is lifted.

[0011] During the adjustment of the control rod position, if the temperature regulating rod group or power compensation rod group reaches the upper or lower limit of insertion, the rod position is set according to the limit value; if the rod position of the temperature regulating rod group or power compensation rod group is the same as the previous rod position adjustment result, the rod position movement completion signal is triggered.

[0012] Step 4: Perform critical boron concentration search and toxicant distribution calculation;

[0013] Under the condition of adjusting the rod position, according to the power level and maintenance time of the core operation at the current time step, the critical boron concentration search and poison distribution calculation are performed using the core burnup distribution and poison nucleus density distribution information until the core effective multiplication factor converges iteratively.

[0014] Step 5: Determine the AO;

[0015] Given the current rod position, critical boron concentration, and toxicant distribution, the AO (Area of ​​Occurrence) is determined: if the two predefined AO determination criteria are not met, return to step 3 for rod position adjustment; if the two predefined AO determination criteria are met, proceed to the next step of determination calculation. The two AO determination criteria are expressed as follows:

[0016]

[0017]

[0018] —This represents the calculated value of the core AO at time step n;

[0019] AO ref —This means that the reactor core is required to operate according to the reference value given by actual measurement during the load adjustment phase;

[0020] Step 6: Determine the boron dilution rate in the primary loop;

[0021] Based on the dilution amount of the critical boron concentration in the current time step and the previous time step, the dilution rate in the current time step is calculated. Combined with the volume of the primary coolant, the water injection volume in the current time step is calculated. This is then compared with the set primary dilution rate limit to determine the boron dilution rate in the primary circuit.

[0022] If the dilution rate at the current time step meets the limit requirement, then return to step 2 to proceed to the calculation of the next time step; if the dilution rate at the current time step does not meet the limit requirement, then trigger the boron dilution rate over-limit signal and return to step 3 to perform rod position adjustment calculation. The criterion for determining the boron dilution rate of the primary loop is expressed as follows:

[0023] V RCV ·ln[BC / (BC-dBC)]≤V 注水 Formula (3)

[0024] V RCV —This indicates the volume of the primary coolant circuit;

[0025] BC represents the boron concentration;

[0026] V 注水 — Indicates the amount of water injected.

[0027] Preferably, the iteration convergence condition in step 4 is that the error of the effective core multiplication factor is less than 10. -5 .

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] This invention enables automatic search for control rod movement during peak shaving in commercial pressurized water reactors, avoiding the drawbacks of traditional methods that rely heavily on expert experience and are time-consuming. It can automatically and efficiently obtain the position of the control rod movement, meeting the critical requirements of high frequency and deep amplitude for pressurized water reactor nuclear power units. Attached Figure Description

[0030] Figure 1 This is a flowchart of the method of the present invention.

[0031] Figure 2 This is a power-time curve of the CO2 cycle small-scale peak shaving process of Unit 6 of Tianwan Nuclear Power Plant.

[0032] Figure 3 The calculated values ​​of the reactor core AO under automatically obtained control rod movement are compared with the measured values ​​of actual operation.

[0033] Figure 4 The calculated value of the temperature regulating rod group position under the automatically obtained control rod movement is compared with the measured value during actual operation. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0035] This invention discloses an automatic search method for control rod movement during peak shaving in a pressurized water reactor. Based on different power levels and durations calculated by the burnup module of core physics analysis software, AO reference values, and primary loop boron dilution rate limits, and in accordance with basic reactivity management requirements, the method automatically searches for control rod movement during peak shaving. Specific implementation steps are as follows: Figure 1 As shown, it includes the following steps:

[0036] Step 1: Use core physics analysis software to calculate core burnup and obtain the core burnup distribution and poison nucleus density distribution information output by the core physics analysis software.

[0037] In this embodiment, burnup is calculated based on power history to obtain the core burnup distribution and toxic nucleus density distribution information of Unit 6 of Tianwan Nuclear Power Plant before the small peak shaving of CO2 cycle.

[0038] Step 2: Based on the grid peak-shaving requirements, determine and set the corresponding power level, temperature regulating rod position low limit, AO reference value, and primary loop boron dilution rate limit at different times of core operation.

[0039] In this embodiment, the No. 6 unit of Tianwan Nuclear Power Plant slightly reduced the CO2 cycle peak on May 1st, from 1 MWe / min to 76% of full power, maintained at 76% of full power for a period of time, and then increased back to full power.

[0040] Step 3: Adjust the position of the control rod according to the normal AO control requirements;

[0041] When a boron dilution rate exceeding the limit signal is received, or when no boron dilution rate exceeding the limit signal is received but the AO error is greater than zero, the insertion signal is triggered. Under the conditions of the insertion signal triggering: if the temperature regulating rod group position is higher than the lower limit, the temperature regulating rod group is inserted first; if the temperature regulating rod group is at the lower limit, the power compensation rod group is inserted.

[0042] If no signal indicating that the boron dilution rate of the primary loop exceeds the limit is received and the AO error is less than zero, a rod lifting signal is triggered. Under the triggering conditions of the rod lifting signal: if the power compensation rod group is in the insertion state, the power compensation rod group is lifted first; if the power compensation rod group is in the fully lifted state, the temperature regulating rod group is lifted.

[0043] During the adjustment of the control rod position, if the temperature regulating rod group or power compensation rod group reaches the upper or lower limit of insertion, the rod position is set according to the limit value; if the rod position of the temperature regulating rod group or power compensation rod group is the same as the previous rod position adjustment result, the rod position movement completion signal is triggered.

[0044] Step 4: Perform critical boron concentration search and toxicant distribution calculation;

[0045] Under adjusted rod positions, based on the current core operating power level and sustainment time at the current time step, critical boron concentration search and poison distribution calculations are performed using core burnup distribution and poison nucleus density distribution information until the error of the core effective multiplication factor is less than 10. -5 until;

[0046] Step 5: Determine the AO;

[0047] Given the current rod position, critical boron concentration, and toxicant distribution, the AO (Anaerobic Oxidation) is determined: if the two predefined AO determination criteria are not met, return to step 3 for rod position adjustment; if the two predefined AO determination criteria are met, proceed to the next step of determination calculation. The two AO determination criteria are expressed as follows:

[0048]

[0049]

[0050] —This represents the calculated value of the core AO at time step n;

[0051] AO ref —This means that the reactor core is required to operate according to the reference value given by actual measurement during the load adjustment phase;

[0052] Step 6: Determine the boron dilution rate in the primary loop;

[0053] Based on the dilution amount of the critical boron concentration in the current time step and the previous time step, the dilution rate in the current time step is calculated. Combined with the volume of the primary coolant, the water injection volume in the current time step is calculated. This is then compared with the set primary dilution rate limit to determine the boron dilution rate in the primary circuit.

[0054] If the dilution rate at the current time step meets the limit requirement, then return to step 2 to proceed to the calculation of the next time step; if the dilution rate at the current time step does not meet the limit requirement, then trigger the boron dilution rate over-limit signal and return to step 3 to perform rod position adjustment calculation. The criterion for determining the boron dilution rate of the primary loop is expressed as follows:

[0055] V RCV ·ln[BC / (BC-dBC)]≤V 注水 Formula (3)

[0056] V RCV —This indicates the volume of the primary coolant circuit;

[0057] BC represents the boron concentration;

[0058] V 注水 —Indicates the amount of water injected;

[0059] Figure 3 Compare the calculated values ​​of core AO under automatically obtained control rod movement with the measured values ​​of actual operation; Figure 4 The calculated values ​​of the temperature regulating rod group positions under automatically obtained control rod movement are compared with the measured values ​​from actual operation. In the industrial verification of pressurized water reactor nuclear power plants, the error limit for core AO is 2%, and the error limit for control rod group positions is within 4 steps. In this embodiment, the control rod movement automatically obtained for Unit 6 of Tianwan Nuclear Power Plant during the small-scale peak shaving on May 1st of the CO2 cycle meets the industrial limit requirements.

Claims

1. An automatic search method for control rod movement in a pressurized water reactor peak shaving process, characterized in that: The system can automatically search for control rod movement based on the grid's peak-shaving requirements by setting different power levels, durations, AO reference values, and primary loop boron dilution rate limits. This includes the following steps: Step 1: Use core physics analysis software to calculate core burnup and obtain the core burnup distribution and poison nucleus density distribution information output by the core physics analysis software. Step 2: Based on the grid peak-shaving requirements, determine and set the corresponding power level, temperature regulating rod position low limit, AO reference value, and primary loop boron dilution rate limit at different times of core operation. Step 3: Adjust the position of the control rod according to the normal AO control requirements; The insertion signal is triggered when a boron dilution rate exceeding the limit is received, or when no boron dilution rate exceeding the limit is received but the AO error is greater than zero. Under the conditions of the insertion signal triggering: if the temperature regulating rod group is above the low limit, the temperature regulating rod group is inserted first; if the temperature regulating rod group is at the low limit, the power compensation rod group is inserted. If no signal of boron dilution rate exceeding the limit is received and the AO error is less than zero, the rod lifting signal is triggered. Under the triggering conditions of the rod lifting signal: if the power compensation rod group is in the insertion state, the power compensation rod group is lifted first; if the power compensation rod group is in the fully lifted state, the temperature regulating rod group is lifted. During the adjustment of the control rod position, if the temperature regulating rod group or power compensation rod group reaches the upper or lower limit of insertion, the rod position is set according to the limit value; if the rod position of the temperature regulating rod group or power compensation rod group is the same as the previous rod position adjustment result, the rod position movement completion signal is triggered. Step 4: Perform critical boron concentration search and toxicant distribution calculation; Under the condition of adjusting the rod position, according to the power level and maintenance time of the core operation at the current time step, the critical boron concentration search and poison distribution calculation are performed using the core burnup distribution and poison nucleus density distribution information until the core effective multiplication factor converges iteratively. Step 5: Determine the AO; Given the current rod position, critical boron concentration, and toxicant distribution, the AO (Area of ​​Occurrence) is determined: if the two predefined AO determination criteria are not met, return to step 3 for rod position adjustment; if the two predefined AO determination criteria are met, proceed to the next step of determination calculation. The two AO determination criteria are expressed as follows: —This represents the calculated value of the core AO at time step n; AO ref —This means that, based on the reference value given by actual measurements, the reactor core is required to operate according to this reference value during the load adjustment phase; Step 6: Determine the boron dilution rate in the primary loop; Based on the dilution amount of the critical boron concentration in the current time step and the previous time step, the dilution rate in the current time step is calculated. Combined with the volume of the primary coolant, the water injection volume in the current time step is calculated. This is then compared with the set primary dilution rate limit to determine the boron dilution rate in the primary circuit. If the dilution rate at the current time step meets the limit requirement, then return to step 2 to proceed to the calculation of the next time step; if the dilution rate at the current time step does not meet the limit requirement, then trigger the boron dilution rate over-limit signal and return to step 3 to perform rod position adjustment calculation. The criterion for determining the boron dilution rate of the primary loop is expressed as follows: V RCV ·ln[BC / (BC-dBC)]≤V 注水 Formula (3) V RCV —This indicates the volume of the primary coolant circuit; BC represents the boron concentration; V 注水 — Indicates the amount of water injected.

2. The automatic search method for control rod movement in a pressurized water reactor peak shaving process according to claim 1, characterized in that: During the power grid peak shaving and power increase / decrease process, it can meet the requirements of constant AO control by automatically searching for the movement of each control rod of the pressurized water reactor.

3. The automatic search method for control rod movement in a pressurized water reactor peak shaving process according to claim 1, characterized in that: The iterative convergence condition in step 4 is that the error of the effective core multiplication factor is less than 10. -5 .

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