Unit shutdown margin calculation method and system

Abstract

The invention relates to a unit shutdown margin calculation method and system. The method comprises the steps that whether control rod abnormity happens to a unit currently or not is judged; if yes, unit operation parameters are obtained; obtaining negative reactivity correlation coefficients of the corresponding units according to the unit operation parameters; obtaining a positive reactivity correlation coefficient of the corresponding unit according to the unit operation parameters; and determining the current actual shutdown margin value of the unit according to the negative reactivity correlation coefficient and the positive reactivity correlation coefficient. According to the method, the negative reactivity correlation coefficient and the positive reaction coefficient of the corresponding unit are obtained according to the unit operation parameters, so that the shutdown margin is quickly and accurately evaluated under the condition that the unit control rod is abnormal.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear power, and in particular to a method and system for calculating a shutdown margin of a unit. Background Art

[0002] During the normal operation of the nuclear power unit, the reactor must have the ability to shut down and maintain a subcritical state under operating conditions and accident conditions. Therefore, it is necessary to monitor the shutdown margin to ensure that the initial state of the core will not exceed the initial assumptions in the final safety analysis report to ensure that the reactivity accident will not damage the fuel. During the power operation of the unit, the shutdown margin is ensured to meet the requirements by limiting the rod positions of the shutdown control rod group, power control rod group and temperature control rod group. Therefore, when the state of the control rod group does not meet the requirements, there is a possibility that the shutdown margin does not meet the requirements. According to the requirements of the technical specifications, the operator is required to complete the calculation of the shutdown margin within 1 hour to confirm whether the requirements are met. If the requirements are not met, the shutdown margin needs to be restored to the required range.

[0003] At present, the shutdown margin of the unit is mainly obtained through simulation calculation by nuclear design software, which cannot cover various possible conditions in the operation of the unit. When the shutdown margin needs to be quickly verified during the operation of the unit, the power plant cannot directly apply the nuclear design software to simulate the shutdown margin, and the design unit cannot complete the shutdown margin calculation within the specified time. At this time, the unit will have to be withdrawn to a safe state, which has a very large impact on the economic efficiency of the unit. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the shutdown margin calculation cannot be completed within the specified time, and a shutdown margin calculation method and system for a unit are provided.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a method for calculating the shutdown margin of a unit, the method comprising the following steps:

[0006] Determine whether the unit currently has a control rod abnormality;

[0007] If yes, obtain the unit operating parameters;

[0008] Obtaining a negative reactivity correlation coefficient of a corresponding unit according to the unit operation parameters;

[0009] Obtaining a positive reactivity correlation coefficient of a corresponding unit according to the unit operation parameters;

[0010] The actual current shutdown margin value of the unit is determined according to the negative reactivity correlation coefficient and the positive reactivity correlation coefficient.

[0011] In one embodiment, the negative reactivity correlation coefficient includes first negative value data and second negative value data;

[0012] The step of obtaining the negative reactivity correlation coefficient of the corresponding unit according to the unit operation parameters comprises:

[0013] Acquire first negative value data; wherein the first negative value data is a first fixed constant;

[0014] According to the unit operation parameters, determining corresponding second negative value data based on preset negative value data;

[0015] Substituting the first negative value data and the second negative value data into a first function, the negative reactivity correlation coefficient is obtained.

[0016] In one embodiment, the unit operation parameters include abnormal control rod information, current fuel consumption value, actual position of R rods and actual position of gray rods;

[0017] The preset negative value data includes the corresponding relationship between the burnup value and the control rod value, the corresponding relationship between the R rod position and the value, and the corresponding relationship between the gray rod position and the value;

[0018] The second negative value data includes the total value of control rods at zero power, the maximum stuck rod value, the abnormal control rod value, the R rod bundle insertion effect and the gray rod bundle insertion effect;

[0019] The determining, according to the unit operation parameters and based on the preset negative value data, the corresponding second negative value data comprises:

[0020] According to the current burnup value, based on the corresponding relationship between the burnup value and the control rod value, respectively determining the total control rod value at zero power and the maximum stuck rod value;

[0021] Determining the abnormal control rod value according to the abnormal control rod information and the current burnup value and based on the corresponding relationship between the burnup value and the control rod value;

[0022] According to the actual rod position of the R rod, the insertion effect of the R rod bundle is determined based on the corresponding relationship between the rod position of the R rod and the value;

[0023] The gray rod bundle insertion effect is determined according to the actual gray rod positions and based on the corresponding relationship between the gray rod positions and the values.

[0024] In one embodiment, the positive reactivity correlation coefficient includes first positive value data and second positive value data;

[0025] The obtaining of the positive reactivity correlation coefficient of the corresponding unit according to the unit operation parameters comprises:

[0026] Acquire first positive value data; wherein the first positive value data is a second fixed constant;

[0027] According to the unit operation parameters, determining corresponding second positive value data based on preset positive value data;

[0028] Substituting the first positive value data and the second positive value data into a second function, the positive reactivity correlation coefficient is obtained.

[0029] In one embodiment, the unit operating parameters include a current power level;

[0030] The preset positive value data include: the corresponding relationship between the power value and the Doppler effect, and the corresponding relationship between the power value and the moderator temperature effect;

[0031] The second positive value data includes Doppler effect value and moderator temperature effect value;

[0032] The determining, according to the unit operation parameters and based on the preset positive value data, corresponding second positive value data comprises:

[0033] Determining the Doppler effect value according to the current power level and based on the corresponding relationship between the power value and the Doppler effect;

[0034] According to the current power level, the moderator temperature effect value is determined based on the corresponding relationship between the power value and the moderator temperature effect.

[0035] In one embodiment, the unit operating parameters further include current boron concentration; and the method further includes:

[0036] According to the current boron concentration, query the corresponding relationship between the preset boron concentration and the shutdown margin to determine the current target shutdown margin value of the unit;

[0037] Determining whether the actual shutdown margin value is greater than or equal to the target shutdown margin value;

[0038] If so, it is determined that the actual shutdown margin value meets the requirement.

[0039] In one embodiment, the first fixed constant includes a gray rod irradiation loss value; and the first function includes:

[0040] A=X1-X2-X3-(X1-X2-X3)*0.11-X5-X6-X7;

[0041] Among them, A is the negative reactivity correlation coefficient; X1 is the total value of the control rod at zero power; X2 is the maximum stuck rod value; X3 is the abnormal control rod value; X5 is the R rod bundle insertion effect; X6 is the gray rod bundle insertion effect; X7 is the gray rod irradiation loss value.

[0042] In one embodiment, the second fixed constant includes an uncertainty value of the Doppler effect, an uncertainty value of the moderator temperature effect, a cavitation effect value, and a flux redistribution effect value;

[0043] The second function comprises:

[0044] B=X8+X9+X 10 +X 11 +X 12 +X 13 ;

[0045] Wherein, B is the positive reactivity correlation coefficient, X8 is the Doppler effect value; X9 is the uncertainty value of the Doppler effect; X 10 is the value of the temperature effect of the moderator; X 11 is the uncertainty value of the moderator temperature effect; X 12 is the cavitation effect value; X 13 is the value of flux redistribution effect.

[0046] In one embodiment, determining the actual trip margin value according to the negative reactivity correlation coefficient and the positive reactivity correlation coefficient comprises:

[0047] The difference between the negative reactivity correlation coefficient and the positive reactivity correlation coefficient is calculated to obtain the actual shutdown margin value.

[0048] The present invention also provides a unit shutdown margin calculation system, comprising a processor and a memory storing a computer program, wherein the processor implements the steps of any one of the above-mentioned unit shutdown margin calculation methods when executing the computer program.

[0049] The implementation of the present invention has the following beneficial effects: The present invention relates to a method and system for calculating the shutdown margin of a unit, wherein the steps of the method include judging whether a control rod abnormality currently occurs in the unit; if so, obtaining the unit operating parameters; obtaining the negative reactivity correlation coefficient of the corresponding unit according to the unit operating parameters; obtaining the positive reactivity correlation coefficient of the corresponding unit according to the unit operating parameters; and determining the actual shutdown margin value of the unit according to the negative reactivity correlation coefficient and the positive reactivity correlation coefficient. The present invention achieves a rapid and accurate evaluation of the shutdown margin in the case of abnormal control rods of the unit by obtaining the negative reactivity correlation coefficient and the negative reaction coefficient of the corresponding unit according to the unit operating parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0051] Figure 1 It is a flow chart of a method for calculating the shutdown margin of a unit provided by the present invention;

[0052] Figure 2 is a schematic diagram of the overall rod bundle provided by the present invention;

[0053] Figure 3 It is a schematic diagram of the control rod value under different burn-ups provided by the present invention;

[0054] Figure 4 Schematic diagram of R-rod value under different fuel consumption provided by the present invention;

[0055] Figure 5 It is a schematic diagram of the ash stick value under different burn-up provided by the present invention;

[0056] Figure 6 It is a schematic diagram of the relationship between the power level and the Doppler effect provided by the present invention;

[0057] Figure 7 This is a schematic diagram of the relationship between the power level and the moderator temperature effect provided by the present invention.

[0058] Figure 8 It is a schematic diagram of the change of the minimum shutdown margin provided by the present invention with the boron concentration. DETAILED DESCRIPTION

[0059] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] The shutdown margin refers to the subcriticality when the reactor is in a subcritical or power operation state and an emergency shutdown occurs, assuming that the bundle of control rods with the largest reactivity value is completely pulled out of the core and all other control rods are completely inserted into the core. The shutdown margin is a capability to ensure that the reactor can be shut down and maintain a certain subcriticality. Since the shutdown margin refers to the shutdown capability of the reactor in an emergency shutdown state, slow reactivity compensation means, such as boron adjustment and burnable poisons, are not considered when calculating the shutdown margin. Only fast reactivity compensation means, such as control rods, temperature effects, and Doppler effects, are considered. Therefore, when a bundle of control rods cannot be fully inserted, the reactivity value of the bundle of control rods must be considered when determining the shutdown margin.

[0061] In the accident analysis of nuclear power plants, the risk of overcooling of the primary circuit due to mis-dilution of the primary circuit or rupture of the secondary circuit main steam pipe after the reactor shutdown is considered, which introduces positive reactivity into the reactor and then generates the risk of core re-criticality. Therefore, it is required that the reactor has a sufficient shutdown depth (subcriticality) after shutdown, so that even if mis-dilution of the primary circuit or rupture of the secondary circuit main steam pipe occurs at this time, it can buy enough time for the operator to intervene and prevent the reactor from returning to criticality.

[0062] During the power operation of the unit, the shutdown margin is ensured to meet the requirements by limiting the rod positions of the shutdown control rod group, power control rod group and temperature control rod group. Therefore, when the control rod group status does not meet the requirements, there is a possibility that the shutdown margin does not meet the requirements. According to the technical specifications, the operator needs to complete the calculation of the shutdown margin within 1 hour to confirm whether the requirements are met. If the requirements are not met, the shutdown margin needs to be restored to the required range.

[0063] The invention aims at the technical problem existing in the background technology: the shutdown margin calculation cannot be completed within the prescribed time.

[0064] like Figure 1 In order to solve the above problems, the present application provides a method for calculating the shutdown margin of a unit, the method comprising the following steps:

[0065] S1: Determine whether the unit currently has a control rod abnormality.

[0066] Specifically, this process can be achieved by real-time monitoring of key parameters of the control rod system (such as the position signal of the control rod, the current and voltage of the drive mechanism, the moving speed of the control rod, etc.). When these parameters deviate from the preset normal range or show abnormal fluctuations, it can be determined that the unit may have a control rod abnormality.

[0067] S2: If yes, obtain the unit operating parameters.

[0068] Specifically, operating parameters refer to various physical and chemical parameters exhibited by the unit in normal operation or abnormal state, including but not limited to one or more of reactor power, coolant temperature, neutron flux density, core pressure, core inlet and outlet temperature difference, and coolant flow rate. These parameters can fully reflect the operating status and performance of the unit.

[0069] S3: Obtain the negative reactivity correlation coefficient of the corresponding unit according to the unit operating parameters.

[0070] Specifically, the negative reactivity correlation coefficient refers to the reactivity that can reduce the reactor power or cause the reactor to shut down.

[0071] S4: Obtain the positive reactivity correlation coefficient of the corresponding unit according to the unit operating parameters.

[0072] Specifically, the positive reactivity correlation coefficient refers to the reactivity that can increase the reactor power or make the reactor tend to criticality.

[0073] S5: Determine the actual shutdown margin value of the unit according to the negative reactivity correlation coefficient and the positive reactivity correlation coefficient.

[0074] Further, the negative reactivity correlation coefficient includes first negative value data and second negative value data;

[0075] Obtaining the negative reactivity correlation coefficient of the corresponding unit according to the unit operating parameters includes:

[0076] Acquire first negative value data; wherein the first negative value data is a first fixed constant;

[0077] According to the unit operation parameters, the corresponding second negative value data is determined based on the preset negative value data;

[0078] The first negative value data and the second negative value data are substituted into the first function to obtain a negative reactivity correlation coefficient.

[0079] It should be noted that: the first fixed constant is pre-set according to the design characteristics and safety criteria of the reactor or nuclear power unit, which represents the negative reactivity value under certain fixed conditions (such as standard operating conditions) and is used to ensure the stability of the reactor within a specific operating range. The second negative value data is dynamically adjusted according to the real-time unit operating parameters (such as power level, temperature, pressure, etc.), which are associated with the negative reactivity value through a preset negative value data table or model, so as to reflect the reactivity changes under the current state of the unit.

[0080] Furthermore, the unit operation parameters include abnormal control rod information, current fuel consumption value, actual position of R rod and actual position of gray rod;

[0081] The preset negative value data include the corresponding relationship between the burnup value and the control rod value, the corresponding relationship between the R rod position and the value, and the corresponding relationship between the gray rod position and the value;

[0082] The second negative value data include the total control rod value at zero power, the maximum rod stuck value, the abnormal control rod value, the R rod bundle insertion effect and the gray rod bundle insertion effect;

[0083] According to the unit operation parameters, determining the corresponding second negative value data based on the preset negative value data includes:

[0084] According to the current burnup value, based on the corresponding relationship between the burnup value and the control rod value, the total control rod value and the maximum stuck rod value at zero power are determined respectively;

[0085] According to the abnormal control rod information and the current burnup value, the abnormal control rod value is determined based on the corresponding relationship between the burnup value and the control rod value;

[0086] According to the actual position of the R rod, the insertion effect of the R rod bundle is determined based on the corresponding relationship between the position of the R rod and the value;

[0087] According to the actual position of the gray rods, the gray rod bundle insertion effect is determined based on the corresponding relationship between the gray rod position and the value.

[0088] like Figure 2 As shown, in one embodiment, the operator finds that the SB-J11 rod cluster is out of step (see the figure below for the position of the J11 rod cluster). According to the technical specification, the calculation of the shutdown margin needs to be completed within 1 hour to confirm that it meets the limit requirements.

[0089] Unit operating parameters Numeric unit Remark Bundle Name SB-J11 Rod Bundle - - Current fuel consumption 13077 MWd / tU End of Life (EOL) R rod actual rod position 215 step Slightly inserted into the core GN (gray bar) actual bar position 615 step Full core extraction

[0090] The process of obtaining the second negative value data:

[0091]

[0092]

[0093]

[0094] Specifically, Figure 3As shown, this data is theoretically calculated during the refueling design phase. The first row of data represents different burnup steps, and each column of data represents the theoretical calculation data under this burnup step. The second row of data is the total value of all control rods, corresponding to the total value of control rods at zero power. The third to 70th rows are the values ​​of single bundles of 68 control rods in the core. According to the actual burnup of the core, the corresponding rod bundle value and total control value can be obtained by finding the data difference between the two nearest burnup steps. The first column is the position of the rod bundle in the core, and the subsequent columns correspond to the values ​​under different burnup steps. The largest bundle among the 68 rod bundles corresponds to the maximum stuck rod value. The value of the control rod bundle at the corresponding position found according to the stuck rod position is the corresponding abnormal control rod value.

[0095] like Figure 4 As shown, according to the actual position of the R rod, Figure 2 The data is used to calculate the difference and obtain the value of R rod insertion into the core, which corresponds to the R rod bundle insertion effect value.

[0096] like Figure 5 As shown, according to the actual rod position of the GN rod, Figure 5 The data is used to calculate the difference to get the value of GN rod insertion into the core, which corresponds to the gray rod bundle insertion effect.

[0097] Further, the positive reactivity correlation coefficient includes first positive value data and second positive value data;

[0098] The positive reactivity correlation coefficient of the corresponding unit is obtained according to the unit operating parameters, including:

[0099] Acquire first positive value data; wherein the first positive value data is a second fixed constant;

[0100] According to the unit operation parameters, the corresponding second positive value data is determined based on the preset positive value data;

[0101] Substituting the first positive value data and the second positive value data into the second function, a positive reactivity correlation coefficient is obtained.

[0102] Furthermore, the unit operating parameters include current power level;

[0103] The preset positive value data include: the corresponding relationship between power value and Doppler effect, the corresponding relationship between power value and moderator temperature effect;

[0104] The second positive value data include Doppler effect value and moderator temperature effect value;

[0105] According to the unit operation parameters, the corresponding second positive value data is determined based on the preset positive value data, including:

[0106] According to the current power level, the Doppler effect value is determined based on the corresponding relationship between the power value and the Doppler effect;

[0107] According to the current power level, the value of the moderator temperature effect is determined based on the corresponding relationship between the power value and the moderator temperature effect.

[0108] In one embodiment, the unit operating parameters include:

[0109] Unit operating parameters Numeric unit Remark Current power level 100％ - Rated full power

[0110] The process of obtaining the second positive value data:

[0111]

[0112] Specifically, Figure 6 As shown, the reactivity introduced by the Doppler temperature effect when the reactor is shut down at the current power is found through this figure, which corresponds to the Doppler effect.

[0113] like Figure 7 As shown, this figure is used to find the reactivity introduced by the moderator temperature effect when the reactor is shut down at the current power, and the corresponding moderator temperature effect value.

[0114] Furthermore, the unit operation parameter also includes the current boron concentration; and the method further includes:

[0115] According to the current boron concentration, the corresponding relationship between the preset boron concentration and the shutdown margin is queried to determine the current target shutdown margin value of the unit;

[0116] Determine whether the actual shutdown margin value is greater than or equal to the target shutdown margin value;

[0117] If yes, it is determined that the actual shutdown margin value meets the requirements.

[0118] In one embodiment:

[0119] Unit operating parameters Numeric unit Remark Current Boron Concentration 3 ppm -

[0120] The process of obtaining the current target shutdown margin value of the unit:

[0121]

[0122] Specifically, Figure 8 As shown, the minimum shutdown margin required under the current primary loop boron concentration is found through this figure, which corresponds to the current target shutdown margin value of the unit.

[0123] Further, the first fixed constant includes the gray rod irradiation loss value; the first function includes:

[0124] A = X1-X2-X3-X4-X5-X6-X7;

[0125] X4 = (X1-X2-X3)*0.11;

[0126] Among them, A is the negative reactivity correlation coefficient; X1 is the total value of control rods at zero power; X2 is the maximum stuck rod value; X3 is the abnormal control rod value; X5 is the R rod bundle insertion effect; X6 is the gray rod bundle insertion effect; X7 is the gray rod irradiation loss value.

[0127] In one embodiment, after long-term irradiation in the reactor, the control rod's ability to absorb neutrons weakens, resulting in loss of its value. Its influence needs to be considered when calculating the shutdown margin. According to theoretical calculations, the first fixed constant of 100pcm can cover all operating conditions, so the gray rod irradiation loss value is 100pcm.

[0128] A=X1-X2-X3-X4-X5-X6-X7; X4=(X1-X2-X3)*0.11; substituting the actual values, the negative reaction correlation coefficient is 11318-2766-130-926.42-100-0-100, which is equal to 7295.58.

[0129] The above parameters are all calculated using absolute values. Based on the above X1 to X7, the negative reactivity introduced by the insertion of all other control rods into the core can be obtained when a specific control rod and a maximum value control rod cannot be inserted into the core.

[0130] Furthermore, the second fixed constant includes the uncertainty value of the Doppler effect, the uncertainty value of the moderator temperature effect, the cavitation effect value, and the flux redistribution effect value;

[0131] The second function includes:

[0132] B=X8+X9+X 10 +X 11 +X 12 +X 13 ;

[0133] Where B is the positive reactivity correlation coefficient, X8 is the Doppler effect value; X9 is the uncertainty value of the Doppler effect; X 10 is the value of the moderator temperature effect; X 11 is the uncertainty value of the moderator temperature effect; X 12 is the cavitation effect value; X 13 is the value of flux redistribution effect.

[0134] In one embodiment, the uncertainty value of the Doppler effect is 100, the uncertainty value of the moderator temperature effect is 59, the cavitation effect value is 50, and the flux redistribution effect value is 850.

[0135] Second fixed constant:

[0136]

[0137]

[0138] Specifically, B = X8 + X9 + X 10 +X 11 +X 12 +X 13 ; Substituting the actual values, the positive reactivity correlation coefficient is 820+100+780+59+50+850, which is equal to 2659.

[0139] Further, determining the actual shutdown margin value according to the negative reactivity correlation coefficient and the positive reactivity correlation coefficient includes:

[0140] The difference between the negative reactivity correlation coefficient and the positive reactivity correlation coefficient is calculated to obtain the actual shutdown margin value.

[0141] In one embodiment, the actual shutdown margin value is equal to the negative reactivity correlation coefficient minus the positive reactivity correlation coefficient. Substituting the actual data into 7295.58-2659 equals 4636.58.

[0142] The actual shutdown margin value is 4636.58. The current target shutdown margin value of the unit is 3300. By comparing the values ​​of C (actual shutdown margin value) and D (current target shutdown margin value of the unit), if C≥D, the shutdown margin of the reactor still meets the requirements when the specific control rod and the maximum value control rod cannot be inserted into the core; otherwise, boronization and power reduction are required until the recalculated shutdown margin meets the requirements.

[0143] The present invention also provides a unit shutdown margin calculation system, comprising a processor and a memory storing a computer program, wherein the processor implements any of the steps of the unit shutdown margin calculation method described above when executing the computer program.

[0144] By implementing the present invention, when a control rod stuck, out of step or other faults occur during the operation of the unit, the operator can, based on the method, use the single rod bundle value and the total control rod value data in combination with the moderator temperature effect, Doppler power effect and other parameters read from the operation atlas to quickly calculate the shutdown margin under the current state, so as to verify whether the reactor shutdown margin meets the requirements of the technical specifications, ensure the safety of the reactor, and avoid the withdrawal of the unit.

[0145] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, the above technical features can be freely combined without departing from the concept of the present invention, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should belong to the coverage of the claims of the present invention.

Claims

1. A method for calculating the shutdown margin of a unit, characterized in that: The method comprises the following steps: Determine whether the unit currently has a control rod abnormality; If yes, obtain the unit operating parameters; Obtaining a negative reactivity correlation coefficient of a corresponding unit according to the unit operation parameters; Obtaining a positive reactivity correlation coefficient of a corresponding unit according to the unit operation parameters; The actual current shutdown margin value of the unit is determined according to the negative reactivity correlation coefficient and the positive reactivity correlation coefficient.

2. The method for calculating the shutdown margin of a unit according to claim 1, characterized in that: The negative reactivity correlation coefficient includes first negative value data and second negative value data; The step of obtaining the negative reactivity correlation coefficient of the corresponding unit according to the unit operation parameters comprises: Acquire first negative value data; wherein the first negative value data is a first fixed constant; According to the unit operation parameters, determining corresponding second negative value data based on preset negative value data; Substituting the first negative value data and the second negative value data into a first function, the negative reactivity correlation coefficient is obtained.

3. The method for calculating the unit shutdown margin according to claim 2, characterized in that: The unit operation parameters include abnormal control rod information, current fuel consumption value, actual position of R rod and actual position of gray rod; The preset negative value data includes the corresponding relationship between the burnup value and the control rod value, the corresponding relationship between the R rod position and the value, and the corresponding relationship between the gray rod position and the value; The second negative value data includes the total value of control rods at zero power, the maximum stuck rod value, the abnormal control rod value, the R rod bundle insertion effect and the gray rod bundle insertion effect; The determining, according to the unit operation parameters and based on the preset negative value data, the corresponding second negative value data comprises: According to the current burnup value, based on the corresponding relationship between the burnup value and the control rod value, respectively determining the total control rod value at zero power and the maximum stuck rod value; Determining the abnormal control rod value based on the abnormal control rod information and the current burnup value and on the corresponding relationship between the burnup value and the control rod value; According to the actual rod position of the R rod, the insertion effect of the R rod bundle is determined based on the corresponding relationship between the rod position of the R rod and the value; The gray rod bundle insertion effect is determined according to the actual gray rod positions and based on the corresponding relationship between the gray rod positions and the values.

4. The method for calculating the unit shutdown margin according to claim 2, characterized in that: The positive reactivity correlation coefficient includes first positive value data and second positive value data; The obtaining of the positive reactivity correlation coefficient of the corresponding unit according to the unit operation parameters comprises: Acquire first positive value data; wherein the first positive value data is a second fixed constant; According to the unit operation parameters, determining corresponding second positive value data based on preset positive value data; Substituting the first positive value data and the second positive value data into a second function, the positive reactivity correlation coefficient is obtained.

5. The method for calculating the unit shutdown margin according to claim 4, characterized in that: The unit operating parameters include current power level; The preset positive value data include: the corresponding relationship between the power value and the Doppler effect, and the corresponding relationship between the power value and the moderator temperature effect; The second positive value data includes Doppler effect value and moderator temperature effect value; The determining, according to the unit operation parameters and based on the preset positive value data, corresponding second positive value data comprises: Determining the Doppler effect value according to the current power level and based on the corresponding relationship between the power value and the Doppler effect; According to the current power level, the moderator temperature effect value is determined based on the corresponding relationship between the power value and the moderator temperature effect.

6. The method for calculating the shutdown margin of a unit according to claim 1, characterized in that: The unit operating parameters also include current boron concentration; the method also includes: According to the current boron concentration, query the corresponding relationship between the preset boron concentration and the shutdown margin to determine the current target shutdown margin value of the unit; Determining whether the actual shutdown margin value is greater than or equal to the target shutdown margin value; If so, it is determined that the actual shutdown margin value meets the requirement.

7. The method for calculating the shutdown margin of a unit according to claim 3, characterized in that: The first fixed constant includes the gray rod irradiation loss value; the first function includes: A=X1-X2-X3-(X1-X2-X3)*0.11-X5-X6-X7; Among them, A is the negative reactivity correlation coefficient; X1 is the total value of the control rod at zero power; X2 is the maximum stuck rod value; X3 is the abnormal control rod value; X5 is the R rod bundle insertion effect; X6 is the gray rod bundle insertion effect; X7 is the gray rod irradiation loss value.

8. The method for calculating the unit shutdown margin according to claim 5, characterized in that: The second fixed constant includes the uncertainty value of the Doppler effect, the uncertainty value of the moderator temperature effect, the cavitation effect value, and the flux redistribution effect value; The second function comprises: B=X8+X9+X 10 +X 11 +X 12 +X 13 ; Wherein, B is the positive reactivity correlation coefficient, X8 is the Doppler effect value; X9 is the uncertainty value of the Doppler effect; X 10 is the value of the temperature effect of the moderator; X 11 is the uncertainty value of the moderator temperature effect; X 12 is the cavitation effect value; X 13 is the value of flux redistribution effect.

9. The method for calculating the shutdown margin of a unit according to claim 1, characterized in that: Determining the actual shutdown margin value according to the negative reactivity correlation coefficient and the positive reactivity correlation coefficient comprises: The difference between the negative reactivity correlation coefficient and the positive reactivity correlation coefficient is calculated to obtain the actual shutdown margin value.

10. A system for calculating the shutdown margin of a unit, comprising a processor and a memory storing a computer program, characterized in that: The processor implements the steps of the unit shutdown margin calculation method according to any one of claims 1 to 9 when executing the computer program.

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