KR101083155B1 - Method for determining reigional overpower protection trip setpoint to core state - Google Patents

Abstract

Disclosed are a method and system for preventing output deterioration during age degradation by setting a stop setpoint to protect nuclear fuel even in the most restrictive core state of the core state. According to the present invention, as a method for evaluating the stop setpoint of the core state, after calculating the stop setpoint using neutron flux distribution information, local overpower protection instrument information and thermal hydraulic information previously calculated for each of the 600 core state By deriving an optimal correlation between the signal distribution information of the local overload protection instrument and the stop setpoint, a method is provided so that the stop setpoint corresponding to each reactor state can be determined only by the instrument signal distribution.

Thus, the present invention estimates the stop set point corresponding to the reactor state from a pre-computed optimal correlation equation from the instrument signal distribution information that most accurately represents the reactor state during reactor operation. In the case of the limited core state, the stop set value corresponding to the limited core state is calculated. Therefore, compared to the conventional stop set value being fixed and operated in the limited core state, the stop set value is maintained at a high level in normal operation. Output reduction is unnecessary, and the effect of preventing losses of almost tens of billions of dollars annually is achieved.

 Stop setpoint, optimal correlation, core, aging

Description

How to determine the local overload stop setpoint corresponding to the core state {METHOD FOR DETERMINING REIGIONAL OVERPOWER PROTECTION TRIP SETPOINT TO CORE STATE}

The present invention relates to a method and system for determining a stop setpoint in a core state, and more particularly, to set a stop setpoint to protect nuclear fuel even in the most limited core state among the core state to prevent output deterioration during aging. And a method and system for the same.

Local overpower protection stop system of pressurized water reactor type nuclear power plant (hereinafter referred to as the heavy water reactor) reads 58 platinum measurement values installed inside the reactor and stops the reactor when the preset stop set value is exceeded. The problem is that due to the material and thermohydraulic characteristics of the reactor, the setpoint decreases at a constant rate every year, and therefore suffers huge economic losses by not operating the reactor at 100% power, but by operating it at several percent annually.

In particular, heavy water reactors are made of cast iron, and the outlet capillary of the heavy water reactors is made of cast iron, which causes iron to melt in the cooling water due to flow vibration corrosion and is deposited in the steam generator to deteriorate steam generator performance. The problem of increasing radial and axial directions causes the above stop setpoint to fall.

In general, the local overload protection stop setpoint of the heavy water channel is determined at the design stage in advance because it cannot calculate the core state that changes every moment. The core state under consideration is about 600. Computational simulation of each core state allows the calculation of the core damage probability corresponding to the core state. The stop setpoint is determined so that the minimum value of the 600 core damage probabilities is 98%. By determining the stop setpoint in this way, there is a 98% chance of stopping the reactor in any of the core operating states. However, the core state with the lowest probability of core damage has never been seen in the driving history for more than 100 years. On the other hand, the stop set point corresponding to the normal operating core state is about 9% higher than the stop set point (the most restrictive core state) installed in the reactor. Therefore, in terms of reactor operation and operation, there is a continuous demand for improvement of the inability to perform 100% full power operation due to the stop set point determined based on the state of the reactor without accidents occurring during operation. come.

If online real-time nuclear design / thermal-hydraulic design is possible, it is possible to solve the above problems by obtaining the stop set value reflecting the actual reactor status. do.

The present invention has been made to solve the above-mentioned conventional problems, and utilizes the signal distribution of the local overload protection measuring instrument installed in the furnace without design changes or real-time nuclear and thermal hydraulic calculations for the reactor, so as to stop the set point corresponding to the core state. The purpose is to provide a method for making a decision.

In order to achieve the object of the present invention as described above, and to perform the characteristic functions of the present invention described below, the characteristic configuration of the present invention is as follows.

According to one aspect of the present invention, a method for evaluating the stop setpoint of a local overload protection system corresponding to an arbitrary core state in real time, using an optimal correlation between a precalculated local overload protection instrument signal distribution and a stop setpoint A method is provided for determining a stop set point corresponding to a current core state from an instrument signal distribution input in real time.

Here, in deriving the optimum correlation between the signal distribution and the stop setpoint of the local overpower protection instrument, when a best correlation with the stop setpoint is derived for each single instrument, the 58 units measured in the field application After determining the stop setpoint, the first method of taking the lowest value as the stop setpoint of the current core state, selecting 3 to 4 instruments for each safety channel, and deriving the optimal correlation between the relative distribution between the selected instrument signals and the stop setpoint. A second method that takes the lowest value of the stop setpoints of the six safety channels as the stop setpoint of the current operating state, and selects 9 to 12 instruments for each reactor stop system, and selects the optimum signal correlation characteristic of the selected instrument signal distribution and the stop setpoint. In case of derivation and use, the lowest value of the stop setpoints of the two reactor shutdown systems is Using one of the methods in the third method takes a jiseol value may determine the stop value.

In addition, the method for evaluating the stop setpoint determined by the optimum correlation can determine the stop setpoint corresponding to any core state but having a stop probability of 98%.

In addition, the stop setpoint evaluation method may determine an optimal correlation using an alternative conditional expectation method or a group method of data handling.

In addition, according to another aspect of the present invention, by using the optimum correlation formula determined as described above to evaluate the stop setpoint in real time from the actual measurement instrument distribution information and compare it to the installed stop setpoint to apply the difference to the site as a penalty A stop setpoint determination method is provided.

According to the present invention, if the current core is normal, the corresponding stop setpoint is derived using an optimal correlation equation. If the current core is close to the limit core, the stop set point is also reduced to a corresponding degree, so that the stop set point corresponding to the limit core is reduced. Since there is no need to install it, there is no need to reduce the reactor output according to the aging deterioration, thereby preventing the loss of nearly hundreds of won every year and preventing the output reduction during the aging deterioration.

The following detailed description of the invention refers to the accompanying drawings, which illustrate, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that the various embodiments of the invention are different, but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein may be embodied in other embodiments without departing from the spirit and scope of the invention with respect to one embodiment. In addition, it is to be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention, if properly described, is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled. Like reference numerals in the drawings refer to the same or similar functions throughout the several aspects.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention.

1 is a view showing a stop setpoint evaluation system 100 according to an embodiment of the present invention by way of example.

As shown in FIG. 1, the stop setpoint determination system 100 according to an embodiment of the present invention includes an information collector 110, a stopset calculator 120, an optimal correlation derivation unit 130, and data storage. It is composed of a portion 140.

First, the information collecting unit 110 of the present invention is to evaluate the local overload protection stop set value, such as neutron flux distribution, thermal hydraulic calculation result information, instrument signal information, reactor operation history and uncertainty information for each of the 600 core state It collects, organizes and stores them in a file format.

Next, the stop set value calculation unit 120 of the present invention calculates a stop set value capable of stopping the reactor with a probability of 98% for each core state by utilizing various data provided by the information collection unit 110, The stop set value for each of the 600 core states is transmitted to the optimal correlation derivation unit 130 together with the signal distribution information of the instrument.

Next, the optimal correlation derivation unit 130 of the present invention derives an optimal correlation that associates the instrument signal distribution information with the stop set value. At this time, since the existing statistical method is difficult to find the optimal condition due to the user's judgment, initial condition, or complicated calculation step, multiple optimal regression such as Alternative Conditional Expectation or Group Method of Data Handling Use the method. The present invention applies an alternative conditional expectation method, but does not limit its use as long as it is a multiple optimal regression method that can find an optimal condition. However, since the optimal correlation of multiple optimal regression methods is essentially obtained as a set of discontinuities and mixed with the operation history, the discontinuities should be approximated as a series of functions to be used in the actual evaluation. The present invention approximates discontinuities with up to 9th order polynomials for fast computation. Accordingly, the optimum correlation is approximated by a higher-order polynomial of up to 9 orders according to the type of instrument signal distribution introduced, and the coefficient is obtained and transmitted to the coefficient storage unit 140. For example, the method of obtaining the optimal correlation by the alternative conditional expectation method is as follows.

The alternative conditional expectation method is that each independent variable (e.g., the instrument signal (x)) can be transformed into an arbitrary function f (x) that has the best correlation with it, and the transformed function is a dependent variable (here It is a theory that it has an optimal correlation with the optimal deformation function q corresponding to Y)). This relationship is expressed as an expression as follows.

In the formulas (1) and (2), Y _j denotes the stop set value of the j th case, and a _k denotes the coefficient of the k th term of the ninth order polynomial approximating the optimal strain function q of the stop set value, h _k (x) means k-th higher polynomial. E means to find the average value (or expected value) of the interval for the variable in square brackets around the j point. b _{j, k} denotes the coefficient of the kth term when the optimal deformation function f _j of the jth instrument (measurement signal value) is approximated by a higher-order polynomial, and N is the total number of independent variables considered. If all 58 instruments are used, N = 58, and if 3-4 instruments are used for each safety channel, N = 3-4 for each safety channel.

Equation (1) shows that the jth value of the optimal deformation function q corresponding to the stop set value (total of 600 discrete values in total) is expressed as the sum of the values of the optimal deformation function of the independent variable. Equation (2) also shows that the optimal strain function of a particular independent variable is expressed as the difference between the optimal strain function of the set point and the other. The equations (1) and (2) are solved repeatedly until the difference between the left and right sides of Eq. (1) is no longer reduced. The formula is expressed as follows.

Where e ² is the sum of squared errors and C ₆₀₀ is the total number of ROP cases (about 600). If Equation (3) has a minimum value, the optimal deformation function for each of the independent variable and the dependent variable is completed. Optimal strain functions are represented by a series of discontinuities. The alternative conditional expectation method, however, has the advantage that the optimal strain function is simplified enough to be easily expressed as a well-known function. Fig. 2 shows a typical form of an optimal strain function corresponding to a stop set point obtained by the alternative conditional expectation method when four detectors are selected in a certain safety channel.

The alternative conditional expectation method of the present invention is very useful for evaluating an approximation equation because the final optimal deformation function determined by the method is expressed in a form that can be easily approximated no matter how many independent and dependent variables are taken.

The instrument signal distribution can be defined in various ways in obtaining the optimal correlation between the instrument signal distribution information and the stop set value from Eqs. (1) and (2) by using more than 600 simulated data. For example, the optimum correlation is derived for each single instrument, and the measured 58 setpoints are substituted into each optimal correlation to calculate the stop setpoint, and the lowest value of the 58 stop setpoints is determined as the stop setpoint of the current operating state. The first method is to select three to four instruments for each safety channel and derive multiple optimal correlations between three to four instruments and the stop setpoints, taking the lowest of the six settling channels as the stop setpoint of the current operating state. In the second method, and two reactor shutdown systems (34 and 28 instruments each), select 9 to 12 instruments and derive multiple optimal correlations between these instrument signal distributions and stop setpoints. At least one of the third methods of taking the lowest value of the stop set values as the stop set value of the current operation state may be used. The determined stop set value TSP can be expressed as in Equation 4 below.

TPSＰ〓Ｍｉｎ (ｒ _j ) .... Formula (4)

Where r _j is a stop setpoint and can range from a minimum of two to a maximum of 58 per methodology. However, the correction factor can be introduced to have an average or 95% reliability because there is a difference between the stop set point obtained by the optimal correlation formula and the computer simulation. The introduction of the correction factor guarantees a 98% stopping probability even in the case of the stop set value derived by the optimal correlation, so that it can be used with confidence in the field. However, the stop set value derived by the introduction of the correction factor may be reduced by the correction factor.

Next, the data storage unit 140 of the present invention, for one of the three methods produced as a result of the optimal correlation derivation unit 130, the optimum correlation (corresponding to each selected instrument signal distribution characteristic ( It is responsible for storing the order and coefficient of the higher-order polynomial approximating f) and the approximate higher-order polynomial order and coefficient of the optimum correlation (q) corresponding to the stop set value in a specific electronic file. The saved electronic file is used as input for the online stop setpoint determination system.

FIG. 2 is a flowchart exemplarily illustrating a method S200 of determining a stop setpoint using an optimal correlation derived according to an embodiment of the present invention.

As shown in FIG. 2, the method (S200) of determining a stop set value from an optimum correlation equation determined according to an embodiment 100 of the present invention utilizes measured instrument signal information to calculate the instrument signal distribution introduced in FIG. 1. Comprising (S210), determining the stop setpoint using the optimum correlation equation and instrument signal distribution information (by instrument, by safety channel or by safety system) (S220), penalizing by the difference with the existing stop setpoint (S230) and providing a penalty to the on-line instrument calibration device (S240).

The step S210 of the present invention receives the measurement instrument signal and the distribution between the signals extracted by extracting a specific instrument signal corresponding to the methodology (any one of three methods) determined in advance for the stop setpoint evaluation in step 100 of the present invention. Calculate The distribution is the same as the method used in the optimal phase derivation step (100).

Next, step S220 of the present invention reads the higher-order polynomial orders and coefficients according to the methodology stored in the electronic file in step 100 of the present invention, and obtains the signal signal distribution characteristics provided in step S210 to the higher-order polynomial. Substitute the stop setpoint and determine it.

Next, step S230 of the present invention compares the determined stop set point (TSP _MEASRED ) with the existing stop set point (TSP _INSTALED ) installed in the field to generate a penalty as shown in Equation (5) below.

P = _{enalty TSP} INSTALED _{-TSP MEASRED} ... formula (5)

Subsequently, in step S240 of the present invention, the result generated by the penalty according to Equation (5) is added to the calibration value of the local overload protection measuring instrument in the same manner as in Equation (6) below to the on-line measuring instrument calibration device. By providing, the user can be confirmed.

Ｄ _Cnew ＝ Ｄ _Cold ＊ _{Ｐｅｎａｌｔｙ} ... Formula (6)

The D _Cnew is a value for re-evaluating the calibration value of the instrument to reflect the newly calculated stop set point in the field, and D _Cold is an instrument calibration value composed of other factors except the instrument signal before evaluating the stop set point according to the present invention. Indicates.

As described above, in the present embodiment, the optimum correlation equations for calculating the stop set point corresponding to the core state are calculated in advance using the above equations (1), (2), (3) and (4), and then Mounted in the stop setpoint evaluation system (S200), the target of the limited core is calculated by calculating the measured signal distribution characteristics of some specific measuring instruments and equations (4), (5), and (6) corresponding to the core state. If the penalty is negative (-) compared with the set stop value obtained in the installation, the calculated stop set value is higher than the set stop set value. During operation, the reactor can be operated while maintaining the stop setpoint near 9% higher than the existing stop setpoint.

1 is a diagram illustrating a stop setpoint determination system 100 according to an embodiment of the present invention.

FIG. 2 is a flowchart exemplarily illustrating a method S200 of determining a stop setpoint using an optimal correlation derived according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

100: stop setpoint determination system 110: information collection unit

120: optimal correlation derivation unit 130: control unit

Claims (6)

As a method of determining the stop setpoint of the local overload protection system corresponding to an arbitrary core state in real time, The optimal correlation is derived by using the optimal correlation between the signal distribution and the stop set point calculated in advance. In case of deriving the optimal correlation with the stop setpoint for each single instrument, the first method of determining the stop setpoint according to the optimal correlation for each of the multiple instruments measured in the field application and taking the lowest value as the stop setpoint of the current core state, A second method that takes the lowest value of the stop setpoints of each of the safety channels as the stop setpoint of the current operation state when selecting a plurality of instruments for each safety channel and deriving an optimal correlation between the relative distribution between the selected instrument signals and the stop setpoint. , And In the case of selecting a plurality of instruments for each reactor shutdown system and deriving and using multiple optimal correlations between the selected instrument signal distribution characteristics and the stop setpoint, the minimum value of each stop setpoint of the reactor stop system is taken as the stop setpoint of the current operation state. A method of determining a stop set point corresponding to a current core state from an instrument signal distribution input in real time based on a stop set value grouped in various forms using one of three methods. delete The method of claim 1, The method for determining the stop set value determined by the optimum correlation equation, A method of determining a stop set point corresponding to any core state but having a stop probability of 98%. The method of claim 1, The stop set value determination method, A method of determining stop setpoints using an optimal correlation using alternative conditional expectation or group method of data handling. The stop setpoint is determined in real time from the measured instrument distribution information in real time using the determined optimal correlation equation selected from any one of the above-mentioned 1, 3, and 4, and compared with the installed stop setpoint. Stop setpoint determination system, characterized in that applied to the local overpower protection stop system site. The method of claim 5, A stop setpoint determination system, characterized in that it is interlocked with a digital instrument calibration device in order to input the penalty to the digital instrument calibration device in real time in applying the penalty to the local over-power output protection system of the heavy water channel.

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