Method and program for measuring dynamic control rod worth

Abstract

A method for measuring dynamic control rod worth of the present invention comprises a process of calculating dynamic control rod worth, wherein a neutron to detector response conversion factor (NRCF) satisfies equation 1. [Equation 1] N]I: Normal ex-core detector count

Description

Dynamic control rod controllability measurement method and program

[0001] The present invention relates to a method and program for measuring dynamic control rod controllability.

[0002] Typically, a new nuclear fuel loading model is designed for each reactor cycle, and a safety analysis is performed on the target reactor. To verify the suitability of this design, various tests are conducted during reactor startup, one of the most critical of which is the control rod controllability measurement test.

[0003] A number of control rods are installed in the reactor core to enable adjustment of thermal output or axial power distribution, or to completely terminate the nuclear reaction within the core for various reasons.

[0004] These control rods do not operate individually, but are managed by control banks (control rod assembly groups) of six or ten, depending on the reactor size. These are broadly divided into a regulation control bank, which is responsible for controlling power levels and power distribution, and a shutdown control bank, which is responsible for shutting down the reactor. In addition, one control bank is composed of four or eight control rod assemblies, and a control rod assembly is composed of four or twelve individual control rods.

[0005] Meanwhile, the term "control rod controllability measurement" used during zero-power reactor characteristic testing refers to the act of measuring controllability of a control group, not individual control rod controllability. In the following description, a control rod does not mean an individual control rod, but rather a control group as is usually the case, and control rod controllability is also used as a term meaning control group controllability.

[0006] In addition, the reactivity refers to the critical state of the reactor, that is, the amount of change in the generation and annihilation of the number of neutrons (or the size of the neutron flux (the number of neutrons per unit area per second)) in the reactor. If a positive (+) reactivity (or positive reactivity) is inserted into the reactor, it means that the number of neutrons is continuously increasing because the generation of neutrons is greater than the annihilation, and if a negative (-) reactivity (or negative reactivity) is inserted, it means that the neutron annihilation is greater, so the number of neutrons in the entire core is continuously decreasing.

[0007] Meanwhile, there are three main methods used to measure the control rod controllability used in nuclear power plants: the boron dilution method, the control rod exchange method, and the dynamic control rod controllability measurement method. Among them, the dynamic control rod controllability method is the most developed method and has been used safely in Korea for over 20 years.

[0008] Dynamic control rod controllability is calculated using current / voltage and pulse signals from the plant's off-core instrumentation during control rod insertion and withdrawal. Unlike current / voltage signals, pulse signals are more susceptible to abnormalities, such as reactivity distortion due to overlapping signals and premature overlapping due to the selection voltage. This nonlinearity increases the error in control rod controllability measurements.

[0009] The previous method of measuring dynamic control rod controllability calculates the dynamic control rod controllability by using the Neutron to Detector Response Conversion Factor (NRCF) value of all external instruments in the process of calculating the dynamic control rod controllability.

[0010] In this way, if the dynamic control rod controllability is calculated using the values ​​of all outdoor instruments, the abnormal signals due to the superposition phenomenon are used as they are, which causes distortion in the controllability calculation.

[0011] To solve this problem, the existing method took the signal from the measuring instrument at the symmetrical position of the ideal measuring instrument and performed the calculation, but this cannot be applied when the measuring instrument of the symmetric channel also has an abnormal signal.

[0012] [Prior Art Literature]

[0013] [Patent Document]

[0014] (Patent Document 1) Korean Patent No. 10-0598037 (June 30, 2006)

[0015] (Patent Document 2) Korean Patent No. 10-1604100 (March 10, 2016)

[0016] The present invention is intended to overcome the above-described conventional problems, and an object of the present invention is to provide a dynamic control rod controllability measurement method and program that applies a method of excluding abnormal signals capable of reducing errors in control rod controllability measurement.

[0017] However, the technical problems to be solved by the present invention are not limited to the problems described above, and other problems not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0018] In order to solve the above technical problem, a method for measuring dynamic control rod controllability according to an embodiment of the present invention is such that, in the process of calculating dynamic control rod controllability, a neutron-to-detector response conversion factor (NRCF) satisfies the following mathematical expression 1.

[0019] [Mathematical Formula 1]

[0020]

[0021] N I : Normal outdoor measuring instrument number

[0022] The dynamic control rod controllability can be calculated by reflecting the normal off-road instrument signals, excluding the abnormal off-road instrument signals.

[0023] A program according to one embodiment of the present invention causes a computer to execute a dynamic control rod controllability measurement method described in any one of claims 1 and 2.

[0024] A method for measuring dynamic control rod controllability according to one embodiment of the present invention enables calculation of control rod controllability when symmetrically positioned off-shore measuring instruments simultaneously receive abnormal signals. Furthermore, the reliability of control rod controllability measurements can be enhanced by using only normal signals.

[0025] The following drawings attached to this specification illustrate preferred embodiments of the present invention, and together with the detailed description of the invention described below, serve to further understand the technical idea of ​​the present invention, and therefore, the present invention should not be interpreted as being limited to matters described in such drawings.

[0026] Figure 1 is a flowchart illustrating a method for measuring dynamic control rod controllability according to one embodiment of the present invention.

[0027] Figure 2 is a screen where measurement control performance calculation is selected in the INVERSE computer program.

[0028] Figure 3 is a screen where the information on the cycle and measurement control rod of the power plant is entered in the INVERSE computer program.

[0029] Figure 4 is a graph of an off-road measuring instrument signal output by the INVERSE computer code in the INVERSE computer program after reading the off-road measuring instrument measurement data.

[0030] Figure 5 is a screen where information on the channel and location of the abnormality measuring device is entered in the INVERSE computer program.

[0031] Figure 6 is a screen showing the INVERSE computer program calculating the dynamic control rod controllability using normal off-road measuring instrument signals.

[0032] Figure 7 is a screen showing the results of the dynamic control rod control performance output by the INVERSE computer program.

[0033] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms or words used in this specification and claims should not be interpreted as limited to their typical or dictionary meanings, and should be interpreted with meanings and concepts that conform to the technical spirit of the present invention based on the principle that the inventor can appropriately define the concept of a term to best explain his or her own invention. Therefore, the embodiments described in this specification and the configurations illustrated in the drawings are only some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention. Therefore, it should be understood that various equivalents and modified examples may exist as substitutes for them at the time of filing this application.

[0034] Additionally, when used herein, the terms "comprise", "include" and / or "comprising", "including" specify the presence of stated features, numbers, steps, operations, elements, elements and / or groups thereof, but do not preclude the presence or addition of one or more other features, numbers, operations, elements, elements and / or groups thereof.

[0035] Additionally, to facilitate understanding of the invention, the attached drawings are not drawn to scale and some components may be exaggerated in size. Furthermore, identical components may be assigned the same reference numbers in different embodiments.

[0036] The statement that two compared objects are "identical" means "substantially identical." Therefore, "substantially identical" may include deviations considered low in the art, such as deviations of less than 5%. Furthermore, uniformity of a parameter over a given region may imply uniformity on average.

[0037] Although terms like "first" and "second" are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless otherwise specified, a "first" component may also be a "second" component.

[0038] Throughout the specification, unless otherwise specifically stated, each element may be singular or plural.

[0039] Any configuration being placed “on top (or bottom)” of a component or “on top (or bottom)” of a component may mean not only that any configuration is placed in contact with the top (or bottom) of the component, but also that other configurations may be interposed between the component and any configuration placed on (or under) the component.

[0040] Additionally, when a component is described as being “on,” “connected to,” or “coupled to” another component, it should be understood that the components may be directly connected or coupled to one another, but that other components may also be “interposed” between the components, or that each component may be “connected,” “coupled,” or “connected” through other components.

[0041] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Furthermore, the use of "may" when describing embodiments of the present disclosure refers to "one or more embodiments of the present disclosure." Expressions such as "one or more" and "one or more" preceding a list of elements modify the list as a whole and do not modify individual elements in the list.

[0042] When reference is made throughout the specification to “A and / or B,” this means A, B, or A and B, unless otherwise stated, and when reference is made to “C to D,” this means C or more and D or less, unless otherwise stated.

[0043] When phrases such as "at least one of A, B, and C," "at least one of A, B, or C," "at least one selected from the group A, B, and C," or "at least one selected from A, B, and C," are used to specify a list of elements A, B, and C, the phrases can refer to any suitable combination.

[0044] The term "use" may be considered synonymous with the term "utilize." As used herein, the terms "substantially," "about," and similar terms are used as terms of approximation rather than degrees, and are intended to take into account inherent variations in measured or calculated values ​​that would be recognized by those skilled in the art.

[0045] Although terms such as first, second, third, etc. may be used herein to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could also be termed a second element, component, region, layer, or section without departing from the teachings of the exemplary embodiments.

[0046] For ease of description, spatially relative terms such as "beneath," "below," "lower," "above," "upper," and the like may be used herein to describe the relationship of one element or feature to another element(s) or feature(s) as depicted in the drawings. It will be understood that spatially relative positions encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. For example, if the device in the drawings is turned over, an element described as "beneath" or "lower" another element would be understood to be "above" or "upper" the other element. Thus, the term "beneath" can encompass both the above and below orientations.

[0047] The terminology used herein is for the purpose of describing embodiments of the present disclosure and is not intended to be limiting of the present disclosure.

[0048] Before explaining a method for measuring dynamic control rod controllability according to one embodiment of the present invention, a general method for measuring controllability is explained as follows.

[0049] The reactor is usually critical when the control rods are inserted into the core to a depth of about 50 to 70 pcm, and since the heat release point has already been determined before the dynamic controllability measurement test, the signal from the external instrument indicates a constant value with a strength of several hundred nA.

[0050] In this state, the driver changes the switch so that he can operate the control rod manually.

[0051] The dynamic control rod controllability measurement test begins with the control rods, which are inserted to a depth of approximately 50 to 70 pcm, being fully withdrawn at the maximum allowable speed, as requested by the user.

[0052] As the control rods are withdrawn, a positive reactivity equivalent to the initial insertion length is inserted into the core, increasing the overall neutron density and the signal strength of the upper and lower external measurement instruments. When the signals of the upper and lower external measurement instruments reach approximately 60% to 80% of the nuclear release point, the operator inserts only the control rods to be measured into the core at the maximum allowable speed at the user's request.

[0053] Once the control rod is fully inserted, withdrawal of the control rod begins immediately at the maximum allowable speed and continues until complete withdrawal.

[0054] At this time, the reaction calculator measures the current signal or pulse signal of the upper and lower external measuring instruments for the entire process.

[0055] With the complete insertion and withdrawal of the control rods, the neutron number density inside the core decreased to about 1 / 1000 of its peak value, and then began to gradually increase after the control rods were completely withdrawn. This is due to the positive reactivity of about 50 to 70 pcm added at the beginning of the test.

[0056] As the neutron flux inside the core, i.e. the neutron number density, increases, the signals from the upper and lower external measuring instruments increase to the point where it is time to insert another control rod for the next test. The same operation as the first test control rod is repeated. The time it takes for the signals from the upper and lower external measuring instruments to rise from the lowest point to a point suitable for the test depends on the initially given positive (+) reactivity, but it takes approximately 10 minutes.

[0057] Hereinafter, a method for measuring dynamic control rod controllability according to one embodiment of the present invention will be described with reference to the attached drawings.

[0058] Meanwhile, the external instrument used in the dynamic control rod controllability measurement method is installed on the outer periphery of the reactor core and detects neutrons leaking out of the core, thereby detecting changes in core power. The control rods are inserted into or withdrawn from the reactor core at a target speed by the external instrument. Multiple external instruments for this purpose may be used, and these may be located at various locations on the outer periphery of the core.

[0059] The dynamic control rod controllability measurement method evaluates the controllability by inserting / withdrawing only one control rod into / out of the core at maximum speed and using the current signal from the external measuring device obtained at that time.

[0060] In order to accurately determine the continuously changing core neutron average number density from the current signal, the relationship between the current signal and the core neutron average density (Density-to-Response Conversion Factor, DRCF) must be known, and since the result of the inverse reactivity relationship is the 'dynamic reactivity' that indicates the state in which control rods are continuously inserted, a relationship (Dynamic-to-Static Conversion Factor, DSCF) that can express this as the 'static controllability' described in the power plant operating manual is also required.

[0061] According to the general method of measuring dynamic control rod controllability, in the case of zero-power reactor characteristics tests in domestic Korean standard nuclear power plants and Westinghouse type nuclear power plants (both pressurized water nuclear power plants), the control rods are completely withdrawn from the core at the maximum allowable speed under the critical state of the reactor. Then, when the neutron flux reaches a certain value of the heat release point, the control rods are completely inserted into the core at the maximum allowable speed and then completely withdrawn again. At the same time, the current signals measured from the upper and lower outer core measuring devices are acquired to measure the control rod controllability.

[0062] More specifically, in the general dynamic control rod controllability measurement method, each of the measured upper and lower current signals is corrected to the optimal baseline signal, and then each current signal is normalized to the current signal at the time of control rod insertion, and these are summed (RSUM) by axial control rod insertion height, and then the neutron number density to instrument reactivity conversion constant (DRCF) calculated in advance by external instrument, control rod, and axial control rod insertion height to match this definition is applied to calculate the core average neutron number density by axial control rod insertion height, and this is substituted into the inverse reactivity relationship to obtain the dynamic controllability by axial control rod insertion height, and then the dynamic to static conversion constant (DSCF) is applied to calculate the final static control rod controllability by control rod insertion height.

[0063] Then, using the corrected current signal, the upper and lower current signals are first added up for each axial control rod insertion height, and then the signal is normalized (RTOT) based on the summed current signal at the time of control rod insertion, and the corresponding neutron number density to instrument response conversion constant (DRCF) and dynamic to static conversion constant (DSCF) are applied to calculate the static control rod controllability.

[0064] The basic procedure for producing DSCF and DRCF is disclosed in prior literature, such as Korean Patent No. 10-0598037 and ‘Measurement Results of Dynamic Control Rod Controllability Applied to 6 Light Water Nuclear Power Plants (2003 Fall Academic Conference Proceedings)’, so a detailed description thereof will be omitted.

[0065] In the conventional dynamic control rod controllability measurement method, the signals from the measuring instrument at the symmetrical position of the abnormal measuring instrument are obtained and calculated by summing them for each channel, as shown in Mathematical Equation 2 below. However, if the measuring instrument of the symmetric channel also has an abnormal signal, a situation arises where it cannot be applied.

[0066] [Equation 2]

[0067]

[0068] Here, Ch is the signal of each channel outdoor meter.

[0069] On the other hand, in a method for measuring dynamic control rod controllability according to one embodiment of the present invention, the dynamic control rod controllability is calculated by normalizing the normal off-road instrument signal while excluding the abnormal off-road instrument signal.

[0070] To this end, in the process of calculating the dynamic control rod controllability, the neutron to detector response conversion factor (NRCF) satisfies the following mathematical expression 1.

[0071] [Mathematical Formula 1]

[0072]

[0073] Here, N I is a normal outdoor measuring instrument.

[0074] Below, the overall application method of the above mathematical formula 1 will be described with reference to the drawings.

[0075] Figure 1 is a flowchart illustrating a method for measuring dynamic control rod controllability according to one embodiment of the present invention.

[0076] Referring to Fig. 1, the control rod controllability measurement test is performed by inputting the INVERSE computer code into the INVERSE computer program (120). Since the INVERSE computer program is a program used in general power plants, a detailed description thereof will be omitted.

[0077] Data measured through the control rod controllability measurement test are used to calculate dynamic control rod controllability using the INVERSE computer code. In this case, mathematical equation 1 is used within the INVERSE computer code. In conventional control rod controllability measurement tests, mathematical equation 2 was used.

[0078] A method (100) for measuring dynamic control rod controllability according to one embodiment of the present invention may include a dynamic control rod controllability measurement data input step (110), a calculation step (120a, 120b, 120c, 120d) using an INVERSE computer program (120), and a measurement control rod controllability result output step (130).

[0079] Here, the calculation step may include an abnormal outdoor measuring instrument selection step (120a), an NRCF calculation step (120b), a dynamic-static reactivity calculation step (120c), and a point reactivity calculation step (120d).

[0080] The process of calculating the dynamic control rod controllability in a power plant is described as follows.

[0081] Figure 2 is a screen where measurement control performance calculation is selected in the INVERSE computer program, and Figure 3 is a screen where information on the cycle and measurement control rod of the power plant is entered in the INVERSE computer program.

[0082] Select the measurement control performance calculation as shown in Fig. 2, and input the information on the cycle and measurement control rod of the power plant as shown in Fig. 3 (110, see Fig. 1) and execute it.

[0083] Figure 4 is a graph of an off-road measuring instrument signal output by the INVERSE computer code in the INVERSE computer program after reading the off-road measuring instrument measurement data, and Figure 5 is a screen in which information on the channel and location of an abnormal measuring instrument is entered in the INVERSE computer program.

[0084] The INVERSE computer code reads (loads) the measurement data from the outdoor measuring device and displays the information in a graphical format as shown in Fig. 4. The user looks at the outdoor measuring device signal in Fig. 4 to determine whether or not the device is an abnormal signal measuring device (120a, see Fig. 1), and inputs information on the channel and location of the abnormal measuring device as shown in Fig. 5.

[0085] Figure 6 is a screen showing the INVERSE computer program calculating the dynamic control rod controllability using normal off-road measuring instrument signals.

[0086] Figure 7 is a screen showing the results of the dynamic control rod control performance output by the INVERSE computer program.

[0087] The INVERSE computer program calculates the dynamic control rod controllability by using the normal off-road measurement signals remaining after excluding the abnormal measurement signals using the aforementioned mathematical expression 1 (120a, 120b, 120c, 120d, see Fig. 1). As shown in Fig. 6, the calculation of the dynamic control rod controllability is completed, and the result is displayed as shown in Fig. 7 (130, see Fig. 1).

[0088] In Figure 7, the line made of dots represents the actual measured controllability results, and the line made of solid lines represents the designed values ​​in the nuclear design report.

[0089] As described above, in the dynamic control rod controllability measurement method according to one embodiment of the present invention, controllability is calculated by normalizing only the signals from the off-core instrument that generate normal signals. Accordingly, the dynamic control rod controllability measurement method according to one embodiment of the present invention enables calculation of control rod controllability even when symmetrically positioned off-core instruments simultaneously generate abnormal signals. Furthermore, the reliability of the control rod controllability measurement value can be enhanced by using only normal signals.

[0090] Table 1 below compares the values ​​calculated using Equations 1 and 2, respectively, of the measured dynamic control rod controllability.

[0091] Control group design control performance (pcm) measurement control group (pcm) mathematical equation 2 mathematical equation 111,0951,0491,0632695685690342942142246636656635540541545

[0092] While various embodiments of the present invention have been described above, the drawings and detailed description of the invention described so far are merely illustrative of the present invention, and are used solely for the purpose of explaining the present invention and are not intended to limit the meaning or scope of the present invention as set forth in the claims. Therefore, those skilled in the art will understand that various modifications and equivalent embodiments are possible. Accordingly, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

Claims

1. A method for measuring dynamic control rod controllability in which the neutron-to-detector response conversion factor (NRCF) satisfies the following mathematical expression 1 in the process of calculating dynamic control rod controllability. [Mathematical Formula 1] N I : Normal outdoor measuring instrument number 2. In paragraph 1, A method for measuring dynamic control rod controllability that calculates dynamic control rod controllability by reflecting normal off-road instrument signals excluding abnormal off-road instrument signals.

3. A program that causes a computer to execute the dynamic control rod controllability measurement method described in either of paragraphs 1 and 2.

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