Patent Number: 
Section: claims

1. A moderator temperature coefficient measurement apparatus, comprising:an input unit having at least one storage device, the input unit receiving plant data including a coolant temperature signal being time series data on a temperature of a coolant of a light water reactor, and a reactivity signal indicating time series data on a reactivity calculated based on a detection value of a neutron flux in the light water reactor; anda data processing unit programmed to decompose the coolant temperature signal into N time-dependent temperature components and the reactivity signal into M time-dependent reactivity components by a singular value decomposition method,wherein the data processing unit is programmed to generate at least one selected combination by selecting a temperature component from the N time-dependent temperature components and a reactivity component from the M time-dependent reactivity components for each of the at least one selected combination, each of the at least one selected combination consisting of the selected temperature component and the selected reactivity component, andwherein the data processing unit is programmed to calculate a moderator temperature coefficient based on auto and cross power spectral density functions obtained by applying a Fourier transformation to the at least one selected combination,wherein the data processing unit is programmed to extract combinations each of which has a strong correlation between the coolant temperature signal and the reactivity signal on a basis of an auto correlation function from N×M combinations of the N time-dependent temperature components and the M time-dependent reactivity components, andwherein the at least one selected combination is selected from the combinations extracted by the data processing unit. 2. The moderator temperature coefficient measurement apparatus according to claim 1,wherein the data processing unit is programmed to generate temperature coefficient plot data for respective frequencies with use of auto and cross power spectral density functions obtained by applying a Fourier transformation to each of the at least one selected combination,wherein the temperature coefficient plot data includes a pair of a coherence and a moderator temperature coefficient, and calculate a moderator temperature coefficient at a coherence of 1 by extrapolating the temperature coefficient plot data. 3. The moderator temperature coefficient measurement apparatus according to claim 2, wherein the input unit receives a plurality of plant data different from each other, each of the plurality of plant data corresponds to the plant data, andwherein the data processing unit is programmedto calculate moderator temperature coefficients for the plurality of plant data, respectively, to count a number of high coherence data corresponding to the number of the temperature coefficient plot data for which the coherence is larger than a predetermined criterion andto output a reliable moderator temperature coefficient for which a number of the high coherence data is judged to be large based on a predetermined criterion, the outputted moderator temperature coefficient being selected from among the moderator temperature coefficients respectively corresponding to the plurality of plant data. 4. A void reactivity coefficient measurement apparatus, comprising:an input unit having at least one storage device, receiving plant data including a void fraction signal being time series data on a void fraction of a boiling water reactor, and a reactivity signal indicating time series data on a reactivity calculated based on a detection value of a neutron flux in the boiling water reactor; anda data processing unit programmed to decompose the void fraction signal into N time-dependent void fraction components, and the reactivity signal into M time-dependent reactivity components by a singular value decomposition method,wherein the data processing unit is programmed to generate at least one selected combination by selecting a void fraction component from the N time-dependent void fraction components and a reactivity component from the M time-dependent reactivity components for each of the at least one selected combination, each of the at least one selected combination consisting of the selected void fraction component and the selected reactivity component; andwherein the data processing unit is programmed-to calculate a void reactivity coefficient based on auto and cross power spectral density functions obtained by applying a Fourier transformation to the at least one selected combination,wherein the data processing unit is programmed to extract combinations each of which has a strong correlation between the void fraction signal and the reactivity signal on a basis of an auto correlation function from N×M combinations of the N time-dependent void fraction components and the M time-dependent reactivity components, andwherein the at least one selected combination is selected from the combinations extracted by the data processing unit. 5. A moderator temperature coefficient measurement method implemented on a moderator temperature coefficient apparatus including an input unit and a data processing unit, the method comprising:by the input unit, receiving plant data including a coolant temperature signal being time series data on a temperature of a coolant of a light water reactor, and a reactivity signal indicating time series data on a reactivity calculated based on a detection value of a neutron flux in the light water reactor;by the data processing unit, decomposing the coolant temperature signal into N time-dependent temperature components, and the reactivity signal into M time-dependent reactivity components by a singular value decomposition method;by the data processing unit, generating at least one selected combination by selecting a temperature component from the N time-dependent temperature components-and a reactivity component from the M time-dependent reactivity components for each of the at least one selected combination, each of the at least one selected combination consisting of the selected temperature component and the selected reactivity component; andby the data processing unit, calculating a moderator temperature coefficient based on auto and cross power spectral density functions obtained by applying a Fourier transformation to the at least one selected combination,wherein the generating at least one selected combination includes:extracting combinations each of which has a strong correlation between the coolant temperature signal and the reactivity signal on a basis of an auto correlation function from N×M combinations of the N time-dependent temperature components and the M time-dependent reactivity components; andselecting the at least one selected combination from the extracted combinations. 6. A computer program product embodied on a computer-readable medium and comprising code that, when executed, causes a computer to perform the following: receiving plant data including a coolant temperature signal being time series data on a temperature of a coolant of a light water reactor, and a reactivity signal indicating time series data on a reactivity calculated based on a detection value of a neutron flux in the light water reactor;decomposing the coolant temperature signal into N time-dependent temperature components, and the reactivity signal into M time-dependent reactivity components by a singular value decomposition method;generating at least one selected combination by selecting a temperature component from the N time-dependent temperature components and a reactivity component from the M time-dependent reactivity components for each of the at least one selected combination, each of the at least one selected combination consisting of the selected temperature component and the selected reactivity component; andcalculating a moderator temperature coefficient based on auto and cross power spectral density functions obtained by applying a Fourier transformation to the at least one selected combination,wherein the generating at least one selected combination includes:extracting combinations each of which has a strong correlation between the coolant temperature signal and the reactivity signal on a basis of an auto correlation function from N×M combinations of the N time-dependent temperature components and the M time-dependent reactivity components; andselecting the at least one selected combination from the extracted combinations.