JP2003149378A - Neutron measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a neutron measuring device capable of easily determining that abnormality is present by detecting and displaying the abnormality before a mean-square measurement function works when the abnormality (trouble of a constituent element of the neutron measuring device or intrusion of external electrical noise) causing the variation of the mean-square measurement is present. SOLUTION: This neutron measuring device is provided with: a neutron detector 1 for measuring a neutron bundle in stopping or starting a nuclear reactor; a preamplifier 2 for amplifying a pulse train signal from the neutron detector 1; a mean square calculating means 42 for calculating the mean square of a signal component in a certain frequency band within the pulse train signal from the preamplifier 2; and an offset means 43 for offsetting the output of the calculating means 42. The neutron measuring means is equipped with an abnormality detection means 48 for detecting abnormality of the output of the calculating means 42 offset by the offset means 43.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neutron measuring apparatus, and more particularly to a neutron measuring apparatus using a root mean square measuring method using a neutron detector.

[0002]

2. Description of the Related Art As a monitoring device for a reactor output having a low neutron flux from a reactor shutdown state to an output increasing process, there are a "pulse number measuring method" and a "root mean square measuring method" for measuring a pulse train signal from a neutron detector. Is used. In particular, the pulse number measurement method is used for neutron measurement from the reactor shutdown state to the critical state, and the root mean square method is used for neutron measurement from the critical state to the ascending process. It is used in a single neutron detector and signal processor.

As shown in FIG. 6, the structure of a conventional neutron measuring apparatus that employs the pulse number measuring method and the root mean square measuring method is as follows: neutron detector 1 ', preamplifier 2', pulse measuring apparatus 3 ', and It was equipped with a root mean square measuring device 4 '. The pulse measuring device 3 ′ includes a wave height discrimination level setting circuit 31 ′,
A pulse height discriminating circuit 32 ', a pulse number counting circuit 33',
The display device 34 'and the trip circuit 35' were provided, and the wave height discrimination level 37 'and the pulse number measurement value 38' were used as signals. The root mean square measuring device 4'includes a band amplifier 41 ', a root mean square circuit 42', and a root mean square offset correction circuit 43 '.
And the root mean square offset correction value 44 ', and the root mean square neutron flux 50' and the corrected root mean square neutron flux 51 'were used as signals. Then, in the measurement by the pulse number measurement method, the pulse train signal from the neutron detector 1'is amplified by the preamplifier 2'and input to the pulse measurement device 3'and the root mean square measurement device 4 '. In the pulse measuring device 3 ', the pulse number counting circuit 33' is used after the pulse height discriminating circuit 32 'removes the pulse having the wave height smaller than the wave height discriminating level 37' preset by the pulse number discriminating level setting circuit 31 '. The number of pulses is counted by and the measured pulse number 38 'is output to the display 34' and the trip circuit 35 '.

In the root mean square measuring device 4 ', the root mean square circuit 42 is used after band amplification is performed in the band amplifier circuit 41'.
Performs root mean square in ′, performs appropriate range switching according to the value of the output, and further calculates the neutron flux value 50 ′ by multiplying by an appropriate coefficient, then performs offset correction in the offset correction circuit 43 ′, Find the final neutron flux 51 '.

The reason why the offset correction is performed in the root mean square measurement will be described with reference to FIG. The neutron flux during the reactor shutdown will be measured by pulse number measurement. Therefore, at this time, it is not necessary to perform measurement by means of root mean square. However, due to the neutron measurement function by means of root mean square during reactor shutdown, higher measurement results than the actual one can be obtained due to the influence of electrical noise. Therefore, by subtracting the offset value 44 'from the measured value of the root mean square measurement so that the measured value of the root mean square measurement does not fluctuate due to such an influence of electrical noise, etc. The average neutron flux value is set to zero.

When the nuclear reactor is started and the value of the neutron flux becomes high, the measured value in the root mean square measurement becomes larger than the offset value, so that the same measured value as the pulse number measurement can be obtained.
Further, the pulse becomes continuous, which makes it difficult to measure the number of pulses. Therefore, at an appropriate time (value 1 in Figure 6
By shifting from the pulse number measurement to the root mean square measurement with the value 2), the continuous neutron measurement can be performed from the reactor shutdown state to the power increase state.

By the way, in the conventional neutron measuring apparatus, since the offset correction is performed so as not to measure an unnecessary value in the neutron measurement by the root mean square measurement, the root mean square measurement is performed before the reactor is started while the reactor is stopped. It will be difficult to check if the soundness of the. That is, unless the root mean square measurement is performed after the reactor is started, it is not known whether the root mean square measurement is functioning normally. Therefore, even if the function of root-mean-square measurement becomes abnormal during reactor shutdown and normal measurement is not performed, it is difficult to detect this before reactor startup. Means As a factor that causes an abnormality in the root mean square measurement as described above, a detector, a signal cable between a detector and a preamplifier, a preamplifier, a signal cable between a preamplifier and a signal processing unit, a signal processing unit There is a problem in each component of the neutron measurement device such as the above, or an electric noise invading from the outside. If such an abnormality is found during reactor shutdown, it is possible to investigate and repair the defective part at that time, so it is possible to ensure sufficient reliability of the neutron measurement device before starting the reactor. it can.

As described above, the conventional neutron measuring apparatus has a problem that it is not possible to detect the abnormality of the root mean square measurement before the reactor is started.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is an abnormality that causes fluctuations in the root mean square measurement (a defect in the components of the neutron measurement apparatus or an external electrical noise). The purpose of the present invention is to provide a neutron measurement device that can detect and display anomalies before the root mean square measurement function operates and easily determine such anomalies when there is To do.

[0010]

The present invention is a neutron detector for measuring the neutron flux at the time of reactor shutdown or startup, a preamplifier for amplifying a pulse train signal from the neutron detector, and the pre-amplifier. In a neutron measurement apparatus comprising a root mean square calculation means for performing a root mean square of signal components in a constant frequency band of a pulse train signal from an on-amplifier, and an offset means for offsetting the output of the mean square calculation means, the offset means is It is a neutron measuring apparatus provided with an abnormality detecting means for detecting an abnormality in an output of a root mean square calculating means that is offset.

Further, according to the present invention, a second root mean square calculating means for performing a root mean square of the variation of the output of the mean square calculating means offset by the offset means, and a second mean square calculating means during the reactor shutdown. It is a neutron measuring apparatus provided with a comparing means for outputting an abnormal signal when the output of the root mean square calculating means becomes larger than a predetermined reference value.

Further, according to the present invention, the absolute value average calculating means for averaging the absolute values of the magnitudes of the outputs of the mean square calculating means offset by the offset means, and the output of the absolute value average calculating means during the reactor shutdown. Is a neutron measurement apparatus including a comparison unit that outputs an abnormal signal when the value becomes larger than a predetermined reference value.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described. One embodiment of the neutron measuring device of the present invention will be described with reference to FIGS. FIG. 1 is a configuration explanatory view of a neutron measuring device of an embodiment. FIG. 2 is an explanatory diagram of a time variation example (normal time) of the measured value of the root mean square neutron flux. Figure 3
It is explanatory drawing of the time change example (at the time of abnormal change generation) of the measured value of a root mean square neutron flux. FIG. 4 is an explanatory diagram of an example of a signal processing waveform performed by the neutron measurement device of the embodiment. FIG. 5 is an explanatory diagram of the sharing of the pulse measurement method and the root mean square measurement method in the neutron measurement apparatus.

An embodiment of the present invention will be described. As shown in FIG. 1, the neutron measuring apparatus of the present embodiment includes a neutron detector 1, a preamplifier 2, a pulse measuring apparatus 3 and a root mean square measuring apparatus 4. The neutron detector 1 measures the neutron flux of a nuclear reactor. The preamplifier 2 amplifies the pulse train signal from the neutron detector 1. Pulse measuring device 3
Has a pulse height discrimination level setting circuit 31, a pulse pulse height discrimination circuit 32, a pulse number counting circuit 33, a display device 34, a trip circuit 35, and a pulse number measurement mode determination circuit 36,
The signals of the wave height discrimination level 37, the pulse number measurement value 38, and the pulse measurement mode flag 39 are used. The root mean square measuring device 4 includes a band amplifier 41, a root mean square circuit 42, a root mean square offset correction circuit 43, and a root mean square offset correction value 4.
4, a time averaging circuit 45, a root mean square circuit 46, a comparison reference circuit 47, a comparison circuit 48 and an AND circuit 49 are provided, and a root mean square neutron flux 50 and a corrected root mean square neutron flux 5
1. The signals of the judgment result 52 and the abnormal signal output 53 are used. The root mean square circuit 46 is a second root mean square calculation means. The arithmetic processing and the like are performed by computer software.

In the neutron measuring apparatus of this embodiment, the pulse train signal output from the neutron detector 1 is the preamplifier 2
Is input to the band amplification circuit 41 and the root mean square circuit 42 via. The output of the root mean square circuit 42 is guided to the time average circuit 45, and the difference from the output is obtained to obtain the variation from the time average value, and this is input to the root mean square calculating means 46.
The output is compared with a reference value set in advance in the comparison reference circuit 47 in the comparison circuit 48, and if the output of the root-mean-square calculation unit> = reference value, the determination result 52 is output. This determination result 52 is ANDed with a pulse measurement mode flag 32 which is an output of a pulse number measurement mode determination circuit 36 described later, and an abnormal signal output 53 is transmitted to the outside.

By transmitting the abnormal signal output 53 as described above to the outside, the neutron flux measurement by the pulse number measurement before the neutron flux measurement by the root mean square measurement method at the stage of the reactor shutdown to the reactor critical state can be performed. Even at the stage of carrying out: 1) When there is no abnormal signal waveform in the root mean square neutron flux (before offset correction), the abnormal signal 52 is not output to the outside as shown in FIG. 2) When there is an abnormal signal waveform of the root mean square neutron flux (before offset correction) (see FIG. 3), the second root mean square calculation means detects a portion exceeding the reference value as shown in FIG. Therefore, the abnormal signal 52 can be output to the outside. (In the conventional neutron measurement apparatus, since the arithmetic mean is performed on the signal waveform shown in FIG. 3 to detect an abnormality, the abnormal waveform portion cannot be found.) Moreover, the soundness of the root mean square measurement function can be confirmed. Therefore, even when the measurement of the neutron flux is in the pulse number measurement region, the operator knows that some abnormality has occurred in the soundness of the root mean square measurement method, and can then take appropriate measures. .

The soundness confirmation of the root mean square measurement method here is performed when the neutron measurement is in the pulse number measurement state (pulse number measurement mode). Therefore, the above-mentioned determination result 52 needs to be output to the outside when the neutron measurement is in the pulse number measurement mode. The pulse number measurement mode determination circuit 36 determines whether the neutron measurement is in the pulse number measurement mode.

Whether the neutron measurement mode is the pulse number measurement mode or the root mean square measurement mode can be determined by the value of the measured neutron flux. Switching of this measurement mode is performed based on the measured values of both the neutron flux by pulse number measurement or the neutron flux by root mean square measurement. For example, as shown in FIG. 6, 1) root mean square neutron flux is 1 or less. : Neutron measurement by pulse number measurement method (pulse number measurement area) 2) Mean neutron flux value is 1 or more and value 2 or less: By pulse number measurement method and weighted calculation of medieval flux measurements of each of the root mean square measurement methods Neutron measurement (transition region. Weighting calculation so that the neutron flux component by the pulse number measurement becomes dominant at the location near the value 1, and the neutron flux component by the root mean square measurement becomes dominant at the location near the value 2. 3) Root mean square neutron flux is 2 or more: A method called neutron measurement by a root mean square measurement method (root mean square measurement area) is used.

Therefore, the pulse number measurement state determination circuit 36 in the neutron measurement apparatus according to this embodiment determines that the pulse number measurement mode is in effect because the value of the root mean square neutron flux is smaller than 1. The pulse measurement mode flag 32 is output. This pulse measurement mode flag 32
Is ANDed with the determination result 52 which is the output of the comparison circuit 48.
It is used for calculation, and in the pulse measurement mode, the abnormal signal output 53 is transmitted to the outside.

The neutron measuring apparatus of this embodiment can detect an abnormality in the root mean square measurement function even before the operation of the root mean square measurement function. It is possible to further improve the reliability of neutron measurement when the reactor is started. Specifically, while the reactor is shut down, the change in the root mean square neutron flux before the offset correction is in the normal state (see FIG. 2), while the root mean square neutron flux before the offset correction as shown in FIG. 3 is performed. When the neutron measuring apparatus according to the present embodiment is in an abnormal state exhibiting a large fluctuation, the root mean square is taken with respect to the fluctuation from the average value of the neutron flux values as shown in FIG. In comparison with the reference value, a variation larger than the reference value is found and is output to the outside as an abnormal signal.

The neutron measuring apparatus of the above embodiment is
Second root mean square calculation means for performing a mean square of the variation of the output of the mean square calculation means offset by the offset means, and output of the second mean square calculation means during the reactor shutdown are predetermined. The comparison means was provided for outputting an abnormal signal when it became larger than the reference value, but the absolute value average calculation means for averaging the absolute values of the magnitudes of the outputs of the mean square calculation means offset by the offset means and , It is also possible to find an abnormality in a neutron measurement device equipped with a comparison means that outputs an abnormality signal when the output of the absolute value average calculation means becomes larger than a predetermined reference value during a reactor shutdown. .

[0022]

According to the present invention, when there is an abnormality that causes fluctuations in the root-mean-square measurement (a defect in the components of the neutron measuring apparatus or the intrusion of external electrical noise), the abnormality is calculated as the root-mean-square. It is possible to obtain a neutron measurement device that can detect and display anomalies before the measurement function operates and can easily determine that such anomalies exist.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a configuration of a neutron measurement device according to an embodiment.

FIG. 2 is an explanatory diagram of an example of time change of a measured value of a root mean square neutron flux (normal time).

FIG. 3 is an explanatory diagram of an example of a temporal change in a measured value of a root mean square neutron flux (when an abnormal change occurs).

FIG. 4 is an explanatory diagram of an example of signal processing waveforms performed by the neutron measurement apparatus of the embodiment.

FIG. 5 is an explanatory diagram of sharing of a pulse measurement method and a root mean square measurement method in a neutron measurement device.

FIG. 6 is an explanatory diagram of a configuration of a neutron measuring device of a conventional example.

[Explanation of symbols]

1 Neutron detector 2 Preamplifier 3 pulse measuring device 31 Wave height discrimination level setting circuit 32 pulse wave height discrimination circuit 33 pulse counting circuit 34 Display 35 Trip circuit 36 Pulse number measurement mode judgment circuit 37 Wave height discrimination level 38 pulse number measurement value 39 Pulse measurement mode flag 4 root mean square measuring device 41 band amplifier 42 Root-mean circuit 43 root mean square offset correction circuit 44 root mean square offset correction value 45 hour averaging circuit 46 root mean square circuit 47 Comparison reference circuit 48 comparison circuit 49 AND circuit 50 root mean square neutron flux 51 Corrected root mean square neutron flux 52 Judgment result 53 Abnormal signal output

Claims (3)

[Claims] 1. A neutron detector for measuring a neutron flux at the time of shutting down or starting up a nuclear reactor, a preamplifier for amplifying a pulse train signal from the neutron detector, and a pulse train signal from the preamplifier. In a neutron measurement apparatus comprising a root mean square calculation means for performing a root mean square of signal components in a constant frequency band, and an offset means for offsetting the output of the mean square calculation means, the output of the mean square calculation means offset by the offset means A neutron measuring device comprising an abnormality detecting means for detecting the abnormality of the neutron. 2. The neutron measurement apparatus according to claim 1, wherein the second means for calculating the root mean square of the variation from the average value of the output of the root mean square calculation means offset by the offset means, and a nuclear reactor. A neutron measurement device comprising: a comparison unit that outputs an abnormal signal when the output of the second root mean square calculation unit becomes larger than a predetermined reference value during a stop. 3. The neutron measurement apparatus according to claim 1, wherein absolute value averaging means for averaging the absolute values of the magnitudes of the outputs of the root mean square computing means offset by the offset means, and absolute values during the reactor shutdown. A neutron measurement apparatus comprising: a comparison unit that outputs an abnormal signal when the output of the value average calculation unit becomes larger than a predetermined reference value.