JPH09318785A - Fixed type in-core measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixed type in-core measuring device with high reliability by improving the measurement accuracy for microvoltage signal with a circuit constitution of an input signal amplifier, shortening measuring time and improving in noise resistance and grasping exact measured value, etc. SOLUTION: This fixed type in-core measuring device is provided with a plurality of gamma temperature meters 1 in the core of a reactor. An input signal amplifier 5 for amplifying the gamma temperature detection signal 2 from the gamma temperature meter 1 is constituted of a multiplexer 10 as a turn switching means of the plurality of detection signals, an input amplifier part 13 and a differential amplifier part 14 and an isolation 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor power measuring device for a boiling water reactor, and more particularly to a fixed core measuring device using a gamma ray thermometer.

[0002]

2. Description of the Related Art An in-core measuring device in a reactor power measuring device of a boiling water reactor has conventionally been provided with a plurality of neutron detectors each consisting of a small fission ionization chamber, which are used as a detector assembly. I am using. However, since the fission ionization chamber outputs a detection signal due to the ionization action of the fission fragments, the sensitivity gradually decreases with the burning of uranium.

Therefore, as a detector assembly, a plurality of fixed local power range monitors (Local Power Range Monitoring) installed in the core for monitoring the reactor state during operation.
(Hereinafter abbreviated as LPRM) detector and a mobile in-core instrumentation system (Traversing Inc) that continuously measures the distribution of neutrons in the vertical direction of the reactor by moving the reactor in the vertical direction.
ore Probe System, hereinafter abbreviated as TIP) detector. Note that the TIP detector is also used for calibration for the sensitivity decrease of the fixed type LPRM detector.

Further, the detection signals relating to the reactor output from the LPRM detector and the TIP detector are extracted to the outside of the reactor pressure vessel forming the reactor and the reactor containment vessel surrounding the reactor pressure vessel. And is provided to the reactor power measurement by signal processing in the in-core signal processing unit.

[0005]

Recently, as a fixed type in-core instrumentation device (Fixed Incore Calibration, FIC),
A large number of gamma thermometers (GT) are installed in the core to measure the output of the reactor and
It is also used for calibration of RM detectors.

This gamma ray thermometer, unlike the conventional LPRM detector, does not require a high-voltage power source as a detector and has no deterioration in sensitivity, so that it is highly reliable. However, by arranging an electric heater in the vicinity for calibration and because the output signal is a minute voltage, by solving the following problems,
Further, the function and reliability can be improved. (1) Improvement of measurement accuracy, (2) Reduction of measurement time, (3)
Improving reliability, (4) Improving noise resistance, (5) Understanding accurate measured and used values.

The object of the present invention is to improve the measurement accuracy of a minute voltage signal by the circuit configuration of the input signal amplifier, to shorten the measurement time and to improve the noise resistance, and to grasp an accurate measured value. An object of the present invention is to provide a highly reliable fixed type in-core measuring device.

[0008]

In order to achieve the above-mentioned object, the fixed type core measuring apparatus according to claim 1 is a fixed type core measuring apparatus using a plurality of gamma ray thermometers arranged in a core of a nuclear reactor. A calibration heater is provided in the gamma ray thermometer, and an input signal amplifying unit that amplifies the detection signals from the plurality of gamma ray thermometers is an isolation unit that sequentially switches a plurality of detection signals, an input amplifying unit, and a differential amplifying unit. It consists of and.

The fixed core in-core measuring device in the reactor power measuring device has no deterioration due to the adoption of the gamma ray thermometer.
The calibration by the IP detector is not necessary and the reactor output can be monitored with high reliability. In addition, the output from the input signal amplifier is directly affected by common mode noise even if the insulation resistance of the gamma ray thermometer is reduced due to the isolation provided on the output side of the differential amplifier. Since it does not spread to other parts, the soundness of the in-core measurement system is improved and the detection signal is measured accurately.

The fixed core in-core measuring device according to claim 2 is
In the input signal amplifying section, the sequential switching means is a multiplexer. The circuit configuration is simple and highly reliable, and the time required to measure the detection signals from a plurality of gamma ray thermometers can be shortened.

According to a third aspect of the fixed core in-core measuring device,
In the input signal amplification section, a filter is provided for each of the plurality of gamma ray thermometers on the input side of the multiplexer, which is a sequential switching unit. The switching operation of the detection signals from multiple gamma-ray thermometers by the multiplexer is switched sequentially, but it is possible to switch to another signal without waiting until the rounding by the filter of the detection signal before switching is restored to the original, so the switching time is shortened. Thus, the measurement time of the detection signal from the gamma ray thermometer, which is a plurality of minute voltage signals, is shortened.

According to a fourth aspect of the fixed core in-core measuring device,
In the input signal amplifier, the input amplifier is a non-inverting amplifier having high input impedance. Since the input impedance is high with respect to the detection signal from the gamma ray thermometer having a very small voltage, the influence of the impedance change caused by the signal cable or the like can be ignored, and the detection signal from the gamma ray thermometer can be accurately measured.

According to a fifth aspect of the fixed in-core measuring device,
In the input signal amplifying section, a capacitor is provided on the common signal input side of the input amplifying section. The influence of the common code potential difference is eliminated, the common code noise resistance is improved, and the detection signal from the gamma ray thermometer can be accurately measured.

According to a sixth aspect of the fixed core in-core measuring device,
In the input signal amplifying means, a disconnection detecting circuit is provided on the lines of the plurality of gamma ray thermometers on the input side of the sequential switching means. By bypassing the signal cable with the bypass reference potential, when the gamma ray thermometer is disconnected, the signal level becomes upscale and the disconnection is detected, so that the soundness of the in-core measurement system is improved.

According to a seventh aspect of the fixed core in-core measuring device,
It is characterized in that the bias reference potential of the circuit for detecting disconnection provided on the input side of the switching means in the input signal amplifying means is supplied from a separate power supply insulated from the power supply of the input signal amplifying means. Since the power supply for the bias reference potential of the disconnection detection circuit is insulated from the power supply for the input signal amplification section, the common mode noise immunity is increased and the reliability of the in-core measurement system is improved.

[0016] A fixed type core measuring device according to claim 8 is
The input signal amplification section is characterized in that a reference potential by an independently provided power source or an internal signal common is provided to automatically perform offset correction and gain adjustment of the input signal amplification section. Since the calibration of the input signal amplification section becomes easy at the same time when the detection signals from the plurality of gamma ray thermometers in the sequential switching means are switched, the soundness of the input signal amplification section is improved and the detection signal from the gamma ray thermometer is improved. It can be measured accurately.

According to a ninth aspect of the fixed core in-core measuring device,
In the calibration of the detection signal from the gamma ray thermometer in the input signal amplification unit, offset correction and gain adjustment of the target detection signal are performed on demand after multiplexing by the sequential switching means. By improving the reliability of hardware such as the input signal amplifier and reducing the load of signal processing, the response time can be shortened and the measurement time can be shortened.

The fixed core in-core measuring device according to claim 10 is:
The amplification gain is fixed in the input signal amplification unit. By simplifying the circuit configuration of the input signal amplifying section, reliability is improved and errors that occur at the time of gain switching are eliminated, and gain switching is performed by software means to accurately measure the detection signal from the gamma ray thermometer.

A fixed core in-core measuring device according to claim 11 is
It is characterized in that the gain in the input signal amplification section is inversely calculated by the software means in the input signal amplification section from the measured value of the detection signal from the gamma ray thermometer.
The accurate measured value can be grasped by actual measurement, and the gain of the input signal amplification section can be easily monitored, and the reliability of the in-core measurement system is improved.

A fixed type core measuring device according to claim 12 is:
In the input signal amplifying unit, the input amplifying unit is an inverting amplifier having a high input impedance. Since the input impedance is high with respect to the detection signal from the gamma ray thermometer having a very small voltage, the influence of the impedance change caused by the signal cable or the like can be ignored, and the detection signal from the gamma ray thermometer can be accurately measured.

A fixed-type in-core measuring device according to claim 13 is
A filter is provided on the output side of the differential amplifier in the input signal amplifier. Although the processing time of detection signals from multiple gamma ray thermometers will be slightly slower, it is not necessary to provide a filter for each of many gamma ray thermometers, so the reliability of the in-core measurement system is improved by reducing the number of parts. can do.

The fixed-type in-core measuring device according to claim 14 is
It is characterized in that the switching means in the input signal amplifying section is sequentially a switched capacitor. Unlike the case of the multiplexer, there is no sneak between the signals, and the noise resistance is improved together with the isolation function between the signals.

The fixed core in-core measuring device according to claim 15 is:
In the calibration heater power supply unit that supplies power to the calibration heater of the gamma ray thermometer, the heater power supply is connected to the calibration heater by the heater cable through the switching unit that controls the supplied power, and the output side of the switching unit is connected. A feature is that a diode is provided. Since the diode suppresses the noise due to the counter electromotive force caused by the inductance generated when the switching unit malfunctions, the influence of the noise is reduced.

[0024] According to a sixteenth aspect of the fixed in-core measuring device,
The calibration heater power supply unit is characterized in that a monitor for the output side voltage is provided on the output side of the switching unit. Since the voltage value supplied to the calibration heater can be measured accurately, the detection signal from the gamma ray thermometer can be confirmed by checking the accurate value of the heater output from the calculation of the accurate value of the heater resistance using the current value. Can calibrate with high accuracy.

[0025] The fixed core in-core measuring device according to claim 17 is
A heater side voltage monitor is provided near the calibration heater in the calibration heater power supply section. Since the voltage value applied to the calibration heater can be accurately measured without being substantially affected by the resistance of the heater cable, the detection signal from the gamma ray thermometer can be accurately calibrated.

The fixed in-core measuring device according to claim 18 is:
It is characterized in that the resistance value of the heater cable is calculated from the comparison of the voltage values measured by the output side voltage monitor and the heater side voltage monitor in the calibration heater power supply section. Since the resistance value of the heater cable can be accurately calculated, the detection signal from the gamma ray thermometer can be accurately calibrated by this.

The fixed core in-core measuring device according to claim 19 is:
When the resistance value of the calibration heater is calculated from the heater current value and the heater power supply voltage in the calibration heater power supply unit, the correction is performed by the heater cable resistance value.
Since the accurate resistance value of the output loop of the calibration heater output is obtained, the detection signal from the gamma ray thermometer can be accurately calibrated.

A fixed type core measuring device according to claim 20 is
In a plurality of gamma ray thermometers arranged in the core, a cable separating box is provided in the middle of the signal cable and the heater cable drawn from the gamma ray thermometer to separate the signal cable and the heater cable. Since the signal cable and the heater cable are separately installed, the contact between the signal cable and the heater cable is prevented, so that the noise resistance is improved and the detection signal from the gamma ray thermometer can be accurately calibrated.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. In the following drawings, for easy understanding, one gamma-ray thermometer and a device corresponding thereto are shown. The first embodiment relates to claims 1 to 11, and as shown in the circuit configuration diagram of FIG. 1, in the fixed core measuring device of the reactor power measuring device, the gamma ray thermometer 1 is not shown in the core. A gamma ray thermometer detection signal (hereinafter abbreviated as GT detection signal) 2 that is installed inside and is output from the gamma ray thermometer is input to the input signal amplification section 5 via a signal cable 4 having a cable resistance 3.

The gamma ray thermometers 1 in the fixed-type in-core measuring device are generally arranged in the core of a boiling water reactor, for example, 9 at each of about 50 places, and GT detection from 500 or more in total. The signal 2 is output to an in-core signal processing unit or the like (not shown) via the input signal amplifying unit 5.

The input signal amplifying section 5 includes a filter 6 provided for each signal cable 4 in each channel of the gamma ray thermometers 1, a common power source 7 that is the same as the power source of the input signal amplifying section 5, or the input signal. A disconnection detection circuit 9 to which a bias-use reference voltage is supplied by a separate power supply 8 which is insulated from the power supply of the amplification section 5 is provided.
7).

Furthermore, G from a plurality of gamma ray thermometers 1
A multiplexer 10 is provided as a sequential switching means for inputting the T detection signal 2 and sequentially switching the T detection signal 2. The multiplexer 9 is connected to a reference potential by an internally independent power source or an internal signal common 12. (Claims 2 and 8). In addition, the multiplexer 10
On the output side of, the input amplification unit 13 and the differential amplification unit 14,
The isolation 15 and the isolation 15 are connected (Claim 1).

The input amplifying section 13 is formed by high impedance non-inverting amplifiers 16a and 16b. One of the non-inverting amplifiers 16a receives the output of the multiplexer 10 and the other non-inverting amplifier 16b includes the GT. Input common signal 17. Further, a capacitor 18 is connected to the input side of the GT common signal 17 of the non-inverting amplifier 16b (claim 4,
5).

The differential amplifying section 14 is formed by a differential amplifier 19, and the gain of the input signal amplifying section 5 is fixed, and this gain switching is performed by a software means (not shown). (Claims 1 and 10).

Next, the operation of the above configuration will be described. The multi-channel GT detection signals 2 output from the multiple gamma ray thermometers 1 installed in the core are input to the input signal amplifying section 5 via the respective signal cables 4, and the filters 6 are applied to each channel. After that, the multiplexer 10 sequentially switches.

At this time, since the filter 6 is provided in front of the multiplexer 10 for each channel, when the multiplexer 10 switches a plurality of GT detection signals 2, the filter 6 of the GT detection signal 2 before the switching is changed. It is possible to easily switch to another GT detection signal 2 immediately without waiting until the rounding of the signal due to is restored. Therefore, the switching of the multiplexer 10 is speeded up, and the measurement time of the GT detection signal 2 which is a plurality of minute voltage signals can be shortened.

Next, each GT detection signal 2 switched by the multiplexer 10, together with the GT common signal 17 common to each string, is a non-inverting amplifier of the input amplifier 13.
16a and the non-inverting amplifier 16b. At this time, since the non-inverting amplifiers 16a and 16b forming the input amplifier 13 have high impedance, the cable resistance 3 and the like in the signal cable 4 to which the GT detection signal 2 detected by the gamma ray thermometer 1 is transmitted. It is possible to ignore the change in impedance caused by

Further, since the capacitor 18 is connected to the input side of the non-inverting amplifier 16b to which the GT common signal 17 is input, the influence due to the common code potential difference is eliminated, so that the common code noise resistance is improved. . Therefore, by these, the GT detection signal 2 which is the minute voltage signal can be accurately measured.

The output of the input amplifier 13 is further amplified by the differential amplifier 19 of the differential amplifier 14. The differential amplifier 19 eliminates the influence of the common mode potential difference in the input amplifier 13. Since the common mode noise resistance is improved, the GT detection signal 2 can be accurately measured.

Further, the output 20 from the input signal amplifying section 5 to the in-core signal processing section or the like (not shown) is an isolation signal.
Even if the insulation resistance of the gamma-ray thermometer 1 arranged in the furnace is lowered,
The influence of common mode noise does not directly affect the signal processing unit in the reactor. Therefore, the soundness of the fixed core in-core measuring device is improved, and the GT detection signal 2 can be accurately measured.

Further, regarding the gamma ray thermometer 1 arranged in the furnace and the monitoring of the disconnection in the signal cable 4 thereof, the disconnection detection circuit 9 for the bypass which is supplied from the power source 7 common to the input signal amplifying section 5 is used. The signal cable 4 is bypassed by the reference potential. At this time, when the gamma-ray thermometer 1 and the signal cable 4 are disconnected, the signal level is upscaled, and therefore the disconnection can be easily detected, so that the reliability of the fixed core in-core measuring device is improved. improves.

If the supply of the bias reference voltage of the disconnection detection circuit 9 is obtained from another insulated power supply 8 different from the common power supply 7 of the input signal amplifier 5, the disconnection detection circuit 9 also receives a bias. The reference voltage for use is insulated from the circuit of the input signal amplifier 5.

Therefore, even if the common mode noise resistance is increased and the insulation resistance of the gamma ray thermometer 1 is lowered, the influence of the common mode noise does not directly affect the in-core signal processing section and the like, so the fixed core The reliability of the internal measuring device is further improved.

In the input signal amplifying section 5, the G
When the T detection signal 2 is sequentially switched, the reference potential 11 obtained from the output of the power supply independently provided in the input signal amplifier 5,
Alternatively, by selecting either of the internal signal commons 12, the offset correction and the gain adjustment in the input signal amplification section 5 can be automatically performed (claim 9). As a result, the soundness of the input signal amplification 5 is improved, and the GT detection signal 2 can be accurately measured.

In the input signal amplifying section 5,
The plurality of GT detection signals 2 are sequentially switched by the multiplexer 10 or the like, but the GT detection signal 2 is selected as necessary, and the offset correction to the specific GT detection signal 2 is performed after the GT detection signal 2 is selected. To do so. That is, by performing the offset correction and the gain adjustment on demand, the reliability of the in-core signal processing unit (not shown) is improved, the signal processing load is reduced, and the response time is shortened to reduce the measurement time. Can be shortened.

In the input signal amplifying section 5, the gain for amplifying the GT detection signal 2 is fixed, and
By performing the gain switching by a software means (not shown), the circuit configuration of the input signal amplifying section 5 can be simplified, the reliability is improved, the error generated at the gain switching is eliminated, and the GT detection signal 2 is accurately generated. Can be measured.

Further, in the input signal amplifier 5, the GT
Gains of the input signal amplifying section can be calculated in reverse by obtaining actual measured values when the detection signal 2 is amplified from the input side and the output side of the input signal amplifying section 5 and calculating by software means not shown. Item 11). As a result, the gain of each of the plurality of input signal amplifying units 5 can be easily confirmed, and the reliability of the input signal amplifying unit 5 is improved by correcting the gains if necessary. Therefore, the GT detection signal 2 can be accurately measured.

The second embodiment relates to claim 12, and as shown in the circuit configuration diagram of FIG. 2, the input signal amplifying section 21 in the fixed core in-core measuring apparatus is an inverting amplifier having a high impedance in the input amplifying section 22. It is composed of 23a and 23b. The other parts have the same structure as that of the first embodiment.

The operation of the above configuration is as follows:
Since the inverting amplifiers 23a and 23b as 22 have high impedance, they are caused by the cable resistance 3 and the like in the signal cable 4 to which the GT detection signal 2 detected by the gamma ray thermometer 1 input from the multiplexer 10 is transmitted. Changes in impedance can be ignored. Therefore,
The GT detection signal 2 which is a minute voltage signal can be measured with high accuracy, and other effects and advantages similar to those of the first embodiment can be obtained.

The third embodiment relates to claim 13, and as shown in the circuit configuration diagram of FIG. 3, the input signal amplifying section 24 in the fixed in-core measuring device is a differential amplifier 19 in the differential amplifying section 25. A filter 26 is provided on the output side of the. Also, unlike FIG. 1 of the first embodiment, a plurality of filters 6 corresponding to the channels of each gamma ray thermometer 1 on the input side of the multiplexer 10 to which a plurality of GT detection signals 2 are input, and a non-inverting amplifier 16b. The capacitor 18 connected to the input side of is not provided. The other parts are configured similarly to the first embodiment.

The operation of the above configuration is that one filter 26 is provided on the output side of the input signal amplifying section 24, so that on the input side of the multiplexer 10, a filter is provided for each channel for inputting a plurality of GT detection signals 2. 6 and the capacitor 18 connected to the input side of the non-inverting amplifier 16b are no longer required.

As a result, although the signal processing time for the sequential switching in the multiplexer 10 is slightly delayed, the number of parts such as the filter 6 is reduced, so that the structure of the fixed in-core measuring device is simplified and the reliability is improved. Will improve. Other than that, the same operation and effect as those of the first embodiment can be obtained.

The fourth embodiment relates to claim 14 and, as shown in the circuit configuration diagram of FIG. 4, the input signal amplifying section 27 in the fixed in-core measuring device is provided with a switched capacitor 28 as a sequential switching means. Thus, a plurality of GT detection signals 2 input from a plurality of gamma ray thermometers 1 installed in the furnace are sequentially switched.

As in the third embodiment, a large number of filters 6 corresponding to the gamma ray thermometers 1 on the input side of the multiplexer 10 to which a plurality of GT detection signals 2 are input and a non-inverting amplifier 16b are provided. The capacitor 18 connected to the input side is not provided. The other parts have the same structure as that of the first embodiment.

As an operation of the above configuration, the GT detection signal 2 input from the plurality of gamma ray thermometers 1 is sequentially switched by the switched capacitor 28. At this time, the switched capacitor 28 is different from the multiplexer 10 in the signal. Since there is no wraparound, the isolation function between signals is improved.

Furthermore, since the number of parts such as a large number of filters 6 is reduced, the structure of the fixed core in-core measuring device is simplified. As a result, the reliability of the fixed core in-core measuring device is improved and the GT detection signal 2 can be accurately measured.

The fifth embodiment relates to claims 15 to 19, wherein a large number of gamma ray thermometers 1 in the fixed-type in-core measuring device are collectively arranged at the same place in the core. A calibration heater is provided side by side, and a predetermined power is supplied to the calibration heater from the calibration heater power source section to heat the gamma ray thermometer 1 to a predetermined temperature and to obtain the GT.
Perform calibration of detection signal 2.

As shown in the circuit diagram of FIG. 5, in the calibration heater power source section, a heater cable 31 having a cable resistance 30 is connected to the calibration heater 29, and a switching section 32 for power control is inserted. It is connected to the heater power supply 33. In addition, a calibration heater is provided in parallel with the calibration heater 29.
A heater side voltage monitor 34 is connected near 29, and a diode 35 and a power supply side voltage monitor 36 are connected on the output side near the switching unit 32 (claims 15, 16, 1).
7).

Next, the operation of the above configuration will be described. The power supplied from the heater power supply 33 is controlled to a predetermined voltage by the switching unit 32, and the heater cable 31
The heater 29 for calibration is heated by heating the heater 29 for calibration, and the GT detection signal 2 output from the gamma ray thermometer 1 (not shown) is calibrated.

At this time, the diode 35 suppresses the noise generated by the counter electromotive force due to the inductance when the switching section 32 malfunctions, and the calibration heater 29.
It is possible to prevent the voltage applied to the voltage from exceeding a predetermined value, improve noise immunity, and obtain high calibration accuracy.

Further, by monitoring the output voltage of the switching unit 32 by the power supply side voltage monitor 36, an accurate measured value can be obtained without being affected by the switching unit 32, and the current value can be calculated from this accurate measured value. By using, the accurate resistance value of the calibration heater 29 can be calculated. As a result, the GT detection signal 2 can be calibrated accurately by confirming the accurate value of the output of the calibration heater 29.

Further, when the resistance value of the calibration heater 29 is obtained from the heater current value and the heater power supply voltage, the resistance value of the output loop of the heater output can be known by correcting the heater cable resistance 30. The detection signal 2 can be accurately calibrated (claim 18).

Further, according to the heater side voltage monitor 34, the voltage applied to the calibration heater 29 can be accurately measured without being substantially affected by the cable resistance 30 of the heater cable 31, so that the GT detection signal 2 can be accurately calibrated. it can. In addition,
Both the voltage applied to the calibration heater 29 by the heater side voltage monitor 34 and the output voltage of the switching unit 32 can be accurately measured by the power source side voltage monitor 36.

Thus, by comparing the voltage applied to the calibration heater 29 and the output voltage value of the switching section 32, the cable resistance 30 of the heater cable 31 can be accurately calculated, so that the gamma ray thermometer 1 outputs it. The GT detection signal 2 can be accurately calibrated (claim 19).

The sixth embodiment relates to claim 20 and, as shown in the configuration diagram of FIG. 6, a cable for pulling out the GT detection signal 2 to the cable drawn from the gamma ray thermometer 1 and a calibration heater 29. There are those that supply power to. Both cables drawn together from the gamma ray thermometer 1 are configured to be separated into a signal cable 4 and a heater cable 31 in a cable separation box 38 provided after the multi-pin connector 37.

The operation of the above configuration is that the signal cable 4 for transmitting the GT detection signal 2 and the calibration heater 29 are used.
By separating the heater cable 31 for supplying power to the separation box 38 and later, each cable can be separated and laid in an orderly manner. Therefore, the signal cable 4 and the heater cable
The contact with 31 is prevented, the noise resistance is improved, and the GT detection signal 2 can be accurately calibrated.

[0067]

As described above, according to the present invention, the following effects can be obtained in the fixed core measuring device of the reactor power measuring device. (A) It is possible to accurately amplify the minute voltage signal which is the detection signal of the gamma ray thermometer. (B) Since the measurement time of detection signals from a large number of gamma ray thermometers can be shortened, rapid signal processing can be performed.

(C) The reliability of the fixed core in-core measuring device using the gamma ray thermometer is improved. (D) The noise resistance can be improved. (E) The detection signal of the gamma ray thermometer can be isolated from the external signal processing inside the furnace. (F) Since the measured value of each part is accurately obtained, the detected value and the calibration accuracy are improved.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an input signal amplifying unit in a fixed type in-core measuring device according to a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of an input signal amplification unit according to a second embodiment of the present invention.

FIG. 3 is a circuit configuration diagram of an input signal amplification unit according to a third embodiment of the present invention.

FIG. 4 is a circuit configuration diagram of an input signal amplification unit according to a fourth embodiment of the present invention.

FIG. 5 is a power supply circuit configuration diagram of a calibration heater according to a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram of a gamma ray thermometer and a cable according to a sixth embodiment of the present invention.

[Explanation of symbols]

1 ... Gamma ray thermometer, 2 ... Gamma ray thermometer detection signal (GT detection signal), 3, 30 ... Cable resistance, 4 ... Signal cable, 5, 21, 24, 27 ... Input signal amplification section, 6, 26 ... Filter , 7 ... Common power supply, 8 ... Separate power supply, 9 ... Disconnection detection circuit, 10 ... Multiplexer, 11 ... Reference voltage, 12 ... Signal common, 13, 22 ... Input amplification section, 14, 25 ... Differential amplification section, 15
... Isolation, 16a, 16b ... Non-inverting amplifier, 17 ...
GT common signal, 18 ... Capacitor, 19 ... Differential amplifier, 20
Output to signal processing unit, 23a, 23b ... Inverting amplifier, 28 ...
Switched capacitor, 29 ... Calibration heater, 31 ... Heater cable, 32 ... Switching unit, 33 ... Heater power supply, 34 ...
Heater side voltage monitor, 35 ... Diode, 36 ... Power supply side voltage monitor, 37 ... Multi-pin connector, 38 ... Cable separation box.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Ito 8 Shinsita-cho, Isogo-ku, Yokohama-shi, Kanagawa Incorporated company Toshiba Yokohama Office

Claims (20)

[Claims] 1. In a fixed core in-core measuring device using gamma ray thermometers arranged in the core of a nuclear reactor, a calibration heater is provided in the gamma ray thermometers, and detection signals from the plurality of gamma ray thermometers are provided. A fixed core in-core measuring device, wherein an input signal amplifying section to be amplified comprises a plurality of detection signal sequential switching means, an input amplifying section, a differential amplifying section, and isolation. 2. The fixed in-core measuring device according to claim 1, wherein in the input signal amplifying section, the sequential switching means is a multiplexer. 3. The fixed core according to claim 2, wherein a filter is provided for each of the plurality of gamma ray thermometers on the input side of the multiplexer, which is the sequential switching means, in the input signal amplifying section. Internal measuring device. 4. The fixed in-core measuring device according to claim 1, wherein, in the input signal amplifying unit, the input amplifying unit is a non-inverting amplifier having a high input impedance. 5. The fixed in-core measuring device according to claim 1, wherein in the input signal amplifying section, a capacitor is provided on a common signal input side of the input amplifying section. 6. The disconnection detection circuit is provided in a line of the plurality of gamma ray thermometers on the input side of the sequential switching means in the input signal amplification section.
The fixed-type in-core measurement device described in the above. 7. The input signal amplifying section supplies the bias reference potential of the disconnection detecting circuit provided on the input side of the sequential switching means from a separate power source insulated from the power source of the input signal amplifying section. The fixed in-core measuring device according to claim 6, which is characterized in that. 8. The input signal amplification section is provided with a reference potential or an internal signal common by a power supply independently provided inside, and automatically performs offset correction and gain adjustment of the input signal amplification section. The fixed in-core measuring device according to claim 1, which is characterized in that. 9. The input signal amplifying section, when calibrating a detection signal from the gamma ray thermometer, performs offset correction and gain adjustment of a target detection signal on demand after multiplexing by a sequential switching means. Item 1. A fixed core in-core measuring device according to Item 1. 10. The fixed in-core measuring device according to claim 1, wherein an amplification gain is fixed in the input signal amplifying section. 11. A fixed-type in-core measuring device characterized in that, in the input signal amplifying section, a gain in the input signal amplifying section is inversely calculated by an actual measurement value of a detection signal from the gamma ray thermometer by software means. . 12. The fixed in-core measuring device according to claim 1, wherein, in the input signal amplifying section, the input amplifying section is an inverting amplifier having a high input impedance. 13. The fixed in-core measuring device according to claim 1, wherein a filter is provided on the output side of the differential amplifier in the input signal amplifying section. 14. The fixed in-core measuring device according to claim 1, wherein the switching means in the input signal amplifying section is a switched capacitor. 15. A calibration heater power supply unit for supplying power to a calibration heater of a gamma ray thermometer, wherein the heater power supply is connected to the calibration heater by a heater cable via a switching unit for controlling the supplied power, and the switching is performed. Fixed core in-core measuring device characterized in that a diode is provided on the output side of the section. 16. The fixed in-core measuring device according to claim 15, wherein an output side voltage monitor is provided on the output side of the switching section in the calibration heater power supply section. 17. The fixed-type core measuring device according to claim 15, wherein a heater-side voltage monitor is provided near the calibration heater in the calibration heater power source section. 18. The resistance value of the heater cable is calculated by comparing the voltage values measured by the output side voltage monitor and the heater side voltage monitor in the calibration heater power supply section. 17. The fixed type in-core measuring device according to 17. 19. The calibration heater power supply section, when calculating the resistance value of the calibration heater from the heater current value and the heater power supply voltage, performs correction by the heater cable resistance value. Fixed type in-core measuring device. 20. In a gamma ray thermometer arranged in a plurality of cores, a cable separating box is provided in the middle of the signal cable and the heater cable drawn from the gamma ray thermometer to separate the signal cable and the heater cable. Fixed type in-core measuring device.