JPH08146187A - Nuclear reactor output area measuring device - Google Patents

Abstract

PURPOSE: To detect the abnormality of a LPRM detector quickly and without any increase in an operator's load by providing a gamma thermo detector for correcting the sensitivity of a local output monitor(LPRM) detector. CONSTITUTION: A LPRM detector 2 installed in a nuclear reactor 1 outputs electric current proportional to neutron flux in the periphery, and it is input to a LPRM measuring part 4 by a LPRM cable 3. The output of the measuring part 4 is input to a comparison determining part 8. On the other hand, a gamma thermo detector 5 is disposed in the vicinity of the detector 2. This is always fixed to execute the correction of sensitivity of the detector 2 in an output area. The output of the detector 5 is input to a gamma thermo measuring part 7 by a gamma thermo cable 6, signal-processed, and then input to the determining part 8. In the determining part 8, a LPRM measured value La which is output of the measuring part 4 is compared with a gamma thermo measured value Ga which is output of the measuring part 7, and if there is deviation more than fixed, a deviation warning 9 is issued.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor power range measuring apparatus for measuring the neutron flux of a nuclear reactor, for example.

[0002]

2. Description of the Related Art A conventional detector (LPRM local power range monitor, local power range monitor) installed in a nuclear reactor outputs a current proportional to the surrounding neutron flux. The in-reactor neutron flux is monitored by inputting this to the LPRM measurement unit with a cable and displaying it with the indicating means. LPR
The M detector is a nuclear fission counter, and it is necessary to provide a means for detecting disconnection or short circuit of the detector due to radiation irradiation or the like.
Therefore, one of the outputs of the LPRM measurement unit is input to the upper limit determination unit, compared with the value of the upper limit setting unit, and when it exceeds this, an upper limit alarm is issued. Further, the output of the LPRM measurement unit is also input to the lower limit determination unit and compared with the value of the lower limit setting unit, and when it is less than this, a lower limit alarm is issued. The soundness of the LPRM detector was confirmed by checking the upper and lower limit values as described above. The upper limit check mainly detects a short circuit due to a spark of the LPRM detector, and the lower limit detects an abnormality such as disconnection of the LPRM detector.

[0003]

The conventional system has the following problems.

Since the neutron flux in the reactor is small at the time of shutting down or starting up the reactor, the lower limit alarm is released.

As the output of the nuclear reactor increases, the neutron flux in the nuclear reactor increases, and if the LPRM detector is normal, the lower limit alarm will clear. However, LPRM detectors are arranged in various places in the reactor, and the timing at which the lower limit should be cleared is not constant (because the output distribution in the reactor is not uniform).

Therefore, there are the following problems in operating the nuclear reactor.

(1) There is no means to provide the operator with information as to which lower limit of which LPRM detector should be cleared during startup.

(2) In order to overcome the above, it is necessary for the operator to regularly confirm the lower limit clear. However, there are 172 LPRM detectors in total (1.1 million KWBWR)
Because of this, it took a lot of effort to check each one.

(3) In addition to detection by the upper and lower limit detectors, it is necessary to periodically check the indicated value in order to confirm the validity of the LPRM measured value, which is very laborious.

An object of the present invention is to overcome the above problems and provide an output range monitor having the following functions.

(1) It is possible to detect an abnormality in the LPRM detector promptly even in a low power region such as when the reactor is started up, and without increasing the burden on the operator.

(2) Not only detection of detector abnormalities such as upper and lower limits, but also validity of the LRPM measurement value can be promptly confirmed at startup.

[0013]

A reactor power range measuring apparatus of the present invention comprises an LPRM detector for measuring a neutron flux in a reactor, a gamma thermodetector for performing sensitivity calibration of the LPRM detector, and an LPRM detection. Output when the LPRM detection value detected by the detector and the gamma thermo detection value detected by the gamma thermo detector are compared, and when the comparison difference compared by the detection value comparison circuit exceeds a preset value. And an alarm circuit that operates. The reactor power range measuring apparatus according to claim 2 further includes a delay circuit that delays the output of the LPRM detection value detected by the LPRM detector, the delayed LPRM detection value output from the delay circuit, and the gamma thermodetector. And a detection value comparison circuit for comparing the detected value of gamma thermo detected in.

[0014]

In the reactor power range measuring apparatus of the present invention,
The neutron flux in the reactor is measured, the sensitivity of the LPRM detector is calibrated, the LPRM detection value detected by the LPRM detector is compared with the gamma thermo detection value detected by the gamma thermo detector, and the detection value comparison circuit is used. It is characterized in that it is output when the compared comparison difference exceeds a predetermined set value. In the reactor power range measuring apparatus according to claim 2, the output of the LPRM detection value detected by the LPRM detector is delayed, and the delayed LPR output from the delay circuit is output.
It is characterized in that the M detection value and the gamma thermo detection value detected by the gamma thermo detector are compared.

[0015]

EXAMPLE An example of the reactor power range measuring apparatus of the present invention will be described below. In FIG. 1, the LPRM detector 2 counts the fission of the neutron flux of the reactor 1 and detects the LPRM detection value L.
It is a fission counter that outputs. Gamma thermo detector 5
Is in the reactor 1 with the LPRM detector 2
Gamma thermo detection value G for calibrating the sensitivity of the detector 2
It is a fission counter that outputs. LPRM measuring unit 4 is L
It is connected to the PRM detector 2 and outputs the LPRM measurement value La according to the LPRM detection value L from the LPRM detector 2. The gamma thermo measurement unit 7 is connected to the gamma thermo detector 5 and outputs the gamma thermo measurement value Ga according to the gamma thermo detection value G from the gamma thermo detector 5. The comparison / determination unit 8 includes an LPRM measurement unit 4 and a gamma thermo measurement unit 7.
Connected to, and compares the LPRM measurement value La output from the LPRM measurement unit 4 and the gamma thermo measurement unit 7 with the gamma thermo measurement value Ga, and determines whether the comparison difference exceeds a predetermined set value. Circuit.

In the reactor power range measuring device of FIG.
The delay device 30 is a delay circuit connected between the LPRM measurement unit 4 and the comparison determination unit 8 to delay the output of the LPRM measurement value La output from the LPRM measurement unit to obtain the delayed LPRM measurement value Lb. The comparison / determination unit 8 is a detection value comparison circuit that compares the delayed LPRM measurement value Lb delayed by the delay device 30 with the gamma thermo measurement value Ga output from the gamma thermo measurement device 7.

That is, the LPRM detector 2 installed in the nuclear reactor 1 outputs a current proportional to the surrounding neutron flux. This is input to the LPRM measurement unit 4 via the LPRM cable 3. The output of the LPRM measurement unit 4 is input to the comparison / determination unit 8. On the other hand, a gamma thermo detector 5 is arranged near the LPRM detector 2 of the nuclear reactor 1. This was devised to perform sensitivity calibration of the LPRM detector 1 in the output region, and unlike the conventional TIP (movable in-core probe monitor), it is always fixed in the furnace.

The output of the gamma thermo detector 5 is input to the gamma thermo measuring section 7 by the gamma thermo cable 6 and subjected to signal processing, and then input to the comparison / determination section 8. The comparison / determination unit 8 compares the LPRM measurement value La, which is the output of the LPRM measurement unit 4, and the gamma thermo measurement value Ga, which is the output of the gamma thermo measurement unit 7, and issues a deviation alarm 9 when there is a deviation above a certain level.

FIG. 2 is an explanatory view showing the details of FIG.

The detector assembly 2A installed in the nuclear reactor 1 contains LPRM detectors 3a, 3b, 3c and 3d and gamma thermo detectors 5a, 5b, 5c and 5d.
These outputs are input to the LPRM measurement unit 4 and the gamma thermo measurement unit 7, respectively. Then, it is further input to these output comparison / determination units 8. The comparison / determination unit 8 has comparison / determination units 8a, 8b, 8c, 8d for the respective detectors, and the outputs are connected to the alarm means 9a, 9b, 9c, 9d.

The LPRM detectors 3a to 3d are fission counters and output a current proportional to the neutrons in the reactor. By measuring this with the LPRM measurement unit 4, the neutron flux in the reactor is monitored with good response, and a signal is output to the reactor protection system. However, since the sensitivity changes with age due to neutron irradiation, the gamma thermo detectors 5a to 5d are installed in the vicinity and the sensitivity is periodically calibrated by comparison with the values. Since the gamma thermo detector is a thermocouple and its sensitivity is small and its response is low, it cannot be used in a reactor protection system.

As the neutron flux in the reactor is increased at reactor startup, L
PRM detectors 3a to 3d and gamma thermo detector 5a to
The output of 5d increases. The comparison / determination units 8a to 8d constantly compare these outputs, and when there is a certain deviation or more, the warning means 9a to 9d issue an alarm.

Next, as the processing of the comparison / determination unit 8a, L
An alarm is issued when the deviation between the PRM measurement value La and the gamma thermo measurement value Ga exceeds a certain value.

However, when the gamma thermo measurement value Ga is less than the measurement lower limit, the alarm is automatically bypassed.

Further, as the processing of the comparison / determination units 8b to 8d, similarly, processing is performed by the deviation between the LPRM measurement values Lb, Lc, Ld and the gamma thermo measurement values Gb, Gc, Gd.

The present embodiment has the following effects.

(1) It is possible to realize early detection of an abnormality in the LPRM detector at the time of reactor shutdown and startup.

(2) Unnecessary LP at reactor shutdown and startup
Since the occurrence of the RM lower limit alarm can be suppressed, the burden on the operator is reduced.

(3) LPRM gain adjustment error and the like can be detected at an early stage.

(4) Conventionally, only the extreme failure detection of the LPRM lower limit and the upper limit was performed, but more delicate abnormality detection is possible. Gain adjustment is abnormal in the upper and lower limit range,
A sudden decrease in gain may be considered, but any of them can be detected in this embodiment.

(5) It is also possible to detect an abnormality on the gamma thermo detector side.

FIG. 3 shows another embodiment of the present invention. LPR
The output of the M measurement unit 4 is delayed by the delay device 30, and this value and the output of the gamma thermo measurement unit 7 are input to the comparison determination unit 8 for comparison. This is because the response of the gamma thermo measurement system is LPR.
Since it is slower than the M measuring system, it is possible to prevent the false alarm from being generated due to the difference in response between the two when the furnace output changes.

[0033]

According to the present invention, it is possible to realize early detection of an abnormality in the LPRM detector when the reactor is stopped or started up.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a reactor power range measuring apparatus showing an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating details of FIG.

FIG. 3 is a configuration diagram showing another embodiment.

[Explanation of Codes] 2 ... LPRM Detector 4 ... LPRM Measuring Section 5 ... Gamma Thermo Detector 7 ... Gamma Thermo Measuring Section 8 ... Comparison Judgment Section

Claims (2)

[Claims] 1. A LPRM for measuring neutron flux in a nuclear reactor
A detector, a gamma thermo detector for calibrating the sensitivity of the LPRM detector, and an LP detected by the LPRM detector.
A detection value comparison circuit for comparing the RM detection value and the gamma thermo detection value detected by the gamma thermo detector, and an alarm output when the comparison difference compared by the detection value comparison circuit exceeds a predetermined set value. A reactor power range measuring device comprising a circuit. 2. The LPRM detected by the LPRM detector
A delay circuit for delaying the output of the detection value; and a detection value comparison circuit for comparing the delayed LPRM detection value output from the delay circuit and the gamma thermo detection value detected by the gamma thermo detector. Reactor power range measuring device.