JPH0225159B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wide area neutron output monitoring device using a neutron detector.

Conventionally, a neutron measuring device using a neutron detector has been used as a monitoring device for nuclear reactor output. This neutron measurement device employs three types of methods depending on the neutron flux range in order to measure neutron flux over a wide range.

In other words, in the low neutron flux range, a pulse counting method (starting system) that measures pulses from a neutron detector;
In the intermediate neutron flux range, the Campbell method is used to measure the root mean square of the fluctuation component of the detector output (intermediate system), and in the high neutron flux range, the method is used to measure the DC component of the detector output signal (output system). It monitors the output of the furnace.

Of these, a wide range neutron output monitoring device (wide range monitor) was devised that measures the pulse counting method (startup system) and Campbell method (intermediate system) using the same detector (patent application 1983). −
No. 20083).

This wide-area neutron output monitoring system had advantages such as being able to reduce the number of detectors and simplifying the structure of the reactor.

FIG. 1 shows an embodiment of a conventional wide-area neutron output monitoring device.

The signal from the neutron detector 1 is amplified by a preamplifier 2 and input to a wide range monitor 3.

This wide range monitor 3 is composed of a pulse counting system 4 and a Campbell measuring system 10. The signal from the neutron detector 1 is processed by the pulse counting method and the Campbell method by the respective signal processing circuits 5, 6, 7 and 11, 12, 13, and then input to the trip circuits 8 and 14. .

The trip circuits 8 and 14 compare the trip signals with reference signals, and output trip signals such as low level and high level to the control rod withdrawal prevention system 9 and the like.

In such a wide-area neutron output monitoring device (wide-range monitor), although it is a wide-area neutron device that uses the same detector, the monitor side is essentially divided into two systems, the conventional startup system and intermediate system. It is no different from the separate neutron monitoring equipment. That is, as the reactor output increases, the pulse count rate of the startup system increases and the Campbell output of the intermediate system reaches a range where it has sufficient linearity, and the level of the Campbell system 10 remains low until the monitoring function is switched from the pulse system 4 to the Campbell system 10. After switching, the high-level trip signal of pulse system 4 must be bypassed manually or automatically, and the reactor output control and startup method using the conventional two-system monitoring system using two detectors has been changed. It was not a huge improvement.

Furthermore, the wide-area neutron monitoring system (wide range monitor) monitors the operating status of the neutron detector to check for abnormalities in the neutron detector while the reactor is operating, similar to the previous two systems of monitoring systems, startup system and intermediate system. It is difficult to judge. In other words, if there is an abnormality in the mode in which no output signal is generated due to a failure in the detector or system, reactor control can be maintained on the safe side by low-level trip signals in the startup system and intermediate system, but the neutron detector It is not possible to diagnose abnormalities.

In the monitor that monitors the reactor output, the function to perform online abnormality diagnosis, including the decrease in sensitivity and changes in characteristics of the neutron detector, which is the heart of the monitor, is useful for confirming the soundness of the reactor output monitoring function. This is a very important function, but in the past, it was used in non-online situations such as measuring the plateau characteristics or pulse height distribution of the detector at a constant furnace output, etc. to check the health of the detector and the deterioration of the characteristics. It had the disadvantage that there was only one method available.

SUMMARY OF THE INVENTION Therefore, the present invention provides a wide-area neutron output monitoring device that is equipped with an online abnormality diagnosis function for neutron detectors and can automatically switch the output monitoring function and alarm output function from a pulse counting method to monitoring using the Campbell method. With the goal.

The present invention is characterized by a neutron detector that detects the neutron flux of a nuclear reactor, and a pulse measurement method that measures the detection signal output from the neutron detector using a pulse measurement method when the reactor output is in the startup region. a Campbell measurement system circuit that is connected to the neutron detector together with the pulse measurement system circuit and measures a detection signal from the neutron detector using the Campbell method when the reactor output is in an intermediate region; An overlap between the outputs of the pulse measurement system circuit and the Campbell measurement system circuit is detected, and when the furnace output is within this overlap range, the Campbell measurement system circuit is selected if the furnace output is increasing, and the Campbell measurement system circuit is selected if the furnace output is decreasing. If the overlap detection arithmetic processing circuit that switches between the two circuits to select the pulse measurement system circuit and the overlap detection arithmetic processing circuit do not detect the overlap, the monitoring function determines that there is an abnormal state and triggers the trip. The present invention is characterized in that it includes a trip circuit that outputs a signal, and an alarm signal generating means that generates an alarm signal when it is determined that the monitoring function is in an abnormal state.

Hereinafter, the present invention will be explained based on illustrated embodiments.

<Configuration> FIG. 2 shows an embodiment of the present invention.

The output signal from the detector 1a is sent to the preamplifier 2a.
The signal is amplified and input to the wide range monitor 3a. The wide range monitor 3a includes a pulse counting system 4a and a Campbell measuring system 10 that are substantially similar to the pulse counting system 4 and the Campbell measuring system 10 in FIG.
It is composed of a. The signal from the preamplifier 2a is processed by the pulse counting system 4a and the Campbell measuring system 10a using the pulse counting method and the Campbell method, respectively. And pulse counting system 4a and Campbell measuring system 10a
The output signals of the two systems are input to the trip circuit 8a, and are also input to the trip circuit 8a via an arithmetic processing circuit 15a for detecting overlap. In the trip circuit 8a, the trip signal is compared with a reference signal, and a low level or high level trip signal is output to the control rod withdrawal prevention system 9a.

<Use> Next, the operation of the present invention will be explained with reference to FIGS. 2 and 3. First, a general explanation of the output signals from the two measurement methods will be given. In the overlap detection arithmetic processing circuit 15a, the pulse system 4a
and the output signal of the Campbell system 10a are compared and determined. That is, each signal from a healthy detector is 4
Signal processing is performed in each measurement system of a and 10a.

The relationship between the output signal C of the pulse system, the output signal V of the Campbell system, and the furnace output is shown in FIG. In the wide-area neutron output monitoring system, the range in which the linearity of the output signal proportional to the reactor output overlaps by about two orders of magnitude in the reactor output (Fig. 3 OV).

That is, according to the signal based on the output of a healthy detector, the value of the rising portion of the signal V of the Campbell system, that is, the value of the rising portion from a nearly constant value determined by α and α noise, noise of the circuit system, etc. is the predetermined value C ₁ of the pulse system counting rate (usually around 10 ⁴ cps)
It corresponds to a constant value V ₁ below the furnace power P ₁
±△V ₀ . Here, △V ₀ indicates the measurement error precision.

On the other hand, as the number of output pulses from the detector increases, the pulse system signal C begins to become saturated as the number of circuits decreases, etc., and remains at an almost constant value C ₂ ±△C ₀ above the furnace output P ₂ +△P ₂ . saturate. Here, △C ₀ indicates measurement error precision. At this time, the Campbell system output signal has a predetermined value V ₂ +ΔV ₂ .

Therefore, when the output increases, the furnace output becomes P ₁ in the overlap detection calculation circuit 15a shown in FIG. 2, and the signal of the canvas signal remains below V ₁ +△V ₀ until the pulse system signal C reaches a predetermined value C ₁ . When C ₁ +△C ₁ is reached, V ₁ +△V ₁
By detecting the above two points, it can be confirmed that the Campbell system output V is rising in a healthy manner as the pulse system counting rate increases.

Further, when the furnace output increases and reaches P ₂ and the Campbell system output signal V reaches a predetermined value V ₂ , the pulse system output signal C becomes C ₂ −△C ₂ or more, and V It can be confirmed that the pulse system is normally saturated by detecting two points: when C reaches ₂ + △V ₂ or more, and C becomes less than C ₂ - △C ₀ .

Furthermore, when the output is decreasing, the normality of the overlap can be determined by performing the above-described determination in the order of the upper limit side and the lower limit side.

In addition, by setting in advance a difference corresponding to two digits of the furnace output as a reference signal for comparison with the prescribed signal output of each system on the lower limit side and upper limit side of these overlaps, it is possible to adjust the output to the prescribed furnace output. It is possible to check whether there is a linearity overlap equivalent to two digits.

The configuration of the arithmetic processing circuit can be easily configured by combining a well-known voltage comparison circuit, a voltage comparison circuit, and an appropriate logic circuit.

Appropriate values can be set for the predetermined signal values, etc., which serve as a reference for comparison of the respective systems, through initial testing and calibration of the detector and circuit systems.

In the above, if a trip signal indicating an abnormality in the detector is outputted to the trip circuit 8a,
If a predetermined overlap cannot be obtained due to some abnormality in the detector, it is possible to immediately issue an abnormality signal.

By the way, by using the overlap detection function on the lower limit side of this overlap detection function,
When the output increases, when the pulse system reaches a predetermined output, it can be determined that the Campbell system has started up normally, and the alarm output can be bypassed and connected automatically. That is, until the Campbell system starts up normally, the low level alarm output of the Campbell system is bypassed, and the pulse system short period, high level, etc. alarm outputs are connected.

When the pulse system reaches a predetermined level and the Campbell system starts up normally, the alarm output of the pulse system is bypassed, and the low level alarm output of the Campbell system is connected.

Conversely, when the output is decreasing, the alarm output can be switched from the Campbell system to the pulse system in the same way. That is, after confirming that the overlap on the upper limit side has been properly removed, switching is automatically performed at a predetermined level.

In either case, switching the monitoring function is usually done in two steps.
This can be done at any set point within a region where both systems can have a linear overlap of about an order of magnitude.

If you simply want to automatically switch the alarm output,
It is only necessary to detect that a predetermined set value has been reached and switch the alarm output from the system being used at the time of switching to another system, regardless of whether the output increases or decreases.

In the present invention, the automatic switching can be performed while checking the operation of the detector. Further, after automatic switching of the monitoring function at the set point, if an abnormality is detected on either the lower limit side or the upper limit side, it is possible to issue an alarm of operational abnormality regardless of the presence or absence of an alarm output.

Modification Example 1 In the above-mentioned embodiment, the output signal values of each system corresponding to the two-digit difference in furnace outputs P ₁ and P ₂ are used as comparison reference signals when comparing and determining the overlap of the output signals of the two systems. I mentioned setting it up.

In addition, regarding the pulse system output signal C and the Campbell system output signal V, the pulse system output signal C
To match the output signal V ₁ of the Campbell system when the output signal V 1 reaches a predetermined value C ₁ by adjusting the gain, and determine whether the output signals of both systems rise while remaining consistent as the output increases thereafter. It is also possible to detect overlaps in output linearity.

In this case, signal processing is required to unify the linearity characteristics of both systems to either linear scale or logarithmic scale. Of course, this processing may be performed independently by the overlap detection arithmetic processing circuit 15a in addition to the output to the display. In this case, of course, it is possible to determine whether or not there is overlap within a predetermined range by receiving the range position signal and the set level signal.

Conversely, when the overlap cannot be taken, that is, when the mismatch width of the output signals of the pulse system and the canvas signal exceeds a predetermined setting standard, the signal level of either the pulse system or the canvas signal is set to a predetermined reference voltage. It is also possible to detect abnormalities by comparing with the values.

Modification 2 In addition, the output signals of both systems are input to a computer for calculation processing, and the output linearity of both systems with respect to the reactor output is displayed on a graphic display, etc., and the linearity overlap corresponding to Fig. 3 is calculated. It is possible to judge at a glance whether the data is within the range, and at the same time, by digitally displaying the number of digits of overlap, it is possible to clearly judge whether there is an abnormality. Also, if the range where the output linearity does not overlap is displayed in different colors, it will be easier to judge.

<Effects> As described above, according to the present invention, in the case of an output abnormality due to a conventional failure mode, it can be outputted as an alarm output as in the conventional case, and even if the detector is operating almost normally, the detector characteristics It is possible to detect abnormalities due to deterioration etc. with high sensitivity at an early stage and output an alarm. In other words, it is possible to detect a sign of failure and issue a warning.

This is because even if the output signals from both measurement methods have linearity and operate almost normally in the overlap detection arithmetic processing circuit, an abnormality can be determined if an overlap of a predetermined number of digits is not achieved in the end.

Furthermore, it is possible to detect an abnormality in a detector during reactor operation at the early stage of the abnormality, and it is easy to take measures such as making a plan to replace the detector at the next inspection, which improves the reliability of reactor operation. Useful for improvement. Note that depending on whether the abnormality occurs on the upper limit side or the lower limit side of the overlap, it is possible to make some inferences about the nature of the abnormality in the detector.

Further, in addition to determining an abnormality by checking a two-digit overlap range, an alarm can be output when only an abnormality is detected on either the upper limit side or the lower limit side.

In particular, by detecting an abnormality on the lower limit side, it is possible to determine an abnormality in the detector in a region where the reactor output is low, which is effective for safe operation of the reactor. If the alarm output on the lower limit side is performed in two stages, that is, if the comparison standard value has two stages, large and small, and the judgment is made, if the abnormality is large, the increase in the furnace output will be prohibited, and if it is small, the increase in the furnace output will be prohibited. , an alarm is output, but the output can be increased.

In this way, it is possible to diagnose abnormalities in the operating state of the detector without interfering with the safe operation of the reactor, and it is possible to detect and judge abnormalities with high sensitivity not only in extreme failure modes but also in the pre-failure stages. can.

Furthermore, according to the present invention, after detecting and confirming that the overlap between the output signals of the two methods has started to be corrected normally at the lower limit side or the upper limit side, the overlap is detected when the output signal level has reached the appropriate furnace output. In the arithmetic processing circuit, the input signal to the trip circuit (from the pulse system to the Campbell system)
It is possible to automatically output a switching signal for bypassing the pulse system alarm of the trip output signal, or a switching signal for connecting the signal for the alarm system alarm output.
Driving can be automated and simplified, eliminating the need for troublesome driving operations.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional wide area neutron output monitoring device, Fig. 2 is a block diagram showing a wide area neutron output monitoring device according to the present invention, and Fig. 3 is a diagram showing the overlap of output signals by the pulse counting method and the Campbell method according to the present invention. It is a graph showing a detection example. 1, 1a... Neutron detector, 2, 2a... Preamplifier, 3, 3a... Wide area neutron output monitoring device, 4, 4
a... Pulse measurement system circuit, 5... Wave height analysis circuit, 6...
Logarithmic conversion circuit, 7... DC amplifier circuit, 8, 8a... Trip circuit, 9, 9a... Control rod withdrawal prevention system circuit,
10, 10a...Cambell measurement system circuit, 11...gain switching circuit, 12...phase inversion circuit, 13...root mean square circuit, 14...trip circuit, 15a...overlap detection arithmetic processing circuit.

Claims (1)

[Claims] 1. A neutron detector that detects the neutron flux of the nuclear reactor; and a pulse that measures the detection signal output from the neutron detector using a pulse measurement method when the reactor output is in the startup region. a measurement system circuit; a Campbell measurement system circuit that is connected to the neutron detector together with the pulse measurement system circuit and measures a detection signal from the neutron detector using the Campbell method when the reactor output is in an intermediate region; detecting an overlap between the respective outputs of the pulse measurement system circuit and the Campbell measurement system circuit, and selecting the Campbell measurement system circuit if the furnace output is increasing while the furnace output is within this overlap range;
An overlap detection arithmetic processing circuit that switches between both circuits so as to select the pulse measurement system circuit if the pulse is falling, and if the overlap detection arithmetic processing circuit does not detect the overlap, the monitoring function is in an abnormal state. A high-frequency neutron output monitoring device comprising: a trip circuit that determines that the monitoring function is in an abnormal state and outputs a trip signal; and an alarm signal generating means that generates an alarm signal when it is determined that the monitoring function is in an abnormal state.