JPH07101238B2 - Wide area neutron flux measurement and monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention measures and displays the neutron flux in the start-up system region and the intermediate system region in a reactor pressure vessel, and displays the average of the reactor. The present invention relates to a wide area neutron flux measurement and monitoring device that generates a control rod withdrawal prevention signal and a scrum signal when a transient phenomenon such as an abnormal increase in output or local output is shown.

(Prior Art) In general, the neutron flux level in a reactor pressure vessel has a wide measurement range (for example, a boiling water reactor has an 11-digit measurement range), and it is technically difficult to measure with one measurement means. Is difficult. For this reason, conventionally, three measuring means are used in combination.

The first measurement means is in the low neutron flux range (start-up system area). In this area, the reactor output is proportional to the count rate. The level is being measured. The second measuring means is based on the intermediate neutron flux range (intermediate region). In this region, the reactor power is proportional to the root mean square value of the fluctuation components of the output signal, and the Campbell method is used for the measurement. That is, it is measured by the square of the effective value of the AC component of the detector output signal. The third measuring means is based on the high neutron flux range (output region), in which the direct current from the detector is measured, paying attention to the fact that the reactor output is proportional to the direct current.

In these measuring means, four detectors for the starting system area, eight detectors for the intermediate system area, and 100 to 200 detectors for the output system area are installed in the core, and the detectors are detected for each system. It is connected to a circuit to measure the neutron flux level.

In addition, the handling method when the above-mentioned measuring means is used as a safety system of a nuclear reactor is also different. Generally, the time T until the output becomes e (base of natural logarithm) times is defined as a period and is used as an index of output change. In the start-up system, the time rate of change of neutron flux is directly measured by a differentiating circuit, and when this value exceeds a certain value, a control rod withdrawal prevention signal is output. In the case of the intermediate system, since the range switching linear display system is adopted as the output display system, the scrum signal is output when the indication value for each range becomes a certain value or more.
In the output system, the output instruction value is a constant value, for example, the rated value of 12
The scrum signal is output when the output exceeds 0%. Here, the start system and the intermediate system prevent a sudden output increase,
In addition, the output system is monitored so that the rated output is not exceeded to ensure reactor safety.

FIG. 5 is a block diagram of a conventional neutron flux measurement / monitoring device in the startup system region. The neutron flux measurement and monitoring device in this start-up system region comprises a detector (fission counter) 1 for detecting a neutron flux in the start-up system region, a pulse system amplifier 2 for amplifying the output signal of this detector 1, and this pulse. Start-up system output processing circuit 3 including a pulse height discrimination circuit that discriminates the signal amplified by the system amplifier 2 into a signal pulse and a noise component, and a counter that measures the counting rate of the signal pulse.
And a differentiation circuit for differentiating the output of the startup system output processing circuit 3 to directly obtain the time change rate of the neutron flux, and comparing the time change rate of the neutron flux obtained by this differentiation circuit with the set value. And a period circuit 4 that outputs a control rod withdrawal inhibition signal when the time change rate of the neutron flux is larger than the set value, and a display 5 that displays the time change rate of the neutron flux.

FIG. 6 is a block diagram of a conventional neutron flux monitoring device in the intermediate region. The neutron flux monitoring device in the intermediate system region includes a detector 6 for detecting the neutron flux in the intermediate system region, a Campbell system amplifier 7 for amplifying an output signal of the detector 6, and an amplification by the Campbell system amplifier 7. An intermediate output processing circuit 10 having a squaring circuit 8 for squaring the generated signal and a smoothing circuit 9 for smoothing an output signal of the squaring circuit 8, and a display 11 for displaying the output of the intermediate output processing circuit 10. And a comparison circuit 12 that compares the output of the intermediate system output processing circuit 10 with a set value and generates a scrum signal when the output of the intermediate system output processing circuit 10 is equal to or more than the set value. It should be noted that the squaring circuit 8 has a built-in range switching amplifier, and the operator of the plant checks the output level of the display 11 and outputs an appropriate range switching signal from the comparison circuit 12 so as not to generate a scrum signal. While inputting, increase the reactor power.

Due to such a difference in characteristics, it is considered impossible to perform the measurement by the pulse system and the measurement by the Campbell system with the same measuring device, and the output has been displayed by different devices before.

FIG. 7 shows a conventional wide area neutron flux measurement and monitoring device developed as a means for solving the above problems. This conventional wide area neutron flux measurement and monitoring device includes a wide area system detector 20 having a fission counter and the like, and a wide area system detector 20.
Wide-area preamplifier 21 in which the pulse system amplifier 22 capable of high frequency band amplification and the Campbell system amplifier 23 capable of low noise intermediate frequency band amplification are connected in parallel, and the pulse system amplifier A start-up output processing circuit 3, a period circuit 4, and an indicator 5 connected to the output side of 22 in the same manner as in FIG. 5, and a square connected to the output side of the Campbell amplifier 23 in the same manner as in FIG. An intermediate output processing circuit 10 having a circuit 8 and a smoothing circuit 9, a comparison circuit 12, and a display 11 are provided. The pulse system amplifier 22 and the Campbell system amplifier 23 perform frequency separation by an appropriate combination of an input impedance (not shown) and a coupling capacitor. That is, in the starting system, only the high frequency component is amplified by the pulse system amplifier 22, and in the intermediate system, only the intermediate frequency band component is amplified by the Campbell system amplifier 23. All of the S / N characteristics in can be satisfied, and each amplifier gain can be set to an appropriate value. Therefore, it is possible to detect the start-up system neutron flux and the intermediate system neutron flux with one wide-area detector 20.
The measurement and monitoring means after 21 are no different from the neutron flux measurement and monitoring means in the starting system area shown in FIG. 5 and the neutron flux measurement and monitoring means in the intermediate system area shown in FIG. 6, respectively. , Contains the same problem. That is,
Since the period circuit 4 in the start-up system region includes a differentiating circuit that directly obtains the time change rate of the neutron flux, the output signal greatly changes due to a slight fluctuation such as circuit noise, and the system is likely to become unstable. Further, since the output signal fluctuates significantly due to the noise component carried on the neutron flux signal, the circuit becomes complicated to remove this noise component. When a positive reactivity is added due to pulling out of the control rod, etc., the reactor shows a phenomenon that the output power suddenly increases in a short time and then increases at a stable rate of increase. being called. However, since the power rise time is extremely short and the power rise does not increase so much, it is not a phenomenon that poses a particular problem to reactor safety,
If there is a differentiating circuit, this short-time input signal is differentiated, so that the time change rate of the neutron flux, which is the output signal, rapidly increases. Therefore, the time change rate of the neutron flux becomes higher than the set value, the period circuit may output the control rod withdrawal prevention signal, and the presence of the differential circuit causes a decrease in operating performance. Therefore, it is necessary to take a complicated circuit configuration because it is necessary to remove the influence of the prompt jump. Also, in the neutron flux measurement and monitoring device in the intermediate region, the operator
Since it is necessary to check the output level of the reactor with, and to increase the reactor output by switching to an appropriate range so that a scrum signal does not occur, it is possible to reduce the burden on the operator and save labor in operation. There wasn't.

(Problems to be Solved by the Invention) The present invention does not separately measure the neutron flux in the start-up system region or the intermediate system region, automatically measures and monitors these neutron fluxes, and the influence of prompt jumps and the like. It is an object of the present invention to provide a wide-area neutron flux measurement and monitoring device that does not have a complicated circuit configuration for removing the neutrons.

[Structure of Invention]

(Means and Actions for Solving Problems) The present invention relates to a wide-area neutron flux detector that detects a neutron flux in a start-up system region in a reactor pressure vessel and a neutron flux in an intermediate-system region, and a wide-range neutron flux detector. A wide band neutron flux signal detected by the neutron flux detector is frequency band separated, and a pulse system amplifier to which the high frequency component separated by this frequency band is input and a Campbell system amplifier to which the intermediate frequency component is input are provided. A wide area preamplifier provided, and a start system output processing circuit for inputting the output of the pulse system amplifier to perform wave height discrimination, and measuring a count rate and outputting the wave height discriminated signal as a start system signal φ _a. , it receives the output signal of the Campbell system amplifier, and the intermediate system output processing circuit for outputting a mean square value of this input as a intermediate system signal phi _b smoothes the activation system output processing circuit An output comparison circuit outputted the activation system signal phi _a of the count rate outputs a switching instruction signal when above predetermined set value Te, based on the switching instruction signal is output from the output comparison circuit, wherein when the counting rate of the activation system signal phi _a of more than the set value is passed through the intermediate system signal phi _b, when the count rate of the activation system signal phi _a is less than the set value, the activation system signal phi _a A switching device that switches the connection so that it passes, a first amplifier, a first low-pass filter, and a first signal comparison circuit,
Only when the count rate of the start-up signal φ _a is less than the set value is connected to the start-up output processing circuit by the switch, the start-up signal φ _a is the first amplifier and the first low-pass filter. The signal φ _a ′ after passing through and the starting system signal φ _a are compared in the first signal comparison circuit,
First period measurement and monitoring means for outputting a control rod withdrawal prevention signal when the magnitude of the activation system signal φ _a is greater than or equal to the magnitude of the signal φ _a ′, _a second amplifier, a second low pass filter, and A second signal comparison circuit, which is connected to the intermediate system output processing circuit by the switch when the count rate of the starting system signal φ _a is equal to or more than the set value, and the intermediate system output signal φ _b is the second compared with the amplifier and a second low-pass filtered signal phi _b 'and the intermediate system signal phi _b of the second signal comparison circuit after passing the magnitude is the signal of the intermediate system signal phi _b phi _b Second period measurement and monitoring means for outputting a control rod withdrawal prevention signal when the size is equal to or greater than ‘
A third amplifier, a third low-pass filter and a third signal comparison circuit, arranged in parallel with the second period measurement and monitoring means, when the count rate of the activation system signal φ _a is equal to or more than the set value. The intermediate system output processing circuit is connected to the intermediate system output processing circuit by the switch, and the intermediate system signal φ _b is passed through the third amplifier and the third low-pass filter to output the signal φ _c ′ and the intermediate system signal φ _b . The magnitude of the intermediate signal φ _b is compared by the third signal comparison circuit, and the magnitude of the intermediate signal φ _b is the signal φ _c ′.
And a third period measuring and monitoring means for generating a scrum signal when the value is equal to or larger than the above value.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of a wide area neutron flux measurement and monitoring apparatus according to the present invention. This wide-area neutron flux measurement and monitoring device separates a wide-area neutron flux detector (for example, a nuclear fission counter) 30 installed in a nuclear reactor and an output signal of the wide-area neutron flux detector 30 into frequency bands, A pulse system amplifier 32 to which the separated high frequency component is input, and a wide area preamplifier 31 having a Campbell system amplifier 33 to which an intermediate frequency component is input, and pulse height discrimination of the output of the pulse system amplifier 32, The output signal of the startup system output processing circuit 34 that measures the counting rate and outputs it as the startup system signal φ _a and the output signal of the Campbell system amplifier 33 are input, and the root mean square value of this input is smoothed and output as the intermediate system signal φ _b. Intermediate output processing circuit 35 and output comparison circuit 40 that outputs a switching instruction signal when the count rate of the startup system signal φ _a output by the startup system output processing circuit 34 is equal to or greater than a preset set value.
If, on the basis of the switching instruction signal output from the output comparison circuit 40, start system when the counting rate of the signal phi _a of more than the set value is passed through an intermediate system signal phi _b, count rate activation system signal phi _a Is less than the set value, the switch 41 for switching the connection so as to pass the start-up signal φ _a and the first amplifier 37.
_a , a first low-pass filter 38 _a , and a first signal comparison circuit 39 _a, and is connected to the startup system output processing circuit 34 by the switch 41 only when the count rate of the startup system signal φ _a is less than the set value. The start-up signal φ _a is compared with the signal φ _a ′ after the start-up signal φ _a has passed through the first amplifier 37 _a and the first low-pass filter 38 _a and the start-up signal φ _a in the first signal comparison circuit 39 _a , First period measurement and monitoring means 36 which outputs a control rod pull-out prevention signal when the magnitude of the starting system signal φ _a is equal to or greater than the magnitude of the signal φ _a ′.
and _a, is connected to the first Periodo measurement monitoring means 36 _a,
An indicator 42a for displaying a start-up signal, _a second amplifier _37b ,
The second low pass filter 38 _b and the second signal comparison circuit 3
9 _b , the starter signal φ _a is connected to the intermediate system output processing circuit 35 by the switcher 41 when the count rate is equal to or more than the set value, and the intermediate system output signal φ _b outputs the second amplifier 37 _b and the second amplifier 37 _b . The signal φ _b ′ after passing through the low-pass filter 38 _b and the intermediate system signal φ _b are compared by the second signal comparison circuit 39 _b , and the magnitude of the intermediate system signal φ _b is equal to or larger than the magnitude of the signal φ _b ′. Second period measurement and monitoring means 36 _b that outputs a control rod pull-out prevention signal when
When, a second indicator 42 _b of the counting rate of the activation system signal phi _a displays an intermediate system signal phi _b when more than the set value, the third amplifier 37 _c, a third low-pass filter 38 _c and comprising a third signal comparison circuit 37 _c, arranged in parallel with the second Periodo measurement monitoring means 36 _b, an intermediate system output processing circuit by switching unit 41 when the counting rate of the activation system signal phi _a of more than the set value The intermediate signal φ _c (= φ _b ) connected to the signal 35 is passed through the third amplifier 37 _c and the third low-pass filter 37 _c , and the intermediate signal φ _c ′ and the intermediate signal φ _c are converted to the third signal. compared with the comparison circuit 37 _c, which includes the intermediate system signal third Periodo measurement monitoring means for generating a scram signal when phi magnitude of _c is greater than or equal the magnitude of the signal phi _c '36 _c. Further, the pulse system amplifier 32 performs frequency separation by a suitable combination of the impedance R ₁ and the coupling capacitor C ₁ , and the Campbell system amplifier 33 performs frequency separation by a suitable combination of the impedance R ₂ and the coupling capacitor C ₂ . A signal corresponding to the neutron flux level in the startup system region is output from the startup system output processing circuit 34 as the startup system signal φ.
_{The signal} is output as a, and the intermediate system output processing circuit 35 outputs a signal corresponding to the intermediate system conjunctive child bundle level as the intermediate system signal φ _b . Period measurement and monitoring means 36 _a , 36
The input signals φ _a , φ _b , and φ _{c at b} and 36 _c and the input signals φ _a , φ _b , and φ _c are respectively amplified by the amplifiers 37 _a and 3
The relationship with the signals φ _a ′, φ _b ′, φ _b ′ after passing through 7 _b , 37 _c and the low pass filters 38 _a , 38 _b , 38 _c is expressed by the following equation.

Here, i = a, b, c φ i (t): input signal Periodo measurement monitoring means _{36 i φ i '(t)} : amplifiers 37 _i and the low-pass filter 38 the signal has passed through the _i G _i: amplifier 37 _i Gain λ _i : 1 / RC _i RC _i : time constant of low-pass filter 38 _i Equation (1) can be analytically solved when the neutron flux rises at period τ _i. Given in.

(Φ _i (t) = φ _i (o) e ^{t / τ} _i ) Furthermore, by utilizing the fact that φ _i ′ = φ _{i at} t = ∞, RC _i = (G _i −1) · τ _i …… ( 3) relationship constant RC _i and the gain G _i when next low-pass filter 38 _i is provided. Therefore, when RC _i and G _i are set in the period measurement / monitoring means 36 _{i, the} period τ _i is given, and when a control rod withdrawal prevention signal or a scrum signal is to be issued at a certain period (for example, 10 seconds), it corresponds to that. You can set the combination of RC _i and G _i .

Furthermore, the setting period τ S of this period measurement and monitoring means 36 _i
when the output increase of the furnace had happened to Periodo τ _i for the _{i φ i}
When the time T _i required until ≧ φ _i ′ is determined, T _i is Since it is given by, G _i is uniquely determined. This G _i and (3)
If RC _i is determined by using the formula, “a period measurement and monitoring means for issuing a control rod withdrawal prevention signal or scrum signal after T _i time from the time when the output of period τ _i rises” will be given.

For example, if RC _i = 10 seconds and G _i = 2, the trip setting period τ _i is τ _i = 10 seconds from equation (3), and if the reactor power rise occurs at period τ Si = 9 seconds, (4) From the formula, T _i = 15
A trip signal is output after a second.

As described above, the wide area neutron flux measurement and monitoring apparatus according to the present invention can monitor whether or not the period of the reactor power increase is equal to or less than the set period without directly differentiating the neutron flux signal.

FIG. 2 is a diagram showing a response example when a control rod pull-out prevention signal is generated in the activation system area. Reference numeral 43 _a indicates a starting system signal phi _a, numeral 44 _a is Periodo measuring monitoring means 36 _a
The signal φ _a ′ after passing through the amplifier 37 _a and the low-pass filter 38 _a of FIG. 4 is shown, and the control rod pull-out prevention signal is generated at the intersection point 46.

FIG. 3 is a diagram showing a response example when the control rod pull-out prevention signal and the scrum signal are generated in the intermediate system region. Reference numeral 43 _b indicates the intermediate signal φ _b , reference numeral 44 _b indicates the signal φ _b ′ after passing through the amplifier 37 _b and the low-pass filter 38 _b , which are components of the period measuring and monitoring means 36 _b , and the reference numeral 45.
Amplifier is a component of Periodo measurement monitoring means 36 _c 37 _c
The signal φ _c ′ after passing through the low-pass filter 38 _c is shown, and the control rod pull-out prevention signal is generated at the intersection point 46 and the scrum signal is generated at the intersection point 47.

FIG. 4 is a graph showing changes with time of the input signal of the period measuring and monitoring means and the signal after passing through the amplifier and the low pass filter which are the constituent elements of the period measuring and monitoring means in the intermediate region. Reference numeral 48 indicates an input signal of the period measuring and monitoring means, and reference numeral 49 indicates a signal after passing through the amplifier and the low-pass filter.

〔The invention's effect〕

The wide area neutron flux measurement and monitoring apparatus according to the present invention can automatically measure and automatically monitor the neutron flux in the start-up system region or the intermediate system region, and an amplifier, a low-pass filter and a signal without using a differentiating circuit in the period measurement and monitoring means. Since the comparator circuit is provided, the configuration is extremely simple, and the effects of prompt jump and the like can be eliminated by appropriately selecting the gain of the amplifier and the time constant of the low-pass filter.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a wide area neutron flux measurement and monitoring device according to the present invention, and FIG. 2 is a diagram showing an example of a response when a control rod withdrawal prevention signal is generated in an activation system region. FIG. 3 is a diagram showing a response example when the control rod pull-out prevention signal and the scrum signal are generated in the intermediate system region,
FIG. 4 is a graph showing changes with time in the input signal of the period measuring and monitoring means and the signal after passing through the amplifier and the low-pass filter which are the constituent elements of the period measuring and monitoring means in the intermediate region, and FIG. FIG. 6 is a block diagram of a neutron flux measurement and monitoring device in the start-up region, FIG. 6 is a block diagram of a conventional neutron flux measurement and monitoring device in the intermediate region, and FIG. 7 is a block diagram of a conventional wide area neutron flux measurement and monitoring device. . 30 …… Wide area neutron flux detector, 31 …… Wide area preamplifier, 32
...... Pulse system amplifier, 33 …… Campbell system amplifier,
34 ...... activation system output processing circuit, 35 ...... intermediate system output processing _{circuit, 36 a, 36 b, 36} c ...... Periodo measurement monitoring means, 37 _a, 37 _b, 3
7 _c …… Amplifier, 38 _a , 38 _b , 38 _c …… Low pass filter, 3
9 _a , 39 _b , 39 _c …… Signal comparison circuit, 40 …… Output comparison circuit, 41
...... Switch, 42 _a , 42 _b ...... Display.

Claims (1)

[Claims] 1. A wide-area neutron flux detector for detecting a neutron flux in a start-up system region in a reactor pressure vessel and a neutron flux in an intermediate-system region, and a wide-range neutron flux detected by this wide-range neutron flux detector. A wide-area preamplifier including a pulse system amplifier to which the high frequency component separated by the frequency band separation is input, and a Campbell system amplifier to which the intermediate frequency component is input, and the pulse system For inputting the output of the amplifier for use in the pulse height discrimination, measuring the count rate, and outputting the signal subjected to the pulse height discrimination as the activation system signal φ _a , and inputting the output signal of the Campbell amplifier and then, counting rate of the intermediate system output processing circuit for smoothing the mean square value of the input and output as an intermediate system signal phi _b, the starting system the activation system signal outputted by the output processing circuit phi _a An output comparator circuit for outputting a switching instruction signal when the above setting value set in advance, based on the switching instruction signal is output from the output comparison circuit, the counting rate of the activation system signal phi _a of more than the set value when passed through the intermediate system signal phi _b, wherein when the count rate of the activation system signal phi _a is less than the set value, a switching device for switching a connection to pass the activation system signal phi _a, the first An amplifier, a first low-pass filter, and a first signal comparison circuit,
Only when the count rate of the start-up signal φ _a is less than the set value is connected to the start-up output processing circuit by the switch, the start-up signal φ _a is the first amplifier and the first low-pass filter. The signal φ _a ′ after passing through and the starting system signal φ _a are compared in the first signal comparison circuit,
First period measurement and monitoring means for outputting a control rod withdrawal prevention signal when the magnitude of the activation system signal φ _a is greater than or equal to the magnitude of the signal φ _a ′, _a second amplifier, a second low pass filter, and A second signal comparison circuit, which is connected to the intermediate system output processing circuit by the switch when the count rate of the starting system signal φ _a is equal to or more than the set value, and the intermediate system output signal φ _b is the second compared with the amplifier and a second low-pass filtered signal phi _b 'and the intermediate system signal phi _b of the second signal comparison circuit after passing the magnitude is the signal of the intermediate system signal phi _b phi _b Second period measurement and monitoring means for outputting a control rod withdrawal prevention signal when the size is equal to or greater than ‘
A third amplifier, a third low-pass filter and a third signal comparison circuit, arranged in parallel with the second period measurement and monitoring means, when the count rate of the activation system signal φ _a is equal to or more than the set value. The intermediate system output processing circuit is connected to the intermediate system output processing circuit by the switch, and the intermediate system signal φ _b is passed through the third amplifier and the third low-pass filter to output the signal φ _c ′ and the intermediate system signal φ _b . The magnitude of the intermediate signal φ _b is compared by the third signal comparison circuit, and the magnitude of the intermediate signal φ _b is the signal φ _c ′.
And a third period measurement / monitoring means for generating a scrum signal when the magnitude is equal to or larger than the above.