JP2001021654A - Radiation measurement system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an erroneous counting due to noise and to perform accurate counting by counting only the detection signal of neutron flux. SOLUTION: A signal from a neutron flux detector 1 is amplified by a preamplifier 2, its waveheight is selected by a waveheight-selecting circuit 3, and signals being equala to or less than a selection level are cut as noise. When the width of a pulse being selected by a waveform-processing circuit 11 is equal to or more than a set pulse width, it is outputted as a pulse. When the width is less than the set pulse width, it is cut as a noise. A count circuit 5 counts the pulses for counting and performs reading/displaying by a signal processing system 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation measurement system for measuring radiation by counting pulse signals generated by a radiation detector.

[0002]

2. Description of the Related Art FIG. 18 is a block diagram of a neutron flux measuring system, in which (a) shows the entire configuration and (b) shows a circuit diagram of a waveform shaping circuit. In the figure, 1 is a neutron flux detector, 2 is a preamplifier, 3 is a wave height selection circuit, 4 is a waveform shaping circuit, 5 is a counting circuit, and 6 is a signal processing system. The waveform shaping circuit 4 includes a resistor R and a capacitor C as shown in FIG.
, And generates a constant pulse signal when there is an input pulse.

[0003] Next, the operation will be described with reference to the waveform processing time chart of FIG. When a neutron flux is detected in the neutron flux detector 1, a pulse is generated, amplified by the preamplifier 2, and sent to the wave height sorting circuit 3. As shown in FIG. 19A, the wave height sorting circuit 3 performs wave height sorting on the voltage signal to remove noise caused by the electric circuit and influences other than the intended signal (FIG. 19B). .

That is, the pulse height selection circuit 3 measures a pulse peak value generated by detecting a neutron flux by the neutron flux detector 1 in advance to set a peak height selection level, and sets a peak height value exceeding the peak height selection level. Are output as a neutron flux detection pulse to the waveform shaping circuit 4, and a pulse having a peak value equal to or lower than the peak selection level is not output as noise.

The crest shaping circuit 4 comprises a monostable multivibrator 26 for converting a crest-selected signal into a constant pulse signal (pulse signal having a constant pulse width T) as a trigger signal, as shown in FIG. The output of the pulse signal is sent to the counting circuit 5. The counting circuit 5 counts the pulses of the fixed pulse signal whose waveform has been shaped, and sends the counted value to the signal processing system 6. Then, the measurement result of the neutron flux is obtained in the signal processing system 6.

[0006]

Since the conventional neutron flux measurement system is configured as described above, if the peak value of the noise is higher than the peak selection level, the noise and the neutron flux signal are separated. There is a problem that the counting circuit 5 counts a signal other than the intended signal, which causes erroneous counting and malfunction.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. Due to the influence of noise, erroneous counts, erroneous alarms, erroneous operations, etc. are inevitably caused by factors other than the intended fluctuation of the neutron flux level. The purpose of the present invention is to provide a reliable system that does not cause a problem.

[0008]

(1) A radiation measurement system according to the present invention is a radiation measurement system for measuring radiation by counting pulse signals detected by a radiation detector, wherein the pulse signal has a predetermined peak value. When the pulse width is equal to or larger than the set value, a predetermined pulse is output and counted.

(2) In a radiation measurement system for measuring radiation by counting pulse signals detected by a radiation detector, the pulse signal has a pulse height not less than a predetermined peak value and a pulse width within a set range. When there is, a predetermined pulse is outputted and counted.

(3) In the radiation measuring system for counting the pulse signal detected by the radiation detector and measuring the radiation, the pulse signal may be set within a predetermined peak value range.
If the pulse width is equal to or larger than the set value, a predetermined pulse is output and counted.

(4) In the radiation measuring system for measuring the radiation by counting the pulse signals detected by the radiation detector, the pulse signal may be set within a predetermined peak value range.
In addition, a predetermined pulse is output and counted if the pulse width is within the set range.

(5) In the above (2), if the pulse signal has a pulse height not less than a predetermined peak value and a pulse width exceeding a set range, an alarm output is sent.

(6) In the above (3) or (4), when the pulse signal exceeds a predetermined peak value range, an alarm output is transmitted.

(7) In any one of the above items (1) to (6), the means for obtaining a predetermined pulse to be counted may be a pulse having a pulse width in a period from the start of counting to a predetermined count value. An output counter is provided, and when an output for counting is input to the counter, counting is started and a pulse having the pulse width is output.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a neutron flux measurement system according to Embodiment 1 of the present invention, FIG. 2 is a circuit diagram of a waveform processing circuit, and FIG. 3 is a time chart of waveform processing. In FIG. 1, 1 is a neutron detector, 2 is a preamplifier, 3 is a wave height sorter,
11 is a waveform processing circuit, 5 is a counting circuit, and 6 is a signal processing system. 2, the waveform processing circuit 11 includes a reference clock 21, a counter 22, a decoder 23, a JK flip-flop 24, a D flip-flop 25, and a monostable multivibrator 26 including a resistor R and a capacitor C.

Next, the operation will be described. (1) The pulse signal generated in the neutron flux detector 1 is amplified by the preamplifier 2, and the noise signal and the neutron flux signal are separated from the voltage signal by the peak value sorting circuit 3 based on the peak value (FIG. 3A). (B)). (2) The selection pulse signal from the wave height selection circuit 3 is input as a count permission signal of the counter 22 operated by the reference clock 21, and the counter 22 stops after a certain count (stop value Na count) (FIG. 3 (c)). .

(3) The count value of the counter 22 is input to the decoder 23. When the count value reaches the set value N1 (the set time t1 has elapsed from the start of counting), the decoder 23
The decoder 23 sends out a decoder output having a clock pulse width, and sets the JK flip-flop 24 to the set state (from L to H) (FIGS. 3D, 3E, and 3F).

(4) When the JK flip-flop 24 is in the set state (H) and the pulse height selection pulse signal shown in FIG. 3B disappears (from H to L), the D flip-flop 25 outputs (from L to H). Then, a trigger signal is applied to the monostable multivibrator 26 (FIGS. 3F and 3G). Further, at this time, when the peak selection pulse signal shown in FIG. 3B disappears (from H to L), the JK flip-flop 24 is reset (H
To L).

(5) The monostable multivibrator 26 generates a pulse having an output pulse width T in response to the trigger signal (FIG. 3 (h)). (6) The D flip-flop 25 is reset by the input to the CLR terminal from the monostable multivibrator 26, and returns to the initial state. (7) Since the pulse whose pulse width does not reach t1 (in the case of noise other than the neutron flux in FIG. 3) is not counted up to the set value N1, it is not output from the decoder 23 and
(E) The following waveforms are not output.

As described above, in the first embodiment, the pulse signal is not output from the waveform processing circuit 11 unless the output of the wave height selection circuit 3 continues for the set time t1 or more. Malfunction can be prevented, and a highly reliable device can be obtained.

Embodiment 2 FIG. In the first embodiment, the case where the counting pulse is output when the signal of the predetermined peak level or higher continues for the set time t1 or more has been described. However, in the second embodiment, the signal of the predetermined peak level or higher is output. This is a signal that outputs a counting pulse when the signal continues within a set time range.

FIG. 4 is a circuit diagram of a waveform processing circuit of the neutron flux measurement system according to the second embodiment of the present invention.
Is a time chart of the waveform processing. In FIG. 4, when the count value of the counter 22 reaches two set values from the decoder 23, the output is input to the J terminal and the K terminal of the JK flip-flop 24.

The operation when a large noise other than the neutron flux such as extraneous noise enters the neutron flux measurement system will be described with reference to FIG. (1) When noise wider than the neutron flux is detected (FIG. 5 (a)), a pulse having a large pulse width is output from the pulse height selection circuit 3a (FIG. 5 (b)). (2) The counter 22 starts operating (FIG. 5C), and the decoder 23 outputs when the count of the counter 22 reaches the set value N1, and outputs when the count of the counter 22 reaches the set value N2 (FIG. 5).
(D) (e)). That is, the set times t1 and t2 are set by the two set values N1 and N2, and thus t3 is set.

(3) The JK flip-flop 24 has a C
Since the LR terminal is H, a pulse having a pulse width of time t3 is output by two pulses of the decoder 23 (FIG. 5).
(F)). (4) Even if there is an output from the JK flip-flop 24, the D flip-flop 25 inputs to the C terminal (FIG. 5B).
Does not change because H remains unchanged at H (FIG. 5
(G)). Even if the C terminal input changes from “H” to “L”, the D terminal input (FIG. 5F) is not output because it is L at that time.

As described above, a pulse having a pulse width exceeding t2 can be regarded as noise and erroneous counting can be eliminated. Further, pulses having a pulse width of t1 or less are regarded as noise and are not output for counting, as in the case of the pulse width of t1 or less in the first embodiment. And t1 <pulse width <
If it is a pulse of t2, it is the same as the case of t1 <pulse width in FIG. 3 of the first embodiment, and outputs a pulse for counting.

As described above, according to the second embodiment,
If the signal has a signal higher than the wave height selection level and has a pulse width not shorter than the set time t1 and not longer than t2, the counting signal is output. Therefore, white noise due to the preamplifier and noise due to an external electric circuit are output. Erroneous counting due to the above can be prevented.

Embodiment 3 In the first embodiment, the case where the counting pulse is output when the signal having the predetermined peak level or more continues for the set time t1 or more has been described. However, in the third embodiment, the high and low two peak level sorting levels are output. A signal within a range is output when the signal continues for a set time or longer.

FIG. 6 is a block diagram of a neutron flux measuring system according to a fourth embodiment of the present invention, and FIG. 7 is a circuit diagram of a waveform processing circuit of the neutron flux measuring system according to the fourth embodiment of the present invention. 8 is a time chart of the waveform processing. As shown in the configuration of FIG. 6, a wave height sorting circuit 3a with a low wave height sorting level and a wave height sorting circuit 3 with a high wave height sorting level
b. In the waveform processing circuit 11 shown in FIG. 7, the output from the peak selection circuit 3a is input as "input L", and the output from the peak selection circuit 3b is input as "input H".

Next, the operation will be described with reference to FIG. (1) First, t1 is set. As in the first embodiment, t1 is set so as to distinguish the noise and white noise from the preamplifier from the neutron flux signal (FIG. 8B).
(D)). (2) When noise having a wide width and a high wave height other than the neutron flux enters (FIG. 8A), the wave heights are sorted by the wave height sorting circuits 3a and 3b (FIGS. 8B and 8C).

(3) The counter 22 and the decoder 23 operate according to the peak selection output (L) of FIG.
Although not shown, the operation is the same as that shown in FIGS. Then, the decoder 23 outputs (FIG. 8)
(D)). (4) The JK flip-flop 24 receives the output from the decoder 22 as a J terminal input, and the K terminal as "input H",
Since both become H, an inverted output H is sent out (FIG. 8).
(E)). (5) Next, when the decoder output changes from H to L, the JK flip-flop 24 is inverted and the output changes from H to L (FIG. 8E).

(6) The D flip-flop 25 is a JK
Even if there is an output from the flip-flop 24, the C terminal input (FIG. 8 (b)) remains unchanged at H, so that no output is made (FIG. 8 (f)). Even if the C terminal input changes from “H” to “L”, the D terminal input (FIG. 8E) is not output since it is L at that time.

As described above, pulses having a pulse width exceeding the pulse height selection level (H) can be regarded as noise, and erroneous counting can be eliminated. Further, pulses having a pulse width of t1 or less are regarded as noise and are not output for counting, as in the case of the pulse width of t1 or less in the first embodiment. Then, the pulse height selection level is a signal between L and H, and the pulse width is t1.
If so, a counting pulse is output.

As described above, according to the third embodiment,
Only signals having a peak level within a predetermined range are selected, and when the width of the signal is equal to or longer than the set time t1, an output for counting is sent out, so that large noise such as noise due to an external electric circuit is generated. Erroneous counting can be prevented.

Embodiment 4 In the first embodiment, the case where the counting pulse is output when the signal of the predetermined peak level or higher continues for the set time t1 or more has been described. However, in the fourth embodiment, two high and low peak level selection levels are output. A counting pulse is output when the signal is within the range and the width of the signal is within the range of two set times. That is, the second embodiment and the third embodiment are combined.

FIG. 9 is a circuit diagram of a waveform processing circuit of the neutron flux measurement system according to the fourth embodiment of the present invention.
0 is a time chart of the waveform processing. Although the configuration diagram of the neutron flux measurement system is the same as that of FIG. 6 of the third embodiment, it is omitted. However, as shown in FIG. 6, a peak height sorting circuit 3a having a low peak sorting level and a peak height sorting circuit 3b having a high peak sorting level are shown in FIG. And

The waveform processing circuit shown in FIG.
Is input as “input L”, and the output from the wave height selection circuit 3b is input as “input H”. Also, the count value of the counter 22 from the decoder 23 is changed to two set values (N
1, N2), the output is input to the J and K terminals of the JK flip-flop 24. 2
7 is a NOT circuit and 28 is an AND circuit.

The operation when a large noise other than the neutron flux such as extraneous noise enters the neutron flux measurement system will be described with reference to FIG. (1) When noise wider than the neutron flux is detected (FIG. 10 (a)), a pulse having a large pulse width is output from the pulse height selection circuit 3a (FIG. 10 (b)). (2) The counter 22 and the decoder 23 operate and are not shown in FIG. 10, but their operations are the same as those in FIGS. 5 (c) and 5 (d). That is, as shown in FIGS. 5C and 5D, the decoder 23 outputs when the count of the counter 22 reaches the set value N1, and further outputs when the count of the counter 22 reaches the set value N2 (FIG. 10).
(E)). That is, the set times t1 and t2 are obtained by the two set values N1 and N2, and as a result, the time t3 is obtained. The time t2 is set so as to satisfy “t2 <T2 + ta”, and the time t1 is set so as to distinguish the white noise and the neutron flux signal as in the first embodiment.

(3) On the other hand, the logic circuit composed of the AND circuit 27 and the NOT circuit 28 is as follows according to the input. When the sorting level is below L, between L and H, or above H, NOT output HHL AND output LHL Figure 10 (d) is a waveform diagram when H is above H.

(4) The JK flip-flop 24 has a C
Since the LR terminal is L, even if two pulses of the decoder 23 are input, they are not output. (FIG. 10
(F)). (5) Therefore, the D flip-flop 25 does not operate nor output (FIG. 10 (g)). Even if the C terminal input changes from "H to L", the D terminal input (FIG. 10 (f)) is not output because it is L.

(6) If the peak selection level is between H and L, there is no "input H" and only "input L" is input. Therefore, the output of the AND circuit becomes H, and J-
The K flip-flop 24 enters a state where it operates according to the inputs of the J and K terminals. (7) In this state, J terminal input (decoder output at t1)
When there is, the D flip-flop 25 outputs. The waveforms are similar to those shown in FIGS. 3 (e), 3 (f), 3 (g) and 3 (h). (8) In the above state (6), if the width of the signal waveform is equal to or less than t1 or equal to or more than t2, no count output is generated as described in the second embodiment.

As described above, according to the fourth embodiment,
By combining the second embodiment and the third embodiment, only signals having a peak level within a predetermined range are selected,
When the width of the signal is equal to or more than the set time t1 and equal to or less than t2, the counting signal is output, so that erroneous counting due to white noise due to the preamplifier, noise due to the external electric circuit, or the like can be prevented.

Embodiment 5 FIG. In the fifth embodiment, a counter is used instead of a monostable multivibrator that outputs a counting pulse signal. The monostable multivibrator using the resistor R and the capacitor C is economically inexpensive, but has a problem that the pulse width variation range is wide depending on the use environment. However, the use of a counter reduces the pulse width variation range. Can be.

FIG. 11 is a circuit diagram of a waveform processing circuit according to a fifth embodiment of the present invention, and 29 is a counter. FIG.
Is a waveform time chart.

Next, the operation will be described with reference to FIG. (1) FIGS. 12A to 12C are the same as the operations of FIGS. 3A to 3F of the first embodiment. (2) JK flip-flop 24 is set (H)
12 (b) disappears (H
To L) and the D flip-flop 25 outputs (from L to H) (FIGS. 12C and 12D). At this time, FIG.
2 (b) pulse height selection pulse signal disappears (from H to L)
Then, the JK flip-flop 24 is reset (from H to L).

(3) The counter 26 starts at the same time as the output of the D flip-flop 25 (FIG. 12 (e)), and is output from the counter 26 (FIG. 12 (f)). (4) When the count value of the counter 26 reaches the set value N3, the counting is stopped and the output is also stopped (FIG. 12 (e)).
(F)). (5) The reset signal from the counter 26 is input to the CLR terminal of the D flip-flop 25, and the D flip-flop 25 is reset and returns to the initial state. In this way, the counter output is sent out as a counting pulse and counted.

As described above, according to the fifth embodiment, the width of the output pulse for counting can be set to an arbitrary pulse width accurately according to the set value, and the pulse width due to environmental change such as temperature change can be obtained. Fluctuations can be reduced. In addition, in FIGS. 4, 7 and 9 of the second to fourth embodiments, a counter can be applied instead of the monostable multivibrator.

Embodiment 6 FIG. In the sixth embodiment, a notification is made when noise is detected. FIG.
Numeral 3 is a circuit diagram of a waveform processing circuit for obtaining an alarm output due to noise, in which an alarm D flip-flop 30 is added to FIG. 4 of the second embodiment. FIG. 15 is a timing chart of waveform processing when noise is input, and FIG. 16 is a timing chart of waveform processing when a neutron flux detection signal is input.

Next, the operation when noise is input will be described with reference to FIG. (1) FIGS. 14A, 14B, and 14C are the same as the operations in FIGS. 3A to 3F of the first embodiment, and a description thereof will not be repeated. (2) When the output of the JK flip-flop 24 changes from H to L, the alarm D flip-flop 30 outputs an alarm signal (FIG. 14D).

Next, the operation when a neutron flux detection signal is input will be described with reference to FIG. (1) The processing of the waveforms of FIGS. 15A to 15F is the same as the processing of the waveforms of FIGS. 3A to 3F of the first embodiment, and a description thereof will be omitted. (2) The alarm D flip-flop 30 is driven by the output of “H to L” of the JK flip-flop 24 being input to the C terminal, but the output of the wave height discrimination circuit becomes “H to L” and the CLR is output. Since it is input to the terminal and is cleared and only a very short pulse signal is output, it is not output as an alarm signal (FIG. 15 (g)). In this way, when a noise wider than the neutron flux signal is input, it can be notified.

As described above, according to the sixth embodiment, the noise source can be identified by notifying the noise, and the noise countermeasures can be implemented at an early stage, and the reliability of the system can be improved. Can also be improved.

Embodiment 7 FIG. In the seventh embodiment, an alarm output is added to the third embodiment. FIG. 16 shows a waveform processing circuit according to the seventh embodiment.
When the signal “input H” having a peak value exceeding
The signal of "input H" is transmitted as an alarm output, assuming that the signal is noise. As described above, the seventh embodiment is different from the sixth embodiment.
It has the same effect as.

Embodiment 8 FIG. In the eighth embodiment, an alarm output is added to the fourth embodiment. FIG. 17 shows a waveform processing circuit according to the eighth embodiment.
When the signal “input H” having a peak value exceeding
The signal of "input H" is transmitted as an alarm output, assuming that the signal is noise. As described above, the eighth embodiment is different from the sixth embodiment.
It has the same effect as.

Embodiment 9 FIG. In each of the above embodiments, a system for counting a neutron flux signal has been described, but a radiation signal other than a neutron flux may be counted.

[0054]

As described above, according to the radiation measuring system of the present invention, since a signal due to radiation and a signal due to noise are distinguished, accurate measurement can be performed and erroneous counting can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram of a neutron flux measurement system according to Embodiment 1 of the present invention.

FIG. 2 is a circuit diagram of a waveform processing circuit according to the first embodiment of the present invention.

FIG. 3 is a timing chart showing waveform processing according to the first embodiment of the present invention;

FIG. 4 is a circuit diagram of a waveform processing circuit according to a second embodiment of the present invention.

FIG. 5 is a timing chart showing waveform processing according to the second embodiment of the present invention.

FIG. 6 is a block diagram of a neutron flux measurement system according to a third embodiment of the present invention.

FIG. 7 is a circuit diagram of a waveform processing circuit according to a third embodiment of the present invention.

FIG. 8 is a timing chart showing waveform processing according to the third embodiment of the present invention.

FIG. 9 is a circuit diagram of a waveform processing circuit according to a fourth embodiment of the present invention.

FIG. 10 is a timing chart showing waveform processing according to a fourth embodiment of the present invention.

FIG. 11 is a circuit diagram of a waveform processing circuit according to a fifth embodiment of the present invention.

FIG. 12 is a timing chart showing waveform processing according to the fifth embodiment of the present invention.

FIG. 13 is a circuit diagram of a waveform processing circuit for transmitting an alarm output according to a sixth embodiment of the present invention.

FIG. 14 is a timing chart showing waveform processing according to the sixth embodiment of the present invention.

FIG. 15 is a timing chart showing waveform processing according to the sixth embodiment of the present invention.

FIG. 16 is a circuit diagram of a waveform processing circuit for transmitting an alarm output according to a seventh embodiment of the present invention.

FIG. 17 is a circuit diagram of a waveform processing circuit for transmitting an alarm output according to an eighth embodiment of the present invention.

FIG. 18 is a block diagram of a conventional neutron flux measurement system.

FIG. 19 is a timing chart showing conventional waveform processing.

[Explanation of symbols]

Reference Signs List 1 neutron flux detector 2 preamplifier 3, 3a, 3b wave height sorting circuit 5 counting circuit 6 signal processing system 11 waveform processing circuit 21 reference clock 22, 29 counter 23 decoder 24 J-K flip-flop 25 D flip-flop 26 monostable Multivibrator 27 NOT circuit 28 AND circuit 30 D flip-flop for alarm

Claims (7)

[Claims] 1. A radiation measurement system for measuring radiation by counting pulse signals detected by a radiation detector,
A radiation measurement system, wherein a predetermined pulse is output and counted when the pulse signal has a pulse height equal to or greater than a predetermined peak value and a pulse width equal to or greater than a set value. 2. A radiation measurement system for measuring radiation by counting pulse signals detected by a radiation detector,
A radiation measurement system, wherein a predetermined pulse is output and counted when the pulse signal is equal to or greater than a predetermined peak value and has a pulse width within a set range. 3. A radiation measurement system for measuring radiation by counting pulse signals detected by a radiation detector,
A radiation measurement system, wherein a predetermined pulse is output and counted when the pulse signal is within a predetermined peak value range and has a pulse width equal to or larger than a set value. 4. A radiation measurement system for measuring radiation by counting pulse signals detected by a radiation detector,
A radiation measurement system, wherein a predetermined pulse is output and counted when the pulse signal has a pulse width within a predetermined peak value range and a pulse width within a set range. 5. The radiation measurement system according to claim 2, wherein an alarm output is transmitted when the pulse signal has a pulse height equal to or more than a predetermined peak value and a pulse width exceeding a set range. Radiation measurement system. 6. The radiation measurement system according to claim 3, wherein an alarm output is sent out when the pulse signal exceeds a predetermined peak value range. 7. A radiation measuring system according to claim 1, wherein the means for obtaining a predetermined pulse to be counted is a pulse having a pulse width in a period from the start of counting to reaching a predetermined count value. A radiation measurement system comprising: a counter for outputting a pulse; and when a counter output is input to the counter, counting is started and a pulse having the pulse width is output.