JP3750924B2 - Radiation monitor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiation monitor used in a nuclear power plant or the like.
[0002]
[Prior art]
In a nuclear power plant or the like, a radiation monitor using a semiconductor detector has been conventionally used. FIG. 7 is a block diagram showing a configuration of a radiation monitor using a conventional semiconductor detector. In FIG. 7, 1 is a first semiconductor detector, 2 is a second semiconductor detector, 3 is a pulse height discrimination counter circuit, 4 is a calculator, 5 is a memory, and 6 is a display.
[0003]
The first semiconductor detector 1 and the second semiconductor detector 2 absorb the energy of the incident radiation, convert it into an analog signal pulse having a voltage peak proportional to the absorbed energy, and output it. The outputs of the first semiconductor detector 1 and the second semiconductor detector 2 are merged and input to the wave height discrimination counting circuit 3. The crest discrimination counting circuit 3 receives analog signal pulses and counts crest pulses having a predetermined discrimination level or higher. The arithmetic unit 4 controls the wave height discrimination counting circuit 3, the memory 5 and the display 6, reads the count value of the wave height discrimination counting circuit 3 at a fixed period, stores it in the memory 5, and the arithmetic program stored in the memory 5 And the calculation such as the counting rate is executed with the data, and the calculation result is stored in the memory 5 and displayed on the display 6. Here, as the first semiconductor detector 1 and the second semiconductor detector 2, for example, a CdTe semiconductor sensor or a PIN (P layer, depletion layer, N layer structure) type Si semiconductor sensor is used. One or more.
[0004]
FIG. 8 shows signal waveforms at A, B, C, and D shown in FIG. In FIG. 8, a1 and a7 are analog signal pulses as a result of detection of radiation by the first semiconductor detector 1, a3 is internal noise of the first semiconductor detector 1, and a5 and a6 are external noise. Similarly, b4 and b8 are analog signal pulses as a result of detection of radiation by the second semiconductor detector 2, b2 is internal noise of the second semiconductor detector 2, and b5 and b6 are external noise. The outputs of the first semiconductor detector 1 and the second semiconductor detector 2 merge and are input to the wave height discrimination counting circuit 3.
[0005]
For this reason, the waveform a5 and b5 and a6 and b6 of the simultaneous timing are respectively added to the crest values to become c5 and c6. Waveforms a1, a3, a7, b2, b4, and b8 of non-simultaneous timing are crest values as they are, and are c1, c3, c7, c2, c4, and c8, respectively. In the wave height discrimination counting circuit 3, analog signal pulses c1, c4, c7, c8 exceeding the wave height discrimination level and external noise c5, c6 exceeding the wave height discrimination level are digital pulses d1, d4, d7, d8, d5, d6, respectively. Is converted to and counted. The internal noise d3 of the first semiconductor detector 1 and the internal noise d2 of the second semiconductor detector 2 are excluded from the count because the crest value is small.
[0006]
[Problems to be solved by the invention]
In the conventional radiation monitor described above, the semiconductor detectors used for the first and second semiconductor detectors 1 and 2 have a smaller peak value of the output signal pulse than the scintillation detector, and are intended to increase the detection sensitivity. Since external noise is amplified when a plurality of detectors are connected in parallel, etc., measurement with noise eliminated as a countermeasure against external noise has been a problem.
[0007]
The present invention has been made in order to solve the problems associated with the above-described conventional example, and an object thereof is to obtain a radiation monitor capable of preventing external noise from being mixed.
[0008]
[Means for Solving the Problems]
The radiation monitor according to the present invention includes first and second semiconductor detectors each having one or a plurality of semiconductor sensors that detect radiation and output analog signal pulses, and are provided in two groups. A non-simultaneous counting circuit that receives analog signal pulses output from the first and second semiconductor detectors, and counts pulses having a peak value equal to or higher than a predetermined discrimination level and satisfying a condition of non-simultaneous timing; It is provided.
[0009]
Also, a coincidence counting circuit for inputting analog signal pulses output from the first and second semiconductor detectors, counting pulses having a peak value equal to or higher than a predetermined discrimination level and satisfying a simultaneous timing condition, and The non-simultaneous counting circuit and the non-simultaneous output pulses and simultaneous output pulses output from the coincidence counting circuit are counted at regular intervals, respectively, and the average non-synchronized value calculated from the current non-simultaneous clock value and the previous non-simultaneous clock value or the previous measured value The clock value is compared as a reference value, and when the ratio K is less than a predetermined value, the current measurement value is calculated and output from the current non-same clock value or the latest non-same clock value including the current time, and the ratio When K is equal to or greater than a predetermined value, the current clock value is compared with the current non-clock value, and when the ratio P is less than the predetermined value, the current clock value or the latest multiple non-clock values including this time To this time When the ratio P is equal to or greater than a predetermined value, the current non-same clock value is discarded, and the previous non-same clock value or the latest multiple non-same clock values including the previous time are calculated. This time, it has an arithmetic unit that calculates and outputs the measured value.
[0010]
Further, the computing unit issues a failure alarm when the number of times of discarding the non-clock value this time continues for a predetermined number of times.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to the drawings.
1 is a block diagram showing a configuration of a radiation monitor according to Embodiment 1 of the present invention. The same parts as those of the conventional example shown in FIG. As a new code, reference numeral 7 denotes a non-coincidence counting circuit. The non-coincidence counting circuit 7 inputs analog signal pulses output from the first semiconductor detector 1 and the second semiconductor detector 2 and outputs a peak value. Are counted above a predetermined discrimination level and satisfy the condition of non-simultaneous timing. Each of the first semiconductor detector 1 and the second semiconductor detector 2 includes one or more semiconductor sensors. Needless to say, the condition for discriminating the wave height of the non-simultaneous counting circuit 7 may be that the wave height value is not less than a predetermined lower limit level and not more than the upper limit level, or may be a wave height analysis condition obtained by multiplying the wave height values.
[0012]
FIG. 2 shows signal waveforms at A, B, and E shown in FIG. 1. In the non-coincidence counting circuit 7, analog signal pulses a1, a7, b4, and b8 have peak values equal to or higher than the discrimination level and non-simultaneous timing. It counts because it satisfies the condition. The external noises a5 and b5 are excluded from the count because of the simultaneous timing although they exceed the wave height discrimination level indicated by the broken line. The external noises a6 and b6 and the internal noises a3 and b2 are excluded from the count because they are below the wave height discrimination level indicated by the broken line.
[0013]
The count value obtained by the non-simultaneous counting circuit 7 is input to the arithmetic unit 4, and the arithmetic unit 4 controls the non-simultaneous counting circuit 7, the memory 5, and the display 6, and calculates the count value of the non-simultaneous counting circuit 7 at a fixed period. The data is read and stored in the memory 5, the calculation such as the counting rate is executed by the calculation program and data stored in the memory 5, and the calculation result is stored in the memory 5 and displayed on the display 6.
[0014]
Therefore, according to the first embodiment, the non-simultaneous counting circuit 7 can selectively count analog signal pulses with non-simultaneous timing, thereby preventing external noise from being mixed in the counting.
[0015]
Embodiment 2. FIG.
A second embodiment of the present invention will be described with reference to the drawings.
FIG. 3 is a block diagram showing the configuration of the radiation monitor according to Embodiment 2 of the present invention. The same parts as those in the first embodiment shown in FIG. As a new code, reference numeral 8 denotes a coincidence counting circuit. The coincidence counting circuit 8 inputs analog signal pulses output from the first semiconductor detector 1 and the second semiconductor detector 2 and has a predetermined peak value. The number of pulses that are equal to or higher than the discrimination level and satisfy the simultaneous timing condition are counted. Each of the first semiconductor detector 1 and the second semiconductor detector 2 includes one or more semiconductor sensors. Needless to say, the condition for discriminating the wave height of the coincidence counting circuit 8 may be that the wave height value is not less than a predetermined lower limit level and not more than the upper limit level, or may be a wave height analysis condition obtained by multiplying the wave height values.
[0016]
FIG. 4 shows signal waveforms at A, B, E, and F shown in FIG. 3. In the coincidence counting circuit 8, the external noises a5 and b5 are counted because they satisfy the condition of simultaneous timing and higher than the wave height discrimination level. The External noises a6 and b6 are excluded from the count because they are below the wave height discrimination level.
[0017]
Thus, by counting the simultaneous timing pulses by the coincidence counting circuit 8, the degree of intrusion of external noise can be grasped.
[0018]
FIG. 5 shows a calculation processing flow of the calculator 4. In step f 1, the current asynchronous clock value output from the non-simultaneous counting circuit 7 is input and stored in the memory 5. In step f 2, the current clock value output from the coincidence counting circuit 8 is input and stored in the memory 5. In step f3, the current non-same clock value is compared with the previous non-same clock value. Instead of the previous non-clock value, an average non-clock value obtained by multiplying the previous measurement value by the integration time may be used as the reference value.
[0019]
As a result of the comparison, if the current non-same clock value ≧ K · previous non-same clock value, the process proceeds to step f4. If the current non-same clock value <K · previous non-same clock value, the process proceeds to step f6. In step f4, the current clock value is compared with the current non-clock value, and if the comparison result shows that the current clock value is greater than or equal to P. If it is a non-same clock value this time, the process proceeds to step f6. Note that K is a value related to the measurement time, and is a value that approaches 1 when the measurement time is long, and P is a noise mixture allowable rate.
[0020]
In step f5, the current non-clock value is discarded, and the latest value of the non-clock value remains the previous value. In step f6, the current measurement value is calculated. The current measurement value is obtained as a count rate by dividing the current count value by the accumulated time, for example. Moreover, it is calculated | required as an average value of the newest non-same clock numerical value. As a calculation method of the average value, a moving average may be performed so that the integration time becomes constant, or the integration time may be controlled so that the integration count value becomes constant. In step f7, the present measurement value of the calculation result of step f6 is displayed on the display 6.
[0021]
Therefore, according to the second embodiment, the degree of intrusion of external noise is grasped, and when the non-clockwise value increases rapidly and is synchronized with the rapid noise intrusion, the non-coincidence count is measured. By eliminating the calculation data, it is possible to prevent an increase in instruction for high-frequency noise that cannot be excluded even by selectively counting analog signal pulses at non-simultaneous timing.
[0022]
Embodiment 3 FIG.
Embodiment 3 of the present invention will be described with reference to the drawings.
In the third embodiment, the configuration shown in FIG. 3 similar to that of the second embodiment is provided, and the arithmetic unit 4 executes arithmetic processing according to the flow shown in FIG. 5 as in the second embodiment. The processing content of step f7 shown is different.
[0023]
FIG. 6 shows a calculation process flow of the calculator 4 of the radiation monitor according to the third embodiment of the present invention, which corresponds to step f7 shown in FIG. 5 and includes steps f71, f72, and f73. In step f71, the number of discards of the current non-clock value is compared with the reference value R. If the number of times of discard of the current clock value is greater than or equal to R, the process proceeds to step f72 to issue an alarm and If the number of times of disposal is less than R, the process proceeds to step f73, where the current count value is displayed, and when an alarm is issued, an alarm is displayed.
[0024]
Therefore, according to the third embodiment, it is possible to prevent trouble by notifying the existence of a continuous noise source.
[0025]
【The invention's effect】
As described above, according to the present invention, a plurality of semiconductor detectors that detect radiation and output analog signal pulses are divided into two groups, and the non-simultaneous output pulses are counted. Can be prevented.
[0026]
In addition, a plurality of semiconductor detectors that detect radiation and output analog signal pulses are divided into two groups, and the non-simultaneous output pulses and simultaneous output pulses are counted at regular intervals, respectively. When the same clock value or the average non-clock value obtained from the previous measurement value is compared as a reference value, and the ratio K is less than the predetermined value, the current non-clock value or the latest multiple times When the ratio K is equal to or greater than a predetermined value, the current clock value is compared with the current non-clock value, and when the ratio P is less than the predetermined value, the current clock value is calculated. Alternatively, the current measurement value is calculated and output from the latest multiple times of the same clock value including the current time, and when the ratio P is equal to or greater than a predetermined value, the current clock value is discarded and the previous clock value or the previous clock value is discarded. Previous multiple including Since so calculates and outputs a current measurement value from the non-coincidence count of an instruction rise against high-frequency noise that can not be eliminated by the non-coincidence can be prevented.
[0027]
In addition, since a failure alarm is issued when the number of discarded non-same clock values continues for a predetermined number of times this time, it is possible to prevent the trouble by notifying the existence of a continuing noise source. ]
FIG. 1 is a block diagram showing a configuration of a radiation monitor according to Embodiment 1 of the present invention.
FIG. 2 is a diagram showing signal waveforms of the radiation monitor according to the first embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of a radiation monitor according to Embodiment 2 of the present invention.
FIG. 4 is a diagram showing signal waveforms of the radiation monitor according to Embodiment 1 of the present invention.
FIG. 5 is a diagram showing a calculation processing flow of a radiation monitor according to Embodiment 3 of the present invention.
FIG. 6 is a diagram showing a calculation processing flow of the radiation monitor according to the third embodiment of the present invention.
FIG. 7 is a block diagram showing a configuration of a radiation monitor using a conventional semiconductor detector.
FIG. 8 is a diagram showing signal waveforms of a radiation monitor using a conventional semiconductor detector.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st semiconductor detector, 2nd 2nd semiconductor detector, 4 arithmetic unit, 5 memory, 6 indicator, 7 non coincidence counting circuit, 8 coincidence counting circuit.

Claims (2)

First and second semiconductor detectors each having one or a plurality of semiconductor sensors that detect radiation and output analog signal pulses and are provided in two groups;
A non-simultaneous counting circuit that receives analog signal pulses output from the first and second semiconductor detectors and counts pulses having a peak value equal to or higher than a predetermined discrimination level and satisfying a condition of non-simultaneous timing ;
A coincidence counting circuit for inputting analog signal pulses output from the first and second semiconductor detectors, counting pulses having a peak value equal to or higher than a predetermined discrimination level and satisfying a simultaneous timing condition;
The non-simultaneous counting circuit and the non-simultaneous output pulse and the simultaneous output pulse output from the coincidence counting circuit are respectively counted at a fixed period, and the average non-simultaneous value obtained from the current non-simultaneous clock value and the previous non-simultaneous clock value or the previous measured value are calculated. The same clock value is compared as a reference value, and when the ratio K is less than a predetermined value, the current measurement value is calculated and output from the current non-same clock value or the latest non-same clock value including the current time, When the ratio K is equal to or greater than a predetermined value, the current clock value is compared with the current non-clock value, and when the ratio P is less than the predetermined value, the current non-clock value or the latest plurality of non-clock clocks including the current time. The current measurement value is calculated and output from the numerical value, and when the ratio P is equal to or greater than the predetermined value, the current non-same clock value is discarded, and the previous non-same clock value or the latest multiple non-same times including the previous time. Calculate and output the current measurement value from the clock value Radiation monitor comprising a calculator that. The radiation monitor according to claim 1 .
The arithmetic unit issues a failure warning when the number of times the non-clockwise clock value is discarded continues for a predetermined number of times.

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