JP3659852B2 - Radiation measuring instrument - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radiation meter, and more particularly to a personal dosimeter that measures a 1 cm dose equivalent, a 3 mm dose equivalent, and a 70 μm dose equivalent.
[0002]
[Prior art]
In nuclear power plants, nuclear fuel facilities, radiation handling facilities, etc., each worker is required to carry a personal dosimeter. There are various types of personal dosimeters, and among them, there are those that measure a plurality of types of dose equivalents (1 cm dose equivalent, 3 mm dose equivalent, 70 μm dose equivalent). Such a conventional personal dosimeter is provided with two or three or more radiation detectors, and each dose equivalent is determined from the detected values.
[0003]
[Problems to be solved by the invention]
However, when a large number of radiation sensors are used, the circuit configuration becomes complicated in proportion thereto, causing problems such as an increase in power consumption (promotion of battery consumption) and an increase in the shape of the personal dosimeter. Further, when a different filter is provided for each radiation sensor, the amount of the detection unit increases.
[0004]
Japanese Patent Laid-Open No. 7-12939 discloses a related technique, but there is a problem in terms of downsizing the personal dosimeter. In Japanese Patent Laid-Open No. 62-2111578, a pulse from a single radiation sensor is input to a plurality of pulse height discriminators, the energy of the radiation is determined from the ratio of the outputs, and the energy of the sensor is determined according to the energy. It is disclosed to correct the response characteristic. However, since the response correction prior to the calculation of the output ratio is not considered, there is a problem that the energy estimation accuracy cannot be improved.
[0005]
The present invention has been made in view of the above conventional problems, and an object thereof is to measure a plurality of dose equivalents with a small number (preferably one) of radiation sensors.
[0006]
Another object of the present invention is to accurately estimate radiation energy in a personal dosimeter and use it for calculation.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is a detection method in which a single radiation sensor and a plurality of discrimination thresholds are set in a time-sharing manner in a stepwise manner, and detection pulses from the radiation sensor are input and each discrimination threshold is exceeded. A pulse height discriminating unit that outputs a pulse, and means for periodically switching each discrimination threshold in a time-sharing manner according to a predetermined switching pattern, and performing response correction for each discrimination threshold by adjusting a setting period of each discrimination threshold Based on the time-division control means to be performed , a counter for counting the detection pulses for each of the response-corrected discrimination thresholds to obtain a count value, and the count value for each of the response-corrected discrimination thresholds, the radiation energy is calculated. Based on the means for estimating and the response-corrected count value for each discrimination threshold, a procedure for calculating a dose corrected according to the energy of the radiation Characterized in that it comprises a and.
The present invention also provides a pulse height discrimination in which a single radiation sensor and a plurality of discrimination thresholds are set in a time division manner in a stepwise manner, a detection pulse from the radiation sensor is input, and a detection pulse exceeding each discrimination threshold is output. A time-division control means for periodically switching each discrimination threshold in a time-sharing manner according to a predetermined switching pattern, a counter for counting a detection pulse for each discrimination threshold, and obtaining a count value, and for each discrimination threshold Means for performing response correction by multiplying a count value by a response correction coefficient; means for estimating the energy of radiation based on the count value for each response-corrected discrimination threshold; and And a means for calculating a dose corrected according to the energy of the radiation based on a count value for each discrimination threshold.
[0008]
According to the above configuration, the discrimination threshold of the wave height discriminator is switched by time-sharing control. Therefore, the discrimination circuit can be shared by different wave height discrimination, and the circuit configuration can be simplified. In addition, weighting (response correction) can be performed on the number of detected pulses to improve the calculation accuracy of the dose.
[0009]
The above weighting can be realized by adjusting the setting time of each discrimination threshold or by multiplying a coefficient corresponding to each discrimination threshold. In the case of the former time weighting, for example, a single counter is connected to the subsequent stage of the wave height discriminating unit, and a count value is output from the counter for each discrimination threshold, and they are temporarily stored in the memory, and then, Various calculations (particularly energy estimation described later) may be performed on each count value in the memory. Alternatively, on the counter, when the integrated value of the count value that is time-weighted for each discrimination threshold is obtained, the integrated value is output from the counter, and various calculations are performed on the integrated value. The dose and dose equivalent may be calculated. On the other hand, in the case of the latter coefficient weighting, generally, a count value is transferred from the single counter to each memory for each wave height discrimination value, and coefficient multiplication is performed on each count value on the memory. Even in this case, since each count value is independently stored in the memory, the radiation energy can be estimated by them.
[0010]
Here, preferably, since a single radiation sensor, a single pulse height discriminator, and a single counter are used, the circuit configuration can be extremely simplified.
[0011]
Nozomu Mashiku, the means for calculating the dose calculates 1cm dose equivalent, 3 mm dose equivalent, a 70μm dose equivalent. Preferably, the plurality of discrimination thresholds are three discrimination thresholds, and the energy of the radiation is estimated and the dose is calculated based on the three response-corrected count values.
[0012]
In order to achieve the above object, the present invention has a single radiation sensor and n (but two or more) discrimination thresholds are set stepwise, and a detection pulse from the radiation sensor is input. Multi-wave height discriminating section for outputting detection pulses exceeding each discrimination threshold, n counters for counting detection pulses for each discrimination threshold, and correction means for performing response correction on the count values of the n counters If, based on the count value of the n counter after said response correction, means for estimating the energy of the radiation, on the basis of the response corrected n-number of the counter count value, depending on the estimated energy And a dose calculation unit that calculates the corrected dose.
[0013]
According to the above configuration, the radiation energy is estimated after the response correction is performed on the count values of the n counters. Therefore, the estimation accuracy can be increased, and the dose calculation accuracy can be improved.
Desirably, the dose calculation unit calculates a 1 cm dose equivalent, a 3 mm dose equivalent, and a 70 μm dose equivalent. Preferably, the n is 3, and the radiation energy is estimated and the dose is calculated based on the three response-corrected count values.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.
[0015]
FIG. 1 shows a preferred embodiment of a radiation measuring instrument according to the present invention, and FIG. 1 is a block diagram showing the overall configuration thereof. The radiation measuring instrument according to this embodiment is, for example, a personal dosimeter. Of course, the present invention can be applied to other radiation measuring devices.
[0016]
In FIG. 1, the radiation sensor 10 is comprised with the semiconductor detector in this embodiment. The radiation sensor outputs a detection pulse having a pulse peak value corresponding to the energy of radiation (for example, X-ray or γ-ray). The preamplifier 12 amplifies the detection pulse, and the detection pulse that passes through the preamplifier 12 is amplified by the linear amplifier 14. The detection pulse output from the linear amplifier 14 is input to a discrete (wave height discriminator) 16. On the other hand, a reference voltage from the calculation control unit 18 is supplied to the discreet 16.
[0017]
In the disc 16, only the detection pulse having a peak value exceeding the reference voltage passes. Here, in the present embodiment, a reference voltage output unit 22 is provided in the arithmetic control unit 18, and the reference voltage output unit 22 periodically switches and sets three levels of reference voltage levels in a time division manner. In the switching pattern, the setting periods of the respective reference voltage levels may coincide with each other, but in that case, weighting by coefficient multiplication is required as will be described later. On the other hand, in this embodiment, the reference voltage output unit 22 has a time weighting function. Specifically, the setting period of each reference voltage level is adjusted according to the weighting coefficient corresponding to each discrimination level. Yes.
[0018]
The counter 20 receives a pulse output from the disc 16. In the example of FIG. 1, the counter 20 counts a pulse for each discrimination level. As described above, the coefficient value of the number of pulses corresponding to each discrimination level is sequentially stored in the counter 20 by the time division control of the reference voltage output unit 22, and each value is read at a predetermined timing, and the memory 50 described later. Temporarily stored.
[0019]
In FIG. 1, the count values corresponding to each discrimination level are indicated by A, B, and C, and these are sequentially input to the CPU 24. The CPU 24 manages the count of each count value by executing the steps shown in FIG. 7 and FIG. 2 to be described later, and finally estimates three dose equivalents, that is, while estimating the radiation energy E. 1 cm dose equivalent, 3 mm dose equivalent, and 70 μm dose equivalent are calculated. Those three dose equivalents are displayed on the display unit 26. Electric power is supplied from the battery 28 to each circuit.
[0020]
Here, the CPU 24 controls the operations of the counter 20 and the reference voltage output unit 22. A memory 50 is connected to the CPU 24. The counting control of the CPU 24 will be described with reference to FIG. First, in S <b> 201, the reference voltage for the count value A is set in the reference voltage output unit 22. In S202, counting by the counter 20 is started, and counting by the counter 20 is continued until the set time for A has elapsed in S203. If it is determined in S203 that the set time for the count value A has elapsed, the count value in the counter 20 is transferred to the memory 50 in S204, and then the counter 20 is reset in S205. Then, steps similar to the above-described series of steps are executed for the count value B in S206 to S210, and for the count value C, are executed in S211 to S215. Finally, when it is determined in S216 that measurement is to be continued, each process from S201 is repeatedly executed. Through the above steps, the count values A, B, and C are stored in the memory 50, so the CPU 24 executes the following calculation step of FIG. Although the case of the time weighting method has been described above, when the coefficient weighting method is applied, for example, the setting time of the discrimination level of each count value is the same, and each count value before weighting is stored in the memory 50. Will be.
[0021]
FIG. 2 shows a calculation content in the CPU 24 as a flowchart.
[0022]
First, in S101, radiation is measured according to the time division method as described above. In S102, when the coefficient weighting method is applied, the respective count values A, B, and C are multiplied by the response correction coefficients a1, b1, and c1, respectively, and the addition result is multiplied by a constant constant K. Thus, a 1 cm dose equivalent D (10) is obtained. However, the energy sensitivity of the 1 cm dose equivalent D (10) is corrected in later S104. Incidentally, the calculation formula is represented by the formula (1) in FIG.
[0023]
On the other hand, in S102, when the time weighting method (response correction by time weighting) as shown in FIG. 7 is applied, the addition value of the count values A, B, and C is multiplied by a constant K, thereby A 1 cm dose equivalent D (10) is calculated. However, as described above, the 1 cm dose equivalent D (10) is corrected for energy sensitivity in later S104. This is shown as the calculation formula (2) in FIG.
[0024]
In the case of the coefficient weighting method, the switching of the reference voltage output unit 22 is simplified, but on the other hand, the burden of coefficient multiplication increases. On the other hand, the time weighting method has an advantage that the amount of calculation can be reduced.
[0025]
Incidentally, the above-mentioned coefficients a1, b1, c1 or time weighting periods corresponding to them correspond to response correction coefficients for the respective discrimination levels.
[0026]
In S103, the radiation energy E is estimated. In the case of the coefficient weighting method, the energy E is estimated based on A ′ (= A × a1), B ′ (= B × b1), and C ′ (= C × c1). The energy E is estimated based on the count values A, B, and C that have already been weighted.
[0027]
In estimating the energy E, a distribution table as shown in FIG. 6 is referred to. Referring to FIG. 6, the horizontal axis of the table shown in FIG. 6 is the effective energy of the incident radiation, and the vertical axis is the count value 104 after response correction corresponding to the first discrimination level, the second It shows the mutual ratio between the count value 102 after response correction corresponding to the discrimination level and the count value 100 after response correction corresponding to the third discrimination level. Incidentally, for example, the first discrimination level is set to 20 keV, the second discrimination level is set to 30 keV, and the third discrimination level is set to 90 keV.
[0028]
As described above, the effective energy of the incident radiation can be estimated based on the mutual ratio as shown in FIG. In the present embodiment, since the mutual ratio of the three count values is used, there is an advantage that the energy estimation accuracy can be improved while keeping the amount of calculation constant. In particular, in this embodiment, since energy estimation is performed based on each count value after response correction, more accurate estimation is possible.
[0029]
Returning to FIG. 2, in S104, the 1 cm dose equivalent D (10) calculated in S102 is corrected based on the estimated energy E. In this case, it is conceivable to multiply the coefficient values corresponding to the table shown in FIG. By this S104, the corrected 1 cm dose equivalent D (10) is obtained.
[0030]
In S105, for example, 3 mm dose equivalent D (3) and 70 μm dose equivalent D (0.07) are obtained by multiplying predetermined coefficients based on the corrected 1 cm dose equivalent D (10) obtained in S104. Calculated. For these calculations, various parameters obtained in S102 or S103 can be used as appropriate.
[0031]
In any case, since each dose equivalent is corrected and calculated under the energy estimation, there is an advantage that three types of dose equivalent can be calculated even when the single radiation sensor 10 is used as shown in FIG. is there. In S106, the three dose equivalents calculated as described above are displayed on the display unit 26.
[0032]
In the above configuration, the counter 20 transfers the count values to the memory 50 at the timing when the count values A, B, and C for each discrimination threshold are obtained, and the counter 20 is reset at the same time. 20, the integrated value is output from the counter at the timing when the integrated value (A + B + C) is obtained (at the same time, the counter 20 is reset), and a predetermined calculation such as multiplication of a coefficient value is performed on the integrated value. The dose and dose equivalent may be obtained by In this case, however, energy estimation becomes difficult, but the configuration can be simplified.
[0033]
3 and 4 show another embodiment. FIG. 3A shows the weighting coefficients a1, b1, and c1 for each estimated energy category. By using each coefficient for each energy category and performing an operation as shown in FIG. 3B, for example, energy correction can be performed simultaneously with response weighting.
[0034]
FIG. 4A shows a1 to c1, a2 to c2, and a3 to c3 for each energy section. By executing the arithmetic expression as shown in FIG. It is also possible to calculate equivalents simultaneously. Even in this case, response correction and energy sensitivity correction are achieved at the same time.
[0035]
Incidentally, the calculation example described above is only an example, and various methods other than this can be applied.
[0036]
FIG. 5 shows another embodiment. In addition, the same code | symbol is attached | subjected to the structure similar to the structure shown in FIG. 1, and the description is abbreviate | omitted. In this embodiment, three discs are provided in parallel. That is, the discs 16A, 16B, and 16C are provided. Different discrimination levels are set for each, and the respective outputs are input to the counts 32, 34, and 36 in the arithmetic processing unit 30 and counted independently. The counted values are represented by A, B, and C, and the calculation unit 38 calculates the above three dose equivalents by executing the various calculation formulas described above. The calculation result is displayed on the display unit 40. The battery 42 is a circuit that supplies power to each circuit.
[0037]
Also in such an embodiment, as shown in FIG. 6, the effective energy is estimated after performing the response correction for the count values A, B, and C, and is estimated with such high accuracy. Energy sensitivity correction is performed by effective energy. Therefore, there is an advantage that the dose equivalent can be obtained with higher accuracy than the conventional example.
[0038]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the size of the radiation measuring instrument. In addition, according to the present embodiment, high-precision measurement can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration example of a radiation measuring apparatus according to the present invention.
FIG. 2 is a flowchart showing processing contents in a calculation unit.
FIG. 3 is a diagram showing another example of a method for calculating a dose equivalent.
FIG. 4 is a diagram illustrating another example of a dose equivalent calculation method.
FIG. 5 is a block diagram showing a configuration of a radiation measuring instrument according to another embodiment.
FIG. 6 is an explanatory diagram showing the principle of energy estimation.
FIG. 7 is an explanatory diagram for explaining a time weighting method;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Radiation sensor, 12 Preamplifier, 14 Linear amplifier, 16 Discrete, 18 Arithmetic processing part, 20 Counter, 22 Reference voltage output part, 24 CPU, 26 Display part.

Claims (7)

A single radiation sensor;
A plurality of discrimination thresholds are set in a time-sharing manner in stages, a detection pulse from the radiation sensor is input, and a pulse height discrimination unit that outputs detection pulses exceeding each discrimination threshold;
Means for periodically switching each discrimination threshold in a time-sharing manner according to a predetermined switching pattern, and time-division control means for performing response correction for each discrimination threshold by adjusting a setting period of each discrimination threshold ;
A counter that counts the detection pulse for each discrimination threshold that is response-corrected to obtain a count value;
Means for estimating the energy of the radiation based on the count value for each discrimination threshold that has been response-corrected;
Means for calculating a dose corrected in accordance with the energy of the radiation, based on the count value for each of the discrimination threshold values corrected for the response;
A radiation measuring instrument comprising: A single radiation sensor;
A plurality of discrimination thresholds are set in a time-sharing manner in stages, a detection pulse from the radiation sensor is input, and a pulse height discrimination unit that outputs detection pulses exceeding each discrimination threshold;
Time-division control means for periodically switching each discrimination threshold in a time-sharing manner according to a predetermined switching pattern;
A counter for counting a detection pulse for each discrimination threshold to obtain a count value;
Means for performing response correction by multiplying the count value for each discrimination threshold by a response correction coefficient;
Means for estimating the energy of the radiation based on the count value for each discrimination threshold that has been response-corrected;
Means for calculating a dose corrected according to the energy of the radiation based on a count value for each of the response-corrected discrimination thresholds;
A radiation measuring instrument comprising: The radiation measuring instrument according to claim 1 or 2 ,
The means for calculating a dose calculates a 1 cm dose equivalent, a 3 mm dose equivalent, and a 70 μm dose equivalent. The radiation measuring instrument according to claim 1 or 2,
The plurality of discrimination thresholds are three discrimination thresholds;
A radiation measuring apparatus characterized in that radiation energy is estimated and a dose is calculated based on three response-corrected count values. A single radiation sensor;
A multi-wave height discriminating unit which sets n (but two or more) discrimination thresholds in stages, inputs detection pulses from the radiation sensor, and outputs detection pulses exceeding the discrimination thresholds;
N counters for counting detection pulses for each discrimination threshold;
Correction means for performing response correction on the count values of the n counters;
Means for estimating the energy of radiation based on the count values of the n counters after the response correction;
A dose calculation unit for calculating a dose corrected according to the estimated energy based on the response-corrected n counter values;
A radiation measuring instrument comprising: The radiation measuring instrument according to claim 5, wherein
The dose calculator is configured to calculate a 1 cm dose equivalent, a 3 mm dose equivalent, and a 70 μm dose equivalent. The radiation measuring instrument according to claim 5, wherein
N is 3;
Based on the three response-corrected values, the radiation energy is estimated and the dose Is a radiation measuring instrument characterized in that

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