JP2001215277A - Radiation meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize miniaturization and heighten energy estimation accuracy in a radiation meter. SOLUTION: A reference voltage output part 22 switches three discrimination levels following a prescribed pattern. In this case, weighting is executed by adjustment of setting periods of each discrimination level. A CPU 24 executes energy estimation based on discrete count values A, B, C of each discrimination level, and operates a dose equivalent by using the estimated energy. Plural discriminators can be installed in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation measuring instrument, and more particularly, to a 1 cm dose equivalent, a 3 mm dose equivalent, and 70 μm.
The present invention relates to a personal dosimeter for measuring dose equivalent.

[0002]

2. Description of the Related Art In a nuclear power plant, a nuclear fuel facility, a radiation handling facility, etc., each worker is required to carry a personal dosimeter. There are various types of personal dosimeters, among which multiple types of dose equivalents (1 cm dose equivalent, 3
(mm dose equivalent, 70 μm dose equivalent). In such a conventional personal dosimeter, two or three or more radiation detectors are provided, and each dose equivalent is determined from the detected values.

[0003]

However, if a large number of radiation sensors are used, the circuit configuration becomes proportionately complicated, and the power consumption increases (promoting battery consumption).
A problem arises in that the shape of the personal dosimeter becomes large. Also,
When a different filter is provided for each radiation sensor, the physical quantity of the detection unit increases.

Japanese Patent Application Laid-Open No. 7-12939 discloses a related technique, but has a problem in miniaturization of a personal dosimeter. Japanese Unexamined Patent Publication (Kokai) No. 62-21578 discloses that 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 that the response characteristic is corrected. 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.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to reduce the number (preferably 1).
) To measure a plurality of dose equivalents.

Another object of the present invention is to accurately estimate radiation energy in a personal dosimeter and use it for calculation.

[0007]

In order to achieve the above object, according to the present invention, a radiation sensor and a plurality of discrimination thresholds are set stepwise in a time-division manner, and a detection pulse from the radiation sensor is inputted. A pulse height discriminator for outputting a detection pulse exceeding each discrimination threshold, and time division control means for periodically switching each discrimination threshold in a time division manner according to a predetermined switching pattern, and weighting the number of detection pulses for each discrimination threshold And a calculation processing unit that calculates the dose based on the number of detected pulses after the weighting.

According to the above configuration, the discrimination threshold of the pulse height discriminator is switched by time division control, so that a discrimination circuit can be shared for a plurality of pulse height discriminations, and the circuit configuration can be simplified. Moreover, weighting is performed on the number of each detected pulse, so that the calculation accuracy of the dose can be improved.

The above weighting can be realized by adjusting the set time of each discrimination threshold or by multiplying by 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 discrimination unit, and the count value is output from the counter for each discrimination threshold, and they are temporarily stored in a memory.
Various calculations (particularly, energy estimation described later) may be performed on each count value in the memory. Alternatively, when the integrated value of the count value weighted for each discrimination threshold is obtained on the counter, the integrated value is output from the counter, and various operations are performed on the integrated value. The calculation of the dose and the dose equivalent may be performed. On the other hand, in the case of the latter coefficient weighting, generally, the count value is transferred from the single counter to the memory for each peak value discrimination value, and the count value on the memory is multiplied by a coefficient. Also in this case, since the respective count values are independently stored in the memory, the energy of the radiation can be estimated based on the count values.

Here, since a single radiation sensor, a single wave height discriminator, and a single counter are preferably used, the circuit configuration can be extremely simplified.

Preferably, the arithmetic processing unit weights each of the discrimination thresholds by adjusting a setting period of each discrimination threshold. According to the above configuration, it is possible to reduce the amount of calculation by performing weighting by time adjustment of the discrimination threshold. Preferably, the dose calculation unit includes a 1 cm dose equivalent,
A 3 mm dose equivalent and a 70 μm dose equivalent are calculated. Preferably, the arithmetic processing unit performs weighting for each of the discrimination thresholds by multiplying the number of detection pulses by a coefficient for each of the discrimination thresholds. According to this configuration, weighting can be performed by a mathematical operation of multiplication of coefficients.

In order to achieve the above object, the present invention provides a single radiation sensor and n (but two or more) discrimination thresholds are set in stages, and detection pulses from the radiation sensor are used. A multi-wave height discriminator that inputs and outputs a detection pulse exceeding each discrimination threshold, n counters that count detection pulses for each discrimination threshold, and response correction for the count value of the n counters. Correction means to perform;
Means for estimating the energy of the radiation based on the count value of the n counters after the response correction, and a dose for calculating the dose in accordance with the estimated energy based on the count value of the n counters And an operation unit.

According to the above configuration, the radiation energy is estimated after performing the response correction on the count values of the n counters, so that the accuracy of the estimation can be improved, and the accuracy of the dose calculation can be improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

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 entire configuration. The radiation measuring instrument according to the present embodiment is, for example, a personal dosimeter. Of course, the present invention is applicable to other radiation measuring instruments.

In FIG. 1, the radiation sensor 10 is constituted by a 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 passing therethrough is amplified by the linear amplifier 14. The detection pulse output from the linear amplifier 14 is input to a discrimination (wave height discriminator) 16. On the other hand, the reference voltage from the arithmetic control unit 18 is supplied to the discrimination 16.

In the discrimination 16, only a 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 reference voltage levels in a time division manner. In the switching pattern, the setting periods of the respective reference voltage levels may be the same, but in that case, weighting by coefficient multiplication is necessary as described later. On the other hand, in the present embodiment, the reference voltage output unit 22 has a time weighting function, and specifically,
The setting period of each reference voltage level is adjusted according to the weighting coefficient corresponding to each discrimination level.

The counter 20 receives pulses output from the discrimination 16, and in the example of FIG. 1, the counter 20 counts pulses 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 is read out at a predetermined timing. Is temporarily stored in

In FIG. 1, the count values corresponding to the respective discrimination levels are indicated by A, B, and C.
Are sequentially input. The CPU 24 manages the count of each count value by executing the steps shown in FIGS. 7 and 2 described below, and finally estimates the radiation energy E, and finally obtains three dose equivalents, that is, three dose equivalents. 1c
The m dose equivalent, 3 mm dose equivalent, and 70 μm dose equivalent are calculated. The three dose equivalents are displayed on the display unit 26. Note that power is supplied from the battery 28 to each circuit.

Here, the CPU 24 controls the operations of the counter 20 and the reference voltage output unit 22. Also, CP
A memory 50 is connected to U24. This CPU2
The counting control of No. 4 will be described with reference to FIG. First, S
In 201, a 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 elapses in S203. S20
If it is determined in step 3 that the set time for the count value A has elapsed,
After the count value in the counter 20 is transferred to the memory 50 in 204, 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
The processing is performed in 211 to S215. Finally, when it is determined in S216 that the measurement is to be continued, the steps from S201 are repeatedly executed. Through the above steps, the memory 50 has
Since the count values A, B, and C are stored, the CPU
24 executes the following calculation process of FIG. Although the case of the time weighting method has been described above,
When the coefficient weighting method is applied, for example, the set time of the discrimination level of each count value is set to be the same, and each count value before weighting is stored in the memory 50.

FIG. 2 is a flowchart showing the contents of the calculation in the CPU 24.

First, in step S101, radiation is measured according to the time division method as described above. In S102, when the coefficient weighting method is applied, each of the count values A, B, C
Are multiplied by coefficients a1, b1, and c1, respectively, and the result of addition is multiplied by a constant K to thereby obtain a 1 cm dose equivalent D (10). Incidentally, the arithmetic expression is represented by Expression (1) in FIG.

On the other hand, in this S102, when the time weighting method as shown in FIG. 7 is applied, the added value of the count values A, B, and C is multiplied by a constant K, whereby the 1 cm dose equivalent D (10) is calculated. This is shown in FIG. 2 as the calculation formula (2).

In the case of the coefficient weighting method, switching of the reference voltage output section 22 is simplified, but the load of coefficient multiplication increases. On the other hand, in the case of the time weighting method, there is an advantage that the amount of calculation can be reduced.

Incidentally, the above-mentioned coefficients a1, b1, c1 or the time weighting periods corresponding thereto correspond to the response correction coefficients for the respective discrimination levels.

In S103, the energy E of the radiation is estimated. In the case of the coefficient weighting method, A ′ (= A × a
1), the energy E is estimated based on B ′ (= B × b1) and C ′ (= C × c1), while in the case of the time weighting method, the already weighted count values A, B,
The energy E is estimated based on C.

In estimating the energy E, a distribution table as shown in FIG. 6 is referred to. Referring now 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 response-corrected count value 10 corresponding to the first discrimination level.
4, the respective reciprocal ratios of the response-corrected count value 102 corresponding to the second discrimination level and the response-corrected count value 100 corresponding to the third discrimination level. Incidentally, for example, the first discrimination level is 20
keV, the second discrimination level is set to 30 keV, and the third discrimination level is set to 90 keV.

As described above, the effective energy of the incident radiation can be estimated from 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 accuracy of energy estimation can be improved while the amount of calculation is kept constant. In particular, in the present embodiment, energy estimation is performed based on each count value after response correction, so that more accurate estimation is possible.

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, multiplication by a coefficient value corresponding to the table shown in FIG. 6 can be considered. By this S104, the corrected 1 cm dose equivalent D (10) is obtained.

In S105, for example, the 3 mm dose equivalent D (3) and the 70 μm dose equivalent D (0 .0) are multiplied by predetermined coefficients based on the corrected 1 cm dose equivalent D (10) obtained in S104, for example. 07) is calculated. In calculating them, S102 or S
Various parameters obtained in step 103 and the like can be used as appropriate.

In each case, under energy estimation,
Since each dose equivalent is corrected and calculated, there is an advantage that three types of dose equivalents can be calculated even if a single radiation sensor 10 is used as shown in FIG. In S106,
The display unit 26 displays the three dose equivalents calculated as described above.

In the above configuration, the counter 20 transfers the respective count values to the memory 50 at the timing when the count values A, B, and C for each discrimination threshold are obtained.
At the same time, the counter 20 is reset. At the timing when the integrated value (A + B + C) is obtained, the counter 20 outputs the integrated value (simultaneously resets the counter 20). By performing a predetermined operation such as multiplication of coefficient values,
The dose and the dose equivalent may be obtained. However, in this case, the energy estimation becomes difficult, but the configuration can be simplified.

FIGS. 3 and 4 show another embodiment. FIG. 3A shows the estimated weighting coefficients a1, b1, and c1 for each energy section. By using such coefficients for each energy section to perform an operation as shown in FIG. 3B, for example, it is possible to perform energy correction simultaneously with response weighting.

FIG. 4A shows a1 to c1, a2 to c2, and a3 to c3 for each energy division. By executing an arithmetic expression as shown in FIG. It is also possible to calculate three dose equivalents simultaneously. Also in this case, the response correction and the energy sensitivity correction are simultaneously achieved.

Incidentally, the above calculation example is one example, and
Various other methods can be applied.

FIG. 5 shows another embodiment.
The same components as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, three discries are provided in parallel. That is, the discriminations 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 are counted independently. The count value is A, B, C
The calculation unit 38 calculates the above three dose equivalents by executing the above-described various calculation expressions. The calculation result is displayed on the display unit 40. The battery 42 is a circuit that supplies power to each circuit.

Also in this embodiment, as shown in FIG. 6, the effective energy is estimated after the response correction for the count values A, B, and C, and thus the accuracy is high. Energy sensitivity correction is performed by the estimated effective energy. Therefore, there is an advantage that the dose equivalent can be obtained with higher accuracy than the conventional example.

[0038]

As described above, according to the present invention,
The radiation measuring instrument can be reduced in size. Also,
According to this embodiment, highly accurate measurement can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of a radiation measuring instrument 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 of calculating a dose equivalent.

FIG. 4 is a diagram showing another example of a method of calculating a dose equivalent.

FIG. 5 is a block diagram showing a configuration of a radiation measuring device according to another embodiment.

FIG. 6 is an explanatory diagram showing an energy estimation principle.

FIG. 7 is an explanatory diagram for explaining a time weighting method.

[Explanation of symbols]

10 radiation sensor, 12 preamplifier, 14 linear amplifier, 16 discriminator, 18 arithmetic processing unit, 20
Counter, 22 reference voltage output unit, 24 CPU, 26
Display section.

Claims (6)

[Claims] A radiation sensor; a plurality of discrimination thresholds set in a time-division manner in a time-division manner; a pulse height discrimination unit for receiving a detection pulse from the radiation sensor and outputting a detection pulse exceeding each discrimination threshold; A time-division control means for periodically switching each discrimination threshold in a time-sharing manner according to the switching pattern, weighting the number of detected pulses for each of the discrimination thresholds, and setting the dose based on the number of detected pulses after the weighting. A radiation measurement device comprising: an arithmetic processing unit that performs an operation. 2. The radiation measuring instrument according to claim 1, wherein the arithmetic processing unit performs weighting for each of the discrimination thresholds by adjusting a setting period of each discrimination threshold. 3. The radiation measurement device according to claim 1, wherein the arithmetic processing unit performs weighting for each of the discrimination thresholds by multiplying a coefficient to the number of detection pulses for each of the discrimination thresholds. Radiation measuring instrument. 4. The radiation measuring apparatus according to claim 1, wherein the dose calculation unit is configured to perform a 1 cm dose equivalent, a 3 mm dose equivalent,
A radiation measuring device for calculating a 70 μm dose equivalent. 5. A single radiation sensor and n (but two or more) discrimination thresholds are set in stages,
A multi-pulse height discrimination unit that receives a detection pulse from the radiation sensor and outputs a detection pulse exceeding each discrimination threshold, n counters that count detection pulses for each discrimination threshold, and n counters. Correction means for performing response correction on the count value, based on the count value of the n counters after the response correction, means for estimating the energy of radiation, based on the count value of the n counters, A radiation calculator for calculating a radiation dose according to the estimated energy. 6. The radiation measuring device according to claim 5, wherein the dose calculation unit is configured to: 1 cm dose equivalent, 3 mm dose equivalent,
A radiation measuring device for calculating a 70 μm dose equivalent.