JP4731330B2 - Radiation monitor - Google Patents

Description

  The present invention relates to a radiation monitor, and more particularly to a radiation monitor that converts a minute current signal from a radiation detector into a frequency signal and measures a radiation dose or a radioactivity amount by the frequency, and measures a wide range of radiation levels with high accuracy. The present invention relates to a radiation monitor.

  At nuclear power plants, nuclear fuel reprocessing facilities, particle beam utilization facilities, etc., ionization chambers, scintillation detectors, semiconductor detectors, etc. are used as radiation detectors to measure radiation dose or radioactivity, and normal radiation levels In order to cover a wide measurement range from the radiation level to the radiation level assuming an accident, a radiation monitor is installed to measure the current generated by the radiation acting on the radiation detector by converting it into a frequency.

  A conventional radiation monitor of this type includes an electrometer composed of an integrator and a reset circuit. The integrator is composed of an operational amplifier and a charge integrating capacitor, and the charge integrating capacitor is connected to the operational amplifier as a negative feedback circuit. Therefore, the output current of the radiation detector is accumulated in the form of charge by the charge integration capacitor, the operational amplifier outputs a voltage that rises with time as a result of the accumulation of the charge, and the reset circuit has a predetermined output voltage of the operational amplifier. When this level is reached, the charge integration capacitor is discharged and reset, and a one-shot pulse is output. If current is input to the electrometer in this way, pulses are repeatedly output from the electrometer, and the radiation dose is measured by counting the pulses.

The current output from the radiation detector can measure a minute current at the lower limit of measurement, from the order of 1 × 10 ⁻¹⁴ A to 1 × 10 ⁻⁷ A depending on the radiation level, and covers a wide range up to the upper limit of measurement. It must be measurable.
In order to measure the radiation level with high accuracy over a wide range, in the minute current region, a highly insulated relay contact is used for the switch that discharges the charge integrating capacitor in consideration of current leakage during charging, which is the main cause of measurement error. However, in the high current region, a semiconductor switch that operates at high speed is used in consideration of the missing measurement time caused by the switch operating time, which is the main cause of measurement errors, and the relay contact and the semiconductor switch are connected in parallel or in series. A technique for switching a switch according to a frequency has been proposed (see, for example, Patent Document 1).

JP 2002-365317 A

Since the conventional electrometer is configured as described above, since the terminal of the semiconductor switch is connected to the operational amplifier, a minute current leak peculiar to the semiconductor occurs even when the switch function is off, There is a problem that the measurement accuracy is greatly affected in a minute current region.
If the above-described measurement error can be eliminated without using such a semiconductor switch, it is possible to solve both the measurement error problem in the high current region and the measurement error problem in the minute current region.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a radiation monitor capable of measuring radiation levels over a wide range with high accuracy.

The radiation monitor according to the present invention includes a radiation detection unit that detects radiation and outputs an ionization current, and inputs the ionization current and accumulates it as a charge, and a voltage value corresponding to the integral value of the charge has a charge storage start The coefficient signal is output each time a plurality of discrimination levels sequentially provided at equal intervals from the current voltage level are sequentially reached, and when the last discrimination level is reached, the accumulated charge is discharged and the charge is accumulated again. And a radiation dose output means for calculating and outputting the radiation dose based on the count value obtained by counting the count signal .

  According to the present invention, it is possible to provide a radiation monitor capable of measuring radiation levels over a wide range with high accuracy.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the configuration of the radiation monitor according to the first embodiment. FIG. 2 is a diagram for explaining the operation of the electrometer in the first embodiment. FIG. 3 is a flowchart showing the calculation procedure of the measurement unit in the first embodiment.

In FIG. 1 showing the configuration of the radiation monitor according to the first embodiment of the present invention, the radiation detector 1 detects radiation and outputs an ionization current, and the electrometer 2 converts the ionization current into a pulse train and outputs it. The measurement unit 3 counts the pulses at a constant cycle, calculates the count rate based on the count value, converts the count rate into engineering values such as radioactivity concentration and dose rate, and outputs it. The display unit 4 outputs the output Is displayed. Note that the output of the measurement unit 3 may be a count rate.
The electrometer 2 includes an integrator 21, a comparator 22, and an electromagnetic relay 23. The integrator 21 includes an operational amplifier 211 and a charge integration capacitor 212. The electromagnetic relay 23 includes an electromagnetic coil 231 and a contact 232.

In FIG. 2 for explaining the operation of the electrometer 2 according to the first embodiment of the present invention, when an ionization current is input to the integrator 21, the operational amplifier 211 charges the charge obtained as a result of temporally integrating the ionization current. An output voltage V (a in FIG. 2) that is stored in the integrating capacitor 212 and is proportional to the charge amount Q is output. The output voltage V is equal to a value obtained by dividing the charge amount Q accumulated in the charge integration capacitor 212 by the capacitance C of the charge integration capacitor 212.
When the output voltage V of the operational amplifier 211 reaches the operating voltage V _s , the comparator 22 is inverted for a short time and outputs a one-shot pulse P _s (b in FIG. 2). The one-shot pulse electromagnetic coil 231 of the electromagnetic relay 23 operates in P _s, the contact 232 is reversed from the open only closing time t ₁ in the closed (c in FIG. 2), discharging the charges accumulated in the charge integration capacitor 212 And charge again. Therefore, the frequency of the one-shot pulse P _s output from the comparator 22 is proportional to the ionization current is input to the integrator 21.
Since the charge integrating capacitor 212 repeats charging and discharging, the output voltage V of the operational amplifier 211 repeatedly has a sawtooth waveform. If the charge integration capacitor 212 is excessively charged, the output voltage of the operational amplifier 211 is saturated and the linearity between the ionization current input and the output voltage is lost. Therefore, the charge integration capacitor 212 is discharged within the range in which the linearity is maintained. as performed, the operating voltage V _s of the comparator 22 is set.
The contact 232 has the advantages of high insulation and low leakage current, but has the disadvantage of relatively long operation time. The closing time t ₁ is longer than the discharging time t ₂ , and missing measurement occurs only during the closing time t ₁ .

In FIG. 3 showing the calculation procedure of the measurement unit according to the first embodiment of the present invention, it is determined whether or not the elapsed time from the start of measurement has reached the measurement time T set as a fixed period in step S1. If the measurement time T has been reached, the count value N is read in step S2. In step S3, a missing time N × t ₁ is obtained from the count value N and the contact closing time t ₁ . From the measurement time in step S4 T and missing time N × _{t 1} determining an actual measurement time _{Tr = T-N × t 1} . In step S5, the count rate n = N ÷ Tr is obtained from the count value N of the measurement unit 3 and the actual measurement time Tr. Step S6 in obtaining the net counting rate _n N = _{n-n b} from the background count rate _{n b} obtained in advance and counting rate n. In step S7, the radioactivity concentration or dose rate R = k × n _N is obtained from the converted count k and the net count rate nN. In step S8, the radioactivity concentration or dose rate R is output.

As described above, in the first embodiment, the measuring unit 3 calculates the missing measurement time N × t ₁ of the electrometer 2 from the count value N and the closing time of the contact 232, and calculates the counting rate n with the actual measurement time Tr. As a result, it is possible to compensate for an increase in error due to missing measurement in the high count rate region, which was a weak point of a highly insulated mechanical switch, and a highly accurate and wide-range inexpensive radiation monitor can be obtained.

According to the first embodiment of the present invention, radiation detection means comprising a radiation detector 1 that detects radiation and outputs an ionization current, inputs the ionization current, accumulates it in the charge integration capacitor 212, and stores it as a charge. When the voltage V corresponding to the integrated value of the electric charge corresponding to the operating voltage V _s reaches a predetermined value, a counting signal composed of a one-shot pulse P _s is output and the accumulated electric charge is discharged by the electromagnetic relay 23. and comprising a signal generating means comprising electrometer 2 as a current / frequency converter means for repeating the operation of storing charges again, a count made of the one-shot pulse P _s generated by the signal generating means comprising the electrometer 2 Found determined signal from the counted count value N and the measurement time T except missing time N × t ₁ by the discharge operation Is provided with the radiation amount output means comprising measuring unit 3 to be displayed on the display unit 4 the radiation dose as a result time Tr = T-N × calculates the radiation dose based on t ₁ and outputs the measurement, the main measurement error The radiation dose can be calculated by compensating for the missing measurement time caused by the switch operating time, and the entire measurement range can be covered with highly insulated relay contacts. It is possible to provide a radiation monitor capable of measuring a wide range of radiation levels with high accuracy by eliminating the influence of missing time due to the discharge operation with a simple configuration.

Embodiment 2. FIG.
A second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a block diagram showing the configuration of the radiation monitor according to the second embodiment. FIG. 5 is a diagram for explaining the operation of the electrometer in the second embodiment.
In the second embodiment, the configuration other than the specific configuration described here has the same configuration contents as the configuration in the first embodiment described above, and exhibits the same operation. In the drawings, the same reference numerals indicate the same or corresponding parts.

In the first embodiment, the electrometer 2 is configured by the integrator 21, the comparator 22, and the electromagnetic relay 23. However, in the second embodiment, the integrator 21, the multistage wave height discriminator 24, and the electromagnetic wave as shown in FIG. The relay 23 is configured.
In FIG. 5 for explaining the operation of the electrometer 2 according to the second embodiment of the present invention, the multistage wave height discriminator 24 has a plurality of individual discrimination levels L ₁ , L ₂ , L ₃ , L ₄ , L ₅ ... L _m . (A in FIG. 5), and a plurality of individual discrimination levels L ₁ , L ₂ , L ₃ , L ₄ , which are provided in order at equal intervals from the voltage level L ₀ at which the output of the operational amplifier 21 starts charge accumulation. Each time L ₅ ... L _m is sequentially reached, the one-shot pulse P _s is output (b in FIG. 5). When the final individual discrimination level L _m is reached, the one-shot pulse P _s is output and the charge integrating capacitor 22 is output. The operation of discharging the accumulated charge and accumulating the charge again is repeated (c in FIG. 5).
Then, a count rate by the count value N and the measurement time of the one-shot pulse P _s T, and outputs the radioactivity concentration or dose rate R.

Here, the frequency of the one-shot pulse P _s output from the multi-stage wave height discriminator 24 is the same as the frequency of the one-shot pulse P _{s in} the first embodiment, but the individual discrimination levels L ₁ , L ₂ , L ₃ , L ₄ , L ₅ : It can be increased to a value obtained by multiplying the number of L _m .
For example, when the ionization current output from the ionization chamber is 10 ⁻¹⁴ A, the capacitance of the charge integration capacitor 212 is 10 pF, and the discharge discrimination voltage of the multistage wave height discriminator 24 is 1 V ,
Accumulated charge amount of pulses corresponding to L _m = capacitance × discharge discrimination voltage ^{= 10 × 10 -12 F × 1V} = 1 × 10 -11 coulombs
L _m pulses of a frequency corresponding to = the ionization current ÷ L corresponding to _m was accumulated charge amount ^{= 10 -14 A ÷ 1 × 10} -11 coulombs = 0.001s ^-1
Thus, the count obtained at a measurement time of 10,000 seconds is 10 counts, and the resolution at this time is 10%. By providing the individual discrimination voltage levels L ₁ , L ₂ , L ₃ , L ₄ , L ₅ ... L _m at an interval of 10 mV, for example, a resolution equivalent to the above can be obtained in a measurement time of 100 seconds. If the measurement time is 10,000 seconds, the resolution is 0.1%.

As described above, by replacing the comparator 22 of the electrometer 2 with the multistage wave height discriminator 24, the output of the electrometer 2 is increased without increasing the rate of missing due to the discharge reset in the charge storage capacitor 212 of the integrator 21. the frequency of the one-shot pulse _{P s} is, multiplied by the number of individual discrimination levels _{L 1, L 2, L 3} , L 4, L 5 ... L m of the multi-stage pulse height discriminator 24 to a discharge number of resets per unit time Therefore, the measurement range on the lower limit side of the radiation monitor can be expanded, and minute ionization current can be measured with high accuracy.

Also in the second embodiment, the measurement unit 3 calculates the count rate corresponding to the radiation dose based on the actual measurement time Tr obtained by subtracting the missing measurement time N × t ₁ ÷ m from the measurement time T. The influence of the measurement time N × t ₁ ÷ m can be eliminated, and the measurement range can be expanded to the upper limit side.
That is, the count rate corresponding to a radiation dose by a separate discrimination voltage level _{L 1, L 2, L 3} , L 4, L 5 ... one-shot pulse is generated in _{L m P s} count value N in the multi-stage pulse height discriminator 24 When obtaining n, the count rate n is obtained from the count value N and the actual measurement time Tr obtained by subtracting the missing measurement time N × t ₁ ÷ m from the measurement time T, and the count rate n = N ÷ Tr. The counting rate n corresponding to the radiation dose can be accurately obtained by eliminating the influence of the measurement time N × t ₁ ÷ m . Note that Tr at this time is Tr = T−N ÷ m (the number of individual discrimination level stages) × t ₁ .

(2A) According to the second embodiment of the present invention, radiation detecting means comprising a radiation detector 1 that detects radiation and outputs an ionizing current, inputs the ionizing current, and accumulates it in the charge integrating capacitor 212 as a charge. , The charge due to the ionization current is integrated by an integrator 21 having a charge integrating capacitor 212 and corresponds to a level difference of individual discrimination levels L ₁ , L ₂ , L ₃ , L ₄ , L ₅ ... L _m in the multistage wave height discriminator 24. and a signal generating means comprising electrometer 2 as a current / frequency converter means for generating a counting signal consisting of one-shot pulse P _s for each predetermined integral amount, generated by the signal generating means comprising the electrometer 2 and the one-shot pulse P _s count counted counting signal consisting of N and the measurement time by calculating the radiation dose from the T output Since the radiation dose output means comprising the measurement unit 3 for displaying the radiation dose as the fixed result on the display unit 4 is provided, it becomes possible to reduce the charge amount per pulse without increasing the missing measurement time associated with the discharge. Because it can speed up the response in the minute current region and improve the current resolution, it can measure the minute radiation dose with high accuracy and eliminates the influence of the missing measurement time due to the discharge operation. Can be provided with high accuracy.

(2B) according to the second embodiment according to the present invention, in the configuration of the (2A) sections wherein the radiation amount output means comprising measuring unit 3 is composed of a one-shot pulse P _s generated by the signal generating means The radiation dose is calculated and output based on the count value N obtained by counting the counting signal and the actual measurement time Tr obtained by subtracting the missing measurement time N × t ₁ ÷ m from the discharge operation from the measurement time T. Therefore, the amount of charge per pulse can be reduced without increasing the missing time associated with the discharge, the response in the minute current region can be made faster, and the current resolution can be improved. It can measure with accuracy, eliminates the effect of missing time due to discharge operation, can measure a wide range of radiation levels with high accuracy, and eliminates the effect of missing time due to discharge operation. The radiation monitor which can measure the radiation level of a range with high precision can be provided.

Embodiment 3 FIG.
A third embodiment of the present invention will be described with reference to FIGS. FIG. 6 is a block diagram showing the configuration of the radiation monitor according to the third embodiment. FIG. 7 is a diagram for explaining the radiation monitor switching operation in the third embodiment.
In the third embodiment, the configuration other than the specific configuration described here has the same configuration contents as the configuration in the first embodiment or the second embodiment described above, and exhibits the same operation. is there. In the drawings, the same reference numerals indicate the same or corresponding parts.

In the second embodiment, the electrometer 2 is configured by the integrator 21, the multistage wave height discriminator 24, and the electromagnetic relay 23. However, in the third embodiment, the electrometer 2 is replaced by the integrator 21 as shown in FIG. A one-shot pulse composed of a comparator 22, a multi-stage wave high discriminator 24, and an electromagnetic relay 23 and generated at individual discrimination voltage levels L ₁ , L ₂ , L ₃ , L ₄ , L _5, L _m in the multi-stage wave high discriminator 24. The count rate is obtained from the count value N of P _s (see FIG. 5) and the measurement time T, and the radioactivity concentration or dose rate R is output, and the comparator 22 is set to the final discrimination level L _m of the multistage wave height discriminator 24. corresponding Once beyond the operating voltage V _s of the discharged again charges the electric charges accumulated in the charge integration capacitor 212 outputs a one-shot pulse P _s as in the first embodiment It repeats the operation to accumulate.
Measurement unit 3, the one-shot pulse P _s that is output from the one-shot pulse P _s and multistage pulse height discriminator 24 output from the comparator 22, and inputs both of them, to measure the respective one-shot pulse P _s When the counting rate n is obtained and the ionization current increases and the counting rate n based on the output of the comparator 22 exceeds the predetermined value R1, the counting rate n used for the subsequent calculation is calculated as the counting rate based on the output of the comparator 24. To the count rate n based on the output of the comparator 22.
FIG. 7 is a diagram for explaining this switching operation. The output characteristic when the output is increased by the count rate n based on the output of the multistage wave height discriminator 24 is indicated by a characteristic line AU. When the count rate n exceeds a predetermined value R1, the output of the comparator 22 indicated by the characteristic line BU Based on the output characteristics.
After switching the count rate by increasing the ionization current, the ionization current decreases, and when returning from the count rate n based on the output of the comparator 22 to the count rate n based on the output of the multistage wave height discriminator 24, a characteristic line The output characteristic based on the output of the comparator 22 indicated by BD is switched by a predetermined value R2 smaller than the predetermined value R1, and becomes an output characteristic based on the output of the multistage wave height discriminator 24 indicated by the characteristic line AD.
As described above, by performing the switching at the predetermined value R2 lower than the switching value R1 with a hysteresis effect, it is possible to reliably prevent the hunting operation during the switching operation.
The switching value R1 and switch value R2 increases the frequency of the one-shot pulse P _s of the output of the multi-stage pulse height discriminator 24, the count rate of the apparent pulse each other connected does not appear the effect of choking phenomenon to lower numerical Selected by area.

As described above, with both of the comparator 22 and the multi-stage pulse height discriminator 24, respectively, and outputs a one-shot pulse P _s, the measurement unit 3 inputs the respective one-shot pulse P _s, count rate based on the respective input n is selected so that an accurate count rate n with few missing outputs can be output, and the measurement range upper limit can be prevented from being reduced because the measurement range lower limit is widened. An ionization chamber radiation monitor with a wide range can be obtained with high accuracy.

Also in the third embodiment, the measurement unit 3 calculates the count rate n corresponding to the radiation dose based on the actual measurement time obtained by removing the missing measurement time from the measurement time, thereby eliminating the influence of the missing measurement time. The measurement range can be expanded to the upper limit side.
That is, the count rate corresponding to a radiation dose by a separate discrimination voltage level _{L 1, L 2, L 3} , L 4, L 5 ... one-shot pulse is generated in _{L m P s} count value N in the multi-stage pulse height discriminator 24 When obtaining n, the count rate n is obtained from the count value N and the actual measurement time Tr obtained by subtracting the missing measurement time N × t ₁ ÷ m from the measurement time T, and the count rate n = N ÷ Tr. The counting rate n corresponding to the radiation dose can be accurately obtained by eliminating the influence of the measurement time N × t ₁ ÷ m .
Also, the case of obtaining a count rate n corresponding to the radiation dose by the count value N of the one-shot pulse P _s output from the comparator 22, the actual measured excluding the missing time N × t ₁ from the count value N and the measured time T By obtaining the count rate n from the time Tr and setting the count rate n = N ÷ Tr, the influence of the missing measurement time N × t ₁ can be eliminated, and the count rate n corresponding to the radiation dose can be accurately obtained. .

(3A) According to the third embodiment of the present invention, radiation detection means comprising the radiation detector 1 that detects radiation and outputs an ionization current, inputs the ionization current, and accumulates the charge integration capacitor 212 as charges. , The charge due to the ionization current is integrated by an integrator 21 having a charge integrating capacitor 212 and corresponds to a level difference of individual discrimination levels L ₁ , L ₂ , L ₃ , L ₄ , L ₅ ... L _m in the multistage wave height discriminator 24. to be one that outputs a count signal consisting of one-shot pulse P _s for each predetermined integral amount, the voltage value V corresponding to the integrated value of the charge, at equal intervals from the voltage level L ₀ of the charge accumulation start and it outputs a count signal consisting of one-shot pulse _{P s} for each sequentially reach a plurality of discrimination levels provided in order _{L 1, L 2, L 3} , L 4, L 5 ... L m The first signal generating means by the multistage wave height discriminator 24 as the current / frequency converting means, the voltage value V corresponding to the integrated value of the electric charge is the last discrimination of the multistage wave height discriminator 24 in the first signal generating means. by reaching the level L _m above set predetermined voltage value, and repeats the operation of accumulating discharged again charge the accumulated charges and outputs a count signal consisting of one-shot pulse P _s current / a second signal generating means by the comparator 22 as frequency converting means, the generated count signal consisting of the one-shot pulse P _s counted respectively by said first and second signal generating means, their total The one-shot pulse generated by the first and second signal generation means is calculated based on the numerical value N and the measurement time T, respectively. By comparing the radiation dose of each calculated by counting signal consisting of P _s, from the radiation amount by the comparator 22 is the radiation dose measurement result by the first signal generating means by the multi-stage pulse height discriminator 24 exceeds a predetermined value R1 Switched to the radiation dose measurement result by the second signal generating means by the comparator 22 and outputted, and when the radiation dose by the comparator 22 becomes equal to or less than the predetermined value R2, the multi-stage high discriminator from the radiation dose measurement result by the second signal generating means by the comparator 22 The radiation dose measurement results by the first and second signal generation means are switched and output on the display unit 4 based on a predetermined switching standard that is switched and output to the radiation dose measurement results by the first signal generation means by 24. Since the radiation dose output means comprising the measurement unit 3 is provided, the multistage wave height discriminator 2 as the first signal generation means One-shot by the current / frequency converter pulse P _s even at high radiation doses such as to overlap, one-shot pulse P of the current / frequency converter according to the comparator 22 as a second signal generating means whose frequency is reduced By switching and outputting the radiation dose according to the measurement result based on _s , the upper limit of the measurement range can be expanded while maintaining high-accuracy measurement. It is possible to provide a radiation monitor capable of measuring the radiation level with high accuracy.

(3B) According to the third embodiment of the present invention, in the configuration of the item (3A), the radiation dose output means including the measurement unit 3 is generated by the first and second signal generation means. by calculating the radiation dose based on the shot pulse P _s except during time measurement deleted by the discharging operation of the count signal from the counted count value N and the measurement time T containing real measurement time it was determined Tr to be output since, even at high radiation doses such as one-shot pulse P _s overlaps a current / frequency converter as a first signal generating means, the one-shot pulse of the second current / frequency conversion means frequency is reduced by outputting switching the radiation dose based on the P _s, it is possible to extend the measurement range upper limit to maintain the measurement precision, to eliminate the influence of missing time by the discharging operation It is possible to provide a radiation monitor that can measure a wide range of radiation levels with high precision.

It is a block diagram which shows the structure of the radiation monitor in Embodiment 1 by this invention. It is a diagram explaining operation | movement of the electrometer in Embodiment 1 by this invention. It is a flowchart which shows the calculation procedure of the measurement part in Embodiment 1 by this invention. It is a block diagram which shows the structure of the radiation monitor in Embodiment 2 by this invention. It is a diagram explaining operation | movement of the electrometer in Embodiment 2 by this invention. It is a block diagram which shows the structure of the radiation monitor in Embodiment 3 by this invention. It is a diagram for demonstrating the switching operation of the radiation monitor in Embodiment 3 by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Radiation detector, 2 Electrometer, 21 Integrator, 211 Operational amplifier, 212 Charge integration capacitor, 22 Comparator, 23 Electromagnetic relay, 231 Electromagnetic coil, 232 Contact, 24 Multistage wave height discriminator, 3 Measurement part, 4 Display part.

Claims (4)

Radiation detection means for detecting radiation and outputting an ionization current;
The ionization current is input and accumulated as a charge, and the voltage value corresponding to the integrated value of the charge is counted each time it sequentially reaches a plurality of discrimination levels provided in order from the voltage level at the start of charge accumulation at equal intervals. outputs use signal, a signal generating means for repeating the operation of accumulating the last to reach the discrimination level and the accumulated discharge and again charges the electric charges,
Radiation monitor, characterized in that a, the radiation amount output means for calculating and outputting a radiation dose based on the count value obtained by counting the count signal. Radiation detection means for detecting radiation and outputting an ionization current ;
Each time the ionization current is input and accumulated as a charge, the voltage value corresponding to the integrated value of the charge reaches each of a plurality of discrimination levels sequentially provided at equal intervals from the voltage level at which charge accumulation starts . First signal generating means for generating one counting signal ;
Each time the voltage value corresponding to the integrated value of the electric charge reaches the final discrimination level of the first signal generating means, a second counting signal is generated and the accumulated electric charge is discharged to recharge the electric charge. Second signal generating means for repeating the storing operation ;
Said first counting signal and the second count signal by counting each calculated radiation dose based on their count values, respectively, compared to predetermined switching criteria the radiation dose of the computed each the first signal generating means and the radiation amount output means and the radiation monitor, characterized in that a for switching and outputting radiation dose measurement result by the second signal generating means based on. Radiation amount output means, according to claim 1, characterized in that so as to calculate the radiation dose based on the actual measurement time calculated by excluding the missing time by the count value and the discharging operation of counting a counting signal Radiation monitor. The radiation dose output means calculates the radiation dose based on the count value obtained by counting the first counting signal and the second counting signal and the actual measurement time obtained by excluding the missing measurement time due to the discharge operation. The radiation monitor according to claim 2.

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