JP2013088266A - Radiation monitor - Google Patents

Abstract

A radiation monitor capable of performing highly accurate detection with reduced instrument errors related to standard deviation without sacrificing responsiveness is provided.
A counter 3 that counts radiation as a digital pulse at a constant cycle and outputs a count value, and a calculator 4 multiply the count rate of the previous calculation cycle from the current calculation cycle by the calculation cycle time. The addition / subtraction obtained by subtracting the value is added to the addition / subtraction integration value of the previous calculation cycle to obtain the addition / subtraction integration value of the current calculation cycle. Find the integrated natural number, compare the addition / subtraction integration natural number of the current calculation cycle with the addition / subtraction integration natural number of the previous calculation cycle, and if different, find the average value of the addition / subtraction integration natural number of the current calculation cycle and the previous calculation cycle, Multiply the average value by a weighting factor based on the standard deviation to calculate the standard deviation to be constant, or use the same as the count rate in the previous calculation cycle. , Alarm judgment Cormorant.
[Selection] Figure 1

Description

  The present invention relates to a radiation monitor used for emission management or radiation management of a nuclear reactor facility, a spent fuel reprocessing facility, etc., and in particular, compresses equipment errors.

The radiation monitor used in the conventional nuclear reactor facility, spent fuel reprocessing facility, etc. covers a wide range where the repetition frequency of the signal pulse as a result of detecting the radiation ranges from about 10 cpm to about 10 ⁷ cpm. There is a need to ensure the required accuracy without switching. Further, when the repetition frequency of the output pulse of the radiation detector changes from the background level to a high count rate region including a high alarm point, a response with a fast count rate is required. For this reason, the count rate obtained as a result of measuring it with respect to the repetition frequency of the input pulse is the first-order delay of the time constant so that the time constant changes in inverse proportion to the count rate and the standard deviation becomes constant. A mechanism for measuring the count rate by making the response and balancing the repetition frequency of the input pulse and the repetition frequency of the feedback pulse corresponding to the count rate has been widely introduced (see, for example, Patent Document 1).

JP-A-11-326523

  Since the conventional radiation monitor measures the counting rate with the above-mentioned, when the repetition frequency of each of the input pulse and the feedback pulse is balanced, fluctuations of up to one pulse input occur, which is preferable. When measuring the radiation dose with high responsiveness and high accuracy, there is a problem that the error inherent to the device increases depending on the standard deviation.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a radiation monitor in which instrument errors are compressed without sacrificing responsiveness.

The radiation monitor of the present invention is
Radiation detecting means for outputting an analog signal pulse when detecting radiation;
A pulse height discriminating means for inputting the analog signal pulse and outputting it as a digital pulse within an allowable range;
Counting means for inputting the digital pulse, counting at a fixed period, and outputting a count value;
Calculating the count rate of the fixed period, converting the count rate into an engineering value, and having an arithmetic means for performing a warning determination on the engineering value,
The calculation means calculates the count rate as follows:
Addition / subtraction obtained by subtracting the value calculated by multiplying the count rate of the previous calculation cycle by the calculation cycle time from the count value of the previous calculation cycle is added to the accumulated value of the previous calculation cycle to add or subtract the current calculation cycle. As an integrated value, an addition / subtraction integration natural number obtained by rounding down the decimals of the addition / subtraction integration value of the current calculation cycle is calculated, and the addition / subtraction integration natural number of the current calculation cycle is compared with the addition / subtraction integration natural number of the previous calculation cycle,
If they are different, the average value of the addition / subtraction integration natural number of the current calculation cycle and the addition / subtraction integration natural number of the previous calculation cycle are obtained, and the standard deviation is made constant by multiplying the average value by a weighting factor based on the standard deviation. To calculate the counting rate,
In the same case, the count rate of the previous calculation cycle is set as the count rate of the current calculation cycle.

The radiation monitor of the present invention is
Radiation detecting means for detecting radiation and outputting analog signal pulses;
A pulse height discriminating means for inputting the analog signal pulse and outputting it as a digital pulse within an allowable range;
Addition input of the digital pulse, subtraction input of the feedback pulse output from the pulse generation means, addition / subtraction integration means for outputting the result as an addition / subtraction integration value,
Integration control means for weighting and integrating the digital pulse and feedback pulse input to the addition / subtraction integration means based on a standard deviation;
Pulse generating means for outputting a repetition frequency that responds with a first order delay of a time constant to the repetition frequency of the digital pulse as the feedback pulse to the addition / subtraction integration means;
A calculation rate is calculated at a fixed period, the count rate is converted into an engineering value, and an arithmetic means for performing alarm determination on the engineering value is provided.
The calculation means calculates the count rate as follows:
Compare the accumulated value of the previous calculation cycle with the accumulated value of the current calculation cycle,
If they are different, the average value of the addition / subtraction integration value of the previous calculation cycle and the addition / subtraction integration value of the current calculation cycle is obtained, and the average value is calculated so that the standard deviation is constant to obtain the count rate. Or
In the same case, the count rate of the previous calculation cycle is set as the count rate of the current calculation cycle.

The radiation monitor of the present invention is
Radiation detecting means for outputting an analog signal pulse when detecting radiation;
A pulse height discriminating means for inputting the analog signal pulse and outputting it as a digital pulse within an allowable range;
Counting means for inputting the digital pulse, counting at a fixed period, and outputting a count value;
Calculating the count rate of the fixed period, converting the count rate into an engineering value, and having an arithmetic means for performing a warning determination on the engineering value,
The calculation means calculates the count rate as follows:
Addition / subtraction obtained by subtracting the value calculated by multiplying the count rate of the previous calculation cycle by the calculation cycle time from the count value of the previous calculation cycle is added to the accumulated value of the previous calculation cycle to add or subtract the current calculation cycle. As an integrated value, an addition / subtraction integration natural number obtained by rounding down the decimals of the addition / subtraction integration value of the current calculation cycle is calculated, and the addition / subtraction integration natural number of the current calculation cycle is compared with the addition / subtraction integration natural number of the previous calculation cycle,
If they are different, the average value of the addition / subtraction integration natural number of the current calculation cycle and the addition / subtraction integration natural number of the previous calculation cycle are obtained, and the standard deviation is made constant by multiplying the average value by a weighting factor based on the standard deviation. To calculate the counting rate,
In the case of the same, since the count rate of the previous calculation cycle is the count rate of the current calculation cycle,
It is possible to perform highly accurate detection with reduced instrument errors related to standard deviation without sacrificing responsiveness.

The radiation monitor of the present invention is
Radiation detecting means for detecting radiation and outputting analog signal pulses;
A pulse height discriminating means for inputting the analog signal pulse and outputting it as a digital pulse within an allowable range;
Addition input of the digital pulse, subtraction input of the feedback pulse output from the pulse generation means, addition / subtraction integration means for outputting the result as an addition / subtraction integration value,
Integration control means for weighting and integrating the digital pulse and feedback pulse input to the addition / subtraction integration means based on a standard deviation;
Pulse generating means for outputting a repetition frequency that responds with a first order delay of a time constant to the repetition frequency of the digital pulse as the feedback pulse to the addition / subtraction integration means;
A calculation rate is calculated at a fixed period, the count rate is converted into an engineering value, and an arithmetic means for performing alarm determination on the engineering value is provided.
The calculation means calculates the count rate as follows:
Compare the accumulated value of the previous calculation cycle with the accumulated value of the current calculation cycle,
If they are different, the average value of the addition / subtraction integration value of the previous calculation cycle and the addition / subtraction integration value of the current calculation cycle is obtained, and the average value is calculated so that the standard deviation is constant to obtain the count rate. Or
In the case of the same, since the count rate of the previous calculation cycle is the count rate of the current calculation cycle,
It is possible to perform highly accurate detection with reduced instrument errors related to standard deviation without sacrificing responsiveness.

It is a block diagram which shows the structure of the radiation monitor of Embodiment 1 of this invention. It is a flowchart which shows the arithmetic processing of the calculator of the radiation monitor shown in FIG. It is a block diagram which shows the structure of the radiation monitor of Embodiment 2 of this invention. It is a flowchart which shows the arithmetic processing of the calculator of the radiation monitor shown in FIG. It is a block diagram which shows the structure of the radiation monitor of Embodiment 3 of this invention. It is a figure which shows the input / output characteristic of the calculator of the radiation monitor shown in FIG. It is a flowchart which shows the arithmetic processing of the calculator of the radiation monitor shown in FIG. It is a block diagram which shows the structure of the radiation monitor of Embodiment 4 of this invention. It is a figure which shows the timing chart of the radiation monitor shown in FIG.

Embodiment 1 FIG.
Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing a configuration of a radiation monitor according to Embodiment 1 of the present invention, and FIG. 2 is a flowchart showing a calculation process of a calculator of the radiation monitor shown in FIG. In FIG. 1, a radiation detector 1 serving as radiation detecting means for outputting an analog signal pulse when radiation is detected, and an analog signal pulse output from the radiation detector 1 are input, and the analog signal pulse is within an allowable range. For example, if the voltage level of the analog signal pulse is equal to or higher than the set level, or is within the set level range, the input analog signal pulse is regarded as being within the allowable range. A pulse height discriminator 2 is provided as a pulse height discriminating means that outputs a digital pulse and deviates from other set conditions and regards the input analog signal pulse as noise and does not output the digital pulse.

  Further, the digital pulse output from the wave height discriminator 2 is input, the counter 3 as a counting means for counting at a constant cycle and outputting the count value ΔN, and the count value ΔN (current count) output from the counter 3 ( This time, based on the standard deviation and the count rate, the count rate is calculated at regular intervals, the count rate is converted into an engineering value, the engineering value is judged as an alarm, and the engineering value and the alert judgment result are output. While displaying the arithmetic unit 4 as a means, the memory 5 for storing the calculation procedure necessary for the calculation of the arithmetic unit 4, each set value, data, etc., the engineering value and the alarm judgment result output from the arithmetic unit 4, It is comprised with the indicator 6 which can perform operation, such as setting value input and alarm reset, from a screen. The engineering value may be the counting rate itself (counting rate = engineering value) depending on the application, or may be a product of the engineering value multiplied by a constant for converting the radiation dose. Here, for the sake of convenience of explanation, the case of engineering value = counting rate will be described.

Next, the operation of the radiation monitor of the first embodiment configured as described above will be described.
First, the calculation for obtaining the count rate m with a constant standard deviation in the calculator 4 will be described. The count rate of the previous calculation cycle is m (previous), the addition / subtraction integrated value of the previous calculation cycle is M (previous), the counter value of the counter for each calculation cycle is ΔN, the count time (refers to the calculation cycle time) is ΔT, this time The integration value of the calculation cycle is M (current), the natural number of the previous calculation cycle is rounded down to the natural number M (previous: natural number), and the decimal point of the current cycle of the addition / subtraction integration value is rounded down. The natural number is M (current time: natural number), and the count rate of the current calculation cycle is m (current time). M (current) and m (current) can be obtained by the following equations (1) and (2), respectively.
M (current) = M (previous) + {ΔN (current) −m (previous) × ΔT} (1)
m (current) = exp {γ ₁ × 2 ^α × M (current: natural number average value)} (2)

The count rate m (current) obtained by the above equation (2) is controlled with a standard deviation σ = constant as shown in the following equation (3).
σ = 1 / (2mτ) ^1/2 = constant (3)
The time constant τ is inversely proportional to the count rate m, inversely proportional to the square of the standard deviation, and inversely proportional to γ, as shown in the following equation (4). γ is proportional to the square of the standard deviation as shown in the following equation (5), and is obtained from the above equation (2) by, for example, counting by weighting with 2α using a constant α relating to the weighting of the count. The count rate m (current time) responds by following the change in the repetition frequency of the output pulse of the wave height discriminator 2 with a first order delay of the time constant τ.
τ = 1 / (2mσ ² ) = 1 / (mγ) (4)
γ = 2σ ² = 2 ^α × 2 ⁻¹¹ × ln2 = γ ₁ × 2 ^α = constant (5)

By weighting the count by 2 ^alpha in the above (2), when the reference weighted ² 0 = 1 alpha = 0, weighting ² 2 = 4 counts alpha = 2, tau is 1/4, alpha = When the weighting of 4 is 2 ⁴ = 16, τ is 1/16, the weighting of α = 6 is 2 ⁶ = 64, and τ is 1/64.

  Next, the calculation processing procedure of the calculator 4 of the radiation monitor according to the first embodiment configured as described above will be described with reference to FIG. First, α, high alarm set value, low alarm set value, m (previous), M (previous), M (previous: natural number), and ΔN (current) are input from the memory 5 (step S1 in FIG. 2). Next, M (current) is obtained by the above equation (1) (step S2 in FIG. 2). Next, M (current: natural number) obtained by rounding down the decimal point of M (current) is obtained (step S3 in FIG. 2), and it is determined whether M (current: natural number) ≠ M (previous: natural number) ( Step S4 in FIG. Next, if different (YES), M (current: natural number average value) = {M (previous: natural number) + M (current: natural number)} / 2 is obtained (step S5 in FIG. 2). Next, based on M (current: natural number average value), m (current) is obtained by the above equation (2) (step S6 in FIG. 2).

  On the other hand, if they are the same in step S4 (NO), m (previous) is output as m (present) (step S7 in FIG. 2). Next, it is determined whether m (current) ≧ high alarm set value (step S8 in FIG. 2). Next, if YES, a high alarm is output (step S9 in FIG. 2), for example, the display 6 indicates that the alarm is high, ends the current calculation cycle, and returns to step S1. On the other hand, if NO in step S8, it is determined whether m (current) ≤ low alarm set value (step S10 in FIG. 2). Next, if YES, a low alarm is output (step S11 in FIG. 2), for example, the display 6 indicates that the alarm is low, ends the current calculation cycle, and returns to step S1. On the other hand, if “NO” in the step S10, the current calculation cycle is ended and the process returns to the step S1.

The count rate is calculated with σ = constant so that the count rate becomes the standard deviation σ determined by the request from the measurement accuracy from the measurement range lower limit to the measurement range upper limit. In applications where a low count rate is measured, responsiveness is given priority and a large standard deviation is set. For example, error compression when the standard deviation σ is as large as 0.104 will be described. The weight of the count determined corresponding to the standard deviation of 0.104 is 2 ⁶ = 64. In the above equation (2), M (current: natural number average value) is multiplied by the count weight 64, and further the constant γ ₁ is multiplied. The counting rate m (this time) is obtained based on the obtained information. In the above equation (5), γ ₁ can be obtained as “2 ⁻¹¹ × ln2 = constant”, and becomes “3.38 × 10 ⁻⁴ ”. When 10.0 cpm, M is “ln (count rate) / γ = ln10 / (3.38 × 10 ⁻⁴ ) = 6812”, and when M is increased by the count weight 64, the count rate is “exp (3. 38 × 10 ⁻⁴ × 6876) = 10.2 cpm ″.

If the count rate is calculated based on M (current time: natural number) in an equilibrium state, it will fluctuate between 10.0 cpm and 10.2 cpm, but if M (current time: natural number) changes from M (previous: natural number), M ( The count rate is stabilized at “exp (3.38 × 10 ⁻⁴ × 6844) = 10.1 cpm” by calculating the count rate based on the current value (natural number average value). For example, if the calculation cycle is 1 second, one pulse is added to the addition / subtraction integrated value every 6 seconds in a 10 cpm equidistant pulse train, and 1 pulse is subtracted every 6 seconds, including the timing of addition / subtraction of 1 pulse. The count rate is stable at all timings.

  According to the radiation monitor of the first embodiment configured as described above, the arithmetic unit calculates the average value when the natural number obtained by rounding down the decimal point of the addition / subtraction integrated value changes from the previous calculation cycle to the current calculation cycle. Since the count rate is calculated based on the above, when the input repetition frequency is in an equilibrium state, the count rate can be stabilized at all timings, and the equipment related to the standard deviation without sacrificing responsiveness It is possible to measure radiation with high accuracy by reducing errors.

Embodiment 2. FIG.
In the first embodiment, the counter 3 counts the digital pulses output from the wave height discriminator 2 at a constant cycle and outputs a count value ΔN, and the calculator 4 counts the current calculation cycle output from the counter 3. Although the count rate is calculated at regular intervals based on the numerical value ΔN (current) and the standard deviation, in the second embodiment, an up / down counter 7 and an integration control circuit 8 are used instead of the counter 3 as shown in FIG. And a pulse generator 9.

  The up / down counter 7 inputs the digital pulse output from the pulse height discriminator 2 to the addition input terminal 71, inputs the feedback pulse output from the pulse generator 9 to the subtraction input terminal 72, and adds or subtracts the result. Output the integrated value. The integration control circuit 8 controls the up / down counter 7 so that the addition input and subtraction input of the up / down counter 7 are counted based on the standard deviation. The pulse generator 9 connects a frequency divider 92 to the output of the clock 91, connects a rate multiplier 93 to the output of the frequency divider 92, and inputs the addition / subtraction integrated value output from the up / down counter 7. The frequency divider 92 and the rate multiplier 93 are controlled, converted to a repetition frequency of the output pulse of the rate multiplier 93, and input to the subtraction input terminal 72 of the up / down counter 7 as a feedback pulse. Note that the clock 91 may be shared with a clock (not shown) provided as a standard in the arithmetic unit 4.

Next, the operation of the radiation monitor of the second embodiment configured as described above will be described.
First, the arithmetic unit 4 inputs the addition / subtraction integrated value M (current) of the current calculation cycle output from the up / down counter 7, calculates M (current: average value) as shown in the flowchart of FIG. Based on the value, the count rate is obtained by equation (6). The counting weights of the addition input and the subtraction input of the up / down counter 7 are the same as those in the first embodiment, and the description thereof is omitted.
m (current) = exp {γ ₁ × 2α × M (current: average value)} (6)

  Next, the calculation processing procedure of the calculator of the radiation monitor according to the second embodiment configured as described above will be described with reference to FIG. First, α, high alarm set value, low alarm set value, m (previous), M (previous), M (previous: average value), and M (current) are input from the memory 5 (step S21 in FIG. 4). Next, it is determined whether or not M (current) ≠ M (previous) (step S22 in FIG. 4). Next, if different (YES), M (current: average value) = {M (previous) + M (current)} / 2 is obtained (step S23 in FIG. 4). Next, m (current) is obtained by the above equation (6) based on M (current: average value) (step S24 in FIG. 4). On the other hand, if they are the same (NO), m (previous) is output as m (present) (step S25 in FIG. 4).

  Next, it is determined whether m (current) ≧ high alarm set value by the same operation as in the first embodiment (step S8 in FIG. 4). Next, if YES, a high alarm is output (step S9 in FIG. 4), for example, the display 6 indicates that the alarm is high, ends the current calculation cycle, and returns to step S21. On the other hand, if NO in step S8, it is determined whether m (current) ≦ low alarm set value (step S10 in FIG. 4). Next, if YES, a low alarm is output (step S11 in FIG. 4), for example, the display 6 indicates that the alarm is low, ends the current calculation cycle, and returns to step S21. On the other hand, if “NO” in the step S10, the current calculation cycle is ended and the process returns to the step S21.

  For example, if the calculation cycle is 1 second, one pulse is added to the addition / subtraction integrated value every 6 seconds in a 10 cpm equidistant pulse train, and 1 pulse is subtracted every 6 seconds, including the timing of addition / subtraction of 1 pulse. The count rate is stable at all timings.

  In the radiation monitor according to the second embodiment configured as described above, when the addition / subtraction integrated value changes from the previous calculation cycle to the current calculation cycle, the calculator calculates the count rate based on the average value. Therefore, when the input repetition frequency is in an equilibrium state, the count rate can be stabilized at all timings, and the instrument error related to the standard deviation can be reduced without sacrificing responsiveness, and radiation can be performed with high accuracy. Can be measured.

Embodiment 3 FIG.
In the second embodiment, the up / down counter 7 outputs the addition / subtraction integrated value M. However, in the third embodiment, the up / down counter 7 includes the mantissa part 73 and the exponent part 74 as shown in FIG. And the addition / subtraction integration value C of the mantissa part 73 and the addition / subtraction integration value E of the exponent part 74 are respectively output. Then, the arithmetic unit 4 obtains a count rate r approximated to an exponential function by the following equation (7) as shown in FIG. 6 when A = constant and B = constant. Note that the weighting of the C count is the same as in the second embodiment, and a description thereof will be omitted.
r (current) = {A + C (current: average value)} / B × 2 ^{E (current)} (7)

Next, the calculation processing procedure of the calculator of the radiation monitor according to the third embodiment configured as described above will be described with reference to FIG. First, α, high alarm set value, low alarm set value, r (previous), C (previous), C (previous: average value), and C (current) are input to the memory 5 (step S41 in FIG. 7). Next, it is determined whether or not C (current) .noteq.C (previous) (step S42 in FIG. 7).
If they are different (YES), C (current: average value) = {C (previous) + C (current)} / 2 is obtained (step S43 in FIG. 7). Next, r (current) is obtained by the above equation (7) based on C (current: average value) (step S44 in FIG. 7).

  On the other hand, if they are the same (NO), r (previous) is output as r (current) (step S45 in FIG. 7). Next, it is determined whether r (current) ≧ high alarm set value by the same operation as in the above embodiments (step S46 in FIG. 7). If YES, a high alarm is output (step S9 in FIG. 7), for example, the display 6 indicates that the alarm is high, ends the current computation cycle, and returns to step S41. On the other hand, if NO in step S8, it is determined whether r (current) ≦ low alarm set value (step S48 in FIG. 7). On the other hand, if NO in step S8, it is determined whether r (current) ≤ low alarm set value (step S48 in FIG. 7). Next, if YES, a low alarm is output (step S11 in FIG. 7), for example, the display 6 indicates that the alarm is low, ends the current calculation cycle, and returns to step S41. On the other hand, if “NO” in the step S48, the current calculation cycle is ended and the process returns to the step S41.

  In the radiation monitor according to the third embodiment configured as described above, the computing unit counts based on the average value when the addition / subtraction integrated value of the mantissa part of the up / down counter changes from the previous computation cycle to the current computation cycle. Since the rate is calculated, when the input repetition frequency is in a balanced state, the count rate can be stabilized at all timings, and the instrument error related to the standard deviation is reduced without sacrificing responsiveness. Radiation can be measured with high accuracy.

Embodiment 4 FIG.
In the second embodiment, the divider 92 is connected to the output of the clock 91 in the pulse generator 9, the rate multiplier 93 is connected to the output of the divider 92, and the feedback pulse of the rate multiplier 93 is increased. In the fourth embodiment, as shown in FIG. 8, the pulse generator 90 connects the rate multiplier 930 to the output of the clock 91, and the rate is input to the subtraction input terminal 72 of the down counter 7. A frequency divider 920 is connected to the output of the multiplier 930, and a feedback pulse of the frequency divider 920 is input to the subtraction input terminal 72 of the up / down counter 7.

  Since control is performed in this way, as shown in FIG. 9, the rate multiplier 930 first extracts a predetermined number of output pulses in a certain period of time at random. Next, this extracted pulse is applied to a frequency divider 920 to obtain a feedback pulse. This feedback pulse has an error equivalent to the number of cycles of the clock signal, but when the repetition frequency is high, it is a negligible ratio with respect to the number of pulses in the calculation cycle, and when the repetition frequency is low, the pulse interval is It can be fixed. The operations other than the pulse generator 90 can be performed in the same manner as in the second embodiment.

  According to the radiation monitor of the fourth embodiment configured as described above, the same effects as those of the second embodiment can be obtained, but accuracy is required in the low count rate region. For example, a PWR plant In the background of 4 to 10 cpm of the high-sensitivity main steam pipe monitor, the interval between the feedback pulses of the subtraction input can be made equal, so that when the input repetition frequency is in a balanced state, the addition input of the up / down counter is Since the alternation with the subtraction input is maintained, the count rate can be stabilized at all timings, and the instrument error related to the standard deviation can be reduced without sacrificing responsiveness, and radiation can be measured with high accuracy. .

  It should be noted that the present invention can be appropriately modified and omitted in each embodiment within the scope of the present invention.

1 radiation detector, 2 wave height discriminator, 3 counter, 4 arithmetic unit, 5 memory,
6 display, 7 up / down counter, 8 integration control circuit, 9 pulse generator,
71 Addition input terminal, 72 Subtraction input terminal, 73 Mantissa part, 74 Exponential part,
91 clock, 92,920 divider, 93,930 rate multiplier.

Claims (8)

Radiation detecting means for outputting an analog signal pulse when detecting radiation;
A pulse height discriminating means for inputting the analog signal pulse and outputting it as a digital pulse within an allowable range;
Counting means for inputting the digital pulse, counting at a fixed period, and outputting a count value;
Calculating the count rate of the fixed period, converting the count rate into an engineering value, and having an arithmetic means for performing a warning determination on the engineering value,
The calculation means calculates the count rate as follows:
Addition / subtraction obtained by subtracting the value calculated by multiplying the count rate of the previous calculation cycle by the calculation cycle time from the count value of the previous calculation cycle is added to the accumulated value of the previous calculation cycle to add or subtract the current calculation cycle. As an integrated value, an addition / subtraction integration natural number obtained by rounding down the decimals of the addition / subtraction integration value of the current calculation cycle is calculated, and the addition / subtraction integration natural number of the current calculation cycle is compared with the addition / subtraction integration natural number of the previous calculation cycle,
If they are different, the average value of the addition / subtraction integration natural number of the current calculation cycle and the addition / subtraction integration natural number of the previous calculation cycle are obtained, and the standard deviation is made constant by multiplying the average value by a weighting factor based on the standard deviation. To calculate the counting rate,
In the case of being the same, the radiation monitor characterized in that the count rate of the previous computation cycle is set to the count rate of the current computation cycle. Radiation detecting means for detecting radiation and outputting analog signal pulses;
A pulse height discriminating means for inputting the analog signal pulse and outputting it as a digital pulse within an allowable range;
Addition input of the digital pulse, subtraction input of the feedback pulse output from the pulse generation means, addition / subtraction integration means for outputting the result as an addition / subtraction integration value,
Integration control means for weighting and integrating the digital pulse and feedback pulse input to the addition / subtraction integration means based on a standard deviation;
Pulse generating means for outputting a repetition frequency that responds with a first order delay of a time constant to the repetition frequency of the digital pulse as the feedback pulse to the addition / subtraction integration means;
A calculation rate is calculated at a fixed period, the count rate is converted into an engineering value, and an arithmetic means for performing alarm determination on the engineering value is provided.
The calculation means calculates the count rate as follows:
Compare the accumulated value of the previous calculation cycle with the accumulated value of the current calculation cycle,
If they are different, the average value of the addition / subtraction integration value of the previous calculation cycle and the addition / subtraction integration value of the current calculation cycle is obtained, and the average value is calculated so that the standard deviation is constant to obtain the count rate. Or
In the case of being the same, the radiation monitor characterized in that the count rate of the previous computation cycle is set to the count rate of the current computation cycle. 3. The radiation monitor according to claim 2, wherein the addition / subtraction integration means is constituted by an up / down counter. 4. The radiation monitor according to claim 3, wherein the up / down counter comprises a mantissa part and an exponent part. The pulse generating means connects a rate multiplier to the output of the clock,
A divider is connected to the output of the rate multiplier,
The radiation monitor according to any one of claims 2 to 4, wherein the pulse output from the frequency divider is the feedback pulse. The radiation monitor according to any one of claims 1 to 5, wherein the wave height discriminating means removes the wave height level of the input analog signal pulse as noise when the wave height level deviates from an allowable range. The arithmetic means outputs the engineering value and the alarm determination result,
The radiation monitor according to any one of claims 1 to 6, further comprising display means for displaying an output from the arithmetic means. The radiation monitor according to any one of claims 1 to 7, further comprising a storage means for storing a calculation procedure of the calculation means and set values and data necessary for the calculation.

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