JP5373720B2 - Radiation monitoring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation monitor device that greatly shorten a test time, and changes test items according to circumstances by automatically and sequentially optimizing the frequency of a test pulse. <P>SOLUTION: A measurement unit 12 in which a detection pulse is input to measure a counting rate (n) comprises: a pulse amplifier 11 in which the detection pulse is input to amplify the detection pulse; a pulse height discriminator 122 which outputs a digital pulse when the voltage of the amplified detection pulse is within a predetermined range; a counter 123 which inputs the digital pulse to an addition input unit 123a and a feedback pulse to a subtraction input unit 123b, and outputs an integrated value M obtained by integrating the difference between the both; a frequency synthesis circuit 124 in which the integrated value M is input to generate the feedback pulse; an integration control circuit 125 which performs weighting when the counter 123 counts; a computing element 126 in which the integrated value M is input to find a counting rate (n); a changeover switch 128 which changes over the input to the pulse amplifier 121; and a changeover switch 129 which changes over the subtraction input to the counter 123. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a radiation monitoring apparatus used for radioactive material release management or radiation management in a nuclear reactor facility, a spent fuel reprocessing facility, or the like.

  Conventional radiation monitoring devices used in nuclear reactor facilities, spent fuel reprocessing facilities, etc., have a detector that detects radiation and outputs a detection signal pulse, and a measurement that inputs the detection signal pulse and measures the count rate. A radiation monitor having a plurality of channels, a test signal generator for inputting a test signal pulse to each radiation monitor, a frequency of the test signal pulse of the test signal generator, and a detection signal pulse in the radiation monitor; And a control unit that switches the input of the test signal pulse. The control unit operates the input selector switch of the measurement unit to switch the input from the detection signal pulse to the test signal pulse, and performs the input / output response test and alarm test individually. Has confirmed the soundness of radiation monitors.

  Each radiation monitor calculates the radiation dose by converting the measured count rate into an engineering value, a high alarm is set at a radiation dose level higher than the normal background level, and the radiation dose rate or process system in the management area of the facility. It is a system that automatically alerts the operator by sending a high alarm to the radioactivity abnormality and automatically isolates the necessary system. In addition, a low alarm is set at a radiation level lower than the normal background level, and a low alarm is issued to notify the operator when the detector signal is lost or the count rate of the detector signal is reduced due to a radiation monitor failure. Like to do.

  The accuracy of the instruction response of the radiation monitor and the accuracy of the alarm operation are confirmed by inputting a test pulse to the measurement unit, and the control unit transmits the test pulse of the test signal generation unit according to the test item. The frequency is changed in steps or ramps. During the test period, the alarm is blocked before the start of the test so that the high and low alarms are not output from the radiation monitoring apparatus to the outside, and the block is released after the end of the test. These operations are performed manually, and an alarm is output during the test while the alarm is blocked.

On the other hand, since the radiation dose measured by the radiation monitor fluctuates statistically, the predetermined measurement accuracy is maintained by automatically controlling the time constant according to the counting rate so that the standard deviation is constant. . In addition, the measurement unit is required to measure over a wide range of counting rates from about 10 cpm to about 10 ⁷ cpm. In order to eliminate discontinuities associated with range switching, the wide range can be used without range switching. Counting rate measurement is performed using an up / down counter that operates at high speed.

  The count rate measurement using this up / down counter is to calculate the count rate by reading the integrated value of the difference between the addition input and the subtraction input at a certain period. The addition input is the detection input from the detector to the measurement unit. A digital pulse that is obtained by amplifying a signal pulse and satisfying a predetermined peak value. The subtraction input is a digital pulse generated by frequency-synthesizing the clock pulse of the crystal oscillator based on the integrated value. In particular, it is characterized by being able to measure with high accuracy, especially up to a high count rate.

Count rate measurement using the above-mentioned up / down counter responds with a time constant, so the input / output response test to check the output accuracy by inputting a test pulse for each decard, and alarm operation by inputting the test pulse Since it takes time to check the alarm, it is possible to optimize the step change time and step duration by combining the test pulse changing stepwise and the ramp changing for each test item. Yes. Then, by optimizing the ramp inclination and duration and setting in advance so as to be input sequentially, a contrivance is made to shorten the response time of the count rate with respect to the test pulse input (see, for example, Patent Document 1). ).

Japanese Patent Laid-Open No. 10-260262

  In the measurement method disclosed in Patent Document 1, an excessive step input and a subsequent ramp input pattern are set in advance for a typical test input, and a test pulse is automatically input according to the input pattern. It is a thing. However, even if this method is used, if the target value of the repetition frequency of the test pulse is higher than the current value, the test time is reduced accordingly, but if the target value of the repetition frequency of the test pulse is lower than the current value, it still remains. Requires a long time. For example, when the standard deviation is 2.6%, the lower limit of the measurement range is 10 cpm, and the background is 50 cpm, it takes about 40 minutes to make the test pulse input 1 cpm stepwise and close to 10 cpm. Even 0 cpm does not improve significantly.

  As described above, the conventional radiation monitoring device shortens the test time by devising the test pulse input method. However, in the integrated value of the up / down counter, the test pulse contributes only to the addition input, and the subtraction input. In addition, since the test pulse is input in a state where the addition input and the subtraction input function, it is difficult to control the precise test pulse to reach the target value in a short time. For this reason, most of the channels are in continuous measurement during facility operation, and there are channels that require continuous operation even during the facility inspection period. There is a need for improvement. In particular, the test item with a low count rate has a problem that the test takes a long time because the time constant is inversely proportional to the count rate and only waiting for the integrated value to decrease with the time constant.

  In addition, when the planned test item is changed in the middle, it is necessary to set a test input pattern in accordance with the indicated value and the changed test item, and there is a problem in quick response.

  The present invention has been made to solve the above-described problems, and provides a radiation monitoring apparatus capable of changing test items flexibly by reducing test time significantly and automatically and automatically optimizing test pulse frequencies. For the purpose.

A radiation monitoring apparatus according to the present invention includes a radiation detector that detects radiation and outputs a detection signal pulse, a measurement unit that receives the detection signal pulse and measures a count rate, and a test signal generation that generates a test pulse A radiation monitoring apparatus comprising: a control unit that controls a transmission frequency of a test pulse output from the test unit and the test signal generator, and a control unit that switches and controls an input of the measurement unit;
The measurement unit includes a pulse amplifier that inputs and amplifies the detection signal pulse, a pulse height discriminator that outputs a digital pulse when the voltage of the amplified detection signal pulse is within a predetermined range, an addition input unit, and a subtraction An up / down counter that has an input unit, inputs the digital pulse to the addition input unit, inputs a feedback pulse to the subtraction input unit, and outputs an integrated value obtained by integrating the difference between the two, and the integrated value A frequency synthesizing circuit for generating the feedback pulse upon input, an integration control circuit for weighting when the up / down counter counts, an arithmetic means for inputting the integrated value to obtain the count rate, and the pulse amplifier And a second switching means for switching a subtraction input of the up / down counter ,
Each of the first switching means and the second switching means has three positions: a measurement position that enables input measurement, an input cutoff position that blocks input, and a test input position that enables measurement of the test pulse. And in the normal mode, the control unit passes the detection signal pulse with the first switching means set to the measurement position, and passes a feedback pulse with the second switching means set to the measurement position. In the mode, the frequency of the test pulse is determined based on the target count rate, the latest count rate, and the weighting constant when the up / down counter counts, and the positions of the first switching means and the second switching means are determined. Determining and controlling the test pulse generation frequency of the test signal generator and the first switching Stage and by switching the position of the second switching means in a radiation monitoring device designed to enter the test pulse to the measuring unit,
In the test mode, the control unit is an A mode in which the first switching means is the test input position and the second switching means is the input cutoff position, and the first switching means is the test input position. A C mode in which the second switching means is the measurement position, the first switching means is the input cutoff position, and the second switching means is the test input position. 4 switching control modes of the D mode in which the switching means and the second switching means are the input cutoff position, and the test pulse is input based on the frequency of the test pulse calculated and the switching control mode. It is what you do .

  According to the radiation monitoring apparatus of the present invention, the control unit determines from the current value of the integrated value of the up / down counter and the target value, and switches the input of the test pulse so as to operate with either the addition input or the subtraction input. Since the control is performed, precise control for accurately reaching the target value in a short time becomes possible, and control for automatically and sequentially optimizing the frequency of the test pulse becomes possible. For this reason, it is possible to provide a radiation monitoring apparatus that can greatly reduce the test time and can change the test items as needed.

It is a block block diagram of the radiation monitoring apparatus which concerns on Embodiment 1 of this invention. It is a flowchart explaining operation | movement of the control part of the radiation monitoring apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the test pulse frequency change and count rate response of the radiation monitoring apparatus which concerns on Embodiment 1 of this invention. It is a flowchart explaining operation | movement of the control part of the radiation monitoring apparatus which concerns on Embodiment 2 of this invention. It is a flowchart explaining operation | movement of the control part of the radiation monitoring apparatus which concerns on Embodiment 3 of this invention. It is a flowchart explaining operation | movement of the measurement part of the radiation monitoring apparatus which concerns on Embodiment 4 of this invention. It is a flowchart explaining operation | movement of the control part of the radiation monitoring apparatus which concerns on Embodiment 5 of this invention. It is a block block diagram of the radiation monitoring apparatus which concerns on Embodiment 6 of this invention. It is a block block diagram of the radiation monitoring apparatus which concerns on Embodiment 7 of this invention. It is a block block diagram of the radiation monitoring apparatus which concerns on Embodiment 8 of this invention.

  Preferred embodiments of a radiation monitoring apparatus according to the present invention will be described below with reference to the accompanying drawings. Note that the present invention is not limited to this embodiment, and includes various design changes.

Embodiment 1 FIG.
1 is a block diagram showing a radiation monitoring apparatus according to Embodiment 1 of the present invention. The radiation monitor 1 includes a radiation detector 11 that outputs a detection signal pulse that detects radiation, and a measurement unit 12 that receives the detection signal pulse from the radiation detector 11 and measures a count rate, and generates a test signal during a test. A test pulse is input from the unit 2 to the measuring unit 12. The control unit 3 controls the oscillation frequency of the test pulse generated by the test signal generation unit 2 and also controls the switching between the detection signal pulse and the test pulse input to the measurement unit 12.

  In the measurement unit 12, the pulse amplifier 121 receives and amplifies the detection signal pulse from the radiation detector 11, and the pulse height discriminator 122 is a digital pulse when the voltage of the amplified detection signal pulse is within a predetermined range. To eliminate noise.

The up / down counter 123 inputs the digital pulse output from the wave height discriminator 122 to the addition input unit 123a, and inputs a feedback pulse described later to the subtraction input unit 123b, and outputs an integrated value M obtained by integrating the difference between the two. To do. The frequency synthesis circuit 124 receives the integrated value M output from the up / down counter 123 and generates the feedback pulse.

  Further, the integration control circuit 125 performs weighting when the up / down counter 123 counts, and the calculator 126 as a calculation means calculates the count rate by inputting the integrated value M output from the up / down counter 123. At the same time, an alarm determination is made, and the counting rate and the alarm are displayed on the display 127.

  The first changeover switch 128 that is the first changeover means changes the input to the pulse amplifier 121, and the second changeover switch 129 that is the second changeover means is the subtraction input section 123 b of the up / down counter 123. Change the input to. Needless to say, the counting rate may be finally converted into an engineering value by the calculator 126 and output as a radiation dose.

  For each of the first changeover switch 128 and the second changeover switch 129 of the measurement unit 12, for example, a semiconductor switch having a high operation speed is used, and there are three positions of a measurement position, an input cutoff position, and a test input position. doing.

  In the normal mode, the control unit 3 sets the first changeover switch 128 to the measurement position and passes the detection signal pulse, and sets the second changeover switch 129 to the measurement position and passes the feedback pulse. In the test mode, an optimum test pulse frequency is determined based on the target count rate, the latest count rate, and the weighting constant when the up / down counter 123 counts. Then, the positions of the first changeover switch 128 and the second changeover switch 129 are determined, the oscillation frequency of the test pulse of the test signal generator 2 is controlled, and the first changeover switch 128 and the second changeover switch of the measurement unit 12 are controlled. The position of the changeover switch 129 is switched and a test pulse is input to the measurement unit 12.

  Note that the measurement unit 12 outputs a warning during testing to the display 127 and other equipment as necessary for the test period and the period until the count rate returns to the background level immediately before the test mode after the test is completed. To do.

  In the test mode, the control unit 3 uses the first changeover switch 128 as a test input position, the second changeover switch 129 as an input cutoff position, and the first changeover switch 128 as a test input position. B mode with the changeover switch 129 as the measurement position, C mode with the first changeover switch 128 as the input cutoff position and the second changeover switch 129 as the test input position, the first changeover switch 128 and the second changeover There are four switching control modes of D mode in which the switch 129 is an input cutoff position. The control unit 3 inputs the test pulse based on the optimum test pulse frequency and the optimum switching control mode obtained by calculation.

The radiation monitoring apparatus according to the first embodiment is configured as described above, and the operation thereof will be described next.
Since the radiation count rate varies statistically, in order to measure with a predetermined accuracy, the time constant τ is controlled based on the count rate n so that the standard deviation σ is constant as shown in the following equation.
σ = 1 / (2nτ) ^1/2 (1)
τ = 1 / (2nσ ² ) (2)

  In the normal mode, a digital pulse output by discriminating and removing noise from the detection signal pulse input by the wave height discriminator 122 is input to the addition input unit 123a of the up / down counter 123, and frequency synthesis is performed to the subtraction input unit 123b. In the circuit 124, a digital pulse obtained by frequency division and frequency synthesis from the clock pulse of the arithmetic unit 126 based on the integrated value M is input.

In an equilibrium state, the frequency F _{IN of the} digital pulse input to the addition input unit 123a of the up / down counter 123 is equal to the count rate n obtained by the calculator 126 and the frequency F _B (M) of the subtraction input unit 123b. Based on the standard deviation σ and the integrated value M, F _B (M) and n follow the first-order lag of the time constant τ so as to balance with _FIN as shown in the following equation. respond.
F _IN = F _B (M) = n = e ^γM = 2 ^{γM / ln2} (3)
γ = 2σ ² = 1 / (nτ) = 2 ^−λ · ln2 (4)
β = 11−λ (5)

In the above equation (4), when λ is 11, 9, 7, 5 for example, the standard deviation σ is 1.3%, 2.6%, 5.2%, 10.4%, respectively. When λ is based on the time of 11, when λ is 9,7,5, gamma, respectively ^{2 doubles, 2 4-fold, 2 6} fold becomes, ^{2 1} times the standard deviation σ, respectively, ^{2 doubles,} 2 ^tripled becomes, the (2), respectively ^{2 -2} times the time constant τ as ^{equation 2 -4 times,} a ^2-6 fold.

As shown in equation (3), the counting rate n is the 2 ^beta double the γ in a constant state, the integrated value M is equilibrated with ^2-beta times the response time. In counting rate n is a constant state, to ensure that the integrated value M apparent be changed γ does not change, up-down counter 123 After the γ to 2 ^beta times are weighting of one pulse 2 ^beta times You only have to count. That is, when a digital pulse output to the adding input portion 123a from the pulse height discriminator 122 of the up-down counter 123 is one input, the integrated value M is to be added counted by 2 ^beta. On the other hand, when the digital pulse outputted to the subtracting input portion 123b of the up-down counter 123 from the frequency synthesizer circuit 124 is one input, the integrated value M is to be subtracted counted by 2 ^beta. As a result the accumulated value M becomes an integrated value value multiplied by 2 ^beta to the N of the difference subtraction counting and addition count.

Here, β is 0 or a positive integer. When λ is 11, 9, 7, 5 as shown in the above formula (5), 0, 2, 4, 6 are given as β, respectively. For example, when λ is 11, M is added to or subtracted from one pulse input, and M and N are equal. When λ is 9, four pulses are added to or subtracted from one pulse input. That is, when σ is 1.3%, 2.6%, 5.2%, and 10.4%, the up / down counter 123 is weighted by 1, 4, 16, and 64 per pulse by the integration control circuit 125, respectively. And count. Thus, the (3) 2 ^beta multiplying that the γ In the equation is equivalent to changing the weighting count to 2 ^beta times, counting rate n is 2 ^beta doubles weighted the result of apparent integration value Based on M and γ corresponding to the reference β = 0 (λ = 11), it is obtained by the equation (3). As described above, the integration control circuit 125 controls the weighting of the count of the up / down counter 123, so that the apparent integration value M is used as it is even if the setting of γ is changed in a state where the count rate n is constant. As a result, a sudden change in the counting rate n due to the setting change does not occur.

The target count rate of the test is n (target), the integrated value corresponding to n (target) is M (target), the count rate in the current calculation cycle is n (current), and the integrated value corresponding to n (current) is M ( This time), the frequency of the test pulse is m (test), the calculation cycle of the calculator 126 of the measurement unit 12 is ΔT1, the control cycle of the control unit 3 is ΔT2, and the weight when the up / down counter 123 counts is α = and 2 ^beta, control unit 3, the control cycle △ T2 n (current) for each, M (current), high warning setpoint, low alarm setpoint, gamma, receiving the necessary data α and the like from the measuring unit 12. j is an integer of 2 to 5, and k is an integer of (ΔT1 + ΔT2) / ΔT2-2 under the condition of ΔT1 <ΔT2, and control in the case of the input / output response test based on FIG. The operation of unit 3 will be described.

First, the test input position of the measurement unit 12 is set to the D mode (step S101), and then n (target) is read from a memory (not shown) of the control unit 3 (step S102). Thereafter, M (target) = (1 / γ) · ln {n (target)} is obtained based on n (target) (step S103).

Next, M (current) is read from the memory of the control unit 3 (step S104), and {M (target) −M (current)} ≧ jα is determined (step S105). The frequency m (test) is controlled to m (test) = {M (target) -M (current) -jα} ÷ k · ΔT2 (step S106), and the test input position of the measurement unit 12 is set to the A mode (step S106). S107), the process returns to step S104.

If NO in step S105, a determination of {M (current) −M (target)} ≧ jα is performed (step S108). If the determination result in step S108 is YES, the frequency m (test) of the test pulse is determined. Is controlled to m (test) = {M (current) -M (target) + jα} ÷ k · ΔT2 (step S109), the test input position of the measurement unit is set to the C mode (step S110), and the process returns to step S104. .

  If the determination result in step S108 is NO, the test pulse frequency m (test) is controlled to m (test) = n (target) (step S111), and the test input position of the measurement unit 12 is set to the B mode. (Step S112). Then, it is determined whether or not a predetermined number of fixed periods has elapsed in the B mode (step S113). If the determination result in step S113 is NO, the process returns to step S111. If the determination result in step S113 is YES, the final m (test) and n (current) data are stored in the memory of the control unit 3 (step S114), and the input / output response test is terminated.

FIG. 3A shows a test in an input / output response test in which, for example, k · ΔT2 is about 1 second and n (current) = 10 cpm is increased from n (target) = 10 ⁴ cpm to measure an instruction error. This shows the change of the pulse frequency m (test) and the response of the count rate n (current). The test position is set to the A mode, and the count rate n (current) is set to, for example, a target 1 for each period of k · ΔT2. When the count rate n (current) is close to the resolution range with respect to n (target), the test position is set to the B mode, and the test pulse frequency m (test) is set to m (test) = n ( Control).

  FIG. 3B shows, for example, a change in the frequency m (test) of the test pulse and the count rate in an input / output response test in which the indication error is measured by dropping from n (current) = 100 cpm to n (target) = 10 cpm. n (current) response, the test position is set to the C mode, and the count rate n (current) is made to approach, for example, about 1/2 of the target for each period of k · ΔT2, and the count rate n (current) is When close to the resolution range with respect to n (target), the test position is set to the B mode, and the test pulse frequency m (test) is controlled to m (test) = n (target).

  As described above, according to the radiation monitoring apparatus according to the first embodiment, the control unit 3 inputs the test pulse to either the addition input or the subtraction input from the current value of the integrated value M of the up / down counter 123 and the target value. Therefore, the test pulse input of the measuring unit 12 is switched and controlled, so that the target value can be accurately reached in a short time. Further, since the frequency of the test pulse is automatically and sequentially optimized, it is possible to provide a radiation monitoring apparatus that can greatly reduce the test time and can change the test items as needed. The test input method of the radiation monitoring apparatus according to the first embodiment can obtain the same effect even when applied to an alarm test with the alarm set value as m (target).

Embodiment 2. FIG.
Next, a radiation monitoring apparatus according to Embodiment 2 of the present invention will be described. Since the radiation monitoring apparatus according to the second embodiment has the same configuration as that of the first embodiment, the description thereof will be omitted and the operation will be described next.

  FIG. 4 is a flowchart for explaining the operation of the control unit of the radiation monitoring apparatus according to the second embodiment. The control unit 3 of the radiation monitoring apparatus according to the second embodiment uses the frequency m (test) of the A-mode test pulse in the high alarm test for confirming the high alarm operation set to a level higher than the background count rate. The operation of the control unit 3 will be described with reference to FIG. In the high alarm test, the alarm set value is n (target). Since the precondition for starting the high alarm test is M (target)> M (current), if this condition is not satisfied, the condition is prepared by the input / output response test in FIG. 3 described in the first embodiment. And

As shown in FIG. 4, first, the test input position of the measurement unit 12 is set to the D mode (step S201), and then n (target) is read from a memory (not shown) of the control unit 3 (step S202). Thereafter, M (target) = (1 / γ) · ln {n (target)} is obtained based on n (target) (step S203).

Next, M (current) is read from the memory of the control unit 3 (step S204), and {M (target) -M (current)} ≧ jα is determined (step S205). Frequency m (test) is m (test) = {M (target)-M (current)-jα} ÷ k · △
Control is performed at T2 (step S206), the test input position of the measurement unit 12 is set to the A mode (step S207), and the process returns to step S204.

If NO in step S205, it is determined that there is a high alarm transmission (step S208). If the determination result in step S208 is NO, the test pulse frequency m (test) is set to m (test) = exp [γ { M (current) + α}] (step S209), the test input position of the measurement unit 12 is set to the A mode (step S210), and the process returns to step S204.

  If the determination result in step S208 is YES, m (test) is held (step S211), m (test) at the time of high alarm transmission, and n (current) are stored in the memory (step S212). End the test. The hold of m (test) at the time of alarm transmission is canceled by resetting by the control unit 3.

  As described above, according to the radiation monitoring apparatus according to the second embodiment, the control unit 3 controls the frequency m (test) of the A-mode test pulse by automatically and sequentially optimizing and controlling in the high alarm test. As a result, the high alarm test can be performed efficiently in a short time and the high alarm operating point can be confirmed with high accuracy. In addition, since the frequency of the test pulse is held when the high alarm is issued, an inadvertent overrun of the up / down counter 123 is suppressed, and an effect of efficiently shifting to the next test is achieved.

Embodiment 3 FIG.
Next, a radiation monitoring apparatus according to Embodiment 3 of the present invention will be described. Since the radiation monitoring apparatus according to the third embodiment has the same configuration as that of the first embodiment, the description thereof will be omitted and the operation will be described next.

FIG. 5 is a flowchart for explaining the operation of the control unit of the radiation monitoring apparatus according to the third embodiment. The control unit 3 of the radiation monitoring apparatus according to the third embodiment sets the frequency m (test) of the C-mode test pulse in the grain pattern in the alarm test for confirming the low alarm operation set to a level lower than the background count rate. The operation of the control unit 3 will be described with reference to FIG. In the low alarm test, the alarm set value is n (target). Since the precondition for starting the low alarm test is M (current)> M (target), if this condition is not satisfied, the condition is prepared by the input / output response test in FIG. 3 described in the first embodiment. And

As shown in FIG. 5, first, the test input position of the measurement unit 12 is set to the D mode (step S301), and then n (target) is read from a memory (not shown) of the control unit 3 (step S302). Thereafter, M (target) = (1 / γ) · ln {n (target)} is obtained based on n (target) (step S303).

Next, M (current) is read from the memory of the control unit 3 (step S304), {M (current) -M (target)} ≧ jα is determined (S305), and if YES, the frequency of the test pulse m (test) is controlled to m (test) = {M (current) −M (target) + jα} ÷ k · ΔT2 (step S306), and the test input position of the measurement unit 12 is set to the C mode (step S307). Return to step S304.

  If NO in step S305, it is determined that there is a low alarm transmission (step S308), and if the determination result in step S308 is NO, the frequency m (test) of the test pulse is m (test) = exp [γ { M (current) −α}] (step S309), the test input position of the measurement unit 12 is set to the C mode (step S310), and the process returns to step S304.

If the determination result in step S308 is YES, m (current) is held (step S311), m (test) at the time of low alarm transmission, and n (current) are stored in the memory (step S312). End the test. The hold of m (test) at the time of alarm transmission is canceled by resetting by the control unit 3.

  As described above, according to the radiation monitoring apparatus according to the third embodiment, the control unit 3 controls the frequency m (test) of the C-mode test pulse in a low alarm test by finely and automatically optimizing and controlling the frequency m. Therefore, the low alarm test can be performed efficiently in a short time and the low alarm operating point can be confirmed with high accuracy. In addition, since the frequency of the test pulse is held when a low alarm is issued, an inadvertent overrun of the up / down counter 123 is suppressed, and an effect of efficiently shifting to the next test is achieved.

Embodiment 4 FIG.
Next, a radiation monitoring apparatus according to Embodiment 4 of the present invention will be described. Since the radiation monitoring apparatus according to the fourth embodiment has the same configuration as that of the first embodiment, the description thereof will be omitted and the operation will be described next.

  FIG. 6 is a flowchart for explaining the operation of the measurement unit of the radiation monitoring apparatus according to the fourth embodiment. As shown in FIG. 6, the radiation monitoring apparatus according to the fourth embodiment holds the alarm transmission count rate and checks the operating point when the measurement unit 12 issues an alarm in the alarm determination calculation of the alarm test. The operation of the measurement unit 12 will be described with reference to FIG.

  As shown in FIG. 6, first, M (current) is read from a memory (not shown) (step S401), and n (current) = exp {γM (current)} is obtained (step S402).

  Thereafter, n (current) ≧ n (high alarm set value) is determined (step S403). If NO, n (current) ≦ n (low alarm set value) is determined (step S404). If the determination result is NO, n (current) is output (step S405), and the process returns to step S401.

If the determination result in step S403 is YES, a high alarm is issued and the count rate n (
High alarm transmission) is held (step S406), n (current) at the time of high alarm transmission is output and stored in the memory (step S407), and the alarm test is terminated.

  If the determination result in step S404 is YES, a low alarm is issued and the count rate n (low alarm transmission) is held (step S408), and the low alarm and the held count rate are output and stored in the memory. Store (step S409) and end the alarm test. Note that the high alarm and the low alarm are canceled by resetting the measurement unit 12.

  As described above, according to the radiation monitoring apparatus according to the fourth embodiment, in the alarm determination calculation of the alarm test, the measurement unit 12 holds the count rate when the alarm is transmitted. In addition, it is possible to suppress the inadvertent overrun of the up / down counter 123 and efficiently shift to the next test.

Embodiment 5 FIG.
Next, a radiation monitoring apparatus according to Embodiment 5 of the present invention will be described. Since the radiation monitoring apparatus according to the fifth embodiment has the same configuration as that of the first embodiment, the description thereof will be omitted and the operation will be described next.

  FIG. 7 is a flowchart for explaining the operation of the control unit of the radiation monitoring apparatus according to the fifth embodiment. When returning from the test mode to the normal mode, the radiation monitoring apparatus according to the fifth embodiment uses the test pulse to promote the return of the count rate to the vicinity of the background count rate n (BG) immediately before the test. The operation of the control unit 3 will be described with reference to FIG.

  After switching the measurement unit 12 from the test mode to the normal mode (step S501), the control unit 3 sets the test input position of the measurement unit 12 to the D mode (step S502), and stores n (BG) from a memory (not shown). Read (step S503).

Next, M (BG) = (1 / γ) · ln {n (BG)} is obtained based on n (BG) (step S504), and M (current) is read from the memory of the control unit 3 (step S505). , {
It is determined that M (BG) −M (current)} ≧ jα (step S506).

  If YES in step S506, the frequency m (test) of the test pulse is controlled to m (test) = {M (BG) -M (current) -jα} ÷ k · ΔT2 (step S507), and the measurement unit The 12 test input positions are set to the A mode (step S508), and the process returns to step S505.

  If NO in step S506, a determination of {M (current) −M (BG)} ≧ jα is performed (step S509). If the determination result in step S509 is YES, the frequency m (test) of the test pulse Is controlled to m (test) = {M (current) −M (BG) + jα} ÷ k · ΔT2 (step S501), the test input position of the measurement unit 12 is set to the C mode (step S511), and the process proceeds to step S505. Return.

  If the determination result in step S509 is NO, the first changeover switch 127 and the second changeover switch 128 are returned to the measurement position (step S512), and the measurement unit 12 is notified of the return to the normal mode (step S513). When the control unit 3 switches the measurement unit 12 from the normal mode to the test mode, the control unit 3 stores the background count rate in the previous normal mode as n (BG) in the memory. In addition, the display 129 displays a status so that it can be determined whether the measurement unit 12 is in the normal mode or the test mode, and outputs a warning during the test during the test.

  As described above, according to the radiation monitoring apparatus according to the fifth embodiment, the control unit 3 inputs a test pulse from M (current) and M (BG) of the up / down counter 123 to either the addition input or the subtraction input. Since the input of the test pulse of the measuring unit 12 is switched and determined by determining whether to do so, the background count rate immediately before the test mode can be accurately reached in a short time.

Embodiment 6 FIG.
Next, a radiation monitoring apparatus according to Embodiment 6 of the present invention will be described. As shown in FIG. 8, the radiation monitoring apparatus according to the sixth embodiment is provided with a waveform shaping circuit 130 that approximates the waveform of the test pulse to the detector signal pulse before the first changeover switch 128. Is configured. In addition, about another structure, it is the same as that of Embodiment 1, or is equivalent, and abbreviate | omits description by attaching | subjecting the same code | symbol.

  According to this configuration, there is an effect that the soundness including the frequency characteristics of the pulse amplifier 121 can be confirmed.

Embodiment 7 FIG.
Next, a radiation monitoring apparatus according to Embodiment 7 of the present invention will be described. As shown in FIG. 9, the radiation monitoring apparatus according to the seventh embodiment replaces the pulse height discriminator 122 constituting the measurement unit 12 of the radiation monitoring apparatus described in the first to fifth embodiments with the detector signal pulse. A waveform discriminator 131 that outputs a digital pulse when the waveform is discriminated and a predetermined condition is satisfied is provided. In addition, about another structure, it is the same as that of Embodiment 1, or is equivalent, and abbreviate | omits description by attaching | subjecting the same code | symbol.

  According to this configuration, regardless of the normal mode and the test mode, even if noise occurs due to switching between the normal mode and the normal mode, noise pulses can be removed and measured, so a highly reliable radiation monitoring device Can provide.

Embodiment 8 FIG.
Next, a radiation monitoring apparatus according to Embodiment 8 of the present invention will be described. As shown in FIG. 10, the radiation monitoring apparatus according to the eighth embodiment includes radiation monitors 1a, 1b,..., 1n and a plurality of channels. I did it. The radiation monitors 1a, 1b,..., 1n, the control unit 3, and the test signal generation unit 2 are the same as those described in the first to seventh embodiments, and detailed description thereof is omitted.

  According to this configuration, by sharing the control unit 3 and the test signal generation unit 2, there is an effect that the cost can be significantly reduced.

1, 1a, 1b, 1n Radiation monitor 2 Test signal generation unit 3 Control unit 11 Radiation detector 12 Measurement unit 121 Pulse amplifier 122 Wave height discriminator 123 Up / down counter 123a Addition input unit 123b Subtraction input unit 124 Frequency synthesis circuit 125 Integration control Circuit 126 Calculator 127 Display 128 First changeover switch 129 Second changeover switch 130 Waveform shaping circuit 131 Waveform discriminator

Claims (9)

A radiation detector that detects radiation and outputs a detection signal pulse; a measurement unit that inputs the detection signal pulse and measures a count rate; a test signal generation unit that generates a test pulse; and the test signal generation unit A radiation monitoring apparatus comprising: a control unit that controls the transmission frequency of the output test pulse and that controls the input of the measurement unit;
The measurement part
A pulse amplifier for inputting and amplifying the detection signal pulse;
A pulse height discriminator that outputs a digital pulse when the voltage of the amplified detection signal pulse is within a predetermined range;
An up / down counter which has an addition input unit and a subtraction input unit, inputs the digital pulse to the addition input unit, inputs a feedback pulse to the subtraction input unit, and outputs an integrated value obtained by integrating the difference between the two; ,
A frequency synthesizer that inputs the integrated value and generates the feedback pulse;
An integration control circuit for weighting when the up / down counter counts;
A calculating means for inputting the integrated value and obtaining the counting rate;
First switching means for switching the input of the pulse amplifier;
Second switching means for switching the subtraction input of the up / down counter ,
Each of the first switching means and the second switching means has three positions: a measurement position that enables input measurement, an input cutoff position that blocks input, and a test input position that enables measurement of the test pulse. Have
The control unit
In the normal mode, the first switching means is set to the measurement position to pass the detection signal pulse, and the second switching means is set to the measurement position to pass a feedback pulse.
In the test mode, the frequency of the test pulse is determined based on the target count rate, the latest count rate, and the weighting constant when the up / down counter counts, and the positions of the first switching means and the second switching means are determined. To control the test pulse generation frequency of the test signal generator and switch the positions of the first switching means and the second switching means to input the test pulse to the measuring section. In the radiation monitoring equipment
In the test mode, the control unit is an A mode in which the first switching means is the test input position and the second switching means is the input cutoff position, and the first switching means is the test input position. A C mode in which the second switching means is the measurement position, the first switching means is the input cutoff position, and the second switching means is the test input position. Four switching control modes of D mode in which the switching means and the second switching means are the input cutoff position,
A radiation monitoring apparatus, wherein the test pulse is input based on the frequency of the test pulse obtained by calculation and the switching control mode . The control unit sets the target count rate to n (target), the integrated value corresponding to n (target) to M (target), the count rate in the current calculation cycle to n (current), and the integrated value corresponding to n (current). Is M (current), the frequency of the test pulse is m (test), the calculation period of the measurement unit is ΔT1, the control period of the control unit is ΔT2, and the weight when the up / down counter counts is α ,
Under the condition of ΔT1 <ΔT2, M (target) = (1 / γ) · ln {n (target)} is obtained based on n (target), and {M (target) −M (current time) in the D mode. )}> Jα (j is an integer of 2 to 5) and {M (current) −M (target)}> jα
During the period when the condition {M (target) -M (current)}> jα is satisfied, the test pulse generation frequency of the test signal generator is set to m (test) = {M (target) -M (current) -jα. } ÷ k · ΔT2 (k is an integer of (ΔT1 + ΔT2) / ΔT2-2), and a test pulse is input to the measurement unit in the A mode.
During the period when the condition of {M (current) -M (target)}> jα is satisfied, the transmission frequency of the test pulse of the test signal generator is set to m (test) = {M (current) -M (target) + jα} ÷ k / ΔT2 is controlled and a test pulse is input to the measurement unit in the C mode.
In other cases, the test pulse generation frequency of the test signal generator is controlled to m (test) = n (target) and the test pulse is input to the measuring unit in the B mode for a predetermined period . The radiation monitoring apparatus according to claim 1. When the control unit starts from a state of M (target)> M (current) in an alarm test for confirming a high alarm operation set to a level higher than the background count rate, {M (target) −M During the period when the condition of (current)}> jα is satisfied, the test pulse generation frequency of the test signal generator is controlled to m (test) = {M (target) −M (current) −jα} ÷ k · ΔT2. In addition, a test pulse is input to the measurement unit in the A mode,
If the above condition is not satisfied, the test pulse generation frequency of the test signal generator is controlled to m (test) = exp [γ {M (current) + α}] and the measurement unit is tested in the A mode. Input pulse,
The radiation monitoring apparatus according to claim 2, wherein the frequency of the test pulse is held when an alarm is generated . When the control unit starts from a state of M (target) <M (current) in an alarm test for confirming a low alarm operation set to a level lower than the background count rate, {M (current) -M During the period when the condition of (target)}> jα is satisfied, the test pulse generation frequency of the test signal generator is controlled to m (test) = {M (current) −M (target) + jα} ÷ k · ΔT2. In addition, a test pulse is input to the measurement unit in the C mode,
If the above condition is not satisfied, the test pulse generation frequency of the test signal generator is controlled to m (test) = exp [γ {M (current) −α}], and the measurement unit is operated in the C mode. Input a test pulse,
The radiation monitoring apparatus according to claim 3, wherein the frequency of the test pulse is held when an alarm is generated . 5. The radiation monitoring apparatus according to claim 3, wherein, in the alarm test, the measurement unit holds the count rate when an alarm is transmitted . The measurement unit stores the background count rate n (BG) in the normal mode immediately before the start of the test mode, and when the measurement unit is switched from the test mode to the normal mode, M is determined based on n (BG). (BG) = (1 / γ) · ln {n (BG)} and {M (BG) −M (current)}> jα (j is an integer of 2 to 5) and {M ( This time) -M (BG)}> jα,
During the period when the condition of {M (BG) −M (current)}> jα is satisfied, the test pulse generation frequency of the test signal generator is m (test) = {M (BG) −M (current) −jα } ÷ k · ΔT2 (k is an integer of (ΔT1 + ΔT2) / ΔT2-2) and a test pulse is input to the measurement unit in the A mode,
During the period when the condition of {M (current) -M (BG)}> jα is satisfied, the test pulse generation frequency of the test signal generator is set to m (test) = {M (current) −M (BG) + jα}. ÷ k / ΔT2 is controlled and a test pulse is input to the measurement unit in the C mode.
In other cases, the first switching means and the second switching means are returned to the measurement position and the measurement unit is notified of the return to the normal mode, and the measurement unit ends the test mode period and the test mode. the count rate for the period until returning to background levels in normal mode immediately before the test mode, characterized in that the during the test for informing that it is being tested is cautioned to outgoing automatic Te claim 1 The radiation monitoring apparatus as described in any one of -5 . 7. The measurement unit according to claim 1, further comprising a waveform shaping circuit that approximates the waveform of the test pulse to the detection signal pulse before the first switching unit. The radiation monitoring apparatus described. The measurement unit of claim 1 to 7, characterized in that with a waveform discriminator that outputs a digital pulse when a predetermined condition is satisfied by discriminating the waveform of the detection signal pulse instead of the pulse height discriminator The radiation monitoring apparatus according to any one of the above. The radiation monitoring apparatus according to any one of claims 1 to 8, wherein a radiation monitor is provided with a plurality of channels, and the control unit and the test signal generation unit simultaneously test the plurality of channels. .

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