JPH04258782A - Radioactive ray monitor - Google Patents

Abstract

PURPOSE:To easily pursue the cause of the aging change of the exposure rate as the detection result of radioactive rays in a wide-range radioactive ray monitor using an ionization chamber. CONSTITUTION:A radioactive ray detection section 40 detecting radioactive rays 2 with an ionization box and outputting the primary voltage V1 indicating the logarithm of the exposure rate of the radioactive rays 2, a primary delay circuit 7 smoothing the primary voltage V1 to obtain the secondary voltage V2, and a means outputting the tertiary voltage V3 indicating the dose of pulse- shaped radioactive rays when the radioactive ray detection section 40 detects the pulse-shaped radioactive rays are provided, and the radioactive rays 2 are monitored based on the secondary voltage V2 and the tertiary voltage V3.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to the irradiation dose rate (
Hereinafter, the irradiation dose rate may be simply referred to as the dose rate. ), and in particular, relates to a device that can easily investigate the cause of changes in dose rate over time.

0002

2. Description of the Related Art FIG. 4 is a block diagram of a conventional radiation monitor. In the figure, 1 is an ionization chamber into which an ionizing current i representing the dose rate r of the radiation 2 flows when the radiation 2 is incident, 3 is an operational amplifier 4 and a diode 5 as a negative feedback circuit for this amplifier 4, and a current i The primary voltage V1 representing the logarithm of
6 is the resistor R1 and capacitor C1
7 is an operational amplifier 8 whose non-inverting input terminal is grounded, an input resistor R2 connected to the inverting input terminal of the amplifier 8, and the above-mentioned parallel circuit forming a negative feedback circuit of the amplifier 8. This is a first-order delay circuit consisting of 6. Then, 9 is the secondary voltage V as the output voltage of the delay circuit 7.
2 is an analog recorder for recording, 10 is a radiation monitor consisting of the above-mentioned parts, and 40 is a radiation detection section consisting of an ionization chamber 1 and a logarithmic amplifier 3. In the monitor 10, C1 and R1 are set so that the time constant T1=C1×R1 of the circuit 7 becomes a considerably long time, and in this case, R1
=R2.

[0003] In the monitor 10, as mentioned above,
After the radiation 2 is detected by the ionization chamber 1, a voltage V1 proportional to logi is obtained, so it is clear that the dose rate r can be measured over a wide range of orders of magnitude from small to large dose rates using this V1. And also,
In the case of the monitor 10, since the circuit 7 is configured as described above, in a steady state where V1 does not change, V1=V2, and furthermore, the current i due to the statistical fluctuation originally exhibited by the dose rate of background radiation. It is clear that the fluctuations in V1 due to fluctuations are sufficiently smoothed out by the filtering action of the circuit 7 with the long time constant T1, even in the case of large fluctuations. Therefore, according to the monitor 10,
By using the voltage V2, the dose rate γ can be stably measured or monitored over a wide range of orders of magnitude without being affected by the above-mentioned statistical fluctuations.

0004

[Problem to be Solved by the Invention] In the monitor 10, when this monitor 10 is used for monitoring radioactive materials released into the environment of a facility handling radioactive materials, the dose rate r increases due to the release of the radioactive materials. The above-mentioned first-order delay circuit 7 is provided in order to be able to clearly distinguish the background dose rate from fluctuations in the background dose rate based on background radiation. If the particle acceleration operation performed by this accelerator causes radiation whose dose rate changes over time in a pulse-like manner to appear in the environment (hereinafter, this radiation may be referred to as pulse-like radiation), this pulse Fluctuations in the voltage V1 due to the shape radiation are also smoothed by the action of the circuit 7, similar to the fluctuations in V1 due to the statistical fluctuations of the background dose rate.
Therefore, in the case of the monitor 10, it is clear that when the voltage V2 increases, it is not possible to distinguish from the recording result of the recorder 9 whether the cause is the release of radioactive substances or the appearance of pulsed radiation. That is, the above-described monitor 10 has a problem in that, because the dose rate γ is monitored using the voltage V2 smoothed by the circuit 7, it is difficult to investigate the cause of the change in γ over time.

An object of the present invention is to make it possible to measure the dose of pulsed radiation in addition to obtaining the voltage V2 described above, so that it is possible to easily investigate the cause of the change over time in the dose rate γ of the radiation 2.

[0006]

[Means for Solving the Problems] In order to achieve the above object, according to the present invention,

1) a radiation detection unit that detects radiation and outputs a primary voltage representing the logarithm of the irradiation dose rate of the radiation;
a primary delay circuit that smoothes the primary voltage with a long time constant and outputs a secondary voltage; and a predetermined constant current is added to the primary current proportional to the primary voltage and the secondary current proportional to the secondary voltage. a control unit that outputs a control signal when the difference from the sum current changes from negative polarity to positive polarity, and extinguishes the control signal after a predetermined delay time when the difference changes from the positive polarity to the negative polarity; , when the control signal is input, a voltage difference between a voltage according to the inverse logarithmic value of the primary voltage and a voltage according to the inverse logarithmic value of the secondary voltage is integrated while the control signal is input. a calculation unit that outputs a tertiary voltage representing the integrated value, and the radiation monitor is configured to monitor the radiation using the secondary and tertiary voltages, and

2) In the monitor described in item 1) above,
an analog recorder that records secondary and tertiary voltages and a synchronization signal as a pulse train signal consisting of pulses representing particle acceleration operations of the particle accelerator; and each time the pulse appears in the synchronization signal, the value of the third voltage at that time. A radiation monitor is configured by adding a digital recorder that integrates and records the value of the third voltage on the previous recorded value and also records the number of times the value of the third voltage is integrated.

3) In the monitor described in either 1) or 2) above, the first-order lag circuit is connected to an operational amplifier whose non-inverting input terminal is grounded, and an input connected to the inverting input terminal of the operational amplifier. A radiation monitor is configured to include a resistor and a CR parallel circuit forming a negative feedback circuit for the operational amplifier.

0010

[Operation] With the above configuration, in any monitor, when pulsed radiation appears in the radiation field where the radiation detection unit detects radiation, the inverse logarithm conversion voltage of the primary voltage and the inverse logarithm conversion voltage of the secondary voltage The voltage difference between the two and By setting the time appropriately, the time during which the difference between the primary current and the sum current maintains a positive polarity can be made to approximately match the duration of fluctuations in the radiation dose rate due to the pulsed radiation. Every time pulsed radiation appears, the calculation unit outputs a tertiary voltage representing the dose of this pulsed radiation, and it is clear that the secondary voltage outputted by the first-order delay circuit is equal to the voltage V2 mentioned above. Therefore, by monitoring radiation using the secondary voltage and the tertiary voltage, it is possible to easily investigate the cause of the change over time in the radiation dose rate r.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an embodiment of the present invention. In this figure, the same parts as in FIG. 4 are given the same reference numerals as in FIG. Now, in FIG. 1, R3 is the non-inverting input terminal 1 of the operational amplifier 11 whose inverting input terminal is grounded.
1a and the output terminal of the operational amplifier 4; R4 is a resistor connected between the output terminal of the operational amplifier 8 and the terminal 11a; the resistance value is equal to that of R3; and R5 is a constant voltage direct current with negative polarity. A resistor 12 is connected between the power supply E and the terminal 11a, and 12 is input with the output voltage V4 of the operational amplifier 11, and V4 is a negative polarity voltage -V40 to a positive polarity voltage V4.
This control signal generator outputs a control signal 12a when V4 changes from V40 to -V40 and causes the signal 12a to disappear after a predetermined delay time τ has elapsed. In this case, the amplifier 11 sets the value of the voltage V4 to -V40 when the current flowing into the terminal 11a has a negative polarity, and sets the value of V4 to V40 when the current flowing into the terminal 11a has a positive polarity. It is composed of 13 is resistance R3
, R4, R5, a power supply E, an amplifier 11, and a signal generator 12.

In FIG. 1, the logarithmic amplifier 3, the first-order lag circuit 7, and the control section 13 are constructed as shown, so that in this case, V1 is at a positive potential, V2 is at a negative potential, and the terminal 1
1a becomes almost zero potential, current I1=V1/R3 flows in the direction shown in the resistor R3, current I2=V2/R4 flows in the direction shown in the resistor R4, and almost constant in the direction shown in the resistor R5. A current I3=E/R5 flows. Therefore, the control unit 13 controls the primary current I1 proportional to the primary voltage V1.
When the difference between the current and the sum of the secondary current I2 proportional to the secondary voltage V2 and the predetermined constant current I3 changes from negative polarity to positive polarity, the control signal 12a is output, and the difference changes from positive polarity to negative polarity. When the signal changes to 12 after a predetermined delay time τ has passed,
It can be said that a disappears. Then, in this case, since R3=R4, V1=
When V2 is established, I1=I2.

In FIG. 1, 14 is an anti-logarithmic converter which receives a voltage V1 and performs an anti-logarithmic transformation on V1 in parentheses and outputs a voltage V5 representing the anti-logarithmic value exp(V1) of V1, and 15 is a voltage An anti-logarithmic converter receives V2 and performs anti-logarithmic transformation on V2 in parentheses and outputs a voltage V6 representing the anti-logarithmic value exp (V2) of V2; 16 is a control signal 12;
This is a b contact that opens the circuit when a is input and closes the circuit when the signal 12a disappears. 17 is a series circuit 18 consisting of a b contact 16 and a resistor R6, and this circuit 18 is connected in parallel. This is an integrating circuit consisting of a connected capacitor C2, and an operational amplifier 19 whose parallel circuit consisting of C2 and a series circuit 18 is connected to a negative feedback circuit and whose non-inverting input terminal is grounded. Then, 20 is the control signal 12
When the signal 12a is input, the circuit is closed and the voltages V5 and V6 are input to the integrating circuit 17 through the resistors R7 and R8, respectively. When the signal 12a disappears, the circuit is opened and the voltages V5 and V6 are input to the integrating circuit 17 through the resistors R7 and R8.
The a contact is designed to cut off the input to the circuit 17 of 6,
Reference numeral 21 denotes a radiation monitor consisting of the various parts shown in the figure.

In the monitor 21, R7=R8, and as mentioned above, V1 has positive polarity and V2 has negative polarity, so when the control signal 12a is input, the contact 20 is closed. Then (V5/R7-V6/
A current of R8)=(V5-V6)/R7=I4 will flow into the integrating circuit 17, and at this time, the contact 16 will be connected to the signal 12.
Since the signal generator 12 outputs the signal 12a in the monitor 21, the voltage (V5-
V6) is integrated by the circuit 17, and the voltage V3 representing this integrated value is outputted from the circuit 17 as a tertiary voltage. Therefore, in the monitor 21, when the signal 12a is input, the converters 14 and 15, the resistors R7 and R8, the contact 20, and the integrating circuit 17 convert the voltage V5 and the secondary voltage V2 according to the inverse logarithm value of the primary voltage V1. The arithmetic unit 22 is configured to integrate the voltage difference (V5-V6) between the voltage V6 and the voltage V6 corresponding to the antilogarithmic value of the voltage V6 while the signal 12a is input, and output the tertiary voltage V3 representing this integrated value. be able to.

In FIG. 1, each part is constructed as described above, so that when the above-mentioned pulsed radiation appears in the radiation field where the ionization chamber 1 detects radiation, the current I1 undergoes a pulsed time-dependent change based on this pulsed radiation. The portion 23 appears and the currents I1, I2 and (I2+I3) change over time as shown in FIG. 2, for example, and as a result, the time t1 shown in FIG.
The control signal 12 is output from the signal generator 12 from time to time t2.
a is output. Furthermore, since each part in FIG. 1 is configured as described above, when pulsed radiation appears in the radiation field, the difference voltage (V5-V6) represents the instantaneous dose rate of the pulsed radiation. Therefore, it is clear that (V5-V6) changes over time in a pulse-like manner, and furthermore, the duration of the pulse-like change in (V5-V6) in this case is determined by setting the current I3 to a small value. It is also clear that the time will be close to the time T0 shown in FIG. 2 for the case. Therefore, when the signal 12a is output from the signal generator 12 on the monitor 21 with I3 set to a small value, at the time when this signal 12a disappears, the voltage V3 represents the dose of one pulsed radiation. Further, when the signal 12a disappears, the input to the circuit 17 (V5-V6) is cut off by the contact 20, and the capacitor C2
is discharged through the resistor R6 and the contact 16, so that in such a monitor 21, V3 will indicate the dose of this radiation each time pulsed radiation appears in the radiation field, and eventually, By monitoring the radiation 2 using the voltages V2 and V3, the cause of the change over time in the dose rate r of the radiation 2 can be easily investigated.

The reason why the current I3 is set in FIG. 1 is because V2 is the output voltage of the first-order lag circuit 7, so the ionization chamber 1 detects radiation in a normal radiation field in which there is no pulsed radiation. This is because the polarity of the case (I1-I2) is generally undefined, so if I3 is not set, the voltage V4 will fluctuate unstablely. The reason why the signal 12a is made to disappear after the delay time τ shown in FIG. 2 has elapsed is to facilitate signal processing for the voltage V3, which is performed by AD converting the voltage V3.

FIG. 3 is a configuration diagram of a radiation monitor 24 as an embodiment of the present invention, which is different from the monitor 21. The difference from FIG. 1 is that the secondary and tertiary voltages V2 and V3 and particles (not shown) An analog recorder 27 is provided to record a synchronization signal 26 as a pulse train signal consisting of pulses 25 representing the particle acceleration operation of the accelerator, and the voltage V3 and the signal 26 are input and the pulse 25 is included in the signal 26. A gate 28 that passes the voltage V3 when it appears, an AD converter 29 that AD converts the voltage V3 that has passed through the gate 28, and a record that has already recorded the value of the voltage V3 as digital data 29a output by the converter 29. A digital recorder 31 is provided which includes a recording body 30 that integrates and records the value and also records the number of times the data 29a has been integrated. Since the monitor 24 is configured as described above, it is possible to investigate the causes of changes in the dose rate γ over time using the recording results of the recorders 27 and 31 even more easily than on the monitor 21. That is clear.

[0018]

[Effects of the Invention] As mentioned above, in the present invention,

[
1) A radiation detection section that detects radiation and outputs a primary voltage representing the logarithm of the irradiation dose rate of this radiation, and a primary lag circuit that smoothes the primary voltage with a long time constant and outputs a secondary voltage. , when the difference between the primary current proportional to the primary voltage and the sum current obtained by adding a predetermined constant current to the secondary current proportional to the secondary voltage changes from negative polarity to positive polarity, a control signal is output, and the difference is positive polarity. A control section that eliminates the control signal after a predetermined delay time when the polarity changes from positive to negative, and when the control signal is input, the voltage corresponds to the inverse logarithm value of the primary voltage and the inverse logarithm value of the secondary voltage. The radiation monitor is equipped with an arithmetic unit that integrates the voltage difference between the corresponding voltage and the corresponding voltage while a control signal is input, and outputs a tertiary voltage representing this integrated value. and also

2) In the monitor described in item 1) above,
An analog recorder records secondary and tertiary voltages and a synchronization signal as a pulse train signal consisting of pulses representing particle acceleration operation of the particle accelerator, and each time the pulse appears in the synchronization signal, the value of the third voltage at that time is recorded from the previous time. A radiation monitor is configured by adding a digital recorder that integrates and records the recorded value of the third voltage value and also records the number of times the third voltage value is integrated.

3) In the monitor described in either 1) or 2) above, the first-order lag circuit is composed of an operational amplifier whose non-inverting input terminal is grounded, and an input resistor connected to the inverting input terminal of the operational amplifier. and a CR parallel circuit forming a negative feedback circuit of an operational amplifier.

Therefore, with the above configuration, in any monitor, when pulsed radiation appears in the radiation field where the radiation detection section detects radiation, the inverse logarithm conversion voltage of the primary voltage and the inverse of the secondary voltage The voltage difference from the logarithmically converted voltage represents the instantaneous dose rate of pulsed radiation, and the controller also calculates the proportional constant of the primary current to the primary voltage, the proportional constant of the secondary current to the secondary voltage, and the constant current. By setting each value appropriately, the time during which the difference between the primary current and the sum current maintains a positive polarity can be made to approximately match the duration of fluctuations in the radiation dose rate due to the pulsed radiation. In the end, every time pulsed radiation appears, the calculation unit outputs a tertiary voltage representing the dose of this pulsed radiation, and furthermore, the secondary voltage outputted by the first-order delay circuit is equal to the voltage V2 mentioned above. It is clear that by monitoring radiation using these secondary voltages and tertiary voltages, it is possible to easily investigate the cause of the change in the radiation dose rate γ over time. The present invention has the effect of improving the reliability of radiation monitoring.

[Brief explanation of the drawing]

[Fig. 1] Configuration diagram of one embodiment of the present invention

[Figure 2] Diagram explaining the operation of the main parts in Figure 1

FIG. 3 is a configuration diagram of an embodiment of the present invention that is different from the embodiment shown in FIG. 1.

[Figure 4] Configuration diagram of a conventional radiation monitor

[Explanation of symbols]

2 Radiation 6 CR parallel circuit 7 First-order delay circuit 8 Operational amplifier 12a Control signal 13 Control section 21 Radiation monitor 22 Arithmetic unit 24 Radiation monitor 26 Synchronization signal 27 Analog recorder 30 Digital recorder 40 Radiation detection section V1 Primary voltage V2 Secondary voltage V3 Tertiary voltage I1 Primary current I2 Secondary current I3 Constant current R2 Input resistance

Claims (3)

[Claims] 1. A radiation detection unit that detects radiation and outputs a primary voltage representing the logarithm of the irradiation dose rate of this radiation, and a primary lag that smoothes the primary voltage with a long time constant and outputs a secondary voltage. outputting a control signal when the difference between the circuit and a sum current obtained by adding a predetermined constant current to a primary current proportional to the primary voltage and a secondary current proportional to the secondary voltage changes from negative polarity to positive polarity; a control unit that eliminates the control signal after a predetermined delay time when the difference changes from the positive polarity to the negative polarity; and a voltage that corresponds to the inverse logarithm value of the primary voltage when the control signal is input. and a voltage according to the inverse logarithmic value of the secondary voltage, while the control signal is being inputted, and outputs a tertiary voltage representing the integrated value. A radiation monitor characterized in that the radiation is monitored using a tertiary voltage. 2. The monitor according to claim 1, further comprising: an analog recorder for recording secondary and tertiary voltages and a synchronization signal as a pulse train signal consisting of pulses representing a particle acceleration operation of a particle accelerator; It is characterized by adding a digital recorder that records the value of the third voltage at that time by integrating it with the previously recorded value every time the pulse appears, and also records the number of times the value of the third voltage is integrated. radiation monitor. 3. The monitor according to claim 1, wherein the first-order lag circuit includes an operational amplifier whose non-inverting input terminal is grounded, and an input resistor connected to the inverting input terminal of the operational amplifier. , and a CR parallel circuit forming a negative feedback circuit of the operational amplifier.