JPS6154487A - Radiation measuring device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention is a radiation measuring device using an ionization chamber, particularly for environmental monitoring in nuclear power plants, etc. The present invention relates to a measuring device that can measure a wide range of radiation levels, including high radiation levels.

[Prior art and its problems]

When measuring the radiation dose rate, it is extremely advantageous if the measuring device has a wide measuring range when the measuring device is to be used for general radiation monitoring. For this reason, conventional radiation measurement equipment using an ionization chamber that detects radiation and outputs a current proportional to the dose rate of 1 uses a logarithmic amplifier to
! It is customary to convert the output current of the output current into a signal f which is logarithmically proportional to the vL current, and measure the dose rate based on this signal t.The logarithmic amplifier is a semiconductor such as a silicon diode or a silicon transistor. Amplifiers using elements or vacuum tubes as feedback elements are used. Such a radiation measuring device R has the following problems.

(1) The maximum measurement range is about 6 digits, and if the measurement range is made wider than this, the measurement error will increase and it cannot be used practically.

(2) The accuracy of radiation dose rate measurement is poor because the output current of the ionization chamber is not directly measured, but the logarithm of this current is measured.

(3) Since the temperature coefficient of the logarithmization circuit of the logarithmic amplifier is large, a temperature compensation circuit is incorporated in the logarithmic amplifier in practice, but even so, the measurement error increases due to the ambient temperature 1.

(4) Logarithmic amplifiers using vacuum tubes have the advantage of having a wider conversion range than those using semiconductor elements. Have difficulty.

For this reason, a logarithmic amplifier is not used.
This analogy has a problem in that the result measuring device requires a plurality of linear amplifiers with different gains, resulting in a large size.

[Purpose of the invention]

The present invention solves the problems of the conventional radiation measuring device (as described above), and enables high-nuclear radiation measurement over a wide measurement range, for example, over a 10-digit measurement range, without using a logarithmic amplifier. To provide a small radiation measurement device capable of determining 6111 degrees of radiation.

The purpose is to

[Key points of the invention]

In order to achieve the above-mentioned object, the present invention provides a radiation measuring device including an ionization chamber, an amplifier for amplifying the output current of the ionization chamber and converting the voltage, and setting the output voltage, pressure, and upper limit of the amplifier. an upper limit comparator that compares the voltage, and a lower limit comparator that compares the output voltage of the amplifier with the lower limit setting voltage;
A reversible counting circuit that performs addition/subtraction and arithmetic operations based on the output signals of both comparators, a decoder that decodes the contents of the reversible counting circuit, and a feedback resistor connected to the feedback circuit of the amplifier in response to the output signal of the decoder. The output signal of the decoder is taken out as a range signal for the selected feedback resistor, and the radiation dose rate is measured based on the output voltage of the amplifier. By configuring the ζ radiation measuring device (in this way), the dose rate of the radiation detected by the ionization chamber, and therefore the output voltage of the amplifier, changes and exceeds the upper or lower set voltage. In this case, return resistors with different resistance values are connected to the feedback circuit via a self-effective resistor switching circuit, and the gain of the amplifier is changed, and the amplifier output voltage and decoder output coefficient in this case are Using this technology, we have made it possible to measure the radiation dose rate with high accuracy over a wide measurement range without using a logarithmic amplifier or multiple linear amplifiers that are used in conventional radiation measurement equipment. It is.

[Embodiments of the invention]

FIG. 1 is a configuration diagram of an embodiment of the radiation measuring device according to the present invention, in which 1 indicates the radiation that is detected and its dose rate 1
2 is an amplifier that amplifies the output current of ionization chamber 1 and outputs a DC voltage 2a proportional to the magnitude of this current; 3 to 7 are n resistors, respectively. Value R,, Tl12. Feedback resistors with R,, R4°BS, 8a to 12a are contacts driven by each of the n relay coils 8 to 12, and 13 is a feedback resistor 3 to
7 is a feedback circuit of the amplifier 2 which is switched and connected by the contacts 8a to 12a1. In this case R,: R,:
R8: R4 knee 11. , =l :10":10'
: 10': 10''
Each resistance value of 7 is determined.

14 is the output voltage of the amplifier, voltage 2a is input, and this voltage Vh
Upper limit setter that outputs 16 is a variable lower limit setting voltage t
A lower limit setter 17 outputs the output voltage 2a and the upper limit setting voltage Vh, and when the magnitude of the voltage 2a exceeds the voltage Vh, outputs an H signal among binary signals consisting of an H signal and an L signal. The upper limit comparator 18 inputs the output voltage 2a and the lower limit setting voltage Vt, and the magnitude of the voltage 2a is the voltage V.
When it becomes smaller than t, it is a lower limit comparator which outputs an H signal among the 1-bit binary signals as described above. In this case (Vh/
Vt) is set to be 100.

Reference numeral 19 denotes a two-man power one-shot circuit to which each output signal of the comparators 17'J6 and 18 is input, and this circuit outputs one pulse-like H signal when either of the two man power outputs exceeds the H signal t. 20 is a two-man powered first A that receives the output signal of the upper limit comparator 17 and the output signal of the one-shot circuit 19, and outputs an H signal when both signals are H signals.
The ND circuit 21 receives the output signal of the lower limit comparator 18 and the output signal of the one-shot circuit 19, and both signals are H.
This is a second AND circuit operated by two people that outputs an H signal if the signal is a signal. The first and second AND circuits 20 and 21 may each be constructed using other logic elements to have similar functions. 22 is a two-man reversible counting circuit having an addition/subtraction terminal 22a and a calculation terminal 22b; in this case, the terminal 22a1 is connected to the output terminal of the first AND circuit 20, and the terminal 22b is connected to the output terminal of the second AND circuit 21. has been done. 23 is the input of the output signal of the reversible counting circuit 22 and the contents of this counting circuit 22)
In this case, the output signals of the decoder are five binary signals 23a, 23b, 23C, 23d, 23e that are output in parallel.
It is made up of. In addition, the signal 23a means the range 1 signal, the signal 23b means the range 2 signal, the signal 23C means the range 3 signal, (the W number 23d means the range 4 signal,
Signal 23e means range 5 signal. In this way, there is one range, or in this example, five ranges. 24~
Reference numeral 28 denotes a relay drive circuit that operates to excite relay coils 8 to 12 when each H signal of signals 23a to 23e is input, and feedback resistors 3 to 7? When the J series coils 8 to 12 are excited and the turning points 8a to 12a operate, the feedback circuit 13t is connected, so the drive circuits 24 to 28
The relay coils 8 to 12 and the contacts 8a to 12a are connected to a resistor switching circuit 2 which connects the feedback resistors 3 to 7 to the feedback circuit 13 in response to the output signals 23a to 23e1 of the decoder 23.
It consists of 9. In this case, make sure that one of the feedback resistors 3 to 7 is connected to the R feedback circuit 13+.
Output signals 23a to 23e and a resistor switching circuit 29 are configured.

Next article ζ The operation of the measuring device shown in FIG. 1 will be explained. In FIG. 1, each part is configured as described above, so in this example, the feedback resistor 5 is connected to the relay contact 10a + the feedback circuit 131 and the output voltage of the amplifier. When the magnitude of the voltage 2a is between the set voltages Vh and Vj, the amount of radiation detected by the ionization chamber 1 increases, and the magnitude of the output voltage 2a becomes larger than the set chamber FIEVh. In this case, the upper limit comparator 17 outputs an H signal. Therefore, one pulse-like H signal is output from the one-shot circuit 19. Since the output signal of the n1 lower limit comparator 18 is a signal at this time, one pulse is output from the LAND circuit 20 to the reversible counting circuit 22. , As a result, the content of the counting circuit 22 increases by one.

The decoder 23 sets the output signal 23b to an H signal and sets the output signal 23C to an L signal according to the count contents of the counting circuit 22 at this time)ζ.
One stiffness is made to serve as a signal. C'
J-ray drive circuit 25. The feedback resistor 4 is connected to the feedback circuit 131 through the relay coil 9 and the contacts 9a and 1, and the feedback resistor 5, which has not been connected to the feedback circuit 131, is fed back through the relay drive circuit 26 and the relay coil IO1 contacts 10a) and 10c. It is disconnected from the circuit 13. At this time, the value of the feedback resistor of amplifier 2 changes from R5 to R21, so the gain of the amplifier becomes 1/100+, and therefore the output voltage 2
The value of a is close to the lower limit set voltage Vt. Voltage Vt
is set to be a value slightly 5 smaller than the magnitude of the output voltage 2a at this time. When the feedback resistor 4 is connected to the feedback circuit 131, the gain of the amplifier 2 is nil/1'OO1 compared to the state where the feedback resistor 5 is connected.
Therefore, the output voltage 2a at this time is 1()0 times the output current of the ionization chamber 1 when the output voltage 2a is the same level in the latter connected state IC. represents the output current of In this state, the radiation dose car is even more
When this increases and the output voltage 2a becomes higher than the upper limit setting voltage Vh again, the upper limit comparator 17, the one-shot circuit 19, the first AND circuit 20. The counting circuit 22 operates once as described above, and at this time the signal 23b becomes an L signal and becomes a signal 2.
3a becomes an H signal. Therefore, the feedback resistor 3 is connected to the feedback circuit 131, and the feedback resistor 4 is disconnected, so the output voltage 2a is 100 times the output of the ionization chamber 1.
It represents electric current.

With the feedback resistor 3 connected to the feedback circuit 13, when the radiation dose rate decreases and the output current of the ionization chamber 1 decreases, the magnitude of the output voltage 2a of the amplifier decreases, and finally the magnitude of t here decreases. When the voltage becomes smaller than the set voltage Vt, the lower limit comparator 18 outputs an H signal. As a result, one pulse-like H signal is output from the one-shot circuit 19.
1 Since the output signal of the upper limit converter leg 17 is a signal at this time, one pulse is output from the second AND circuit 21 to the reversible counting circuit 221, and therefore the counting circuit 22
The content of is decreased by 1. Therefore, the contents of the counting circuit 22 at this time are the same as those when the feedback resistor 4 was connected to the feedback circuit 131 by the decoder 23 and the resistor switching circuit 29, so the decoder output signal 23b
becomes an H signal, and the output signal 23a becomes an L signal. late)
In this case, the feedback resistor of the feedback circuit 13 is switched from resistor 3 to resistor 4t by the resistor switching circuit 291, so the output voltage 2a after switching is the output of the ionization chamber 1 represented by the output voltage 2a before switching. This represents an output current with a magnitude of 1/1O-0 of the type and current.At the time of this switching, the set voltage Vj is set to 1, as described above, so the output voltage 2a is The size is the upper limit setting voltage Vh
(voltage smaller than nearby Vh). In this state, when the fmR rate of radiation decreases drastically and the output '1 voltage 2a becomes smaller than the lower limit setting voltage Vt, the lower limit comparator 18
, the one-shot circuit 19, the second AND circuit 21, and the counting circuit 22 generate ηh in the same manner as described above, and at this time, the signal 23b becomes L.
The signal 23G becomes a signal. Therefore, at this time, the 1iVA measuring device is in the initial state 1 of this operation description, in which the feedback circuit 131 and the feedback resistor 5 are connected.

As described above, the measuring device Ptb in FIG. 1 = B6)
Then, the output fi current of the ionization chamber 1 is 100. Every time 1 times more
The connections of the feedback resistors 3 to 7 are automatically switched by one, and the gain of the amplifier 2 is cut down by 1/1001, and the magnitude of the gain of the amplifier 2 and the output signal 231 of the decoder 23 are
This corresponds to the state of ~23e. death.

Therefore, the state of the output signal of the decoder 23 and the output voltage 2a
What is the magnitude of the output current of ionization chamber 1 and therefore the radiation dose rate? 1l11, and in this case, the gain of the amplifier 2 is switched in 5 steps of 100 times, so this measuring device has a measurement range of 10 digits. Output signal 238 of decoder 23~
Since the state of 23e corresponds to the magnitude of the gain of the amplifier 2, these signals also represent the measurement range. As mentioned above, the output signal 14a of the frequency conversion circuit is a pulse whose frequency is proportional to the output voltage 2a). Therefore, the signal 14al is the output signal 23a of the decoder 23.
By multiplying the weights represented by each of ~23e, the radiation dose rate can be directly measured over a 10-digit measurement range without using a logarithmic amplifier or multiple linear amplifiers.

This measuring device has a 10-digit measurement range, but if the frequency conversion circuit 14 is to output a pulse signal with a frequency proportional to the input signal over the entire measurement range, then this The starting point of the measuring range E is the ending point 1 of the measuring range assuming the frequency of the corresponding pulse signal is 10 (Hz).
The frequency of the corresponding pulse signal is 10rr'+10[H
2], and since the radiation dose rate can be directly measured by counting such pulse signals 1, the measurement error in this case is full scale), whereas α is m+10. Then, the absolute value of this error is 10 Xα×10-2
[:Hz], and this value is α for the frequency 10rn (Hz) of the pulse signal corresponding to the starting point of the measurement range.
XIO (%). Conventional radiation measurement equipment using a logarithmic amplifier had an error of αx1o (%:), but in the measurement equipment 1 shown in Fig. 1,
Any one of the feedback resistors 3 to 7 is the feedback circuit 131
ζ connection and the gain of the amplifier 2 is set to one value GI, the measurement range start point, that is, the minimum value of the output voltage 2a of the amplifier 2 is 1, and the frequency of the output signal 14a of the corresponding frequency conversion circuit is set to 10. If the gain of the amplifier 2 is set to the value G + n, then the frequency of the output signal 14a corresponding to the end point of the measurement range will be n-)-2 10 (Hz). , this 10” (Hz) α [
If the radiation dose rate measurement error of
XIO [%) is which feedback resistor 3 to 7 is connected to the feedback circuit t
There is no change even if I connect this. In other words, in the conventional radiation measuring device using a logarithmic amplifier, the measurement error at the starting point of the measurement range is αX1010[chi]1, whereas in the measuring device shown in Fig. 1, the measurement error at the starting point of the measuring range is αX
10 (%), so the measurement accuracy is significantly improved.

In the above implementation, the ratio between the upper limit setting voltage Vh and the lower limit setting voltage Vt is set to approximately 10 #C, and the gain of the amplifier 2 is set to 1, 10 . 1
0. 10. Although the present invention is not limited to such embodiments, the ratio between the upper limit voltage Vh and the lower limit voltage Vt is set to 1.
Set to a value almost close to a larger positive real number R, and the gain of amplifier 2 is 1, R, R, ..., where S is a positive integer.
. . , 3 feedback resistors may be provided to switch between the S stages of . The circuit 29 receives 5IllSI by this output signal.
The feedback resistor of the amplifier 2 is connected to the feedback circuit 131 of the amplifier 2. Therefore, in a radiation measuring device configured as +c SJ, the amplified human defense force signal or R times 1
Each time, the gain of the amplifier is automatically switched once, and this switching is carried out over the S stage, so that the total measurement rli+5. The measurement accuracy of the above-mentioned measuring device is %R + so that the gain of the amplifier is switched every time the input signal increases by R times. It is clear from the above that the measurement accuracy is better than that of the measuring device used.

Furthermore, in Embodiment 1 of FIG. 1, the gain switching of the amplifier 2 is performed by connecting one feedback resistor to the feedback circuit, but the present invention is not limited to such an embodiment. Instead, the cane switching of the amplifier 2 can be done by appropriately setting the resistance value of each feedback resistor 1. Therefore, it is possible to connect multiple feedback resistors to one feedback circuit, but it is not supported. It is.

In the second embodiment of FIG. 1, the output signal of the first AND circuit 20 is inputted to the addition terminal 22al.

Although the output signal of the second AND circuit 21 is inputted to the subtraction terminal 22b, the present invention is such that the output signal of the first AND circuit 20 is inputted to the subtraction terminal 22blC, and the output signal of the second AND circuit 21 is inputted to the addition terminal 22a. In this case, of course, the resistor switching circuit 29 is configured to reduce the gain of the amplifier 2 when the content of the reversible counting circuit 22 decreases.

In addition, in the embodiment 1c of FIG. 1, the reversible counting circuit 22
The addition/subtraction direction switching circuit is ANDed with the one-shot circuit 19.
For example, the output 5 of the upper limit comparator 17 and the lower limit comparator 18
A one-shot circuit is connected to each of i1jI, and the output signal of each one-shot circuit is directly added to the reversible counting circuit 22.
4 terminal 22a and subtraction terminal 22bl, or similarly both comparators 17.1
A differentiating circuit may be connected to the output side of each of the differential circuits 8, and only the positive pulses of the differential output may be passed through, for example, a die-sinking circuit to the reversible counting circuit 221.

FIG. 2 is a block diagram of another embodiment of the present invention.

In this embodiment, the ionization chamber 1 is composed of an ionization chamber 1, an amplifier 2, feedback resistors 3 to 7, and relay coils 8 to 12), and a frequency conversion circuit 14, setting devices 15, 16, Comparator 17°18, one-shot circuit 19, AND circuit 20°21, reversible counting circuit 22,
The decoder 23 and the relay drive circuits 24 to 28 constitute a measuring section (2). And then, the ionization chamber part■
and measuring section ■ are connected by a cable.

According to the first embodiment having such a configuration, the following advantages can be obtained. That is, in the radiation ionization chamber, minute currents are often measured, and the ionization chamber section (2) is usually housed inside a shield case so as not to be affected by external conduction. In addition, it is housed in a luxurious moisture-proof case so that the insulation resistance of the gauze material does not decrease due to moisture in the air. Therefore, if the ionization chamber part I and the measurement part 2 are separated and only the parts b and pana are housed in a moisture-proof case with an electrostatic shield, the size of the housing case becomes smaller and the product can be manufactured at a lower cost.

In addition, in the embodiment shown in FIG. 2, the ionization chamber 1 and the amplifier 2 are
It is also possible to separate the seven units into separate units. Embodiment 1 of such a configuration Koyowa radiation ionization chamber is W
JIFc or used under high radiation 11. If
Install only the power supply box] under high temperature or high radiation, and then send the output signal using a cable to a place with good conditions.
Therefore, it can be used even at high temperatures or under high radiation conditions.

FIG. 3 is a block diagram of another slightly different embodiment of the present invention. In this first embodiment, the output signal of the AND circuit 20 is input to the subtraction terminal 22b1 of the reversible counting circuit 22, and the output signal of the AND circuit 21 is input to its addition terminal 22a+. Therefore, in the decoder 231,
The output range position is opposite to that of the embodiment shown in FIG.

〔Effect of the invention〕

As explained above, one invention, one invention, and two, electric cod I
L, Yu, an amplifier that amplifies the output current of this α1 box and converts it into voltage and voltage, an upper limit comparator that compares the output W voltage of the amplifier with the upper limit setting α pressure, and the output of the amplifier. A lower limit comparator that compares the heavy pressure and the lower limit set voltage, a reversible counting circuit that performs -C770 subtraction based on the output signals of both comparators, a decoder that decodes the contents of the reversible counting circuit, and an output signal of the decoder that responds to the output signal t. A radiation measuring device is constituted by a resistor switching circuit that connects the feedback resistor to the feedback circuit of the amplifier, and the output signal of the decoder is taken out as a range signal for the selected feedback resistor. With a radiation measuring device like this, 1JL
The dose rate of the radiation edge detected by the unboxing changes, and the output pressure of the amplifier increases or decreases1, and if this voltage exceeds the upper limit setting voltage or lower limit setting voltage, the resistor switching circuit tthus changes the gain of the amplifier. In this case, the amplifier output voltage and the output signal of the decoder can be used to measure the radiation dose rate. This has the effect of being able to measure the radiation dose rate over a wide area without using a logarithmic amplifier or a plurality of edge-shaped amplifiers, and as a result, the constant area of one surface is improved and the measuring device can be made smaller.

[Brief explanation of drawings]

1 to 3 are configuration diagrams of different embodiments of the radiation measuring apparatus according to the present invention. 1...Ionization chamber, 2...Amplifier, 3-7
...Feedback resistor, 13... Feedback circuit, 15... Upper limit setter, 16... Lower limit setter,]7...・Upper limit comparator, 18...
... lower limit comparator, 19 ... one-shot circuit, 20 ... ... first as first logic circuit
ANT) circuit, 21... Second AND circuit as second logic circuit, 22... Reversible measurement circuit, 2
3...Decoder, 29 Kawayama resistor switching circuit, V
h... Upper limit setting pressure, vt... Hashi°' J Fig. 1

Claims (1)

[Claims] an ionization chamber that detects radiation and outputs a current proportional to its dose rate; an amplifier that includes a feedback circuit to which a plurality of feedback resistors are connected in a switched manner and converts the output current of the ionization chamber into a voltage; an upper limit comparator that compares the output voltage of the amplifier with an upper limit setting voltage; a lower limit comparator that compares the output voltage of the amplifier with a lower limit setting voltage; a reversible counting circuit that performs addition/subtraction operations based on the output signals of both the comparators; The output signal of the decoder includes a decoder that outputs a signal according to the contents of the reversible counting circuit, and a resistor switching circuit that connects at least one of the feedback resistors to the feedback circuit according to the output signal of the decoder. A radiation measuring device characterized in that the radiation measuring device extracts the signal as a range signal for the selected feedback resistor, and measures the dose rate of the radiation based on the output voltage of the amplifier.