JP3232617B2 - Inspection method of environmental radiation dose rate meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE regarding this invention inspection calibration environment radiation dose rate meter, such as so-called environmental space gamma dose rate meter for measuring the radiation of the environment using the ionization chamber detector method. In the drawings, the same reference numerals indicate the same or corresponding parts.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing a configuration example of a conventional radiation dose rate meter using an ionization chamber detector. In the figure, 1 is an ionization chamber detector, 2 is a minute current amplifier, 3 is an indicator, and 4 is a detector bias power supply. In FIG. 6, when radiation is detected by the ionization chamber detector 1, the enclosed gas generates ionized ions. A bias voltage is applied to the ionization chamber detector 1 via the power supply 4, and the electric field causes ionization. The ions are collected and become an ionization current, which is input to the minute current amplifier 2. By reading the output voltage of the amplifier 2 through the indicator 3, the radiation dose rate is measured.

FIG. 7 shows a typical example of the detailed configuration of the microcurrent amplifier 2 shown in FIG. 6. In FIG.
(R11, R12) are resistors, and 6 is a range switch. In FIG. 7, when the contact between the contact COM of the range changeover switch 6 and a is conducting, when the ionization current I is input to the amplifier 7, the output voltage V of the operational amplifier 7 is V = − ( I × R11) is generated.

[0004] Since the ionization current I of the ionization chamber detector 1 under appropriate conditions is proportional to the dose rate of radiation, the output voltage V is also proportional to the dose rate. Can be measured. The range changeover switch 6 is provided to switch the value of the resistor R1 so that the output voltage V becomes a value that can be easily read according to the height of the dose rate, so that a wide dose rate range can be measured. Adjust the number of switching according to the measurement range.

FIG. 8 shows an example of the installation of an environmental space gamma dose rate meter for measuring the environmental space gamma dose rate and its calibration device. In the figure, reference numeral 8 denotes a detector storage post installed outdoors, which stores the ionization chamber detector 1 shown in FIG. 1
Reference numeral 1 denotes a measuring unit housing station, which is a small current amplifier 2 shown in FIG.
An indicator 3 and a bias power supply 4 are housed. Reference numeral 9 denotes a calibration device for the dose rate meter, which is attached and used when calibrating the detector storage post 8. Reference numeral 10 denotes a radioisotope (source) for creating a field for a reference dose rate meter to calibrate the dose rate meter.
Has a function of adjusting the distance 1 between the radiation source 10 and the radiation source 10. The distance l is adjusted to create a field of a reference dose rate suitable for calibration.

[0006]

The place where the environmental space gamma dose rate meter is installed is often a general residential area. In such a place, the measurement range of the radiation dose rate meter, especially the high dose rate area, is set. Calibration is difficult because the strength of the source used is subject to legal restrictions. Therefore, in order to calibrate the dose rate meter, it is necessary to remove each device and bring it into a radiation utilization facility having a calibration device for the dose rate meter. For this reason, there is a problem that handling such as removal, attachment, and transportation of each device becomes complicated.

Accordingly, an object of the present invention is to provide an inspection method of an environmental radiation dose rate meter capable of solving such a problem.

[0008]

[0009]

Means for Solving the Problems To solve the above problems,
Inspection method of environmental radiation dose rate meter of claim 1 in order includes an ionization chamber detector for detecting the radiation is applied a bias voltage environment by a bias power source (such as 4) (such as 1), the ionization chamber detector An environmental radiation dosimeter which amplifies the output current of the detector (via the microcurrent amplifier 2 or the like) and outputs the radiation dose rate as a detection output (to the indicator 3 or the like). Current generating means (current generator 13, etc.) for generating a current of one or more predetermined values including an output current value of the ionization chamber detector corresponding to the maximum value of the measurement range of the meter;
In an environmental radiation dosimeter provided with a switching selecting means (switching switch 12 or the like) for switching and selecting the output current of the ionization chamber detector or the current generating means as an object of the amplification, measurement of the dosimeter is performed. The range is defined as a range in which the output current of the ionization chamber detector is proportional to the dose rate to be measured. In the range of the low dose rate in the measurement range, a predetermined radiation source (such as radioisotope 10) which is not regulated by law is used. The output current generated by the ionization chamber detector is selected through the switching selection means, and the output current of the current generation means is selected through the switching selection means in the high dose rate range of the measurement range. Check the function of the dosimeter.

[0010]

[Function] The low dose rate range of the environmental space gamma dose rate meter is calibrated using a radiation source that is not regulated by law, and the higher dose rate range above that is used under appropriate conditions. Using the fact that the output current is proportional to the radiation dose rate of 1,
By using a current generator to calibrate, it is possible to calibrate the entire measurement range of the environmental space gamma dose rate meter without removing the equipment in the installed state.

FIG. 4 shows the radiation dose rate as a parameter.
FIG. 5 is a characteristic diagram showing an example of the relationship between the bias voltage (horizontal axis, logarithmic scale) and the output current (vertical axis, logarithmic scale) of the ionization chamber detector 1. FIG. 5 shows that the bias voltage of the ionization chamber detector 1 is constant. (1
000V) (radiation dose rate (horizontal axis, logarithmic scale))
FIG. 6 is a characteristic diagram showing an example of a relationship between the output current and the output current (vertical axis, logarithmic scale).

FIG. 4 shows that as the radiation dose rate increases, the bias voltage at which the output current of the detector becomes constant increases. For example, the output current to the dose rate at a bias voltage of 1000V is, 1mGy / h → 4.5 × 10 -10 A 10mGy / h → 4.5 × 10 - proportional at ^{8 A - 9 A 100mGy / h} → 4.5 × 10 Although it has to, in the bias voltage 100V, 1mGy / h → 4.5 × 10 -10 A 10mGy / h → 4.4 × 10 - in proportion with ^{8 A - 9 A 100mGy / h} → 3.2 × 10 It turns out there is no.

Next, in FIG. 5, a characteristic curve is a characteristic at a normal time, and an output current of the ionization chamber detector 1 is a radiation dose rate of 100.
Below mGy / h, it is proportional to the radiation dose rate. The characteristic curve is a characteristic in the case where the sealed gas leaks which is considered as a deterioration form of the ionization chamber detector 1, and the output current with respect to the radiation dose rate is smaller than that in the normal case. On the other hand, in order to confirm the soundness of the environmental space gamma dose rate meter, the characteristics of each device, such as the output current characteristics with respect to the radiation dose rate of the ionization chamber detector 1 at the beginning of manufacture, are measured. ,
When the output current of the ionization chamber detector is within a predetermined range with respect to the radiation dose rate (that is, there is no leakage of the sealed gas), the microcurrent amplifier 2 has an output voltage V within a predetermined range with respect to the input current I, It is sufficient to confirm that the indicator 3 gives a predetermined instruction to the voltage V to be applied, and that the bias power supply 4 outputs power with a predetermined specification. In other words, if the conditions are set in an area where the characteristics of the ionization chamber detector 1 are proportional to the dose rate, the output current of the ionization chamber detector 1 is proportional to the dose rate in the entire measurement range of the dose rate. Check the output current value for the dose rate using a known source of a level that is not received, and confirm that it is within the specified range,
Find the proportional constant. In the higher dose rate range, the fact that the output current of the ionization chamber detector 1 is proportional to the radiation dose rate is used to obtain the current for the dose rate to be checked from the previously obtained proportionality constant, and these currents are calculated. In addition to the minute current amplifier 2, the output voltage V and the indication of the indicator 3 are checked.

Further, it is sufficient to confirm whether the bias power supply 4 satisfies the specifications separately. As described above, the soundness of the entire measurement range of the environmental gamma dose rate meter can be checked.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Fig. 1 shows the dose to which the inspection method of the present invention is applied.
FIG. 7 is a block diagram showing a schematic configuration of the rate meter, and corresponds to FIG.
FIG. 2 is a detailed view of FIG. In FIG. 1, what is different from FIG. 6 is a current generator 13 and a changeover switch 12 for switching the input to the minute current amplifier 2 to the current generator 13 or the ionization chamber detector 1.

The current generator 13 comprises a resistor R2 (R21, R22), a DC power supply 16, and a changeover switch 15, as shown in FIG. The changeover switch 15 switches the output current of the current generator 13 determined by the resistance R2 and the voltage of the DC power supply 16. The output current of the current generator 13 can be set to a desired value by appropriately selecting the voltage of the DC power supply 16 and the value of the resistor R2.

As described with reference to FIG. 7, the microcurrent amplifier 2 is provided with a range changeover switch 6 for switching one or a plurality of ranges in accordance with the measurement range of the radiation dose rate. In order to confirm the above, the voltage of the DC power supply 16 and the resistance value R2 are selected so that a current suitable for the range can be output from the current generator 13, and are switched by the changeover switch 15 and supplied to the minute current amplifier 2.

FIG. 3 shows a configuration in which the microcurrent amplifier 2 is configured as a logarithmic amplifier. In FIG. 3, reference numeral 21 denotes an operational amplifier, 22 denotes a logarithmic element such as a diode, 23 denotes a resistor, and 24 denotes a DC voltage generator. . In the case of the microcurrent amplifier 2 having the configuration shown in FIG. 3, the output is a logarithmic value. However, it is difficult to check the low dose level using the radiation source and check the high dose level using the current generator 13 as shown in FIG. The same is true.

[0019]

According to the present invention, the ionization chamber detector of the environmental radiation dose rate meter is used in a range where the output current is proportional to the dose rate, and a radiation source which is not regulated by law in the low dose rate range is used. In the higher dose rate range, use the proportional constant of the dose rate versus the output current of the ionization chamber detector in the lower dose rate range, and use the current of the current generator to measure the environmental radiation dose rate. Can be checked, and these checks can be performed with the environmental radiation dose rate meter installed, making handling much easier.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a dose rate meter to which an inspection method of the present invention is applied .

FIG. 2 is a circuit diagram showing one embodiment of the detailed configuration of FIG. 1;

FIG. 3 is a circuit diagram showing an embodiment of a detailed configuration different from FIG. 2 of the micro-current amplifier of FIG. 1;

FIG. 4 is a characteristic diagram showing an example of a relationship between a bias voltage and an output current of an ionization chamber detector.

FIG. 5 is a characteristic diagram showing an example of a relation between a dose rate and an output current of an ionization chamber detector.

FIG. 6 is a conventional block diagram corresponding to FIG. 1;

FIG. 7 is a detailed circuit diagram of the minute current amplifier of FIG. 6;

FIG. 8 is a layout diagram showing an example of an installation state of an environmental space gamma dose rate meter and its calibration device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ionization chamber detector 2 Microcurrent amplifier 3 Indicator 4 Detector bias power supply 9 Calibration device 10 Radioisotope (ray source) 12 Changeover switch 13 Current generator 15 Changeover switch 16 DC power supply R2 (R21, R22) Resistance

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-2682 (JP, A) JP-A-62-235589 (JP, A) JP-A-62-8087 (JP, A) JP-A 63-235 314490 (JP, A) JP-A-62-245987 (JP, A) JP-A-1-272989 (JP, A) JP-A-61-94789 (JP, U) JP-A-62-167185 (JP, U) U.S. Pat. Appln. No. 2-93784 (JP, U) U.S. Pat. No. 5,015,592 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01T 1/16 G01T 1/185 G01T 7/00

Claims (1)

(57) [Claims] 1. An environment in which a bias voltage is applied by a bias power supply and an ionization chamber detector for detecting radiation in the environment is provided. A radiation dose rate meter, current generation means for generating one or more predetermined value currents including an output current value of the ionization chamber detector corresponding to a maximum value of a measurement range of the environmental radiation dose rate meter; An environmental radiation dosimeter comprising: an ionization chamber detector or a switching selection means for switching and selecting the output current of the current generation means as an object of the amplification. In the range where the output current of the detector and the measured dose rate are in proportion, the output current generated by the ionization chamber detector by a predetermined radiation source that is not regulated by law in the low dose rate range of the measurement range is Switching selection means In the high dose rate range of the measurement range, the output current of the current generating means is selected through the switching selection means, and the function of the dose rate meter is checked. How to check the environmental radiation dose rate meter.