JPH07113871A - Fluorescent-glass dosimeter - Google Patents

Abstract

PURPOSE:To accurately calibrate a measured dose by correcting a natural exposure dose of an internal calibration glass element by using a natural exposure dose obtained from a natural exposure monitoring element. CONSTITUTION:A reference exposure value D is inputted at the time of an external calibration. After an external calibration glass element 21 is conveyed to a measuring position 23 by a conveyor 22, an ultraviolet ray is excited, and a fluorescence read value C of the element 21 is read by a reader 1. Similarly, fluorescent read values B0, E0 of an internal calibration glass element 25 and a natural exposure monitoring glass element 26 are read. A dose value of the element 25 is decided by using the data. Thereafter, a fluorescence read value A of a dose measuring glass element 27 (fluorescent glass dosimeter) is read, and a true do is obtained. An internal calibration process is executed at each predetermined period. In this case, fluorescence read values Bn, En of the elements 25, 26 are read. Up to following internal calibration, when the read value A of the element 27 is read, a true dose read value is obtained by a formula. Thus, a dose read value of the dosimeter can be calibrated without external calibration for a long period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent glass dosimeter measuring device for measuring the radiation exposure dose of a fluorescent glass dosimeter, and in particular, an internal calibration used as a reference when measuring the radiation exposure dose of the fluorescent glass dosimeter. The present invention relates to a fluorescent glass dosimeter measuring device having an improved means for correcting the natural exposure dose of glass.

[0002]

2. Description of the Related Art Generally, phosphate glass containing silver ions (also referred to as silver activated phosphate glass) is used in fluorescent glass dosimeters. When the phosphate glass is exposed to radiation and exposed to light, fluorescent centers are generated in the glass body. In this state, when the phosphate glass is excited with ultraviolet rays, orange fluorescent radiophotoluminescence is generated. Since the fluorescence intensity at this time is proportional to the radiation dose, the radiation dose can be measured by detecting this fluorescence intensity.

Such measurement of the radiation dose is performed by blocking the light from the light source for exciting the ultraviolet light having a predetermined wavelength or more through an optical filter and then transmitting the transmitted ultraviolet light to one side of a rectangular parallelepiped-shaped phosphate glass. Incident vertically on. Then, the fluorescence emitted from the phosphate glass by the excitation of the ultraviolet rays is extracted from the direction perpendicular to the incident light, and the transmitted light in the predetermined wavelength range is further extracted through the filter, and then converted into an electric signal by the photomultiplier tube. By doing so, the fluorescence intensity is measured from this electric signal level, and the exposure dose is obtained.

In the measurement of such a radiation dose, a calibration glass is used as a fluorescent standard glass which generates a predetermined fluorescence amount (calibration dose) in advance. The calibration dose and the phosphate of this calibration glass are used. The amount of radiation exposure of the phosphate glass is determined by comparing the amount of fluorescence emitted from the glass.

When calibrating such a fluorescent glass dosimeter measuring device, the following two types of calibration methods are used.

(1) External calibration This external calibration is performed to ensure the traceability (high standard) of the dose measurement value, and a reference radiation dose (hereinafter referred to as a reference irradiation value) is set in advance. The internal calibration glass incorporated in the fluorescent glass dosimeter measuring device is priced using the irradiated external calibration glass. This valuation is to determine the dose value of the internal calibration glass by using the reference irradiation value of the external calibration glass or the like. This calibration operation is performed at the time of initial setting at the installation stage of the apparatus and periodically (for example, once every 3 months or once every 6 months).

(2) Internal Calibration In this internal calibration, the measuring device is calibrated in daily use by using the internal calibration glass valued by the external calibration glass. This calibration operation is automatically performed at the start of measurement and every predetermined number of measurements.

Incidentally, the following relational expression is established between the above two types of calibration glass and the dose measurement value of the fluorescent glass dosimeter after calibration.

Dose measurement value = A · (B ₀ / Bn) · (D / C) where A: fluorescence reading value of fluorescent glass dosimeter (value after A / D conversion proportional to exposure amount, , B ₀ : Fluorescence reading of internal calibration glass when external calibration is performed, Bn: Fluorescence reading of internal calibration glass when internal calibration is performed, C: Fluorescence of external calibration glass when external calibration is performed Read value, D: Reference irradiation value of external calibration glass when external calibration is executed.

[0010]

However, the above calibration method has the following problems.

When the interval for performing the external calibration using the external calibration glass is relatively long, the internal calibration glass inside the measuring device receives a natural exposure of 0.6 mSv to 2 mSv per year, and the fluorescence intensity gradually increases. The calibration error of the device, that is, the measurement error of the fluorescent glass dosimeter cannot be ignored.

As a solution to this problem, it is conceivable to increase the frequency of calibration by the external calibration glass. However, since the external calibration glass itself also receives natural exposure and the dose value increases, external calibration is performed. It is necessary to perform the reference irradiation of the external calibration glass every time, and there is a problem that the calibration work becomes complicated.

On the other hand, the natural exposure dose of the internal calibration glass is calculated from the period from the execution date of the external calibration to the execution date of the internal calibration and the correction coefficient representing the natural exposure dose per unit time, and this calculated value is used. Although a method of performing internal correction by performing correction by using the above method is also conceivable, when there is a change in the natural exposure dose per unit time with respect to time, the change amount becomes the correction error as it is.

Further, Japanese Laid-Open Patent Publication No. 3-291593 proposes a method of increasing the dose value of the internal calibration glass in advance to reduce the influence of natural exposure. In this case, however, the error due to natural exposure is relatively large. However, if the dose measurement value of the dosimeter is small, there is a problem with a large error as described above.

The present invention has been made in view of the above circumstances, and appropriately corrects the natural exposure dose of the internal calibration glass,
It is an object of the present invention to provide a fluorescent glass dosimeter measuring device that accurately calibrates measured dose values without performing external calibration.

[0016]

In order to solve the above problems, the invention according to claim 1 is a fluorescent glass dosimeter measuring device for measuring the radiation exposure dose of a fluorescent glass dosimeter, which is built in the device. , An internal calibration glass element having a calibration dose for calibrating the radiation exposure dose of the dosimeter, a natural exposure monitor element for monitoring the natural exposure dose of the internal calibration glass element, and a natural exposure monitor element during internal calibration Measured dose correction means for correcting the natural exposure dose of the internal calibration glass element using the natural exposure dose and for calibrating the radiation exposure dose of the dosimeter using the corrected calibration dose of the internal calibration glass element And a fluorescent glass dosimeter measuring device provided with.

[0017]

Therefore, in the invention corresponding to claim 1, by taking the above-mentioned means, the internal calibration glass element for calibrating the radiation exposure dose of the fluorescent glass dosimeter after the external calibration is naturally exposed as the period elapses. However, a natural exposure monitor element for newly monitoring the natural exposure dose is provided, and the natural exposure dose of the internal calibration glass element is corrected using the natural exposure dose of the monitor element during internal calibration, and the internal calibration glass element is corrected. Since the radiation exposure dose of the fluorescent glass dosimeter is calibrated using only the calibration dose of the above, it is possible to measure the radiation exposure dose of the dosimeter with high accuracy by using only the internal calibration without performing the external calibration.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a fluorescent glass dosimeter measuring device according to the present invention. This measuring device is a glass element for exposure dose measurement (fluorescent glass dosimeter), an external calibration glass element, an internal calibration glass element, a natural exposure monitor glass element, etc. A reading device 1 for detecting the amount of fluorescence emitted from the device, an input device 2 for inputting instruction data necessary for calculation, a reference irradiation value for irradiating an external calibration glass element when performing external calibration, and each fluorescence read by the reading device 1. A data calculation processing unit 3 that executes a predetermined process using a read value or a reference irradiation value input from the input device 2, read data by the reading device 1 and a reference irradiation value from the input device 2, and further calculation processing. It comprises a storage unit 4 for storing process data, a display unit 5 for outputting a calculation result, and a printer 6.

The data calculation processing section 3 has the function shown in FIG. The data calculation processing unit 3 inputs the reference irradiation value when the external calibration glass element is irradiated with the reference radiation amount when executing the external calibration from the input device 2 and stores it in the storage unit 4. A reading glass fluorescence amount reading and storing means 12 for reading the fluorescence amount emitted by the excitation of ultraviolet rays to the external calibration glass element, the internal calibration glass element and the natural exposure monitor glass element during external calibration and storing them in the storage section 4, The fluorescence amount read value obtained by the pricing glass fluorescence amount reading and storing means 12 and the reference irradiation value input storing means 11
The internal calibrating glass valuing means 13 for determining the exposure dose of the internal calibrating glass element using the reference irradiation value stored by the calibrating means, and the internal calibrating glass, that is, the internal calibrating glass element and the natural exposure monitor glass element are measured at the measuring positions. Glass feeding means 14 for internal calibration processing, the glass fluorescence amount reading means 15 for internal calibration processing for reading the amount of fluorescence emitted by the excitation of ultraviolet rays to each glass element set by this feeding means 14, and a glass element dosimeter And a measurement dose correction means 16 for correcting the measurement result of 1.

Next, the operation of the measuring apparatus having the above configuration will be described with reference to FIG. First, when performing the external calibration, the external calibration glass element 21 is irradiated with the reference radiation dose, and the reference irradiation value D at this time is input from the input device 2 (reference irradiation value input storage means 11). The reference irradiation value D from the input device 2 may be input after the next execution of the pricing glass fluorescence amount reading and storing means 12 instead of at this time.

The glass fluorescence amount reading / storing means 12 for pricing
Then, after the external calibration glass element 21 is transported to the measurement position 23 by the transport mechanism 22, ultraviolet rays are excited, and the fluorescence reading value C of the external calibration glass element 21 is read by the reading device 1 and stored in the storage unit 4. . Further, in the transport mechanism 24, the internal calibration glass 25 and the natural exposure monitor glass element 26 are used.
Set in order to measure the position 23, similarly fluorescence readings B ₀ of the internal calibration glass element 25 at the time of external calibration run, stored natural exposure monitoring fluorescent glass element 26 readings E ₀ read in the storage unit 4 .

When D, C, B ₀ and E ₀ have been obtained as described above, these data D, C, B ₀ and E ₀ are successively _read.
By using (B ₀ −E ₀ ) · (D / C) (1)
Determine the dose value of. That is, the internal calibration glass element 25
Is performed (internal calibration glass pricing means 13).

Therefore, at this point in time, since the fluorescence reading value Bn of the internal calibration glass element 25 and the fluorescence reading value En of the natural exposure monitor glass element 26 at the time of executing the internal calibration are just after the external calibration, the internal calibration is performed. However, since it is considered that there is no change in the fluorescence reading values of the glass elements 25 and 26, Bn = B ₀ and En = E ₀ are stored in the storage unit 4.

After that, if the fluorescent glass dosimeter before internal calibration, that is, the dose measuring glass element 27 is carried by the carrying mechanism 22 and set at the measuring position 23, the fluorescence reading value A is read by the reading device 1, The following measured dose correction means 16 is executed to obtain a true dose measurement value.

True dose measurement value = A · {(B ₀ −E ₀ ) / (B ₀ −E ₀ )} · (D / C) = A · (D / C) (2) Then, the period Since the internal calibration glass element 25 is naturally exposed with the passage of, if the internal calibration glass element 25 is used for the internal calibration as it is, an error due to the natural exposure will occur.

Therefore, in this apparatus, the internal calibration processing and the error correction processing are carried out at every predetermined time. At this time, the internal calibration glass element 25 and the natural exposure monitor glass element 26 are transported by the transport mechanism 24. Measurement position 23
(Conveying means 14), and the fluorescence reading values Bn and En of the glass elements 25 and 26 are read by the excitation of ultraviolet rays (reading means 15).

Therefore, until the subsequent internal calibration, when the fluorescence read value A of the fluorescent glass dosimeter, that is, the dose measuring glass element 27 is read, the true dose read value can be obtained by the following equation (3). .

True dose measurement value = A · {(B ₀ −E ₀ ) / (Bn −En)} · (D / C) (3) Therefore, according to the configuration of the above embodiment, After performing the external calibration, when the interval for executing the next external calibration is long, the fluorescence reading value Bn of the internal calibration glass element 25 and the fluorescence of the natural exposure monitor glass element 26 accompanied by the natural exposure obtained during the internal calibration. Since the read value En is measured and the correction processing is always performed so as to subtract the natural exposure amount of the internal calibration glass element 25 as shown in the formula (3),
Dose readings of fluorescent glass dosimeters can be calibrated with high accuracy without external calibration for a long period of time.

The present invention is not limited to the above embodiment. In the present embodiment, the natural exposure monitor glass element 26 is incorporated in the measuring device, but if it is stored and used in a position that correctly monitors the natural exposure amount of the internal calibration glass element 25, The external calibration glass element 2 does not necessarily have to be built in the measuring device.
As in the case of 1, the measurement position 23 may be externally set at the time of calibration.

Besides, the present invention can be variously modified and implemented without departing from the gist thereof.

[0032]

As described above, according to the present invention, even if there is a change in the natural exposure dose of the internal calibration glass, the dose measurement value can be calibrated with high accuracy only by internal calibration without external calibration for a long period of time. A fluorescent glass dosimeter measuring device can be provided.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a fluorescent glass dosimeter measuring device according to the present invention.

FIG. 2 is a diagram showing a functional configuration of a data calculation processing unit shown in FIG.

FIG. 3 is a diagram illustrating an operation during calibration processing.

[Explanation of symbols]

1 ... reading device, 2 ... input device, 3 ... data operation processing unit,
4 ... Storage unit, 21 ... External calibration glass element, 25 ... Internal calibration glass element, 26 ... Natural exposure monitor glass element, 2
7 ... Dose measurement glass element (fluorescent glass dosimeter).

Claims (1)

[Claims] 1. A fluorescent glass dosimeter measuring device for measuring a radiation exposure dose of a fluorescent glass dosimeter, comprising: an internal calibration glass element which is built in the device and has a calibration dose for calibrating the radiation exposure dose of the dosimeter. Natural exposure monitor element that monitors the natural exposure dose of this internal calibration glass element, and corrects the natural exposure dose of the internal calibration glass element by using the natural exposure dose obtained from the natural exposure monitor element during internal calibration, and A fluorescent glass dosimeter measuring device comprising: a measured dose correcting means for calibrating the radiation exposure dose of the dosimeter using the corrected calibration dose of the internal calibration glass element.