Radiant energy – Invisible radiation responsive nonelectric signalling – Luminescent device
Reexamination Certificate
2001-12-14
2003-09-30
Bennett, G. Bradley (Department: 2859)
Radiant energy
Invisible radiation responsive nonelectric signalling
Luminescent device
C250S328000
Reexamination Certificate
active
06627902
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a dose reading device for a fluorescent glass dosimeter detecting the intensity of fluorescence generated upon excitation by ultraviolet light, and more particularly, to a dose reading device having an improved fluorescence reading system for a multiplicity of fluorescent glass elements accommodated in a magazine. Furthermore, the present invention relates to a magazine capable of accommodating a multiplicity of fluorescent glass elements which generate fluorescence upon excitation by ultraviolet light, and more particularly, to a dose reading magazine and a method of manufacture for same, whereby the fluorescence can be read off while the aforementioned elements are accommodated in the magazine. Moreover, the present invention relates to a dose reading magazine, dose reading method and dose reading device, whereby reading of high doses can be performed. Furthermore, the present invention also relates to a dose reading device whereby the weak fluorescence from compact fluorescent glass elements is gathered efficiently, and hence detection sensitivity is improved.
In the installation and operation of facilities such as nuclear reactors, accelerators, X-ray generators, and radio isotopes, it is necessary to achieve complete safety in radiation management, in order to protect human beings from radioactivity. In particular, management must be provided to ensure that the radiation dose to which the employees working in various fields in the aforementioned facilities, and the users of the facilities, are exposed comes within a prescribed tolerance range. Dosimeters are used for radiation management of this kind. These dosimeters are located in prescribed locations within a facility, and/or are carried by employees and users, and by reading out the respective exposure doses thereof at regular intervals, it is possible to manage the radiation doses to which employees and users are exposed.
One type of generally used dosimeter is a fluorescent glass dosimeter. In general, a fluorescent glass dosimeter uses glass elements made from phosphate glass containing silver ions. After being irradiated with radiation and activated, these glass elements generate a phenomenon (radio photo luminescence:RPL) whereby they produce fluorescence when excited by ultraviolet radiation of wavelength 300-400 nm. Since the intensity of the fluorescence produced is directly proportional to the radiation exposure dose received by the relevant glass element, it is possible to measure the radiation exposure dose by detecting the intensity of the fluorescence. A particular feature of fluorescent glass dosimeters of this kind is that they can be read out repeatedly, without the core which generates RPL being destroyed by the reading operation.
In measurement using a fluorescent glass dosimeter of this kind, the light emitted by the ultraviolet excitation light source is passed through an optical filter to selectively extract ultraviolet light of prescribed wavelengths, and is then incident on one face of the fluorescent glass elements. The fluorescent light consequently generated by the fluorescent glass dosimeter is passed through an optical filter to selectively transmit light in a prescribed wavelength range, whereupon it is opto-electrically converted by an photomultiplier tube to obtain an electrical signal having a level that is roughly proportional to the fluorescence intensity, and the fluorescence intensity, and hence the radiation exposure dose is measured from the level of the electrical signal.
In general, as illustrated in
FIG. 27
, a dose reading device for reading out the radiation exposure dose according to the principles described above uses a magazine
3
accommodating a multiplicity of capsules
1
holding a fluorescent glass element
2
therein. This magazine
3
is loaded onto a magazine conveying device
4
by a magazine supply device (not illustrated), and conveyed to a prescribed position. The fluorescent glass elements
2
are then extracted, one by one, from their respective capsules
1
, by means of an extracting device (not illustrated), conveyed to a fluorescence detection position which is shielded from external light, and then are subjected to ultraviolet irradiation and fluorescence quantity detection.
However, a conventional dose reading device as described above involves the following kinds of problems. Specifically, since the fluorescent glass elements accommodated in the magazine must be taken out from the magazine, one by one, and transported to a reading position, in order to perform fluorescence reading, a large amount of time is required to read out the fluorescence quantity of a multiplicity of fluorescent glass elements.
Furthermore, during extraction of the individual fluorescent glass elements from the magazine, or during conveyance thereof, transportation problems may occur, such as the elements catching on surrounding members, or the like. In particular, since the small-sized fluorescent glass elements, described hereinafter, are simple glass elements and do not have a metal frame, or the like, then if a transportation problem arises during loading thereof into a conventional reading device, there is a very high risk of problems such as breaking of the glass, soiling of the surfaces thereof, or degradation of the fluorescence-based measurement accuracy due to the presence of foreign matter.
Furthermore, since a mechanism is required for extracting the fluorescent glass elements individually, there are drawbacks in that the manufacturing costs rise and the size of the overall device increases. In particular, in a dose reading system using small-sized fluorescent glass dosimeters, as used in diagnostic and medical dose evaluation, animal experiment dose evaluation, and various other types of experiments, and the like, since the fluorescent glass elements are very small, they are extremely difficult to extract mechanically.
Moreover, as described above, a dose reading device generally uses a magazine
3
accommodating a multiplicity of fluorescent glass elements
2
held in capsules
1
, as illustrated in FIG.
27
and FIG.
28
. This magazine
3
is loaded from a magazine supply device (not illustrated) onto a magazine conveying device
4
and conveyed to a prescribed position, where the fluorescent glass elements
2
are extracted from their respective capsules
1
, one at a time, by an extracting device (not illustrated), and then conveyed to a fluorescence detection position which is shielded from external light, where they are subjected to ultraviolet irradiation and fluorescence quantity detection. From the viewpoint of moldability, PS (polystyrene), for example, is used as the material for this magazine
3
.
However, since the fluorescent glass elements accommodated in a conventional dose reading magazine of the kind described above must be taken out from the magazine, one by one, and transported to a fluorescent reading position, in order to perform fluorescence reading, a large amount of time is required to read out the fluorescence quantity of a multiplicity of fluorescent glass elements.
Furthermore, during extraction of the individual fluorescent glass elements from the magazine, or during conveyance thereof, transportation problems may occur, such as the elements catching on surrounding members, or the like. In particular, since the small-sized fluorescent glass elements, described hereinafter, are simple glass elements and do not have a metal frame, or the like, then if a transportation problem arises during loading thereof into a conventional reading device, there is a very high risk of problems such as breaking of the glass, soiling of the surfaces thereof, or degradation of the fluorescence-based measurement accuracy due to the presence of foreign matter.
Furthermore, since a mechanism is required for extracting the fluorescent glass elements individually, there are drawbacks in that the manufacturing costs rise and the size of the overall device increases. In particular, in a dose reading sys
Ishidoya Tatsuyo
Sato Motoyuki
Asahi Techno Glass Corporation
Bennett G. Bradley
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