Refusable personal monitoring device

Details Refusable personal monitoring device Refusable personal monitoring device

1999-10-26

2003-11-04

Patel, Vip (Department: 2879)

Electric lamp and discharge devices

With luminescent solid or liquid material

Solid-state type

C313S483000, C315S169300

Reexamination Certificate

active

06642650

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a reusable personal monitor in form of a handsome card providing a quantitative determination of harmful threatening ionizing irradiation.
BACKGROUND OF THE INVENTION
Dosimeters suitable to detect and to quantify harmful or threatening ionizing irradiation are known for years. Especially people working with radioactive isotopes as in analytical research laboratories, in nuclear medical research, in nuclear power-stations and in non-destructive testing of materials should be under permanent preventive controll in order to be informed about the dose of ionizing radiation to which they have been exposed within a well-known working time. Well-known types of dosimeters are e.g. based on CsI-crystal scintillators, mostly in form of a pencil, which provide permanent controll. When a quantified critical or treshold value becomes exceeded, a system in form of a sound alarm may warn the controlled person. Nowadays electronic gadgets such as personal identification, personal “irradiation history”, etc., have become available, even in contact with a network, in order to maximize personal security measures.
Another detection system makes use of detectors in form of a badge which, after having been borne during a certain period of time are controlled centrally. Quantifying irradiation can be based on silver halide photography (as e.g. in nuclear power-stations, described as in “Gebrauchsanweisung für das Personendosimeter mit Ganzkörperdosimetersonden, Typ GSF-Film-GD 10/20, GSF-Forschungszentrum für Umwelt und Gesundheit GmbH—Institut für Strahlenschutz—Auswertungsstelle für Strahlendosimeter—Stand: 1 März 1994). Another quantifying method can be based on thermoluminescence (e.g. with LiF detectors) or on PSL-dosimetry wherein phosphate glass becomes stimulated with a pulsed ultraviolet laser and wherein erasure is performed thermically. Advantageously both detection systems based on thermoluminescence and PSL-dosimetry can be reused.
Another detector offering the same advantage of reusability is a stimulable phosphor medium as has been disclosed in EP-A 0 844 497 and in EP-A 0 892 283.
In EP-A 0 844 497 a method has been disclosed of checking whether an article has been inspected by penetrating radiation. In particular however it relates to a method making it possible to check whether if a piece of luggage has been inspected by X-rays and to a method for personal monitoring. Therein a label according to the first embodiment of this invention can beneficially be used as means for personal monitoring. When a person working in an environment with penetrating radiation carries such a label, the label can be used to determine the dose of penetrating radiation absorbed by that person. The amount of energy of the penetrating radiation stored in the phosphor is proportional to the absorbed dose and can be read out and the remaining amount of energy stored in the phosphor can be erased by erasing radiation. It was found that the ease of erasure was related to the energy of the penetrating radiation that irradiated the label. E.g. energy stored in the label by irradiation with Co
60
(1 MeV) radiation is less easily erased than the energy stored in the label by irradiation with penetrating radiation of 50 keV. Thus the time needed to erase the amount of energy stored in the phosphor to a given level is a function of the energy of the penetrating radiation that left said amount of energy stored in the phosphor and by checking the amount of energy left in the phosphor after a given time the energy of the penetrating radiation can be determined. It is clear that for each type of storage phosphor used in the label a calibration of the readings both to determination of the amount of energy stored and to the determination of the energy of the radiation causing the amount of energy to be stored has to be performed. This can easily be done by irradiating the label with a known dose of penetrating radiation of known energy and reading out the amount of energy stored in the phosphor (this is proportional to the absorbed dose) and erasing the amount of energy stored in the phosphor and controlling at given time intervals the amount of energy left in the phosphor (this is proportional to the energy of the penetrating radiation to which the label with the phosphor has been exposed). The phosphor can be calibrated so that the energy of the penetrating radiation can be assessed by reading the time needed to reach an erasure depth (erasure depth: the degree to which the amount of energy stored has been erased.).
Therefore the invention encompasses a method for personal monitoring comprising the steps of
providing a person entering an area where penetrating radiation is used with a label comprising a storage phosphor wherein an amount of energy of said penetrating radiation, proportional to a dose absorbed by said phosphor is stored,
reading out said amount of energy stored in said phosphor, assessing said absorbed dose, while leaving a fraction of said stored energy in said phosphor,
erasing said fraction of said stored energy from said phosphor by overall exposure to erasing radiation during an erasing time to reach a predetermined erasure depth, and noting said erasure time.
In a label according to the first embodiment of that invention and used for personal monitoring it is possible to incorporate different phosphors for the detection of penetrating radiation of different energy. As suggested it is, e.g. possible to include in the label a first patch of phosphor dedicated to the detection of Co
60
radiation, a second patch of phosphor dedicated to the detection of Ir
192
radiation, a third patch of phosphor dedicated to the detection of radiation of X-ray between 50 and 400 keV, a fourth patch of phosphor dedicated to the detection of ultraviolet radiation. It is also possible to cover a label, according to the first embodiment of that invention, used for personal monitoring, wherein only one type of phosphor is present with different filters so that , e.g., on one patch of the phosphor a filter letting only Co
60
radiation pass is present, on a second patch a filter letting only Ir
192
radiation pass, on a third patch a filter letting only pass X-rays with energy between 50 and 400 keV, etc.
In a second embodiment of that invention, means for storing energy of penetrating radiation are means that convert the energy of absorbed penetrating radiation into electrons, these electrons being stored in an electronic memory that can repeatedly be read-out.
In EP-A 0 892 283 a personal monitor has been disclosed comprising a storage medium for absorbing incident radiation energy, wherein said storage medium comprises a storage phosphor panel capable to store radiation energy originating from radiation having a wavelength of 350 nm or less, wherein said panel is covered with an optical filter absorbing radiation having a wavelength of 350 nm or more and wherein said panel is present in a housing, being preferably provided with a shutter element to avoid exposure at those moments when it is undesirable or irrelevant. More particularly said incident radiation is therein substantially composed of UV-B and UV-A rays in the wavelength range from 250 to 350 nm and said storage phosphor panel comprises storage phosphors having a dark decay of 2 hours or more as it was an object of that invention to provide a personal monitor as an indicator making it possible to check in a quantitative way any amount of harmful (sun) rays irradiating the human skin, more in particular to provide a quantitative indicator for measuring irradiation of the human skin by (over)exposure to harmful UV-A and UV-B radiation originating from sun-rays and/or solar panels and to provide a method for quantitatively checking the amount of accumulated radiation and comparing it with radiation doses tolerable within a certain exposure time as a function of age, location on earth, skin type, protection factor of sun cream used, etc. Said personal monitor therefore further comprises a digital memory storing

Affiliated with

Also associated with

Rating

Refusable personal monitoring device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Refusable personal monitoring device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Refusable personal monitoring device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3172855