Methods and devices for measuring the activity of a radioisotope

• US 20050029465A1
• Filed: 12/05/2002
• Published: 02/10/2005
• Est. Priority Date: 12/06/2001
• Status: Active Grant

• Current Assignee: Lemer Protection Anti-X Par Abreviation Societe Lemer Pax
• Original Assignee: Lemer Protection Anti-X Par Abreviation Societe Lemer Pax
• Inventors: Lemer, Pierre-Marie
• Granted Patent: US 7,151,267 B2
• Time in Patent Office: Days
• US Class Current: 250/374
• CPC Class Codes: G01T 1/167 Measuring radioactive content of objects, e.g. contamination whole body counters G01T1/163

Abstract

According to the invention, the method of measuring the activity of a radioisotope (3) placed in an ionisation chamber (1) consists in:—determining the energy spectrum of the radiation emitted by the radioisotope;—automatically comparing said energy spectrum with a set of pre-recorded or pre-programmed radioisotope energy spectra in such a way as to identify the radioisotope present;—subsequently, automatically directing the calibration coefficient corresponding to the radioisotope present to the electronic measuring means in order to obtain the appropriate activity measurement. The invention provides a totally automatic activity measurement. Moreover, the invention also relates to an activity meter with radioisotope recognition which is used to obtain an automatic activity measurement. Said device employs one or more scintillation- or semi-conductor-type radiation detectors (10) for determining the energy spectrum of the radioisotope present.

Claims

1. A method for measuring the activity of a radio-isotope, which method consists in placing said radio-isotope (3) in an ionization chamber (1) capable of providing a current proportional to the activity of said radio-isotope tested, then, using electronic means for processing the signal (15), in converting the value of the current into an activity value, by using a calibration coefficient corresponding to the radio-isotope at hand, characterised in that it consists:

in determining the energy spectrum of the radiation emitted by the radioisotope (3) placed in the ionisation chamber (1),

in comparing automatically this energy spectrum with a set of energy spectra of pre-recorded or pre-programmed radio-isotopes, in order to identify the radio-isotope at hand, then

in allocating automatically to the electronic means for processing the signal (15), the calibration coefficient corresponding to said radio-isotope at hand, to obtain the adequate activity measurement.

2. A method according to claim 1, characterised in that it consists, when the measured spectrum of the radio-isotope (3) under analysis does not correspond to any of the pre-recorded or preprogrammed spectra, in activating automatically a visual and/or selection of the radio-isotope at hand.

3. An instrument for measuring the activity of a radio-isotope, which instrument comprises an ionization chamber (1) connected to electronic means for controlling and processing the signal (15) providing an indication of the activity introduced into said chamber (1), by using a calibration coefficient corresponding to the radio-isotope at hand (3), characterised in that it comprises:

means (10, 11, 161) for analyzing the energy spectrum of the radio-isotope affected (3),

means (162) for comparing automatically the energy spectrum analysed with a set of pre-recorded or pre-programmed spectra (163) in order to identify the radio-isotope at hand, and

means (164) for allocating automatically to said electronic means for processing the signal (15), the calibration coefficient corresponding to said radio-isotope at hand, to obtain the adequate activity measurement.

4. An instrument according to claim 3, characterised in that the means for analyzing the energy spectrum of the radio-isotope (3) are formed of at least one detector (10) of the scintillation or semi-conductor type, associated with electronic and computerized means for processing the signal (161), the photosensitive surface of said detectors (10) being placed in the flux of the primary radiation emitted by the radio-isotope (3) placed in the ionization chamber (1).

5. An instrument according to claim 4, characterised in that it includes at least one detector (10) enabling measurement of the energy spectrum of radio-isotopes, associated with means (13) which enable to limit the flux of the primary radiation emitted by the radio-isotope which strikes its photosensitive surface, to limit the radiation received by said detector (10) and improve the analysis conditions of the spectrum of the radio-isotope at hand.

6. An instrument according to claim 5, characterised in that it includes at least one detector (10) enabling measurement of the energy spectrum of radio-isotopes, associated with a variable aperture diaphragm (13).

7. An instrument according to claim 5, characterised in that it includes at least one detector (10) enabling measurement of the energy spectrum of radio-isotopes, associated with a fixed aperture diaphragm (13).

8. An instrument according to claim 3, characterised in that it includes a plurality of different detectors (10) enabling measurement of the energy spectrum of radio-isotopes, in order to increase the possibilities of identification of the radio-isotopes analysed.

9. An instrument according to claim 3, characterised in that it includes at least one detector (10) enabling measurement of the energy spectrum of radio-isotopes, placed at the bottom of the ionization chamber (1), the support (5) of the container (4) of radio-isotope (3) being fitted with a bottom at least partially radio-transparent, so that flux of the primary radiation emitted by the radio-isotope may strike the photosensitive surface of said detectors (10).

10. An instrument according to claim 4, characterised in that it includes information or alert means (171, 174) activated in case when the spectrum analysed of the radio-isotope at hand does not correspond to any of the pre-recorded or pre-programmed spectra, and means (172, 173) to enable manual selection of the radio-isotope at hand.