Gamma Irradiation TechTip

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ATTRIBUTE ALANINE DOSIMETRY SYSTEM RED 4034 DOSIMETRY SYSTEM
Instrumentation Electron paramagnetic resonance (EPR) spectrometer SpectrophotometerMicrometer
Dosimeter Description Alanine substrate pressed into pellet shape with wax for binding material. Pellet is placed into a film package with a bar code that cannot be separated from the film package. Polymethylmethacrylate (PMMA) molded sheets cut into ~ 3.0×1.1×0.55 mm pieces. Hermetically sealed in a film package.
Dosimeter Response
(per ASTM)
Dosimeter contains crystalline alanine and registers the absorbed dose by the formation of alanine-derived free radicals. Identification and measurement of the alanine-derived free radicals are performed by EPR spectroscopy.ISO/ASTM 51607 Standard Practice for Use of an Alanine-EPR Dosimetry System Induction of chemical reactions resulting from irradiation, which create absorption bands in the visible and/or UV regions of the spectrum. Optical absorbance is determined at appropriate wavelengths within these radiation-induced absorption bands and is quantitatively related to absorbed dose.ISO/ASTM 51276 Standard Practice for Use of a Polymethylmethacrylate Dosimetry System
Dosimeter Measurement Process Insert alanine dosimeter into spectrometer, system automatically transfers dosimeter bar code into software and begins taking measurementDose calculated Users remove dosimeter from packetPlace dosimeters into holder that holds 8 dosimeters

Place holder into spectrophotometer and absorbance transferred into software

Remove dosimeters from holder and read thickness of dosimeters, one at a time

Thickness automatically transferred into software

Dose calculated

Influence Quantities
(per ASTM)1
Temperature, pellet massISO/ASTM 51607 Standard Practice for Use of an Alanine-EPR Dosimetry System Temperature, humidity, dose rate, post-irradiation responseISO/ASTM 51276 Standard Practice for Use of a Polymethylmethacrylate Dosimetry System
Typical Dosimeter System Uncertainty
(per ASTM)
± 4%ISO/ASTM 51607 Standard Practice for Use of an Alanine-EPR Dosimetry System ± 6%ISO/ASTM 51276 Standard Practice for Use of a Polymethylmethacrylate Dosimetry System
Typical Dose Range 0.5-150 kGy 5-50 kGy

 

1 Influence quantities are compensated for by either the user or the dosimeter manufacturer.