Calibration of the high and low resolution gamma-ray spectrometers

摘要

Many laboratories accredited according to the requirements of the standardEN ISO/IEC 17025:2005 "eneral requirements for the competence of testing andcalibration laboratories"are implied in the radioactive content measurement of samplescollected from the environment, food chain or industrial products. The most usedmethod is the gamma-ray spectrometry measurement, using high resolution HPGe andlow resolution NaI(Tl) detectors. In order to improve its sensitivity, many technical andmethodological aspects are important: careful choice of detector material and shielding,samples matrix, measurement of high volume samples in close to detector geometries.The results are strongly influenced by the geometry, sample volume and content, andtrue coincidence summing effects (for cascade gamma-ray emitters), as demonstratedduring many proficiency tests. The Radionuclide Metrology Laboratory from IFIN-HH,Primary Activity Standard Laboratory, assures the continuity of the whole metrologicaltraceability chain of activity measurement and is accredited by the nationalaccreditation body RENAR as a Calibration and Testing Laboratory, offering productsand services for clients. Within the frame of its QMS, RML elaborated two workingprocedures for the calibration of the gamma-ray spectrometers and the low levelradioactive samples activity measurement. The calibration procedures are described,emphasizing the corrections applicable by the measurement laboratories.