CALIBRATION OF THE HIGH AND LOW RESOLUTION GAMMA-RAY SPECTROMETERS

Many laboratories accredited according to the requirements of the standard EN ISO/IEC 17025:2005 "General requirements for the competence of testing and calibration laboratories" are implied in the radioactive content measurement of samples collected from the environment, food chain or industrial products. The most used method is the gamma-ray spectrometry measurement, using high resolution HPGe and low resolution NaI(Tl) detectors. In order to improve its sensitivity, many technical and methodological 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, and true coincidence summing effects (for cascade gamma-ray emitters), as demonstrated during many proficiency tests. The Radionuclide Metrology Laboratory from IFIN-HH, Primary Activity Standard Laboratory, assures the continuity of the whole metrological traceability chain of activity measurement and is accredited by the national accreditation body RENAR as a Calibration and Testing Laboratory, offering products and services for clients. Within the frame of its QMS, RML elaborated two working procedures for the calibration of the gamma-ray spectrometers and the low level radioactive samples activity measurement. The calibration procedures are described, emphasizing the corrections applicable by the measurement laboratories.