O24. Calibration of radiation monitoring instruments at the NMISA

Abstract

Introduction Radiation monitoring instruments are calibrated to ensure measurements of the instrument are reliable and accurate in all ranges and for energy spectrum in which the instrument is expected to function. The Dosimetry Section (Radiation Protection) of NMISA provides the calibration service for all types of radiation monitoring instruments. This paper will focus on the calibration of surface contamination monitor in terms of 2 π efficiency and surface activity response (SAR), survey meter in terms of ambient dose equivalent (ADE) rate and electronic personal dosimeter (EPD) in terms of personal dose equivalent (PDE). Measurements are traceable to the national standards calibrated at NPL, PTB and BIPM. Materials and methods Measurements for determining the 2 π efficiency and surface activity response of the surface contamination monitor were performed using the wide area reference sources and linearity measurements were performed using Cs-137 source. Survey meter and electronic personal dosimeter were calibrated using Cs-137 and Am-241 sources. Calibrations were performed in accordance with ISO 4037-3, ISO 8769 and SANAS TR 18-02. IAEA report series no. 16 is also used as a guideline. Results The uncertainties in the 2 π efficiency and surface activity response were estimated not to exceed ± 11% and ±4,0% respectively. For the survey meter and electronic personal dosimeter, the average error for all calibrated ranges did not exceed ±15% and the average percentage error per point for all ranges did not exceed ±25%. Conclusion The results obtained from calibrations were conforming to the SANAS TR 18-02 requirements and certificates issued in accordance with the ISO/IEC 17025:2005.