Gabon results for the 2018 IAEA regional intercomparison exercise on measurements of the personal dose equivalent Hp(10) in photon fields and additional tests

Abstract

The study provides the overall results of the national individual monitoring service in Gabon obtained during the 2018 International Atomic Energy Agency Africa region intercomparison exercise on measurements of the personal dose equivalent Hp(10) in photon fields. The dosimetry system tested was the microStar InLight dosimetry system (Landauer, Inc., USA). The results were assessed using the trumpet curve. Requirements for photon energy, linearity, coefficient of variation and mixed irradiations were also assessed against IEC 62387 standard. The reader stability, zero dose, recording levels and the ability of the dosemeter to act as a crude energy spectrometer for low energy photons were evaluated as well. The results for reader stability were in line with the manufacturer’ specifications, and the photomultiplier tube count measurements relative to the dark current and the built-in 14C radioactive source passed the chi-square test proposed. Monthly and quarterly recording level and zero dose values were calculated to be 0.057 ± 0.003 mSv, 0.05 ± 0.01 mSv and 0.110 ± 0.001 mSv, respectively. The overall results obtained during the 2018 intercomparison exercise met the requirement for overall accuracy (trumpet curve). For the dose equivalent, photon radiation energy and angle of incidence ranges tested, the results for coefficient of variation, energy dependence and mixed irradiations met the corresponding IEC 62387 standard requirements. The results for linearity were considered satisfactory with respect to the corresponding IEC 62387 standard requirement. The method proposed to estimate workplace low photon energies provided better results than the system algorithm. This study has demonstrated that the national individual monitoring service can provide a reliable and consistent accurate dosimetry service to its customers.