An inter-comparison study was conducted to assess the capability of dosimetry systems of individual monitoring services (IMSs) in Gabon and Ghana to measure personal dose equivalent Hp(10) in photon fields. The performance indicators assessed were the lower limit of detection, linearity and uncertainty in measurement. Monthly and quarterly recording levels were proposed with corresponding values of 0.08 and 0.025 mSv, and 0.05 and 0.15 mSv for the TLD and OSL systems, respectively. The linearity dependence of the dosimetry systems was performed following the requirement given in the Standard IEC 62387 of the International Electrotechnical Commission (IEC). The results obtained for the two systems were satisfactory. The procedure followed for the uncertainty assessment is the one given in the IEC technical report TR62461. The maximum relative overall uncertainties, in absolute value, expressed in terms of Hp(10), for the TL dosimetry system Harshaw 6600, are 44. 35% for true doses below 0.40 mSv and 36.33% for true doses ≥0.40 mSv. For the OSL dosimetry system microStar, the maximum relative overall uncertainties, in absolute value, are 52.17% for true doses below 0.40 mSv and 37.43% for true doses ≥0.40 mSv. These results are in good agreement with the requirements for accuracy of the International Commission on Radiological protection. When expressing the uncertainties in terms of response, comparison with the IAEA requirements for overall accuracy showed that the uncertainty results were also acceptable. The values of Hp(10) directly measured by the two dosimetry systems showed a significant underestimation for the Harshaw 6600 system, and a slight overestimation for the microStar system. After correction for linearity of the measured doses, the two dosimetry systems gave better and comparable results.

In this study, the activity concentrations of radon (²²²Rn), thoron (²²⁰Rn) and thoron progeny were measured simultaneously in Djeno (Pointe-Noire, Republic of Congo) using RADUET detectors to evaluate the air quality and the radiological risks due to the inhalation of these radionuclides. Activity concentrations of radon progeny were calculated from those of radon. Indoor radon, thoron and progenies followed a lognormal distribution ranging between 20 and 40, 6 and 62, 8 and 17.6 and 0.4 and 19.6 Bq m⁻³ for radon, thoron, radon progeny and thoron progeny, respectively. Mean values for radon were lower than the worldwide values estimated by the United Nation Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), which are 40 Bq m⁻³ (arithmetic mean) and 45 Bq m⁻³ (geometric mean). Radon concentrations in the dwellings under study were below the World Health Organization and the International Commission on Radiological Protection recommended reference levels, which are, respectively, 100 and 300 Bq m⁻³. The mean concentration of thoron was twice the world average value of 10 Bq m⁻³ estimated by UNSCEAR. Thoron progeny mean concentration was sharply greater than the typical value (0.3 Bq m⁻³) for indoor atmosphere provided by UNSCEAR. Annual effective dose ranges were 0.40–0.87 mSv (arithmetic mean, 0.57 ± 0.11 mSv) for radon and 0.10–4.14 mSv (arithmetic mean, 0.55 ± 0.77 mSv) for thoron. The mean value for radon was lower than the value (1.15 mSv) estimated by UNSCEAR, while the mean value for thoron was five times higher than the UNSCEAR value (0.10 mSv). The study showed that the use of the typical equilibrium factor value given by UNSCEAR to compute effective dose led to an error above 80%. Finally, the results of this study showed that the excess relative risk of radon-induced cancer was low, below 2% for the population under 55 y. The results presented in the present study prove that the population of Djeno is exposed to a relatively low potential risk of radon- and thoron-induced cancer.

The present work was aimed at measuring indoor radon activity concentrations in dwellings in Mvangan locality, South Cameroon, in order to assess the extent of measures that may be necessary for controlling public indoor radon exposure in this area. Measurements were carried out using passive solid-state nuclear track detectors (RADONAVA Inc., RadTrak2, Sweden) following ISO 11665-4 standard. Radon concentration ranged between 36 ± 20 and 150 ± 30 Bq m⁻³ with arithmetic and geometric means values of 64 ± 25 and 60 ± 1 Bq m⁻³, respectively. These mean values were greater than worldwide values presented by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), which are, respectively, 40 and 30 Bq m₋₃. 96% of dwellings that have radon concentrations below the World Health Organization (WHO) reference level of 100 Bq m⁻³, whereas 4% of dwellings have radon concentrations higher than this level but lower than 300 Bq m⁻³, the International Commission on Radiological Protection (ICRP) reference level. Annual effective doses due to indoor radon ranged between 0.7 and 2.8 mSv y⁻¹ with an arithmetic mean value of 1.2 ± 0.5 mSv y⁻¹. These values were below the lower limit of the ICRP-recommended action level interval 3–10 mSv y⁻¹. It has been observed that annual effective dose received by residents in cement bricks dwellings were not significantly different (P-value = 0.565) than those received by residents in mud dwellings in Mvangan locality. The mean number of persons expected to be diagnosed with or die from cancer (solid cancers and leukemia) were 162 ± 48 (61 ± 25 for males and 101 ± 41 for females) and 82 ± 24 (33 ± 13 for males and 49 ± 20 for females), respectively. The results obtained in this study prove that the populations of Mvangan locality are exposed to a relatively low potential risk of cancer incidence and mortality.

This paper describes the essential of the “Guide to the expression of Uncertainty in Measurement” Framework (GUMF) Method and Monte Carlo Method (MCM) for propagating uncertainties, with an application to Gabon results obtained during the 2018 International Atomic Energy Agency (IAEA) regional intercomparison exercise. The work has shown that the output quantity H_p (10) follows a lognormal distribution. The study has also shown that although the normal distribution does not best approximate the distribution of the output quantity H_p (10), it has been observed that its estimate, the associated standard uncertainty and the coverage interval determined by GUMF and MCM were close, meaning that the application of the GUMF could still be seen as valid. Finally, the results obtained by the two methods are in agreement with International Commission on Radiological Protection and IAEA requirements for overall accuracy.

The present study aimed at to establish typical dose reference level (DRL) values for adult patients undergoing computed tomography (CT) examinations in three hospitals in Brazzaville, Congo Republic. The examinations considered were head, chest, abdomen-pelvis, chest-abdomen-pelvis and lumbar spine CT scans. For each examination, the median of the distribution for the volume CT dose index (CTDIvol) and dose-length product (DLP) were determined. The median values were considered as the typical DRL values. Hypothesis testing was also carried out to statistically compare the mean values obtained for each participating CT facility. In the case of head scan, the typical values proposed in the present study in terms of CTDIvol and DLP were 15–48% and 28–60% lower than the DRL values reported in the literature, respectively. In the case of lumbar spine, the typical value determined in this study in terms of DLP was 48–70% greater than the DRL values provided in the literature. The typical values proposed for chest, abdomen-pelvis and chest-abdomen-pelvis were within the DRL values reported in the literature. It is possible that the adoption of the typical values proposed in the present study will help in reducing the dose received by adult patients undergoing CT examination in Congo Republic.