No abstract

The energy response of three types of LiF:Mg, Ti dosemeter to standard x-ray calibration qualities and diagnostic x-rays has been studied. The aim of this study was to investigate whether the inherent mismatch between these qualities compromises the accuracy of the evaluated occupational doses in diagnostic x-ray facilities. A sample of 10 dosemeters of each type was exposed to air kerma of 5 mGy from each of six ISO 4037 (series 407) x-ray radiation protection calibration qualities (2.7 mm Al to 2.45 mm Cu HVL (half-value layer)) and 11 diagnostic x-ray qualities (1.45-4.9 mm Al HVL). The results show that the TLD energy response to ISO 4037 and diagnostic x-rays as normalised to 137Cs ranged from 1.1 to 1.44 and 0.57 to 1.54 respectively. This implies an energy response range from -52 to +7% for diagnostic x-rays relative to ISO 4037 x-rays, hence a maximum over-response of 52%. Despite this discrepancy, the results show that the mismatch between calibration and diagnostic x-ray beams does not significantly compromise the accuracy of individual doses in diagnostic x-ray facilities.

Data on occupational radiation exposure using the thermoluminescence dosimetry methodology in Tanzania for the years 1996-2010 are analysed and discussed. The results of the analysis indicate that over 80 % of the total collective dose was from diagnostic radiology. In addition, <1 % of workers received annual individual doses above 5 mSv, and there were no doses that exceeded the recommended limit of 20 mSv y(-1), except for one incidence in non-destructive testing. Furthermore, the trends in occupational exposure remained approximately constant and largely within the ranges of average doses in the literature. The status and trends in occupational exposure demonstrate that radiation protection conditions at the majority of workplace were adequate. Despite that, further optimisation is necessary due to large variations observed in the maximum individual doses over three 5-y sub-periods.

The objectives of this paper were to evaluate the occupational radiation exposure data from 2011 to 2017 and to compare the results with status in 1996–2010 periods. The evaluation was performed in terms of annual collective effective dose, the average annual effective dose, the individual dose distribution ratio and the annual collective effective dose distribution ratio. Irrespective of work category, the results indicate that the average effective dose ranged from 0.64 to 1.55 mSv and broadly comparable to data in the previous analysis. Over seven year period, the maximum annual individual dose was 4 mSv and therefore below the dose limit of 20 mSv y−1. The impact of radiological practice on the exposed population was &lt;1.1 person.Sv. The results demonstrate satisfactory radiation protection conditions at workplaces, a situation which is mainly explained by the existing effective regulatory enforcement and improved workers’ awareness.