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[en] Cyclic loading damage in uranium mining is often accompanied by changes in radon exhalation characteristics. Understanding the relationship between rock damage and radon exhalation of uranium ore is therefore important for predicting rock instability and improving monitoring methods to ensure the safety of uranium mines and other underground projects. In this study, we performed constant amplitude cyclic loading and unloading tests on quasi-uranium ore to measure the degree of damage and used the closed chamber method to measure the accumulated radon concentration. The results show a range of damage values between 0.089 and 0.315. The sample with the highest damage value also showed the highest radon exhalation rate of 0.0411 ± 0.00384 Bq m-2 s-1. We use the dissipated energy as a damage variable and find a positive correlation between damage and radon exhalation rate. The damage value was fitted with radon exhalation rates, yielding correlation coefficients of 0.97, and shows an inverted S-shaped trend. The results provide a basis for monitoring rock stability using radon exhalation in future uranium mining operations. (author)
[en] In present study, distribution of 210Po and 210Pb in ground water in uranium mineralized zone of Jaduguda in East Singhbhum region of Jharkhand state, India is evaluated. Activity concentration of 210Po ranges from < 0.08 to 7.41 ± 0.90 mBq L-1 and activity concentration of 210Pb was ranging from 0.76 ± 1.27 to 34.43 ± 3.89 mBq L-1. Comparable results were observed for the samples from upstream and downstream direction with respect to uranium mining and ore processing facilities at Jaduguda reflecting restriction of migration of radionuclides from facilities. Activity concentrations of 210Pb and 210Po observed were below the guidance value of WHO. Average ingestion doses from 210Pb and 210Po in groundwater were calculated to 1.91 ± 1.60 µSv year-1 and 5.75 ± 4.45 µSv year-1respectevely. 210Po was observed to be decreasing with SO42- in ground water indicating possible fixation of 210Po with process involving formation of sulfates. (author)
[en] In this study, the natural radioactivity in pit-water and paddy soil around a decommissioned uranium mine in eastern China was investigated. The gamma radiation absorbed dose rate, annual effective dose equivalent, radium equivalent activity, and radiation hazard index were calculated, and their spatial distribution was presented. The profile distribution of the activity concentrations of radionuclides was also investigated for the possible deposition effect. The radioactivity accumulation in the paddy-soil due to the irrigation was further discussed. It was shown that the accumulation of radioactivity in the paddy soil was limited from the irrigation. (author)
[en] Since the outbreak of the Covid-19 health crisis, Orano has implemented a set of measures to ensure both the health of its employees and the continuity of its customers' businesses, in compliance with the directives of national and international health authorities. At the reporting date of the financial statements, the only significant disruptions related to Covid-19 concern the group's mining activities. The Cigar Lake mine operated by Cameco and the McClean Lake mineral processing plant in Canada, which were stopped for the first time at the end of March with a resumption of production in September, were again phased out at the end of December in view of the development of the local health situation. No contract termination with customers or suppliers was noted due to the pandemic. One-off agreements have been negotiated with certain customers in order to reorganize deliveries beyond 2020 without prejudice to the parties. While the Covid-19 crisis does not affect the value of the group's industrial assets, it has severely disrupted activities, particularly in the Mining and Back End sectors. Despite these uncertainties and thanks in particular to the measures implemented, the group achieved an EBITDA rate of 25.3%, an improvement of +1.5 point compared to 2019. Activity preserved and operational performance improved despite Covid: - Order intake of Euros 1.9 billion and no impact of the crisis on the backlog; - Revenue down by -2.5% (bps) compared to 2019 due to production stoppages and postponements of activities, in connection with the pandemic; - EBITDA of Euros 931 million compared to Euros 900 million in 2019 (rate up to 25.3% compared to 23.8% in 2019). Positive net cash flow and improved liquidity: - Net cash flow of +Euros 144 million (compared to +Euros 219 million in 2019) and maintenance of a coverage rate of 100% of end-of-life cycle liabilities; - Net debt down to Euros 2.15 billion. Net income attributable to owners of the parent impacted by the health crisis: - Adjusted net income attributable to owners of the parent improved at -Euros 91 million (compared with -Euros 145 million in 2019) but impacted by the Covid and an additional end-of-life cycle provision; - Net income attributable to owners of the parent down to -Euros 70 million (compared to +Euros 408 million in 2019) reflecting the same effects and a lower performance of the financial markets in 2020. Financial outlook for 2021: - A recovery in revenue growth; - Consolidation of EBITDA rate between 23% and 26%; - Continuing positive net cash flow.
[en] Epidemiological evidence of lung cancer risk from radon is based mainly on studies of underground miners where occupational exposures were, historically, relatively high in comparison to residential indoor exposure. However, radiation protection measures have caused radon levels in uranium mines to decrease significantly in more recent periods. Miners’ occupational exposure is limited to their working years while they are exposed to environmental radon at home over their entire lifetime. Even during their limited working years, workers spend much more time at home than in workplaces. The biological effect of radon in mines cannot be distinguished from the biological effect of residential radon. Therefore, for an exposure–risk relationship study of former uranium miners, excess radon-induced lung cancer cases should be related to the combined radon exposure cumulated in workplaces and at homes in excess of the radon exposure of the reference population. This is especially important when residential radon levels differ or vary significantly between miners and the reference population over the course of extended follow-up years. This paper reviews some recent studies on former uranium miners, shares what seems controversial to the author and wonders whether lifetime exposure at home to widely varying radon concentrations can actually impact the quality of exposure assessment, and hence impact the results of the exposure–risk relationship.
[en] From 1946 to 1990, more than 400 000 people were employed by Wismut AG, a Soviet/Soviet-German corporation (German abbreviation: SAG/SDAG), in the East German states of Saxony and Thuringia. In the early years in particular, employees were exposed to large amounts of radon and respirable crystalline silica. In a cohort of 35 204 former underground employees of Wismut AG, mortality was analyzed in comparison to the general male population of East Germany, and the pertaining standardized mortality ratios (SMRs) were calculated. 18 510 persons in the study cohort died in the follow-up period 1960–2013. Mortality from lung cancer was 2.36 higher in the study cohort than in the general population (95% confidence interval, [2.28; 2.45]); the associated SMRs rose markedly with increasing radon exposure. Mortality from silicosis and other types of pneumoconiosis was elevated by a factor of 22.62 [21.20; 24.11], and the associated SMRs rose exponentially with increasing exposure to respirable crystalline silica. Mortality from both of these causes was still markedly elevated more than 20 years after Wismut AG had ceased its activities. Mortality from a wide range of other diseases was elevated as well, with the following SMRs: stomach cancer, 1.28 [1.17; 1.40]; liver cancer, 1.34 [1.15; 1.55]; all tumors other than lung cancer, 1.06 [1.02; 1.09]; infections, 1.18 [1.01; 1.38]; cerebrovascular diseases, 1.33 [1.26; 1.41]; and influenza/pneumonia, 1.13 [1.01; 1.27]. Mortality from a small number of other causes was found to be markedly lowered in the study cohort (mental illness, renal diseases, and nervous system diseases). The role of occupational risk factors, lifestyle differences and other reasons for the latter results is unclear. Underground miners employed by Wismut AG displayed marked excess mortality due to silicosis/other pneumoconiosis and lung cancer. The contribution of individual occupational risk factors for these and other causes of death with increased SMR are being further investigated in analyses within the study cohort.