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[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] 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] 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.
[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] 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] 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] Public exposure to external gamma radiation on the waste-rock-covered-8.5-km2-planned final landform from rehabilitation of the Ranger uranium mine was assessed. The average above-background dose rate from external gamma radiation on the planned final landform was determined to be 6.0 x 10-3 mSv d-1. This dose rate was one order of magnitude higher than that for inhalation of radon progeny and two orders of magnitude higher than that for inhalation of radionuclides in dust on the final landform. The above-background annual effective dose to the public from external gamma radiation when the envisioned land use by Aboriginal traditional owners was averaged over the entire 79 km2 Ranger Project Area was about 4.1 x 10-2 mSv. The results of this study may provide general guidance to sites elsewhere on the relative importance of the external gamma pathway and assist in the development or assessment of rehabilitation plans for uranium mining sites. (authors)
[en] This volume is a record of the papers presented at the Fifth International Symposium on the System of Radiological Protection in Adelaide, Australia 2019. This symposium attracted around 400 experts from 40 countries. The structure of the event was different from those in the past, with a focus on three main themes – Mines, Medicine, and Mars – with these and other topics also being covered in poster sessions and other oral sessions organised in conjunction with the 44th Conference of the Australasian Radiation Protection Society.
[en] The mobility and bioavailability of uranium in the environment, e.g. in the near field of a deep geological repository for high-level radioactive waste as well as in former uranium mining sites of Saxony and Thuringia, is controlled by important molecular reactions along the groundwater flow paths. These include both hydrolysis and complexation in aqueous solution as well as reactions at biogeochemical interfaces (sorption, diffusion). Detailed knowledge of the mechanisms taking place is essential to develop reliable long term safety analysis and remediation strategies. The required structural and thermodynamic information can be determined by various spectroscopic methods. The focus of this work is on the characterization of the aquatic speciation of tetravalent uranium present under reducing conditions with inorganic ligands in environmentally relevant micromolar concentrations. For this purpose, the complementary absorption and fluorescence spectroscopic methods UV-VIS, IR, fluorometry and (cryo-) time resolved laser- induced fluorescence spectroscopy (TRLFS) were combined with electrochemical and elemental analytical methods (ICP-MS) as well as with thermodynamic and quantum chemical calculations. In addition to the speciation, this combination allows stoichiometry and molecular structure of the aquatic U(IV) complexes to be characterized as well. To characterize the luminescent properties of U(IV), a laser-based measuring system was successfully set up to study U(IV) systems at room temperature (298.15 K) as well as in the frozen state at liquid nitrogen temperature (77 K). By reproducing previously published data on U(IV) luminescence [1, 2], the suitability of the established TRLFS system could be verified. Static and time-resolved luminescence spectra for the free U 4+ aquo ion could be detected with major peaks at 321, 410, and 523 nm and minor peaks at 337, 395, 447, 489, 511, and 564 nm, as well as an improved fine structure of the luminescence spectra. The associated luminescence lifetimes were determined in perchlorate and chloride with τ = 2.26 ± 0.1 ns at 298.15 K and with τHClO4 = 148.4 ± 6.5 ns and τHCl = 152.6 ± 8.3 ns at 77 K, respectively. Hydrolysis and sulfate complexation were shown to quench the U(IV) luminescence signal and the species UOH3+, USO4 2+ and U(SO4)2 do not luminesce upon excitation with λexc = 245 nm. However, the U(IV) sulfate species can be excited at a λexc higher than 245 nm. Furthermore, the influence of temperature on the absorption and luminescence spectroscopic properties of U(IV) was investigated. An increase in temperature shows a similar effect as an increase in pH since the formation of hydrolysis species is shifted to lower pH at elevated II temperature. Thus, the luminescence intensity decreases with increasing temperature due to formation of not luminescent hydrolysis species combined with increasing dynamic quenching processes. The detection limit for U(IV) fluorescence was improved by two orders of magnitude to 5·10−6 M U(IV) at 25°C/298.15 K and 10−6 M U(IV) at 77 K. The suitability of TRLFS as a sensitive, non-invasive analytical technique for the detection of U(IV) in aqueous solution with environmentally relevant uranium concentrations was verified. However, this method is currently not suitable for speciation studies of U(IV) by reason that the U4+ ion is the only U(IV) species in solution to show a characteristic luminescence signal. Based on its absorption properties, the aqueous speciation of the U(IV) sulfate system in the pH range 0 to 2 could be characterized. Since U(IV) hydrolyzes already at low pH values, a complex multicomponent system consisting of the free U(IV) aquo ion, hydrolysis products and U(IV) sulfate complexes was considered here. Single component spectra for U 4+, UOH3+ , US 2+ and U(So)2 as well as their extinction coefficients of 61.7, 19.2, 47.6 and 40.3 L mol−1 cm−1 were calculated using HypSpec for numerical modeling. Under the experimental conditions, no further hydrolysis and sulfate species were detected. The following complex formation constants for infinite dilution were calculated for the two species USO4 2+ and U(SO4)2 present in aqueous solution and for the hydrolysis species UOH3+: log β⦵101 = 6.9 ± 0.3, log β⦵102 = 11.84 ± 0.5, log β⦵110 = −(0.4 ± 0.1). These were first determined by spectroscopic methods and are in good agreement with literature values from indirect investigation methods or analogies to other tetravalent actinides.[3, 4] Compared with previous experiments, the methodology presented here offers the advantages of direct and non-invasive detection of the species as well as its application to micromolar uranium concentrations. By combining these results with vibration spectroscopic investigations and quantum mechanical calculations, it was additionally possible to show that the species USO4 2+ has a monodentate structure in solution. These results serve as a reference for synthetic and natural systems. In addition, the presented methodology can be applied to other inorganic U(IV) species as well as for other actinides and tetravalent metal ions. As examples of application to real systems, this work photometrical investigates the U(IV) speciation in waters of the Asse II mine and the former uranium mine Königstein. For mine water of the Asse II it was shown that U(IV) remains under reducing conditions stable in solution for several weeks despite a pH of 4.7, since it is stabilized by high ionic strength. The dominant U(IV) species in solution are USO4 2+ and U(SO4)2. For the flooding water from Königstein, after both electrochemical and biochemical reduction of the naturally dissolved uranium, U(IV) in solution could be detected. The dominant U(IV) species in solution is U(SO4)2. Since U(IV) remains stable in solution under the prevailing conditions, remediation strategies based on immobilization through uranium reduction require an increase in pH as well.
[en] Rare earth elements (REE) are used for different applications worldwide in new technologies considered critical and strategic materials in the current globalized scenario and the concern about this resource is constantly gaining attention. The search for new sources of REE is a current issue and researchers are seeking for recycling and recovering REE from secondary sources. Acid mine drainage (AMD) is an important secondary source of REE because this effluent can contain a considerable amount of these precious elements. Furthermore, as AMD is a serious environmental issue and demands treatment before discharge, the union of metal recovery and pollution control is something desirable when sustainability is the goal. There is a closed uranium mine in the state of Minas Gerais-Brazil, with the occurrence of an REE-rich AMD. This peculiar site was selected due to its sui generis geochemical characteristics. In this scenario, this investigation aimed to evaluate the co-precipitation of REE from AMD effluents using oxyhydroxides of Al and Fe as the major co-precipitants. A geochemical model of the AMD system indicates that Ln3+, LnSO4+ and LnF2+ are the dominant REE species at pH 3.5. The neutralization of the AMD with KOH produced an amorphous precipitate containing 14% of REE oxides. The precipitate contains Al13-polymers and accounts for the REE removal when the pH is raised to 8, thus promoting adsorption and entrapment simultaneously. Sequential extraction revealed that 60% of the REE could be leached with the use of acetic acid. In sequence, the role of iron in the coprecipitation of REE and uranium by Fe-Al-precipitates in AMD was studied. It was concluded that the presence and the amount of Fe in the initial solution can positively influence the REE removal efficiency, especially at acidic environments. The influence caused by the addition of Fe was irrelevant when the pH of the AMD was raised to values equal to 7-8. The removal of U was not influenced by the addition of Fe to the AMD before pH neutralization. Sequential extraction results showed that precipitates containing higher amounts of Fe, the REE tend to be less labile. 57Fe Mössbauer spectroscopy studies revealed that the REE can occupy iron sites in the structure of the amorphous precipitates. Subsequently, the influence of soluble Ca and Zn over the co-precipitation of REE by amorphous aluminium precipitates was studied. It was concluded that Ca exerts a negative influence over the co-precipitation as well as over the adsorption of Pr and Eu on amorphous aluminium precipitates. On the other hand, the coprecipitation and adsorption of the elements Nd and Sm did not suffer any influence of the presence of Ca in the solution. Finally, a study concerning the recovery of REE by co-precipitation with Al13-polymers from AMD using Ca(OH)2 for pH control showed that about 90% of the REE present in the AMD sample could be recovered by co-precipitation with amorphous Al-precipitates. The precipitate contains about 7% of REE oxides. The results of the acid-leaching experiment show that about 60%, 65% and 85% of the REE can be extracted from the precipitates using 2 mol L-1 HCl, 1.7 mol L-1 H2SO4 and 2 mol L-1 CH3COOH, respectively. The economic potential of the REE-recovery considering an AMD sample from the studied site was also estimated, revealing the great potential of AMD treatment combined with REE production, in compliance with the United Nations sustainable development goals. (author)