A primeira mineração de urânio do Brasil está localizada nas dependências da Unidade de Tratamento de Minérios das Indústrias Nucleares do Brasil. Atualmente, essa área mineradora encontra-se em fase de descomissionamento e a drenagem ácida de mina constitui o principal passivo ambiental, devido ao volume de efluentes radioativos gerados, os quais após tratamento são lançados na represa das Antas (RA). Os resultados indicaram que amostras do efluente in natura e tratado apresentaram maiores concentrações de espécies químicas, sendo consideradas agudamente tóxicas para os dafinídeos, indicando que que o sistema de tratamento realizado pela mineradora foi impróprio e ineficiente. Valores de dureza extremamente elevados indicaram efeito protetor para os dafinídeos, quando maiores concentrações de metais tais como F-, U, Mn e Al foram registradas. O metal Mn apresentou potencial de causar toxicidade para C. silvestrii, CE50 (5,93 mg L-1). Para U, mudanças no pH nos ensaios de D.magna, estiveram associadas a alterações nas concentrações das espécies potencialmente tóxicas UO22+ e UO2OH+. A espécie nativa C. silvestrii mostrou ser muito mais sensível a U, quando comparada a D. magna, de acordo com a CE50 (0,07 e 0,56 mg L-1, respectivamente). / The first uranium mining in Brazil is located on the Ore Treatment Unit of Nuclear Industries of Brazil. Currently, this mining area is in process of decommissioning and the acid mine drainage is the main environmental liability due to the volume of radioactive effluents produced, which after treatment are discharged into the Antas reservoir (AR). The results indicated that samples of the in natura and treated effluent presented higher concentrations of chemical species, being considered acutely toxic to the daphnids, indicating that the treatment carried out by the mining company (UTM/INB) was improper and inefficient. Extremely high hardness values indicated protective effect for the daphnids, when higher concentrations of metals such as F-, U, Mn and Al were recorded. The Mn metal presented potential toxicity for C. silvestrii, EC50 (5.93 mg L-1). For U, changes in pH in the D.magna assays were associated with changes in concentrations of the toxic potentially species UO22+ and UO2OH+. The native species C. silvestrii showed to be much more sensitive to U, than D. magna, according to EC50 (0.07 and 0.56 mg L-1, respectively).

Sediment quality guidelines (SQGs) or values (SQVs) are used to assess the potential risk of contaminants in sediment to aquatic organisms, specifically benthic invertebrates. The objectives of this research were to evaluate SQGs derived specifically for use by the uranium industry in Canada, propose alternative SQVs for use at uranium operations in northern Saskatchewan using a novel approach, and investigate the potentially bioavailable fractions of metals in sediment which could become an alternative measurement to the typically used total metal concentrations. The screening-level concentration (SLC) approach has been used in Ontario, Canada, to derive lowest effect levels (LELs) and severe effect levels for use as SQGs. This approach was adopted by the Canadian Nuclear Safety Commission (CNSC) to set guidelines for metals (As, Cr, Cu, Pb, Mo, Ni, Se, U, and V) and radionuclides (Ra-226, Pb-210, and Po-210) in sediment at northern Saskatchewan uranium mining and milling operations. The SLC approach is based on total metal and radionuclide concentrations in sediment, and corresponding benthic invertebrate community composition data for a specific sampling site. In this study, sediment chemistry (total metals and radionuclides) and benthic community data from northern Saskatchewan uranium operations were compiled and examined. Results indicated that the CNSC-derived SQGs had limited relationships to observed effects, or lack thereof, on benthic invertebrate communities near uranium operations in Saskatchewan. On a general basis, the correct alignment of at least one LEL exceedence at an effect site was observed 95% of the time, but on an element-specific basis many of the elements had concentrations at effect sites below their LELs. Furthermore, concentrations of the evaluated elements exceeded at least one LEL at 60% of the no-effect sites. The high number of exceedences of LELs at reference and no-effect sites (false-positives) calls to question the appropriateness of the CNSC-derived SQGs. To address the deficiencies of the SLC approach, a new approach was developed to derive alternative metal SQVs for the uranium industry in northern Saskatchewan that was based on the use of reference and no-effect site field data. Three different sets of NE values were derived using combinations of benthic invertebrate community effect criteria (abundance, richness, evenness, Bray-Curtis index). Additionally, reference (REF) values were derived based solely on sediment metal concentrations from reference sites. In general, NE values derived using abundance, richness, and evenness (NE1 and NE2 values) were found to be higher than the NE values derived using all four metrics (NE3 values). Derived NE values for Cr, Cu, Pb, and V did not change with the incorporation of additional effects criteria due to a lack of influence from the uranium operations on these metal concentrations (i.e., they were generally present at or near background levels). However, a gradient of exposure concentrations was apparent for As, Mo, Ni, Se, and U in sediment which allowed for acceptable exposure levels of these metals in sediment to be defined. The findings from this assessment proposed a set of new, alternate SQVs for use at the uranium industry in northern Saskatchewan. Often, only total metals concentrations are measured in the evaluation of contaminated sediment. However, this measure may over-estimate metal exposure to benthic invertebrates. Using sediment cores collected from near the Rabbit Lake and Key Lake uranium operations, along with a series of mixed-sediments (contaminated and reference sediment), metal bioaccumulation experiments using Chironomus dilutus were conducted in the laboratory. Metal concentrations in extracts from single extractions with either potassium phosphate or hydrochloric acid on wet and dried sediment, pore-water, and whole-sediment were used to evaluate metal bioaccumulation in test organisms. Depending on the metal, pore-water isolated using peepers generally exhibited the best relationship with tissue metal concentrations. Based on this finding, it is suggested that pore-water sampling using peepers (an in-situ dialysis device) be added to environmental sampling programs at Saskatchewan uranium operations so that sediment metal availability to benthic invertebrates can be better assessed. With the eventual development of a larger pore-water metals dataset, SQGs based on pore-water metals concentrations could likely be derived as an alternative to existing SQGs based on total metal concentrations in sediment.

Sediment quality guidelines (SQGs) or values (SQVs) are used to assess the potential risk of contaminants in sediment to aquatic organisms, specifically benthic invertebrates. The objectives of this research were to evaluate SQGs derived specifically for use by the uranium industry in Canada, propose alternative SQVs for use at uranium operations in northern Saskatchewan using a novel approach, and investigate the potentially bioavailable fractions of metals in sediment which could become an alternative measurement to the typically used total metal concentrations. The screening-level concentration (SLC) approach has been used in Ontario, Canada, to derive lowest effect levels (LELs) and severe effect levels for use as SQGs. This approach was adopted by the Canadian Nuclear Safety Commission (CNSC) to set guidelines for metals (As, Cr, Cu, Pb, Mo, Ni, Se, U, and V) and radionuclides (Ra-226, Pb-210, and Po-210) in sediment at northern Saskatchewan uranium mining and milling operations. The SLC approach is based on total metal and radionuclide concentrations in sediment, and corresponding benthic invertebrate community composition data for a specific sampling site. In this study, sediment chemistry (total metals and radionuclides) and benthic community data from northern Saskatchewan uranium operations were compiled and examined. Results indicated that the CNSC-derived SQGs had limited relationships to observed effects, or lack thereof, on benthic invertebrate communities near uranium operations in Saskatchewan. On a general basis, the correct alignment of at least one LEL exceedence at an effect site was observed 95% of the time, but on an element-specific basis many of the elements had concentrations at effect sites below their LELs. Furthermore, concentrations of the evaluated elements exceeded at least one LEL at 60% of the no-effect sites. The high number of exceedences of LELs at reference and no-effect sites (false-positives) calls to question the appropriateness of the CNSC-derived SQGs. To address the deficiencies of the SLC approach, a new approach was developed to derive alternative metal SQVs for the uranium industry in northern Saskatchewan that was based on the use of reference and no-effect site field data. Three different sets of NE values were derived using combinations of benthic invertebrate community effect criteria (abundance, richness, evenness, Bray-Curtis index). Additionally, reference (REF) values were derived based solely on sediment metal concentrations from reference sites. In general, NE values derived using abundance, richness, and evenness (NE1 and NE2 values) were found to be higher than the NE values derived using all four metrics (NE3 values). Derived NE values for Cr, Cu, Pb, and V did not change with the incorporation of additional effects criteria due to a lack of influence from the uranium operations on these metal concentrations (i.e., they were generally present at or near background levels). However, a gradient of exposure concentrations was apparent for As, Mo, Ni, Se, and U in sediment which allowed for acceptable exposure levels of these metals in sediment to be defined. The findings from this assessment proposed a set of new, alternate SQVs for use at the uranium industry in northern Saskatchewan. Often, only total metals concentrations are measured in the evaluation of contaminated sediment. However, this measure may over-estimate metal exposure to benthic invertebrates. Using sediment cores collected from near the Rabbit Lake and Key Lake uranium operations, along with a series of mixed-sediments (contaminated and reference sediment), metal bioaccumulation experiments using Chironomus dilutus were conducted in the laboratory. Metal concentrations in extracts from single extractions with either potassium phosphate or hydrochloric acid on wet and dried sediment, pore-water, and whole-sediment were used to evaluate metal bioaccumulation in test organisms. Depending on the metal, pore-water isolated using peepers generally exhibited the best relationship with tissue metal concentrations. Based on this finding, it is suggested that pore-water sampling using peepers (an in-situ dialysis device) be added to environmental sampling programs at Saskatchewan uranium operations so that sediment metal availability to benthic invertebrates can be better assessed. With the eventual development of a larger pore-water metals dataset, SQGs based on pore-water metals concentrations could likely be derived as an alternative to existing SQGs based on total metal concentrations in sediment.

Made available in DSpace on 2014-06-11T19:26:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-01-23Bitstream added on 2014-06-13T19:54:20Z : No. of bitstreams: 1 barros_df_me_rcla.pdf: 4822584 bytes, checksum: fd3df8fb03e1be9a4566668c777c0a5a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho mostra eventos que influenciaram a indústria mundial do urânio tomando como países selecionados a Alemanha, a Austrália, o Canadá, os Estados Unidos da América, a França e o Brasil. Os eventos destacados para cada país são: a implantação das agências reguladoras ao longo dos anos; a evolução das políticas de proteção do público e do meio ambiente contra os possíveis danos da radiação ionizante. Um levantamento histórico desses fatos foi realizado e é organizado em ordem cronológica, dividindo as legislações de cada país em seus âmbitos: federal, estadual e ambiental, bem como é tratado da produção de urânio de cada nação. Deste modo é apresentada a evolução das legislações no campo da indústria de urânio, com o propósito de demonstrar como a legislação sobre esta indústria e a agência reguladora nacional podem ser aperfeiçoadas e melhoradas. / This study shows events that have influenced the worldwide uranium industry, taking into account the countries: Germany, Australia, Canada, the United States of America, France and Brazil. The highlighted events for every country will be: the installations of the regulatory agencies along the years, the evolution of the political concepts concerning the public health and the environment against the possible effects of the ionizing radiation. A historical study of these facts was accomplished and will be set in chronological order, so that dividing the legislation of every country in its federal, state and environmental scopes. Uranium production for every nation is also treated herein. Therefore the legislation evolution in the uranium industry field is shown with the aim to demonstrate how the legislation of this industry and the Brazilian regulatory agency can be improved.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The Uraniferous Province of Lagoa Real, in the region of Caetité, located in midwest Bahia State, is considered the most important uraniferous reserve of Brazil. Because it is a uranium mining region, it is important to be evaluated and monitored in order to obtain information on the chemical composition and concentration of radionuclides in water and soil. In this study we determined the specific activity of some radionuclides in soil and water samples collected in February 2014, when high rainfall in the region. The concentration of the activities of radionuclides 226,228Ra and 234,238U in water samples and radionuclides 226Ra, 232Th and 40K in soil samples were found by different techniques of nuclear spectrometry. The water samples showed higher specific activity (134 + 4) mBq / L for 226Ra and (208 + 9) mBq / L for 228Ra. Concerning the isotopes of uranium, the highest activity in the water was (172 + 10) mBq / L for 238U and (447 + 20) mBq / L for 234U. In the soil samples was noted that especially the 40K was most active. The highest value obtained for this radioactive nuclide was (155 + 11) .10 Bq / kg. In samples sand beaches of Rio de Janeiro and Aracaju, used as a reference, the highest activity was the 232Th with (36.4 + 6.1) Bq / kg, and for the 40K all showed a specific activity of < 50 Bq / kg. The soil samples represented very low specific activity for radionuclides investigated, compared to the values established in the Brazilian criteria for exclusion, exemption and waiver as radiation protection requirement. The effective doses were calculated from the activity concentrations of radioactive nuclides in water and their dose coefficients. Two samples exceeded the limits recommended by the WHO that is 100 mSv / a, (144.2 mSv / a) and (102.2 mSv / a), but both are not ingested by the population. The most effective dose calculated for water samples ingested by the population was 58.6 mSv / a, value within the recommended limit. From the data obtained, it can be concluded that the samples did not indicate a high concentration as TENORM and that there seems to be contamination of Caetité region due handling ore in the region. The presence of radionuclides in the samples is due to the nature of the soil region and the operation of uranium. / A Província Uranífera de Lagoa Real, na região de Caetité e Lagoa Real, situado no centro sul da Bahia, atualmente é considerada a mais importante reserva uranífera do Brasil. Por se tratar de uma região de exploração do minério de urânio, é importante ser avaliada e monitorada para que se obtenham informações da composição química e concentração de radionuclídeos na água e no solo. Neste trabalho determinou-se a atividade específica de alguns radionuclídeos em amostras de águas e solos coletadas em fevereiro de 2014, época de alto índice pluviométrico na região. A concentração das atividades dos radionuclídeos 226,228Ra e 234,238U em amostras de água e dos radionuclídeos 226Ra, 232Th e 40K em amostras de solos foram encontrados por diferentes técnicas de espectrometria nuclear. A amostra de água com maior atividade específica apresentou (134 + 4) mBq/L para 226Ra e (208 + 9) mBq/L para 228Ra. Tratando-se isótopos de urânio, a maior atividade na água foi de (172 + 10) mBq/L para o 238U e de (447 + 20) mBq/L para 234U. Nas amostras de solo foi notado que especialmente o 40K apresentou maior atividade. O maior valor obtido para este nuclídeo radioativo foi (155 + 11).10 Bq/kg. Em amostras de areia de praias do Rio de Janeiro e de Aracaju, usadas como referência, a maior atividade foi do 232Th com (36,4 + 6,1) Bq/kg, sendo que para o 40K todas apresentaram uma atividade específica de < 50 Bq/kg. As amostras de solos representaram muito baixa atividade específica para os radionuclídeos investigados, comparadas aos valores estabelecidos nos critérios brasileiros de exclusão, isenção e dispensa como requisito de proteção radiológica. As doses efetivas foram calculadas a partir das concentrações de atividade dos nuclídeos radioativos encontrados na água e de seus coeficientes de dose. Duas amostras excederam os limites recomendados pela OMS que é de 100 mSv/a, (144,2 mSv/a) e (102,2 mSv/a), mas ambas não são ingeridas pela população. A maior dose efetiva calculada para amostras de água ingeridas pela população foi 58,6 mSv/a, valor dentro do limite recomendado. A partir dos dados obtidos, pode-se concluir que as amostras não indicaram uma concentração elevada como TENORM e que não parece haver contaminação da região de Caetité devido movimentação de minério na região. A presença de radionuclídeos nas amostras de solo se deve à natureza do solo da região e não à exploração de urânio.

The impacts of mining are easily observable in the way they alter the terrain of landscapes, displace animals, and increase waste accumulation in an area. An unobservable impact and one that lasts a long time is by radioactive exposure in the environment. Specifically, this is a risk at uranium (U) mine sites which are expanding in number to accommodate the world’s growing energy needs, and even to accommodate weapons manufacturing. This paper analyses the impacts of an abandoned uranium mine on the local environment through measurements of Uranium concentration in soil, plants, and rocks. Transect sampling was used to collect 22 soil samples and 17 plant samples between 5 and 100m of the mine shaft. Uranium concentrations in soil and plant samples, digested with nitric acid, were measured with an Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES), and an X-ray Powder Diffraction (XRD) analysis was used to find the mineral contents of the rock samples. Satellite positions were associated with each sample, which allowed an effective spatial analysis of the Uranium concentration values. U values in soil ranged from 0 to 5.291ppm, with mean concentrations of 0.710 ppm, and U values in plants ranged from 0.0323 to 0.1121ppm with mean concentrations of 0.0558 ppm. A paired t-test determined that there was no spatial autocorrelation in U concentrations of plants and adjacent soils. The highest U concentration was found closest to the mine, peaking at ~7.3 meters from the mine, and low spatial variability occurs in U concentrations at greater than 10 meters from the mine. In comparison with other mines internationally, U concentrations at this study site were low, which may be indicative of a small operating mine, efficient clean-up, and transport mechanisms of U in desert environments.

Im Abstrom von Uranbergbauobjekten (Sachsen, Deutschland) wurden Uran, Radium-226 und Arsen in unterschiedlichen Feuchtgebieten untersucht. Dabei wurden Wasser (vor¬wiegend neutrale bis leicht basische pH-Werte), Sedimente und im Wasser befindlicher Bestandesabfall (CPOM) beprobt. Zur Klärung der Genese der Urangehalte im Sediment erfolgten Untersuchungen an Pb-Isotopen. Sie zeigen u. a., dass das Uran in den obersten Zentimetern des Sediments (organische Auflage) aus der wässrigen Phase und nicht von ca. 300 Millionen Jahre alten Erzteilchen stammt. Für die Verlagerung von Radionukliden und Arsen aus dem Wasserkörper in das Sediment wird ein neuer Weg aufgezeigt. Eine Fixierung dieser Stoffe an Bestandesabfällen (plant litter) ist möglich. Allochthoner Bestandesabfall (Blätter, Früchte, Zweige von Alnus spec. und Quercus spec.) weist nach Kontakt mit kontaminiertem Wasser (ca. 100 - 300 µgU L-1) Urangehalte von 50 - 2.000 µgU g-1 auf. Im Vergleich zu Uran sind Ra-226 und Arsen labiler am Bestandesabfall gebunden. Für die Genese der Gehalte in den subhydrischen Auflagen sind die Herkunft des (autochthonen bzw. allochthonen) Bestandesabfalls und der Abbau eine entscheidende Rolle. Sedimente aus leicht abbaubaren Bestandesabfällen (z.B. Lemna spec., Algen) weisen im Vergleich mit allochthonen Bestandesabfällen (von Bäumen) deutlich geringere Urangehalte auf. Exemplarisch wurde für einen aus allochthonen Bestandesabfällen bestehenden Sedimentkern mittels Cs-137-Bestimmung eine maximale Uranfestlegung von 1 – 2 g m-² a-1 ermittelt. Neben allochthonem Bestandesabfall führen Eisen- und Manganhydroxide, die unmittelbar an den Sickerwasseraustrittstellen ausfallen, bei relativ geringen Arsen- und Radiumkon¬zentrationen im Wasser zu hohen Arsen- bzw. Radiumgehalten im Sediment (As ≤ 5 mg g-1; Ra-226 ≤ 25 Bq g-1). Unter reduktiven Bedingungen werden Ra-226 und Arsen jedoch leicht freigesetzt. Ausgehend von den Untersuchungsergebnissen wird eine mögliche Anordnung für eine naturnahe passive Sickerwasserbehandlung vorgeschlagen.

Este trabalho teve como objetivo avaliar o impacto radiológico atmosférico da Unidade de Concentrado de Urânio URA, Caetité, BA, através da modelagem da dispersão de radionuclídeos e a estimativa da dose efetiva anual (em mSv.ano-1). Para tal, utilizou-se o programa MILDOS-AREA que foi desenvolvido pelo Argonne National Laboratory (ANL) em conjunto com a U.S. Nuclear Regulatory Commission (USNRC), para avaliar impacto radiológico ambiental atmosférico nas instalações de mineração e beneficiamento de urânio. O incremento de dose efetiva anual para três grupos críticos hipotéticos e oito grupos populacionais reais foi estimado com base na medida de fluxos de radônio e na estimativa das concentrações de radionuclídeos em particulados no ar dos principais termos fontes da URA (cava da mina, depósito de estéril e britador). Paralelamente, as medidas de concentração de radônio e taxa de kerma no ar, reportadas nos relatórios dos programas de monitoração ambiental pré-operacional (PMAPO) e operacional (PMAO) da URA, foram avaliadas. Os valores de dose efetiva anual estimados para os grupos críticos hipotéticos variaram de 1,78E-02 a 2,10E-02 mSv.ano-1, enquanto que para os grupos populacionais, variaram de 7,49E-05 a 1,56E-02 mSv.ano-1. A maior contribuição para o incremento da dose foi devida a inalação do radônio, sendo responsável por quase a totalidade da dose efetiva anual estimada. A média da concentração de atividade de radônio no entorno da URA foi 137,21 Bq m-3 e não sendo observada diferenças significativas entre as concentrações de radônio reportadas nos programas de monitoramento ambiental pré-operacional (valores de background) e operacional. Os valores médios de taxa de kerma no ar no entorno da URA foram de 0,136 &#956;Gy h-1. No entanto, em todos os pontos de monitoramento, os valores reportados no programa operacional foram inferiores aos valores reportados no programa pré-operacional (background), o que sugere problemas de medidas ou de coleta de dados durante a realização deste programa. O operador da URA utilizou para avaliação de impacto radiológico atmosférico, resultados apresentados em seus relatórios finais de análise de segurança (RFAS), um modelo próprio de simulação de dispersão, denominado Impacto Ambiental Radiológico (IAR7). Uma comparação entre o MILDOS-AREA e o IAR7, utilizando os mesmos parâmetros de entrada reportados no RFAS sugere que o IAR7 subestimou as concentrações de radônio no ar para os grupos críticos hipotéticos. Os resultados de simulação com o MILDOS-AREA mostram que as doses efetivas estimadas para os grupos críticos hipotéticos são inferiores a 0,3 mSv.ano-1 que é a restrição de dose estabelecida pela Comissão Nacional de Energia Nuclear. Recomenda-se que o código MILDOS-AREA seja utilizado no Brasil, para fins de licenciamento e controle, tendo em vista que o mesmo é um código validado e já utilizado em outros países para avaliar impacto radiológico ambiental atmosférico em instalações de mineração e beneficiamento de urânio / This work aimed to evaluate the atmospheric radiological impact of the Uranium Concentration Unit - URA, Caetité, BA, by modeling the dispersion of radionuclides and estimating the annual effective dose (in mSv.year-1). For this purpose, we used the MILDOS-AREA program that was developed by Argonne National Laboratory (ANL) jointly with the US Nuclear Regulatory Commission (USNRC) specifically to evaluate the atmospheric radiological impact of uranium mining and processing facilities. Taking into account estimative of particulate radionuclide concentration and radon flux measurements performed in the main source-terms of URA (open pit, heap leaching and tailing deposit), we estimated the increase of annual effective dose for three hypothetical critical groups and eight population groups. In addition, we evaluated results of radon activity concentration and kerma rate concentration in air reported in the pre-operational environmental monitoring program (PMAPO) and in the operational environmental monitoring programs (PMAO) from URA. The estimated annual effective dose to the hypothetical critical groups ranged from 1,78E-02 a 2,10E-02 mSv.year-1. For real populations, effective doses ranged from 7,49E-05 to 1,56E-02 mSv.year-1. The largest contribution to the total dose was due to inhalation of radon, accounting for almost the entire estimated annual effective dose. The average radon activity concentration in the vicinity of the URA was 137.21 Bq m-3 and there was no apparent difference between the radon concentrations reported in the pre-operational environmental monitoring program (background values) and post-operational. The average values of kerma rate in air surrounding the URA were 0.136 &#956;Gy h-1. However, for all the monitoring points, the values reported in operational environmental monitoring program were lower than the values reported in pre-operational environmental monitoring program (background), suggesting measurements or data collection problems during the pre-operational program. The miner industry used in their final report of safety analysis (RFAS), a proper dispersion model simulation, called Environmental Impact Radiological (IAR7). A comparison between the MILDOS-AREA and the IAR7 using the same input parameters in IAR7 suggested that IAR7 underestimated the radon concentrations in the air to the hypothetical critical groups. In conclusion, MILDOS-AREA simulation showed that the estimated effective doses for the hypothetical critical groups are less than 0.3 mSv.year-1, which is the operational dose limit to the public established by the National Nuclear Energy Commission. It is recommended that the MILDOS-AREA code should be used in Brazil, considering that it is a validated code and already used in other countries to assess atmospheric radiological impact on mining and uranium processing facilities

Este trabalho teve como objetivo avaliar o impacto radiológico atmosférico da Unidade de Concentrado de Urânio URA, Caetité, BA, através da modelagem da dispersão de radionuclídeos e a estimativa da dose efetiva anual (em mSv.ano-1). Para tal, utilizou-se o programa MILDOS-AREA que foi desenvolvido pelo Argonne National Laboratory (ANL) em conjunto com a U.S. Nuclear Regulatory Commission (USNRC), para avaliar impacto radiológico ambiental atmosférico nas instalações de mineração e beneficiamento de urânio. O incremento de dose efetiva anual para três grupos críticos hipotéticos e oito grupos populacionais reais foi estimado com base na medida de fluxos de radônio e na estimativa das concentrações de radionuclídeos em particulados no ar dos principais termos fontes da URA (cava da mina, depósito de estéril e britador). Paralelamente, as medidas de concentração de radônio e taxa de kerma no ar, reportadas nos relatórios dos programas de monitoração ambiental pré-operacional (PMAPO) e operacional (PMAO) da URA, foram avaliadas. Os valores de dose efetiva anual estimados para os grupos críticos hipotéticos variaram de 1,78E-02 a 2,10E-02 mSv.ano-1, enquanto que para os grupos populacionais, variaram de 7,49E-05 a 1,56E-02 mSv.ano-1. A maior contribuição para o incremento da dose foi devida a inalação do radônio, sendo responsável por quase a totalidade da dose efetiva anual estimada. A média da concentração de atividade de radônio no entorno da URA foi 137,21 Bq m-3 e não sendo observada diferenças significativas entre as concentrações de radônio reportadas nos programas de monitoramento ambiental pré-operacional (valores de background) e operacional. Os valores médios de taxa de kerma no ar no entorno da URA foram de 0,136 &#956;Gy h-1. No entanto, em todos os pontos de monitoramento, os valores reportados no programa operacional foram inferiores aos valores reportados no programa pré-operacional (background), o que sugere problemas de medidas ou de coleta de dados durante a realização deste programa. O operador da URA utilizou para avaliação de impacto radiológico atmosférico, resultados apresentados em seus relatórios finais de análise de segurança (RFAS), um modelo próprio de simulação de dispersão, denominado Impacto Ambiental Radiológico (IAR7). Uma comparação entre o MILDOS-AREA e o IAR7, utilizando os mesmos parâmetros de entrada reportados no RFAS sugere que o IAR7 subestimou as concentrações de radônio no ar para os grupos críticos hipotéticos. Os resultados de simulação com o MILDOS-AREA mostram que as doses efetivas estimadas para os grupos críticos hipotéticos são inferiores a 0,3 mSv.ano-1 que é a restrição de dose estabelecida pela Comissão Nacional de Energia Nuclear. Recomenda-se que o código MILDOS-AREA seja utilizado no Brasil, para fins de licenciamento e controle, tendo em vista que o mesmo é um código validado e já utilizado em outros países para avaliar impacto radiológico ambiental atmosférico em instalações de mineração e beneficiamento de urânio / This work aimed to evaluate the atmospheric radiological impact of the Uranium Concentration Unit - URA, Caetité, BA, by modeling the dispersion of radionuclides and estimating the annual effective dose (in mSv.year-1). For this purpose, we used the MILDOS-AREA program that was developed by Argonne National Laboratory (ANL) jointly with the US Nuclear Regulatory Commission (USNRC) specifically to evaluate the atmospheric radiological impact of uranium mining and processing facilities. Taking into account estimative of particulate radionuclide concentration and radon flux measurements performed in the main source-terms of URA (open pit, heap leaching and tailing deposit), we estimated the increase of annual effective dose for three hypothetical critical groups and eight population groups. In addition, we evaluated results of radon activity concentration and kerma rate concentration in air reported in the pre-operational environmental monitoring program (PMAPO) and in the operational environmental monitoring programs (PMAO) from URA. The estimated annual effective dose to the hypothetical critical groups ranged from 1,78E-02 a 2,10E-02 mSv.year-1. For real populations, effective doses ranged from 7,49E-05 to 1,56E-02 mSv.year-1. The largest contribution to the total dose was due to inhalation of radon, accounting for almost the entire estimated annual effective dose. The average radon activity concentration in the vicinity of the URA was 137.21 Bq m-3 and there was no apparent difference between the radon concentrations reported in the pre-operational environmental monitoring program (background values) and post-operational. The average values of kerma rate in air surrounding the URA were 0.136 &#956;Gy h-1. However, for all the monitoring points, the values reported in operational environmental monitoring program were lower than the values reported in pre-operational environmental monitoring program (background), suggesting measurements or data collection problems during the pre-operational program. The miner industry used in their final report of safety analysis (RFAS), a proper dispersion model simulation, called Environmental Impact Radiological (IAR7). A comparison between the MILDOS-AREA and the IAR7 using the same input parameters in IAR7 suggested that IAR7 underestimated the radon concentrations in the air to the hypothetical critical groups. In conclusion, MILDOS-AREA simulation showed that the estimated effective doses for the hypothetical critical groups are less than 0.3 mSv.year-1, which is the operational dose limit to the public established by the National Nuclear Energy Commission. It is recommended that the MILDOS-AREA code should be used in Brazil, considering that it is a validated code and already used in other countries to assess atmospheric radiological impact on mining and uranium processing facilities

Im Abstrom von Uranbergbauobjekten (Sachsen, Deutschland) wurden Uran, Radium-226 und Arsen in unterschiedlichen Feuchtgebieten untersucht. Dabei wurden Wasser (vor¬wiegend neutrale bis leicht basische pH-Werte), Sedimente und im Wasser befindlicher Bestandesabfall (CPOM) beprobt. Zur Klärung der Genese der Urangehalte im Sediment erfolgten Untersuchungen an Pb-Isotopen. Sie zeigen u. a., dass das Uran in den obersten Zentimetern des Sediments (organische Auflage) aus der wässrigen Phase und nicht von ca. 300 Millionen Jahre alten Erzteilchen stammt. Für die Verlagerung von Radionukliden und Arsen aus dem Wasserkörper in das Sediment wird ein neuer Weg aufgezeigt. Eine Fixierung dieser Stoffe an Bestandesabfällen (plant litter) ist möglich. Allochthoner Bestandesabfall (Blätter, Früchte, Zweige von Alnus spec. und Quercus spec.) weist nach Kontakt mit kontaminiertem Wasser (ca. 100 - 300 µgU L-1) Urangehalte von 50 - 2.000 µgU g-1 auf. Im Vergleich zu Uran sind Ra-226 und Arsen labiler am Bestandesabfall gebunden. Für die Genese der Gehalte in den subhydrischen Auflagen sind die Herkunft des (autochthonen bzw. allochthonen) Bestandesabfalls und der Abbau eine entscheidende Rolle. Sedimente aus leicht abbaubaren Bestandesabfällen (z.B. Lemna spec., Algen) weisen im Vergleich mit allochthonen Bestandesabfällen (von Bäumen) deutlich geringere Urangehalte auf. Exemplarisch wurde für einen aus allochthonen Bestandesabfällen bestehenden Sedimentkern mittels Cs-137-Bestimmung eine maximale Uranfestlegung von 1 – 2 g m-² a-1 ermittelt. Neben allochthonem Bestandesabfall führen Eisen- und Manganhydroxide, die unmittelbar an den Sickerwasseraustrittstellen ausfallen, bei relativ geringen Arsen- und Radiumkon¬zentrationen im Wasser zu hohen Arsen- bzw. Radiumgehalten im Sediment (As ≤ 5 mg g-1; Ra-226 ≤ 25 Bq g-1). Unter reduktiven Bedingungen werden Ra-226 und Arsen jedoch leicht freigesetzt. Ausgehend von den Untersuchungsergebnissen wird eine mögliche Anordnung für eine naturnahe passive Sickerwasserbehandlung vorgeschlagen.