Multi-criteria model to support decision-making for the remediation of urban areas

Under the environmental modeling Project of radioecology research area of IRD (CNEN), several tools have been developed to support post-emergency activities. Currently, a multi-criteria model is in development with the aim of supporting decision-making processes under the radiological protection point of view. At this stage, we are focusing on the decontamination of urban areas. The model includes five calculation modules: (i) averted doses to the public due to remediation procedures; (ii) occupational exposure of remediation workers; (iii) properties of the wastes generated by a remediation procedure; (iv) classification of each procedure for a specific urban scenario based on previously calculated quantities; and, (v) multi-criteria rank calculation. The classification of procedures is based on two types of criteria previously defined, both also included as input data of the model. The first type, called Subjective Criteria, is based on experts’ opinions collected through questionnaires. The second type, called Technical Criteria, is calculated according to the outputs of the three first modules of the program. The output of the model is a rank order list indicating the priority of procedures to use for each different type of urban environment. The use of results based on criteria and methods developed previously to the occurrence of a contamination event intends not only to provide an input to decision-making processes but also to improve public confidence on authorities responsible for the remediation decisions

Geoquímica de radionuclídeos naturais em solos de áreas circunvizinhas a uma Unidade de Mineração e Atividade de Urânio Geochemistry of natural radionuclide in soils surrounding a Mining and Plant Uranium Concentration

Os impactos ambientais advindos da exploração e do beneficiamento de U são, em grande parte, idênticos àqueles causados por atividades minero-extrativistas em geral. Este trabalho teve o objetivo de determinar a partição geoquímica dos radionuclídeos naturais 238U, 226Ra e 210Pb em áreas circunvizinhas à Unidade de Mineração e Atividade de Urânio (URA) das Indústrias Nucleares do Brasil S.A., localizada na Província Uranífera de Lagoa Real, no município de Caetité, na região sudoeste do Estado da Bahia. Foram coletadas amostras de solo em cinco áreas circunvizinhas à URA, representando as principais classes de solos da região, na profundidade de 0-20 cm. Nas cinco áreas, foram determinados o teor de atividade total e o fracionamento geoquímico nas frações: F1 - levemente ácida, F2 - reduzível, F3 - oxidável, F4 - alcalina e F5 - residual. As atividades totais médias foram, em Bq kg-1 de solo, de 50 para 238U, 51 para 226Ra e 159 para 210Pb. Os extraídos na fase potencialmente biodisponível (F1) foram: 11 % para 238U, 13 % para 226Ra e 3 % para 210Pb. O 238U apresentou maior biodisponibilidade nos solos mais ácidos e maior afinidade pelos óxidos de Fe, o que não ocorreu para o 226Ra, tendo este apresentado a maior biodisponibilidade. O 210Pb apresentouse predominantemente associado a F5. As percentagens elevadas de 238U, 226Ra e 210Pb na fração geoquímica F5 indicam que as atividades observadas nos cinco solos estão, predominantemente, associadas ao material que deu origem a esses solos, e não a um processo de contaminação artificial em função da atividade da URA.<br>The environmental impacts resulting from uranium exploration and processing are to a great extent identical to those caused by extractive mining activities in general. This study aimed to determine the geochemical partitioning of the natural radionuclides 238U, 226Ra and 210Pb in areas surrounding the Uranium Mining and Concentration Plant (URA) of the Brazilian Nuclear Industries S.A., in the uranium deposit region of Lagoa Real, in Caetité, southwestern Bahia state. Representative soil samples of the main regional soil classes were collected from the layer 0-20 cm, in five areas around the URA. The level of total activity and geochemical fractionation (F1slightly acidic, F2 reducible, F3 oxidisable, F4 alkaline, and F5 residual) were determined for the five areas. The average total radioactivity levels were, in Bq kg-1 soil: 50 for 238U, 51 for 226Ra, and 159 for 210Pb. During the potentially bioavailable phase (F1) 11 % were extracted for 238U, 13 % for 226Ra and 3 % for 210Pb. The bioavailability of 238U was higher in more acidic soils and the affinity for iron oxides was greater, unlike in the case of 226Ra, with the greatest bioavailability. 210Pb was predominantly associated with F5. The high percentage of 238U, 226Ra and 210Pb in the geochemical fraction F5 indicates that the concentrations observed in the five soils are predominantly associated to the parent material of these soils, rather than to an artificial contamination caused by the URA activity