RESUMO
The use of materials containing naturally occurring radionuclides for house construction may enhance the natural radiation background to which some population groups are exposed. External exposure results from gamma emitter radionuclides existing in the walls, floor and ceiling. Mathematical models can be used to predict external dose rates inside a room, provided the compartment geometry and the radionuclide concentration activities are known. This paper presents a methodology and a computer code for theoretical evaluation of indoor external gamma doses in the air. The room was modelled as three pairs of rectangular slabs of finite thickness. Doses were evaluated by applying a photon transport model, taking into account self-absorption and radiation build-up. Calculations were performed for 40K, 226Ra and 232Th, considering concrete walls. The results obtained show good agreement with those reported in the literature. Dose conversion factors are presented in a practical manner, ready to use for radiological impact screening.
Assuntos
Poluição do Ar em Ambientes Fechados/análise , Materiais de Construção/análise , Raios gama , Modelos Teóricos , Proteção Radiológica/métodos , Radioisótopos/análise , Radiometria/métodos , Medição de Risco/métodos , Carga Corporal (Radioterapia) , Simulação por Computador , Humanos , Doses de Radiação , Reprodutibilidade dos Testes , Fatores de Risco , Sensibilidade e EspecificidadeRESUMO
Spent or disused sealed radiation sources--no longer needed sources--may represent a risk of radiological accident or may be a target for criminal acts in countries where final disposal options are unavailable and where an increasing number of sources are being kept in extended storage. In developing countries, thousands of radium needles, teletherapy sources, oil well logging neutron sources, and miscellaneous industrial radioactive gauges are annually collected as waste and stored in research institutes. The objectives of the study described in this paper are to inventory such sources in Brazil, including those presently in use and those already collected as waste, and to design a dedicated repository where spent sources could be disposed of properly. The inventory of sources in Brazil and the concept of the repository are presented and its feasibility is discussed.
Assuntos
Documentação/métodos , Documentação/normas , Proteção Radiológica/métodos , Resíduos Radioativos/prevenção & controle , Eliminação de Resíduos/métodos , Eliminação de Resíduos/normas , Medição de Risco/métodos , Gestão da Segurança/métodos , Brasil , Equipamentos e Provisões , Arquitetura de Instituições de Saúde , Estudos de Viabilidade , Lesões por Radiação/prevenção & controle , Gerenciamento de Resíduos/métodos , Gerenciamento de Resíduos/normasRESUMO
Radionuclide contents were determined in the botton sediment of the Pinheiros river, into which the Instituto de Pesquisas Energéticas e Nucleares (IPEN) has been continuously discharging low level radioactive liquid effluents. The results showed that the activity of natural radionuclides and the activity of (137)Cs found in the sediment were within the range of the expected baskground for the region. (60)Co was the only other artificial radionuclide detected, with concentrations ranging from 0.20 to 0.85 Ba per kilogram dry weight, at some points of the river.