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Master's Dissertation
DOI
10.11606/D.85.2013.tde-04072013-163633
Document
Author
Full name
Maurício Guimarães Sabbag
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2013
Supervisor
Committee
Marumo, Júlio Takehiro (President)
Cota, Stela Dalva Santos
Vicente, Roberto
Title in Portuguese
Estudo da migração de radionuclídeos em depósito para fontes seladas tipo poço tubular
Keywords in Portuguese
fluxo
fratura
migração
radionuclídeos
repositório
segurança
transporte
Abstract in Portuguese
Visando contribuir com o desenvolvimento de uma metodologia adequada ao Brasil para deposição de fontes seladas fora de uso, o presente estudo avaliou cenários de migração de radionuclídeos para fora de um repositório profundo tipo poço tubular. Considerou-se uma fratura anelar como caminho preferencial de fluxo da água subterrânea, que futuramente adentrará os poços, entrando em contato direto com as fontes. No futuro, fenômenos naturais e ação antrópica poderiam levar à degradação dos materiais que formam as barreiras artificiais do repositório e formar uma via preferencial de transporte e migração dos radioisótopos depositados. Haveria intrusão de água subterrânea e contato com as fontes seladas, corrosão e transporte dos radioisótopos para o ambiente acessível ao homem. A modelagem de transporte considerou percolação de água subterrânea numa fratura causada pelo descolamento entre o tubo de aço e a pasta de cimento, que separa o repositório do meio geológico. Foram simulados cenários de migração e o estudo poderá ser aproveitado na escolha de sítio e de novas técnicas para selagem. Diferentes gradientes hidráulicos e espessuras de fratura, entre outros parâmetros, influirão diretamente no fluxo pela fratura postulada que resultarão em diferentes tempos de trânsito até a biosfera.
Title in English
Study of radionuclide migration in repository type tubular well for sealed sources deposition
Keywords in English
flow
fracture
migration
radionuclides
repository
safety
transport
Abstract in English
The present study models radionuclide migration scenarios out of a deep borehole for disposal of disused sealed radioactive sources (DSRS). The aim is to contribute to the development of methodologies for the safety assessment of the repository. It is assumed that, in the future, anthropogenic and natural phenomena could impair the capacity of the engineered barriers to prevent the radionuclides from spreading to the accessible environment. Groundwater intrudes into the repository, corrodes the sealed sources and transports the radioisotopes to the biosphere. The model considers percolation of groundwater through an annular fracture caused by a detachment between the borehole steel casing and the cement backfill. A range of values of hydraulic gradients, fracture apertures, radionuclide sorption capacity in the cement backfill were considered in calculating flow and radionuclide transport through the postulated fracture. The present study shows, by comparing different scenarios, the variation of hydraulic gradients associated with different apertures of the fracture, exposing, through charts, the radionuclides transit times. The results of the study may be used in safety assessments and for selecting sites and materials for a 400 m deep borehole repository, for the present Brazilian inventory of DSRS.
 
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2013SabbagEstudo.pdf (4.31 Mbytes)
Publishing Date
2013-07-30
 
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