1. Center for Environmental Studies and Basin Studies LaboratorySão Paulo State University, UNESP Rio Claro SP 13506‐900 Brazil.
2. Department of Applied GeologySão Paulo State University, UNESP Rio Claro SP 13506‐900 Brazil.
3. Department of Nuclear EngineeringFederal University of Rio de Janeiro, COPPE Rio de Janeiro RJ 21941‐972 Brazil.