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186   Nuclear Science and Technology | Progress Report





               where the fossil sample is found is known, it   Electron spin resonance (ESR) dating was ap-
               is possible to convert this dose into the age   plied to date a sample of fossil tooth found in
               of the sample by the equation: age=AD/Dan.     Ribeira Valley, São Paulo, Brazil. This region
               The annual dose rate coming from the radio-    is characterized by abundant fossil records
               active elements present in the soil and in the   of  Pleistocene–Holocene  South  American
               sample itself can be calculated by determining   megafauna belonging to different faunistic
               the U, Th and K concentration. Therefore, the   moments related to climate changes during
               determination of the dose rate depends on      the quaternary. The equivalent dose (De) was
               the concentration of these main radioactive    determined using single exponential fitting
               elements.                                      resulting in (24±1) Gy. The De was converted
                                                              to age using ROSY ESR Dating program and the
               Neutron Activation Analysis has the sensitivity   concentration of radioisotopes present in the
               and the accuracy necessary to determine U      sample and soil determined through neutron
               and Th with this objective. Depending on the   activation analysis. The ages cover the range
               composition of the sample, the determina-      of 25–34 ka. This information is important
               tion of U and Th can be improved irradiating   to contextualize other findings in the region
               the sample inside a Cd capsule, reducing the   from different sites and to help obtain better
               thermal neutron incidence on the sample and,   information about the climate changes in this
               therefore, diminishing the activation of possi-  region. (Partnership: Universidade Sagrado
               ble interfering nuclides.                      Coração, Bauru, SP, Brazil; Departamento de
                                                              Física, Faculdade de Filosofia Ciências e Letras,
               Electron spin resonance (ESR) dating was ap-   USP, Ribeirão Preto, SP, Brazil).
               plied to a Smilodon populator tooth found in
               “Toca de Cima dos Pilão”, located in the sur-  Relative INAA and k -INAA at
                                                                                    0
               roundings of the Serra da Capivara National    IPEN: a Comparative Study
               Park. Neutron Activation Analysis was used to
               determine the concentration of radioisotopes   The Neutron Activation Analysis Laboratory at
               present in the sample and in the sediment to   IPEN (LAN-IPEN) has been analyzing different
               calculate the internal and external dose rates.   kinds of samples for decades, using the relative
               The result of age found is 93±9 ka, which con-  method of instrumental neutron activation
               firmed the presence of this species in Serra da   analysis (INAA) at the IEA-R1 nuclear research
               Capivara National Park in the late Pleistocene.   reactor of IPEN. In this method, samples and
                                                              standards are irradiated simultaneously with
                Electron spin resonance (ESR) dating was ap-  neutrons under the same conditions. Elemental
               plied to a fossil human tooth and shell found at   concentrations are calculated by comparison
               the archaeological site Toca do Enoque located   of the activities of the gamma-rays from the
               in Serra das Confusões National Park (Piauí,   sample and standard. This procedure requires
               Brazil). The ages for the tooth and the shell   the preparation of element standards, which is
               (~4.8 kyBP) agreed with C-14 dating of the shell   very laborious and time consuming. Further-
               and other samples (charcoal) collected at the   more, some elements present in the sample
               same study site, showing the validity of ESR   cannot be analyzed due to the absence of a
               dating for this range of ages.                 corresponding element standard. The k -INAA
                                                                                                   0
                                                              method, developed by the Institute of Nuclear







                         Instituto de Pesquisas Energéticas e Nucleares
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