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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
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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