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144
ST 2.1 –
Radiación natural, NORM y TENORM
NATURAL OCCURRING RADIONUCLIDES IN NOVEL SAND BEACHES
FROM ESPÍRITO SANTO, STATE, BRAZIL
Ribeiro de Aquino, Reginaldo*; Roxana Soreanu Pecequilo, Brigitte
Instituto de Pesquisas Energéticas e Nucleares. Brasil.
* Responsible author, email: raquino@ipen.br
Due the geological conditions and millenary processes of sedimentation, the sand of Espírito
Santo beaches contains minerals such as ilmenite, monazite, zirconite and rutile, sources of
uranium and thorium natural radioactive minerals. In previous works, several beaches from
Guarapari and Vitória regions were studied for natural radioactivity assessment. In this work,
novel locations in Espírito Santo state, southeast Brazil, from the mouth of Itapemirim river
(south of the state) to the mouth of the river Cricaré were collected and the natural radioactivity
in the beach sand samples was determined by measuring the ²²
⁶
Ra, ²³²Th and
⁴⁰
K concentration
activities. In these sands, the minerals from the silica group (white up to yellow) represent the
major concentration and the tonal variation is a strong indication of an anomalous radioactive
region. Sand samples tightly sealed in standard 100 mL HDPE flasks were measured by high
resolution gamma spectrometry after a resting time of approximately 4 weeks before counting,
in order to ensure secular equilibrium of natural uranium and thorium series. The ²²
⁶
Ra
concentration was determined as the weighted mean from the average concentrations of ²¹
⁴
Pb
and ²¹
⁴
Bi, the 232Th concentration was determined as the weighted mean from the average
concentrations of ²²
⁸
Ac, ²¹²Pb and ²¹²Bi and the
⁴⁰
K concentration by its single radiation of 1460 keV.
The results show the higher concentrations for the south region, namely 4300±500 Bq•kg¯¹ for
²²
⁶
Ra, 37000±2600 Bq•kg¯¹ for ²³²Th and 5000±570 Bq•kg¯¹ for
⁴⁰
K. For Great Vitoria central
metropolitan region, the higher values were 3200±200 Bq•kg¯¹ for ²²
⁶
Ra 20000±1300 Bq•kg¯¹ for
²³²Th and 2200±200 Bq•kg¯¹ for
⁴⁰
K. For the upstate region, the higher values were 30±6 Bq•kg¯¹ for
²²
⁶
Ra, 111±10 Bq•kg¯¹ for ²³²Th and 200±10 Bq•kg¯¹ for
⁴⁰
K.