Page 53 - PR 2014 2016 07 Nuclear Science and Technology

Nuclear Science and Technology | Progress Report 195

and compared to the critical group method- marine particles and nutrients that occur in
ology currently used for regulatory control of the water column as well as in the sediment.
Brazilian nuclear facilities. As a reference, the Several research works applied the distribu-
predicted potential releases of radionuclides tion and the respective disequilibrium degree
resulting from the normal operation of the Ura- of natural radionuclides in the environment,
nium Hexafluoride Production Plant (USEXA), including geochronological models for ob-
located at Centro Experimental Aramar (CEA), taining historical information on samples of
were used. Specifically, the objectives are: to certain sediment profile. The radiochemical
carry out the environmental radiological im- characterization of the distribution of 226 Ra,
pact for CEA, using the two recommended 228 Ra and 210 Pb from a sedimentary column
methods (deterministic and probabilistic) for called 1B (248 cm long) collected in the Ad-
the representative person, as described by miralty Bay, Antarctic Peninsula region, was
the ICRP (2006); to make the comparison of performed. The methodology used included
results obtained with these methods with the acid leaching of sediment samples followed
those obtained with the methodology used for by the radiochemical sequential separation of
228
the critical group; and, make a critical analysis 226 Ra and Ra by co-precipitation with Ba(Ra)
of the need and the availability of data for the SO and Pb by co-precipitation with PbCrO .
210
4 4
application of these methodologies, as well as All measurements were carried out by count-
its consequences for the operational control ing of gross alpha and gross beta measures
of CEA. Based on the results obtained, it is in a low background gas flow proportional
emphasized that the use of the methodology detector. The activity concentrations of 226 Ra
for calculating critical group remains a sim- and Pb were used to estimate the unsupport-
210
ple and efficient way to evaluate radiological ed Pb activities present in sediment profile
210
210
environmental impact when compared to the 1B. Based on unsupported Pb data and the
use of the representative person methodology, application of the CIC model (Constant Initial
which makes the establishment of monitoring Concentration), it was possible to determine
programs, and therefore the environmental the sedimentation rate of 0.59 ± 0.05 cm • y .
-1
radiological control, simpler and objectives.
Study of natural radionuclides Ra, Ra and
226
228
Natural Radioactive Tracers 210 Pb in marine sediment cores from Southwest
Atlantic Ocean during the Holocene
Evaluation of the activity concentration of
226 Ra, Ra and Pb in sediments from Natural radionuclides from U and Th series
228
210
238
232
Antarctica in the Admiralty Bay region have been successfully applied as tracers of
environmental process and climate changes.
The natural radionuclides from radioactive The Pb (half-life of 22.2 years) is used in the
210
series of 238 U, 235 U and 232 Th have been ap- geochronological dating technique of sediment
plied as tracers in environmental studies for cores of the last 100–150 years, and its respec-
understanding the dynamics that occur in tive sedimentation rate determination. The
both marine and terrestrial environment, as study of 226 Ra and 228 Ra concentrations (half-
for example, in research of oceanic processes lives of 1600 years and 5.75 years, respectively)
and management of the coastal region. In the helps calculate the activity of 210 Pb in excess
marine environment, these radionuclides can in the environment, besides being important
be used to estimate biogeochemical fluxes of tracers of marine processes, as ground water