Page 200 - 00. Complete Version - Progress Report IPEN 2014-2016

200 Nuclear Science and Technology | Progress Report

person methodology are evaluated and com- used to estimate biogeochemical fluxes of ma-
pared to the critical group methodology cur- rine particles and nutrients that occur in the
rently used for regulatory control of Brazilian water column as well as in the sediment. Sever-
nuclear facilities. As a reference, the predict- al research works applied the distribution and
ed potential releases of radionuclides result- the respective disequilibrium degree of natu-
ing from the normal operation of the Urani- ral radionuclides in the environment, including
um Hexafluoride Production Plant (USEXA), geochronological models for obtaining histori-
located at Centro Experimental Aramar (CEA), cal information on samples of certain sediment
were used. Specifically, the objectives are: to profile. The radiochemical characterization of
carry out the environmental radiological im- the distribution of Ra, Ra and Pb from a
226
210
228
pact for CEA, using the two recommended sedimentary column called 1B (248 cm long)
methods (deterministic and probabilistic) for collected in the Admiralty Bay, Antarctic Pen-
the representative person, as described by the insula region, was performed. The methodol-
ICRP (2006); to make the comparison of results ogy used included the acid leaching of sedi-
obtained with these methods with those ob- ment samples followed by the radiochemical
tained with the methodology used for the crit- sequential separation of 226 Ra and 228 Ra by
ical group; and, make a critical analysis of the co-precipitation with Ba(Ra)SO4 and Pb by
210
need and the availability of data for the appli- co-precipitation with PbCrO4. All measure-
cation of these methodologies, as well as its ments were carried out by counting of gross
consequences for the operational control of alpha and gross beta measures in a low back-
CEA. Based on the results obtained, it is em- ground gas flow proportional detector. The ac-
phasized that the use of the methodology for tivity concentrations of 226 Ra and 210 Pb were
calculating critical group remains a simple and used to estimate the unsupported Pb activ-
210
efficient way to evaluate radiological environ- ities present in sediment profile 1B. Based on
mental impact when compared to the use of unsupported Pb data and the application of
210
the representative person methodology, which the CIC model (Constant Initial Concentration),
makes the establishment of monitoring pro- it was possible to determine the sedimenta-
grams, and therefore the environmental radio- tion rate of 0.59 ± 0.05 cm·y1.
logical control, simpler and objectives.
Study of natural radionuclides Ra, Ra and
228
226
Natural Radioactive Tracers 210 Pb in marine sediment cores from Southwest
Atlantic Ocean during the Holocene
Evaluation of the activity concentration of
210
226 Ra, Ra and Pb in sediments from Natural radionuclides from U and Th se-
228
238
232
Antarctica in the Admiralty Bay region ries have been successfully applied as tracers
of environmental process and climate changes.
The natural radionuclides from radioactive se- The Pb (half-life of 22.2 years) is used in the
210
ries of 238 U, 235 U and 232 Th have been applied geochronological dating technique of sediment
as tracers in environmental studies for un- cores of the last 100–150 years, and its respec-
derstanding the dynamics that occur in both tive sedimentation rate determination. The
marine and terrestrial environment, as for ex- study of 226 Ra and 228 Ra concentrations (half-
ample, in research of oceanic processes and lives of 1600 years and 5.75 years, respective-
management of the coastal region. In the ma- ly) helps calculate the activity of Pb in excess
210
rine environment, these radionuclides can be in the environment, besides being important

Instituto de Pesquisas Energéticas e Nucleares