Page 19 - IEAR1_60y_Book_of_Abstracts_UPD

60 Years of IEA-R1 International Workshop 7

the host mineral crystal lattice as they shift. As uranium is a trace element in a
number of minerals and, since the 238 U isotope fission happens spontaneously in a
known rate, the fission tracks can be used to date the host minerals. Many natural
isotopes are subject of decay by spontaneous fission. However, only 238 U has a fission
half-life short enough to produce a significant number of spontaneous tracks through
the time period of geological interest (8.410 15 years) (Wagner & Van Den Haute,
1992).
Fission track dating is based in a general radioactive decay equation, requiring
an estimate of the relative abundance of parent and daughter product. In this case,
the abundance of 238 U, obtained by irradiating the sample with low-energy thermal
neutrons, which induces 235 U fission recorded in an external detector, and the number
of spontaneous fission tracks per unit volume, counted on a specific surface. Provided
the neutron flux is monitored, the number of induced tracks indicates the abundance
of 235 U. Since the 235 U/ 238 U ratio is constant in nature, the abundance of 238 U can
be estimated.

SUCCESSFUL LONG-TERM COLLABORATION BETWEEN THE IEA-R1
NUCLEAR RESEARCH REACTOR OF IPEN/CNEN AND THE
RADIOISOTOPES LABORATORY OF CENA/USP 30 Nov
2:30pm
E.A.N. Fernandes a
a lis@cena.usp.br

Nuclear Energy Center for Agriculture, University of São Paulo, Brazil

The strength of strong ties in scientific collaboration between Nuclear Energy
Center for Agriculture of the University of São Paulo (CENA/USP) and Institute of
Nuclear Energy Research of the Brazilian Nuclear Energy Commission (IPEN/CNEN)
since 1985 has resulted in dozens of scientific and academic researches in the vari-
ous areas of knowledge. The irradiation of samples in the IEA-R1 nuclear research
reactor allowed the Radioisotopes Laboratory to perform neutron activation analysis
in the last 32 years effectively to the point of forming the basis to be designated
in 2007 as a primary method of measurement in the CCQM/BIPM (Consultative
Committee for Amount of Substance Ű Metrology in Chemistry and Biology/Bureau
International des Poids et Mésures), Sèvres, Paris, France, 2007. Several studies
were performed by using instrumental neutron activation analysis from which some
are herewith described. The pioneer one was developed in the sucroenergetic sec-
tor to evaluate the technological quality of the sugarcane collected in the field and
delivered to the industry by finding chemical elements to be used as soil tracers
in the sugarcane load and in the entire industrial processing for sugar and ethanol
production. A series of innovative research on the Brazilian uranium mining in the
Poços de Caldas Plateau (MG) and Lagoa Real Province (BA) have been performed
for the chemical characterization of waste rocks. A comprehensive study of sus-
pended and floodplain sediments along the Amazon River basin to the continental
shelf. Environmental quality studies involving biomonitoring of the Atlantic Forest