Soil is usually carried to the mills, as an impurity in sugar cane, leading to economic drawbacks for the industry. The quantification
of this dirt is important to identify its causes and for routine quality control. Several methods have been used for this
purpose, however, no single one has been pointed out as an industrial standard. The use of a γ-ray emitting radionuclide of
natural occurence was investigated and, after several soil and cane radioactivity analyses,212Pb was chosen as the best tracer. Calibration curves developed with the addition of soil in clean cane, from 0 to 10% (dry
mass), demonstrated the linearity of the method. Analyses of eleven samples taken from consignments showed that the procedure
was consistent and reliable when compared to the traditional ash method.
This work shortly describes the main steps involved in the design and development of the software package Quantu, created to conduct k0-standardized NAA. The package comprises a database as well as two individual programs. Quantu-MCA is dedicated to (g-ray spectrum analysis and Quantu-INAA is the interface for the database administration, also dealing with k0-method calculations.
New software was developed to assist users of the k0-approach in NAA to harmonize their results. The k0-IAEA software uses the holistic approach developed at the Delft Interfaculty Reactor Institute and incorporates the latest
k0 data catalogue together with additional information on coincidence and sum peaks, which together are used in the joint evaluation
of samples. Multiple irradiations as well as multiple measurements of samples are treated simultaneously. Flux parameter determination
as well as efficiency calibrations of detectors are accommodated using a single-measurement approach as developed at the Interfaculty
Reactor Institute, Delft. The standard Windows software will stimulate the application of the k0 approach through the free distribution and updates of the program.
Brazil has become the largest producer of biomass ethanol derived from sugar cane. The industrial production is based on the fermentation of sugar cane juice by yeast, inside of large volume vats, in a fed-batch process that recycles yeast cells. To study the dynamics of chemical elements in each operating cycle, five stages of the fementation process were considered: must, yeast suspension, wine, non-yeast wine and yeast cream. For this, a mass balance of the terrigenous elements, Ce, Co, Cs, Eu, Fe, Hf, La, Na, Sc, Sm, and Th, and the sugar cane plant elements, Br, K, Rb, and Zn, were established in fementation vats of an industrial scale unit, with sampling undertaken during different climatic conditions (dry and rainy periods). A similar distribution of the sugar cane characteristics elements was found for the stages analysed, while for the terrigenous elements a trend of accumulation in the yeast cream was observed. Preferential absorption of Br, K, Rb, and Zn by yeast cells was indicated by the smaller concentrations observed in yeast suspension than in yeast cream.
This work presents a comparison of analytical results obtained for U, Th, K, and Fe in solid material from tailings pond, carried out within the CIPC's Tailings Management Program, with those achieved by instrumental neutron activation analysis. The validity of the techniques applied for dissolution and determination of elements in high silicate grade material, as the present case, can be assured by good agreement of the resulst.
Studies concerning the accumulating capacity of native epiphytic bromeliads are of utmost relevance, due to the continuous
incorporation of chemical elements provided by these organisms in the ecosystems. Bromeliad species from diverse São Paulo
State conservation units, Brazil, were sampled for young, mature and old leaves using a sustainable sampling method. By applying
INAA, the accumulation of ten chemical elements, i.e. Br, Ca, Co, Fe, K, Na, Rb, Sc, Sr and Zn, was investigated in different
leaf vegetative stages. The bromeliads showed divergent chemical element distribution patterns, demonstrating a real complexity
in the accumulation and translocation mechanisms utilized by these plants.
Environmental quality assessment studies have been conducted with tree species largely distributed in the Atlantic Forest.
Leaf and soil samples were collected in the conservation unit Parque Estadual da Serra do Mar (PESM) nearby the industrial
complex of Cubatão, São Paulo State, Brazil, and analyzed for chemical elements by instrumental neutron activation analysis.
Results were compared to background values obtained in the Parque Estadual Carlos Botelho (PECB). The higher As, Fe, Hg and
Zn mass fractions in the tree leaves of PESM indicated anthropogenic influence on this conservation unit.
Selenium detection limits of INAA are normally above its concentration in most biological materials. Gamma-gamma coincidence
methodology can be used to improve the detection limits and uncertainties in the determination of selenium. Here, some edible
parts of plants were measured using a HPGe detector equipped with a NaI(Tl) active shielding, producing spectra both in normal
and coincidence modes. The results presented the reduction of the detection limits of selenium by a factor of 2 to 3 times
and improvement in the uncertainty of up to 2 times.
The experimental work involved the efficiency determination of three coaxial hyperpure Ge detectors, using point-like sources placed at various distances from the top cover of the detectors. Curves were fitted to the experimental data and a microcomputer routine was developed to calculate the efficiencies of cylindrical sources, including self-attenuation correction. Tested at various source and distance conditions, the procedure showed results sufficiently consistent for routine k0-INAA.
After more than ten years working with multicomparator instrumental neutron activation analysis, mainly applied to the characterization of environmental samples, the Radioisotopes Laboratory (CENA/USP) started changing gradually to the k0-method in 1997. The main activities developed, as well as some of the results obtained, are presented here. Even though there is much more work to be done, the good quality of the results and the possibility of elemental determinations without the co-irradiation of standards may lead to the definitive adoption of the k0-method in a near future.