Reevaluation of Spectral Parameters and Neutron Fluxes in IC-7 Irradiation Channel of TRIGA MARK I IPR-R1 Research Nuclear Reactor

The core configuration of the TRIGA MARK I IPR-R1 nuclear research reactor, Brazil, has been modified six times since the first criticality and the neutron fluxes have been determined using experimental and semi theoretical methodologies determining the neutron fluxes in different irradiation channels and devices, applying different procedures and materials. This reactor operates at 100 kW, however, after new configuration for 250 kW in 2001, the carousel no longer rotates during irradiations aiming at preserving the rotation mechanism. In 2003, the spectral parameters were determined experimentally by the "Cd-ratio for multi-monitor" in five specific channels aiming at the application of NAA k0-standardized method. The determinations were repeated applying the same procedure in 2016, 2018 and 2019. Values for thermal and epithermal neutron fluxes as well as f and a spectral parameters were determined. The experimental results for CRM BCR-320R were calculated by the k0-method of NAA, using the spectral parameters for irradiation channel IC-7 obtained in 2003, 2016, 2018 and 2019 and evaluated by En-score. The values showed that the differences in the results compared to those in 2003 were lower than 2.5%, inside the uncertainty of the method. It shows that the k0-method installed in CDTN is reliable and useful for various purposes. The results of the spectral parameter f presented small differences, in a period of 16 years, pointing out the stability of operation of the reactor TRIGA MARK I IPR-R1.

Trace elements detection in whole food samples by neutron activation analysis, k0-method

The increase in anthropogenic activities has been contributing to considerable increasing of the chemical elements concentration in the environment. One consequence is the need of monitoring the elemental composition of food available for consumption. Numerous techniques have been used to detect inorganic elements in biological and environmental matrices, always aiming reaching lower detection limits in order to evaluate the trace element content in the sample. This study evaluated the presence of inorganic elements in whole food samples, mainly elements on trace levels applying the neutron activation technique, k0-method. This method produces accurate and precise results, without the need of chemical preparation of the samples. For this purpose, four samples of different types of whole foods were irradiated in the TRIGA MARK I IPR-R1 research reactor – located at CDTN/CNEN, in Belo Horizonte, MG, Brazil. It was possible to detect, in total, twenty-three elements. Nine elements are considered essentials, according to nutrition literature, thirteen are not essentials and one, classified as contaminant element by legislation. The majority of the elements determined are not reported in the TACO (Brazilian Table for Food Composition). It means that the professionals of health do not know, in fact, the real chemical elemental composition in foods and the population do not know what they are ingesting in terms of chemical elements and the risks of this ingestion. This study reaffirms the INAA, k0–method, is an efficient technique for detecting trace elements in food samples.