[en] The present work describes the procedure carried out for the preliminary determination of neutron flux parameters for the nuclear research reactor IAN-R1 (RNI IAN-R1) through the not covered triple monitor method in the nucleus peripheral irradiation position. Using this method, the thermal flux value (φ_th), the epithermal neutron flux symmetry factor (α) and the ratio between thermal neutron fluxes with respect to the epithermal neutron flux (f) were estimated. Those parameters were obtained by irradiating zirconium (Zr) monitors and a gold-aluminum alloy monitors (Au-Al 0.1% Au), which were irradiated at the G3 and G4 irradiation positions of the RNI IAN-R1. The following values were found for the parameters estimated at an operating power of 30 kW, φ_th= 2,1 * 10¹¹ cm² s^-1 (variance CV 4%), α = 0,02 (CV 83 %), and f =67 (CV 8 %). The high variance in α could be explained if we consider that the method only uses 3 capture reactions to describe the epithermal neutron spectrum. The variance could be improved by application of multimonitor methods for neutron flux characterization.

[en] This work describes a procedure conducted using the neutron activation analysis technique for the validation of lanthanum (La) mass fraction determination in soil matrices. This study shows the principles of application of the relative method to instrumental neutron activation analysis and presents the experimental procedure used to evaluate the following performance parameters: selectivity, linearity, detection limit, quantification limit, precision, trueness and uncertainty. The results show that in the range of 0.66 to 38.0 mg/kg La, the method satisfies the acceptance criteria established in the validation process; as a consequence, the assaying of La by the developed method offers satisfactory results.