title: Determination of the neutron spectrum shape parameter alpha in k0 NAA methodology using covariance analysis.
abstract: The k(0) method for quantitative reactor neutron activation analysis (NAA) has been applied in several laboratories for the determination of multi-elemental concentrations in different materials. The general formula that yields the concentration value can be divided in two parts: one involving detection parameters and the other involving irradiation parameters. A rigorous uncertainty calculation must take into account the correlations between each of these parameters. The Nuclear Metrology Laboratory at IPEN has a research program intended to develop a methodology applying covariance analysis in order to obtain the overall uncertainty in the concentrations of different elements in a given sample, and the correlation between each pair of them. The present paper concentrates in the determination of the neutron spectrum shape factor alpha by two methods: Cd-covered and Cd-ratio, using experimental data obtained in the IEA-R1 research reactor. The final values for alpha were: (0.001+/-0.018) and (0.001+/-0.019) for the Cd-covered and Cd-ratio methods, respectively, in good agreement with each other.
authors.affiliation: Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN/SP), Centro do Reator de Pesquisas-CRPq, São Paulo-SP, Brazil. msdias@ipen.br
authors.forename: Mauro S
authors.initials: MS
authors.lastname: Dias
authors.forename: Vanderlei
authors.initials: V
authors.lastname: Cardoso
authors.forename: Marina F
authors.initials: MF
authors.lastname: Koskinas
authors.forename: Ione M
authors.initials: IM
authors.lastname: Yamazaki
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D008956:Models, Chemical; D015233:Models, Statistical; D009501:Neutron Activation Analysis / Q000379:methods*; D013057:Spectrum Analysis / Q000379:methods*