The application of Nisle unified formulation for ko - NAA standardization method

Current formulations of the well established k0- NAA standardization method are limited mainly by the '1/v' or 'non - 1/v' (n/γ) reactions nuclide status. Therefore, Nisle unified formulation, which covers some of these limitations, was investigated at GHARR - 1 for the simplified and effective utilization of the ko NAA standardization method. By making critical assumptions to the neutron flux spectrum and using the neutron monitoring standards (Au, Zr, Lu etc), the Nisle neutron flux parameters (Tn, F1) were theoretically calculated and experimentally determined for both inner (No.2) and outer (No.7) irradiation sites of GHARR - 1. Nisle F1 factor was found to be 0.0080 at 27.65 degrees Celsius of neutron temperature (Tn) for the inner irradiation site. These values were then used to carefully characterize the neutron flux spectrum of GHARR - 1 for the adoption of Nisle unified formulation to the k0 - NAA standardization method. The Nisle neutron flux parameters were then validated by using them to quantify a biological Standard Reference Sample (NIST 1547 Peach Leaves) for fourteen (14) different elements and geological Standard Reference Sample (NIST 1646a Estuarine Sediment) for thirteen (13) different elements. The measured mean concentrations (μ/g) were found to be in good arrangement with the certified values; generally within ±10%. (au)