THE APPLICATION OF NISLE UNIFIED FORMULATION TO THE k0 — NAA STANDARDIZATION METHOD

Abstract

Current formulations of the well established ko- NAA standardization method are limited mainly by the "1/v" or "non — 1/v" (n, y) reactions nuclide status. Therefore, Nisle unified formulation, which overcomes 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 (T„, F1) were theoretically calculated and experimentally determined for both inner (No.2) and outer (No.7) irradiation sites of GHARR — 1. Nisle F1factor was found to be 0.0080 at 27.65°C of neutron temperature (To) for the inner irradiation site. Also 0.0030 of Nisle F1factor at 20.74°C of Tnwere determined for the outer 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 ko — 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 a geological Standard Reference Sample (NIST 1646a Estuarine Sediment) for thirteen (13) different elements. The measured mean concentrations (.1.g/g) were found to be in good agreement with the certified values; generally within ±10%.