Rapid determination of gold in Romanian auriferous alluvial sands, concentrates and rocks by 14 MeV NAA

Abstract

The nuclear and spectral interferences in the 14 MeV neutron activation analysis (NAA) of gold from Romanian auriferous alluvial sands, concentrates and rocks have been studied and the optimum of activation, cooling and measuring times was determined for a maximum peak-to-background ratio for gold. The contribution of the nuclear interfering elements in the samples, Hg and Pt, to the concentration of gold has been calculated and, concluded that the nuclear reactions ¹⁹⁷Au(n,2n)¹⁹⁶Au, ¹⁹⁷Au(n,2n)^196mAu and ¹⁹⁷Au(n,n')^197mAu can be used for gold determination, with minimal errors. Using the nuclear reactions ¹⁹⁷Au(n,n')^197mAu and ¹⁹⁷Au(n,2n)¹⁹⁶Au the spectral interferences are minimal and are due to Rb, Ti and V for a short irradiation and to Se for a long one. Two methods of fast gold determination were proposed for auriferous alluvial sands and rocks in the range of 20-2500 ppm, under the optimum conditions established so that the systematic errors of analysis due to the gold accompanying elements can be considerably diminished. For measuring the induced gamma-radioactivity in the samples either a short irradiation (25 seconds) with a NaI(Tl) detector or a long irradiation (3000 seconds) with a Ge(Li) detector were used.