View More View Less
  • 1 Comissão Nacional de Energia Nuclear Radiochemistry Division, Instituto de Pesquisas Energéticas e Nucleares Caixa Postal 11049 São Paulo SP (Brasil)
Restricted access


The procedure for thorium determination in ammonium diuranate (ADU) and rocks, by neutron activation analysis after chemical separation of233Th, is presented. The separation of233Th from the interfering radioisotopes is based on the retention of233Th by a resin saturated with thorium (isotopic exchange) and on the elution of the interfering radioisotopes by a dilute solution of thorium in 0.5M HCl (ion exchange). The determination limit of thorium in rocks and ADU was found to be 0.56 and 9.3 g, respectively, when a 20% relative standard deviation was assumed as acceptable. The highest value obtained for the determination limit of thorium in uranium compounds, on account of the234Th activity present, is discussed.