Elemental interferences in the analysis of uranium by delayed-neutron counting

Major physical and elemental effects influencing U analysis were investigated at the fully automated Risø delayed-neutron counting facility. Changes in the physical conditions at the analytical facility can be closely controlled and most physical interference parameters are of minor importance for the analysis. Experiments were performed with artificial granitic and basaltic rocks to estimate the actual influence of Be, B, Li, Al, Na, Mn, Fe, rare earth elements and Th on the U analysis. The neutron counting rate from U is increased by about 1% when 1000 ppm Be are added to a 5-g sample. For the strong neutron absorbers B and Cd the correction factors are about −1 and −2%, respectively, per 1000 ppm interfering element present. For the rare earth elements Sm and Gd these correction factors were −2.2% and −10.2% per 1000 ppm added element, respectively. High gamma-radiation fluxes from Al, Mn and Fe have no significant effect on the U analysis.