Determination of natural uranium and thorium content by alpha spectrometry

Alpha-spectrometry has been used to determine simultaneously the uranium and thorium content in solid samples as well as the equilibrium with their decay products. Samples require preparation for measurement only by milling in a disc mill, without additional chemical treatment. Instrumentation used consisted of a commercial large area Frisch grid ionisation chamber. At concentration levels of 100 ppm of U or Th, deviations from decay equilibrium were measured within ± 10%, with increasing error margins for smaller concentrations. The detection limits appear to depend primarily on the background count rates of the chamber. (author)