Application of INAA in the Characterisation and Quantification of Dy-Labeled Ceramic Spheres and Their Use as Inert Tracers in Soil Studies

An inert, activable tracer method, using sized ceramic spheres custom labeled with 15% Dy₂O₃ during manufacture, has been developed to study soil aggregation. Instrumental neutron activation analysis (INAA) with a Slowpoke reactor, using ^165mDy (T_1/2 = 1.26 min), provides an extremely rapid means with which to characterise the Dy-content of the various size fractions of labeled spheres from different production runs. In contrast, the Dy-content (and hence number of spheres) of 5—g soil/sphere mixtures is determined using the longer-lived ¹⁶⁵Dy (T_1/2 = 2.33 hrs) following a 30-minute decay period during which the otherwise interfering ²⁸Al (T_1/2 = 2.24 min) preferentially decays. The method is expected to find many applications.