ABSTRACT
This paper discusses the use of a large sodium iodide detector to determine gamma-ray emitting radionuclides in living animals, and in particular the application of the technique to investigations that have followed the Chernobyl reactor accident. A series of experiments to validate the technique is presented. The detector and its associated electronics and data collection equipment are sufficiently robust for use in the field, and ancillary equipment to immobilize subjects such as sheep and cattle are readily available. Although the in vivo procedure underestimates activity concentrations in muscle tissue compared to results from samples obtained post mortem, the advantage is that the same animal can be measured repeatedly and reproducibly.