Thorium isotopic analysis by alpha spectrometry

The technique of alpha spectrometry is used to detect alpha particles and to determine their energy. In this way the technique is able to provide simultaneously quantitative information (i.e. the activity) and qualitative information (the identity) on any radionuclide that emits an alpha particle. The longer-lived naturally occurring isotopes of thorium are all alpha emitters so the technique can be used to quantify them directly and this is extremely important if radiation doses due to intakes of these isotopes into the body are to be accurately assessed. The principle of the technique is discussed, its advantages and disadvantages, and the instrumentation that is commonly used today. The need for radiochemical separation is discussed and illustrated by reference to analysis procedures in current use for thorium isotopic analysis. Practical issues such as detection limits, quality control procedures. sample throughput and cost will be covered.