On the feasibility of determining the Th activity in minerals without the addition of a Th radiotracer.

The necessity of measuring the radioactivity of the Тh nuclide arises when attempting to solve a number of geochemical or geochronological problems based on the effects of radioactive disequilibrium in the U series. It is the authors' opinion that the use of the traditional α- and β-emitters of thorium as a radiotracer in order to determine the activity of Тh leads to various inconveniences and difficulties of a technical nature. The authors recommend using the Тh isotope contained in the study sample as the simplest and most natural way of measuring the chemical yield of the targeted nuclide (Тh). A sequence of radio-analytical procedures is proposed that will provide a correct assessment of the radioactivity of Тh. In addition, a specific example and an evaluation of the accuracy of the proposed methodology are presented, using actual experimental data.