Evaluation of two radiochemical procedures for the determination of uranium and thorium isotopes in coal samples

Two procedures are presented for the sequential determination of uranium and thorium isotopes in coals. They are based on acid leaching on a hot plate, and on acid digestion in closed vessels using microwave irradiation. Both were applied to the analysis of International Atomic Energy Agency (IAEA) and National Institute of Standards and Technology (NIST) reference materials, and to the study of coals with different ranks. The greatest recoveries were obtained with the acid digestion method. This method was more effective than the leaching method for the extraction of the uranium isotopes in coals. The effectiveness of the thorium isotopes extraction was similar in the two methods.