DEVELOPMENT AND VALIDATION OF A TECHNIQUE FOR THE DETERMINATION OF 226Ra AND 228Ra BY LIQUID SCINTILLATION IN LIQUID SAMPLES

Radium isotopes are dispersed in the environment according to their physicochemical characteristics. Considering their long half-lives and radiological effects, Ra-226 and Ra-228 are very important issues in radiological protection. In Brazil, radium isotopes represent an exposure problem both in nuclear fuel cycle installations and in high natural radiation background areas. The experimental part of this work includes the development of a technique for the determination of Ra-226 and Ra-228 by liquid scintillation with potential application in biological samples. Radium was concentrated and then separated from other constituents of the sample by co-precipitation/precipitation with Ba(Ra)SO4. The precipitate was filtered and weighted to calculate the chemical yield. The filter containing the precipitate of Ba(Ra)SO4 was transferred to a scintillation vial. Two methods were used to prepare the sources. The first one consisted of the addition of water (8 ml), Instagel XF (8 ml) and UltimaGold (4 ml) in the vial containing the filter and the precipitate, forming a gel suspension. In the second method, the precipitate was dissolved with 0.2 M ethylene-diamine-tetra-acetic-acid solution (9 ml) and 11 ml of scintillation solution (Optiphase Hisafe 3) was added to the vial, forming an aqueous and an organic phase. The solutions obtained were counted in a low background scintillation spectrometry system (Quantulus) suitable for the detection and identification of both alpha and beta particles for the determination of Ra-226 and Ra-228. The activity values of Ra-226 and Ra-228 calculated by the two methods are in good agreement with the reference values, indicating that both methods are suitable for the determination of Ra-226 and Ra-228.