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, (226)Ra and (228)Ra 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 (226)Ra and (228)Ra 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)SO(4). The precipitate was filtered and weighted to calculate the chemical yield. The filter containing the precipitate of Ba(Ra)SO(4) 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 (226)Ra and (228)Ra. The activity values of (226)Ra and (228)Ra calculated by the two methods are in good agreement with the reference values, indicating that both methods are suitable for the determination of (226)Ra and (228)Ra.

Exposure of workers in a mineral processing industry in Brazil.

In Brazil there are many regions where the extraction mining and processing of ores containing elements of great economical importance as tin, niobium and tantalum. Some of these ores have uranium and thorium natural decay series associated. This study was carried out in a niobium mine, where is obtained concentrates of niobates-tantalates, cassiterite and zirconite. The aim of this study is the evaluation of the occupational exposure to uranium, thorium, niobium and tin through urine bioassay data. In order to have it, 105 urine samples were analysed: 17 samples of exposed workers collected after a working day, 49 samples of exposed workers collected before a working day and 39 samples of local non-exposed people, assigned as a control group. The samples were analysed by mass spectrometry. The obtained results showed that the average concentration of Nb, Sn and U in the exposed group is statistically higher than those found in the control group indicating an occupational exposure. For Th there were no statistically difference between the exposed and the control group.