Authors:Nguyen Chau, J. Niewodniczański, J. Dorda, A. Ochoński, E. Chrusciel, and I. Tomza
This paper presents a method for the determination of radium isotopes in mineralised mine waters, based on the separation of alpha- and beta-intensities measured in the precipitate by a liquid scintillation spectrometer in two time intervals (1 day and 7 days) after radium precipitation. The count rates of -particles give not only the concentration of alpha emitters (226Ra and224Ra), but also make possible to find the -counting efficiency of the system and through that-to determine the concentration of the -emitting radium isotope (228Ra) with higher accuracy. An improved chemical procedure was elaborated. By this method radium isotopes in different water samples were determined, in wide range of concentrations, from about 0.06 Bq/dm3 in potable water to more than 100 Bq/dm3 in some mine brines. As an example some analytical results are given. The detection limit, defined as three standard deviations, is-for both radium isotopes –0.03 Bq/dm3 (for intial volume of water sample equal to about 1 dm3 and for counting time of each measurement not longer than 1 hour).
Authors:R. Wang, A. Chau, F. Liu, H. Cheng, P. Nar, X. Chen, and Q. Wu
The aim of this paper is to consider using effective natural minerals in studying the retardation and migration of radium under the influence of groundwater in the far-field of a radioactive waste repository. The properties of adsorbing radium by minerals are studied by adopting the static and dynamic adsorption method. Preliminary experimental results give confidence in the validity of using Maifanshih and barite to adsorb radium in water and to serve as effective retarding materials in radioactive waste repositories, their Kd values being 3815 and 2955, respectively. The study on a certain number of conditions of adsorbing radium by the promissing material Maifanshih is reported for the first time. The mechanism of radium adsorption has been discussed and modeling of migration of radium in the minerals has been presented to establish a rational basis for the longterm prediction required for safety assessment of underground disposal of radioactive waste.