Application of soda softening method for liquid radioactive waste solidification

Abstract At present, the liquid radioactive waste processing, solidification and utilization flowcharts are much in demand. In our experimental research, the removal of radium from real and model liquid radioactive waste samples has been achieved by the soda softening method. The technology is based on chemical interaction of alkali-earth metal compounds with soda which precipitates the compounds including those of radium. The softening method selection is accounted for its versatility which makes it possible to lower both the carbonate and non-carbonate concentration of calcium, and therefore, of radium. The research has been conducted on real and model liquid media that appear in nearsurface short-lived low-radioactive waste storages. All the experimental research has been performed in a specialized laboratory certified for work with radioactive substances and equipped with the necessary protection means. In our experimental research, the removal of radium from the real liquid radioactive waste reached 100 per cent (at 22.2 Bq/l initial activity), and with the soda softening method applied to the model radioactive liquid – 99.4 per cent (at 137 Bq/l initial activity). It was established the high content of magnesium in the radioactive liquids impeded the precipitation of calcium, the effectiveness of which correlated positively with Ra-226 removal.