USING SODA SOFTENING TECHNOLOGY FOR RADIUM REMOVAL FROM LIQUID WASTE
DOI:
https://doi.org/10.33042/2522-1809-2024-6-187-50-56Keywords:
liquid radioactive waste, radium, soda softening, removal efficiency, calcium, magnesiumAbstract
The processes for treating liquid radioactive waste result in the creation of a concentrated waste stream in the form of sludge (which requires additional conditioning) and a supernatant/distillate, which can often be released from regulatory control and either directly discharged into the natural environment or discharged after further treatment. The radium removal technology studied in this article is based on the understanding that the solubility of alkaline earth metal carbonates (Group 2 of the periodic table) decreases from magnesium to radium. Thus, if calcium is precipitated as calcium carbonate, radium should also be incorporated into the precipitate, at least with a similar separation factor. As a result, the radium concentration is expected to decrease significantly.
The objects of the experimental study were real liquids from sludge containers of Poltava NGDU and model liquid radioactive environments. All experimental studies were performed in a specialized laboratory accredited for work with radioactive substances and equipped with the necessary means of personnel protection.
Experimental studies demonstrated radium removal from real and model radioactive liquid waste through soda softening. This technology is based on the chemistry of interactions between soda and alkaline earth metal compounds, which precipitate, including radium. In the experiments, radium removal efficiency from real radioactive liquid waste reached 100% (at an initial activity of 22.2 Bq/L), while soda softening of model radioactive liquid achieved 99.4% (at an initial activity of 137 Bq/L).
It was found that high magnesium content in radioactive liquids interfered with calcium precipitation, whose efficiency positively correlated with the effectiveness of Ra-226 removal. Furthermore, during soda softening of the tested liquids, the efficiency of calcium removal showed a positive correlation with the efficiency of Ra-226 removal. To achieve deeper removal of Ra-226 from Sample No. 1 to a level of 1 Bq/L, a second purification stage is required. The second stage could involve soda softening or other radium removal methods, such as sorption, chemical, or membrane technologies.
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