Sampling technique and analysis of the sediments of low level wastes (LLW) of nuclear plant

Delay and decay is one of the techniques adopted by the nuclear plants for low level waste (LLW) before treating the effluents for final disposal. During this process the solution is kept in alkaline condition and is left open to the atmosphere which leads to the formation of algae which along with sand forms the sediment. The sediment is buried in shallow landfill sites. To reduce its volume, it is often compacted or incinerated (in a closed container) before disposal. It is important to know the composition and activity of the sediment before disposal to make it environmentally safe. The sediment analysis results are shown and the need for proper sampling technique is emphasized in this paper. It is evident from the table that the activity of the sediment is not consistent throughout the tank necessitating proper sampling before carrying out the analysis. The sampling are drawn from three different locations from a point near to the inlet of the effluents and mixed thoroughly to form a uniform sample. Similarly sampling is done from three different locations is done from the point farthest from the inlet of effluents. These are mixed to make a second sample. The average of the analysis results of these two samples are taken as the final value. Known volume of the sediment in the form of slurry is taken. centrifuged and the settled residue is analysed. The residue is dissolved in sulphuric acid and estimated by radiometry. (author)