Radioactivity levels in beach sand from the West Coast of Sri Lanka

Concentration of primordial radionuclides in 48 sand samples collected from the coastal strip from Uswetakeyyawa to Chillaw in the West Coast of Sri Lanka was measured using a high purity germanium (HPGe) detector. The measured activity concentrations of 232Th ranged from 14 ± 3 to 6257 ± 38 Bq kg-1. The maximum concentrations of 238U and 40K measured were 1243 ± 15 and 647 ± 37 Bq kg- 1, respectively and the minimum were below the detection limits. The detection limits of 238U, 232Th and 40K were 1.70, 2.37 and 10.41 Bq kg -1, respectively. The calculated external annual effective dose rate at one meter aboveground ranged from 5 - 4567 nGyh-1. More than 50 % of the samples analysed showed radium equivalent activity concentrations above the limit 370 Bq kg-1, which is the value recommended for the safe use of building materials for dwellings. The same 48 samples were parallely analysed using NaI (Tl) scintillation spectrometry. For 238U and 232Th the mean ratios of the values obtained by the two methods were 1.0148 and 1.0018, respectively. The findings of this study shows that scintillation spectrometry provides a cost effective method to measure U and Th in radioactive beach sand.

J.Natn.Sci.Foundation Sri Lanka 2013 41(4): 279-285

DOI: http://dx.doi.org/10.4038/jnsfsr.v41i4.6249