Variation of radiation level and radionuclide enrichment in high background area

Significantly high radiation level and radionuclide concentration along Quilon beach area of coastal Kerala have been reported by several investigators. Detailed gamma radiation level survey was carried out using a portable scintillometer. Detailed studies on radionuclides concentration in different environmental matrices of high background areas were undertaken in the coastal areas of Karunagapalli, Kayankulam, Chavara, Neendakara and Kollam to study the distribution and enrichment of the radionuclides in the region. The absorbed gamma dose rates in air in high background area are in the range 43-17,400nGyh^-1. Gamma radiation level is found to be maximum at a distance of 20m from the sea waterline in all beaches. The soil samples collected from different locations were analysed for primordial radionuclides by gamma spectrometry. The activity of primordial radionuclides was determined for the different size fractions of soil to study the enrichment pattern. The highest activity of ²³²Th and ²²⁶Ra was found to be enriched in 125-63μ size fraction. The preferential accumulation of ⁴⁰K was found in <63μ fraction. The minimum ²³²Th activity was 30.2Bqkg^-1, found in 1000-500μ particle size fraction at Kollam and maximum activity of 3250.4Bqkg^-1 was observed in grains of size 125-63μ at Neendakara. The lowest ²²⁶Ra activity observed was 33.9Bqkg^-1 at Neendakara in grains of size 1000-500μ and the highest activity observed was 482.6Bqkg^-1 in grains of size 125-63μ in Neendakara. The highest ⁴⁰K activity found was 1923Bqkg^-1 in grains of size <63μ for a sample collected from Neendakara. A good correlation was observed between computed dose and measured dose in air. The correlation between ²³²Th and ²²⁶Ra was also moderately high. The results of these investigations are presented and discussed in this paper.