Estimation of radiological risk due to concentration of 238U, 226Ra, 232Th and 40K in soils of different geological origins in northern India

Radioactivity of nuclides 238 U, 226 Ra, 232Th and 40K was measured in soil by γ -ray spectrometry using a HPGe detector. A criterion was set in order to analyse soil samples from plain, semi-hilly and hilly areas in northern India. More than three γ -ray energy peaks were used for the determination of 226 Ra and 232Th activity concentrations to obtain more accurate results. Some of these peaks have interfering energies, which was caused by the limited resolution of the detector, but they were resolved theoretically and used in the analysis because of their significance in reducing the random error to its minimum level. Relationships between the measured radionuclides have been discussed elaborately. Radionuclides 238U and 226 Ra were found in disequilibrium with ratio of specific activities ( 238 U/226 Ra) less than unity for most of the samples. In some cases this disequilibrium may be significant enough to modify the γ -ray dose factors.