Equilibrium status of naturally occurring 226Ra with radon daughters and estimation of 238U activity from 235U using natural radioactivity ratio of 238U/235U in soil around Rawatbhata, Rajasthan

Equilibrium status among 226Ra and radon daughters was studied in soil samples around Rawatbhata, Rajasthan. It was found that the increase in radioactivity of 214Bi (radon daughter) due to complete radon buildup in the sealed container is within 15% which establishes that 226Ra remains in equilibrium with radon daughter in soil of Rawatbhata. Radioactivity of 238U was estimated from the radioactivity of 235U using natural uranium isotopic radioactivity ratio (238U/235U) of 21.5. 238U radioactivity in soil was found in the range 25.8–49.5 Bq/kg with an average of 36.7 Bq/kg which is comparable to the global average of 35 Bq/kg.