Natural uranium comprises of 238U (99.28%) and 235U (0.71%), which are both radioactive. These nuclides have long decay chains consisting of radioactive daughters that radiate numerous particles and gamma rays. The gamma emitting progeny of 238U are therefore also present in natural material and the decay chain would not necessary be in secular equilibrium. This is especially true if the soil were disturbed by anthropogenic activities, like mining. The most prominent daughter in the decay chain of 238U is the long lived radium (226Ra) nuclide. Gamma rays from the bismuth (214Bi) daughter of 238U are generally utilised to estimate uranium concentrations,under condition that secular equilibrium exist in the decay chain. 226Ra is however before 214Bi in the uranium decay chain and the measurement of the 214Bi gamma rays therefore provides a better estimation of 226Ra concentration than that of 238U, especially when secular equilibrium is uncertain. This study will therefore refer to 226Ra concentrations rather than of 238U concentrations, but still keeping in mind the underlying relationship
between these nuclides.