Revision of nuclear data of .sup.235U and .sup.226Ra for the 186-keV gamma-ray peak for the determination of activity in environmental samples

In this work, the ratio contribution of .sup.226Ra and .sup.235U in [gamma] spectra with the latest update nuclear data will be revised. The results showed that in the total count rate of the 186 keV peak consists of 57.2% of .sup.226Ra (186.2 keV) and 42.8% of .sup.235U (185.7 keV) with the existence of equilibrium. These calculations were used for determining mass activity of .sup.238U for the direct and fast measurement using only the 186 keV peak and verifying the .sup.238U-.sup.226Ra secular equilibrium. An equilibrium method was measured secular equilibrium of decay chain .sup.238U (by the product daughter .sup.214Bi-609.3 keV) that was used for this study. The maximum relative deviation was less than 4.0% between both methods proved the direct method was reliable and can be applied to determine the mass activity of .sup.238U in the radioactive equilibrium samples.