The accurate evaluation of the absolute intensity (I%) of the gamma-ray transition 1001.03 keV of 234mPa is crucial for accurate determination of 238U in nuclear material and environmental samples. Over the last decades, a wide range of 1001.03 keV absolute intensity values were published by different researchers and ranged from 0.59 to 1.12 %. Nowadays, one of the most commonly used values is 0.847±0.008 % that seems not accurate and would eventually lead to an overestimation of 238U activity concentration.

In this study the commonly used f-value for the 1001.03 keV (0.835 ± 0.004%) energy transition of the
234mPa was re-evaluated due to an obvious consistent overestimation of the 238U activity concentration.
Different calibration protocols, samples’ matrices and geometries, and gamma-ray spectrometers were
exploited in order to assure the accuracy of the derived data. An average positive relative bias of about
24% from the currently used f-value was estimating leading to newly adopted f-value of 1.037 ± 0.052%.