Corrections for the Emission Probabilities of the Intense Gamma Rays from 238U and Applying them to Uranium Isotopic Analysis

Gamma-ray emission probabilities of 235U and 238U have been studied extensively. While the gamma-ray emission probabilities for 235U are well known, the emission probabilities for 238U differ widely from one study to another. Our study indicates that one of the causes of the large discrepancies in the studies may be due to the true coincidence summing of many gamma rays from the decay of 238U daughters. The intensities of some of the intense gamma rays of 238U compared with the others were reduced by as much as 16% when the 21-mm-thick U3O8 samples were moved from 15 cm to putting them in contact with the detector. With better knowledge of the gamma-ray emission probabilities and understanding the summing effects of specific gamma rays, the isotopic concentration of uranium can be better analyzed. The results of the isotopic analysis using fixed energy response function analysis with multiple efficiencies (FRAM) with the summing correction are presented in this paper.