The use of k0-NAA for the determination of the n(235U)/n(238U) isotopic ratio in samples containing uranium

TLDR: In this article, a reverse perspective of the problem, the observed 235 U-fission and 238 U activation products along with the k 0 -factors were used to obtain information about the n ( 235 U)/ n ( 238 U) 1 isotopic ratio in the samples.

Abstract: In the analysis of rare earth elements in samples containing uranium by k 0 -neutron activation analysis fission of 235 U was considered an undesired phenomenon until the “fission k 0 -factors” were introduced to account for natural-U fission interferences. In this work, by using a reverse perspective of the problem, the observed 235 U-fission and 238 U activation products (along with the k 0 -factors) were used to obtain information about the n ( 235 U)/ n ( 238 U) 1 isotopic ratio in the samples. The relevant formulae and data-filtering algorithm were implemented in a home-made computer software, allowing automated evaluation and selection of unbiased data. Two radioisotopes ( 131 I and 140 La) were demonstrated to be reliable candidates for n ( 235 U)/ n ( 238 U) determination in environmental samples. The accuracy of this method was determined using several isotopic standards varying from a depleted to a highly enriched 235 U content. An overall 2.31±0.03% overestimation of the isotopic ratio was observed (within 95% confidence level).