A Uranium Adsorbing Alginate Polyacylonitrile Membrane With Superior Regeneration Performance.

[NNadir]

7. As I indicated last night in post #6, the ratio is apparently a ratio of ratios, displacement from secular equilibrium.

From the full text of the paper:

The reproducibility and the reliability of the U isotopic analyses were tested by periodic determination of the HU1Ustandard supposed to be at secular equilibrium, i.e., (234U/238U) 51.

It would have been better if they'd listed at such in the table.

The value at secular equilibrium is simply the ratio of the decay constants, which is simply the ratio of the half-lives, 5.50 X 10^-5.

A discussion of displacement from secular equilibrium in seawater and other matrices is found in this open source paper: Hsun-Ming Hu et al. Sub-epsilon natural 234U/238U measurements refine the 234U half-life and U-Th geochronology. Sci. Adv.11,eadu8117(2025). The table therein is labeled better.