Comment on 'Excess 234U: an aging effect in confined waters' by J. Kronfeld, E. Gradsztajn, H.W. Mueller, J. Radin, A. Yaniv and R. Zach

In a recent paper by Kronfeld et al., a strong isotopic fractionation between 234U and 238U has been reported to occur in oil well brines. It is argued that the excess 234U was produced by alpha-recoil 234Th ejected into the liquid during a period of 'many half-lives' of 234U in which these waters were isolated and thus expected to reach isotopic equilibrium. It is for this reason that Kronfeld et al. prefer the alpha-recoil 234Th over the previously suggested mechanism of preferential leaching of 234U. This comment is intended to show, that (1) the Ramallah No. 1 well waters, on which Kronfeld's et al. findings are based, are essentially mud filtrates which were routinely used during the drilling of this well, and (2) that the reported excess of 234U in these waters could also be explained by a preferential leaching mechanism of this isotope from the surrounding rocks. (Auth.)