U-234/U-235 Activity Ratios as a Probe for the U-238/U-235 Half-Life Ratio

The uranium isotopes U-235 and U-238, because of their long half-lives, have important applications, in particular for nuclear geochronology. The most accurate measurements, by Jaffey et al., have up to now not been confirmed by other measurements of comparable accuracy. Hence, the validity of dating via the uranium-lead system is predominantly dependent on this single experiment. In this work, we supply some additional experimental information on the U235 and U-238 half-lives. High resolution alpha spectrometry was performed on three enriched U-235 materials, containing also impurity traces of U-234. Assuming the U-234 in the material to be in equilibrium with its parent, U-238, it can be used as a probe for the half-life of the latter. Relying on the isotopic composition of the uranium, as determined by mass spectrometry techniques, the ratio of half-lives of U-238 and U-235 was determined via the activity ratio of U-234 and U-235. Preliminary results on one material confirm the half-life ratio within a few tenths of percent. Yet, a discrepancy was detected with another material, which raises questions about the attainable accuracy with mass spectrometry on ultra-low amounts of U-234.

POMME Stefaan;  GARCIA-TORANO E.;  SIBBENS Goedele;  RICHTER Stephan;  WELLUM Roger;  STOLARZ Anna;  ALONSO-MUNOZ Adolfo; 

2008-07-02

SPRINGER

JRC46171

0236-5731,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC46171,   

10.1007/s10967-008-0731-6,