The 238U decay constant (λU-238) is fundamental to radioisotope-based chronometry in the Earth and planetary sciences, yet only a single published λU-238 value (Jaffey et al. in Phys Rev C 4(5):1889–1906, 1971) is widely applied. We have determined λU-238 via the novel approach of measuring of 234Th ingrowth in high-purity 238U solutions, using isotope dilution mass spectrometry (ID-MS). The 234Th decay constant (λTh-234) was measured via decay counting with high-purity Ge (HPGe) γ detectors. Preliminary results for λU-238 agree with the value determined by α-counting within the elevated uncertainty of 0.462% (k = 2). Ongoing efforts to reproduce λU-238 with reduced experimental uncertainties will inform future conclusions.
Parsons-Davis, T. et al. (2018). New measurement of the 238U decay constant with inductively coupled plasma mass spectrometry. Journal of Radioanalytical and Nuclear Chemistry 318 (1), 711-721.