Uranium isotope abundance ratios in natural uranium metal certified reference material 112-A

► The 234U/238U and 235U/238U isotope-amount ratios in natural uranium metal certified reference material 112-A and CRM 145 are characterized. ► The 235U/238U ratios from two analytical techniques (total evaporation and modified total evaporation) are in agreement. ► Uncertainties in the CRM 112-A 235U/238U and 234U/238U ratios are calculated following the GUM. ► The certified isotope abundance ratios are in excellent agreement with the values obtained in the IRMM measurement campaign. ► Traceability of the measured isotopic ratios with SI units and with US nuclear reference materials is established through the use of CRM U030-A.