TY - JOUR
T1 - Uranium isotope abundance ratios in natural uranium metal certified reference material 112-A
AU - Mathew, K.
AU - Mason, P.
AU - Voeks, A.
AU - Narayanan, U.
PY - 2012/4/1
Y1 - 2012/4/1
N2 - Certified reference material (CRM) 112-A, uranium metal assay standard, with "natural" U isotopic composition and CRM 145, uranium assay standard solution made by dissolving CRM 112-A metal were analyzed using TRITON Thermal Ionization Mass Spectrometer (TIMS) to characterize the uranium isotopic abundances. The certified 235U/ 238U "major" ratio of 0.0072543 (40) in CRM C112-A and CRM 145 is determined using the total evaporation (TE) and modified total evaporation (MTE) methods. In the MTE method, the total evaporation process is interrupted on a regular basis to allow correction of background from peak tailing, internal calibration of the secondary electron multiplier (SEM) detector versus the Faraday cups, peak-centering, and ion source re-focusing. For the "minor" 234U/ 238U and 236U/ 238U ratio measurements using MTE, better precision and accuracy are achieved compared to the TE analyses. The certified 234U/ 238U ratio of 0.000052841 (82) in CRM C112-A and CRM 145 is determined using a conventional analysis technique that incorporates an internal mass bias correction utilizing the measured 235U/ 238U ratio and correction for peak tailing from 235U and 238U. The 236U/ 238U isotope abundance ratio in CRM C112-A and CRM 145 is estimated to be <5 × 10 -9. The CRM 112-A and CRM 145 materials show no evidence for any statistically significant unit-to-unit variations in uranium isotope abundance ratios. The homogeneity of both CRMs is established. The measurements leading to the certification of uranium isotopic abundances are discussed.
AB - Certified reference material (CRM) 112-A, uranium metal assay standard, with "natural" U isotopic composition and CRM 145, uranium assay standard solution made by dissolving CRM 112-A metal were analyzed using TRITON Thermal Ionization Mass Spectrometer (TIMS) to characterize the uranium isotopic abundances. The certified 235U/ 238U "major" ratio of 0.0072543 (40) in CRM C112-A and CRM 145 is determined using the total evaporation (TE) and modified total evaporation (MTE) methods. In the MTE method, the total evaporation process is interrupted on a regular basis to allow correction of background from peak tailing, internal calibration of the secondary electron multiplier (SEM) detector versus the Faraday cups, peak-centering, and ion source re-focusing. For the "minor" 234U/ 238U and 236U/ 238U ratio measurements using MTE, better precision and accuracy are achieved compared to the TE analyses. The certified 234U/ 238U ratio of 0.000052841 (82) in CRM C112-A and CRM 145 is determined using a conventional analysis technique that incorporates an internal mass bias correction utilizing the measured 235U/ 238U ratio and correction for peak tailing from 235U and 238U. The 236U/ 238U isotope abundance ratio in CRM C112-A and CRM 145 is estimated to be <5 × 10 -9. The CRM 112-A and CRM 145 materials show no evidence for any statistically significant unit-to-unit variations in uranium isotope abundance ratios. The homogeneity of both CRMs is established. The measurements leading to the certification of uranium isotopic abundances are discussed.
KW - Certified reference material
KW - Isotopic abundance ratio
KW - Mass spectrometry
KW - Natural uranium
UR - http://www.scopus.com/inward/record.url?scp=84859555015&partnerID=8YFLogxK
U2 - 10.1016/j.ijms.2012.02.005
DO - 10.1016/j.ijms.2012.02.005
M3 - Article
AN - SCOPUS:84859555015
SN - 1387-3806
VL - 315
SP - 8
EP - 14
JO - International Journal of Mass Spectrometry
JF - International Journal of Mass Spectrometry
ER -