Radiochemical analysis of a sample of mixed uranium–plutonium nitride fuel

An isotope dilution mass spectrometry overview: tips and applications for the measurement of radionuclides

“…103,104 A wide range of U-series geochemistry applications to the Earth sciences was thoroughly summarized in "Uranium-series Disequilibrium, Applications to Earth, Marine and Environmental Sciences". 105 The uranium and thorium decay-series contain radioactive isotopes of many elements (in particular, 234,235,238 U, 230,232 Th, 231 Pa, 226 Ra and 227 Ac) with varied physicochemical properties leading to a fractionation (mainly elemental fractionation) within the chain in different geological environments during geochemical processes. The accurate measurement of these radionuclides and more specically their elemental ratios (i.e., 230 Th/ 238 U, 238 U/ 232 Th, 231 Pa/ 235 U, 226 Ra/ 230 Th) allows the investigation of processes occurring on time scales from a hundred years to ∼600 000 years.…”

“…To this end, radionuclide concentrations are accurately determined in environmental samples by ID-MS. It is worth mentioning that isotopic compositions (i.e., 234 U/ 238 U and 230 Th/ 232 Th) are also mandatory for disequilibrium studies, however this topic will not be addressed in this section, as it does not fall under the scope of ID-MS.…”

“…Recently, a new high purity 229 Th ( 230 Th/ 229 Th = 5.18 × 10 −5 and 232 Th/ 229 Th = 3.815 × 10 −4 ) reference solution was commercialized by the National Institute of Standards and Technology (NIST). 36 This spike is ideal for measuring samples with very low 230,232 Th content (i.e. young carbonates, etc.).…”

“…The 228 Ra fraction can be used directly aer its separation from 232 Th 120,121,147 or the 232 Th solution is puried from Ra ( 226,228 Ra) and then the puried thorium solution is set aside, and 228 Ra grows in through 232 Th decay. 148 As 226 Ra (impurities of 230 Th 0 226 Ra) grows much more slowly than 228 Ra, at the beginning of 232 Th decay (some months or years) a high 228 Ra/ 226 Ra ratio suitable for ID-MS can be obtained. The 228 Ra spike concentrations were calibrated against certied 226 Ra solutions (i.e.…”

“…Bias in this half-life value will affect the accuracy of the results. Production of a new 229 Th reference material certied by mass spectrometric measurements 36 in combination with the publication of coherent values for 229 Th half-life [193][194][195][196] have enabled the development of uranium age dating with the 230 Th- 234 U chronometer.…”