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Deadline extended to apply for ANS's 2023 ANS Congressional Fellowship
The deadline for applications to the ANS's Glenn T. Seaborg Congressional Science and Engineering Fellowship has been extended. All ANS members are invited to apply to help the Society fulfill its strategic goal of informing nuclear public policy.
All applications and supporting documents are now due by 11:59 p.m. (EDT) on Monday, May 23.
Robert B. Hayes
Nuclear Technology | Volume 197 | Number 2 | February 2017 | Pages 209-218
Technical Paper | dx.doi.org/10.13182/NT16-98
Articles are hosted by Taylor and Francis Online.
Some quality considerations for use in isotopic dating are presented to identify and correct heretofore unidentified overestimate scenarios. These include to a lesser degree the statistical interpretation issues with linear-least-squares fitting results but more importantly the isotope effect in the individual components of the isochron coefficient ratios. By taking into consideration the isotope effect (differential mass diffusion rates) when measuring isotopic ratios from very old samples, the distribution dependency in the coefficient ratios will cause a bias if isotopic diffusion rates are not identical throughout a sample. The isotope effect is that isotopes having a smaller atomic mass will diffuse faster throughout a medium than will their heavier counterparts causing concentration gradients of their ratios even when there are no contributions from radioactive decay. The application to Rb/Sr dating is evaluated and shown to result in expected age overestimates when isotopic ratios are employed to linearize the isochron. A suggested method to test for this effect is argued to require rigorous statistical analysis. An associated optimal sampling technique would involve using single-grain etching. It is also shown that the only method to fully eliminate the isotope effect is to not use isotopic ratios at all in radioisotopic dating as the physics do not require the use of isotopic ratios for geochronological dating. However, without the ratios, the data are inherently noisy.