IUPAC

Update and harmonize recommendations on half-lives and isotopic compositions.

The inter-Union project with the International Union of Geological Sciences (IUGS) strives to provide an authoritative recommendation based on a critical reevaluation of data on half-lives and decay schemes of long-lived radioactive nuclides used by the geological and planetary science communities. A specific goal of the project is to reconcile current inconsistencies between values used in geological and planetary sciences on the one hand, and those used in the nuclear physics and chemistry communities on the other.

The project will draw on complementary expertise present in IUGS and IUPAC. Previous work by IUGS (Working Group "Decay constants in geochronology") and IUPAC (Commissions II.1 "Isotopic abundance" and V.7 "Radiochemistry and Nuclear Techniques") will be included, harmonized, and updated. IUGS-IUPAC interaction will be tightened.

Initial work (2006-2008) focuses on 9 nuclides used in geochronology (40K, 87Rb, 138La, 147Sm, 176Lu, 187Re, 232Th, 235U, 238U). Half-lives, decay schemes, and measurement techniques will be critically evaluated, as well as isotopic compositions of parent and daughter elements. Uncertainty analyses need to be adequately reassessed following ISO/GUM procedures. Successive phases will both expand the number of nuclides and refine the isotopic abundances in view of an additional recommendation.

<project announcement published in Chem. Int. Mar-Apr 2007, p. 17>