Abstract
One material attribute for nuclear forensics is material age. (241)Pu is almost always present in uranium- and plutonium-based nuclear weapons, which pose the greatest threat to our security. The in-growth of (241)Am due to the decay of (241)Pu provides an excellent chronometer of the material. A well-characterized (241)Pu/(241)Am standard is needed to validate measurement capability, as a basis for between-laboratory comparability, and as material for verifying laboratory performance. This effort verifies the certification of a 38 year old (241)Pu Standard Reference Material (SRM4340) through alpha-gamma anticoincidence counting, and also establishes the separation date to two weeks of the documented date.