A new design of 238Pu activity sources for use in intercomparison exercises

In the framework of a BIPM 238Pu comparison exercise, a new design for α-radiation counting sources was developed. These sources are constructed with a gold-coated Vyns film stretched over a stainless-steel disk. To improve the crystallization of the radioactive salt, the physical properties of the gold-coated polymer surface which receives the radioactivity deposit is modified. A pad of polystyrene micro-spheres (Estapor® K-007) mixed with a wetting agent (Tween 20®) is directly electrosprayed before the radioactive drop is deposited. After hot air-drying, the source is finally sealed with a thin Vyns film covering the entire radioactive spot. This new design makes it possible to create 238Pu sources that are easy and safe to handle, homogeneous and stable during ageing.