Development of a 147Pm source for beta-backscatter thickness gauge applications

This paper describes a method for the preparation of 147Pm sources, utilized in the determination of graphite coating thickness on the inner surface of the zircaloy cladding tube of nuclear fuels. 147Pm was adsorbed on a limited surface area [1.5 mm (ϕ)×2 mm (l)] of a cylindrical aluminum rod [1.5 mm (ϕ)×10 mm (l)]. In brief, the selected tip area [1.5 mm (ϕ)×2 mm (l)] was anodized at a current density of 15 mA/cm2 at 15 °C in 3 M·H2SO4 for 2 h followed by immersion of this area in 10 μL of 147Pm solution containing 37 MBq (1 mCi) of activity at pH 6.0 for 24 h. The radioactive area was subsequently covered with a thin layer of Polymethyl Methacrylate (PMMA) to prevent leaching of 147Pm from the source. The quantity of incorporated 147Pm activity was assayed in a calibrated ion chamber. Quality control tests were carried out to ensure nonleachability, uniform distribution of activity and stability of the sources.