The AL-R8 stainless steel sealed insert that is currently used for interim storage of plutonium pits at the Pantex facility in Amarillo, Texas, is designed to provide an inert storage environment for the plutonium pits for a 50-year service life. There is concern that the high chlorine content and absorbed moisture present in the packaging material, Celotex, may lead to corrosion of the container over time. The main objective of this study was to determine chlorine in the Celotex as well as in the various leaching procedures using neutron activation analysis.