PNNL

Abstract

The Pacific Northwest National Laboratory (PNNL) conducted inspection and cleaning activities at two radionuclide air-sampling systems that continuously monitor radioactive air emissions from research and development (R&D) facilities. The inspection and cleaning was performed to evaluate effective methods and potential cost impacts of maintenance requirements in the revised American National Standard Institute (ANSI) standard Sampling and Monitoring Releases of Airborne Radioactive Substances from the Stacks and Ducts of Nuclear Facilities (ANSI/HPS N13.1-1999). The standard requires at least annual inspections of sampling systems followed by cleaning if deposits are visible. During 2001 and 2002, inspections were performed leaving the sampling systems in place and inserting videoscope cables into different access points to allow viewing of the inside and outside of sampling manifolds and transport lines. Cleaning was performed on one of the systems by disconnecting and extracting the sampling manifold, then washing it with de-ionized water and scrub brushes. The wash water was analyzed for radioactivity and solids. Results of the inspection showed greater deposition in one of the systems than would be expected by a High Efficiency Particulate Air (HEPA) filtered exhaust stream; the second system was also downstream of HEPA filters and appeared much cleaner. The videoscope was a useful and cost-effective tool and provided a better view than could be obtained with the naked eye. However, because even small amounts of deposition were made visible with the videoscope, clarification is needed in defining when probe washing is merited, particularly in existing sampling systems whose design is not conducive to easy removal and cleaning.