He and SF(6) as tracers for determining ventilation rates of high-level radioactive waste tanks

British Nuclear Fuels pie ( BNFL) manages and operates facilities associated with all aspects of the nuclear fuel cycle including the reprocessing of spent nuclear fuel at its Sellafield site, located in the north of England. Over the past 40 years, a number of liquid and solid wastes have been generated as a result of these activities. These wastes are safely managed in a raw form within a series of silos and stores located above ground at Sellafield. A number of major plants have been, or are being, constructed to safely and efficiently condition these wastes into a form that will facilitate their continued safe on-site storage, with their eventual safe transport and long-term storage in a deep underground waste repository planned by Nirex, the UK radioactive waste disposal agency. This paper briefly describes the evolution of a strategy for the recovery and treatment of approximately 16 000 m(3) of intermediate-level waste accumulated in storage ponds and silos at the Sellafield site during the past 40 years of active operations, focusing on the Sellafield drypac plant (SDP) process. It will also identify some key lessons learned on previous major capital projects at Sellafield and how these have been applied to the SDP.