CHARACTERIZATION OF TANK 241-Z-361

This paper describes how engineering inputs were incorporated into detailed plans, reviewed, approved, and subsequently implemented at the DOE Richland (DOE-RL) Hanford Site, near Richland, Washington. Nuclear safety aspects are emphasized; specifically, the use of projectspecific safety basis documentation (regulatory requirements are discussed in the companion papers). An out-of-service sealed underground settling tank (241-Z-361) within the security perimeter of the Plutonium Finishing Plant (PFP) was identified as a known potential hazard. Potential hazards initially identified were: degraded structural integrity, explosive concentrations of flammable gas in the vapor space, chemical instability, and poorly defined nuclear criticality characteristics. The tank contains approximately 70m 3 of plutonium bearing sludge, with a plutonium content estimated at 30 kg. The paper discusses the processes leading up to, and the safe venting and sampling in 1999, of Tank 241-Z-361. BACKGROUND