Engineering study of the criticality issues associated with Hanford tank 241-Z-361

Tank 241-Z-361 is associated with the Plutonium Finishing Plant (PFP). Uncertainty about the contents of the tank have led to the declaration of an Unreviewed Safety Question (USQ) and the preparation of a Justification for Continued Operation (JCO) to address flammable gas and other authorization basis issued. A Criticality Safety Team was assembled to review old data, determine its validity, and reevaluate the tank. It was concluded that the tank has a sufficient margin of safety to allow opening, sampling, and other characterizing activities. The team concluded that a criticality in Tank 241-Z-361 was extremely unlikely