The Evolution of PMFDs (Process Monitoring Flow Diagrams) at the Los Alamos National Laboratory Plutonium Facilit

Since the mid-1980s, Process Accountability Flow Diagrams (PAFDs) have been used at TA-55 (the Los Alamos National Laboratory Plutonium Facility) in response to a DOE finding regarding Material Control and Accountability documentation of the flow of nuclear material within the facility. The diagrams were developed to represent plutonium processing and currently represent over 40 different Process/Status units (a Process/Status is an increment around which nuclear material accounting and balancing is performed) within the plutonium facility. The name was recently changed to PMFDs (Process Monitoring Flow Diagrams). These documents are schematics or overviews of a process where handling of the nuclear material might incur either a gain or loss. These diagrams include required measurement points, changes in the material through processing steps such as combinations, splits, calcinations, dissolutions, sampling, chemical conversions, chemical separations, etc. The locations of accountability measurements within the process flow are discussed and negotiated with facility operating personnel to satisfy both processing and measurement requirements. The PMFD also provides item descriptions, limited project information and acceptable incoming and exiting process directions. This paper will describe how these documents have changed since their inception, including how they are being used to assist as material control indicators. The PMFDs are used in conjunction with a modernized Nuclear Material Accountability System (NMAS) and are important tools used in drawing a material balance around processing operations. Finally, the strengths of these documents and how their use can be enhanced in the future will be presented as well as some of the possible ramifications of potential future changes