UPF Data Book: A Resource for Standard Data, Dimensions, Equations, and Practices used at UPF for Nuclear Criticality Safety Analyses

A new Uranium Processing Facility (UPF) is being designed at Y-12 in Oak Ridge to replace the existing facilities. As part of this design, new and existing processes need to be evaluated using Criticality Safety Process Studies (CSPS) to ensure they remain subcritical for both normal and credible abnormal conditions. This requires a great many sets of calculations using both MCNP and SCALE to model the various configurations, concentrations, and processes being designed. At UPF these calculations are contained within Design Analysis and Calculation (DAC) documents. Without a standard guide different nuclear criticality safety (NCS) engineers were modeling the same system using parameters familiar to them from past experience. Often this resulted in significantly different assumptions on things such as: materials, uranium enrichment, reflection conditions, and maximum uranium concentrations for calculations in DACs supporting essentially the same process but in a different CSPS. It became apparent that, for DACs to be useful for more than the CSPS they were written to support, a common set of guidelines, for use by all NCS engineers, was needed. A Data Book DAC is now used at UPF to help standardize the common UPF system parameters used for all calculations. This makes it possible to use existing calculations from one CSPS in another CSPS having similar processes. It also simplifies the requirements imposed by NCS on things like pipe diameters, tank size and spacing, and component placement on the design and process disciplines. Finally, for a given parameter, once it is determined the parameter is valid for a UPF process it becomes valid for all similar processes without the need for further calculational analyses. (authors)