Literature Survey: A Survey of Open Literature On Process Holdup of Special Nuclear Materials

The residual amount(s) of fissionable materials remaining in process equipment after the runout of bulk materials processed is referred to as "Process Holdup of Special Nuclear Materials." Locating regions of holdup and estimating the quantity of fissile materials remaining as holdup are important not only to materials accountability but also to process safety. Holdup is often referred to as a "Hidden Inventory." In materials accounting terminology, hidden inventories are part of "Materials Unaccounted For" (MUF) or "Inventory Difference" (ID). MUF or ID could be construed as "Loss" or "Diversion." From a safeguards perspective, all these designations are undesirable. Another terminology that is relevant to holdup is "In-Process Inventory." During process operations and temporary shutdown, the holdup within the facility is also known as the in-process inventory. Estimating this inventory is just as challenging as residuals after process runout.