Thoughts on Holdup Measurements and Their Uncertainty

Holdup measurements are challenging, in part, because they arenot performed in a controlled environment such as a laboratory.They do not present standardized containers, the measurementgeometry is uncontrolled, and they are generally performed innuclear material process areas surrounded by unknown anduncontrolled backgrounds. Holdup measurements are often consideredan art. Alternatively, they can be considered an underdeterminedmathematical problem. Either way, these characteristicsindicate that it may be difficult to reliably estimate holdup measurementuncertainties.One should first consider the definition of holdup. It hasbeen defined as undeclared inventory, in-process inventory, aresidue remaining after cleanout, or the process contents beforecleanout and recovery. While this presentation is pretty muchindependent of which definition is used, specifically it addressesthe other factors in estimating holdup measurement uncertainty,clearly much confusion or error can result from a discussionbetween two parties with different definitions of nuclear materialholdup.