Low Flow Filter Efficiency Testing

The nuclear industry relies heavily on air filters in waste drums, bag-out bags, respirators and storage containers to contain plutonium particulates while allowing hydrogen gas to escape. The flow rate design requirements for filters used in these applications can be as much as five to seven orders of magnitude lower than those used in large confinement ventilation systems. Furthermore, the testing protocols and standards for filter efficiency measurement at high flow rates are relatively well defined compared to those for low flow rate systems. In addition, the measurement of filter efficiency at low flow rates presents some unique challenges. This paper will describe some of these challenges, as well as the low flow filter efficiency testing equipment used at Nuclear Filter Technology and that under development at Los Alamos National Laboratory (LANL) for acceptance and surveillance testing.