The Transport of Micron-Sized Particles Through Short Capillaries

The leak testing of containers for radioactive material is a time-consuming process, particularly since very low gas leakage rates have to be detected in order to demonstrate compliance with the regulations (IAEA 1985). The assessment of airborne particulate (aerosol) releases across seals is avoided by achieving such low leakage rates that the assumption can be made that particles do not pass through the widest conceivable pathway. In practical terms, a leakage rate of 1 o-6 Pa m3s-1 is equivalent to a single orifice of 0.25 J..lffi diameter (Burgess et al., 1989). It is desirable to test containers to an acceptance criterion that is equivalent to a leakage pathway at least ten times this size, since such leakage can be detected using simple-to-use pressure rise or fall methods, and corrections for temperature variations during the much shorter test duration can be reduced or even avoided altogether.