Leak-Testing to Demonstrate Retention of Particulates

Packages designed to contain radioactive materials for transport or storage must be shown to be leak-tight to certain standards. Tests are performed to demonstrate compliance with these standards before acceptance for despatch or storage. The standards depend on the form of the radioactive contents and the potential hazards from the release of the isotopes concerned. Fluid (liquid or gas) leak rates can readily be assessed by evaluating flow rates from measured pressure drops. Solid matter will normally only leak in the form of particles entrained in the fluid stream but assessment of particle concentrations is not practical as an operational procedure. This problem is avoided by achieving such low leak rates that solid particles cannot pass through the largest conceivable leak path. Further difficulties are encountered in following this route, however. It may be difficult to achieve the desired low leak rate; measurement to demonstrate achievement may require costly and sensitive equipment and may be time-consuming; the interpretation of hole size and particle size distributions may leave some uncertainty.