Combination of a filter and a material permeable to gases but impermeable to liquids

In combination with a container for containing radioactive material, wherein the container vents gases to the atmosphere through an opening in the wall of the container, a filter element comprised of an activated carbon or carbon-carbon composite disposed in the opening of the container with a first surface facing into the container and a second surface interfacing the atmosphere to which the container vents for filtering out radioactive material from vent gases passing from the container, through the filter element and to the atmosphere;

• a layer of material completely covering the second surface of the filter element, the material being impermeable to liquid and permeable to vapor thereby allowing filtered vapor to vent from the container while preventing liquid water from entering the container through the filter element.