In a repository for spent nuclear fuel, gas generated by corrosion of theiron in the canister may form small bubbles that will escape and rise to theground surface. Colloidal particles may attach to the surface of the bubblesand be carried by them. If the colloids are supplied by the montmorilloniteclay of the buffer material surrounding the canister, the clay can becarried away. Nuclides sorbed in the clay can be carried with the bubbles.We have estimated the carrying capacity of the gas of the clay particles andthe escape rate of nuclides carried by the gas bubbles. The latter is alsocompared to the escape rate by the conventional escape mechanisms from thenear field. We have further estimated the detachment of the nuclides fromthe clay and their sorption onto the fracture surfaces of the rock as wellas their uptake by diffusion into the rock matrix along the bubble transportpaths.

The present paper is speculative and uses some hypothetical assumptions.Although the processes that are modelled are known to exist there is notenough known of several of them to quantify them accurately. The carryingcapacity of the gas used in the calculations is an upper bound and probablyvery much exaggerated. Even so, the consequences are minor for the releaseof radionuclides.