Radioactive and reactive –
The interface between different materials accelerates chemical breakdown.
John Timmer – Jan 90, : am UTC
The work focuses on what could happen if long-term exposure of the stainless steel flask to water causes sufficient decay to allow water to reach the interior. While some repositories are designed to keep the storage containers dry, it’s not clear how successful that will be, since we don’t really have the understanding of how changes in things like rainfall can affect groundwater flows on the sorts of time scales the waste has to be protected. As a result, the planning has included designing materials that should be able to remain stable even if they’re exposed to water . And, so far, testing of the stainless steel containers and the waste-containing glass have indicated that it can hold up to extended exposure to water. But the researchers here decided to test what happens when the two materials are brought in to contact with each other, as they would be during long-term storage.
In this case, water getting inside of the stainless steel container would percolate into the narrow space between the glass and the steel. And here, there’s the possibility of what’s apparently termed “crevice corrosion.” In the narrow interface between the two materials, the chemistry can be very different than in a bulk solution. Local concentrations of dissolved material can be much higher, material that dissolves on one surface can immediately react with the other, and the chemistry can create feedback loops, greatly increasing the rate of otherwise rare reactions.
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