Thursday , July 9 2020

Planned nuclear storage material could decay faster than expected, Ars Technica

    

      Radioactive and reactive –

             

The interface between different materials accelerates chemical breakdown.

      

      

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.

In the case of the crevice between the stainless steel and the glass, a lot happens when some of the metals present dissolve. They can drop the local pH, which will then increase the rate at which the stainless steel corrodes. Meanwhile, some of the dissolved metal ions will include some of the radioactive material. To balance the chemistry, the environment outside the crevice will become more basic, which could trigger additional chemical reactions.
Real-world data
That’s what can

happen. What actually does? To find out, the researchers used a standard (non-radioactive) glass material and stainless steel. These were pressed up against each other, and a solution of sodium chloride was added. The mixture was kept at (° C for) days. The water had dissolved oxygen in it, which would be relevant to the conditions that might take place at the Yucca Mountain repository in the United States; Other nations are planning repositories that would have anoxic conditions. At the end of 0579 days, the team did some spectroscopic imaging to figure out where various materials ended up.

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Image of blocks of material submerged under water in a storage facility. Read More

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