How dangerous are these crystals, then?

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ResearchBlogging.orgRecently I came across a very interesting article on the website of the German magazine Der Spiegel, which informed me that the current way of storing highly radioactive waste was unsuitable, and the reason for this is chemical. Says there:

Now a US-German research group, in an Article in Angewandte Chemie, raises doubts about the basic principle of storage.

Except that they don’t. The paper is about certain actinide borates with rather complicated structures and interesting properties – basic research with a lot of crystallography. Creating the borate compounds was inspired by a method of storing nuclear waste – very active materials are melted into glass rods and enclosed in a steel container. Depending on the condition, some actinides form crystals within the glass. Not much is known about these crystals, except that they appear to be actinide borates.

After the experiments a little more is known about the structures and properties compounds, which is obviously very good. Additionally, one of the prepared crystals is highly unusual in that it contains three distinct oxidation states of Neptunium with three distinct coordination spheres for the basic NpO2-unit, including one which is entirely surrounded by other NpO2-oxygens. Take a look at it if you get the chance.
But I don’t get how this is at all related to the Spiegel article. One of the scientists apparently claims that the results of this research imply that the radioactive glass rods will crack upon contact with water, probably due to swelling of these borates. Actinide borates do have a layered structure that may take up water, but this is hardly a new discovery. Also, the paper doesn’t mention any experiments in this direction and makes clear that the scientists even set out to avoid the conditions under which the crystals in the glass rods form.

So even if the cited scientist, Dr. Depmeier, told the journalist all the things in the article, there is nothing whatsoever in this paper to substantiate the alleged doubts about the basic principle of storage. And this annoys me no end.
In Germany, the long-term storage of nuclear waste has been a hot topic for decades. The reason is that the government years ago decided to deposit the stuff in an old salt mine, because salt is geologically very stable and particularly impervious to water. Or something like that.

Anyway, they always assured the people that the radioactive waste was safe down there. Until, well, it turned out that it wasn’t and now a few million tons of nuclear waste are slowly drowning in ground water. We are in enough trouble as it is. The last thing we need is people throwing outlandish claims around.

Wang, S., Alekseev, E., Ling, J., Skanthakumar, S., Soderholm, L., Depmeier, W., & Albrecht-Schmitt, T. (2010). Neptunium Diverges Sharply from Uranium and Plutonium in Crystalline Borate Matrixes: Insights into the Complex Behavior of the Early Actinides Relevant to Nuclear Waste Storage Angewandte Chemie, 122 (7), 1285-1288 DOI: 10.1002/ange.200906127

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One Response to “How dangerous are these crystals, then?”

  1. Thomas Albrecht-Schmitt Says:

    Lars,

    I am glad that you wrote this article. You are correct that we are doing basic research to undercover the structures and properties of actinide borates. While the works was partially inspired by the potential presence of actinide borates in vitrified waste, the compounds that we made are very exotic. The take home message from the article is that the chemistry of neptunium can not be predicted based on studies with uranium or plutonium. You are correct that nowhere in our article did we extrapolate from our work to what will happen with actual glass logs.

    Thomas Albrecht-Schmitt

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