The conditioning of nuclear waste that some states like France plan to bury deep underground does not take into account an interaction between certain compounds that could accelerate their degradation, warns a study published on Monday.
In several countries, including France, which has the second largest fleet of reactors in the world, the most radioactive ultimate waste is packaged in blocks of crystallized glass poured into stainless steel cylinders. This vitrification is intended to ensure the confinement of radioactivity in the very long term for materials which can be radioactive for tens of thousands of years.
Accelerated corrosion
A study led by the American University of Ohio, published in the journal Nature Materials , highlights the fact that the corrosion of glass or ceramic used to confine this waste is "significantly accelerated" under certain conditions. "It is unexpected. Until now, it was considered that stainless steel was inert, that it would eventually oxidize despite its name, but that vis-à-vis the glass which contains radioelements it played no role, "said one of the study's authors, Stéphane Gin, researcher at the French Atomic Energy Commission (CEA).
Over a long time, whatever the deep storage place, the water always ends up filling the voids, note the researchers. Under these conditions, the corrosion of the steel is accelerated, itself accelerating the degradation of the glass and the risk of release of the radioactive elements.
This acceleration is "significant," said Xiaolei Guo, the study's lead author, in a statement. "This indicates that current models may not be sufficient to guarantee the safe storage of this waste," he added. But the study does not give any figures on the time from which the packages could become problematic.
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