Bacteria make nuclear waste safer

Bacteria could make underground nuclear waste deposits safer, new research has revealed. Scientists discovered that the bacteria could increase safety by consuming hydrogen.

A new study has discovered a microbial community made up of seven species of bacteria that live hundreds of meters underground in the rock layers that host Swiss nuclear waste.

Scientists at the EPFL in Lausanne revealed that the bacteria could increase the safety of nuclear waste repositories by consuming hydrogen that accumulates as the steel canisters containing the waste corrode.

It takes some two hundred thousand years for the radioactivity of nuclear fuel to revert to the levels of naturally occurring uranium. As a result, most research into the long-term safety of nuclear waste disposal focuses on the mechanics of the rock layers that make up the storage site, explained the Swiss university in a statement.

However, biology is also a key factor in safe waste disposal, according to Rizlan Bernier-Latmani, senior author of the new study. She explained that bacteria would pounce on any available energy source, saying: “In water samples from 300 meters underground at the Mont Terri Rock Laboratory, we unearthed a community bacteria forming a closed food chain. Under pristine conditions, the species at the bottom of this bacterial food chain get their energy from hydrogen and sulfate from the host rock, powering the remaining species.”

Adding nuclear waste changes the conditions altogether. Although the waste is vitrified, or sealed in steel canisters, the inevitable corrosion of the steel canisters leads to the production of hydrogen gas.

Five years ago in the field, the researchers subjected underground bacteria to increased hydrogen levels. They monitored the composition of the bacterial population and how they changed, noticing that once the bacteria had consumed all the available oxygen and iron, there was a shift in their population numbers and metabolism. Both were driven by the increased availability of hydrogen gas.

To make nuclear waste repositories safer, Bernier-Latmani proposes adding a fourth, biological, engineered barrier. Research is ongoing.

Photo credit: Alex Hesse/ CC BY 2.0

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