Algae remove strontium from nuclear waste

Researchers from Northwestern University and Argonne National Laboratory have an enhanced understanding of a common freshwater alga and its remarkable ability to remove strontium from water. Insight into this mechanism ultimately could help scientists design methods to remove radioactive strontium from existing nuclear waste.

This common freshwater alga soaks up strontium, whose radioactive isotope is found in nuclear waste.

Strontium 90, a major waste component, is one of the more dangerous radioactive fission materials created within a nuclear reactor. It is present in the approximately 80 million gallons of radioactive waste sludge stored in the United States alone.

The researchers are the first to show quantitatively how Closterium moniliferum, one of the bright green algae often seen in ponds, sequesters strontium (in the form of barium-strontium-sulfate crystals). They are using this understanding to think about a practical sequestration system for nuclear waste that maximizes strontium removal. The possibilities include using the algae for direct bioremediation of waste or accidental spills in the environment or designing a new process for waste treatment inspired by how the algae work.

The results are published by the journal ChemSusChem, a sister journal of Angewandte Chemie.

''Nuclear waste cleanup is a problem we have to solve,'' said senior author Derk Joester, who experienced Chernobyl's radioactive fallout when he was a teenager living in southern Germany. ''Even if all the nuclear reactors were to shut down tomorrow, the existing volume of waste is great, and it is costly to store. We need to isolate highly radioactive 'high-level' waste from 'low-level' waste. The algae offer a mechanism for doing this, which we would like to understand and optimize.''

Even though strontium 90 doesn't appear to be a significant environmental threat following the nuclear accident in Japan, the radioactive isotope will need to be dealt with during the power plant and nuclear waste cleanup, Joester said.