Can Algae Clean Up Nuclear Waste?

Issue 5 and Volume 115.

Researchers from Northwestern University and Argonne National Laboratory have a better understanding of a common freshwater alga and its ability to remove strontium from water. Insight into this mechanism could help scientists design methods to remove radioactive strontium from existing 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 roughly 80 million gallons of radioactive waste stored in the United States.

The researchers show how Closterium moniliferum, one of the bright green algae often seen in ponds, sequesters strontium in the form of barium-strontium-sulfate crystals. Researchers are using this understanding to think about a practical sequestration system for nuclear waste that maximizes strontium removal.

Possibilities include using the algae for direct bioremediation of waste or accidental spills or designing a new process for waste treatment inspired by how the algae work.

Even though strontium 90 doesn’t appear to be a big environmental threat following Japan’s nuclear accident, the radioactive isotope will need to be dealt with during cleanup, researchers said.

The algae’s ability to separate strontium from calcium occurs when the crystals are formed inside the cells. The algae first soak up barium, strontium and calcium from their watery environment. Strontium then is sequestered along with barium in the crystals, which remain in the cells, while the calcium is excreted from the cells. (Barium must be present for the organisms to take up strontium.)

The researchers varied the amount of barium and strontium in the algae’s environment and then measured the amount of strontium taken up into the cell. They found the ratio of barium to strontium in the water affected the amount of strontium incorporated into each crystal. Depending on the medium’s composition, the strontium measured in a crystal ranged from less than 1 percent to 45 percent. This gives the researchers an avenue for making the process more strontium-selective.

Putting the “Sol” in Soldier 

The National Renewable Energy Laboratory (NREL) and the Defense Advanced Research Projects Agency are teaming up with universities and private companies to perfect an advanced solar cell designed to be smaller and more efficient than existing cells.

Such a solar photovoltaic (or PV) panel would be tiny enough to be built into different types of portable electronic equipment, yet powerful enough to deliver a sufficient current for charging.

To achieve this, scientists are bringing together several revolutionary concepts. The cell they envision would have different layers of PV materials, each producing an optimum amount of electricity from portions of the light spectrum. It would be topped by a lens that would concentrate the amount of sunlight directed on the PV materials.

“By drawing upon several of the most important innovations in PV design and combining them into an entirely new concept for cell design, we believe we can leapfrog over the limitations that had long been assumed for efficiency, size, cost and other critical factors,” said Dr. Mark Wanlass, principal scientist at NREL.

“The new device we are looking to develop could not only solve many of the limitations our soldiers today encounter with electronics in the battlefield,” Wanlass added, “it may spur other new solutions for solar power in space, and eventually, for our homes and businesses here at home.”

The military finds it advantageous for many reasons to use solar cells to charge batteries. Being able to reliably charge batteries reduces the number of spare batteries needed. From a logistical standpoint, that means fewer trucks, helicopters and planes to ferry stocks of batteries into the field.

For individual soldiers, it can mean as much as a 20-pound decrease in the field supplies they must carry. The result would be an armed force that is more efficient and more environmentally sustainable.

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