Scientists at the Savannah River Site say they are trying to figure out how bacteria is growing in an underwater tank used to hold spent nuclear fuel rods. Last year, operators said they found what looked like cobwebs growing inside the pool at the site’s L-Basin. After getting a sample, the scientists at Savannah River National Laboratory said they now believe the “webs” are actually bacteria colonies.
“Operational personnel observed some weird-looking stuff on top of the fuel racks,” said Christopher Berry, the senior technical adviser for Savannah River Nuclear Laboratory. The laboratory and other facilities at the site are operated by Savannah River Nuclear Solutions (SRNS), which has an Energy Department contract.
He said the bacteria consisted of previously unknown DNA sequences, ”I won’t give you a percentage, but there were a number of sequences that were just not in the database.” However, he added that even a traditional soil sample will often find previously unrecorded DNA sequences.
Berry said the bacteria do not appear to be having a negative effect on the pool or rods so far. No corrosion has yet been detected. But he says officials want to be rid of it just the same. The problem is that the bacteria are believed to feed on carbon— which is not supposed to be in the tank.
Berry said the focus right now is to find that food source, because the problem will not be fixed otherwise. “(We) want to remove the material. If they remove the material and they don’t remove the food source, this will crop up again.”
Researchers don’t currently know where the carbon is coming from, says SRNS spokesman D.T. Townsend, “If it was just murky water that had been sitting there for decades, we could understand there could be a food source, but it’s just the opposite,” he told South Carolina Radio Network, “This is extremely purified water… It’s quite a mystery.”
He adds it could be carbon from the air hitting the water’s surface or material which had slowly accumulated in the pool since its construction in the 1960s. However, Townsend added that neither possibility would explain why the growth had only appeared in the past 11 months.
While rare, there have been examples of bacteria growing at other nuclear fuel sites. In fact, after the original report went public in January, operators of a Canadian plant informed SRNS officials they had encountered a similar problem in one of their storage pools. In that case, the growth began clogging the pool’s filter and the Canadian operators had trouble seeing the fuel rods until they put hydrogen peroxide in the tank to kill the bacteria.
Berry says the growth at Savannah has been at a much slower rate. He adds the American pool also uses a different type of filtering system that should not be affected by the bacteria.
The 2 million gallon pool at Savannah River Site holds old nuclear fuel rods that were mostly used for research purposes at the site.