“We’re considering a mechanical remedy,” said Maxcine Maxted, the site’s spent fuel program manager, during a presentation last week to the SRS Citizens Advisory Board.
The white, stringy “cobwebs” were first observed in October 2011 among fuel assemblies submerged 12 to 17 feet in the site’s L Area basin, where aging nuclear materials from foreign and domestic research reactors are stored and guarded.
An assessment concluded it was “biological in nature” and had infested about 7 percent of the 3.5-million-gallon basin.
“Of course it’s really not a cobweb, and it’s not from a spider,” she said, adding that genetic tests of samples found about 3,000 different kinds of bacteria.
In recent months, observers noticed areas where the cobwebs were removed for sampling have not become reinfested.
“At this point, it’s not increasing,” she said. “The spots where we vacuumed up samples are not coming back.”
The simple remedy, she said, might be to just physically remove the material.
Although rare, bacterial colonies have been observed in a few nuclear environments, including a Canadian reactor and at Three Mile Island in Pennsylvania, where a growth developed in the site’s spent fuel basin after its 1979 accident.
“This material is still different, though, because nobody’s ever seen it in a stringy structure,” Maxted said. “But we now know it’s not growing or spreading.”