Bacteria feast on nuclear waste

Ground water might be at risk

By Ed Susman
UNITED PRESS INTERNATIONAL

ORLANDO, Fla.—It seemed like a science-fiction scenario: Nuclear scientists announced here that bacteria in salt mines, the storage place of choice for nuclear waste, thrive on radioactive materials.

And these contaminated bacteria are small enough to slip into ground water.

Betty Strietelmeier, a researcher from the Los Alamos National Laboratory in New Mexico, said the short-term risk to the population is small.

"However, it's very hard to predict what will happen in 10,000 years, the projected lifetime of the storage facilities. We did our experiments for a month," said Miss Strietelmeier, who presented her work last week at the fall meeting of the American Chemical Society in Orlando.

Scientists at Los Alamos are combining microbiology and radiochemistry to investigate what could happen to bacteria that come in contact with radioactive waste in a nuclear waste repository.

Miss Streitelmeier found that exposure to radioactive plutonium, neptunium, uranium, thorium and americium did not kill the halophiles—salt-loving bacteria that abound in salt environments.

"If anything," Miss Streitelmeier said, "the bacteria growth was enhanced." The bacteria adsorb the radioactive material—pull the radioactive substances out of the waste material.

Work of colleagues at Los Alamos, Sandia National Laboratories in Albuquerque and at Brookhaven National Laboratory in Upton, N.Y., found that most bacteria would be filtered out of ground water, but smaller bacteria—particularly the halophiles—could be carried off by ground water.

Miss Streitelmeier's work was done in a laboratory setting. In a waste storage facility, she said there could be differences in levels of toxicity or in levels of bacteria. "We don't know how long the bacteria would live carrying the radioactive material," she noted.

She said that bacteria would most likely stick to rock, barrels or the waste itself and would not slip into ground water; and if radioactive bacteria did get into ground water, she said the organism would soon die and the radioactive particles would break into smaller and smaller pieces.

But Miss Streitelmeier acknowledged that radioactivity is a potent generator of mutagens that could cause the bacteria to become more efficient transporters of nuclear contamination.

"It could be a scary scenario," she said.

The studies are part of the extensive scientific evidence required to demonstrate that the U.S. Department of Energy's Waste Isolation Pilot Plant (WIPP) is safe before the Environmental Protection Agency allows the site near Carlsbad, N.M., to accept waste from the nations nuclear weapons laboratories.