Groud water plutonium spurs more research

The discovery of plutonium from a nuclear blast under the Nevada Test Site that traveled in ground water for almost a mile has prompted the federal government to increase spending for contamination research.

Scientists at Lawrence Livermore and Los Alamos national laboratories did not expect to find radioactive plutonium in the ground water.

They discovered plutonium in well water almost a mile south of a 1968 underground nuclear blast, surprising experts on the extent of ground-water contamination.

Department of Energy researchers say in an article in the current issue of the scientific journal Nature that they suspect the plutonium hitched rides in the ground water attached to tiny particles, known as colloids.

"We argue that colloidal ground-water migration must have played an important role in transporting the plutonium," Annie Kersting of Lawrence Livermore and five co-authors of the paper wrote.

"The present work thus demonstrates that plutonium is not immobile in the subsurface, but can be transported over significant distances," the scientists concluded.

Federal scientists believed for years that plutonium stayed inside a nuclear blast's crater, trapped by the molten rock. Clay and other types of Southern Nevada's soil were also suspected of capturing the radioactive particles, which have a half-life of 24,500 years. That means that half of the plutonium remains radioactive after 24,500 years.

Plutonium does not pose a threat of to human health outside the body. However once inside, a speck inhaled into a lung can create a tumor. Plutonium can also create cancer inside the body's other organs, including blood, because it remains radioactive for so long.

Kersting and her colleagues discovered that 98 percent of the plutonium remained inside the crater, but the rest reached below to the ground water in the northwest corner of the Test Site, where 828 underground nuclear tests occurred from 1956 to 1992.

The question is how much plutonium can move on those tiny particles, Kersting said.

The radiation is moving toward the Amargosa Valley, southwest of the Test Site, where farmers grow crops and raise milk cows, raising great concern, DOE spokeswoman Nancy Harkess said.

"We want to protect the public and the workers from exposure to radiation," she said.

The DOE has continued to test the two wells sampled by the scientists who discovered the plutonium movement, Bob Bangerter, the Test Site's Under Ground Test Area project manager, said.

"The levels of plutonium are the same," Bangerter said. The DOE will continue to sample the wells this year, since scientists suspect ground water flows south and west from the Test Site.

Congress approved an extra $6 million to the Test Site's environmental cleanup budget, Bangerter said. Six more wells will be drilled for testing this year.

The migrating plutonium could raise serious questions for nuclear waste disposal.

The DOE is studying Yucca Mountain, 90 miles northwest of Las Vegas, for a national high-level nuclear waste repository. The government has already spent $2.2 billion in 15 years of research there. Department scientists have said that ground water will not seep into the repository and carry contaminated wastes away before 10,000 years.

Plutonium migrating at Yucca Mountain is a different story, Bangerter argued. The underground nuclear weapons blasts exposed the ground water to radiation, but Yucca Mountain would be built above the water table and use engineered barriers such as strong containers to prevent radiation from contaminating the environment.

Bob Loux, executive director of the Nevada Agency for Nuclear Projects, disagreed with the DOE's conclusions. "The fact they can't change is the very fast ground-water travel time at the site," he said.

The DOE's own viability assessment, a recent report card to Congress, says that within 500 years, ground water will invade the repository, Loux said. "Under DOE's own regulations, if ground water moves into the site in less than 1,000 years, that disqualifies it as a nuclear waste repository," he said.

The scientific evidence clearly indicates Yucca Mountain cannot contain the wastes because it is riddled with 34 earthquake faults and thousands of smaller cracks, Loux said. "The sooner they admit the site is not suitable, the sooner the country can find a good site and stop wasting money," he said.

In addition, the DOE failed to consider that Yucca Mountain has a wetter climate, Loux said. More rain and snowfall could invade the nuclear repository within hundreds of years.

However, said Bruce Honeyman, a professor at the Colorado School of Mines, contaminating the environment with plutonium hitchhiking on particles is difficult. He urged further study to determine if the plutonium rode the particles or if some other process caused the movement of radiation in the Test Site's ground water.

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