Scientist warns of volcano threat to Yucca

Friday, Nov. 17, 2000 | 11:16 a.m.

RENO -- The greatest radiation risk to people for the 1,000 years after a proposed high-level nuclear waste repository at Yucca Mountain is sealed would come from volcanoes, a Nuclear Regulatory Commission consultant said Thursday.

While such a catastrophic event is unlikely to occur, it would have dire consequences if it did -- both from ash and lava, Brittain Hill, senior research scientist at the Southwest Research Institute in San Antonio, Texas, told scientists at the Geological Society of America meeting.

Yucca Mountain, 90 miles northwest of Las Vegas, is the only site being considered as a dump for the nation's 77,000 tons of high-level nuclear waste. If it is found scientifically suitable, a repository 1,000-feet below the desert floor could start accepting shipments as soon as 2010.

The closest volcano, Crater Flat, is about 10 miles southwest of Yucca Mountain. It last spewed ash less than 80,000 years ago, Hill said.

In addition, a volcanic eruption likely would push Yucca's rock out of the way, and lava would seek a crack or fracture to head to the surface and possibly enter the repository on the way.

If deep, hot magma invaded the repository, an estimated one to 10 nuclear waste containers would probably release their radioactive contents, Hill said.

In contrast, the DOE's Greg Valentine of Los Alamos National Laboratory in New Mexico told fellow scientists that no buried containers are expected to fail for more than 10,000 years. The Department of Energy's worst case shows one to three casks failing in a volcanic event.

In order to earn a license from the Nuclear Regulatory Commission to operate a repository, the DOE must weigh the risks of a possible explosive eruption from nearby volcanoes.

The DOE is taking volcanic risks seriously. Nuclear waste containers will not be placed near known faults, and burial packages will be designed to withstand rockfalls during volcanic eruptions or earthquakes, spokesmen for both the DOE and the NRC said.

Scientists expect a Crater Flat volcano, if it erupts, to be violent. Geologic evidence of violent eruptions lies less than 1,000 feet away from the western repository boundary at Yucca Mountain, Hill said.

Hill, who has done volcanic research in Arizona and Nicaragua, said 90 percent of the radiation exposure to an Amargosa Valley farm, 12 miles from the eruption, would arrive in the ash erupting from a future volcano.

Near Nicaragua's volcanoes, 300,000 people live and breathe erupting ash, Hill said. The particles are irritating, but they are not radioactive.

"It's having pieces of high-level nuclear waste that creates the problem," he said.

However, the volcanic radiation exposure, calculated at 1 millirem per year, fits within a radiation repository standard of 15 millirems set by the federal Environmental Protection Agency, Hill said. The NRC proposes a total radiation exposure limit of 25 millirems.

In addition to people inhaling the radioactive particles for up to 100 years after a volcanic disruption, ash on the surface of the ground could flow down Forty-Mile Wash to U.S. 95, posing a radiation threat to people for up to 1,000 years, Hill said.

The particles could re-enter the atmosphere in Southern Nevada's winds, then be inhaled by travelers, Yucca Mountain workers and nearby residents, he said.

For 10 years independent scientists have been studying similar eruptions all over the world as consultants to the Nuclear Regulatory Commission.