DOE scientists will test how water flows from Yucca

Wednesday, Feb. 18, 1998 | 10:21 a.m.

U.S. Department of Energy scientists will move out of the laboratory and into Busted Butte to see how water and particles might flow through unsaturated rock that mimics a proposed high-level nuclear waste dump at Yucca Mountain.

The DOE is conducting an intense battery of scientific testing at Yucca Mountain, 90 miles northwest of Las Vegas, to determine if it can contain irradiated commercial fuel and highly radioactive waste from defense activities for thousands of years.

The new test can begin after workers finished in January excavating a 220-foot tunnel into Busted Butte, a small hill about three miles south of Yucca Mountain.

The tunnel was drilled through the same rock layers as those in the potential dump site.

The purpose of the Busted Butte study is to provide part of the answer to solve the puzzle about how fast and how far water and particles flow through unsaturated rock.

DOE researchers discovered plutonium from an underground nuclear experiment at the Nevada Test Site rode tiny particles called colloids almost a mile from the bomb's crater, apparently through fractures in the rock. They announced their findings in September during the American Chemical Society meeting in Las Vegas.

Scientists at Yucca Mountain plan to investigate the layer of volcanic tuff sandwiched between the potential repository area and the water table beneath the dump site.

All investigators have today are computer models, said Russ Patterson, technical lead for hydrology and process models on the Yucca Mountain Project.

"The knowledge acquired from these tests will help verify computer models used by scientists to better understand the flow and transport of water in rock beneath the potential repository," Patterson said.

In the next 18 months two parts of the test in Busted Butte will take place. Scientists will inject non-radioactive tracers to mimic transport of radioactive particles through the rock.

Then the DOE will draw 3-dimensional maps from the paths the tracers take within Busted Butte, Patterson explained.

Scientists are trying to find out if the Calico Hills formation acts as a natural barrier to radioactive particles migrating down through the unsaturated zone. If true, this would slow the rate of any potential radioactive releases escaping a future repository.

Authors Luther Carter and Thomas Pigford, a University of California, Berkeley nuclear engineer, said in an article published this week in the Bulletin of Atomic Scientists that much more radiation will escape from Yucca Mountain than current estimates predict. Disintegrating waste containers will allow the radiation to escape from the mountain into more than a 40-mile area.

The DOE's Busted Butte tests will put small-scale laboratory experiments on this issue to the test.

Rock slabs dug from Busted Butte will show where tracers go as they flow through the rock.