Heat is on for scientists testing at Yucca Mountain

Tuesday, Dec. 9, 1997 | 11:27 a.m.

Scientists turned the heat way up inside Yucca Mountain last week in the world's largest experiment of its kind at the site of a potential national nuclear waste dump.

Located in Alcove 5 of the 5-mile exploratory tunnel beneath Yucca Mountain, the gigantic heater test, called a drift-scale experiment, will help scientists answer how the volcanic rock performs if hot irradiated fuel buried for thousands of years ever goes into the mountain.

"Data collected from the drift-scale and other heater tests will be used to refine the computer models used by scientists to understand the effects of long-term heat generation on the rock that makes up the potential repository area beneath Yucca Mountain," said DOE geophysicist Robert Yasek.

This is a major field test nearly 1,000 times larger than a similar, smaller single heater test, he said.

"It will be the largest test of its type done thus far in the world," Yasek said.

Yucca Mountain, located 90 miles northwest of Las Vegas, has not been declared safe yet. Even when the U.S. Department of Energy announces its suitability next year, that does not mean it can receive waste. The assessment is a report required by Congress.

For Yucca Mountain to take commercial and defense wastes, the DOE must apply for a license from the Nuclear Regulatory Commission. That process will take years and a dump cannot open before 2010.

The heating experiment allows scientists to study how heat flows through the rock, examine changes as the rock deforms with heat, check water movement as it heats up and cools down, and examine the chemistry of the rock and water.

A sealed part of Alcove 5 about 156 feet long is being electrically heated.

Computer models predict that more than 13,000 cubic yards of surrounding rock in the alcove will be warmed to a temperature above the boiling point of water using 50 wing heaters and nine canister heaters similar to waste containers.

Video and infrared cameras will visually monitor the test during the expected four years of heat up and then a similar length of cool down within the mountain.

Instruments and sensors installed in boreholes surrounding the drift will measure heat, mechanics, water and chemical changes in the rock.

Over the past five years, heater testing has moved from laboratory to large-scale field tests such as the newest one.

A large block test and single heater test are ongoing at Yucca Mountain as well.

The large block test is underway at Fran Ridge -- an area next to Yucca Mountain -- in part of the potential host rock, exposed at the surface. The test started in February 1997 and will end its heating phase in January.

This test is investigating the effects of heat on a 10-by-10-by-15-foot block of rock carved with a large saw. Five 9-foot electrics heaters were placed in the block, covered by insulation and vapor barriers.

Once the heaters are turned off, scientists will gather data on how the rock reacts to high temperatures and cooling. Once cooled, the block will be carefully broken apart for further analysis.

The single heater test, which began in August 1996 and is being conducted in Alcove 5, will end in February.

A single electric heater inserted in a borehole warmed 30 cubic yards of insulated rock to a temperature above water's boiling point. More than 300 thermometers monitored the rock's temperature. This test is in its cooling phase.

DOE's Lake Barrett, acting director of the Office of Civilian Radioactive Waste Management, said the heater tests show scientific studies at Yucca Mountain are making progress.

"Nuclear waste disposal is one of the premier challenges our nation faces," Barrett said.

The administration believes geologic disposal is the appropriate solution not only for commercial spent nuclear fuel management, but also for the cleanup of the nation's weapons complex and the disposal of weapons-grade material to prevent nuclear proliferation, he said.

"The start of this test is further evidence that the department has under way an aggressive site characterization program that has made significant progress over the past four years," Barrett said.