MIT team finds that the ratio of component atoms is vital to performance.
A side trip on the recent EAPS field course to Yucca Mountain in Nevada provided the students with a first-hand view of the government's proposed nuclear waste site.
"Safe disposal of the high-level radioactive waste accumulated over the last 50 years is a problem whose solution must combine geology, engineering, and politics," said Sam Bowring, associate professor of geology, who led the field course. "It's important that students as citizens become aware of the scientific issues behind radioactive waste decisions."
Yucca Mountain is part of the test site used in the 1950s for nuclear weapons. The area being considered for storage of the nation's civilian nuclear waste, chosen by Congress in 1987, is 3,500 feet above sea level but 1,500 feet below the summit of the mountain. It is now under further study to confirm its suitability, according to John Peck, the guide for the MIT group and a geologist with Science Applications International Corp., one of the federal government's contractors.
The area has very low rainfall (four to four and a half inches per year) and a low water table-factors that will make it more likely that the buried waste will not be disturbed and carried through the water system.
In determining suitability, geologists also need to understand the history of movement along faults that cut across the proposed site and also to determine the probability of eruption of basaltic volcanoes near Yucca Mountain. The selected repository must be safe for 10,000 years, according to Department of Energy guidelines.
At this point in the government's studies, according to Mr. Peck, the site seems to be passing the suitability tests. Although the questions raised about tectonic, volcanic and groundwater dangers are not entirely answered, the possibility that they will make the site unsuitable is small, he said. It seems to be within the range of acceptability of the NRC.
The government is now in the process of digging a five-mile tunnel 25 feet in diameter to continue site studies. The students arrived at the digging site just at the point when only the very rear of the tunnel borer-the same type used in digging the "Chunnel" under the English Channel-was visible as it buried itself in the ground.
Currently, scientists and engineers on the project are grappling with two questions, Mr. Peck told the students: whether areas of cracked and broken-up rock will make the site unsuitable and whether the tunnel support required by geologic fractures would make the project too expensive.
A final decision on the site is expected to be determined by 2005, making 2010 the earliest that nuclear waste could be interred there.
A version of this article appeared in MIT Tech Talk on March 1, 1995.