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What are the Risks?

There are three main areas of concern with regard to potential long-term radiation exposure from Yucca Mountain: because of earthquakes, volcanic activity, or through aqueous pathways.

One potential risk is that Yucca Mountain is in known seismically active area. The Department of Energy has identified more than 80 suspected faults and fault ruptures within 100 km of Yucca Mountain. 38 of these have the potential to produce earthquakes of a magnitude of concern¹. However, the DOE does not consider seismicity a significant risk factor, because of the low probabilities of occurrence².

A second area of concern is the volcanicnature of Yucca Mountain. Although the principal volcanic eruption which created most of the landscape was over 11 million years ago, the most recent volcanic activity occurred 9,000 yearsago³. The Department of Energy did consider the risk of magma from a volcanic event to either to directly in

tersect the structure itself or to interfere with the pathways the radioactive material might take once escaped from the facility. However, the DOE only estimated the risk of volcanic problems at about 1.5x10-8 per year⁴.

The most likely source of radioactive material leakage is through water flow. Although the facility is located 1000 ft (300 m) below the surface and 1000 ft above the water table, water infiltration is still the most significant concern. It is believed wate will percolate through the walls of the repository and therefore mix with wastes. The radioactive material will then be mixed into the groundwater. Because Yucca Mountain only receives about 6 inches of rain per year (170 mm), and most of this is washed off the mountain or absorbed by plants, waste is not expected to be released through this method for thousands of years⁵. Some are concerned, however, with the possibility of increased rainfall with climate changes. The DOE has also proposed adding drip shields to prevent water from getting into the waste containers.

The two pathways of potential ingestion are through water and through air Source

However, to receive approval from the Nuclear Regulatory Commission, the DOE must only prove that it can meet the standards under normal conditions and under the possibility that a "human intrusion" occurs. For example, if a well is dug that influences the pathways of the radioactive material⁶. In all, the public must not be exposed to more than 15 millirem of radiation per year. This standard must be met for the next 10,000 years.

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