AFTER $10 billion spent, countless papers and a large helping of controversy, are we any closer to knowing whether Yucca Mountain in the Nevada desert offers a secure resting place for America鈥檚 nuclear legacy?
For two senior geologists, the debate is over and it鈥檚 time to forge ahead. Last week, Isaac Winograd and Eugene Roseboom, who did pioneering studies of nuclear storage in the 1980s, argued that the project should proceed, albeit cautiously, with a pilot facility followed by staged expansion over several decades (Science, vol 320, p 1426). They are not the first to suggest this 鈥� a urged a similar approach five years ago 鈥� but are they right?
Congress selected Yucca Mountain as a proposed underground repository in 1987 because of its arid and remote location, mostly within a nuclear test site. Less than 20 centimetres of rain falls each year, so the water table lies 300 metres below where the repository would be built, safely beyond any risk of contamination. Some have argued that the water table may sometimes rise, but Winograd says that theory 鈥渉as been put to rest鈥�.
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Doubts over the region鈥檚 stability are tougher to refute. The crust in southern Nevada is being pulled apart, creating faults that could one day allow magma to seep into the repository. Yucca Mountain itself is made of rock only 10 million years old, and some studies say a volcanic structure 15 kilometres away formed only 78,000 years ago. More eruptions 鈥� not to mention earthquakes 鈥� are possible, but nobody knows when or where they might occur and there is disagreement over the risk.
Winograd and Roseboom complain that policy-makers seek a level of certainty they simply cannot provide. 鈥淔rom a geological point of view, there are no sure bets,鈥� says Brian Evans of the Massachusetts Institute of Technology, who supports the idea of a test facility. Yet four years ago, a US appeals court ruled that construction cannot go ahead unless the waste can be secured for several hundred thousand years.
For all Yucca Mountain鈥檚 faults, Winograd, Roseboom and many other geologists consider it a lesser evil than the surface storage sites now being used, which are vulnerable to accidents or sabotage. Some 60,000 tonnes of high-level waste are spread among 72 reactor sites, many near cities, and all next to a river, lake or ocean.
They may get their wish, as the Department of Energy this month asked the Nuclear Regulatory Commission for a licence to build the repository. The NRC is examining the 8600-page application to decide whether it is complete enough to warrant full three-year scrutiny.
Meanwhile, anti-nuclear activists and opponents of Yucca are ready for a long scrap. Many of them have clout: one US senator from Nevada, Harry Reid, holds the powerful post of Senate majority leader. The scientific debate may have run its course, but the political fight is only just getting started.
