Science: Things that go bump in Nevada: Plans for a nuclear dump are beset by problems, says Philip Richardson

Two hundred feet into the side of a mountain in Nevada, scientists from the US Department of Energy are having a first look at rocks that could ultimately make or break one of the most expensive rubbish dumps in the world.

Yucca Mountain, on the edge of a former nuclear test site, 90 miles north-east of Las Vegas, has been the subject of intense debate since the early Eighties when it was earmarked as the ultimate resting place for radioactive waste from the US civil nuclear power programme. The State of Nevada, from the Governor down, sees no reason why the waste from nuclear power stations in the eastern US - there are none in Nevada itself - should be dumped there. But in 1987 Congress amended its 1982 Nuclear Waste Policy Act, narrowing from three to one the number of sites to be investigated as a potential repository.

The state has done everything within its power to slow down work, from denying drilling permits to preparing a scientific critique of the programme. The Nuclear Waste Project Office - state-based, but federally funded - has run a parallel geological analysis of the site's suitability. Meanwhile the US Department of Energy (DoE) has spent at least dollars 1bn on the programme. The final decision on the site, however, may be many years and billions of dollars away - dollars 6.5bn (pounds 4.4bn) at the latest estimate.

In June, the American nuclear industry started legal action to force the DoE to fulfil its obligations to 'take title' to all the spent fuel from the civil nuclear industry by January 1998. Because of delays in siting a repository, the DoE had intended to develop an interim store for the spent fuel where it would be held in monitorable and retrievable form before disposal. No volunteer community, however, has yet been found where a store could be built. Utility commissioners say there is now a waste management crisis - no repository, and nowhere to put the spent fuel after 1998.

Last year, in a move closely paralleling the planned rock characterisation facility at Sellafield in the UK by Nirex, the nuclear industry's waste disposal company (for which a formal planning application was submitted last Friday), the DoE began to excavate a chamber in the side of Yucca Mountain as the first stage in the construction of an experimental study facility (ESF). The aim is to examine the rock formation selected for repository development.

Even before work had begun, however, there were doubts about the site's suitability. Yucca Mountain is close to volcanic centres, and is criss-crossed by more than 30 faults, many of which have caused recent earthquakes. A previously unknown fault, only 7 miles from Yucca, produced a quake measuring 5.8 on the Richter scale in June 1992, causing dollars 1m worth of damage to the DoE's field offices. Another fault, the Ghost Dance, may have a fractured zone associated with it as wide as 300 yards, which has forced a redesign of the facility. And a third, previously unknown, fault - Sundance - possibly 200 yards wide, could reduce the available repository block by as much as 20 per cent.

There are other uncertainties. Is it a good idea, for example, to pack the spent fuel so close as to maintain the rock at a temperature of over 100C for thousands of years, to drive off any water?

It is therefore no surprise that the Nuclear Waste Technical Review Board has warned the Energy Secretary, Hazel O'Leary, the Senate and Congress that an urgent review of the whole programme by an independent panel is necessary. Protesters fear that the ESF tests will hardly have begun before the DoE begins the site licensing process for Yucca Mountain.

The combination of scientific uncertainty, undue haste and associated uncertainties of programme funding, have combined to mean that the Ghost Dance fault, among others, may yet come to haunt the DoE and its much criticised Office of Civilian Waste Management.

The writer is a freelance consulting geologist who has recently returned from a visit to the Nevada site.

(Photograph omitted)