They were particularly critical of computer models of groundwater flow in the area, which they said were 'inconsistent' with observations in the field. Nirex, the industry's waste disposal company, has used these models to predict that water would seep out into rock deep under the Irish Sea.
But Sir John Knill, chairman of the Government's Radioactive Waste Management Advisory Committee (RAWMAC), said it was 'just as conceivable' that groundwater would flow up from the volcanic rock in which the waste would be buried, through the sandstone above it and onto the surface.
The flow of water around the burial site is a vital safety issue because of the risk that this might leach radioactive chemicals into drinking water supplies. 'A few years ago we thought Sellafield would be a simple site, in fact it is incredibly complex,' Sir John said at the London launch of the committee's annual report yesterday.
If the committee's analysis proved correct, government regulators would not allow the repository to go ahead, Sir John warned. 'We will ultimately see a repository built in Britain. Whether it is at Sellafield is a different matter. Clearly there are major questions that need answers,' he said.
The emerging picture of the hydrogeology of the area implied that Nirex would have to pay far more attention to the physical and chemical containment of its waste, Sir John said.
RAWMAC found that not only do the Nirex computer models fail to agree with what is seen on site, but they also make predictions that contradict basic physical laws. One shows lower-density freshwater moving downwards into higher-density brine.
Sir John said another six or seven years of research were needed to get a clear understanding of groundwater movement in the area. Nirex may have to drill yet another deep borehole, adding to the time and money spent on the repository. Research into the site has already cost over pounds 300m.
A second report published yesterday, following a three-year study by a research student for the environmental group Friends of the Earth, was also critical of Nirex and said the company plans to compromise public safety and build the repository by 2010. It claimed Nirex had over-simplified the chemistry of the real world in its computer models.
A Nirex spokesman said Sellafield remained its preferred site, although it is prepared to look elsewhere. Nirex hopes to build a pounds 200m underground rock laboratory to provide more information and expects to apply for planning permission in a few weeks time.
14th annual RAWMAC report; HMSO; pounds 10.
Out of their depth - the inadequacies of Nirex research on the safety of nuclear waste disposal; FoE; pounds 12.Reuse content