Nuclear waste dump delayed for tests: UK Nirex plans an underground laboratory to check safety of site. Tom Wilkie reports

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THE NUCLEAR industry's waste management company, UK Nirex, yesterday said it was delaying plans to excavate huge underground caverns to take radioactive waste near Sellafield in Cumbria. Instead, the company will first dig a laboratory 650 metres (2,130ft) beneath the surface to check the safety of the site.

But tunnelling industry experts warned that the company's timetable was still too tight. Shafts leading to the 'experimental' rock laboratory would eventually have to be used for heavy duty construction work, to remove spoil during excavation of the repository.

The Government's independent Radioactive Waste Management Advisory Committee welcomed Nirex's plans but also warned that the company was being too hasty. Before Nirex begins to sink the shafts for the laboratory, it should study the flow of underground water by means of boreholes drilled from the surface, the committee recommended.

Knowledge of the natural patterns of underground water flow will be crucial to the long-term safety of the waste repository, but the shafts and the laboratory will disrupt the natural flow. Nirex will apply for planning permission in the middle of next year to sink two shafts each 5m (16ft) across, about 50m (164ft) apart, on farmland owned by British Nuclear Fuels, which operates the nearby Sellafield reprocessing plant.

The chosen spot for the pounds 120m 'rock characterisation facility' is not far from the village of Gosforth, near the north- eastern corner of the underground rock mass which the company believes is suitable for taking radioactive waste.

If Nirex gets the go-ahead it expects to get down to the suitable rocks by early 1996. If the findings confirm its expectations, it expects to submit a planning application for the repository proper by the end of that year and to take the first consignments of waste by 2007.

Reacting to criticism of this tight timetable, Michael Folger, the company's managing director, emphasised that it could be delayed further by aspects outside the company's control. He said: 'We are not looking to telescope anything. We intend to be down there for many years. The key question is when we have sufficient confidence in our safety assessment to go for a planning application. It might be six months or it could be three to four years.'

Mr Folger also revealed that Nirex would be seeking permission to drill eight more boreholes in and around the farmland, before the access shafts were excavated. These would be used to monitor the flow of water deep underground. It would also be sinking a pattern of smaller 'geotechnical' boreholes across the site for the proposed repository.

Coincidentally, the shafts are located in approximately the area which an earlier Nirex design pinpointed for the main vertical access shafts to the repository. Last year, Nirex scrapped that design in favour of sloping spiral tunnels.

Mr Folger said: 'The spiral access route has everything going for it and we would be reluctant to move away from that as the prime route for excavation.'

But, he continued, the company had yet to address the exact sequence of construction. Independent observers with experience in the tunnelling industry said that it was impossible for the company to keep to its schedule 'without pulling the muck up the shafts from the laboratory'.

Mr Folger hopes that wide public consultations over the next six months will assuage local fears about the project and convince objectors that the company is putting long-term safety first.

Constructing the laboratory also reduces the financial risk to the company that it might discover once it got to depth that the rock was really unsuitable. By deferring the main construction phase which will cost about pounds 1bn and concentrating instead on the laboratory, the overall cost would remain the same.

(Photograph omitted)