Following a damning report on Dounreay by two government expert committees last month, surveys of the site have detected widespread radioactive contamination, some of which may have lain undetected since the Fifties.
Grassy verges by roads and footpaths contain highly radioactive particles, outside the "active" areas where people are routinely monitored for contamination. Half a dozen areas have now been roped off as the UK Atomic Energy Authority (UKAEA) works out what to do.
The site's manager, John Baxter, drafted in a team of specialists to survey offices, workshops and employees' homes for radioactivity. One of their first tasks was to survey the canteen and the area outside it before a staff barbecue on 4 July. No loose contamination was found there.
However, more than 20 radioactive particles were found by a site roadway as workmen were replacing streetlights. The particles appear similar to those found contaminating the foreshore after an explosion in a nuclear waste shaft in 1977.
But Dounreay managers believe the particles in the roadside verges fell off a lorry, rather than coming from the 1977 explosion. Mr Baxter said that from the Fifties to the Seventies, radioactive waste was transported within the site in unsealed flasks and these may have scattered radioactive debris.
Mr Baxter stressed that the contamination on the chair was much lower level activity than the beach particles or those found in the verge. However, officials do not know how long it has been there, because they cannot find records showing if the offices have ever been surveyed.
Lorraine Mann, spokesperson for Scotland Against Nuclear Dumping (Sand) said: "It gives a whole new meaning to the phrase 'atomic piles'." She said the site could not be effectively cleaned up as it was: "They should close it down and get a safety team on to do the job effectively."
Last month, the Committee on the Medical Aspects of Radiation in the Environment and the Radioactive Waste Management Advisory Committee issued a joint report on pollution of the beaches at Dounreay which was highly critical of past Dounreay managers. It said the UKAEA had not done enough work to discover the source of the contamination and had failed to pass on to the committees relevant information about the work they had done.Reuse content