ANOTHER 20 potentially lethal particles of radioactive waste have been found lying around the Dounreay nuclear complex in Scotland in the past month. The finds have so incensed environmental groups that they are pressing for the site to be closed for “cleaning”.
But, unlike the 150 particles found on the foreshore next to Dounreay over the past 18 years, the 20 latest particles did not originate from the explosion in 1977 which blew the lid off a waste shaft, spewing its radioactive contents around the site. Instead, according to the UK Atomic Energy Authority (UKAEA), they fell off the back of a lorry on its way to the waste shaft more than thirty years ago.
In a fax to staff last week, Dounreay’s director, John Baxter, revealed that the particles had been found “buried in the grassy roadside verges” at “several places on the site”. Although he gave no specific figures on radiation levels, he said that the particles were “sufficiently radioactive that they could be harmful to health if inhaled, swallowed or held close to the skin for long periods”. They were “similar”, he said, to those found on the foreshore, some of which were hot enough to kill within days (This Week, 24 June).
Baxter suggested that the particles fell onto the roadside during the 1960s and early 1970s when radioactive material was being carried in trailers to the waste shaft. He expressed concern that they had lain undetected since then, but insisted that the risk of workers encountering any of them was “low”. He said that all the particles had been removed and promised “swift action” to check the rest of the site.
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The particles, which are typically a millimetre across and contain uranium, aluminium, caesium and plutonium, were originally part of fuel elements used in Dounreay’s Materials Testing Reactor in the 1960s. Swarf from milling the elements was poured into small, screw-top cans which were transported in open containers to the waste shaft. In a report published last month, the government’s Radioactive Waste Management Advisory Committee (RWMAC) blamed a huge explosion in the shaft in 1977 for releasing the 150 particles which contaminated the foreshore.
In addition, the RWMAC says there are “a much larger number of particles” contaminating the ground around the top of the shaft. The UKAEA is still studying the precise distribution and concentration of these particles. The RWMAC points out that the UKAEA only began to discover significant numbers of particles on the Dounreay site recently – after the RWMAC had begun to investigate the problem.
But a spokesman for Dounreay, Ian Shepherd, stresses that comprehensive monitoring of the site started last autumn as part of a multimillion pound programme to decommission two fast reactors and their associated plants. He says that it is “quite possible” that other particles would be found. “What happened long ago is not for us to explain but we are left to find the remedies,” he told New Scientist.
The monitoring has also uncovered hitherto unknown radioactive contamination on several other parts of the site. Barriers have been erected around areas near a reactor and other fuel cycle areas to prevent workers being exposed to “light or moderate” contamination. In two places, drain covers were found to be contaminated.
The latest finds have prompted environmentalists in Scotland to call for a halt to the reprocessing of nuclear fuel at Dounreay while the site is cleaned up. The UKAEA has rejected this, and it is lobbying for a large expansion of its reprocessing business. The authority is hoping that the US will allow it to reprocess up to 9000 fuel rods from European research reactors. The highly enriched uranium in these rods came from the US, which oversees the fate of all its fuel.
