from New Scientist, 04 June 2007
Scientists have identified a risk of an "uncontrolled chain reaction" at one of the world's largest radioactive waste stores in northern Russia.
According to environmentalists, this could trigger a disaster worse than the accident at the Chernobyl nuclear plant in 1986. But the probability of such a disaster is regarded as very small by regulatory authorities.
"We are sitting on a powder keg with a burning fuse," claims Alexander Nikitin, from the St Petersburg office of the Norwegian environmental group, Bellona. "And we can only guess about the length of the fuse."
Andreeva Bay, on the Kola Peninsula in northwest Russia, is home to 21,000 spent uranium fuel assemblies from nuclear submarines and ice-breakers. But the three huge concrete tanks in which the radioactive waste is stored have begun to corrode and let in seawater.
Critical mass
A study by scientists from three Russian research institutes suggests that salt water could accelerate disintegration of the fuel, splitting it into tiny particles. If the particles reach concentrations of 5-10% in water, it could be dangerous, they say.
"Calculations show that the creation of a homogeneous mixture of these particles with water could lead to an uncontrolled chain reaction," they warn. This kind of accidental critical mass, leading to bursts of radiation and heat, is a well-recognised risk in the nuclear industry, but is not the same as a nuclear explosion.
The Russian study (pdf) has been translated and highlighted by Bellona, which has long monitored safety at Andreeva Bay, less than 50 kilometres from Norway. In the worst case, the group says, such a reaction could ignite a hydrogen explosion, which could shower Europe with radioactivity.
"Real risk"
Per Strand, a director of the Norwegian Radiation Protection Authority, accepts that there is a risk of an accidental criticality. "The probability is low but you can't exclude it," he told New Scientist.
The highest risk would come when the fuel is moved to put it in safer storage, planned over the next few years. "We will have to be very careful," he says. "Many countries are working together to try and solve this unique problem."
John Large, a British nuclear consultant who has visited Andreeva Bay, points out that some forms of aluminium-based fuel stored there were particularly prone to saltwater corrosion. Hydrogen could be released from the fuel, resulting in an explosion and fire, he says.
"The risk is real and serious enough to warrant a study of the potential radiological consequences as these could potentially apply to Scandinavia and north-west Europe," he adds. "But I am doubtful that the keeper of these stores, the Russian Federation Navy, has the resources and desire to undertake such an assessment."
Read a previous story about Andreeva Bay here.
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