Flasks used by British Nuclear Fuels to transport dangerous radioactive material can resist fire for less than three minutes, newly released research reveals.
The revelation will provide fresh headaches for the crisis-ridden BNFL, which runs a major business using the flasks. New safety regulations demanded by the United Nations mean that all the flasks will now have to be replaced.
The tests by France’s nuclear safety agency showed that the flasks would rupture within 175 seconds in a fire.
The flasks are used to transport 20,000 tonnes of uranium hexafluoride or “hex” – the raw material to make fuel for nuclear power stations – around the world every year, much of it for BNFL. Hex is particularly dangerous because as well as being radioactive it reacts with air to produce hydrofluoric acid, a gas which destroys the lungs.
Using the suspect flasks BNFL exports hex to Russia, US and Europe from its Springfields fuel fabrication plant in Preston. Internationally, the nuclear industry makes 2,300 shipments of hex every year by road, rail and sea.
The study was by the Institut de Protection et de Sreté Nucléaire (IPSN) in Paris, which advises the French government on nuclear safety. IPSN scientists led by Gilles Sert baked flasks in an oven and ran computer simulations to see if the hex container most widely used, a type 48Y, would survive the kind of fire that could erupt after an accident.
“Rupture of the 48Y container in a fire seems likely and its resistance to fire should be improved to guarantee safety,” they said.
Their study is published in the latest issue of the International Journal of Radioactive Materials Transport. From next year hex flasks will be required by the UN International Atomic Energy Agency to resist fire for 30 minutes at 800C. IPSN’s experiments suggest current flasks would explode after 175 seconds “in the most favourable case”.
But defects found by x-raying welds on the flasks, of which there are 100,000 worldwide, mean that the explosion could come even sooner. “Large quantities of uranium hexafluoride might be released in a transport accident involving a fire,” the scientists said.
The IPSN study was launched in the wake of the sinking of the French cargo ship, Mont Louis, on August 25 1984 after a collision with a ferry in the English Channel. It went down off Ostend, Belgium, with 350 tonnes of hex destined for Russia on board. There was considerable alarm about the danger and all of it was salvaged from the seabed.
There have been several other accidents involving hex, including a train derailment in the US and a seven-tonne leak from a French nuclear facility at Pierrelatte, both in 1977.
Edwin Lyman, scientific director of the Nuclear Control Institute in Washington, said: “This [report] raises disturbing questions about the credibility of industry safety assurances, not only for hex flasks but for all the radioactive material transport flasks in service today.”
BNFL confirmed yesterday that it used 48Y containers for shipping hex in Britain and abroad. It was transported from Springfields to Capenhurst near Chester for enrichment, as well as to enrichment plants in Russia, the US, France, Germany and Holland.
“Under the new proposed transport regulations there are some additional requirements, one of which is the fire test,” said a BNFL spokesman.
“The industry has done extensive research on the cylinders and there is no conclusive evidence that the current mode of shipping natural hex will not meet the new regulations.”
Although there had been thousands of shipments of hex, there had never been an incident involving a release of hex nor any danger to the public, he said.
“BNFL will continue to transport to a high standard in line with the regulations for the safe transport of radioactive material.”
BNFL has been under attack from the Nuclear Installation Inspectorate over its safety regime and from its major customers for falsifying quality control data on plutonium fuel. This week the government postponed part-privatisation of the company and demanded management improvements.
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