Four nuclear fuel elements were found to be leaking during a routine inspection last week of Switzerland's oldest nuclear power plant, Beznau I. But the leak posed no danger to the public, officials said.
Beznau, which is about 30 years old, is one of five Swiss nuclear power plants and is run alongside Beznau II by the Swiss utility, NOK. NOK said on Thursday it had launched an investigation, which could take six months to a year to establish whether the producer, British Nuclear Fuels (BNFL), or the workers were at fault.
Beznau I is the only power plant still operating with British mixed-oxide (MOX), or plutonium and uranium mixed oxide, after BNFL admitted earlier this year to falsifying quality assurance reports on rods made for Japanese utilities. Japan and Germany sent their rods back to Britain's Sellafield nuclear plant where they are produced.
Richard Stratton, the head of NOK's nuclear fuel business, said the four defective elements found at Beznau I had nothing to do with the falsification scandal which prompted the resignation of top BNFL managers and other staff.
After the scandal broke this year, the Swiss nuclear safety authorities and utilities launched their own investigation into their MOX elements. Stratton said they found anomalies in quality control data, but that the rods themselves showed no defects.
Stratton said Beznau had experienced problems with leaky BNFL rods in 1997. "We used MOX before the falsification scandal - at the time we had three defect (BNFL-produced) fuel assemblies. The rest were fine, so we took the leaky ones out and replaced them.
"We discovered the latest leak during a routine check. Although this only rods we took out all 12 produced by BNFL and these will be investigated," he said, adding: "There is no risk to public or workers' safety because the leakage remained below dangerous levels."
swissinfo with agencies
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