Torness probe after radioactive water leak

Health and safety officials were alerted when the problem was found during a routine inspection at the plant near Dunbar, East Lothian.

The incident was one of three reported to ministers from plants across the UK that are under investigation by the Office for Nuclear Regulation (ONR), the government's nuclear safety watchdog.

Groundwater at the Dunbar plant was found to be contaminated with radioactive tritium leaking from two pipelines.

A brown puddle containing plutonium five times the legal limit had leaked from an old ventilation duct at the Sellafield nuclear complex in Cumbria, while a back-up cooling system failed at a plant in Hartlepool.

The incidents were serious enough to be reported to ministers under safety guidelines agreed after the Chernobyl accident in Ukraine 25 years ago.

According to the ONR, the response to the incidents from the companies that run the plants was "appropriate". The pipelines at Torness were put out of use after the leak was discovered.

A spokeswoman for EDF Energy, the French company that operates Torness, said there had never been any danger to staff or the public, and that the levels of radioactivity that leaked were "extremely low".

A spokeswoman for the Scottish Environment Protection Agency (Sepa) added: "Sepa was informed by British Energy Generation Limited (BEGL) in February 2011 that routine sampling had detected a very small leak in a pipe leading to raised level of tritium in a limited area of groundwater. The leak has been stopped.

"Sepa has investigated the matter and has requested that BEGL carry out further work on the pipe system to demonstrate its integrity in the longer term. This work is due to be completed later this year."

Details of the incidents, all in February, emerged in a leaked report sent to ministers by the executive head of the ONR, Mike Weightman and circulated to First Minister Alex Salmond,

Scottish secretary Michael Moore, Energy Secretary Chris Huhne, Business Secretary Vince Cable, Environment Secretary Caroline Spelman and employment minister Chris Grayling;

The two-reactor Torness nuclear power station began generating in May 1988 and is expected to be decommissionned by about 2023. Disclosure of the incidents could further delay the government's plans for nuclear power station programme, already being held up by a safety review prompted by the Fukushima accident in Japan.

Stephen Bunyan, chairman of Dunbar Community Council said: "By and large I think we all feel quite safe living here and have every confidence in the team which runs Torness."