One of Britain's flagship nuclear facilities has been criticised by the Health and Safety Executive for significant safety lapses after a radioactive leak went undetected for months.

British Nuclear Group was fined £500,000 yesterday in a case brought by the HSE for breaches at the Thorp reprocessing plant at Sella-field in Cumbria, Britain's largest nuclear site. No reprocessing has taken place at Thorp since April last year, when about 83,000 tonnes of acid containing 20 tonnes of uranium and 160kg of plutonium escaped from a broken pipe into a sealed concrete holding at the site.