The incident, which took place on Thursday, happened while decommissioning work was taking place at a redundant building on the Cumbrian site. Particles of alpha radiation escaped into the air by way of a ventilation system in the inactive building which led to a chimney stack still in use.
A spokesman for BNFL said that the emission did not constitute a leak. 'It was a larger than usual discharge of radioactivity,' he said.
He would not reveal the scale of the emission, but said it fell well within limits imposed by the regulatory authorities. Her Majesty's Inspectorate of Pollution, the Department of the Environment and the Sellafield workforce have been informed of the incident.
The abnormal emission was discovered at 3pm on Thursday by a monitoring system programmed to take samples from the chimney stack every 24 hours. Following the alert, monitoring was increased to every four hours. Last night BNFL said the last two samples taken had shown 'significant reductions' in the radioactivity.
Dr Patrick Green, radioactive waste campaigner for Friends of the Earth, said the public had a right to know the extent of the emission. He said that BNFL had played down incidents in the past, citing a spillage at the plant last September. BNFL originally told inspectors the leak involved 700 grams of radioactive material, then upgraded this twice to several kilograms.
It had been found that monitoring instruments had failed to alert operators at the Cumbria site to the spillage, which caused a seven- week shutdown of the reprocessing plant. Dr Green said: 'We can no longer be expected to give BNFL the benefit of the doubt.' He also called for an urgent statement from the Secretary of State for the Environment.
The incident comes at a sensitive time for BNFL, which made an application to increase discharges of radioactivity into the atmosphere earlier this year after it admitted miscalculating its requirement.Reuse content