In the latest incident, the plant discharged 10 times the normal weekly amount of radioactive iodine-129 on the day that officials from HM Inspectorate of Pollution and the Nuclear Installations Inspectorate arrived to investigate an earlier leak of plutonium.
Although the discharge of 3,000 million becquerels of radioactive iodine-129, which has a half-life of 10 million years, happened 'during the week ending 13 February', according to the company, it became public only yesterday. BNFL said that the delay resulted from the time required for its staff to analyse the discharge. The discharge came from the plant which reprocesses fuel from Britain's first-generation Magnox reactors. The normal discharge level is 400 million becquerels a week.
Although BNFL said that no authorised limits had been breached and that the dose to the most exposed members of the population would be well below any safety limit, the incident could not have happened at a worse time. The company is due to appear in court later today to answer charges that its waste-processing operations breached nuclear safety laws. The prosecution has been brought by the Nuclear Installations Inspectorate, which is usually reluctant to take court action.
Last Tuesday, David Maclean, the Minister for Environment and Countryside, took the unusual step of amending, by means of a written answer to a parliamentary question, an earlier statement on the plutonium leak that he had made to the House of Commons. He released figures showing that in one day, through one discharge stack, Sellafield had released nearly 10 times as much plutonium as it usually discharges through the stack in a year.
In what Mr Maclean described as 'a rather extraordinary discourtesy', Sellafield's managers had not informed the local MP, Jack Cunningham, of the plutonium leak, even though he was visiting the site on 11 and 12 February, when the leak was discovered.
The Pollution Inspectorate is currently deciding whether BNFL should be allowed to operate its new Thermal Oxide Reprocessing Plant at the site and how much radioactivity it should be allowed to discharge. According to officials within the Department of the Environment, if the plutonium leak had occurred under the proposed new regime which would impose stricter limits, 'they would have had to shut'.
Mr Maclean ordered HMIP to investigate the plutonium leak and has promised that the results will be made public. However, British Nuclear Fuels added to the confusion with a statement yesterday - two weeks after the event - that the discharge had actually been only two-thirds the amount the company had orginally said. Yet Mr Maclean made no mention of the revised figures in his written parliamentary reply on Tuesday.
Chris Smith MP, Labour spokesman on environmental protection, said: 'I have written to Michael Howard demanding that this latest leak is included in the scope of the HMIP inquiry. It illustrates the need for daily or weekly limits on discharges rather than relying simply on annual limits which may not adequately protect the environment, and the health of local residents.'
According to Pat Green, of Friends of the Earth: 'Once again, BNFL has demonstrated that it cannot be trusted to operate Sellafield in an open and safe manner. No further discharges should be permitted . . . until there has been a thorough and public review of BNFL's safety procedures.'