An internal report into a major leak at the British Nuclear Fuels Limited plant in Sellafield has raised major concerns about the operation of the facility after it found evidence that staff had failed to identify the rupture for nine months.
The report on the Thorp nuclear reprocessing facility found there was an "operational complacency" among staff who believed that major leaks at the plant were impossible because of its design, despite previous evidence to the contrary.
The report by a board of inquiry found that checks continuously failed to identify the leak in the plant in Cumbria on the north west coast of England which began last July but which was not found until this April.
It led to 83,000 litres of radioactive material, containing 20 tonnes of uranium and plutonium, spilling into a concrete containment tank.
Staff initially dismissed evidence of a major leak as a calculation error because the volumes involved were so large, according to the report.
It also said the company failed to carry out a detailed inspection of the pipework and containment tanks for a month after staff had evidence there was a major leak.
The seriousness of the incident was not notified to international authorities until the second week in May, even though the latest report indicates that Thorp staff were aware of the volumes of radioactive waste involved from April 18th.
As the leak was contained, it posed no current safety threat to the general public in Ireland or Britain.
Minister for the Environment Dick Roche has sought an urgent meeting with representatives of the British government on foot of the report and has raised questions as to why the Irish Government was not informed about the seriousness of the leak from the outset.
He accused BNFL, the main operator of Sellafield, of "gross incompetence at best, concealment of the facts at worst".
The Government was informed of the leak on April 22nd, according to a new information-sharing agreement with the British government, but Irish officials say they were not made aware of the seriousness of the incident until May.
Mr Roche said the report provided "ample evidence that the safety culture and practices at Sellafield do not measure up to the assurances provided by the UK government in relation to the safety operation of the plant".
According to the board of inquiry report, the rupture of the pipe was caused by a design fault which meant it could not withstand the shaking motion of tanks or cells linked to the pipes.
The report found there was evidence of a leak dating back to July in relation to the potential leak, and further evidence that it became extremely serious on January 15th, although the evidence, from volume discrepancies, would not have given rise to serious concerns.
However, there were samples carried out on the cells which indicated the presence of radioactive waste in November 2004 and February 2005, but these failed to be acted on.
In March calculations were carried out which indicated a major leak, but these were dismissed for a number of days because staff believed they were calculation errors.
It took three weeks for staff to confirm the figures were correct and then there was a further delay of a week before they carried out a camera inspection of the tanks to confirm there had been a major leak, because it was not deemed by staff to be a priority.
The report, which has made 16 safety recommendations, found that there had been "universal incredulity" among staff that there could have been a major leak.
Mr Roche said last night: "After the last incident, I compared the managerial skills of those who run Sellafield to those of Homer Simpson. Well maybe I was doing Homer a disservice; on this occasion I would like to know who are the Mr Burns and Smithers of this operation," he said.