THE UK safety watchdog admitted last night that its preliminary report into a serious incident at the Sizewell A nuclear power station contained “pessimistic assumptions” and was misleading.

David Green

THE UK safety watchdog admitted last night that its preliminary report into a serious incident at the Sizewell A nuclear power station contained “pessimistic assumptions” and was misleading.

The report - written less than a month after 40,000 gallons of “radioactive water” leaked from a burst pipe and obtained a few weeks ago following a Freedom of Information request by nuclear consultant John Large - suggested that the incident could have led to an off-site release of radioactivity.

It formed the basis of a claim from Dr Large that Suffolk had been only ten hours away from a major accident involving the evacuation of thousands of people.

However, senior officials from the Nuclear Installations Inspectorate (NII) - part of the Health and Safety Executive - told a packed public meeting in Aldeburgh last night that the report had been written before the full facts had become known.

It had been intended for internal discussion and had contained a number of pessimistic assumptions which had later proved to be incorrect.

Peter Rothwell, an inspector who was the joint author of the report, claimed that when he supplied Dr Large with the report he had warned him that it was misleading.

Dr Large, who was not invited to attend last night's meeting, said late last night from his London home that he had received no such warning. “If that had been the case there would have been something to that effect accompanying the document. There was not,” he said.

Last night's meeting - billed as an attempt to uncover the true facts surrounding the nuclear incident and attended by Suffolk Coastal MP John Gummer - was organised by the Sizewell Stakeholder Group in response to the claims made by Dr Large in a report commissioned by the Shut Down Sizewell Campaign.

It was in January 2007 that a plastic pipe burst, causing 40,000 gallons of radioactively contaminated water to escape from a plant where highly radioactive uranium fuel rods were stored prior to dispatch to Sellafield in Cumbria for reprocessing. The total capacity of the plant is 800,000 gallons.

About 10,000 gallons were discharged into the North Sea as a result of the incident but Magnox South, the power station operator, said the radioactivity involved was less than one percent of the annual amount the plant was licensed to discharge and posed no risk to the public or the environment.

Facts to emerge since the incident and at last night's meeting include:

the wrong strength of pipe was used in the construction of the cooling plant in the 1960s

alarms connected to the plant either failed to go off at the time of the incident or were “masked” by other alarms at the power station

the burst pipe was eventually discovered by a contractor working in an adjacent laundry area

Mr Rothwell and his boss, Steve Gibson, defended the NII's decision not to prosecute Magnox Electric - despite their initial report detailing a string of “possible breaches” of the site license.

The officials said a prosecution would not have been in the interests of nuclear safety. A directive had been issued ensuring that Magnox South reviewed its safety arrangements and made improvements to the plant.

The officials also said that they accepted calculations put forward by Magnox South which showed that the cooling plant involved in the incident could not have drained leaving fuel rods exposed and vulnerable to catching fire.

Ray Jepps, chief nuclear officer for Magnox South, told more than 40 members of the public and 20 members of the SSG: “It would have been physically impossible for that fuel to have caught fire.”

Officials from the company said �2 million had been spent at Sizewell A in replacing pipework in the pond area and improving the alarm system. Money had also been spent at the company's other nuclear power stations.

Re-training of staff had been ordered and lessons learned from the incident had been circulated throughout the nuclear industry.

Peter Lanyon, representing the Shut Down Sizewell Campaign, criticised the SSG for not inviting Dr Large to speak at last night's meeting.

david.green@eadt.co.uk