A top-level report into the failure of safety procedures during a major incident at Heysham 1 has been made public.

Although there was no risk of a radioactive leak at any time during the incident on March 11, inspectors from the Health and Safety Executive decided to categorised the event as 'level 2' on the international scale.

This is considered as a major incident in the nuclear industry and was, the report says, "due to the multiple failures of safety provisions."

The incident occurred during a fuelling machine operation when the shield plug failed to disconnect.

A mechanical interlock designed to prevent the machine moving until safe to do so also failed and this led to the machine moving sideways resulting in an impact.

The shield plug was severed into two parts with the lower part falling into a storage tube.

A specialist Inspector visited the site within a few hours of the event being reported.

He confirmed that the nuclear safety significance of the actual event was low, but that it could have been more serious if the fuelling machine had been operating at the reactor.

A health and safety spokesman said: "We eventually allowed British Energy to return the machine to service following our assessment of the revalidated safety case.

"We continue to monitor the longer term actions arising from the event as part of our routine regulatory business."

A spokesman at Heysham 1 said: " A plug unit fell and broke but no one was hurt and there was no radiological release.

"Some safety procedures did fail to activate but it didn't get too far along the chain.

The fuelling machine was back in service and working perfectly, soon after."