THE Royal Navy is to make changes to its procedures, equipment and the way it informs the public after admitting an "unauthorised discharge" of radioactive liquid into the River Tamar.

An investigation into last month's leak of coolant from a hose linked to the submarine HMS Trafalgar is close to completion. But top brass released details of the incident and interim findings at yesterday's Devonport Local Liaison Committee Meeting, which discusses naval base safety.

They claimed the harm caused by the leak of 280 litres of coolant containing radioactive Cobalt-60 and Tritium, was "insignificant". But, nevertheless, they conceded that they should not be "complacent".

Following criticism of the time it took to inform the public and Plymouth City Council, Commodore Ian Jess, Devonport's Naval Base Commander, told the meeting: "It was an unauthorised discharge and our notification procedures were not as they should be, which added to people's worries."

He said reviews are being carried out into the incident and the communication and changes will be made to reduce the risk of it happening again.

Head of base safety, Captain John Taylor, explained the leak happened overnight on November 6 and 7 when the primary coolant was being pumped off HMS Trafalgar at the naval base's Seven Wharf. He said a hose connecting the vessel to a "primary effluent tank" on the dockside failed and showed the meeting, attended by about 30 people, a photo of the damaged pipe.

Since the incident Seven Wharf has not been used for this practice and it was temporarily suspended on Eight Wharf and Nine Wharf. These wharves do not experience the same tidal range and submarines can get closer to the jetties, so hoses are less susceptible to damage, said Capt Taylor. He said only the "youngest hoses" were now being used but also said there may have to be "physical change" to Seven Wharf so it can be in operation again.

Dr Paul Naylor, of the Environment Agency, said that although the coolant contained only 0.001 per cent of the dockyard's annual authorised level of Cobalt-60 and 0.1 per cent of Tritium, the incident was still "a serious unauthorised release".

The EA analysis was carried out 14 hours after the spill.

Plymouth City Councillor George Wheeler asked Dr Naylor about the effect on swimmers who used Plymouth Sound shortly after the leak.

Dr Naylor said the EA knew was "satisfied there was no risk to the public".

Following the leak the Ministry of Defence was criticised for not informing the public until the media broke the story on November 11.

Mr Jess said that had the leak been significant the public would have been notified immediately. He added that the MoD was looking at when the public should be told of less serious events.

Giles Perritt, civil protection spokesman for the city council, said the authority and MoD would be "looking to improve the way we work together".