Radioactive leak at Devonport
The liquid escaped into the River Tamar after an incident involving HMS Trafalgar.
The Royal Navy has confirmed up to 280 litres of water, likely to have been contaminated with tritium, poured from a burst hose as it was being pumped from the submarine in the early hours of Friday. The submarine was alongside at Devonport, after undergoing routine maintenance.
A spokesman for the Royal Navy said no-one had been hurt in the incident and the vessel's nuclear power plant was unaffected.
He said: "Shortly after midnight on the night of November 6/7, during a standard operation to transfer primary coolant from HMS Trafalgar to an effluent tank on the jetty, a hose ruptured, resulting in a leak of the coolant.
"A maximum of 280 litres of coolant were discharged from the hose onto the submarine casing, jetty and into the Hamoaze area of the river Tamar."
As soon as the leak was discovered, the transfer was stopped, the area was quarantined, monitoring and sampling carried out and a clean-up operation completed, the spokesman said.
He added: "Initial sampling has not detected any radioactive contamination in the local environment.
"The environmental risk is assessed to be negligible and analysis of river water has not shown any detectable contamination.
"Investigations into the cause of the rupture are ongoing and will lead to remedial action as necessary to prevent this incident from re-occurring.
"This incident has not affected the submarine's programme."
He added the Environment Agency, Health and Safety Executive and the Defence Nuclear Safety Regulator have been informed of the incident.
Previous reported radioactive spills at the dockyard include one in October 2005, when it was confirmed 10 litres of water leaked out as the main reactor circuit of HMS Victorious was being cleaned to reduce radiation.
Earlier the same year the Environment Agency had threatened legal action against former dockyard owners Devonport Management Limited (DML) after two spillages within the space of a week.
There were 10 nuclear leaks at the base between 1980 and 1998, during which 570 litres of radioactive liquid was lost. The worst incident was in 1985 when around 350 litres was spilled.
The dockyard is licensed to discharge low-level radioactive water in the Tamar. The limits were increased by 500 per cent in 2002.
Investigations are now being carried out by the Ministry of Defence and the Environment Agency in liaison with the Nuclear Installations Inspectorate (NII).
A spokesman for the Environment Agency said: "Our role is to regulate the site to ensure the protection of people and the environment.
"We are certain there is no significant environmental impact, but we have taken our own samples for reassurance purposes and these are in addition to the monitoring carried out by the Ministry of Defence.
"We will investigate the circumstances of this unauthorised discharge and make sure that all necessary measures are taken to stop it happening again."
Independent nuclear consultant John Large said the leak could have posed a risk to people and the environment depending on the levels of radiation.
He said: "This is a failure of the system, management or operatives. Something like this was readily foreseeable. The real issue is that the system designed to prevent this incident has, in fact, allowed it to happen."
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