Radioactive water escapes at Devonport sub dockyard
An investigation has started into a spill of radioactive water from the submarine refit complex at Devonport dockyards.
Operators Babcock said two holding tanks containing the water had overflowed over the weekend, but the spillage was kept in the dock basin.
The Environment Agency said it was not aware of any environmental impact.
A spokesman said it would be investigating and asking questions over procedures.
Plymouth City Council said: "We are reassured that the levels do not pose a risk to the public.
"We remain concerned at any lapse in safety procedures at such an important site.
"We will be waiting for the outcome of the investigation but are seeking urgent reassurances from the Ministry of Defence that this sort of incident will not happen again."
Devonport is the main refitting base for Royal Navy nuclear submarines and has a number of decommissioned nuclear submarines awaiting dismantling.
Water which has been used to cool the reactor on board nuclear submarines is irradiated with a substance called tritium.
Once submarines are docked at Devonport, water containing tritium is treated and discharged to permitted levels into the River Tamar.
Babcock said the incident happened after a hose pipe became detached from a tap.
Water from the tap went into the holding tanks, which had overflowed.
Babcock said the water in the holding tanks was below the limit for discharged tritium.
A spokesman said: "On discovery of the overflow early today, key staff were mobilised to manage the situation most effectively and the overflow has been contained and further discharges prevented.
"The affected area is being returned to normal operation. The impact on normal business on the site has been minimal.
"No personnel were contaminated or exposed to radiation."
The Environment Agency said that radioactive discharges from Devonport were limited to 700 gigabecquerels a year, a becquerel being a unit of radioactivity.
It believed the spill over the weekend was "less than one thousandth of 1% of that limit".
A spokesman said: "No additional radioactivity was discharged into the environment.
"At this stage we do not believe there is any environmental impact."
The Office for Nuclear Regulation said it would be investigating but the quantity of radioactive material released "poses no risk to people on or off site".