The Devon-based submarine HMS Tireless has returned to Plymouth after a leak in its nuclear reactor.
The Royal Navy said the small leak of coolant was contained within the reactor compartment of the Trafalgar-class hunter-killer vessel.
The navy said that the incident “posed no risk to the public, the environment or the crew”.
It added it was not yet known how long the repairs to the 28-year-old vessel would take.
In 2000, a fault was discovered on board which then forced 12 hunter-killer nuclear submarines in the UK’s fleet to undergo intensive inspections.
The submarine became stranded in Gibraltar in May of the same year with a leak in pipe work leading from the nuclear reactor system.
It was there for nearly a year while repairs were carried out, putting a strain on relations with Spain, and drawing criticism from environmentalists.
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