Royal Navy nuclear-powered submarines have been involved in more than 200 radiological incidents at a single base in the past five years, according to a report released under the Freedom of Information Act.

In one case, experts at the Devonport naval base who were supposed to be monitoring nuclear reactor operations aboard HMS Tireless, a submarine with a history of technical faults, were found to be in the wrong vessel.

The Royal Navy said that since 2002 the majority of the incidents recorded at Devonport, the Navy’s only nuclear submarine refitting base, involved “either nil radiological or the very lowest radiological consequences”. However, details released to the Western Morning News revealed a catalogue of potential safety scares. The report showed that between 2002 and 2006 there were 189 recorded incidents, including 12 in the first two months of this year. The three most-serious incidents last year merited a safety-scare rating of Class 3, under a sliding scale system ranging from Class 1, the most severe, to Class 5.

John Large, an independent nuclear consultant, told the newspaper: “One would expect there to be minor incidents because of the complexity of safely looking after nuclear engineering. But some of these incidents represent major systems failures that simply should not have happened.”

The Ministry of Defence said: “There was no risk to members of the public from these incidents.”

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