Three fires broke out on nuclear submarines being refitted at Devonport Royal Dockyard, Plymouth, last year.
Devonport Dockyard said the fires were dealt with swiftly
The small fires, between October and December, had "no nuclear or radiological implications", the Health and Safety Executive (HSE) said.
They were caused by welding work on board the submarines and caused minimal
disruption, said yard operator DML.
Devonport is currently the UK's only refitting and defuelling site for nuclear submarines.
An HSE spokesman said no enforcement action had been taken against DML, but
added: "With fires in confined spaces, the potential is there for people to get
A DML spokesman said: "These were small fires associated with welding
operations and all were dealt with swiftly in accordance with DML's response
The nuclear refitting has been the subject of a series of protests by anti-nuclear campaigners.
The yard is also being considered as a site for dismantling the UK's redundant nuclear submarines.
Concerns have also been raised about the release of tritium, a radioactive substance produced by reactors from nuclear submarines based at the Devonport yard, into the River Tamar.
Levels of the chemical released by Devonport increased by 500% in 2003, although the government says that discharges were well within national and international guidelines, and well below that produced by naturally occurring sources in the area.