text: Radioactive cooling water was also mistakenly discharged into a submarine reactor compartment, the Office for Nuclear Regulation (ONR) reported.
  Reporting of safety incidents at the base, which refits Britain's nuclear submarines, was "below standard".
  Contractor Babcock International said safety was its "highest priority".
  The ONR issued a legal notice to improve after an incident last year in which a worker was contaminated with radiation.
  The ONR said the dose was "very small" but it "highlighted shortfalls" in health and safety at the yard.
  Babcock has been ordered "to bring the arrangements up to an acceptable standard" before the end of January 2016.
  The ONR said five other incidents broke safety rules between October and December last year.
  They were:
  The ONR also reported "shortfalls in the operation of the emergency monitoring vehicles" during a nuclear submarine accident exercise.
  Peter Burt, researcher at the anti-nuclear weapons pressure group Nuclear Information Service, said: "This is a worrying string of events in a short time at Devonport.
  "If the site operators are not able to improve performance rapidly the MoD should take steps to take the operating contract away from Babcock."
  Nuclear engineering consultant John Large, who has advised the government and environmental groups on nuclear issues, said: "These are not uncommon incidents in a complex operation like Devonport.
  "But the level of detail is not good enough. For instance what is the connection with the torpedo tubes and a radiological incident on the submarine?"
  The ONR declined to go into any more detail on the incidents, saying the reports were intended as summaries.
  Babcock said in a statement: "Improvements relating to the ONR enforcement notice and other recently reported incidents at Devonport Royal Dockyard are being addressed through a broader nuclear safety improvement programme to further enhance our current high levels of safety, in agreement with ONR."
  Plymouth City Council said it "takes the safety of nuclear operations at Devonport extremely seriously, as does the site operator.
  "It is protocol that we are informed immediately of any safety issues or incidents that are likely to be of concern to the wider public.
  "The operator also reports on its safety performance every six months at the local liaison committee."
  The Ministry of Defence (MoD) declined to comment.
target: Devonport naval base has been warned of legal action after a worker received a dose of radiation amid a series of safety breaches.