A group of Royal Navy submariners have been given permission to leave HMS Trafalgar, after they expressed fears over their safety.
HMS Trafalgar has undergone 15 months of repairs
The commanding officer agreed to the 11 sailors leaving the submarine before operational tests, following repairs.
HMS Trafalgar has been out of service since it ran aground off the Isle of Skye in 2002 during a training mission.
The Ministry of Defence has said there were some faults, but not enough to stop the vessel going to sea.
And it has denied there was any radiation leak.
The MoD also dismissed reports in the Daily Mirror that the refit at the Devonport yard in Plymouth had cost £60m.
They also stressed that there had been no mutiny, with no sailors refusing to sail, and that there would be no disciplinary action.
BBC defence correspondent Paul Adams said the men could never have been accused of mutiny or disobeying a direct order, as the order to sail had yet to be given.
The officer in charge of the Royal Navy's submarine flotilla based at
Devonport, Plymouth, denied HMS Trafalgar was unsafe.
Captain Simon Martin said: "The submarine has now dived, and I know for a fact that the commanding officer has had other members of the ship's company knocking on his door and saying they are 100% happy."
Capt Martin said the 11 men might be suffering from post traumatic stress disorder
following the 2002 collision and the diesel leak.
He added: "They said they were worried about being at sea in a dived
submarine. The last thing you want on board is someone who feels unstable."
An MoD spokesman later said that five sailors had now returned to the submarine, three were still being medically assessed and two had been cleared fit but had
not as yet returned and were to be interviewed again.
One man had refused to return to vessel.
Although some repairs were made after the original refit, at Faslane nuclear base on the Clyde, the majority of the crewmembers' concerns were unfounded, the MoD added.
Some allegations, such as that the sub's anchor could not be lowered, or that a nose cone had been welded on wrongly, were simply not true, the MoD insisted.
A problem with a single control rod in the ship's reactor was minor, it said.
The November 2002 collisions injured three sailors and caused damage initially estimated at £5m.
Last week three crew members were treated after diesel fumes entered the sub's ventilation system during a training exercise at Devonport.
Breathing masks had to be worn when Freon, a refrigerant gas, escaped in another incident.
All the Trafalgar's crew had been asked if they had any concerns about the vessel's operating systems.
Last Friday, commanding officer Mark Williams released the 11 from duty and temporary replacements joined the other 109 members, currently being trained in preparation for operational deployment.
The submarine had been given the all clear before it left Devonport.
"The Royal Navy would not send officers to sea if it was not totally confident about the safety of a boat," an MoD spokesman said.
"There was no question of a mutiny or that any individual refused to carry out orders."
Last month, a court martial hearing reprimanded Commander Robert Fancy and Commander Ian McGhie, both 39, for their part in causing the vessel to ground in 2002; both pleaded guilty to negligence.