French submarine Triomphant ( S616 ) The Triomphant is a strategic nuclear submarine of the French Navy ; she is the lead boat of her class . She collided with a British nuclear submarine in 2009 . History . Construction and testing . The first sheet of " Triomphant " was cut at DCN Cherbourg in October 1986 , and her engine was shipped to her from DCN Indret five years later . The reactor was built into the vessel in August 1991 , with the fore and aft sections being welded on in January and April 1992 respectively . She was armed and given a commander in May 1992 and moved from the assembly site to the completion basin in July 1993 . Her launch in March 1994 was followed by her first dive that June and her trip from DCN Cherbourg to lle Longue that July down the " free route " between Cherbourg and Brest , with a crew of 110 and engineers from DCN Cherbourg . On 4 January 1995 , during testing , she reached her maximum depth for the first time and made her first firing of a ballistic missile the following month . Photographs of her were exhibited to the Senate of France from 15 to 23 May 1995 . In June she set off back to Cherbourg for Post - Testing Upgrades ( Remises A Niveau Après Essais or RANAE ) , then set off for a second set of trials , making 1 , 300 hours of test dives in total and a five - week trip . She then spent five weeks in maintenance at Cherbourg and during her main weapons tests took on 11 torpedo models , five trial torpedoes and one Exocet SM39 exercise . As a deterrent system , a salvo of 15 models was successfully launched and , in the last round of development , she functioned successfully as a missile platform even if her engine did not achieve its best . She left Cherbourg on 7 March 1996 for her second round of trials , with the final tests of her nuclear boiler coming on 12 July and of her weapons systems on 26 August . Active service . " Triomphant " entered active service in March 1997 . On 18 October 2001 , the fleet support service notified the DCN that " Triomphant " was about to take her first period of Unavailability for Maintenance and Repairs ( IPER or " Indisponibilité pour Entretien et Réparations " ) . The 150 million Euro contract was granted to DCN , with the IPER starting at Ile Longue on 2 April 2002 , scheduled for 29 months in all . In this , her first major refit , her missiles and the fuel elements of her nuclear boiler were disembarked . In August 2004 " L ' Humanité " ran a piece with the headline " Pas si Triomphant que ça " reporting that " Triomphant " had suffered a nuclear leak from one of her nuclear warheads by the end of 1997 and from her reactor in 2004 , though the FOST downplayed the incidents and stated no radiation had been released since the reactor had been nonoperational at the time . She carried out a test flight of a M45 strategic missile on 1 February 2005 in the Atlantic . In the night between 3 – 4 February 2009 , " Triomphant " collided with the Royal Navy submarine HMS " Vanguard " . " Triomphant " was reported to have proceeded to Brest under her own power , submerged , but with extensive damage to her sonar dome . The French originally claimed that " Triomphant " had " collided with an immersed object ( probably a container ) " . After " Vanguard " returned to harbour , it was confirmed that the collision was in fact with her .