https://en.wikipedia.org/wiki/Soviet_submarine_K-278_Komsomolets
K-278 had a double hull, the inner one being composed of titanium,
On 7 April 1989, while under the command of Captain 1st Rank Evgeny Vanin and running submerged at a depth of 335 metres (1,099 ft) about 180 kilometres (100 nmi) southwest of Bear Island (Norway),[4] fire broke out in the engine room due to a short-circuit,[5] and even though watertight doors were shut, the resulting fire spread through bulkhead cable penetrations. The reactor scrammed and propulsion was lost. Electrical problems spread as cables burned through, and control of the boat was threatened. An emergency ballast tank blow was performed and the submarine surfaced eleven minutes after the fire began. Distress calls were made, and most of the crew abandoned ship.
The fire continued to burn, fed by the compressed air system. At 15:15,[6] several hours after the boat surfaced, it sank in 1,680 metres (5,510 ft) of water,[citation needed] about 250 kilometres (135 nmi) SSW off Bear Island.[6] The commanding officer and four others who were still on board entered the escape capsule and ejected it. Only one of the five to reach the surface was able to leave the capsule and survive before it sank again in the rough seas.
A little radiation never hurt anyone.
“The reactor scrammed”
Well that’s certainly understandable! Did they ever find out where it went?;)