The tradition to dispose unnecessary submarines in the sea was born in the Soviet Union when it was not clear what to do with waste nuclear flagships. Some of them were sunk in the vicinity of Norway, which begins to recognize the danger of the neighborhood with Russia – in the Barents and Kara Seas.
In particular, it is referred to the submarine K-27. Its each trip ended in incidents, and in 1968 the radiation leak was so powerful that 9 sailors died from radiation sickness, and the rest became actually disabled.
Nobody "cleaned" this submarine of radiation, in the 80s it was just drowned in the Kara Sea only 30 meters from the surface, violating the environmental regulations. The Soviet Union did not consider it necessary to spend money on nuclear waste disposal, today's Russia is also unlikely to find the money – it spends everything on the war in Ukraine.
In Norway, flooded submarines are called "slow Chernobyl" – radiation is already beginning to flow into the ocean, causing irreparable harm. However, there is a bigger danger for Northern Europe. It is another flooded Soviet submarine K-159, which sank in 2003, just 200 kilometers from the coast of Norway.