Soviet submarine K-27

The K-27 was the only submarine of Project 645 in the Soviet Navy. Project 645 was not assigned a NATO reporting name. That project produced one test model nuclear submarine, which incorporated a pair of experimental VT-1 nuclear reactors that used a liquid-metal coolant (Lead-bismuth eutectic), placed into the modified hull of a November class submarine (Project 627A).

Launch and operations
The keel of the K-27 was laid down on 15 June 1958 at Severodvinsk Shipyard No. 402. She was launched on 1 April 1962, and she went into service as an experimental "attack submarine" on 30 October 1963. The K-27 was officially commissioned into the Soviet Northern Fleet on 7 September 1965. The K-27 was assigned to the 17th submarine division, headquartered at  Gremikha).

The nuclear reactors of the K-27 were troublesome from their first criticality, but the K-27 was able to engage in test operations for about five years. On 24 May 1968, the power output of one of her reactors suddenly dropped sharply; radioactive gases were released into her engine room; and the radiation levels throughout the K-27 increased dangerously – by 1.5 grays per hour. This radiation consisted mostly of gamma rays and thermal neutrons, with some alpha radiation and beta radiation in addition – generated by the released radioactive gasses such as radon, gassified radioactive isotopes of iodine, cesium, xenon, and krypton in her reactor compartment.

The training of her crew by the Soviet Navy had been inadequate, and these sailors did not recognize that their nuclear reactor had suffered from extensive fuel element failures. By the time they gave up their attempts to repair her reactor at sea, nine of her crewmen had accumulated fatal radioactive exposures.

About one-fifth of her reactor core had experienced inadequate cooling caused by uneven coolant flows. Hot spots in the reactor had ruptured, releasing nuclear fuel and nuclear fission products into the liquid-metal coolant, which circulated them throughout her reactor compartment.

The K-27 was laid up in Gremikha Bay starting on 20 June 1968. The cooling-off of her reactors and various experimental projects were carried out aboard her through 1973. These included the successful restarting of her starboard reactor up to the 40% of maximal power production. Plans were considered to slice off her reactor compartment and then to replace it with a new one containing standard VM-A water-cooled reactors. The rebuilding or replacement of her port nuclear reactor was considered to be too expensive, and also to be inappropriate because more modern nuclear submarines had already entered service in the Soviet Navy.

Scuttled in the Kara Sea
The K-27 was officially decommissioned on 1 February 1979 and her reactor compartment was filled with a special solidifying mixture of furfuryl alcohol and bitumen during the summer of 1981 to seal the compartment to avoid pollution of the ocean with radioactive products. This work was performed by the Severodvinsk shipyard No. 893 "Zvezdochka".

Then the K-27 was towed to a special training area in the eastern Kara Sea, and she was scuttled there on 6 September 1982 near the location 72°31'28"N., 55°30'09"E. off the northeastern coast of Novaya Zemlya (at Stepovoy Bay), in a fjord at a depth of just 33 meters (108 feet). It was necessary for a naval salvage tug to ram the stern of the K-27 to pierce her aft ballast tanks and sink her, because the K-27's bow had impacted the seafloor while her stern was still afloat. This scuttling was performed contrary to the International Atomic Energy Agency's requirement that nuclear-powered submarines and surface ships must be scuttled at depths not less than 3,000 meters.

The last scientific expedition of the "Russian Ministry of Emergencies" to the Kara Sea examined the site of the scuttling in September 2006. Numerous samples of the seawater, the seafloor, and the sealife were gathered and the analyzed. The final report stated that the radiation levels of the area were stable.

Lessons in nuclear submarine construction and safety learned from Projekt 645 were applied in Projects 705 and 705K – that produced the Soviet Alfa class submarines. These were equipped with similar liquid-metal-cooled reactors.

In September 2012 it was reported that the sub needed to be lifted from its shallow bed in the Kara Sea. The vessel is a "nuclear time bomb", as the rusting and decaying vessel may be reaching a critical level leading to an "uncontrolled chain reaction". Although a joint Russian and Norwegian in 2012 did not find alarming levels of radioactivity in the water and soil surrounding the sub, an urgent consideration pertains to the dismantling of the nuclear reactors should the sub be raised. Because the reactors were cooled by liquid metals, the nuclear rods became fused with the coolant when the reactors were stopped and conventional methods cannot be used for disassembling the reactors. However, France's Commissariat à l'énergie atomique et aux énergies alternatives designed and donated special equipment for a dedicated dry-dock (SD-10) in Gremikha, which was used to dismantle the Alfa-class submarines that shared this design feature. However, since the last Alfa reactor was dismantled in 2011, this equipment is at risk.