Almost 1,700 meters under the Norwegian Sea lies something more than a sunken submarine. Inside the Komsomolets they continue the nuclear reactor that powered the ship and two torpedoes armed with nuclear warheadslocked in a wreck subjected to salt water, pressure and corrosion for decades. They did not get there because of a secret mission or a failed test, but after an accident that turned one of the great naval feats of the Soviet Union into a problem that we are still trying to understand.
The history of the Komsomolets did not end when the hull hit bottom. The reactor releases radionuclides in sporadic episodes, a behavior that current studies have been able to observe and measure with much more precision than in the 1990s. These emissions have not caused a broad impact on the marine ecosystem so far, but the question remains open.
Before becoming a wreck, as the remains of a sunken ship are called, the Komsomolets had been one of the most ambitious undertakings of Soviet naval engineering. It entered service in 1983 with a sturdy titanium helmet and the ability to operate at more than 1,000 meters depth, an exceptional level for a military submarine of its time. According to the BBC’s historical reconstruction, NATO hoped that this model would inaugurate a new class of attack submarines, but the Soviet Union never built a second unit.
The Soviet submarine that ended up becoming a problem at 1,700 meters deep
On April 7, 1989, a fire started in one of her compartments while she was sailing in the Norwegian Sea. The crew managed to bring the ship to the surface, but the fire continued to spread and disabled several systems. About five hours later, the submarine sank. Five sailors tried to escape in a capsule that surfaced, but only one managed to abandon it before it filled with water. In total, 42 of the 69 crew members died.
What remained on board may lead us to imagine a nuclear explosion, but current assessments they do not identify a spontaneous detonation as the relevant risk. Such an explosion requires arming and initiation mechanisms to operate with very specific timing. The documented concern is that corrosion will end up allowing radioactive material to escape from the reactor or, in the future, from weapons.
The containment intervention chosen years later did not consist of refloating the submarine, but rather isolating its most sensitive areas. In 1994, a Russian expedition used manned submersibles to seal the six torpedo tubes and some holes in the bow section with titanium plates. The objective was to reduce the circulation of water through the compartment where the warheads remained and limit an eventual release of plutonium. It was not a complete closure of the hull, but a containment measure that was still apparently intact when the wreck was inspected in 2019.
Decades later, the return to the Komsomolets had a different objective: to observe and measure, not to reseal it. In 2019, a scientific expedition sent Ægir 6000, a remotely operated vehicle equipped with cameras, manipulator arms and sampling instruments, to the submarine. The robot traveled through different areas of the hull and collected water, sediment and organisms near the reactor and torpedo compartment. Thus it was possible to study the state of the wreck without exposing a human crew to those conditions.
Results published this year in PNAS concluded that the assemblies containing the nuclear fuel are damaged and that seawater has reached the reactor material. The analyzes link this deterioration with intermittent emissions of radionuclides, although researchers are still trying to determine the exact mechanisms that cause them. The highest concentrations appeared next to a ventilation shaft and a nearby grate, but the material dilutes quickly and there is little evidence of accumulation in the surroundings of the wreck. No evidence of military-grade plutonium from the warheads was found in the bow area either.
Reaching the Komsomolets is not impossible: the submersibles of the 1990s and subsequent expeditions already demonstrated that work can be done at that depth. The difficulty is determining what action would provide a real improvement and what risks would be involved in intervening on a damaged nuclear structure. As explained by the Norwegian nuclear safety authority to the BBC, there are currently no plans for a new containment operation. The answer is still to go back, measure and monitor how a submarine that has been under the sea for almost four decades changes.
Images | Norwegian Marine Research Institute
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