The Russian Navy is slowly retiring their Delta IV-class submarines, starting with the hull number K-84, the Yekaterinburg. Though for now the rest of the seven-hull class will remain active, the entire class will ultimately be replaced by Russia’s much anticipated Borei-class. The Yekaterinburg currently serves with Russia’s Northern Fleet, and is scheduled to be scrapped in 2022, according to TASS, a Russian state-owned media company.

The Delta IV was the final and most capable of the Delta-class design, and alongside the older Deltas, served as the backbone of the Soviet Union’s strategic nuclear submarine fleet since the first of the class entered service with the Soviet Navy in the early 1970s.

The Yekaterinburg’s history is a unique one, though marred by several mishaps, accidents, and failures. In 1989, the submarine participated in Operation Behemoth, a missile exercise that sought to launch all sixteen of the Yekaterinburg’s R-29RM Shtil ballistic missiles, and would have marked the first time a submarine successfully conducted a complete salvo launch all at once. The exercise was however unsuccessful due to an accidentally rocket fuel leak, which likely destroyed at least one missiles, though the submarine escaped any major damage.

Disaster also nearly struck the Yekaterinburg in 2018 when the submarine docked at a shipyard in Roslyakovo. While undergoing general repair and maintenance part of the submarine caught fire, likely the sub’s anechoic tiles, essentially rubberized panels impregnated with air bubbles that help reduce a submarine’s acoustic signature.

The fire blazed for nearly twenty-four hours and spread to the inside of the submarine. Fire crews were unable to put out the blaze: The Yekaterinburg was ultimately lowered into the sea, snuffing out the flames, though also flooding the inside of the submarine with corrosive sea water. After the incident, foreign countries and international media were assured that though unfortunate, the fire hadn’t posed any particularly grave risk, as the submarine’s torpedoes and nuclear missiles had been removed prior to scheduled maintenance. The problem, however, was that was just not true.

In an incendiary interview with the Russian newspaper Kommersant, a Russian Navy officer revealed that the submarine’s munitions actually had not been unloaded, in violation of Russian Navy safety protocol. The submarine’s R-29RM Shtil missiles house a plutonium warhead, and though the nuclear payload of the submarine would be unlikely to cause a nuclear explosion, it is easy to imagine radioactive particulates spewing out of the submarine and into the surrounding area and atmosphere. Disaster was luckily—and narrowly—averted.

Ultimately the Delta IV are slated to be replaced by the large and powerful Borei-class, a nuclear-powered ballistic missile submarine that will replace Russia’s mighty Typhoon-class as well. From the standpoint of safety—maybe that’s a good thing.

Caleb Larson is a Defense Writer with The National Interest. He holds a Master of Public Policy and covers U.S. and Russian security, European defense issues, and German politics and culture.

Image: Reuters.