MOSCOW, June 1. /TASS/. The Project 941 Akula-class heavy nuclear-powered missile-carrying submarine cruiser Dmitry Donskoi was decommissioned due to its spent nuclear core, a source close to the Russian Navy told TASS on Thursday.

"The Dmitry Donskoi could no longer be in service due to its spent nuclear core," the source said.

The nuclear core’s replacement with a new unit "was deemed as inexpedient due to the high cost of this operation," he explained.

In addition, the submarine cruiser’s 40-year service in the Russian Northern Fleet was also taken into account, he added.

Over the past few years, the Dmitry Donskoi sub had served as a testing platform for new Borei-, Borei-A-, Yasen-and Yasen-M-class submarines, the source recalled.

On June 1, celebrated as Northern Fleet Day in Russia, the editorial board of the Rossiyskaya Gazeta daily is holding a premiere of the documentary: "Dmitry Donskoi: Thanks for Dreams" devoted to the completion of the combat service of the world’s most powerful Project 941 nuclear-powered submarine.

Dmitry Donskoi sub

The submarine Dmitry Donskoi was the lead submarine cruiser in a series of six heavy nuclear-powered missile-carrying subs developed by the Rubin Central Design Bureau of Marine Engineering and built at the Sevmash Shipyard (both are currently part of the United Shipbuilding Corporation).

The nuclear-powered sub Dmitry Donskoi was put afloat on September 29, 1980 and entered service with the Navy on December 29, 1981. The submarine cruiser initially carried intercontinental ballistic missiles (ICBMs) of the D-19 strategic missile system as its basic armament. In 2002, the nuclear-powered sub underwent its upgrade under Project 941UM, following which it was involved in the tests of the seaborne Bulava ICBM.

In the summer of 2017, the submarine cruiser made an inter-fleet transit to the Baltic Sea where it took part in Russia’s Main Naval Parade. In all, shipbuilders constructed six Project 941 subs for the Russian Navy. All the vessels were based at the Northern Fleet. By now, three of them have been disposed of using US funds. Two submarines, the Arkhangelsk and the Severstal, have been withdrawn from service and are awaiting their disposal.