KTP-6 Atomic Reactor, Submarine

The 4th generation nuclear submarines of the Ash project, already under construction in Russia, became a symbiosis of two traditional directions of the Russian Navy, combining multipurpose torpedo and strategic missiles with cruise missiles in a single submarine cruiser project, ideally suited for naval operations. According to the developers, the new nuclear submarine was to attack enemy aircraft carriers and missile carriers, destroy coastal targets, and fight submarines.

The creation of the 4th generation nuclear submarine began back in 1977 (project 885, Ash) at the St. Petersburg Marine Design Bureau of Mechanical Engineering Malachite, which had already created multipurpose nuclear submarines. It was planned that these ships will replace several types of dissimilar submarines and will be able to solve many problems, including fighting the submarines of a potential enemy and its aircraft carrier formations.

Unlike all previous projects of the Soviet submarines, in order to reduce the level of their own noise, the Ash was made using a half-shell architecture. The reactor is located in the sixth compartment 10.5 m long with an equalization tank located around it to hold the boat in depth during rocket firing. In the seventh turbine compartment, 12 m long, there is steam turbine plant equipment, autonomous turbine generators and other power equipment.

The 4th generation Russian nuclear submarine needed a new type of power plant (PS). OKBM Afrikantov was responsible for its creation, which developed a new 4th generation KTP-6-85 water-water steam generating unit (KPP) with a KTP-6-185SP reactor with a thermal capacity of about 200 MW.

A distinctive feature of the new type of reactor was the integral monoblock arrangement of devices in which the reactor and its first cooling circuit are mounted in a single housing. This solution allows to exclude large pipelines from the PPU design (their maximum diameter was reduced from 675 for OK-650 to 40 mm for connecting pipelines for KTP-6) and, thereby, facilitates the natural circulation of the coolant in all operating modes. The latter is one of the key criteria for the low noise of the entire boat, eliminating the need for continuous operation of the main circulation pumps and reducing the reactor's energy consumption by its own needs by an order of magnitude, thereby giving a higher overall efficiency. Monoblock PPU is much more compact than the previous generation, easier to maintain, more secure and reliable. In the same time, the integration of all systems and components of the reactor in a single housing significantly complicates the maintainability of the installation due to their low availability. Therefore, the OKBM specialists were faced with the task of providing the 4th generation reactor with a non-repairable service life throughout the life of the boat. At the same time, the reactor core needed to be recharged twice less than in similar installations of 3rd generation boats.

Design solutions for the new generation of PUFs were tested at the KV-2 ground-based research stand with the TM-4 / KTM-6 prototype reactor in Sosnovy Bor, and in 1996 the reactor was officially approved for serial production. One of the most important features of this reactor is considered to be a new straight-through direct-pipe steam generator.

However, on the lead ship of the 885th project - the Severodvinsk nuclear submarine, launched in December 1993, this reactor never appeared. In 1996, the construction of the nuclear submarine was stopped due to lack of funding and was resumed only in 2004 already under a revised project. The financial and technological difficulties associated with the production of a block steam turbine unit for him led to the fact that in the process of redesigning the Severodvinsk boat she received a block PPU OK-650V with a previous generation VM-11 reactor with a thermal capacity of 190 MW. This significantly reduced the combat potential of the submarine, despite a number of other decisions taken on it to reduce the noise of the main power plant. On June 15, 2010, the Severodvinsk nuclear submarine was withdrawn from the boathouse and launched on June 24.

The changes that took place in the country and in the world led to the need to revise project 885, since many enterprises producing components for it were outside the borders of the new Russia, and electronics was morally obsolete. As a result, a new modernized project 08851 (885M, Yasen-M) appeared, on which the multipurpose nuclear submarines Kazan, Novosibirsk, Krasnoyarsk, Arkhangelsk and Perm began to be built.

According to OKBM Afrikantov, a subsidiary of the Russian nuclear corporation Rosatom, a new core of nuclear reactors for atomic submarines has been created and in 2018 tested for the first time in Russia. This facility can function throughout the life of the submarine without the need to refuel nuclear fuel. The “active zone” is the heart of the reactor. It contains the nuclear fuel and it is precisely in that the chain reaction occurs. The new technology of the subsidiary OKBM Afrikantov means that Russian submarines will not need refuelling. According to the former commander of the Northern Fleet, Admiral Vyacheslav Popov, the creation of the “eternal” reactor has enormous importance for the Russian Navy’s combat readiness. “With such a reactor [which does not require refuelling] the efficiency coefficient of the submarine increases several times,” Popov said. In the list of fourth generation submarines are those of the Borei and Yasen project.