OK-550 reactor
The OK-550 reactor is the nuclear fission reactor used to power three of the seven boats of the Soviet Navy's Project 705 Лира fourth generation submarines. It is a liquid metal cooled reactor, using highly enriched uranium-235 fuel to produce 155 MWt of power.
OK-550 has three separate steam circulation loops, and was used in the boats built at Severodvinsk.
The reactor was developed by OKBM.
