This is coolbert:
Latest intel dope on the Russian hybrid submarine. A combination of nuclear and diesel/electric power?
"Russia Completes Hybrid Submarine"
"Russia's Sevmash shipyard at the Arctic city of Severodvinsk has completed a hybrid submarine powered by a diesel-electric plant and a small nuclear reactor. Designated B-90 and named Sarov, the submarine was completed on 17 December ."
"The submarine is known as Project 20120 in Russian design terminology. She apparently employs the small nuclear reactor -- known to some engineers as a "teakettle" -- to keep a charge on the battery, providing essentially unlimited underwater endurance on relatively quiet electric propulsion. In effect, this is an Air-Independent Propulsion (AIP) system."
""Secret" Russian Sub, Probed"
"Russia's Not So Super Secret Special Submarine"
"What's Wrong With This Submarine Story (W3TS2)?"
A degree of skepticism is had by those in the know. This is NOT some sort of revolutionary breakthrough?
A vessel to be used as a "test bed" for the new but not quite unique technology. NOT a submarine having two separate power sources. A diesel/electric submarine with a modified, not full scale nuclear reactor as a recharging source. A form of air-independent-propulsion different from German and Swedish designs. To be used for the Russian Northern Fleet as a "spy" ship?
Reactors of this type have been used in spacecraft with success. A much, much larger "radioisotope thermoelectric generator (RTG)" is needed to provide a continuous "trickle" charge to the subs batteries?
As of yet, the U.S. Navy has nothing to fret about?