Alfa class
Alfa class is a nuclear-powered submarine operated by Soviet Navy, powered by BM-40A / OK-550 of about 155 MWt. Retired.
Lead-bismuth cooled, titanium hulled, and the fastest submarines ever built. The coolant froze solid if the reactor was allowed to cool, so the boats had to be kept hot continuously in port. An unsuccessful design, and the only serious attempt at a liquid-metal-cooled naval reactor.
| Reactor | BM-40A / OK-550 |
|---|---|
| Reactors per vessel | 1 |
| Thermal output | 155MWt |
| Fuel enrichment | 90% U-235HEU |
| Refuelling | not disclosed |
| Category | submarine |
|---|---|
| Role | SSN |
| Operator | Soviet Navy |
| Country | Russia |
| Vessels in class | not stated |
| In service from | 1971 |
| Status | Retired |
Other submarines
| Class | Enrichment | Status |
|---|---|---|
| AUKUS submarines | HEU | Planned |
| Akula class | - | Operating |
| Arihant class | HEU | Operating |
| Astute class | HEU | Operating |
| Borei class | HALEU | Operating |
| Columbia class | HEU | Under construction |
| Dreadnought class | HEU | Under construction |
| Han class (Type 091) | - | Operating |
| Le Triomphant class | LEU | Operating |
| Los Angeles class | HEU | Operating |
| Ohio class | HEU | Operating |
| Oscar II class | - | Operating |
| Seawolf class | HEU | Operating |
| Suffren class (Barracuda) | LEU | Operating |
| Type 093 and 094 (Shang and Jin) | LEU | Operating |
| Typhoon class | - | Retired |
| USS Nautilus | HEU | Retired |
| Vanguard class | - | Operating |
| Virginia class | HEU | Operating |
| Xia class (Type 092) | - | Retired |
| Yasen class | HALEU | Operating |
Alfa class in context
It is one of 22 submarine programs on record, 15 of them operating and 4 retired, and one of 13 naval reactor programs from the same country.
Each of its reactors is rated about 155 MWt; across the 19 submarine programs with a stated rating the median is 165 MWt, and this one ranks 11th.
Its fuel is recorded as HEU, the same as 10 of the other 15 submarine programs with a stated enrichment class.
It entered service in 1971, 55 years ago; the submarine programs on record entered service between 1955 and 2020, and this one is the 2nd earliest of 17.
| Measure | Alfa class | Median of submarine programs | Standing |
|---|---|---|---|
| Thermal power per reactor (MWt) | 155 | 165 | 11 of 19 |
| Entered service | 1971 | 1997 | 2 of 17 (earliest first) |
Worked out from the entries on this site only, so a figure compares Alfa class with what is recorded here, not with everything that exists. An entry with no value for a measure is left out of that measure's ranking and median.
Sources
- World Nuclear Association, Nuclear-Powered Ships · retrieved 2026-09-07
How these sources are used, including the corrections applied on top of them and what is deliberately left blank · download the underlying data