Episode:
103
27/VT Lead-Bismuth Reactor
Country:
USSR
Years of Operation:
1965–1987
Category:
Research & Experimental
Reactor Type:
LMFR
Coolant:
Lead-Bismuth Eutectic
Fuel Type:
Enriched Uranium
Moderator:
None
Thermal Power (MWth):
155
Electrical Power (MWe):
155
Status:
Research & Experimental
timeline
First Criticality Year
1965
Commercial Op Year
Shutdown Year
1987
Lessons Learned
Lesson 1 - If the Coolant Needs a Babysitter, It Owns You
- Keep it above 253°F or it becomes a metal brick. That is not elegance. That is a hostage situation with piping.
Lesson 2 — Maintenance Matters More Than the Sales Brochure
- A sleek design on paper can still be a maintenance nightmare. Slag, leaks, and freezing risk settle arguments fast.
Lesson 3 — Polonium Changes the Entire Tone of the Conversation
- Once Po-210 shows up, maintenance stops being routine. Internal alpha contamination is not a footnote.
27/VT proved that lead-bismuth could run. It also proved that “can run” and “should scale” are not the same sentence.
In nuclear, as in life, some ideas look magnificent right up until the mechanics arrive.
sources
ARTICLE
The Soviet 27/VT was not a commercial power reactor. It was a land-based prototype propulsion plant at Obninsk, built to prove out liquid lead-bismuth coolant for naval use.
Construction began in 1953, and the plant was commissioned in January 1959 and produced about 70 MW thermal. No meaningful electric output here. This was a naval test bed, not a grid machine. Its real mission was to teach the Soviets how to run a compact liquid-metal reactor and help pave the road to the K-27 and later the Alfa-class submarines.
And to be fair, it did its job. The plant ran in two operating campaigns totaling 17 years, using two different cores, with the second campaign’s spent fuel reportedly unloaded in 1976.
So this was not some PowerPoint fever dream that lived for eight minutes and died in a conference brochure. It had real operating time. Real scars. Real lessons.
Which is exactly why it matters. Prototype plants are supposed to surface ugly truths early, before somebody in a clean suit starts calling the concept “proven.”
The ugly truths here were about as subtle as a wrench in a dryer.
Lead-bismuth freezes at about 253°F. That meant the system had to be kept hot all the time. Lose heat, make an operator error, or botch a shutdown, and your coolant tries to become a plumbing fixture.
Soviet sources explicitly note freezing in portions of the circuit during emergencies or personnel mistakes.
They also reported high slag content in the core due to lead impurities after the second run. During repairs, leaks also created significant hazards from radioactive aerosols and polonium compounds.
And that brings us to the part that should make any maintenance crew’s eye twitch: Polonium-210.
In lead-bismuth systems, neutron activation can produce Po-210, and Po-210 is an alpha emitter. Outside the body, alpha radiation is limited. Inside the body—through inhalation, ingestion, or contamination entering a wound—it is a very different story. In plain English: if this stuff gets inside you, you need to make sure your will is current. Yeah. That bad.
SLIDE DECK
