Open Veils · Answer
When were thorium reactors last used in the us?
The last operational thorium-cycle reactor in the U.S. was the Shippingport LWBR, shut down in 1982 — not because it failed, but because cheap uranium undermined the economic case for breeding. The suppressed punchline: post-shutdown analysis confirmed it had actually bred new fissile material, validating the entire concept after the program was already dead. Advocates like Kirk Sorensen at Energy From Thorium argue this vindication was deliberately buried during the uranium-lobby-driven pivot away from thorium.
Evidence
- The Shippingport Light Water Breeder Reactor, located in Pennsylvania, loaded a thorium–uranium-233 core that went critical in August 1977.
- The core was subsequently removed, analyzed, and shipped to Idaho.
- Kirk Sorensen and the Energy From Thorium project have long argued that the timing of this confirmation was not coincidental — the breeder program was wound down precisely as uranium proved abundant and cheap in the 1980s, eliminating the institutional incentive to pursue thorium's long-term advantages.
- The competing program, the Clinch River Breeder Reactor Project (a plutonium fast breeder, not thorium), was cancelled in 1983 after sustained political opposition, per the Wikipedia record on thorium-based nuclear power.
- Per Energy From Thorium's historical record, it ran continuously until October 1, 1982, when it was shut down under budgetary pressure and a need to examine the fuel in detail.