In 2000, the U.S. needed to refurbish aging nuclear warheads. But there was a problem: the government had forgotten how to make a classified material called Fogbank, crucial to their operation. For five years, engineers struggled to recreate it—without even knowing what the impurity was that made it work.
Fogbank was originally produced from 1975 to 1989 at Facility 9404-11 in Oak Ridge, Tennessee, used in W76, W78, and W88 warheads. By 2000, when warhead life-extension plans began, the original facility was gone, the experts had retired, and documentation was lacking. Attempts to substitute another material failed due to inadequate simulation models.
A new Fogbank facility was built, but manufacturing stalled. Engineers evacuated repeatedly due to toxic solvents like acetonitrile. Even after restarting production, the product failed tests. In 2007, the project was designated “Code Blue.” By 2008, after spending $69 million more, Fogbank was finally reproduced.
The breakthrough came when engineers discovered that a cleaning step—absent in the original process—removed a critical impurity. Once that was understood, quality improved. The first refurbished warheads were delivered to the Navy in 2009, and the W76 upgrade program was completed in 2018.
In 2000, the U.S. needed to refurbish nuclear warheads—but a crucial classified material called Fogbank had been forgotten.
No one remembered how to make it, documentation was scarce, and nearly all the original experts had left or retired…🧵👇 pic.twitter.com/ss1wsqdi4V
— Detective Tiger's Stories (@TigerDetective) May 2, 2025