It has been revealed by unclassified official sources that Fogbank was originally manufactured in Facility 9404-11 of the
Y-12 National Security Complex in
Oak Ridge, Tennessee, from 1975 until 1989, when the final batch of W76 warheads was completed. After that, the facility was deactivated and finally slated for decommissioning by 1993. Only a small
pilot plant was left, which had been used to produce small batches of Fogbank for testing purposes. In 1996, the US government decided to replace, refurbish, or decommission large numbers of its nuclear weapons. Accordingly, the
Department of Energy established a refurbishment program to extend the
service lives of older nuclear weapons. In 2000, the NNSA specified a life-extension program for W76 warheads that would enable them to remain in service until at least 2040. With Facility 9404-11 long since decommissioned, a new production facility was required. Delays arose during its construction. Engineers repeatedly encountered failure in their efforts to produce Fogbank. Manufacture involves the moderately toxic, highly volatile
solvent acetonitrile, which presents a hazard for workers (causing three evacuations in March 2006 alone). In March 2007, engineers devised a manufacturing process for Fogbank. The material turned out to have problems when tested, and in September 2007 the Fogbank project was upgraded to "Code Blue" status by the NNSA, making it a major priority. The experience of
reverse engineering Fogbank produced some improvements in scientific knowledge of the process. The new production scientists noticed that certain problems in production resembled those noted by the original team. These problems were traced to a particular impurity in the final product that was required to meet quality standards. A
root cause investigation showed that input materials were subject to cleaning processes that had not existed during the original production run. This cleaning removed a substance that generated the required impurity. With the implicit role of this substance finally understood, the production scientists could control output quality better than during the original run. It is unclear whether the new W76-2 uses Fogbank. ==References==