The REAL secret is retired weapon designers are worried about the W76 warhead.
The Pit was so small it was right on the edge of not working.
Instaled in Trident I 8x MIRV
"The W76-1 life extension program for refurbishing the original W76-0 warheads is described as an "excellent program" that meets the Navy's needs, with no changes that put the warhead's basic nuclear design at risk. Great care was taken to replicate the original components and processes as closely as possible."