I recall a teenager on the old Donahue Show who wrote a book called “Mushroom”. It showed how to build an Atomic Bomb. He used information that he got from the Library of Congress. The only thing that he couldn’t find was the detonator, so he called Dupont and they told him the Army uses Kryton.
Kryton? What's that?
HMX, RDX, and PETN would be more likely answers. A krytron is a vacuum tube capable of switching a high current on very suddenly. It is used to fire the exploding bridgewire detonators attached to the explosive lenses that surround the plutonium core. These have to go off at precisely the same instant in order to ensure a blast wave symmetric enough to compress the core properly.
In 2002, a guy got 40 months for shipping 100 krytrons to Israel in 1982.