(Well, thats not true. I learned most of this in the mid 90s from the Internet, but only because I went looking for it).

The BBC has a series of diagrams and explainations describing:

-The Mining of Uranium
-Converting and Enriching Uranium
-Design of gun-type Nuclear bombs
-Nuclear power plants
-Reprocessing nuclear waste in "breeder" reacters
-Design of implosion-type Thermonuclear bombs

I quick look on Wikipedia (http://en.wikipedia.org) turns up much more detailed descriptions of enrichment (no chemical formulas, though any graduate chemistry book should have the need reactions). Also includes many more designs to cause a mass to go critical.

http://en.wikipedia.org/wiki/Nuclear_weapon_design

Here is something odd:

SADM - Backpack sized nuclear weapon to be parachuted in with special forces to take out a hardor or dam. (http://en.wikipedia.org/wiki/Special_Atomic_Demolition_Munition)

BBC: From the mine to the bomb, or everything I ever wanted to know about building nuclear weapons but no one in the US would print