A category of NWD that includes information that would allow or significantly facilitate a proliferant nation or entity to fabricate a credible nuclear weapon or nuclear explosive based on a proven, certified, or endorsed U.S. nuclear weapon or device. This information would enable the establishment or improvement of nuclear capability without nuclear testing or with minimal research and development. The NNSA or successor organization determines which information is placed in the Sigma 18 category. The following is the list of Sigma 18 information.
(1) Complete design of a gun-assembled weapon.
(2) Complete design of a primary or single stage implosion-assembled weapon.
(3) Complete design of an interstage or secondary.
(4) Weapon design codes with one-dimensional (1D) hydrodynamics and radiation transport with fission and/or thermonuclear burn.
(5) Weapon design codes with two-dimensional (2D) and three-dimensional (3D) capabilities.