Nuclear Weapon Data (NWD) Categories

Subsets of Secret and Top Secret NWD relating to Restricted Data and/or Formerly Restricted Data concerning nuclear weapons, nuclear components, or nuclear explosive devices or materials. This information has been determined to require additional protection. The categories of NWD are:

(1) Sigma 14

(2) Sigma 15

(3) Sigma 18

(4) Sigma 20

Note 1: Not all NWD requires the additional protection of a Sigma category. NWD that is not in a Sigma category is referred to as Non-Sigma NWD. See Appendix A for details.

Note 2: Secret or Top Secret Restricted Data or Formerly Restricted Data in one of the Sigma Categories that is reviewed, downgraded or redacted to Confidential may retain the Restricted Data or Formerly Restricted Data designation but loses the Sigma Category designation.