Report a Safety Concern
Search

The U.S. Nuclear Regulatory Commission is in the process of rescinding or revising guidance and policies posted on this webpage in accordance with Executive Order 14151 Ending Radical and Wasteful Government DEI Programs and Preferencing, and Executive Order 14168 Defending Women From Gender Ideology Extremism and Restoring Biological Truth to the Federal Government. In the interim, any previously issued diversity, equity, inclusion, or gender-related guidance on this webpage should be considered rescinded that is inconsistent with these Executive Orders.

Home Nuclear Security Domestic Safeguards Material Control and Accounting

Safeguard Categories of SNM

NRC divides special nuclear material (SNM) into three main categories, according to the risk and potential for its direct use in a clandestine fissile explosive or for its use in the production of nuclear material for use in a fissile explosive.

  1. Strategic SNM (SSNM)
  2. SNM of moderate strategic significance
  3. SNM of low strategic significance

Category I, Strategic SNM (SSNM)

Strategic special nuclear material means

  • Uranium-235 (contained in uranium enriched to 20 percent or more in the U-235 isotope),
  • Uranium-233, or
  • Plutonium.

Category I, SSNM means SSNM in any combination in a quantity of

  • 2 kgs or more of plutonium; or
  • 5 kgs or more of U-235 (contained in uranium enriched to 20 percent or more in the U-235 isotope); or
  • 2 kgs or more of U-233; or
  • 5 kgs or more in any combination computed by the equation grams = (grams contained U-235) + 2.5 (grams U-233 + grams plutonium).

This is often referred to as a formula quantity.

To top of page

Category II, Special nuclear material of moderate strategic significance

Category II, Special nuclear material of moderate strategic significance means

  • Less than a formula quantity of strategic special nuclear material but more than 1,000 grams of uranium-235 (contained in uranium enriched to 20 percent or more in the U-235 isotope) or more than 500 grams of uranium-233 or plutonium, or in a combined quantity of more than 1,000 grams when computed by the equation grams = (grams contained U-235) + 2 (grams U-233 + grams plutonium); or
  • 10,000 grams or more of uranium-235 (contained in uranium enriched to 10 percent or more but less than 20 percent in the U-235 isotope).

To top of page

Category III, Special nuclear material of low strategic significance

Category III, Special nuclear material of low strategic significance means

  • Less than an amount of special nuclear material of moderate strategic significance (see category II above) but more than 15 grams of uranium-235 (contained in uranium enriched to 20 percent or more in U-235 isotope) or 15 grams of uranium-233 or 15 grams of plutonium or the combination of 15 grams when computed by the equation grams = (grams contained U-235) + (grams plutonium) + (grams U-233); or
  • Less than 10,000 grams but more than 1,000 grams of uranium-235 (contained in uranium enriched to 10 percent or more but less than 20 percent in the U-235 isotope); or
  • 10,000 grams or more of uranium-235 (contained in uranium enriched above natural but less than 10 percent in the U-235 isotope).

For information on how the three categories of SNM are controlled and accounted for, see Material Control and Accounting.

To top of page

Page Last Reviewed/Updated Wednesday, March 11, 2020