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.

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).

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.