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.
- Strategic SNM (SSNM)
- SNM of moderate strategic significance
- 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.