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IAEA Categorization of Nuclear Material

Material	Form	Category I	Category II	Category III
1. Plutonium^a	Unirradiated^b	2 kg or more	Less than 2 kg, but more than 500 g	500 g or less, but more than 15 g
2. Uranium-235	Unirradiated^b - uranium enriched to 20% ²³⁵U or more	5 kg or more	Less than 5 kg, but more than 1 kg	1 kg or less, but more than 15 g
	- uranium enriched to 10% ²³⁵U, but less than 20% ²³⁵U	NA	10 kg or more	less than 10 kg, but more than 1 kg
	- uranium enriched above natural, but less than 10% ²³⁵U	NA	NA	10 kg or more
3. Uranium-233	Unirradiated^b	2 kg or more	Less than 2 kg, but more than 500 g	500 g or less, but more than 15 g
4. Irradiated Fuel (The categorization of irradiated fuel in the table is based on international transport considerations. The State may assign a different category for domestic use, storage, and transport taking all relevant factors into account)	NA	NA	Depleted or natural uranium, thorium, or low-enriched fuel (less than 10% fissile content)^d/e	NA

All plutonium except that with isotopic concentration exceeding 80% in plutonium-238.
Material not irradiated in a reactor or material irradiated in a reactor but with a radiation level equal to or less than 1 Gy/hr
Quantities not falling in Category III and natural uranium, depleted uranium and thorium should be protected at least in accordance with prudent management practice.
Although this level of protection is recommended, it would be open to States, upon evaluation of the specific circumstances, to assign a different category of physical protection.
Other fuel which by virtue of its original material content is classified as Category I or II before irradiation may be reduced one category level while the radiation level from the fuel exceeds 1 Gy/hr (100rad/hr) at one meter unshielded.