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Nuclear Safeguards Education Portal

Significant quantity

Photo related to the term with caption below

About three kilograms of fresh highly enriched uranium (HEU).

(Source: Petr Pavlicek/IAEA)

Significant quantity (SQ) is the approximate amount of nuclear material for which the possibility of manufacturing a nuclear explosive device cannot be excluded. Significant quantities take into account unavoidable losses due to conversion and manufacturing processes and should not be confused with critical masses. Significant quantities are used in establishing the quantity component of the IAEA inspection goal. Significant quantity values currently in use are given in the table below.

Material SQ
Direct use nuclear material
Pua 8 kg Pu
233U 8 kg 233U
HEU (235U > 20%) 25 kg 235U
Indirect use nuclear material
U(235U < 20%)b 75 kg 235U
(or 10 t natural U
or 20 t depleted U)
Th 20 t Th
aFor Pu containing less than 80% 238Pu.
bIncluding low enriched, natural, and depleted uranium.