reactorgrade

Reactor-grade is a non-formal term used to describe nuclear materials whose isotopic composition and impurity levels make them suitable for use in nuclear reactors, rather than optimized for weapons. It is commonly applied to uranium and plutonium, but there is no single internationally binding definition for what constitutes reactor-grade material. The label reflects intended use and processing history rather than a formal grade.

In uranium, reactor-grade typically refers to low-enriched uranium (LEU) used as reactor fuel, which has a modest increase in the fissile isotope U-235 above natural levels but well below weapons-grade enrichment. The exact enrichment depends on reactor design and fuel cycle choices, with many commercial reactors operating in the range of about 3% U-235. Some discussions also use “reactor-grade” to describe reprocessed or recycled uranium derived from spent fuel, where the enrichment is variable but not aimed at weapons-grade purity.

In plutonium, reactor-grade denotes plutonium produced in a reactor and separated from spent nuclear fuel that contains a broader mix of isotopes, including higher fractions of Pu-240, Pu-241, and Pu-242, rather than being dominated by Pu-239 as in weapons-grade plutonium. The presence of multiple isotopes makes it less suitable for weapons due to higher heat generation and spontaneous fission, but reactor-grade plutonium can still be used as reactor fuel, particularly in mixed-oxide (MOX) fuel assemblies.

Spent fuel and MOX usage illustrate practical applications: spent fuel may be recycled to recover fissile materials, while MOX uses reactor-grade plutonium to replace some uranium in reactors. The term’s meaning varies by context, and it is not a precise technical classification. Safeguards and nonproliferation considerations accompany discussions of reactor-grade materials.