Refined plutonium over 93% is called which grade?

Refined plutonium over 93% is called which grade?

• A. Reactor grade plutonium
• B. Mixed oxide plutonium
• C. Weapons grade plutonium
• D. Not usable plutonium

Answer: (C)

The key idea is isotopic purity and its impact on weapon usability. When plutonium is refined to a very high fraction of Pu-239—typically around 93% or more with only tiny amounts of Pu-240 and other isotopes—it becomes suitable for reliably sustaining a fission chain reaction in a weapon. Pu-239 is the fissile isotope needed for fast, predictable fission, while Pu-240 tends to undergo spontaneous fission and releases heat, which complicates weapon design and performance. That high Pu-239 content and low impurity make the material “weapons-grade.” Reactor-grade plutonium has a substantial amount of Pu-240 and other isotopes, which increases unwanted spontaneous fission and heat, so it’s not ideal for weapons. Mixed oxide plutonium (MOX) is simply a fuel form—plutonium blended with uranium oxides used in reactors, not a grade of plutonium. The term “not usable” isn’t a standard category for plutonium grades. So, refined plutonium over about 93% Pu-239 is called weapons-grade plutonium.

The key idea is isotopic purity and its impact on weapon usability. When plutonium is refined to a very high fraction of Pu-239—typically around 93% or more with only tiny amounts of Pu-240 and other isotopes—it becomes suitable for reliably sustaining a fission chain reaction in a weapon. Pu-239 is the fissile isotope needed for fast, predictable fission, while Pu-240 tends to undergo spontaneous fission and releases heat, which complicates weapon design and performance. That high Pu-239 content and low impurity make the material “weapons-grade.”

Reactor-grade plutonium has a substantial amount of Pu-240 and other isotopes, which increases unwanted spontaneous fission and heat, so it’s not ideal for weapons. Mixed oxide plutonium (MOX) is simply a fuel form—plutonium blended with uranium oxides used in reactors, not a grade of plutonium. The term “not usable” isn’t a standard category for plutonium grades.

So, refined plutonium over about 93% Pu-239 is called weapons-grade plutonium.