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Weapons-grade plutonium is defined as being predominantly Pu-239, typically about 93% Pu-239. [24] Pu-240 is produced when Pu-239 absorbs an additional neutron and fails to fission. Pu-240 and Pu-239 are not separated by reprocessing.
Weapons-grade plutonium is defined as containing no more than 7% 240 Pu; this is achieved by only exposing 238 U to neutron sources for short periods of time to minimize the 240 Pu produced. Plutonium is classified according to the percentage of the contaminant plutonium-240 that it contains: Supergrade 2–3%; Weapons grade 3–7%; Fuel grade ...
A dedicated reactor operating on very low burnup (hence minimal exposure of newly formed plutonium-239 to additional neutrons which causes it to be transformed to heavier isotopes of plutonium) is generally required to produce material suitable for use in efficient nuclear weapons. While "weapons-grade" plutonium is defined to contain at least ...
Plutonium-240 has a high rate of spontaneous fission, raising the background neutron radiation of plutonium. Plutonium is graded by proportion of 240 Pu: weapons grade (<7%), fuel grade (7–19%) and reactor grade (>19%). Lower grades are less suited for bombs and thermal reactors but can fuel fast reactors.
Takeshi Ebisawa, 60, of Japan, pleaded guilty in Manhattan, New York, to conspiring with a network of associates to traffic nuclear materials, including uranium and weapons-grade plutonium, from ...
Weapon-grade plutonium therefore has plutonium-240 content limited to less than 7%. Supergrade plutonium has less than 4% of the 240 isotope, and is used in systems where the radioactivity is a concern, e.g. in the US Navy weapons which have to share confined spaces on ships and submarines with the crews.
The $1.8 billion project will aid in stockpile stewardship, a program designed to ensure the safety and reliability of the nation's nuclear weapons without the use of underground explosive testing.
Over the forty years of operation the site produced about 67.4 metric tons of plutonium, of which 54.5 metric tons was weapons-grade plutonium, supplying the majority of the 60,000 weapons in the U.S. arsenal. [136] [1] [2] In 1983 and 1984, 425 kilograms of weapons-grade plutonium was extracted from reactor-grade plutonium. [173]