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How is plutonium-239 produced from uranium-238 in nuclear reactors?
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atomic bomb
The first atomic bomb test, near Alamogordo, New Mexico, July 16, 1945.
Plutonium-239 is produced from uranium-238 through a process of neutron capture followed by two stages of beta decay within a nuclear reactor.12
The transformation occurs in the following steps:
- Neutron Capture: A uranium-238 nucleus absorbs a neutron to become the isotope uranium-239, releasing a gamma ray in the process.13
- First Beta Decay: Uranium-239 is unstable and undergoes negative beta-particle decay, emitting an electron to transform into neptunium-239. This typically occurs with a half-life of approximately 23.5 minutes.123
- Second Beta Decay: Neptunium-239 is also unstable and undergoes a second beta decay, transforming into plutonium-239. This step has a half-life of about 2.356 days.12
Once produced, the plutonium can be separated from the remaining uranium and fission products using the plutonium-uranium extraction (Purex) process. In the context of nuclear weapons, production reactors are often operated to ensure quick fuel throughput, which minimizes the buildup of the undesirable contaminant plutonium-240.24