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How does uranium-238 become plutonium-239 inside a nuclear reactor?
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uranium processing
How uranium is enriched to make a nuclear weapon.
Inside a nuclear reactor, uranium-238āa fertile materialāis converted into the fissile isotope plutonium-239 through a process of neutron capture followed by radioactive decay.12
The transformation occurs in the following steps:
- Neutron Capture: A uranium-238 nucleus absorbs a neutron, becoming the isotope uranium-239.12
- First Beta Decay: Uranium-239 is unstable and undergoes beta decay (emitting an electron), which transforms it into neptunium-239 after approximately 23.5 minutes.12
- Second Beta Decay: Neptunium-239 subsequently undergoes a second beta decay, transforming into plutonium-239 after about 2.356 days.12
This process allows reactors to generate new fissile material from fertile fuel, a principle utilized in breeder reactors to extend fuel supplies. Once created, the plutonium can be recovered from irradiated fuel through the plutonium-uranium extraction (PUREX) process.132