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How does radioactive fallout form after a nuclear explosion?
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nuclear weapon
A test of a U.S. thermonuclear weapon (hydrogen bomb) at Enewetak atoll in the Marshall Islands, November 1, 1952.
Radioactive fallout forms when radioactive materials, primarily fission products created during a nuclear explosion, are dispersed into the atmosphere and subsequently deposited on Earth.12
During the detonation, the intense energy release produces various radioisotopes. In addition to these fission products, other materials in the vicinity of the blast can become radioactive through exposure to the explosion's radiation. The resulting fallout is categorized based on the size of the particles and the altitude to which they are lofted:2
- Local fallout: Consists of larger radioactive particles that settle near the explosion site shortly after detonation.1
- Tropospheric fallout: Involves finer particles that enter the troposphere. These are deposited over a wider area, typically within the month following the explosion, influenced by local meteorological conditions.1
- Stratospheric fallout: Composed of extremely fine particles that reach the stratosphere. This material can remain airborne for years and be distributed globally before eventually mixing back into the troposphere to settle on the surface.1
These particles reach the ground through gravity, electrical attraction, or by attaching to larger matter like water droplets.1