Hot particle

A hot particle is a small, highly radioactive object, with significant content of radionuclides. Hot particles are usually released into the environment during a nuclear accident or when high-level radioactive waste is improperly handled, and are the principal hazard of the nuclear fallout from nuclear explosions. They are an important component of radioactive contamination.

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The size of hot particles contained in nuclear fallout ranges from 10 nanometers to 20 micrometers for the worldwide fallout; local fallout particles are significantly bigger (100 micrometers to several millimeters).

Hot particles can consist of tiny specks (~10 micrometers sized) of nuclear fuel (so-called fuel fleas due to their tendency to become electrically charged and then jump from surface to surface), or of other material activated by exposition to neutron radiation.

Hot particles can be identified by a Geiger counter, or by autoradiography. Their age and origin can be determined by their isotopic signature.

Hot particles present significant health hazard when ingested or entered the body by other means.

The Chernobyl disaster was a major source of hot particles.