Hot particles

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A hot particle is a small, highly radioactive object, with significant content of radionuclides. Because radioactivity can be inherent to a substance or induced, and there are many initial sources of radioactivity, hot particles can from a multitude of sources.

Attributes

Hot particles present significant health hazard when ingested or entered the body by other means. They are several orders of magnitude more dangerous than the same amount of radiation emitted from a large source over the whole body because if ingested or inhaled, they do damage to cells at close proximity.

The size of hot particles contained in nuclear fallout ranges from 10 nanometers to 20 micrometers for the worldwide fallout; particles present in local fallout are significantly larger (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 exposure 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.

Origin

Radiation can spread from a more radioactive substance to a less radioactive one by the processes of neutron activation and photodisintegration; this induced radioactivity increases the potential number of hot particle sources.

Hot particles released into the environment may originate in nuclear reactors. The Chernobyl disaster was a major source of hot particles, as the core of the reactor was breached, but hot particles are found near undamaged nuclear reactors as well.

They also are a component of the black rain (WP) or other nuclear fallout resulting from detonations of a nuclear weapon (WP), including the more than 2000 nuclear weapons tests in the mid-20th century.

Atomic testing included safety trials of the devices using radioactive material which was not detonated; fissile material was sometimes dispersed, including plutonium vapor, plutonium aerosols of various sizes, plutonium oxide particulates, plutonium-coated particles, and sizeable lumps of plutonium-contaminated structural material.

Accidents involving the nuclear engines, themselves usually called nuclear reactors, used in submarines, satellites, and other devices, usually crashes or malfunctions of other systems, can be a source. The crash of the nuclear reactor of the Kosmos 954 satellite, which failed to separate from the rest of the craft and entered a decaying orbit, released hot particles.

Accidents during transportation of nuclear weapons or nuclear waste is a potential source. A Boeing B-52 Stratofortress nuclear-armed bomber crashed in the area of the northwest Greenland town of Thule (since renamed to Qaanaaq) , releasing hot particles.

See also

Further reading

Tamplin & Cochran 1974 The scientific theory known as the "Hot particle hypothesis" or "Hot particle problem", that stipulates that a given amount of radiation dispersed through a large area of the body is less likely to cause cancers than the same amount directed to a small area, as happens with hot particles. Article by the theory's originators