Hot particle
Encyclopedia
A hot particle is a small, highly radioactive object, with significant content of radionuclide
s. Because radioactivity can be inherent to a substance or induced
, and there are many initial sources of radioactivity, hot particles can originate from a multitude of sources.
range in size from 10 nanometers to 20 micrometers, whereas particles present in local fallout are significantly larger (100 micrometers to several millimeters).
Hot particles can be identified by a Geiger counter
, or by autoradiograph
y i.e. fogging X-Ray film. Their age and origin can be determined by their isotopic signature
.
Due to their small size, hot particles maybe swallowed, inhaled or enter the body by other means. Significantly, due to close proximity with cells and chronic nature of exposure, the intensity and duration of radiological effects per particle are increased. It has been likened to the difference between having an x-ray, or swallowing the x-ray machine, while it continues delivering x-rays until expelled (Halving the distance between radiation and its source increases the intensity of the radiation by a factor of 4). Thus ingesting a hot particle may be a million times more dangerous than passing the same particle in the street. This is a long standing concern.
However, scientific consensus
studies (e.g. CERRIE) conclude that the current ICRP risk model, despite being largely derived from studies of survivors of external radiation, adequately estimate the risk of hot particles i.e. internal radiation is no more dangerous than an equal amount of externally delivered radiation. However, two members of CERRIE disagreed, notably Chris Busby who advocates several controversial physico-biological mechanisms that can vastly enhance the danger ingested particles e.g. Second Event Theory and Photoelectric Effect Theory.
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 or other nuclear fallout
resulting from detonations of a nuclear weapon
, 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.
(CERRIE), that was established by the UK Government, carried out a 3-year long independent expert review into the health risks of internal emitters (e.g. hot particles) and published its findings in 2003. CERRIE concluded there is no convincing evidence that the risks of internally delivered radiation differ from the risk projections derived from externally delivered radiation e.g. Japanese Atom Bomb survivors, and any differences between internal and external radiation are adequately accommodated by the established appropriate parameters (relative biological effectiveness
, kinetic factors) in physiological models. However, two members of CERRIE disagreed, notably Chris Busby who advocates several controversial physico-biological mechanisms that can vastly enhance the danger ingested particles e.g. Second Event Theory and Photoelectric Effect Theory.
Radionuclide
A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...
s. Because radioactivity can be inherent to a substance or induced
Induced radioactivity
Induced radioactivity occurs when a previously stable material has been made radioactive by exposure to specific radiation. Most radioactivity does not induce other material to become radioactive....
, and there are many initial sources of radioactivity, hot particles can originate from a multitude of sources.
Attributes
Hot particles contained in far traveled nuclear falloutNuclear fallout
Fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and shock wave have passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes...
range in size from 10 nanometers to 20 micrometers, whereas particles present in local fallout are significantly larger (100 micrometers to several millimeters).
Hot particles can be identified by a Geiger counter
Geiger counter
A Geiger counter, also called a Geiger–Müller counter, is a type of particle detector that measures ionizing radiation. They detect the emission of nuclear radiation: alpha particles, beta particles or gamma rays. A Geiger counter detects radiation by ionization produced in a low-pressure gas in a...
, or by autoradiograph
Autoradiograph
An autoradiograph is an image on an x-ray film or nuclear emulsion produced by the pattern of decay emissions from a distribution of a radioactive substance...
y i.e. fogging X-Ray film. Their age and origin can be determined by their isotopic signature
Isotopic signature
An isotopic signature is a ratio of stable or unstable isotopes of particular elements found in an investigated material...
.
Due to their small size, hot particles maybe swallowed, inhaled or enter the body by other means. Significantly, due to close proximity with cells and chronic nature of exposure, the intensity and duration of radiological effects per particle are increased. It has been likened to the difference between having an x-ray, or swallowing the x-ray machine, while it continues delivering x-rays until expelled (Halving the distance between radiation and its source increases the intensity of the radiation by a factor of 4). Thus ingesting a hot particle may be a million times more dangerous than passing the same particle in the street. This is a long standing concern.
However, scientific consensus
Scientific consensus
Scientific consensus is the collective judgment, position, and opinion of the community of scientists in a particular field of study. Consensus implies general agreement, though not necessarily unanimity. Scientific consensus is not by itself a scientific argument, and it is not part of the...
studies (e.g. CERRIE) conclude that the current ICRP risk model, despite being largely derived from studies of survivors of external radiation, adequately estimate the risk of hot particles i.e. internal radiation is no more dangerous than an equal amount of externally delivered radiation. However, two members of CERRIE disagreed, notably Chris Busby who advocates several controversial physico-biological mechanisms that can vastly enhance the danger ingested particles e.g. Second Event Theory and Photoelectric Effect Theory.
Origin
Radiation can spread from a more radioactive substance to a less radioactive one by the processes of neutron activationNeutron activation
Neutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus often decays immediately by emitting particles such as neutrons, protons, or alpha...
and photodisintegration
Photodisintegration
Photodisintegration is a physical process in which an extremely high energy gamma ray interacts with an atomic nucleus and causes it to enter an excited state, which immediately decays by emitting a subatomic particle. A single proton or neutron is effectively knocked out of the nucleus by the...
; this induced radioactivity
Induced radioactivity
Induced radioactivity occurs when a previously stable material has been made radioactive by exposure to specific radiation. Most radioactivity does not induce other material to become radioactive....
increases the potential number of hot particle sources.
Hot particles released into the environment may originate in nuclear reactors. The Chernobyl disaster
Chernobyl disaster
The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in Ukraine , which was under the direct jurisdiction of the central authorities in Moscow...
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 or other nuclear fallout
Nuclear fallout
Fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and shock wave have passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes...
resulting from detonations of a nuclear weapon
Nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...
, 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
Qaanaaq
Qaanaaq is the main town in the northern part of the Qaasuitsup municipality in northwestern Greenland. It is one of the northernmost towns in the world. The inhabitants of Qaanaaq speak the West Greenlandic language and many also speak Inuktun. The town has a population of 626 as of 2010...
), releasing hot particles.
Health Effects
The Committee Examining Radiation Risks of Internal EmittersCommittee on Medical Aspects of Radiation in the Environment
The Committee on Medical Aspects of Radiation in the Environment is a UK-wide advisory committee set up by the British government...
(CERRIE), that was established by the UK Government, carried out a 3-year long independent expert review into the health risks of internal emitters (e.g. hot particles) and published its findings in 2003. CERRIE concluded there is no convincing evidence that the risks of internally delivered radiation differ from the risk projections derived from externally delivered radiation e.g. Japanese Atom Bomb survivors, and any differences between internal and external radiation are adequately accommodated by the established appropriate parameters (relative biological effectiveness
Relative biological effectiveness
In radiology, the relative biological effectiveness is a number that expresses the relative amount of damage that a fixed amount of ionizing radiation of a given type can inflict on biological tissues...
, kinetic factors) in physiological models. However, two members of CERRIE disagreed, notably Chris Busby who advocates several controversial physico-biological mechanisms that can vastly enhance the danger ingested particles e.g. Second Event Theory and Photoelectric Effect Theory.