Plutonium

Precautions

All isotopes and compounds of plutonium are toxic and radioactive. While plutonium is sometimes described in media reports as "the most toxic substance known to man", there is general agreement among experts in the field that this is incorrect. As of 2003, there has yet to be a single human death officially attributed to plutonium exposure. Naturally-occurring radium is about 200 times more radiotoxic than plutonium, and some organic toxins like Botulin toxin are still more toxic. Botulin toxin, in particular, has a lethal dose of 300pg/kg, far less than the quantity of plutonium that poses a significant cancer risk. In addition, beta and gamma emitters (including the C-14 and K-40 in nearly all food) can cause cancer on casual contact, which alpha emitters cannot.

Related Topics:
Toxic - Radium - Botulin toxin

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Orally, plutonium is less toxic (non-oncogenically speaking) than several common substances, including caffeine, acetaminophen, some vitamins, pseudoephedrine, and any number of plants and fungi. It is perhaps somewhat more toxic than pure ethanol, but less so than tobacco and many illegal drugs (some such as marijuana are negligibly toxic). From a purely chemical standpoint, its toxicity is probably on par with lead and other heavy metals.

Related Topics:
Oncogenic - Caffeine - Acetaminophen - Vitamin - Pseudoephedrine - Plant - Fungi - Ethanol - Tobacco - Marijuana - Lead - Heavy metals

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That said, there is no doubt that plutonium may be extremely dangerous when handled incorrectly. The alpha radiation it emits does not penetrate the skin, but can irradiate internal organs when plutonium is inhaled or ingested. Particularly at risk are the skeleton, onto the surface of which it is likely to be absorbed, and the liver, where it will collect and become concentrated. Extremely fine particles of plutonium (on the order of micrograms) can cause lung cancer if inhaled into the lungs.

Related Topics:
Alpha - Skeleton - Liver - Lung cancer - Lung

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Other substances including ricin, botulinum toxin and tetanus toxin are fatal in doses of (sometimes far) under one milligram, and others (the nerve agents, the amanita toxin, the fugu toxin) are in the range of a few milligrams. As such, plutonium is not unusual in terms of toxicity, even by inhalation. In addition, those substances are fatal in hours to days, whereas plutonium (and other cancer-causing radioactives) give an increased chance of illness decades in the future. Considerably larger amounts may cause acute radiation poisoning and death if ingested or inhaled; however, so far, no human is known to have immediately died because of inhaling or ingesting plutonium and many people have measurable amounts of plutonium in their bodies.

Related Topics:
Ricin - Botulinum - Tetanus - Amanita - Fugu - Radiation poisoning

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The chemical and radiological toxicity of plutonium should be distinguished from each other and also from the potential danger of a runaway fission reaction or "criticality". Many in the anti-nuclear movement and in the continuing green politics movement refer to plutonium as the most dangerous substance known to man because of its use in nuclear power plants, which they perceive to be inherently dangerous, and for its potential as a catalyst for nuclear weapons proliferation.

Related Topics:
Anti-nuclear movement - Green politics

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It is possibly confusion between these two issues that has led to sensational exaggerations of plutonium toxicity. A 1989 paper by Bernard L. Cohen states:

Related Topics:
Sensational exaggerations - Bernard L. Cohen

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:Pu hazards are far better understood than , and the one fatality per 300 years they may someday cause is truly trivial by comparison. In spite of the facts we have cited here, facts well known in the scientific community, the myth of Pu toxicity lingers on. (MS Word) (html)

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It must be noted, however, that in contrast to naturally occurring radioisotopes such as radium or C-14, plutonium was manufactured, concentrated, and isolated in large amounts (hundreds of metric tons) during the Cold War for weapons production. These piles, whether in weapons form or otherwise, could pose a significant toxicologic risk, largely because, unlike chemical or biological agents, there is no practical way to destroy them.

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Toxicity issues aside, care must be taken to avoid the accumulation of amounts of plutonium which approach critical mass. Despite not being confined by external pressure as is required for a nuclear weapon, it will nevertheless heat itself and break whatever confining environment it is in. Shape is relevant; compact shapes such as spheres are to be avoided. Plutonium in solution is more likely to form a critical mass than the solid form. A weapon-scale nuclear explosion cannot occur accidentally, since it requires a greatly supercritical mass in order to explode rather than simply melt or fragment. However, a marginally critical mass will cause a lethal dose of radiation and has in fact done so in the past on several occasions.

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Multiple criticality accidents have occurred in the past at least in the US and the former USSR, some of them with lethal consequences. Careless handling of a 6.2 kg plutonium sphere resulted in a lethal dose of radiation at Los Alamos on August 21, 1945, when scientist Harry Daghlian received a dose estimated to be 510 rems (5.1 Sv) and died four weeks later. Nine months later, another Los Alamos scientist, Louis Slotin, died from a similar accident. In 1958, during a process of purifying plutonium at Los Alamos, a critical mass was formed in a mixing vessel, which resulted in the death of a crane operator. Other accidents of this sort have occurred in the Soviet Union, Japan, and many other countries. (See List of nuclear accidents)

Related Topics:
Criticality accident - August 21 - 1945 - Harry Daghlian - Rems - Sv - Louis Slotin - 1958 - Soviet Union - Japan - List of nuclear accidents

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Metallic plutonium is also a fire hazard, especially if the material is finely divided. It reacts chemically with oxygen and water which may result in an accumulation of plutonium hydride, a pyrophoric substance; that is, a material that will ignite in air at room temperature. Plutonium expands considerably in size as it oxidizes and thus may break its container. The radioactivity of the burning material is an additional hazard. Magnesium oxide sand is the most effective material for extinguishing a plutonium fire. It cools the burning material, acting as a heat sink, and also blocks off oxygen. Water is also effective. There was a major plutonium-initiated fire at the Rocky Flats Plant near Boulder, Colorado in 1969 http://tis.eh.doe.gov/techstds/standard/hdbk1081/hbk1081f.html#ZZ39. To avoid these problems, special precautions are necessary to store or handle plutonium in any form; generally a dry inert atmosphere is required http://tis.eh.doe.gov/techstds/standard/hdbk1081/hbk1081d.html#ZZ28.

Related Topics:
Plutonium hydride - Pyrophoric - Heat sink - Rocky Flats Plant - Boulder, Colorado - 1969 - Inert - Atmosphere

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