Chemistry

An Overview about the Chemical Element Plutonium



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Plutonium bears a name descended from the name of the Roman god of Hell. The name was not chosen by scientists being dramatic, however. It simply came next in the naming sequence scientists were following. In the periodic table, plutonium comes after neptunium. In the solar system, Pluto was, at the time, the next planet out from Neptune. (It has been demoted since, of course.) So the name has nothing to do with the underworld, but still seems to suit an element which to the average citizen carries connotations only of poison and death.

At the University of California at Berkeley in 1941, Glenn Seaborg led a group of researchers who bombarded natural uranium with deuterons, nuclei of heavy hydrogen atoms. This increased the weight of the uranium and made it unstable. It decayed quickly into a new element, which they named neptunium. Neptunium decayed too, as scientists had predicted it would, and the element produced by the decay was named plutonium.

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Plutonium, symbol Pu, atomic number 94, atomic weight 244, is poisonous. It throws off deadly radioactivity as it decays into lighter elements. It's an actinide metal which is solid at room temperature and melts at 1184 degrees Fahrenheit. It does exist in nature as it turns out, but only in the minutest quantities. Most of the plutonium in existence is man-made. It is used in nuclear weapons, in a few reactors, and also to power space probes that travel beyond the range of the sun's radiation. Its potential use in nuclear weapons makes it a substance which has to be carefully guarded.

Extreme precautions should be taken, and are, with plutonium. However, contrary to common belief, plutonium is no more poisonous by nature than lead or any other heavy metal. It is also considerably less toxic, per weight, than many biological agents such as ricin, anthrax, and tetanus toxin. The problem with plutonium is storage and disposal, because the poison nature of plutonium persists.

Plutonium storage is a security problem for the long term because one isotope of plutonium has a half life of 24,110 years. It is hard to imagine the storage system that could keep anything safe for even that length of time. But any fissionable plutonium must be stored for far longer than that. The length of a half life only describes how long it will be before half the substance remains. If a gram of plutonium is buried away, after 24,110 years half a gram of plutonium will remain. Another 24,110 years and there is still one quarter gram where distant ancestors left it, unless geologic forces have dispersed it. That amount will have the radioactive products of its decay all around it, and will decay again. And so on, down the long centuries.

This is a tremendous practical problem, as well as a moral one. The United Statesdparams.getadspec('c_billboard1'); is currently storing fissionable materials left over from the Cold War. So are several other nations. One suggested solution is using diluted fissionable plutonium in nuclear power plants, in essence burning it up and at the same time contaminating it with less reactive material to the point that it can't explode. Another idea is mixing fissionable plutonium with more immediately toxic radioactive elements to keep potential thieves away. Right now, governments store plutonium, very mindfully, and study their options.

Fissionable plutonium has killed no one in peacetime through their eating or inhaling it. It has, however, killed. There have been incidents during which plutonium has reached critical mass (the quantity at which it begins to shoot out lethal radiation) by accident, several times. Almost all of the victims have been scientists, some of whom bravely wrote reports about their experience as they died. There was also an incident in which fissionable plutonium caught fire.

Plutonium is dangerous, there's no doubt. As a society, we need to find ways to minimize its dangers, and to use it, if we must, with great care.

http://members.tripod.com/~Arn old_Dion/Daghlian/accident.htm l

http://web.archive.org/web/200 60929015050/http://www.llnl.go v/csts/publications/sutcliffe/

http://www.fas.org/sgp/othergo v/doe/lanl/pubs/00818006.pdf

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