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PLUTONIUM

SHENDA M. BAKER, HARVEY MUDD COLLEGE

Plutonium has my nomination for "Most Influential Element of the 21st Century." Clearly, my choice is premature and predictive, as not even a tenth of this century has yet passed, but already the ascendancy of plutonium is apparent. It motivates international policy decisions and incites national debate. On a local level, issues of plutonium raise hackles and require definition of state and transportation views. As a simple element, plutonium is multifaceted, being extolled as a tremendous source of energy, feared as an impossibly long-lived waste dilemma, and equally denounced as an uncontrollable force. Plutonium isn't going anywhere anytime soon. It's a heavy hitter, in name as well as mass, carrying with it a preponderance of insinuation.

Consider the evocative power of plutonium. The word sends writers and science fiction readers as well as designers of cutting-edge comics into the most extreme realm of space adventures and intrigue. "Plutonium Man" was given that special last-place listing of seven newly minted Metal Men (and even an exclamation point!) when created in 1963 (No. 2, June July, page 15). A current Web-based detective story, "Plutonium Blonde," goes a step beyond the mere "platinum blonde" who simply cannot compete with the magnitude of prowess and cunning of a true plutonium blonde. These characters revel in mystery and strange powers. If Calvin and Hobbes dash off to confront "demented, drooling, bug-eyed, plutonium space demons from Zarg," it seems much more adventurous than tackling nickel-based space demons. Indeed, plutonium elevates the imagination to another level.

Plutonium isn't much to look at. Rather dull and silvery gray, plutonium doesn't hold the luster of precious metals or reflect the light like carbon's most precious form. Brave adventurers didn't seek lost cities in search of plutonium. It's not a keepsake that anyone desires to hold onto forever. Other radioactive elements, uranium as the most obvious example, seem tame relative to plutonium, never achieving the mythical status to which plutonium has risen. And yet, the unwanted becomes "America's Most Wanted" in a world in turmoil, and as such becomes even more influential.

Perhaps uranium seems less mysterious because it is not "synthetic." Since we dig uranium out of the earth, we feel less ownership of its darker side. But because plutonium is not "natural," it has status as a man-made phenomenon. Note that uranium contains only one naturally occurring isotope that will sustain a nuclear chain reaction using normal water to moderate and reflect neutrons: 235U.

HANDLE WITH CARE Technicians make plutonium fuel pellets in a glove box.
ENERGY DEPARTMENT/SCIENCE PHOTO LIBRARY
Whereas this isotope is present in low abundance (0.72%), requiring enrichment to 3% or greater for effective use in commercial nuclear reactors, 2 billion years ago, the natural abundance of 235U was approximately 3%. Radiological evidence indicates that an underground uranium deposit in Oklo, Gabon, Africa, achieved nuclear criticality and operated for tens of thousands of years, stopping and restarting as groundwaters ebbed and flowed throughout the centuries. Apparently, 239Pu was produced in measurable quantities, suggesting that humans were not the first to create plutonium. Nature may again serve as a model for our own understanding of waste treatment, as the heaviest elements from this natural reactor did not spread but rather settled to the bottom of the riverbed and stayed there, the lighter elements being swept downstream.

Plutonium is the stuff of great dreams and great nightmares, a most mysterious of elements, its myriad phases still evading corroboration by even the hardiest of materials scientists. I imagine it morphing and slithering just to stay one step ahead of us. And yet I have never been afraid of plutonium. Of people and their motives, I have a great deal of concern. Still, I cannot help but feel overwhelming awe for the scientific accomplishments of a people under great duress who ultimately put plutonium in a tight bottle and sought to end a war.

So what's the bottom line? Plutonium is a fissile material, a rather homely, overweight element that contains approximately 1-MW-day of heat per g. By extension, the heat energy contained in our nuclear stockpile is more than enough to completely fuel the economies of Western Europe, Canada, Japan, and the U.S. for a year.

From weapons, energy, international relations, national politics, and waste storage to the extremes of imaginary personalities, dreams of star flight, and nightmares of annihilation, plutonium is a major player. Plutonium is getting my vote for the most influential element--now all we need is the contest.


Shenda M. Baker is a chemistry professor at Harvey Mudd College, where she enjoys doing and contemplating undergraduate teaching and research. She is currently exploring science policy and promoting basic and defense science at the national laboratories.


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PLUTONIUM AT A GLANCE
Name: Named after the planet Pluto.
Atomic mass: (244).
History: Discovered by Glenn T. Seaborg and colleagues in Berkeley, Calif., in 1940; however, their results were classified until 1946.
Occurrence: Found in minute amounts in uranium ores.
Appearance: Silvery solid.
Behavior: Plutonium is highly radiotoxic. A large piece will boil water.
Uses: Can be used as a nuclear explosive or as a nuclear fuel.

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