[ RadSafe ] Book review: Plutonium: A History of the World's Most Dangerous Element

John Jacobus crispy_bird at yahoo.com
Thu May 3 08:24:44 CDT 2007

This review appears in Nature.

Nature 447, 31-33 (3 May 2007)

The dark heart of the bomb
John S. Rigden(1)

-Plutonium: A History of the World's Most Dangerous
by Jeremy Bernstein

Joseph Henry Press: 2007. 258 pp. £16.99 $27.95

Plutonium has either a celebrated or a tragic history,
depending on your point of view. It was the core of
the weapon that destroyed much of Nagasaki on 9 August
1945, and has only military uses. For those who find
security standing behind a stockpile of plutonium
bombs, the element is a reason to celebrate. By
contrast, for those who regard the bombing of Nagasaki
as a needless repetition of the Hiroshima catastrophe,
plutonium is a symbol of the US–Soviet arms race that
dominated the second half of the twentieth century. It
now signifies the rank and status of a nation's
military prowess.

In his book Plutonium, Jeremy Bernstein acknowledges
that everything connected with the element is
complicated, and that includes plutonium itself and
its history. Its discovery in 1941 by Glenn Seaborg
and Arthur Wahl is part of a much bigger story in
which each part becomes a story in itself.

Plutonium does not occur in earthen deposits, for
example; it is produced instead by the radioactive
decay of uranium by way of neptunium, and it is with
uranium that the book begins. Then there is the story
of the periodic table and the problems associated with
fitting the elements into their proper places —
especially the lanthanides (the elements of atomic
number 58 to 71 that follow lanthanum in the periodic
table) and the actinides (elements 90 to 103 following
actinium).There is the story of radioactivity (and the
connected story of the discovery of X-rays) and of
Enrico Fermi bombarding uranium nuclei with slow
neutrons. Add to these the story of fission, with
various elements and isotopes complicating the plot.
Los Alamos and the development of atomic bombs are
also a central part of the plutonium story. Finally,
there are the complications arising from the element
plutonium itself that must be understood and the
associated problems solved. Melding these many parts
into a short book represents a daunting challenge,
which Bernstein confronts head on.

One of the benefits of this multifaceted approach is
the opportunity it gives the author to educate readers
by means of historical information and thumbnail
sketches of interesting people. In his 1903 Nobel
address, for example, Henri Becquerel, who discovered
radioactivity, suggested that the energy associated
with radioactivity may involve the modification of
atoms in the radioactive material. Two years later,
Einstein showed that there was a loss of mass, which
becomes energy according to his famous equation E =
mc2. In 1934, Ida Noddack correctly criticized Fermi,
suggesting that in his neutron-bombardment experiments
he had actually discovered nuclear fission. Fermi's
Nobel speech in 1938 was wrong on this point because
he assumed he had discovered transuranic elements.
When the Nobel Prize was awarded for the discovery of
fission, the Nobel committee made so many erroneous
assumptions about who did what, and when, that Lise
Meitner was wrongly denied a share of the prize.

The tale of Fritz Houtermans is particularly
interesting and not well known. Houtermans wrote a
report in 1941 in which he considered the absorption
of a neutron by uranium-238 and concluded that it
would lead to plutonium via neptunium. He further
concluded that plutonium would be fissionable. Perhaps
generalizing from his own insights, he twice sent
messages (from his native Germany) to the Allies that
Germany was "on the track" to making plutonium. It
would be interesting to know why he did this, but
Bernstein says only that he wanted to "warn the
Allies". In any event, Houtermans was wrong: the
Germans were not close to making plutonium.

In early 1943, the Los Alamos laboratory — the home of
the Manhattan Project — began to take shape. By the
summer of 1944, plutonium started arriving there. The
element's idiosyncrasies and complexities soon became
apparent. William Zachariasen discovered that
plutonium had six different crystal structures, or
allotropes, which he labelled , , , , ' and . One of
these allotropes had to be formed into a metal
suitable for a bomb, which meant being stable and free
of isotopes that would interfere with a chain
reaction. The metallurgist Cyril Stanley Smith had the
good fortune and acute intuition (there were no data)
to select gallium to form an alloy with the  allotrope
of plutonium to produce the needed stability. It was
still unclear whether the  allotrope would revert to
the  allotrope before explosion. And a way of bringing
the two subcritical pieces of plutonium together to
form the critical mass — and initiate the chain
reaction that would lead to a nuclear explosion — had
to be developed from scratch, as the gun trigger used
for the uranium bomb that was dropped on Hiroshima was
not suitable. Plutonium, then, presented challenges at
every turn. As Bernstein suggests, it may have been
only the fear of what the Germans were doing that kept
the physicists working long into the night.

This book will make demands of readers. There are many
things to hold in the mind as Bernstein repeatedly
moves away from the main thrust of the book to develop
one of these side stories, which enrich the story of
plutonium but are also sometimes a distraction. But
Bernstein's writing ability smoothes the way and makes
this a successful book.

John S. Rigden is in the Department of Physics,
Washington University, St Louis, Missouri 63130, USA.

“We must face the fact that the United States is neither omnipotent or omniscient — that we are only 6 percent of the world’s population; that we cannot impose our will upon the other 94 percent of mankind; that we cannot right every wrong or reverse each adversity; and therefore there cannot be an American solution to every world problem.”
-- John F. Kennedy 

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

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