SORRY FOR BEING LONG I HOPE SOME OF YOU MAY ENJOY READING THIS COMPILATION.
Not too many people know that neutrons were first studied (but not
recognized) in Germany. Two years before Chadwick's discovery Bothe and
Becker bombarded beryllium with alpha particles and noticed (with a Geiger
tube) a very penetrating radiation. They believed it was gamma. This led to
the Frederic and Irene Joliot Curie experiments in which an ionization
chamber was used instead of a G.M. tube. Placing a layer of paraffin in
front of their chamber they discovered a sudden increase of current. The
interpretation was that it was due to protons produced by photons of
unusually high energy. Chadwick was the first to say that protons were
produced by neutral particles.
And here is another discovered-but-not-recognized story. In the original
article (Naturwiss, 27,11,1939), which excluded Lise Meitner, Hahn and
Strassmann wrote that Ba was produced when U is bombarded by neutrons and
that they have no idea how can this happen. The interpretation of Ba as a
fission product was given by Meitner and Frisch (Nature, 143, 239, 471,
1939) who were the first to show that a lot of energy must be liberated
in the process. The expression "nuclear fission" was introduced by them to
describe the phenomenon.
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Here are other little-known facts surrounding that period. [As described by
Pierre Radvanyi and Monique Bordry in "Histoires d'Atomes", 1988 (ISBN-2-
7011-7712-9)]. Pierre, a retired nuclear physicist was the director
of the Laboratoire National Saturne. Monique still runs a smal Marie and
Pierre Curie "museum" at the Radium Institute in Paris. Give her my regards
if you decide to visit the place where radioactivity was discovered 101 years
ago.
1) Emission of neutrons in fission was simultaneously recognized by Joliot
at College de France and by Fermi+Szilard at Columbia University. Joliot's
number was 2 neutrons per event. Three fission chain reaction patents
ware deposited in France on May 2, 1939 (by Halban, Joliot, Kowarski and
Perin, in the name of "la Caisse National de la Recherche Scientific", the
predecessor of C.N.R.S.): on a device for generating energy through fission,
on a system to stabilize and control that device and on an explosive weapon.
2) On May 8 of 1939 Joliot obtained several tons of uranium oxide from
Belgium and at once started building a device in Ivry, near Paris. This
work was published when WW II had already started (Journal de Physique
et Le Radium, September 19, 1939). The first European reactor, named Zoe,
was built by Joliot in Ivry shortly after the end of the war.
3) Joliot realised that ordinary water absorbs too many neutrons and that
heavy water, available only in Norway was needed. A commando supported
by the French government was sent to Norway and 167 liters of this
precious material was obtained, at no cost, by very informal means.
The cargo was delivered to Oslo's airport; paperwork for sending it to
France via Amsterdam was prepared. But at the last minute the containers
were transferred to an airplane bound for Scotland. The plane flying to
Amsterdam was intercepted and forced to land in Hamburg, where it was
searched.
4) By ther time the heavy water arrived in Paris, the work had already been
suspended. The containers were smuggled by boat to England (by Halban and
Kowarski who were escaping from occupied France).
5) A colleague of Joliot's, after learning about the chain reaction in May
1939, used all his money to buy stocks in uranium mining. He sold them,
very profitably, to the U.S. government after the war.
6) The last paragraph of the Nobel Prize lecture of Joliot (1934) has an
interesting reference to a chain reaction which, if we are not careful,
can turn us into an exploding star. The prize was aworded to him, and to
his wife, for the discovery of artificial radioactivity. Incineration of
nuclear waste is an attempt to turn long-lived radioactive material,
mostly actinides, into substances which are either stable, or decay in
only couple of hundreds of years. Why should spent reactor fuel be
buried underground? We created it artificially and it is our obligation
to destroy it, for the benefit of future generations.
Ludwik Kowalski