pdf - WHALE

obtaining a uranium atom bomb in their program. After all, the
American Manhattan Project had elected to pursue both a uranium
and a plutonium bomb. The theoretical possibility of plutonium
bombs - "element 94" as it was officially called in German
documents of the period - was certainly known to the Nazis. And,
as the early 1942 memorandum to the Heereswaffenamt also makes
clear, the Germans also knew that this element could only be
synthesized in an atomic reactor.
So why did they apparently concentrate only on a uranium
bomb and isotope separation and enrichment almost exclusively
With the destruction of the Norwegian heavy water plant at Ryukon
in 1942 by Allied commandos, and German failures in obtaining
sufficient purity of graphite for use as a moderator in a reactor, the
only other moderator available to them - heavy water - was now in
critically short supply. Thus, according to the Legend, a functioning
reactor leading to a critical mass supply of "element 94" was not
feasible to them in the projected span of the war.
But let us, for a moment, assume that the Allied commando raid
had not taken place. The German failures with graphite moderated
reactors were already a matter of record, and it was obvious to
them that there were significant technological and engineering
hurdles to be surmounted before a reactor came into production.
On the other hand, the Germans already had the necessary
technology to enrich U 235 for a bomb, and thus uranium enrichment
constituted the best, most direct, and technologically feasible route
to the acquisition of a bomb within the expected span of the war for
the Germans. More on that technology in a moment.
One now has to deal with yet another component of the Allied
Legend. American progress in the plutonium bomb, from the
moment Fermi successfully completed and tested a functioning
reactor in the squash court at the University of Chicago, appeared
to be running fairly smoothly, until fairly late in the war, when it
was discovered that in order to make a bomb from plutonium, the
critical mass would have to be assembled much faster than any
existing Allied fuse technologies could accomplish. Moreover, there
was so little margin of error, since the fuses in an implosion device
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