PLENTIFUL ENERGY

―To our knowledge, all U.S. nuclear weapons use weapon-grade plutonium, i.e.
plutonium with an isotopic fraction of at least 93.5 percent Pu-239. The same is
probably true of the weapons in the arsenals of the other weapon states.‖
In conclusion, they say,
―In sum, we are not arguing that a proliferator would not prefer weapons-grade
plutonium or highly-enriched uranium to reactor-grade uranium. However, the
possible use of reactor-grade plutonium cannot be discounted.‖
The use of the phrase ―possible use of reactor-grade plutonium cannot be
discounted‖ in a context where weapons-grade plutonium or uranium would be
preferred would seem to weaken the certainty with which opinions on the use of
reactor-grade plutonium have been expressed in the past.
A comment of Luis Alvarez, one of the twentieth century‘s foremost
experimental physicists and an important figure in the development of the bomb, in
his autobiography, provides perspective:
―With modern weapons-grade uranium, the background neutron rate is so low that
terrorists, if they had such material, would have a good chance of setting off a highyield
explosion simply by dropping one half of the material onto the other half. Most
people seem unaware that if separated U-235 is at hand, it‘s a trivial job to set off a
nuclear explosion, whereas if only plutonium is available, making it explode is the
most difficult technical job I know.‖ [16]
The British ―reactor-grade plutonium‖ tests in 1953 very likely had Pu-240
contents only somewhat above weapons grade. Yielding disappointing results, they
were probably the tests referred to by the ex-Director of the United Kingdom
Atomic Weapons Research Institute at Aldermaston, referred to earlier. (―We tried
reactor-grade plutonium a couple of times. We never will again.‖)
Our purpose here isn‘t to go into the extensive and for the most part not
excessively enlightening literature on the possibility of the use of reactor spent fuel
as a weapon, but rather to give the reader a feel for the issues involved. It is
obvious, we think, that reactor-grade plutonium from modern reactor spent fuel
poses considerable difficulties for all but the most capable of nuclear weapons
programs. We also think it obvious that the use of weapons-grade is so much
preferable, and for an aspiring proliferating group or nation, uranium-235 so much
preferable again, that the link to civilian reactors, properly monitored, is weak to
non-existent.
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