Enrichment

In the Haggadah it is written that "in every generation an evil one arises to
destroy us." In this generation it is undoubtedly Ahmedinejad and his Shi'ite
Islamist Iran. Israel has defeated attacks by Egypt, Syria, Lebanon,
Jordan and Iraq, in various combinations in 1948, 1956, 1967, 1973
and 1982. Now it seems to be Iran leading the charge. They have
announced that they have enriched uranium to the level required for energy
generation purposes (3.5%), and that their intentions are purely peaceful.
Hands up all who believe them? Just as I thought, not too many hands.
The problem is that once you have enriched uranium to that extent it is merely
a question of scale to go to the much higher values, say 90%, required for an
atomic bomb! Natural uranium (processed to 'yellow cake') consists of two
main isotopes, U238 (99%) and U235 (1%), each with a different size and
mass. Bequerel in Paris in 1896 discovered that pitchblende, an ore of
uranium, emitted strong rays, that turned out to be due to the spontaneous
decay of U235. This is radioactivity, the process of nuclear fission that
produces two smaller isotopes from one U235 atom. But, while this process
causes some heat, the presence of a majority of nonfissionable U238 prevents
the process from getting out of control. It is only when the U235 is enriched
to a critical level that the decay, that produces several neutrons, causes the
rapid efficient production of energy that results in an explosion.
Although it is only a matter of scale, it is nontrivial to go from the few
hundred centrifuges required to separate the U235 isotope (in the form of
its volatile hexaflouride) for energy production, to the ten thousand or so
centrifuges required for weapons enrichment. Iran is at this stage now.
Some experts think that it is too late to be able to stop Iran by military
means and that only sanctions will work. Others think that sanctions are
useless, since it will give Iran more time to develop the centrifuge process,
and therefore only military means can work, not to destroy all nuclear
capability, but at least to slow the process down. Now may be premature,
maybe its better to wait until the process is more advanced and then strike.
All this is a matter of great risk, because attacks on protected and buried
facilities are not easy, and Iran could recover from such an attack and still
succeed, and as well you have the possibility of military responses. Iran has
announced that 40,000 suicide bombers are being trained to hit the West
and Israel should there be any attack on Iran. While this is probably said
mainly to intimidate, such reactions must be taken seriously.