What is the energy content of nuclear weapons?

[NNadir]

Recently I learned that much of the world's enriched uranium for power plants is provided by Russia, the fuel being mixed down material from dismantled nuclear weapons. This arrangement arose because of a Clinton era treaty in which the United States agreed to buy its fuel from Russia in order to destroy the fissionable material contained in Soviet nuclear weapons. For the Russians, the Americans, humanity as a whole and the environment this was a win-win-win-win. Without the destruction of isolated highly enriched uranium (and for that matter, plutonium), meaningful nuclear disarmament is not really possible. Russia now provides nuclear fuel to every major nuclear nation on earth, except Taiwan, Taiwan being excluded for political reasons.

For nearly a decade much of the uranium fuel worldwide provided to nuclear power plants has come from inventory and not from mines, as there has been a huge surplus of fissionable material.

Recently I read the Nobel Peace Prize lecture of Dr. Mohamed Elbaradei http://nobelprize.org/peace/laureates/2005/elbaradei-lecture-en.html who has been a tireless worker for the advancement of nuclear power and for the prevention of nuclear war. I was struck by this remark he made:

We still have eight or nine countries who possess nuclear weapons. We still have
27,000 warheads in existence. I believe this is 27,000 too many.

A good start would be if the nuclear-weapon states reduced the strategic role given to these weapons. More than 15 years after the end of the Cold War, it is incomprehensible to many that the major nuclear-weapon states operate with their arsenals on hair-trigger alert – such that, in the case of a possible launch of a nuclear attack, their leaders could have only 30 minutes to decide whether to retaliate, risking the devastation of entire nations in a matter of minutes.

These considerations led me to consider the energy content of nuclear weapons. If we assume that the average nuclear weapon contains 20 kg of fissionable material, we see that 27,000 nuclear weapons would contain about 540,000 kg of fissionable material. Since a nuclear weapon typically has an isotopic concentration wherein the fissionable isotopes represent about 95%, one can show that the total energy content is about 41 exajoules. For comparison, the entire energy demand of the United States is about 100 exajoules. Thus the amount of energy in the world's nuclear weapons is enough to fuel all of the energy demand (from all sources) in the entire United States for about 5 months.