NP - Uranium Is So Last Century

[David Morris]

http://www.wired.com/magazine/2009/12/ff_new_nukes/

Uranium Is So Last Century — Enter Thorium, the New Green Nuke

Named for the Norse god of thunder, thorium is a lustrous
silvery-white metal. It’s only slightly radioactive; you could carry a
lump of it in your pocket without harm. On the periodic table of
elements, it’s found in the bottom row, along with other dense,
radioactive substances — including uranium and plutonium — known as
actinides.

Actinides are dense because their nuclei contain large numbers of
neutrons and protons. But it’s the strange behavior of those nuclei
that has long made actinides the stuff of wonder. At intervals that
can vary from every millisecond to every hundred thousand years,
actinides spin off particles and decay into more stable elements. And
if you pack together enough of certain actinide atoms, their nuclei
will erupt in a powerful release of energy.

To understand the magic and terror of those two processes working in
concert, think of a game of pool played in 3-D. The nucleus of the
atom is a group of balls, or particles, racked at the center. Shoot
the cue ball — a stray neutron — and the cluster breaks apart, or
fissions. Now imagine the same game played with trillions of racked
nuclei. Balls propelled by the first collision crash into nearby
clusters, which fly apart, their stray neutrons colliding with yet
more clusters. Voilè0: a nuclear chain reaction.

Actinides are the only materials that split apart this way, and if the
collisions are uncontrolled, you unleash hell: a nuclear explosion.
But if you can control the conditions in which these reactions happen
— by both controlling the number of stray neutrons and regulating the
temperature, as is done in the core of a nuclear reactor — you get
useful energy. Racks of these nuclei crash together, creating a hot
glowing pile of radioactive material. If you pump water past the
material, the water turns to steam, which can spin a turbine to make
electricity.