Tuesday, 16 October 2012

Thorium Reactors are Coming

If you had to trust your supply of energy and the future of your civilization to someone's hands, which of these would you choose?
Thor Pluto (Hades)

On the left we have Thor, god of electrical power in the form of lightning, tested, protective, and Teutonic; on the right is the god of the depths and the dead. A third choice, not shown, is Uranus, the husband of the earth who, hating the children she bore him, imprisoned them underground.

Moving from myth to chemistry, our players are thorium, plutonium, and uranium. During the cold war, the world's nations threw in their lot with uranium because it could create plutonium for weapons. Thorium could not, so research into thorium as a source of energy finally died in the United States in 1976.

Thorium is not as well known as other metals because we don't, at the moment, use it for much. Nevertheless, it is as common as better-known metals, such as lead, and has interesting qualities as a nuclear fuel. Compare it to uranium:
  1. Since thorium reactions need an outside source of neutrons, thorium reactors are safe. If anything goes wrong, the supply of neutrons either stops by itself or gets switched off, and the reaction simply stops. If reactor number 4 at Chernobyl had been run on thorium, there would have been no disaster in 1986. If the Fukushima reactor had been run on thorium, there would have been no disaster in 2011.
  2. Since thorium cannot be used for atomic weapons, it is good for world peace. Consider the example of Iran's nuclear program, which Iran says is only meant to make electricity, and which Israel and the United States believe is for atomic weapons. We could very well go to war on this issue. However, if Iran built a thorium reactor, that would prove its peaceful purpose. All that Israel and the United States could do is take a step back, take a deep breath, and say, "Good for you."
  3. Since thorium is four times more plentiful than uranium, thorium is cheaper. As well, thorium usually comes from monazite sands, which are being mined, anyway, for rare earth elements. In other words, we might not have to build any new mines or take any more ore from the earth than we are already doing.
  4. It is only slightly radioactive on its own.
  5. The products of the thorium reaction have very short half-lives compared to the products of a uranium reaction.
Thorium reactors can be built according to uniquely tailored designs, such as molten salt reactors, but can also be used as a fuel by one existing and well-tested reactor design, Canada's CANDU reactor. The maker of the CANDU, Atomic Energy of Canada, Ltd. (AECL) has partnered with a Chinese firm to investigate thorium fuel for CANDUs. Since India has very large supplies of monazite, it is also interested in thorium power. It plans to have 30% of its energy come from thorium reactors by 2050.

I first heard about thorium reactors from a TEDx Talk by Kirk Sorensen. A book on the subject is available from Amazon and its own website: Thorium: Energy Cheaper than Coal by Robert Hargraves. The book's title is reason enough to look seriously into thorium reactors.

Later, if you are interested in space travel, look into powering NERVA atomic rocket engines with thorium.

No comments:

Post a Comment