From the article:
After the Manhattan Project, US physicists in the late 1940s were tempted by thorium for use in civil reactors. It has a higher neutron yield per neutron absorbed.
Bombarding thorium with neutrons is how uranium 233 is generated. This was investigated back in the 1980's;
Scientists would like to find a way to use this process to make uranium-233 economically. Thorium is much more abundant than uranium. It would be far cheaper to make nuclear bombs and nuclear power plants with thorium than with uranium.
Unfortunately, no one has figured how to make the process work on a large scale. One nuclear reactor using thorium was built near Platteville, Colorado, in 1979. However, a number of economic and technical problems developed. After only ten years of operation, the plant was shut down. The promise of thorium fission plants has yet to become reality.
Also:
"They were really going after the weapons," said Professor Egil Lillestol, a world authority on the thorium fuel-cycle at CERN. "It is almost impossible make nuclear weapons out of thorium because it is too difficult to handle. It wouldn’t be worth trying." It emits too many high gamma rays.
All of the common isotopes of thorium are alpha or beta emitters. None emit gamma rays.
Everything I have read in addition to the article CLAIM that this is not the type of reactor you would want to build if you were looking for weapons grade material. Certainly building one at any scale for weapons grade material would not make sense seeing as we already know how to produce enough stuff to blow up the world many times over.
More detailed articles did describe the initial problems of not having materials available at that time to handle the required higher temperatures. Technology has now supplied us with those materials.
Investigation of the various links especially http://www.thoriumenergyalliance.com/ will yield an unfortunate political food fight, egos, corporate leverage, and of course the materials vs temperature issue.
Once we started down the LWR path this technology was left in the dust for the most part in the USA but other countries seem to have take great interest as shown in some posts above so it would seem the technology has some merit.
Note: China is on a thorium buying spree.
Thanks again for your contribution to the discussion.