A thorium bomb is not possible because thorium will not fission. Thorium must fisrt be be converted to Uranium in a breeder reactor before it can be used in a reactor. Also the isotope of Uranium that Thorium is converted to is not useful as a bomb material because it does not easily fast fission.
Is this the next generation of terrorist dirty bombs?
First off thorium must pass through a breeder reactor to be converted to Uranium 233. The converted thorium will then need to be processed to be purified and processed in to new fuel.
At some point in that process if the irradiated fuel or the tailings of the reprocessing of the irradiated fuel were stolen they could be made in to a dirty bomb.
However the terrorist that planned such a project would have to be highly knowledgeable, very well equipped, spend many years of preparation and spend millions of dollars to equip a facility capable of building such a dirty bomb without killing everyone involved.
I would think that terrorist would rather spend their time and money on projects less dangerous to themselves and something less time consuming getting a bigger bang for the buck. I also believe that considering the size of such a project that it would be almost impossible to keep it a secret.
The thorium it self would be relatively benign as a dirty bomb as would the converted Uranium 233. Thorium and Uranium are toxic heavy metals but these material after being processed in to fuel are ceramics and not easily absorbed in the body. These materials are also not highly radioactive.
So this is the quite possibly the next generation of nuclear power plants?
Without the waste disposal problem?
That would make all existing nuclear power plants practically obsolete (out of date) in the not too distant future?
That doesn't seem to be the case with the described reactor. Unless the described fuels have been processed in a reactor.
From the article: "The fuel cluster has 54 pins arranged in three concentric rings around a central rod. The 24 pins in the outer ring have thorium-plutonium as fuel, and the 30 pins in the inner and middle rings have thorium-uranium-233 as fuel. The plutonium pins are placed in the outer ring to minimize the plutonium requirement. The thorium provides 60 percent of the reactor's power."
OTOH, I confess to be being baffled by descriptions like, "This is a vertical, pressure-tube-type, heavy-water-moderated, and boiling-light-water-cooled natural circulation reactor."