Discussion on:

The Thorium Lord

I like that she dismisses the idea that the choice of Uranium was due to some conspiracy. They way the history is usually presented makes it sound like fiction, as if the people pushing the technology are wackos. It would be a shame if a far superior technology were never put into production simply because the people trying to push it didn't know how to make it sound legitimate.

Her point about desalination potentially being more important than energy production is well taken. The water crisis will likely become a devastating problem long before temperature change begins to be noticed.

There were over 150 of us glued to every word she said at the fourth Thorium Energy Alliance Conference. It was inspiring. She has a way of getting to the point and saying things clearly. That was very much what we needed from both a woman and a person of her status.

AlanLaRue hit the water issue this is not a new application but an important one. Thorium is not process for weapons grade materials and so rejected as having relevance in the arms race past. Now it can be a better alternative to many.

As mentioned, the main reason thorium was neglected as an energy source from 1945-1960 was that uranium was the better "dual use" fuel for making weapons and for civilian energy. Hence uranium is where all the government research dollars went. However, as Alvin Weinberg pointed out in Annual Reviews of Nuclear Science (1972) pp 327-333, there was a major economic+technical obstacle for thorium as well: the basic heavy water and graphite reactor designs up until 1972 did not conserve neutrons sufficiently well to keep a thorium breeder operating, unless the fuel were reprocessed frequently--too frequently to be cost effective. Hence Weinberg invented the liquid-fueled reactor where the dissolved thorium fuel passes through a continuous fuel-reprocessing step. In theory, this could be more cost-effective, and possibly safer
for some of the reasons mentioned above.

Today we have computing power that Weinberg could not have imagined in 1972, and this allows us to model a wide variety of reactor core configurations that could not have been computed in that era. One result is that we can now show--while the liquid fuel thorium reactor has a higher breeding ratio than any practical solid-thorium fueled reactor--it is ALSO possible to operate a heavy water or graphite reactor thorium breeder at substantially higher efficiency than Weinberg was able to calculate. This is an area of active research in India.

While the Molten Salt (dissolved liquid thorium) reactor is a likely future technology for thorium energy and should be developed, there are also nearer-term thorium breeder solutions in the graphite and heavy water moderated (solid thorium fueled) design space that should be of great interest in Asia in the next few years. My colleagues and I will be publishing an example later this year.

I recall reading an argument to the effect that the Uranium fuel source was favoured in the 60's and 70's because it was believed to be impractical to develop a thorium-based ballistic missile submarine. The 'boomer' was an important development as a strategic weapon because of it's stabilizing effect on the arms race. Nuclear deterrence was assured because neither side could win by launching a first strike. There would always be a boomer or two surviving a first strike and this would ensure the destruction of the instigator.

There was an adequate supply of Uranium for bomb-making and I have been told that there are better ways of making weapons-grade Plutonium than harvesting it from power stations. The vast number of weapons maintained during the cold war included large numbers of obsolete weapons that were retained only for their use in arms-reduction talks. This is supported by the very small number of weapons (less than 300) now held in European NATO countries by the United States.

India has already chosen thorium route.There is one pilot reactor . Why there is no mention about it

Indeed India appears to be leading the world in heavy water breeder reactor and solid thorium fuels reprocessing technologies right now. This article however was written from a western point of view and so did not choose to emphasize that knowledge. In the West you will see lots of blog talk about the Molten Salt or LFTR thorium reactor solutions, and not much any more about heavy water and graphite solutions to the same problem. The urban legend is that you cannot do it in graphite or heavy water, you can only make a thorium breeder work with molten salt or liquid sodium. We shall see...

India has a good supply of thorium. But the big advantage in the LFTR (Liquid Fluoride Thorium Reactor) is that the fuel itself is in the liquid state. All fission reactors are subject to the problem that the noble gases xenon and krypton appear in the fission product mix as isotopes which are very active neutron absorbers. All reactors which use solid fuel tend to find the gases trapped in it, whereas the LFTR is able to let the gas bubble out to where it does not interfere with the neutron flux.
There was an actual incident with the conventional reactor at Indian Point, which was shut down for a minor problem in the attendant apparatus (an electrical fault, I think) and the chief engineer quite justifiably delayed having the reactor restarted until he was confident that enough of the xenon had decayed. The company punished him for the delay. His reasoning is, that in order to offset the neutron capture by the xenon, it is necessary to withdraw the control rods further than usual, and then see to it that they go back in at a rate that matches the decay of the xenon, and such synchronising is difficult enough to pose a danger.

I'm inclined to believe that the LFTR will indeed prove superior to the LMFBR, whose best example is the IFR. But most of the thorium-philic websites only compare the LFTR to the appallingly inefficient* light water reactor technologies, and worse still LWRs run under a no-reprocessing mandate. There might be a margin of two to one in the level of waste from Uranium/Plutonium reactors with metal fuel and liquid metal cooling, compared with the LFTR with its liquid fuel and Thorium/Uranium cycle. But both are hundreds of times, or thousands if you treat the LWR spnt fuel as unprocessable waste, than the currently deplyed Uranium technology.
* Appallingly inefficient -- they use between a third and a half of the seven tons of U-235 in a thousand tons of uranium. Yet they supply the USA with twice as much electrical energy as all the hydroelectric plants.