The MSR is an elegant and flexible system, but one, it must be remembered, that can also be used with uranium salts, as it was originally.
The last two of the above attributes are peculiar to thorium. First, the long-lived alpha-particle-emitters that are a problem in the long-term management of waste from uranium, are not produced from thorium. The waste is more radioactive but shorter-lived.
Second, in the thorium cycle, Uranium-233 is bred as the fissile material rather than Plutonium-239 – the favoured isotope for nuclear weapons. (Some would argue that Uranium-233 is still a proliferation risk.)
So where are all the molten-salt reactors?
MSRs are not currently available at an industrial scale, but test reactors with different configurations have operated for extended periods in the past. But there are a number of technical challenges that have been encountered along the way.
One such challenge is that the hot beryllium and lithium “salts” – in which the fuel and heavy wastes are dissolved – are highly reactive and corrosive. Building a large-scale system that can operate reliably for decades is non-trivial. That said, many of the components have been the subject of extensive research programs.
At the “symposium”, the Czech consortium discussed their plan to construct a demonstration system on an existing nuclear reactor site. The system would be built some time after 2014 before proceeding to a small prototype (60 megawatts capacity) that would deliver electricity to the grid.
Whether that prototype system becomes a game-changer depends on many factors, not least of all the cost of deployment.
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More egregious is the claim along the lines of: “all of the thorium can be used but only a fraction of uranium produces energy”. This is based on the erroneous comparison between the low abundance of the fissile isotope Uranium-235 in nature (only 0.7% of uranium is Uranium-235) with Thorium-232 (100% of natural thorium).
The correct comparison should be between Uranium-238, which is 99.3% abundant, and Thorium-232 which is 100% abundant. Both of these are so-called “fertile isotopes” from which one can breed fissionable material to produce energy. Sadly, this claim of “more energy per unit mass” was repeated by Federal Minister for Resources and Energy, Martin Ferguson in his opening address at the symposium, and is widespread in media reports. Pity.
