Top view of the Molten Salt Reactor
Experiment, Oak Ridge, in the late 1960s.

The emerging global energy crisis is not going to be solved by renewables and rationing. At the same time, the so-called ‘Nuclear Renaissance’, in which thousands of conventional water reactors provide a substantial part of the world’s static energy, is running into trouble from shortages of uranium and skilled technologists, and galloping costs.

Even the US appears to be turning away from conventional nuclear energy. Recently Barack Obama’s energy czar Steven Chu rejected Yucca Mountain as the US geological burial site for Spent Nuclear Fuel (SNF). The State of California has a law that rules out any new nuclear technology that does not solve the SNF issue. However Senators Harry Reid and Orrin Hatch are pushing for greatly increased R&D into the thorium (Th) option.

What is a thorium molten salt reactor?

Instead of fuel rods boiling water, thorium fuels are mixed in a fluid matrix that acts simultaneously as neutron moderator, cooler and control rod. Most importantly, this salt melt is intrinsically stable meaning that strongly negative reactivity coefficients slow down the rate of the chain reactions when the melt temperature rises. Large amounts of water are not needed for cooling. These invaluable properties mean a thorium reactor is much cheaper to build and can be deployed widely. A worst-case accident scenario in an underground thorium molten salt reactor (TMSR) would have very local consequences and risk releasing very small amounts of radiotoxicity.

The big question is: Why is TMSR technology not already standard? After a very successful five year trial at Oak Ridge National Laboratories, Tennessee, in the late 1960s, molten salt reactors were found to be competitive against  fluid metal cooled plutonium breeder reactors.However, the latter also supplied weapons grade fissiles during the Cold War, which was the raison d’etre for US nuclear activities at that time. Molten salt reactors cannot supply weapons-grade plutonium, so the project was terminated. However thorium reactors have another big advantage: they can consume spent fuel from conventional nuclear reactors.  Besides producing energy they can help clean up the global nuclear waste problem. With thorium, the big showstoppers for nuclear power – the weapons and waste risks – are turned on their heads. The International Atomic Energy Agency will applaud any country which launches a crash research program into TMSR.

Australia holds enormous amounts of thorium. In a TMSR, 1 tonne of thorium converts into 10 terawatt hours of electricity. At a production cost of  0.03 cents / kWh, a million tones of thorium will produce $300 billion worth of electrical power. No costly enrichment or isotopic processing is needed to prepare the fluid ThF4 fuel. 

The waste stream from a thorium reactor is correspondingly small: just 1 ton of fission products (FP) per gigawatt/year of energy produced.
 
Fission products from a thorium reactor need to be stored for only about1000 years, not  the million years as is the case for standard nuclear fuel.  Waste from a TMSR is a hundred times less radioactive, less bulky and less costly than today’s nuclear waste. 

The TMSR is superior in performance to the two oft-proposed alternatives, rod thoruium reactors and accelerators. Rod thorium reactor technologies are simply not worth it. Accelerators claim so-called subcriticality but this has been debunked since delayed neutrons are a fact of life anyway, making today’s potentially unstable water reactors controllable. CERN tried to sell the French reactor industry on accelerators for ten years without success. In general however, solid fuel rods simply do not breed sustainably

Molten salt reactors are one of the six main options for the so-called Generation IV nuclear technology. Australia has announced plans to join the GenIV. But leadership of the current GenIV poses risks to the  the prompt development of TMSRs. Established nuclear interests control the agenda and will try to ensure that no disruptive and competing technology makes it. Today France largely dominates the sparse TMSR GenIV activities and they will certainly not permit a revolutionary alternative to interfere with the worldwide marketing of their inflationary uranium water reactors. Neither would the Russians.  

Licensing the TMSR commercially has a few developmental issues to be resolved. Structural alloys must be checked for corrosion. Handling of the fission product waste by way of gas capture, noble metal plateout  and vitrification must be ironed out. Compact carbon composite heat exchangers must be joined with the core parts. But these are all minor technical engineering tasks compared to the daunting high temperatures and astronomically-costly reprocessing schemes of other GenIV options. It is estimated that solving these issues for TMSR would require a 5-year crash program costing about a billion Euros.

While that may sound costly, the investment and operation of a thorium reactor will be a fraction of today’s energy megaprojects. TMSRs can be build in tandem and scaled in configurations ranging from 0.1 – 10 GWe. They adapt instantaneously to the load for the same reason as they are intrinsically safe. Their spare heat can be used thermochemically for industry, in particular for the production of ammonia and hydrogen. 

Finland, traditionally a non-nuclear state, is in the process of pushing the limits for the European Pressurised Reactor (EPR) to 1.6GWe, although this has run into a number of difficulties. A crash research program into the much safer, much cleaner and cheaper thorium molten salt reactor on the same scale could be undertaken if Australia were to team up with other Scandinavian countries like Norway, Sweden and Finland. Indeed, Australia is a very attractive location for a research team of around 50 nuclear engineers to contribute to such an energy solution.

Elling Disen is founder of Thorium ElectroNuclear AB, Sweden. 

More information:

Statements made are supported by independent references found here.