Thorium Alternative for Nuclear Energy

In the US news media, it seems much of the discussion about fuel sources quickly becomes politically entrenched and degenerates into party bickering.  Where is the science?  Are there not alternatives to natural gas fracking, nuclear reactors, or coal powered plants?  Even solar and wind becomes environmentally intrusive, carving up the landscapes. What are the alternatives?

One very interesting option is the radioactive metal thorium -named after the Norse god of thunder. The history of thorium research reads a bit like a dark Nordic murder mystery.  Discovered in 1828 by Swedish chemist Jons Jakob Berzeliusd, research on the use of thorium as a fuel for nuclear energy production was carried at the US Dept. of Energy Oak Ridge Labs, which was created in the 1940s to support the Manhattan Project - the first atomic bomb.  But during the 17 year directorship of Dr. Alvin Weinberg, the lab also focused on peace-time applications of nuclear energy, such as for desalination projects.   In 1965, his researchers built and operated a 8 megawatt  prototype Molten Salt Reactor (MSR), in which thorium can be used.  

But Weinberg’s advocacy of the MSR met opposition with proponents of uranium based breeder reactors during Nixon’s administration.  Uranium yielded plutonium waste that could be used for the arms build-up during the Cold War.  Weinberg’s resulting termination effectively ended research on the MSRs, including a project to build a 6200 megawatt  MSR plant.  The year was 1973 - the year Arab states cut off oil supplies to the West.  It was a great wake-up call for the world to wean itself off fuel dependencies.  But the political focus in the US was on war, not on peacetime energy survival. 

There was a brief return to testing of thorium itself during the Carter Administration, in the 1970’s, when Admiral Rickover and Dr. Alvin Radkowsky successfully replaced the enriched uranium core of a breeder reactor with a thorium based core in the USA's first commercial power plant.  This process requires plutonium to achieve criticality, and the Clinton Administration backed this technology to destroy excess Russian military plutonium in the 1990’s. Again, a war-time concern over the invation of Georgia prompted the Bush administration to stop this effort in 2008.

Why does any of this matter?  One of the most looming issues is  safety.  Watch Kirk Sorensen’s TED Talk for a full explanation, but the danger in the current water-cooled nuclear reactors is the need for very high pressure (over 70 atmospheres of pressure).  When power is lost in a disaster, the super-heated water flashes into steam, expands quickly, and melts the reactor equipment. Hence, the need for the large containment domes.  Instead, the MSR does not have to operate at high pressure.  In the event of a power failure, the liquid salts flow into an overflow cooling tank, and the plant shuts itself down. Zero risk of meltdown.

Thorium is plentiful. In fact, there is a supply of 3200 metric tons stored in Nevada, which  could produce enough energy for the US for 3 years.  There are known supplies in China, India and many other countries.  It is easily mined and processed, with 4,000 times less waste than uranium.  Nearly all of the thorium fuel is consumed (99%), vs. only about .5% of uranium, with 200 times the output.  It also has a higher rate of conversion to electricity (50% vs 30%)making it far more efficient  requiring much less fuel, and producing 1,000 times less nuclear waste, with a far shorter stabilization requirement (10 yrs vs. 10,000).  Nor is the waste from the thorium reactors suitable for weapons.  

Where does this technology stand today?   Well, the Chinese visited ORNL to learn about the Thorium core in a breeding reactor, and are building a test reactor with a scheduled completion of 2017 to 2020. After Fukushima, the Japanese have stepped up efforts on the alternative thorium reactors and might consider the molten salt reactor.  Norway is ready to test burning thorium fuel in a conventional test reactor owned by Norway’s government with help from U.S.-based nuclear giant Westinghouse.  Aker Solutions has developed an accelerator driven reactor using thorium, based on Nobel Prize winner Rubbia's work.   India is actively pursuing thorium replacement cores. And the US?   Apparently the DOE is collaboraing with the Chinese.  But the pursuit of the molten salt reactors is left to the private sector.  Kirk Sorenson, who unearthed the old Oak Ridge Lab work and has become a proponent of thorium, has launched the company Flibe Energy to develop smaller scale molten salt reactors for distributed energy generation. 

To review, there was a successful prototype of MSR built in 1965, which was successful, and pointed to the remaining technical issues to be addressed.  Testing during the last 40 years would have served in good stead.  Unfortunately, this is not testing which can be accelerated, so we are unable to make up for previous decisions with lots of technology dollars. I think this is a very good argument for retaining diversity, set-based design, multiple experiments.  There is no one right way, no “red” way, and no “blue” way. 

We can blame the politics of wars for cutting off the research on Thorium in the past, but what about now?   In 2011, the Weinberg Foundation has been established in London, to honor the pioneering efforts by Dr. Weinberg, and to promote  international cooperation, shared data and testing.   Their website is full of useful resources.   While I have had grave reservations over nuclear, the molten salt reactors with thorium present an entirely different set of variables, and could indeed be significant component of our energy solution.   Let's hope we don't miss this second opportunity.