In depth: Resource availability

Thorium can be found in most rocks and soils. Soil commonly contains about 6 parts per million of thorium, making it 3-4 times more abundant than uranium and it is more easily extracted. Thorium is remarkably evenly distributed across the globe, with highest estimated reserves in India, Brazil, Australia, USA, Egypt and Turkey. It is also found in European countries like Norway, Sweden and Finland. The world reserves of thorium are estimated to be 6.2 million tonnes.

At the present, large amounts of thorium are being excavated in the mining process for rare earths and tin. It is estimated that this leads to a yearly mining level of thorium with an energy equivalent of forty years of world power consumption. This thorium is mostly left unused as mine tailings, and is part of the reason why rare earth mine deposits often show raised levels of radioactivity.

Although not infinitely sustainable, thorium represents an energy supply that could last for tens of thousands of years. This estimate based on at the present rate of energy consumption and IEA growth predictions.

For uranium, the reserves are often estimated to be adequate for centuries of energy supply, rather than millennia, as is the case for thorium, while thorium reserves are only estimated to be 3-4 times greater. How is this possible?

The reason is that the energy content of thorium can be fully employed in a thermal molten salt reactor. While in present day light water reactors, it is only possible to use a small fraction of the energy content of the natural uranium: less than one percent.

If uranium would be used in fast spectrum reactors, it becomes possible to fully use the energy potential of the natural uranium. In a fast spectrum, it is possible to have a closed nuclear fuel cycle, also with the use of uranium. However, it is generally more complicated to achieve acceptable safety levels in fast reactors, whilst remaining economical, especially in case ‘walk away safety’ is required.

The unique feature of thorium MSR’s is their ability to realize a closed nuclear fuel cycle in the thermal spectrum. Given the need to develop novel reactors, there is reason to suppose that the thorium fuel cycle offers better possibilities to be made sustainable (Leblanc, 2009)(Juhasz, et al., 2009, p. 4)(Fetter, 2009)(Hargraves & Moir, 2010, p. 311)(Foro Nuclear, 2011)(National Nuclear Laboratory, 2012, p. 11)(Kloosterman, 2012)(World Nuclear Association, 2016).