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Seductive nuclear power of Thor

Peet Du Plooy

Just 4000 tonnes of thorium could satisfy South Africa's electricity needs for 100 years, writes Peet du Plooy

A mineral being discarded as “waste” may well be able to provide South Africa’s—and the world’s—energy needs for the next thousand years or more. Thorium, aptly named after the Norse god of thunder, Thor, is a nuclear fuel that is four times more abundant in the Earth’s crust than uranium. It was the topic of a conference in Cape Town last week, organised by the South African Institute for Mining and Metallurgy.

In South Africa thorium occurs in rock and heavy mineral sands, with a variety of other “rare earths”, which, despite their name, are relatively abundant in the Earth’s crust.

In the 1950s South Africa was the world’s leading producer of rare earths. Today China has come to totally dominate the global market—it produces 97% of all rare earths, even though it has only 37% of them. In the past three years China has put restrictions on its rare earths exports, which, combined with increased demand driven by the green technology boom, has led prices for the minerals to increase five- or tenfold.

When mining for rare earths, the thorium that is naturally associated with it is regarded as a costly waste that has to be removed and disposed of to get to the valuable stuff.

But thorium has multiple uses. For one, it can substitute for some of the uranium in a conventional light-water nuclear reactor such as Koeberg. When used in this way, thorium can help to extend the time between fuel changes. This means an improvement in the economics, as the plant earns revenue for more of the time. A Norwegian company, aptly named Thor Energy, has just started a programme to test this application of thorium.

Whereas burning uranium produces plutonium, which can be used for making nuclear weapons, using thorium produces instead a man-made uranium variant called U-233, which is also a nuclear fuel, but virtually impossible to use in a nuclear weapon. In fact, thorium can be used to burn up plutonium—a boon for nuclear nonproliferation.
However, it is when it is used in next-generation high-temperature nuclear reactors such as South Africa’s proposed pebble-bed modular reactor or molten salt reactors that thorium really comes into its own.

To generate 1000MW of electricity for one year in a conventional reactor you would need 250kg of natural uranium. From this, 35kg of enriched uranium can be extracted for use as fuel, resulting in 35kg of highly radioactive spent fuel, in addition to the 215kg of less radioactive depleted uranium discarded in the process of enrichment.

For the same amount of energy, using a liquid fluoride reactor, you would need only 1kg of thorium, resulting in 1kg of waste, which contains no uranium or plutonium. Eighty-three percent of this waste becomes stable within 10 years and can then be sold for use in other applications, with only the remaining 17% required to be buried—but then only for 300 years, compared with the thousands of years required for ­uranium fuel waste.

So, thorium-based reactors of current or future design produce less radioactive waste with lower levels of radioactivity than uranium-based reactors and contain none of the waste products that can be used for the making of nuclear weapons. On top of this, when something goes wrong, thorium-based reactors shut themselves down, protecting them from the kind of overheating that resulted in the meltdown at the Fukushima Daiichi plant after the tsunami that hit Japan last year.

The question inevitably arises: If thorium is so great, why are the world’s nuclear powers—most of whom also have rich resources of thorium—not using it as a fuel?

The reality is that more than a dozen reactors (in Germany, the UK, the United States, Canada, the Netherlands and India) operated successfully using thorium as a fuel additive, with a number of reactors still in operation in India today.

Although the exact reasons for largely ignoring thorium as a nuclear fuel is a matter of speculation, it is likely that it is the same positive characteristics of the mineral that counted against its gaining the support of policymakers in the former Cold War adversaries, the US and Russia. It is a sad reality that nuclear energy is the child of nuclear weapons programmes in both these countries. There is no such driver for thorium, as thorium-based reactors ­produce no weapons-grade material.

Looking to the future, it may be possible to use thorium as an additive in conventional reactors within five years. At a push, the first demonstration version of a pebble-bed reactor could be produced within a decade, and commercial versions of other advanced designs such as molten salt reactors may well be available within two or three decades. Although this seems a long way off, these designs have a substantial leg up on fusion reactors in that their viability has already been demonstrated at laboratory scale.

In the meantime, what is required to unlock the potential of two industries—the rare-earths industry today and the thorium industry over the next two decades—is appropriate regulation allowing for the transport and storage of thorium.

We know we have to get away from fossil fuels as the main source of the world’s energy for the sake of both climate and energy security. Although there is undoubtedly massive potential in renewable energy—particularly solar and wind—the effort required to address climate change requires an “all hands on deck” approach, including all low-carbon technologies.

It is, therefore, significant that in the South African government’s integrated resource plan a massively increased focus on renewable energy is accompanied by an equally ambitious nuclear-build plan.

Using next-generation technology, the 4000 tonnes of thorium available at just one South African mine—Steenkampskraal in the Western Cape—is sufficient to provide the country’s electricity needs for a century.

Steenkampskraal Thorium Limited holds a 15% share in Thor Energy, which is pursuing next-generation reactor technology in addition to testing the use of thorium in existing plants. The company has employed Dr Eben Mulder, a leading expert from South Africa’s recently shelved pebble-bed reactor project, with other engineers, to develop a small-scale thorium-based reactor—effectively taking over the reins from the state in driving this technology.

Steenkampskraal is only one of the companies with an interest in this technology. One of the major sponsors of the thorium conference was Exxaro, a coal company that also has interests in thorium-containing mineral sands and is considering supplying thorium—in addition to the solar and wind energy projects it has already announced—as a means for diversifying its offering to a future energy market beyond coal.

It is good news for South Africa that both the minerals and the ­reactor technology required for a safe nuclear revolution are already available in the country.

What remains to be done is to act proactively to ensure that—even without government investment—the regulatory environment can keep up with private-sector interest in pursuing the first real revolution in nuclear energy since its birth six decades ago.

Peet du Plooy is programme manager: sustainable growth at TIPS, but writes in his personal capacity. He does not (yet) hold any shares in thorium companies

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