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The risk of thorium-based nuclear power would be acceptable

SPS/CHIPP Annual Meeting: Maurice Bourquin on the role of thorium in a future energy system

At the end of August, climate change and the future energy supply of Switzerland were among the topics of several keynote speeches at the Annual Meeting of the Swiss Physical Society (SPS) and the Swiss Institute of Particle Physics (CHIPP) in Lausanne. Maurice Bourquin, former professor of physics at University of Geneva, gave a keynote lecture about the ongoing transformation of the Swiss energy system. Professor Bourquin was also Rector of the University of Geneva (1999 - 2003) and President of the CERN Council (2001 - 2003). The 77 year-old scientist’s speech was titled: “Thorium-based systems – A new direction for nuclear waste elimination and energy production.” In the interview that follows, Professor Bourquin explains why he still believes in nuclear power.

The new SPS honorary member Prof. Maurice Bourquin discussing thorium technology on the occasion of the Annual Meeting of the Swiss Physical Society (SPS) and the Swiss Institute of Particle Physics (CHIPP) on August 28th at EPF Lausanne.
Image: SPS, Switzerland

Prof. Bourquin, in Spring 2017 the Swiss population voted not to construct new nuclear power plants in Switzerland in the future. Do you think this was a mistake?

Maurice Bourquin: In May 2017 the majority of people – not all of them – voted for the law proposed by the Swiss parliament to phase-out nuclear power production during the mid-term. I still do not understand how this strategy could be implemented. Since not all of Switzerland’s electricity needs can be supplied by renewable energies, the government obviously wants to import large amounts of electricity from Germany, produced there by coal power plants, which emit a lot of CO2. That is not acceptable to me.

Instead, you favor a new type of nuclear power: that produced through thorium technology. Is it sensible to pursue a revival of nuclear power plants while Swiss laws oppose the construction of new nuclear power plants?

What the Swiss people have decided is not possible to change. But Switzerland is not the only country in the world. If you travel to China or to Africa, you can see that the worldwide need for electricity is tremendous. This additional energy should not be produced by coal, gas or oil for environmental reasons. I see no alternative but to take advantage of nuclear power.

What would be the main advantages of thorium reactors compared to the nuclear energy production technologies currently in use?

The current nuclear power stations use uranium 235 or plutonium as fuel. This is not sustainable. We have to look for an alternative fuel source. And indeed there is one: thorium. Thorium is functional within the reactor for a very long period, for five to ten years, so you do not have to replace it every few months as is necessary with uranium. The reactor is radioactive, but the risk of this radioactivity leaking into the environment is much less. Thanks to the long period the fissile material remains within the reactor, it is protected from being stolen in order to produce nuclear weapons. A second advantage is that thorium does not rely on water as a coolant. Instead, molten lead or molten salt can be used. This enables the reactor to operate at atmospheric pressure instead of at high pressure, as is customary today. There is therefore no risk of a reactor meltdown like at Three Mile Island/US (1979), Tschernobyl/Ukraine (1986) or Fukushima/Japan (2011). A thorium reactor is much safer. A third advantage: there is about 500 times more thorium in the world than uranium 235.

A thorium reactor still produces radioactivity, so people who object to nuclear power because of radioactivity will object to thorium reactors as well.

There is a big difference: The thorium reactor produces much less radioactive waste and this waste has a much shorter time to decay. The waste is dangerous for a period of only three to five hundred years instead of hundreds of thousands of years. Thanks to this much shorter period, the risk of nuclear power would be acceptable to people I think.

The task of storing existing nuclear waste in a safe way falls to society. How can thorium technology help to ease this tremendous task?

In my view, the aim should be not to store this existing high-level waste but to destroy it! Because storing it for hundreds of thousands of years is not adequate. I would prefer if we would destroy this high-level waste by using a thorium reactor. In fact we can use existing nuclear waste as fuel for a thorium reactor and produce electricity at the same time. The technology to do so is essentially ready, it has been tested at CERN (without producing electricity however). The concept works. The next step is to build a proper demonstration plant. In order to do this, Switzerland could participate in one of the on-going projects in China or Russia. I have visited these projects some weeks ago – they are ready to be implemented.

You are a member of the International Thorium Energy Committee, an association of about 30 scientists and citizens based in Switzerland engaged in developing thorium energy systems, with a focus on “Accelerator-Driven Systems.” What is the basic idea of Accelerator-Driven Systems (ADS)?

Thorium is not immediately fissile, it must capture neutrons in order to begin to produce energy within the reactor (by changing thorium 232 to uranium 233). The question is: How do you produce those required neutrons? An innovative way is to use a particle accelerator to do it. Particle physicists know very well that a high-energy proton beam directed on a target produces neutrons. These neutrons can be used to start the fissile reaction in the thorium reactor. If you turn off the accelerator, the reaction immediately stops – and an out of control chain reaction cannot occur.

For an ADS thorium reactor you need an accelerator like those developed at CERN. Does that mean that the CERN area would be a preferred place to establish a thorium reactor?

CERN’s mission is to do fundamental research in particle physics. Using a CERN accelerator to produce energy is not a possibility. But there are centers like the Paul Scherrer Institute in the Canton Aargau that have a proper accelerator, which could be used. Another way would be to construct an accelerator just on the site where the thorium reactor is built.

The idea of a thorium based nuclear power plant has been discussed since the 1950s, or even earlier. Why are we still waiting for this technology to breakthrough?

In the 1960’s and early 1970’s the United States made a large push to develop nuclear power stations. At that time the US had made the decision to use uranium as a fuel for the nuclear reactors and not thorium. The reason was that the government of Richard Nixon was more eager to produce nuclear weapons than to produce electricity. So the US established the entire uranium chain – although it was demonstrated at that time at the Oak Ridge National Lab that a thorium power plant can be operated.

Does that mean that the thorium technology has been ready to produce energy commercially for decades?

That depends on how you choose to construct the thorium reactor: Researchers in Japan or Norway are thinking about using thorium in a water reactor with high pressure. This approach is more advanced, but you abandon the big advantage of working with atmospheric pressure. In my opinion we should not choose water as a coolant, but liquid lead or liquid salt, which allows us to work with atmospheric pressure. There are projects like this in the US and especially in China and Russia.

By when do you expect such a thorium power plant could be developed?

Within about five years one could build a demonstration plant that both produces energy and destroys nuclear waste. I am sure that industry would be interested in this technology because there would be a huge market.

Swiss industry?

The industry in general. Swiss industry currently is not interested in R&D of thorium technology because of a lack of resources.

That means the future of thorium technology will not be decided in Switzerland but rather in countries like China or Russia?

If the Swiss people do not change their minds, I guess yes.

We currently do a lot of energy research in Switzerland in order to set the course for a path to a sustainable energy supply with renewable energies – and to establish a competitive Swiss cleantech industry. Do you think public money should be rather invested in thorium technology research?

A large amount of money, about 13 billion Swiss francs, is reserved to manage nuclear waste. A small part of this money could be redirected to what we are doing, towards studying how to destroy nuclear waste instead of storing it underground. We have the money to do this research without taking it from the research for renewable energies, which is necessary, even though renewables will never be able to supply the electricity deficit after the five nuclear power stations in Switzerland are switched off.

Interview: Benedikt Vogel