An overview of future fusion nuclear technologies

Edouard — Mon, 16 Nov 2009 14:21:52 +0000

For the fourth and last part of my nuclear series and after reviewing 10 reasons to support nuclear, the past and present of this energy source and a review of the main fission future solutions we are finishing with fusion.

Contrary to future fission solutions, fusion won’t happen before mid-century as it is the exact opposite of current fission reactors. Instead of breaking large atoms, fusion aggregates small atoms to create larger ones.

This is what happens in any star like our sun. As this endeavor is very complex and costly, I believe we shouldn’t think of fusion to solve our current climate and energy problems.

Nonetheless, fusion is most interesting as it could enable Mankind to cover all its energy needs for millenia without any greenhouse gases emissions or pollution.

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There are two main possibilities and here is how they work :

The DT reaction

Fuses deuterium with tritium, making helium. This is the way chosen with both ITER and the National Ignition Facility (NIF). To MacKay :

DT is preferred over DD, because the DT reaction yields more energy and be cause it requires a temperature of “only” 100 million °C to get it going, whereas the DD reaction requires 300 million °C. (The maximum temper ature in the sun is 15 million °C.) Let’s fantasize, and assume that the ITER project is successful.

What sustainable power could fusion then deliver? Power stations using the DT reaction, fuelled by lithium, will run out of juice when the lithium runs out. Before that time, hopefully the second installment of the fantasy will have arrived: fusion reactors using deuterium alone.

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The DD reaction

Fuses deuterium with deuterium. As MacKay notes :

If we imagine that scientists and engineers crack the problem of getting the DD reaction going, we have some very good news. There’s 33 g of deuterium in every ton of water, and the energy that would be released from fusing just one gram of deuterium is a mind-boggling 100 000 kWh.

Bearing in mind that the mass of the oceans is 230 million tons per person, we can deduce that there’s enough deuterium to supply every person in a ten-fold increased world population with a power of 30 000 kWh per day (that’s more than 100 times the average American consumption) for 1 million years (figure 24.17).

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For more

Newsweek tour of the NIF ;
Tomorrow is greener : The Future of Green Energy: Nuclear Fusion ;
Official ITER website ;
Official NIF website.

An overview of future fission nuclear technologies

Edouard — Mon, 09 Nov 2009 16:24:18 +0000

After my articles on the 10 reasons to support nuclear power and the one the past and present of nuclear energy it is time to have a look at the main future technologies.

David JC MacKay on his website mentions two main fission possibilities : fast breeders and thorium and fusion. We will have a look at thesemost promising solutions as well as to other technologies.

The needs for safer, cheaper and cleaner nuclear solutions are important as the IAEA forecasts the demand for nuclear is to increase by 60 percent in the next twenty years.

Fast breeders

Fast breeders are interesting as they burn up Uranium 60 times more efficiently and can thus enable us to use our current nuclear waste to generate low carbon electricity.

Even if research has been carried out since the 1950s in many countries (the United States, the United Kingdom, Japan, Germany, Russia, India and France) no country is currently using it for commercial application.

This soon may change as India and China (and many other countries) are planning to build fast breeder reactors to answer their fast increasing energy needs. India’s is due to be ready next year.

It would also make using Uranium from our oceans a viable option that would answer all our energy needs for millenia.

As MacKay notes :

If fast reactors are 60 times more efficient, the same extraction of ocean uranium could deliver 420 kWh per day per person. At last, a sustainable figure that beats current consumption! – but only with the joint help of two technologies that are respectively scarcely-developed and unfashionable: ocean extraction of uranium, and fast breeder reactors.

For more, please check out the following links :

- World Nuclear page on fast neutron reactors ;
- Scientific American : How do fast breeder reactors differ from regular nuclear power plants?
- Japanese Nuclear Agency page on fast breeders ;
- Wikipedia page on fast breeder reactors.

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Thorium

Here again are extracts of MacKay’s book :

Thorium is a radioactive element similar to uranium. Formerly used to make gas mantles, it is about three times as abundant in the earth’s crust as uranium. Soil commonly contains around 6 parts per million of thorium, and some minerals contain 12% thorium oxide.

(…) Thorium can be completely burned up in simple reactors (in contrast to standard uranium reactors which use only about 1% of natural uranium). Thorium is used in nuclear reactors in India.

(…) An alternative nuclear reactor for thorium, the “energy amplifier” or “accelerator-driven system” proposed by Nobel laureate Carlo Rubbia and his colleagues would, they estimated, convert 6 million tons of thorium to 15 000 TWy of energy, or 60 kWh/d per person over 1000 years. Assuming conversion to electricity at 40% efficiency, this would deliver 24 kWh/d per person for 1000 years.

And the waste from the energy amplifier would be much less radioactive too. They argue that, in due course, many times more thorium would be economically extractable than the current 6 million tons. If their suggestion – 300 times more – is correct, then thorium and the energy amplifier could offer 120 kWh/d per person for 60 000 years.

For more on thorium please check out the following resources :

- World Nuclear page on thorium ;
- Wikipedia page on thorium as a nuclear fuel ;
- www.thorium.tv ;
- Energy from thorium.

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Sustainable development and much more » Future of nuclear