Thorium: the future of nuclear power?
published: 16/02/14, 14:14
Abundant resource with high energy potential, lower quantity and dangerousness of waste: thorium could support the development of a new nuclear industry, but this mineral seen by its supporters as nuclear "green" is not necessarily a miracle solution.
"Thorium is three to four times more abundant in the earth's crust than uranium, especially in countries that are likely to build reactors in the future, such as India, Brazil, and Turkey," Martha Crawford explains. -Heitzmann, director of research, development and innovation of the French nuclear giant Areva.
"If new reactors are built, these countries could ask us for solutions to thorium," she adds.
Areva signed with the Belgian Solvay, in December, an agreement including a research and development program to study the exploitation of this mineral as a potential fuel for nuclear power plants.
Experimental thorium reactors had been built as early as the middle of the 1950 years, but the researches put in parentheses in favor of uranium.
"They were motivated by the fear of a shortage of uranium. Then they slowed down, particularly in France, where the uranium cycle was closed by setting up a spent fuel recycling system, "says Crawford-Heitzmann.
If the research resumes today, it is because the abundance of the resource would benefit some countries, like India which, with about a third of the world's reserves, is clearly engaged in the thorium way in the part of its ambitious civilian nuclear development program.
On the other hand, no upheaval in sight in a nucleusized France. "Many countries have invested billions and billions of euros in industrial infrastructure that depends on uranium. They seek to amortize them and do not want to replace them, "says Crawford-Heitzmann.
The benefits are not decisive enough to take the plunge. "The interest of thorium only makes sense in highly innovative reactors, such as those with molten salts, which are still paper-based," according to CNRS project manager Sylvain David, who is working on such a project in Paris. the Institute of Nuclear Physics at Orsay.
Evolution rather than revolution
Main disadvantage of thorium: it is not naturally fissile, unlike uranium 235 used in the current reactors. It is only after absorption of a neutron that it produces a fissile material, uranium 233, necessary to trigger the chain reaction in the reactor. To start a thorium cycle, you need uranium or plutonium (from plant activity).
"Not to mention that it will take several decades to accumulate enough fissile material to start a cycle," says the Commission for Atomic Energy (CEA).
The risks are not zero either. Certainly, thorium fuels melt at a higher temperature, delaying the risk of melting the reactor core in the event of an accident. "But we can not say that it is the magic cycle where there is no more waste, more risks, more Fukushima", insists Mr. David.
233 uranium is highly irradiating, which would require "much more complicated factories, with shielding to respect the rules of radioprotection", according to the CEA.
As to say that the waste is less radioactive, "it is not correct: the radioactivity is lower at certain periods, and stronger at others. There is not an absolutely decisive advantage in this respect.
Result: the industrial production of energy through thorium is not for tomorrow.
"I do not think we'll have any reactors before 20 or 30. And this will be done gradually, in addition to the closed cycle, "predicts Martha Crawford-Heitzmann. Especially since with the closed uranium-plutonium cycle, "the nuclear resource is ensured for centuries".
With this in mind, the CEA is developing a prototype for a sodium-cooled fast neutron reactor, called "Astrid", which, thanks to uranium 238, makes it possible to use the plutonium several times and even to produce more than it does. consumes by "breeding".
However, uranium 238 represents 99,3% of uranium ore and "large quantities have already been extracted from mines, which we do not know what to do," says David.
http://www.20minutes.fr/planete/1300034 ... aire-futur
"Thorium is three to four times more abundant in the earth's crust than uranium, especially in countries that are likely to build reactors in the future, such as India, Brazil, and Turkey," Martha Crawford explains. -Heitzmann, director of research, development and innovation of the French nuclear giant Areva.
"If new reactors are built, these countries could ask us for solutions to thorium," she adds.
Areva signed with the Belgian Solvay, in December, an agreement including a research and development program to study the exploitation of this mineral as a potential fuel for nuclear power plants.
Experimental thorium reactors had been built as early as the middle of the 1950 years, but the researches put in parentheses in favor of uranium.
"They were motivated by the fear of a shortage of uranium. Then they slowed down, particularly in France, where the uranium cycle was closed by setting up a spent fuel recycling system, "says Crawford-Heitzmann.
If the research resumes today, it is because the abundance of the resource would benefit some countries, like India which, with about a third of the world's reserves, is clearly engaged in the thorium way in the part of its ambitious civilian nuclear development program.
On the other hand, no upheaval in sight in a nucleusized France. "Many countries have invested billions and billions of euros in industrial infrastructure that depends on uranium. They seek to amortize them and do not want to replace them, "says Crawford-Heitzmann.
The benefits are not decisive enough to take the plunge. "The interest of thorium only makes sense in highly innovative reactors, such as those with molten salts, which are still paper-based," according to CNRS project manager Sylvain David, who is working on such a project in Paris. the Institute of Nuclear Physics at Orsay.
Evolution rather than revolution
Main disadvantage of thorium: it is not naturally fissile, unlike uranium 235 used in the current reactors. It is only after absorption of a neutron that it produces a fissile material, uranium 233, necessary to trigger the chain reaction in the reactor. To start a thorium cycle, you need uranium or plutonium (from plant activity).
"Not to mention that it will take several decades to accumulate enough fissile material to start a cycle," says the Commission for Atomic Energy (CEA).
The risks are not zero either. Certainly, thorium fuels melt at a higher temperature, delaying the risk of melting the reactor core in the event of an accident. "But we can not say that it is the magic cycle where there is no more waste, more risks, more Fukushima", insists Mr. David.
233 uranium is highly irradiating, which would require "much more complicated factories, with shielding to respect the rules of radioprotection", according to the CEA.
As to say that the waste is less radioactive, "it is not correct: the radioactivity is lower at certain periods, and stronger at others. There is not an absolutely decisive advantage in this respect.
Result: the industrial production of energy through thorium is not for tomorrow.
"I do not think we'll have any reactors before 20 or 30. And this will be done gradually, in addition to the closed cycle, "predicts Martha Crawford-Heitzmann. Especially since with the closed uranium-plutonium cycle, "the nuclear resource is ensured for centuries".
With this in mind, the CEA is developing a prototype for a sodium-cooled fast neutron reactor, called "Astrid", which, thanks to uranium 238, makes it possible to use the plutonium several times and even to produce more than it does. consumes by "breeding".
However, uranium 238 represents 99,3% of uranium ore and "large quantities have already been extracted from mines, which we do not know what to do," says David.
http://www.20minutes.fr/planete/1300034 ... aire-futur