Thorium ist in der Tat eine interessante Alternative, scheint aber seit Jahrzehnten deswegen nicht weiter verfolgt worden zu sein, weil kein Material entsteht, das sich für Bomben eignet!! Dies, wenn nicht der Kugelhaufen-Reaktor betrachtet wird. Ein Atomreaktor, der praktisch mit einem einzigen elektrischen Schalter abgeschaltet werden könnte, hätte schon was für sich!
Dies scheint aus folgender Notiz hervorzugehen (etwa das 10. Zitat im Google für 'Thorium'):
Furthermore, thorium requires an accelerator-driven system (or ADS) reactor, and these have significant differences from reactors commonly used for uranium. When a uranium-235 atom splits, it releases a wave of high-energy neutrons which can then collide with other U-235 atoms, releasing more neutrons. This is the chain reaction responsible for the explosive power of an atom bomb, and when out of control, it is also the force that can drive a disastrous meltdown in a reactor's core.
But in an ADS reactor, that chain reaction cannot get out of control. "The technology for building such a reactor became ripe some 10 years ago. It uses an external beam of protons to kick-start the reactions," says Lillestol. The thorium does not then continue the reaction on its own - it needs the external beam of protons to keep it running. To stop the reaction, and close down a power station, all that would be needed to be done would be to pull the plug on that external beam of protons.
"In the first step, the protons enter into molten lead where a large number of neutrons are produced," continues Lillestol. "These neutrons enter into the thorium blanket. In fact the proton accelerator has to have a rather intense proton beam, and such accelerators could not be built 10 years ago. This is no longer considered to be a major obstacle."
Lillestol says that the problem is political will - and money. "Nobel laureate Carlo Rubbia began work on the ADS while he was director-general at CERN [the European Organisation for Nuclear Research]. He and his group made so much progress that we all believed that a prototype would be built within a decade. However, when the EU turned down the application for $500m first in 1999 and then in 2000, Rubbia gave up pushing and concentrated on solar energy which he then was also heavily engaged in."
Lillestol - whom Rubbia appointed as deputy division leader of CERN's Physics Division back in 1989 - has continued to fight for the thorium cause. He estimates the cost of a prototype reactor at 550m euros and believes it will take around 15 years to develop: "Molten lead becomes highly corrosive - and the problem is, how do we contain that lead? But the greatest difficulty is getting the world's experts to work together in one place and on one prototype. This, I believe, can only be achieved if all the participating countries have equal rights to all the results." Of course, the supply network for uranium has already been established, and is an important issue for governments all over the world. Switching to thorium would move the goalposts and put new power in the hands of the countries that have the thorium. And on such massive issues, it seems that no one likes change.
India, which has about a quarter of the world's total reserves, has already planned its nuclear power program eventually to use thorium, phasing out uranium. But Greenpeace thinks this is a bad idea. The organisation's senior adviser on nuclear energy, Jean McSorley, says: "Operating thorium reactors would mean taking an enormous risk with untried and untested reactors. We shouldn't forget that we need to reduce energy demand, and fully embrace clean, safe and secure alternatives such as renewable energy systems."
But Dr Norman says that new nuclear technology, of some description, is the future. "If you want evidence that nuclear power is back on the agenda, then take a look at what's happening at universities. Our Masters course on the Physics and Technology of Nuclear Reactors was launched 50 years ago, and this year we've got 36 students - the most we've ever had, almost double the previous highest number which was 19 students back in 1957. Global warming is proving far more deadly than Chernobyl. We could try and keep running with the current reactors, which will run as long as uranium-235 lasts. Or we could try something new." He agrees the something new could well be thorium. Or nuclear fusion, which, he admits, "is technically harder to achieve". Perhaps a thorium reactor is not so far-fetched.
Das alte Lied - Machtspiele überall
Gruss,
Lucky