(Updates with detail, background, quotes) By Francois Murphy PARIS, Nov 21 (Reuters) - Representatives of more than 30 countries signed a deal on Tuesday to build the world's most advanced nuclear fusion reactor, aimed at developing a clean, cheap and abundant energy source as the end of fossil fuels looms. After months of wrangling, France edged out Japan last year to host the 10-billion-euro ($12.8-billion) International Thermonuclear Experimental Reactor (ITER), which will be built at Cadarache, near the southern city of Marseille. At a signing ceremony hosted by French President Jacques Chirac, representatives of the European Union, the United States, Japan, India, Russia, South Korea and China signed the ITER agreement in the presidential Elysee Palace in Paris, finalising the project after years of negotiations. "If nothing changes, humanity will have consumed, in 200 years, most of the fossil fuel resources accumulated over hundreds of millions of years, provoking, at the same time, a veritable climate calamity," Chirac told the meeting. "It (the ITER project) is a victory in the general interest of humanity," he added. The ITER reactor will aim to turn seawater into fuel by mimicking the way the sun produces energy. Its backers say that would be cleaner than existing nuclear reactors, but critics argue it could be at least 50 years before a commercially viable reactor is built, if one is built at all. "We have really already come very far," Janez Potocnik, the EU's Science and Research Commissioner, told reporters. "We have to search for answers not only for the short and medium term, but also for the long term." TECHNOLOGY, THOU SHALT BE CONQUERED Unlike existing fission reactors, which release energy by splitting atoms, ITER would generate energy by combining atoms. Despite decades of research, experimental fusion reactors have so far been unable to release more energy than they use. ITER will aim to fuse deuterium derived from seawater with tritium made from lithium, which is abundant in the Earth's crust. A giant electromagnetic ring will force the atoms together at around 100 million Celsius (180 million Fahrenheit). In the lengthy negotiations over who would host the project, the EU and its member France made huge financial and industrial concessions to the Japanese, agreeing to pay for roughly half the 4.6 billion euro construction cost, at 2000 prices. Japan also secured more staff on the project, including the post of director-general. Chirac, however, highlighted the many benefits the project would bring for France, saying it would create nearly 3,000 jobs in the region. "ITER, a scientific jewel, will have wonderful effects in terms of image, attractiveness, as well as scientific, university and industrial momentum," he said. The countries involved, home to more than half the world's population, hailed it as a model of international cooperation to meet a global challenge. "It is the first time that more than half of the world is standing together shoulder to shoulder and looking a technological challenge in the eye and telling it with confidence: thou shalt be conquered," said Anil Kakodkar, head of India's Department of Atomic Energy. For a factbox on ITER, Reuters 3000 Xtra users can click on: [nL21545844]
