VIENNA (Reuters) - China has entered an exclusive nuclear technology group by completing a pilot-scale facility to recycle fuel, but a much-larger plant will be needed for commercial operations, a UN nuclear official said on Monday. Gary Dyck, head of the Nuclear Fuel Cycle and Materials Section of the International Atomic Energy Agency (IAEA), was commenting on a report that Chinese scientists had made a breakthrough in spent fuel reprocessing technology. Chinese state television said in early January the achievement could potentially solve a uranium supply problem in the country, which is planning a massive push into nuclear power in an effort to wean itself off coal, the dirtiest fossil fuel. Around 40 percent of nuclear power plants under construction worldwide are in China. It aims to build scores more. The television report said the technology, developed and tested at the No.404 Factory of China National Nuclear Corp (CNNC) in the Gobi desert in remote Gansu province, enables the re-use of irradiated fuel. The technology could boost the usage rate of uranium materials at nuclear plants by sixtyfold, it added. Dyck said the CNNC already in December reported the completion of hot commissioning of a pilot-scale fuel recycling facility, intended for civilian purposes. It puts China into a fairly exclusive group of nuclear technology holders, as few other countries are currently operating at even this scale, he said in an email comment to Reuters. For China to enter into commercial recycling of irradiated nuclear fuel, they will need to construct and commission a much larger facility, Dyck said. Recycling fuel from light-water nuclear reactors to make mixed oxide fuel (MOX), made up of plutonium and uranium, can boost efficiency in the use of uranium resources by 15 percent, he said. The use of recycle technology with fast breeder reactors, a so called 'closed fuel cycle, could improve this efficiency by a factor of sixty or more, Dyck said, adding China last year commissioned its first such reactor. China, as well as France, the United Kingdom and Russia, actively supports reprocessing as a means for the management of highly radioactive spent fuel and as a source of fissile material for future nuclear fuel supply. But independent scientists argue commercial application of nuclear fuel reprocessing has always been hindered by cost, technology, proliferation risk and safety challenges. Nuclear expert Mark Hibbs of the Carnegie Endowment for International Peace said in a blog China should not be overly hasty in aiming to set up a big reprocessing plant along the lines of what weve seen in Japan, France, Russia or the UK. China, which has 171,400 tonnes of proven uranium resources, now has 12 working reactors. It has set an official target of 40 gigawatts (GW) of installed nuclear generating capacity by 2020, but the government has indicated it could double the goal.