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After a decade in construction, the China Experimental Fast (neutron) Reactor (CEFR) near Beijing, the worlds most advanced nuclear power project, has reached the first stage in a project that started in the 1990s. By Alan Titchall.
This has been driven by projects using new generation reactors that are very efficient in the use of the world’s uranium resources. Among these reactors are a new generation of fast ‘breeder’ reactors that have been evolving over the past 50 years. Although the first sodium-cooled, fast reactor was built as long ago as 1946 (at Los Alamos National Laboratory in the US), the development of this uranium efficient technology stagnated in the US and the leadership was taken over by France, Japan, the Russian Federation, and now China. Fast reactor technology uses a very small percentage of the natural uranium required by conventional light water reactors. Traditional pressurised water reactors (PWR) use U-235, which constitutes a tiny 0.66 percent of natural uranium after treatment, while spent U-238, which constitutes 99.2 percent of natural uranium, is treated as waste. The reaction cycle of a fast reactor produces extra neutrons that it can use – effectively ‘breeding’ new nuclear fuel as it produces power – improving the utilisation rate of natural uranium to around 70 percent (and with an obvious advantage in the transmutation of nuclear waste). If traditional thermal nuclear reactor technology is not replaced in the near future – there’s fears that the world’s known uranium resources will not be able to supply future demand. The breeding principleWith a traditional thermal nuclear reactor, the neutrons are first slowed down in the reactor core by a moderator, either water or graphite. When the fast neutrons hit atoms, or molecules of the moderator, their speed is reduced. Slow neutrons have a high probability of being absorbed by 235U atoms – which then leads to fission.
Water, the most common coolant in thermal reactors, is not a practical coolant for a fast reactor, because it acts as a neutron moderator. Today’s fast reactors are liquid metal cooled reactors, and all large-scale fast reactors have used molten sodium coolant. The largest fast neutron power reactor in service in the world, and the only one in commercial operation, is Russia’s BN-600 – a sodium-cooled, fast breeder reactor built at Beloyarsk with generating capacity of 600MW. The Chinese projectChina, one of the world’s fastest growing nuclear power generators, is already operating 11 nuclear stations with a total installed capacity of over nine gigawatts and has another 13 nuclear power plants under construction. With a target of 80GW of installed nuclear capacity by 2020 (which will eventually replace China’s coal powered generation by 2050) and limited uranium resources for use in traditional pressurised water nuclear reactors, China has much to gain from the new generation nuclear fast reactor technology.
To reduce the technical and economic risks of this project, the engineering development was divided into three steps – the building of an experimental fast reactor (CEFR); a demonstration fast reactor (CDFR); and a demonstration fast breeder reactor (CDFBR). The CEFR entered the final stage of its installation and trial runs late in 2009 with a thermal power of 65MW, matched with a 20MW turbine generator that was due to pump power into the Chinese grid in June 2010. Work has already started on the next stage of the project, which is the demonstration fast reactor (CDFR), due for commissioning by 2018. The third step, the large demonstration fast breeder reaction with a power of between 1000MW and 1500MW, will be deployed before 2025.
Energy NZ Vol.4 No.5 September-October 2010 |
Nuclear power is enjoying strong growth in Asia and a renaissance in Europe, as a clean and reliable source of power generation.
Fast reactors don’t need a neutron moderator, but rely on fuel that is rich in fissile material and capable of sustaining a chain reaction of nuclear fission, which results in a surplus of neutrons than can be used to produce extra fuel (or to transmute long-half-life waste to less problematic isotopes). Though conventional thermal reactors also produce excess neutrons, fast reactors can produce enough of them to ‘breed’ more fuel than they consume.
The China Experimental Fast Reactor project was approved in 1995. Covering an area of 43.5 thousand square meters, and eventually involving two 850-megawatt, sodium-cooled fast breeder reactors, the project has finally reached the testing stage of its development (with a lot of help from Russia).