At present, the research on nuclear energy in the world mainly focuses on the following aspects:
1.Nuclear fuel extraction technology
There are three main mining methods for onshore uranium mines: open-pit mining, underground mining and in-situ leaching. Open-pit mining is generally used for shallower buried ore bodies, and underground mining is generally used for deeper buried ore bodies. The process of this method is relatively complicated, and in-situ leaching of uranium has the advantages of low production cost and low labor intensity. However, its application has certain limitations, and it is only suitable for deposits with certain geological and hydrogeological conditions. Uranium has been extracted from seawater for a long time. Since the 1960s, Japan, the United Kingdom and the Federal Republic of Germany have successively studied the extraction of uranium from seawater, and gradually established a variety of methods for extracting uranium from seawater. Among them, the research progress of inorganic adsorption methods based on hydrated titanium oxide adsorbents is the fastest. At present, uranium extraction from seawater has shifted from basic research to development and application research. Japan has built a pilot plant with an annual output of 10 kilograms of uranium, and some coastal countries also plan to build 100-ton or even 1,000-ton industrial-scale uranium extraction plants from seawater. Uranium enrichment refers to the separation of uranium isotopes to increase the concentration of uranium-235. At present, uranium enrichment methods include gas diffusion method, separation method, laser method, nozzle method, electromagnetic separation method, chemical separation method, etc., among which gas diffusion method and centrifugal separation method are the enrichment methods commonly used in modern industry. At present, lithium extraction methods mainly include evaporation crystallization, precipitation, solvent extraction, and ion exchange.
2.Advanced nuclear reactor technology
At present, there have been three generations of nuclear reactors. The first generation of light water reactors developed between 1950 and 1960, such as the Shiping Port Pressurized Water Reactor in the United States, the Dresden Boiling Water Reactor and the Magnesium Knox Graphite Gas-cooled Reactor in the United Kingdom The second generation is a large-scale commercial reactor developed and constructed on the basis of the first generation of nuclear power plants from the late 1960 to the early 1990s, such as the LWR reactor, the Canadian Kandu reactor, the Soviet pressurized water reactor VER/RBMK, etc., currently in the world Most nuclear power plants belong to the second generation of nuclear power plants; the third generation refers to advanced light water reactors, that is, nuclear reactors that started operation from late 1990 to 2010. It is a passive, standardized, optimized design and higher safety. Safety systems, such as advanced boiling water reactor ABWR, AP600, European pressurized water reactor EPR, etc.
At present, the international nuclear energy community is striving to develop fast breeder reactors (referred to as fast reactors). When this kind of reactor is in operation, on the one hand, it consumes nuclear fuel and generates heat to generate electricity; on the other hand, it produces new nuclear fuel plutonium, and the output is greater than the consumption, and the unit consumption of natural uranium is reduced to 1/5~1/10 of the original and maintained The economics of nuclear energy; at the same time, it mainly relies on the basic physical and chemical properties and laws inherent in nuclear fuel, coolant, radioactive waste and other components of nuclear technology to eliminate accidents.
The new generation of nuclear reactors currently under study have the following characteristics: sustainable development of nuclear energy, high safety and reliability, greater economic efficiency, and prevention of nuclear proliferation. At present, the internationally recognized new generation concept nuclear reactor systems include gas-cooled fast reactor systems, lead alloy liquid metal-cooled fast reactor systems, molten salt reactor systems, liquid sodium-cooled fast reactor systems, and ultra-high temperature gas-cooled reactor systems.
3.Controllable nuclear fusion technology
Although nuclear fission can produce huge amounts of energy, it is far inferior to nuclear fusion. The nuclear fuel required for fission is limited. Not only does it produce powerful radiation that harms the human body, but nuclear waste is also difficult to deal with. The radiation of nuclear fusion is much less. Nuclear fusion fuel can be said to be inexhaustible and inexhaustible. The product after fusion is water without producing radioactive pollutants. At present, nuclear fusion research mainly focuses on two aspects: one is ignition, where nuclear fusion must be carried out at a high temperature of nearly 100 million degrees; the other is the slow release of nuclear fusion energy. Once nuclear fusion occurs, huge energy is released almost instantaneously. The development of laser technology has made it possible to solve the "ignition" problem of controllable nuclear fusion. At present, the world's largest laser output power reaches 100 trillion watts, which is enough to "ignite" nuclear fusion. In addition to the laser, the "ignition" temperature can also be reached by using the ultra-high microwave heating method. Many countries in the world are actively studying the theory and technology of controlled thermonuclear reactions. The United States, Russia, Japan and Western European countries have made gratifying progress. In November 1991, physicists used the European Union Ring Fusion Reactor to achieve a nuclear fusion reaction for the first time in 1.8 seconds. The temperature was as high as 200 million ℃, which was 10 times the internal temperature of the sun and produced nearly 2 megawatts of electricity. , Thus making mankind’s dream of obtaining sufficient and pollution-free nuclear energy a step closer to reality. At present, the United States, Britain, Russia, Germany, France and Japan are all competing to develop nuclear fusion power plants. Scientists estimate that nuclear fusion power plants may not be put into commercial operation until after 2025. Around 2050, controlled nuclear fusion power generation will benefit mankind extensively.
4.Nuclear waste treatment technology
In the process of nuclear industry production and scientific research, some nuclear wastes with different levels of radioactivity will be produced. Although the content of radioactive materials is very low, the harm is great. At present, the treatment of nuclear waste is usually to separate radioactive materials from the waste, to minimize the volume of waste that contains radioactive materials, and to change its existing state to achieve the purpose of safe disposal. At present, the commonly used treatment methods include multi-stage purification, decontamination, compression and volume reduction, incineration, and solidification.