What Is the Fast Breeder Reactor?

A fast neutron reactor is a nuclear fission reactor without a neutron moderator. In general nuclear fission reactors, in order to improve the efficiency of the chain fission reaction of nuclear fuel, high-speed neutrons (fast neutrons) generated by fission need to be slowed down to slower neutrons (thermal neutrons), and usually lighter nucleus is added The neutron moderator, such as light water, heavy water, etc., uses the hydrogen atoms in it as a neutron moderator for high-speed neutron collision deceleration.

Fast neutron reactors do not use uranium-235, but use plutonium-239 as fuel, but place uranium-238 in the core regeneration zone of plutonium-239. Plutonium-239 released during fission reaction

Effects of the physical characteristics of fast reactors on instrument control systems Fast reactors use heavy nuclear elements (uranium or plutonium) to absorb fast neutron fission and release energy. Their physical design is very different from that of thermal reactors, which makes their instrumentation control systems different from thermal reactors. Instrumentation control system.

1. Compared with thermal reactors, the dynamic parameters of fast reactors have higher core enrichment. The energy spectrum is harder, the Doppler effect is smaller than that of thermal reactors, and the slow reactor neutron share is small and the neutron generation time is short. Fast reactor control is disadvantageous and requires faster transient response characteristics of the fast reactor control system.

2. Toxic effects In fast reactors, thermal neutrons are almost non-existent, so materials with high thermal neutron absorption cross sections, which are critical in the design of thermal reactors, are almost not as important in fast reactors, as "nuclear" Fission products are relatively unimportant. Fast reactors do not have xenon poisoning. Fast reactor cores are small and the average free path of fast neutrons is longer than thermal neutrons. Therefore, fast reactor cores are more tightly coupled than thermal reactors. There is no problem of regional instability. Therefore, it is not necessary to consider the control valve problem of power distribution fluctuation in fast reactors, and it is not necessary to measure the core power distribution like PWR, in this sense, to simplify the instrument control system. The design is helpful.

3. Reactivity control Because fast reactors use sodium as a coolant, it is not possible to control the reactivity by using soluble poisons such as boric acid. Generally, a single control rod is used to control the reactivity, so two independent control rod shutdown systems must be provided To ensure redundancy and security.

4. Instrument efficiency The current nuclear testing instruments are sensitive to thermal neutrons, and the efficiency of detecting fast neutrons is relatively low. Therefore, it is required to reasonably consider the settings and sensitivity of board testing instruments. status quo

Fast neutron reactor abroad

Technically, fast reactors are much more difficult than light water reactors. However, due to its unique advantages, the United States, France, Japan, Germany, Russia and other countries are actively developing and researching fast neutron reactors. As early as 1967, an experimental reactor was built in France. In 1974, a 250,000 kilowatt fast neutron reactor was put into operation. In 1984, a 1.2 million kilowatt large-scale commercial fast reactor nuclear power plant was built. Japan has also designed a fast neutron reactor with an output of 300,000 kilowatts. The core nuclear fuel uses uranium-plutonium mixed oxide, and the periphery of the core is uranium-238. This fast reactor can increase the utilization of uranium resources by 50 times, and the economic and social benefits are very obvious. In addition to the aforementioned five countries, Australia, Norway, Spain, Sweden, Switzerland, Italy and China are also actively carrying out related research work.

Fast neutron reactor domestic

On July 21, 2010, China National Nuclear Corporation announced today in Beijing that China's first fast neutron reactor, the China Experimental Fast Reactor (CEFR), independently developed by China Nuclear Research Institute of China Atomic Energy, reached its first criticality. This is a major independent innovation in the field of nuclear power in China, which means that China's fourth-generation advanced nuclear energy system technology has achieved a major breakthrough. As a result, China has become one of the few countries in the world to master fast reactor technology.

Data Map: Exterior of China Experimental Fast Reactor

China's first fast neutron reactor, the China Experimental Fast Reactor (CEFR), independently developed by China Nuclear Research Institute of China Atomic Energy, reached its first critical point today. Yang Changli, a member of the party group and deputy general manager of the China National Nuclear Corporation, and the leader of the China Experimental Fast Reactor Leading Group, said that this means that China's fourth-generation advanced nuclear energy system technology has achieved a major breakthrough, becoming the 8th country in the world with fast reactor technology. Yang Changli introduced that the fast neutron reactor represents the development direction of the fourth generation nuclear energy system. The closed cycle of nuclear fuel formed by it can increase the utilization rate of natural uranium resources from about 1% to more than 60% of pressurized water reactors. Allow nuclear waste to be fully burned, reduce emissions of pollutants, and minimize radioactive waste. Due to the increase in utilization rate, the relatively poor uranium mines also have mining value, which will increase the world's recoverable uranium resources by a factor of 1,000. The development and promotion of fast reactors are therefore considered to fundamentally solve the problems of sustainable development of the world's energy and green development.

It is understood that China Nuclear Group has initially established a sodium-cooled fast reactor technology research and development system and a standard specification system, and has comprehensively mastered the fast reactor physics, thermal engineering, mechanics, and overall, structure, loop, instrument control, and electrical design technology. A group of independent innovation achievements represented by sodium process has applied for more than 100 patents. It is worth mentioning that the experimental fast reactor has more than 200 systems and more than 7,000 sets of equipment. The localization rate reached more than 70%.

In terms of engineering design, experimental fast reactors have also made breakthroughs in many aspects: the world's first use of passive accidental waste heat removal systems; and independently completed the design of the reactor refueling system.

As a major project of the National 863 Program, China Experimental Fast Reactor is the focus of China Nuclear Group's fourth-generation nuclear energy technology research and development. The reactor uses sodium-cooled fast reactor technology that has multiple reactor operating experience in the United States, France, Russia, and Japan. Thermal power is 65 MW and electrical power is 20 MW.

The construction of experimental fast reactors is the first step in the development of fast reactors in China. Yang Changli also said that in the future, CNNC will accelerate the construction of the fourth-generation nuclear power unit, the China Model Fast Reactor, and promote the development of China's uranium and plutonium mixed fuel manufacturing technology and other supporting technologies. ^[2]

At 10:00 am on July 22, 2011, China's first China Experimental Fast Reactor caused by a fast neutron nuclear fission reaction successfully connected to the grid for power generation. The full realization of the major project goals of the National 863 Program marks a major breakthrough in fast reactor technology that is included in the cutting-edge technology of the national medium- and long-term scientific and technological development plan. An important step forward.

The fast neutron reactor is the main type of the world's fourth-generation advanced nuclear energy system. China Experimental Fast Reactor is the first step in the development of China's fast neutron breeder reactor (FRE). The reactor adopts an advanced pool structure with a nuclear thermal power of 65 MW and an experimental power generation of 20 MW. It is one of the few high-power experimental fast reactors in the world with power generation functions. Its main system settings and parameter selection and Large fast reactor power stations are the same. The experimental fast reactor makes full use of inherent safety and adopts a variety of passive safety technologies, and the safety has reached the requirements of the fourth generation nuclear energy system. According to Xu Yan, chief engineer of the Chinese experimental "fast reactor", "compared to previous generations of nuclear energy systems, the 'fast reactor' has better safety, less waste, and obvious advantages. Although China is more developed than some in developing" fast reactors " The country is one step behind, but we have improved on the basis of learning foreign technology, and have improved management methods and safety. "Xu Yan said that because the" fast reactor "uses an advanced passive accident waste heat removal system, Japan The core melting accident at the Fukushima nuclear power plant will not happen to the "fast reactor".

According to the relevant person in charge of China National Nuclear Corporation, the advanced nuclear fuel cycle system hauled by fast reactors has two major advantages: First, it can greatly improve the utilization of uranium resources, and it can widely use the utilization of natural uranium resources from nuclear power plants. About 1% of the pressurized water reactors increased to more than 60%. Second, long-life radioactive waste generated by pressurized water reactors can be transmuted to minimize radioactive waste. The development and promotion of fast reactor technology is of great significance for promoting the sustainable development of nuclear power and the establishment of an advanced fuel cycle system in China, and for the sustainable development of nuclear energy.

The project is supervised by the Ministry of Science and Technology, the National Defense Science and Industry Bureau, organized by China National Nuclear Corporation, and implemented by the China Atomic Energy Research Institute. Over the years, the Atomic Energy Institute has organized hundreds of related domestic universities, research institutes, and enterprises, and vigorously carried out international cooperation. After continuous innovation, exploration and collaborative research, it has completed research, design, construction, and commissioning. The system began in May 2009. Thermal commissioning. The first nuclear criticality was achieved on July 21, 2010. During the R & D process of experimental fast reactors for more than 20 years, China has comprehensively mastered the technology of fast reactors and obtained a large number of independent innovations and patents. It has achieved independent research, independent design, independent construction, independent operation, and independent research of experimental fast reactors. Management, formed a complete research and development capabilities, and cultivated a group of outstanding technical personnel. As the chief engineer, Xu Zheng led the team to build China's first "fast reactor" from pre-research, conceptual design, preliminary design, construction design, construction, installation and commissioning. During the 11-year construction process, they have completed more than 5,000 design documents, more than 600 commissioning technical documents, more than 600 operating maintenance procedures, more than 1,200 research reports, carried out nearly 53 design verifications, and commissioned tests. More than 1,000. As a brand-new major scientific project, Xu Zheng and his research team always insisted on independent innovation and strengthened international cooperation. They obtained a batch of independent innovation achievements represented by the sodium process, and applied for more than 100 patents. The localization rate of equipment Up to 70%, laying a solid foundation for the development of China's "fast reactor". ^[3]