In the development process of science and technology, it is normal and not surprising to encounter difficulties, twists and turns.
At the turn of the century, the controversy surrounding France’s “Super Phoenix Fast Reactor” is one example. This is a nuclear power plant named after a bird in Chinese mythology that gains eternal life from its own ashes. It was integrated into the power grid of EDF more than 10 years ago. Although it has not been in normal operation for a long time, as a technological exploration, The experience provided is valuable.
Currently, there are eight fast reactors in Russia, Japan, India, etc., that is, fast breeder reactors, which are operating normally.
Fast reactors, like other reactors, rule out the possibility of atomic explosions in principle. Of course, it should not be denied that there are still some technical problems in fast reactor power generation, but as long as we pay attention to them, the problems can be solved. Fundamentally speaking; fast reactors are not only inherently safe but also very economical. Compared with thermal reactor nuclear power plants, fast reactor nuclear power plants utilize nuclear fuel 60 to 70 times higher. At the same time, fast reactors can also burn long-lived radioactive actinides. Fast reactor nuclear power plants and thermal reactor nuclear power plants can complement each other to provide human beings with safe, economical and clean electric energy. A country with foresight will not neglect the development of fast reactor nuclear power. For example, in 1995, Japan's fast reactor "Monju" with an installed capacity of 280,000 kilowatts successfully conducted power generation and power supply tests. Therefore, the Japanese government. In June 1997, it announced that it would continue to advance its plans to develop fast reactors and nuclear fuel recycling.
By 2050, China's energy gap will reach 1 billion tons of standard coal. People have realized that the large-scale use of carbon-based fuels by humans has become one of the important factors of environmental pollution. Accelerating the development of nuclear power including fast reactor nuclear power plants is one of the important ways to solve the above-mentioned contradictions. China also attaches great importance to the development of fast reactor technology, and relevant authorities have given strong support. In 1987, fast reactor technology research was included in the national "863" high-tech plan, and was listed as the largest project in the energy field of the plan. project, and plans to build a fast neutron experimental reactor with a thermal power of 65 MW and an electrical power of about 20 MW in the near future.
In the past 10 years, the world's fast reactors have been at a low ebb. The main reason is that since the late 1970s, the world's economic development has slowed down, and the growth rate of energy and electricity has also slowed down. The growth rate of thermal reactor nuclear power plants has also slowed down. Development has slowed down accordingly, so the development of the fast reactor industry, which is the successor to thermal reactor nuclear power plants, has also been restricted. However, the development of fast reactors in various countries is also uneven, and each country has adopted different policies based on its different national conditions. Amid the ongoing debate over the ups and downs of the "Super Phoenix Fast Reactor" in Western Europe, it is reasonable for China, as a nuclear power, to still make the decision to start work on fast reactors.
It can be expected that humans will still use fission energy for a long time to come.
The main problems existing in the current utilization of nuclear energy are:
(1) Low resource utilization rate. Industrial applications are thermal neutron reactor nuclear power plants. Although the cost of power generation is lower than coal power, it uses uranium-235 as fuel, and uranium-238, which accounts for 99.3% of natural uranium, cannot be used.
(2) In addition to uranium-235 and plutonium-239 in the burned spent fuel, the remaining highly radioactive waste liquid contains a large amount of "minor actinide nuclides" (MA) and "fission product nuclides" "(PP), some of which have half-lives of more than one million years, becoming potential factors that harm biological cycles, and their final treatment technology has not yet been completely solved.
(3) The reactor is an external source-free support system with a critical coefficient greater than 1, and its safety issues require continuous monitoring and improvement.
(4) The constraints of nuclear non-proliferation requirements, that is, the plutonium-239 generated in nuclear power plant reactors is controlled.
Among these four questions, the first two are more practical.
Fast neutron breeder reactors can convert uranium-238 in natural uranium into plutonium-239 and become fission fuel. After decades of operation with plutonium-239 or uranium-235, the system can be "self-sustaining" by relying on uranium-238, and the uranium resource utilization rate can be increased by 60 to 70 times. Although this is beneficial to the utilization of resources, the other three problems face more severe challenges. Moreover, the initial charging of fast breeder reactors must be based on a large inventory of industrial plutonium extracted from spent fuel of thermal neutron reactors. If the thermal reactor power station has not developed to a considerable installed capacity, it is impossible for fast reactors to have industrial applications. scale, and at this time the inventory of highly radioactive liquid waste is already extremely large.
The current method of disposing of highly radioactive liquid waste is to solidify it, package it and bury it in a stable rock formation. Although this disposal method of "post-processing, solidification and deep burial" is feasible, in the long run it will not solve the problem of leaking into the biosphere.
Therefore, an ideal nuclear system should use natural uranium (or depleted uranium) as the basic charge of the reactor, and allow the radioactive waste it produces to be transduced into short-lived (half-life) in the system. decades) or stable nuclides. The waste output from the system is short-lived low-level radioactive waste. This is the nuclear energy system that fully utilizes uranium resources and is radioactively "clean" that is currently being vigorously researched by the world's nuclear science and technology community. The physical and radiochemical basis of this system are:
(1) Use neutron nuclear reactions to convert non-fissile nuclei into fissionable nuclei and form a stable supply reserve of fissionable nuclei in the system.
(2) Use chemical separation processes to extract MA and PP from highly radioactive waste liquid and return them to the system. Under certain conditions, MA becomes an additional energy supply resource, while PP absorbs neutrons. The transmutation into stable nuclei or short-lived nuclei is the so-called separation-transmutation (P-T) method.
The nuclear science and technology community believes that the most promising radioactive "clean" nuclear energy system will be a medium-energy high-current proton accelerator (1 to 1.5 GeV, tens of milliamperes or higher) and a subcritical device (thermal Neutrons or fast neutrons) are coupled together with an "in-situ" radiochemical separation process (disposed close to the factory to avoid contact with the external environment). It is generally called ADS (accelerator-driven subcritical device) in the literature. It starts the subcritical device with "external" neutrons produced by the spallation reaction of medium-energy protons on heavy nuclei. In the process of converting non-fissionable nuclei into fissionable nuclei, on the one hand it multiplies the neutrons and outputs energy, and on the other hand it multiplies the neutrons and outputs energy. On the other hand, a certain reserve of neutrons is left to transmute the self-generated or imported MA or PP. The criticality coefficient of the subcritical device is about 0.95, and the system is started by "external" neutrons. Therefore, in principle, when the accelerator stops running, the subcritical device "turns off" and there is no criticality accident problem. The input to this system is mainly non-fissionable materials such as natural uranium, and the output is electrical energy and short-lived low-level radioactive waste. The electrical energy consumed by the accelerator represents a small fraction of the electrical energy generated by the system. The MA and PP produced in the subcritical device are transmuted in the system under appropriate conditions after "in-situ" radiochemical separation, so there is no problem of spreading to the biosphere. If properly designed, this system can run for a long time (for example, 5 to 10 years) without changing materials, so the system can have a high load factor.
China has built three world-class particle accelerators: the Beijing Electron Positron Collider, the Lanzhou Heavy Ion Accelerator and the Hefei National Synchrotron Radiation Laboratory. Therefore, it is necessary to have sufficient equipment to build a medium-energy proton accelerator. of technical power.
Of course, there are still some problems in radioactive "clean" nuclear energy systems that need to be further studied.
The following is a brief overview of the fusion reactor issue.
None of the controlled thermonuclear reactors in Russia and other places have succeeded, and some scientists have even suggested that it is impossible for some thermonuclear reactors to achieve the goal of continuously producing fusion energy in the short term. In view of this, the U.S. Congress reduced the appropriation for nuclear fusion research by 33% in 1996. The U.S. nuclear fusion expert group recommended based on the funding situation to close the $1 billion Princeton reactor and invest the limited funds into the planned nuclear reactor. to the International Thermonuclear Experimental Reactor. This nuclear fusion reactor, which is planned to be built by the United States, Russia, Japan and major European countries with joint investment of funds and technology, will be completed in 2050. The nuclear fusion scientific community regards it as a new hope for a breakthrough in the world's nuclear fusion research.
Since the International Thermonuclear Experimental Reactor is still only on paper, the closure of the Princeton reactor indicates that mankind’s 50-year nuclear fusion energy dream will face an “unpredictable future.”
Mikhailov, the famous Russian theoretical physicist and minister of nuclear energy, believes that the success of nuclear energy technology comes from the specificity of its subject and the clarity of its goals, while the issue of nuclear fusion energy technology is "always vague." . He believes that nuclear fusion energy will definitely appear in the future, "but it will only appear in the 22nd century."
However, Mikhailov’s view is completely different from the International Thermonuclear Experimental Reactor plan. According to the decision of the St. Petersburg meeting of the planning committee in the summer of 1996, the location of the experimental reactor will be determined in 1997. The experimental reactor will be completed and started to operate in 2008, and a commercial reactor will be built in a dozen years.
Velikhov, an authoritative Russian nuclear physicist and former vice president of the Russian Academy of Sciences who serves as the chairman of the committee, also predicted again in 1996 that nuclear fusion energy will become a reality in 30 to 40 years.
In any case, this work must be carried out continuously, because it is the hope of solving the future energy problem of mankind.
In China, the Circulator Experimental Technology Laboratory passed the acceptance inspection hosted by China Nuclear Industry Corporation in 1997 at the Southwest Institute of Physics of the Nuclear Industry. As a result, China's first key laboratory for controlled nuclear fusion research was completed.
Since the Southwest Institute of Physics of the Nuclear Industry built China Circulator No. 1 in 1984 and China Circulator No. 1 in 1995, it has carried out a lot of research work and achieved a large number of scientific research results. Its comprehensive capabilities in terms of plasma current, plasma density and temperature, discharge duration and other parameters, as well as plasma diagnostic technology, data acquisition and processing capabilities, and plasma-assisted heating technology are among the best in the world for devices of the same type and scale. .