/kloc-at the end of 0/9, the British physicist Thomson discovered electrons.
1895 german physicist roentgen discovered x-rays.
1896 French physicist becquerel discovered radioactivity.
Madame Curie and Mr Curie discovered a new radioactive element polonium.
1902, Madame Curie discovered the radioactive element radium after four years' efforts.
1905 Einstein proposed the mass-energy conversion formula.
19 14 British physicist Rutherford determined through experiments that the hydrogen nucleus is a positively charged unit called a proton.
1935 British physicist chadwick discovered neutrons.
German scientist otto hahn bombarded uranium nuclei with neutrons and discovered the phenomenon of nuclear fission.
1942 65438+On February 2nd, the University of Chicago successfully started the world's first nuclear reactor.
1945 On August 6 and 9, the United States dropped two atomic bombs on Hiroshima and Nagasaki, Japan.
From 65438 to 0957, the Soviet Union built the world's first nuclear power plant-Obrin Sk Nuclear Power Plant.
Before 1945, human beings only involved physical changes and chemical changes in the field of energy utilization. During World War II, the atomic bomb was born. Humans began to apply nuclear energy to military, energy, industry, aerospace and other fields. The United States, Russia, Britain, France, China, Japan, Israel and other countries have launched research on the application prospect of nuclear energy.
[Edit this paragraph] The process of nuclear power generation
Nuclear energy → internal energy of water and steam → mechanical energy of generator rotor → electric energy.
[Edit this paragraph] Nuclear power generation
A way to generate electricity by using the thermal energy released by nuclear fission in nuclear reactors. It is very similar to thermal power generation. Only nuclear reactors and steam generators are used to replace boilers for thermal power generation, and nuclear fission energy is used to replace chemical energy of fossil fuels. Except for the boiling water reactor (see light water reactor), other types of power reactors are heated by the coolant in the primary loop through the core, and the heat is transferred to the water in the secondary loop or the tertiary loop in the steam generator, and then steam is formed to drive the turbine generator. Boiling water reactor (BWR) is that the coolant in the primary loop is heated by the reactor core, turned into saturated steam at about 70 atmospheres, separated from the steam, and dried to directly drive the turbine generator.
Nuclear power generation uses the heat generated by the nuclear fission chain reaction of uranium fuel to heat water to high temperature and high pressure, and uses the generated steam to drive a steam turbine to drive a generator. The heat released by nuclear reaction is much higher than the energy released by burning fossil fuels (the difference is about one million times), so the amount of fuel required is far less than that of thermal power plants. The purity of uranium -235 used in nuclear power generation is only about 3%-4%, and the rest is uranium -238 that cannot produce nuclear fission.
For example, the fourth nuclear power plant consumes 80 tons of nuclear fuel every year, and only two standard containers can hold it. If it is replaced by coal, it needs 510.5 million tons, and it is enough to transport 705 vehicles with 20 tons of trucks every day. If natural gas is used, it needs 6.5438+0.43 million tons, which is equivalent to burning 200,000 barrels of household gas every day. Converted, it is just close to the gas consumption of 6.92 million households in Taiwan Province Province.
A brief history The history of nuclear power generation is closely related to the development history of power reactors. The development of power reactors was originally for military needs. 1954, the Soviet Union built the world's first nuclear power plant with an installed capacity of 5 MW. Britain, the United States and other countries have also built various types of nuclear power plants. By 1960, 20 nuclear power plants will be built in five countries, with an installed capacity of 1279 MW. Due to the development of nuclear enrichment technology, the cost of nuclear power generation has been lower than that of thermal power generation 1966. Nuclear power generation has really entered the practical stage. 1978, there were more than 200 nuclear power plant reactors with a total installed capacity of 107776 MW in 22 countries and regions around the world. In 1980s, the shortage of fossil energy became increasingly prominent, and nuclear power generation made rapid progress. By 199 1 year, nearly 30 countries and regions around the world have built 423 nuclear power units with a total capacity of 327.5 million kilowatts, accounting for about 16% of the world's total power generation. The first nuclear power plant in the world-Obninsk nuclear power plant in the Soviet Union.
Chinese mainland's nuclear power started late, and construction of nuclear power plants began in 1980s. The 300,000 kW Qinshan Nuclear Power Station designed and built by China was put into operation at the end of 199 1. Daya Bay Nuclear Power Station 1987 started construction, and 1994 was all connected to the grid for power generation.
The principle of nuclear power generation The energy of nuclear power generation comes from the fission energy released by the fission reaction of fissile materials (nuclear fuel) in nuclear reactors. Fission reaction refers to the process that heavy elements such as uranium -235, plutonium -239 and uranium -233 are split into two fragments under the action of neutrons, and neutrons and a lot of energy are released at the same time. In the reaction, the nucleus of fissionable matter absorbs one neutron, then splits and releases two or three neutrons. If these neutrons are removed and consumed, at least one neutron can cause nuclear fission of another atom and make the fission proceed on its own, then this reaction is called a chain reaction of nuclear fission. Realizing chain reaction is the premise of nuclear power generation.
In order to produce nuclear energy with reactors, the following four problems need to be solved: ① To provide the necessary conditions for the nuclear fission chain reaction to be carried out. ② The chain reaction must be controlled by people through certain devices. Uncontrolled fission energy can not only be used to generate electricity, but also lead to disaster. ③ The energy generated by fission reaction should be taken out of the reactor safely. (4) Neutrons and radioactive substances produced by fission reaction are very harmful to human body, and their harm to nuclear power plant staff and nearby residents must be avoided as far as possible.
There are abundant nuclear resources in the world, such as uranium, thorium, deuterium, lithium and boron. The world's uranium reserves are about 4 1.7 million tons. The available nuclear fuel resources on the earth can provide more than100000 times the energy of fossil fuels. The application of nuclear energy has many advantages as an economical and effective measure to alleviate the world energy crisis. First, nuclear fuel has many advantages, such as small size and high energy, and nuclear energy is millions of times larger than chemical energy; 1000g uranium releases energy equivalent to 2400t standard coal; 1 10,000 kw large coal-fired power station needs 3-4 million tons of raw coal every year. It takes 2,760 trains to transport these coals, which is equivalent to 8 trains a day, and 40 million tons of ash are also to be transported. The PWR nuclear power plant with the same power consumes only 28 tons of low enriched uranium fuel with 3% uranium content a year; The cost per pound of uranium is about $20, which is about $0.00 1 kilowatt, which is much cheaper than the current traditional power generation cost. And because the transportation of nuclear fuel is small, nuclear power plants can be built near the most needed industrial areas. The capital investment of nuclear power plants is generally one and a half to two times that of the same thermal power plant, but its nuclear fuel cost is much cheaper than that of coal, and its operation and maintenance cost is also less than that of thermal power plants. If you master the nuclear fusion reaction technology and use seawater as fuel, it is inexhaustible and convenient to use. The second is less pollution. Thermal power plants continuously discharge harmful substances such as sulfur dioxide and nitrogen oxides into the atmosphere, and at the same time, a small amount of radioactive substances such as uranium, titanium and radium in coal will also fall around the thermal power plant with smoke and dust, polluting the environment. Nuclear power plants have set up layers of barriers, which basically do not emit substances that pollute the environment, and even radioactive pollution is much less than that of coal-fired power plants. According to statistics, when the nuclear power plant is in normal operation, the radiation impact on residents in one year is less than the dose received by one X-ray irradiation. The third is strong security. Since the first nuclear power plant was built, more than 400 nuclear power plants have been put into operation all over the world, which have been basically safe and normal for more than 30 years. Although the accident 1979 occurred in the pressurized water reactor nuclear power plant in Three Mile Island, USA, and the accident 1986 occurred in the graphite boiling water reactor nuclear power plant in Chernobyl, the Soviet Union, both accidents were caused by human factors. With the further improvement of PWR, nuclear power plants may become safer.
Advantages:
1. Nuclear power generation will not emit huge amounts of pollutants into the atmosphere like fossil fuel power generation, so nuclear power generation will not cause air pollution.
2. Nuclear power generation will not produce carbon dioxide which will aggravate the global greenhouse effect.
3. Uranium fuel used for nuclear power generation has no other uses than power generation.
4. The energy density of nuclear fuel is several million times higher than that of fossil fuel, so the fuel used in nuclear power plants is small and convenient for transportation and storage. A 1000 MW nuclear power plant only needs 30 metric tons of uranium fuel a year, and it can be transported by plane in one voyage.
5. In the cost of nuclear power generation, the proportion of fuel cost is low, and the cost of nuclear power generation is not easily affected by the international economic situation, so the cost of power generation is more stable than other power generation methods.
Disadvantages:
1. Nuclear power plants will produce high and low levels of radioactive waste or used nuclear fuel. Although it is small, it must be handled carefully because of its radiation, and it needs to face considerable political trouble.
2. The thermal efficiency of nuclear power plants is low, so they emit more waste heat to the environment than ordinary fossil fuel power plants, so the thermal pollution of nuclear power plants is more serious.
3. The investment cost of nuclear power plants is too high, and the financial risks of power companies are high.
4. Nuclear power plants are not suitable for peak and off-peak load operation.
5. The construction of nuclear power plants is more likely to lead to political differences and disputes.
6. There are a lot of radioactive materials in the reactors of nuclear power plants. If they are released into the external environment in an accident, it will do harm to ecology and human beings.
[Edit this paragraph] Nuclear energy provides power for micro devices.
At present, researchers all over the world are developing micro devices smaller than human hair for various purposes, from biochemical sensors to medical implants. But there is an obstacle: at present, no one can come up with an energy source that can match such a small micro-mechanical device.
Anyone who has carried a portable computer that uses five pounds of batteries and weighs only one pound should understand the meaning of this sentence. In order to realize all potential uses of these devices, it is necessary to have such an energy source, which can provide powerful power and is small enough to be installed on the same chip.
Now, a group of engineers at the University of Wisconsin think they may have found the right method. They have started a project to use nuclear energy to provide energy, but these generators will be completely different from dome nuclear power plants that provide electricity for homes and factories.
The energy of these micro-devices is not generated by rotating turbines, but by using trace radioactive substances to generate electricity through their decay. This practice has been done before, but on a much larger scale. People have used this method to power various devices, from pacemakers to spacecraft exploring the dark outer space of the solar system.
James blanchard, a professor of nuclear energy engineering at the University of Wisconsin, said, "This is unprecedented on the scale we are discussing now." The research team led by blanchard is trying to develop this technology, and the research has been funded by the US Department of Energy for 450,000 dollars.
Although the mere mention of nuclear energy will make some people's backs cold, researchers say that their generators only use very little radioactive material, so safety should not be a problem. Blanchard said that the most suitable element for this technology is polonium discovered by the Curie couple in 1898.
Radioactive substances have been widely used in many devices, including smoke detectors. Other copiers also use strip radioactive substances to eliminate static electricity between papers. However, if nuclear power is to become the energy source of future micro-machines, this technology must be reduced to the microscopic level. Blanchard said that there are two ways to generate electricity with radioactive materials. The heat released when radioactive substances decay can make some substances release electrons, thus forming electric energy. But the research team prefers a more direct approach.
Blanchard said: "When the radioactive isotope decays, it will release charged particles, so you can directly capture these charged particles and use them to generate electricity." He said that the voltage generated by these particles is very high relative to the scale of these devices. Blanchard said that his research team did not directly consider the use of these micro devices. He believes that once you have the right energy, others will come up with many uses. In fact, dozens of laboratories around the world have been developing micro-electromechanical devices called MEMS, which is one of the key topics in today's high-tech field.
Blanchard's colleague in this project, amit Lal, a professor of electrical engineering, said that once there is a suitable energy source, "many previously impossible uses" will be generated.
The most direct application of this technology is probably the development of various micro-sensors. Appropriate energy can connect hundreds of micro sensors through wireless communication, which is a potential military use. This sensor is too small to be seen by naked eyes, and can detect the presence of chemicals in harsh environments. Blanchard said: "If they find chemicals they don't like, they can send signals back to a central location so that people can find these chemical weapons without going to the scene." These sensors can also be used to detect trace harmful chemicals and gases in factories. An interesting prospect is that we can make these sensors very small and mix them with lubricating oil used in heavy machinery to detect when the machine needs maintenance.
Lal said: "The biggest impact may be to integrate these sensor systems into the daily system, thus making the daily system more reliable, safe and intelligent."
[Edit this paragraph] Marine nuclear resources
Nuclear energy is the most promising future energy for mankind. At present, there are two ways for people to develop nuclear energy: one is the fission of heavy elements, such as uranium; The second is the fusion of light elements, such as deuterium, tritium and lithium. Heavy element fission technology has been applied in practice. Light element fusion technology is also being actively developed. However, heavy element uranium and light element deuterium and tritium have considerable reserves in the ocean.
Uranium is a kind of high-energy nuclear fuel, and the available energy of 1 kg uranium is equivalent to burning 2250 tons of high-quality coal. However, the reserves of uranium on land are not abundant, and the distribution is extremely uneven. Only a few countries have limited uranium reserves, and only 6,543,800 tons are suitable for mining in the world. Together with low-grade uranium ore and its by-product uranium compounds, the total amount does not exceed 5 million tons, which is only enough for mining for decades according to the current consumption. However, there are abundant uranium resources in the huge seawater. It is estimated that the amount of uranium dissolved in seawater can reach 4.5 billion tons, which is equivalent to thousands of times of the total land reserves. If all uranium in seawater can be extracted, the fission energy contained can meet the energy demand of human beings for tens of thousands of years. However, the concentration of uranium in seawater is very low, and 1000 tons of seawater only contains 3 grams of uranium. Uranium can only be used if it is extracted from seawater first. However, it is technically very difficult to extract uranium from seawater, which requires a lot of seawater for treatment, and the technical process is very complicated. However, many methods have been tried to extract uranium from seawater, such as adsorption, precipitation, bubble separation and algae biological concentration.
Since the 1960s, Japan, Britain and the Federal Republic of Germany have begun to study the extraction of uranium from seawater, and gradually established a variety of methods to extract uranium from seawater. Among them, the inorganic adsorption method based on hydrated titanium oxide adsorbent has the fastest progress. At present, one of the bases for evaluating the feasibility of extracting uranium from seawater is the composite titanium adsorbent made of polymer binder and hydrated oxide drill. 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 kg of uranium, and some coastal countries also plan to build seawater uranium extraction plants with an industrial scale of 100 tons or even 1000 tons.
Deuterium and tritium are isotopes of hydrogen. Under certain conditions, their nuclei can collide with each other to form a heavier nucleus-helium nucleus, and at the same time release huge nuclear energy. When a carbon atom is completely burned to produce carbon dioxide, only 4 electron volts of energy is released, while the deuterium-tritium reaction can release 654.38+07.8 million electron volts of energy. According to calculation, 1 kg hydrogen/fuel can be at least equal to 4 kg uranium fuel or 1 10,000 tons of high-quality coal fuel.
Every liter of seawater contains 0.03 grams of deuterium. 0.03 g deuterium fusion releases energy equivalent to burning 300 liters of gasoline. The total volume of seawater is 65.438+0.37 billion cubic kilometers, and * * * contains hundreds of millions of kilograms of deuterium. The energy released by deuterium fusion is enough to ensure human energy consumption for billions of years. Moreover, the extraction method of deuterium is simple, the cost is low, and the operation of nuclear fusion reactor is very safe. Therefore, the fusion of deuterium and tritium in seawater can solve the future energy demand of mankind and will show the best prospect.
The nuclear fusion reaction of deuterium and tritium needs to be carried out at tens of millions or even hundreds of millions of degrees. Such a reaction has been realized on the hydrogen bomb. There are still many technical difficulties in controllable thermonuclear fusion for production. However, with the progress of science and technology, these problems are gradually being solved.
199 1 year165438+1October 9th, the first deuterium-tritium controlled nuclear fusion experiment was successfully carried out on the European joint ring nuclear fission device, and the fusion energy of 1.8 MW was emitted, lasting for 2 seconds, and the temperature was as high as 300 million degrees, which was higher than that inside the sun. The energy effect of nuclear fusion is 600 times higher than that of nuclear fission and 65.438+0 billion times higher than that of coal. Therefore, scientists believe that the success of deuterium-tritium controlled nuclear fusion experiment is a milestone for human beings to develop new energy sources. In the next century, there will be a major breakthrough in nuclear fusion technology and marine deuterium and tritium extraction technology. The development and maturity of these two technologies will have a great impact on the progress of human society.
In addition, "energy metal" lithium is an important raw material for making hydrogen bombs. Every liter of seawater in the ocean contains 15 ~ 20mg, and the total lithium reserve in seawater is about 2.5× 10 1 1 ton. With the development of controlled nuclear fusion technology, the huge energy released by the fusion of isotope lithium 6 will eventually serve mankind peacefully. Lithium is also an ideal raw material for batteries, and lithium-containing aluminum alloys play an important role in aerospace industry. In addition, the application of lithium in chemical industry, glass, electronics, ceramics and other fields has also developed greatly. Therefore, the worldwide demand for cranes is increasing by 7% ~ 1 1% every year. At present, evaporation crystallization, precipitation, solvent extraction and ion exchange are the main methods to extract lithium from brine.
Heavy water is also a moderator and heat transfer medium for atomic energy reactors, and it is also a raw material for making hydrogen bombs. Seawater contains 2× 10 14 tons of heavy water. If the controllable thermonuclear fusion research that human beings have been committed to is solved, once heavy water is extracted from seawater on a large scale, the ocean can provide inexhaustible energy for human beings.
[Edit this paragraph] Nuclear application of the moon
As early as the late 1960s and early 1970s, when the American Apollo spacecraft landed on the moon, it brought back 368.38+094 kilograms of moon rocks and dust six times. When scientists heated the lunar dust to 3000 degrees Fahrenheit, they found substances such as helium. After further analysis and identification, there are a lot of helium -3 on the moon. After a lot of research, scientists believe that it will be safer to use helium -3 fusion to generate electricity.
Experts believe that helium -3 is very rare on the earth, but it is abundant on the moon. Helium -3 alone can develop nuclear power for the earth 10000-50000 years. The total amount of helium -3 on the earth is only 10- 15 tons, which is extremely scarce. However, after analyzing the lunar soil samples brought back from the moon, scientists estimate that there are about 500 million tons of helium -3 preserved on the moon, which has existed for hundreds of millions of years and can be used for thousands of years if it is used as an alternative energy source for human beings.
[Edit this paragraph] Safe nuclear energy
Today, almost 16% of the world's electricity is produced by 44 1 nuclear reactors, and more than 40% of energy production in nine countries comes from nuclear energy. In this field, the International Atomic Energy Agency, as a subsidiary international organization of the United Nations family, actively supports the peaceful use and development of atomic energy and has formulated corresponding international standards for nuclear safety and environmental protection.
The role of the International Atomic Energy Agency is equivalent to an intergovernmental central forum for scientific and technological cooperation in the nuclear field. As a coordination center, the establishment of the agency is conducive to the information exchange in the field of nuclear safety, the formulation of standards and norms, and the provision of methods to strengthen the safety of nuclear reactors and avoid the risk of nuclear accidents at the request of relevant governments. The IAEA also plays an important role in international efforts aimed at ensuring the application of nuclear technology to sustainable development.
With the increase of nuclear energy programs in various countries, the public is paying more and more attention to nuclear safety issues, and the responsibility of the International Atomic Energy Agency in the field of nuclear safety has also expanded. To this end, the International Atomic Energy Agency (IAEA) has formulated the benchmark standards for radiation protection, and issued relevant regulations and codes of conduct for specific business types, including the safe transportation of radioactive materials. In accordance with the Convention on Emergency Assistance in the Case of a Nuclear Accident or Radiation and the Convention on Early Notification of a Nuclear Accident, IAEA will take immediate action to ensure emergency assistance to member States in the event of a radiological accident.
The IAEA is also responsible for maintaining several other international treaties on nuclear safety. These international treaties include the Convention on the Physical Protection of Nuclear Material, the Vienna Convention on Civil Liability for Nuclear Damage, the Convention on Nuclear Safety and the Joint Convention on the Safety of Spent Fuel Management and the Safety of Radioactive Waste Management. The last convention is the first international legal instrument on nuclear safety.
The International Atomic Energy Agency (IAEA) provides assistance and consultation to member countries in implementing atomic energy plans, and actively promotes the exchange of scientific and technological information among countries. The agency also helps governments to use atomic energy peacefully in the fields of water, sanitation, nutrition, medicine and food production. An outstanding example of this is mutation breeding by using nuclear radiation technology. Through this work, nearly 2000 excellent new crop varieties have been successfully cultivated.
At present, there is endless debate about the choice of energy. The cause of this debate is that the international community is trying to control the emission of carbon dioxide into the atmosphere, because carbon dioxide enters the atmosphere and causes global warming. The International Atomic Energy Agency emphasizes the benefits of nuclear energy, and believes that nuclear energy, as an important energy source, does not have the problems of greenhouse gases and other toxic gases.
The International Atomic Energy Agency collects and disseminates almost all information about nuclear science and technology through its international nuclear information system in Vienna. In cooperation with UNESCO, the International Atomic Energy Agency has also established an international theoretical physics center in Trieste, a city in the northeast of Italy. The center has three realities. Today, almost 16% of the world's electricity is produced by 44 1 nuclear reactors, and more than 40% of energy production in nine countries comes from nuclear energy. In this field, the International Atomic Energy Agency, as a subsidiary international organization of the United Nations family, actively supports the peaceful use and development of atomic energy and has formulated corresponding international standards for nuclear safety and environmental protection.
The role of the International Atomic Energy Agency is equivalent to an intergovernmental central forum for scientific and technological cooperation in the nuclear field. As a coordination center, the establishment of the agency is conducive to the information exchange in the field of nuclear safety, the formulation of standards and norms, and the provision of methods to strengthen the safety of nuclear reactors and avoid the risk of nuclear accidents at the request of relevant governments. The IAEA also plays an important role in international efforts aimed at ensuring the application of nuclear technology to sustainable development.
With the increase of nuclear energy programs in various countries, the public is paying more and more attention to nuclear safety issues, and the responsibility of the International Atomic Energy Agency in the field of nuclear safety has also expanded. To this end, the International Atomic Energy Agency (IAEA) has formulated the benchmark standards for radiation protection, and issued relevant regulations and codes of conduct for specific business types, including the safe transportation of radioactive materials. In accordance with the Convention on Emergency Assistance in the Case of a Nuclear Accident or Radiation and the Convention on Early Notification of a Nuclear Accident, IAEA will take immediate action to ensure emergency assistance to member States in the event of a radiological accident.
The IAEA is also responsible for maintaining several other international treaties on nuclear safety. These international treaties include the Convention on the Physical Protection of Nuclear Material, the Vienna Convention on Civil Liability for Nuclear Damage, the Convention on Nuclear Safety and the Joint Convention on the Safety of Spent Fuel Management and the Safety of Radioactive Waste Management. The last convention is the first international legal instrument on nuclear safety.
The International Atomic Energy Agency (IAEA) provides assistance and consultation to member countries in implementing atomic energy plans, and actively promotes the exchange of scientific and technological information among countries. The agency also helps governments to use atomic energy peacefully in the fields of water, sanitation, nutrition, medicine and food production. An outstanding example of this is mutation breeding by using nuclear radiation technology. Through this work, nearly 2000 excellent new crop varieties have been successfully cultivated.
At present, there is endless debate about the choice of energy. The cause of this debate is that the international community is trying to control the emission of carbon dioxide into the atmosphere, because carbon dioxide enters the atmosphere and causes global warming. The International Atomic Energy Agency emphasizes the benefits of nuclear energy, and believes that nuclear energy, as an important energy source, does not have the problems of greenhouse gases and other toxic gases.
The International Atomic Energy Agency collects and disseminates almost all information about nuclear science and technology through its international nuclear information system in Vienna. In cooperation with UNESCO, the International Atomic Energy Agency has also established an international theoretical physics center in Trieste, a city in the northeast of Italy. The center has three laboratories to conduct research on the basic application of atomic energy. The International Atomic Energy Agency also cooperates with the Food and Agriculture Organization of the United Nations to study the application of atomic energy in food and agricultural production. The agency also cooperates with the World Health Organization to carry out research on the application of nuclear radiation in medicine and biology. In addition, the International Atomic Energy Agency has a marine environment laboratory in Monaco. The laboratory is assisted by the United Nations Environment Programme and the United Nations Educational, Scientific and Cultural Organization, and conducts research on global marine environmental pollution.
Laboratory, to carry out basic application research of atomic energy. The International Atomic Energy Agency also cooperates with the Food and Agriculture Organization of the United Nations to study the application of atomic energy in food and agricultural production. The agency also cooperates with the World Health Organization to carry out research on the application of nuclear radiation in medicine and biology. In addition, the International Atomic Energy Agency has a marine environment laboratory in Monaco. The laboratory is assisted by the United Nations Environment Programme and the United Nations Educational, Scientific and Cultural Organization, and conducts research on global marine environmental pollution.
[Edit this paragraph] Knowledge of nuclear energy
1. Atoms and nuclei
Everything in the world consists of a positively charged nucleus and negatively charged electrons revolving around the nucleus. Nuclei include protons and neutrons. The number of protons determines which element the atom belongs to, and the mass of the atom is equal to the sum of the number of protons and the number of neutrons. For example, the uranium -235 atom consists of a nucleus (composed of 92 protons and 143 neutrons) and 92 electrons. If the atom is regarded as the earth where we live, then the nucleus is equivalent to the size of a ping-pong ball. Although the nucleus is small, it can release amazing energy under certain conditions.
2. Isotopes
Some atoms with the same number of protons but different numbers of neutrons or the same atomic number but different atomic mass numbers are called isotopes, which occupy the same position in the periodic table of chemical elements. Simply put, isotopes refer to various atoms of an element, which have the same chemical properties. According to different masses, it can usually be divided into heavy isotopes and light isotopes.
3. Isotopes of uranium
Uranium is the element with the largest atomic number in nature. The isotopes of natural uranium are mainly uranium -238 and uranium -235, accounting for 99.3% and 0.7% respectively. In addition, there are trace amounts of uranium -234 in nature. The energy released by the complete fission of uranium -235 nucleus is 2700000 times that released by the complete combustion of the same amount of coal.
4. Nuclear energy and its acquisition
Nuclear energy is short for nuclear fission energy. More than 50 years ago, scientists found in an experiment that the nucleus of uranium -235 can split after absorbing a neutron, and at the same time release 2-3 neutrons, which is huge in energy, far greater than the energy released by chemical reaction. This is what we call nuclear energy today. There are two main ways to acquire nuclear energy, namely heavy nuclear fission and light nuclear fusion. Nuclear fusion releases more energy than nuclear fission. For example, equal amounts of deuterium and uranium -235 are fused and split respectively, and the energy released by the former is about three times that of the latter. The familiar atomic bomb, nuclear power plant, nuclear reactor and so on all use the principle of nuclear fission. Only the requirement for nuclear fusion is higher, that is, the hydrogen nucleus needs to be at a high temperature above 6000 degrees, so that a considerable nucleus can have the kinetic energy to realize polymerization.
5. heavy nuclear fission
Heavy nuclear fission refers to that a heavy nucleus splits into two or more nuclei with medium atomic weight, causing a chain reaction, thus releasing huge energy. For example, when a neutron bombards the nucleus of U-235, it will split into two smaller nuclei, producing 2-3 neutrons and β, γ rays at the same time, releasing about 200 mev of energy. If another newly generated neutron bombards another uranium -235 nucleus, it will cause new fission, and so on, the fission reaction will continue, thus forming a fission chain reaction and releasing nuclear energy continuously.
6. Light nuclear fusion
The so-called light nuclear fusion refers to the process of combining two nuclei with small mass into a new nucleus with large mass at high temperature (above several million degrees) and releasing a lot of energy, which is also called thermonuclear reaction. It is one of the important ways to obtain nuclear energy. Due to the strong electrostatic repulsion between nuclei, it is difficult to have a fusion reaction at normal temperature and pressure. In the sun and other stars, the pressure and temperature are extremely high, so the light nucleus has enough kinetic energy to overcome the electrostatic repulsion and continue to fuse. Self-sustaining nuclear fusion reaction must be carried out at extremely high pressure and temperature, so it is called "thermonuclear fusion reaction".
The hydrogen bomb is made by using the principle that the fusion reaction of deuterium and tritium nuclei releases huge energy instantly, but its energy release is uncontrollable, so it sometimes causes great damage. The "controllable thermonuclear fusion reaction device" being developed at present also applies the principle of light nuclear fusion. Because this thermonuclear reaction is artificially controlled, it can be used as energy.