1. Nuclear heating
Nuclear heating is a central heating method in cities that uses energy produced by nuclear fission as a heat source. It is a new way to solve urban energy supply, reduce transportation pressure and eliminate environmental pollution caused by coal burning. Nuclear energy is the use of energy produced by nuclear reactors to directly supply heat. It can use this energy for pure heating or comprehensive utilization. For example, combined heat and power nuclear energy heating is an important aspect of nuclear energy application. At present, about 70% of primary energy is used for heating, and the advantages of nuclear heating are low environmental pollution and small fuel transportation. Therefore, the market prospect of nuclear heating is very broad.
(1) Heating method
The temperature required for urban central heating is not high, and the existing nuclear energy technology can easily meet the requirements. Currently, there are three nuclear heating methods under development:
①Special low-temperature heating reactor for urban central heating. This kind of reactor has a pressure of 1-2 MPa and can output hot water at about 100°C for urban applications. Due to the low operating parameters and safety of the reactor, it is possible to build in the suburbs of a city, that is, to build only low-pressure steam and hot water without generating electricity. The reactor does not need to use high temperature and high pressure, only 1.5-2.0 MPa, or even lower pressure. In this way, it is easy to manufacture and install pipelines of primary circuit system equipment such as reactors, and the cost is low. In addition, the nuclear heating station, low temperature and low pressure, safe and reliable, can be built near the heat users, reducing the investment in the heat pipe network, and directly supplying heat to the urban area.
②Nuclear thermal power plant. It is similar to the principle of an ordinary thermal power station, except that a nuclear reactor is used instead of a fossil fuel boiler. Nuclear power uses gas extraction for heating while generating electricity, which is similar to conventional thermal power plants. This method is analyzed from the perspective of effective fuel utilization, and it is more economical. However, the general steam parameters of nuclear heating power plants are low, the corresponding steam turbine generators have low efficiency, and the corresponding thermal efficiency of large equipment is lower than that of heating power plants that burn organic fuels. The thermal power plant reactor has high operating parameters and must be built in a location far away from residential areas in accordance with the site selection rules of the power station, thus restricting its development to a certain extent.
③Chemical heat pipe remote nuclear heating system. It is an advanced technology under study. It uses the high-temperature heat source of about 900°C produced by the high-temperature gas-cooled reactor to carry out a reversible reaction and send it to the user through a pipeline at room temperature. The reverse reaction is generated in the regeneration (methanation) device to release chemical heat for the user's application. This method can send nuclear heat to far away for use in large areas.
At present, the main types of low-temperature heating reactors in the world are:
(1) Shell-integrated natural circulation pressurized water reactors, such as the AST-500 designed by the former Soviet Union, have a thermal power of 500 MW and a working pressure of 2.0 MPa.
(2) Pool-type nuclear heating reactors, such as the SLOWPOKE reactor built in Canada, with a heating power of 2000 kilowatts. The reactor is pool-type atmospheric pressure; natural circulation, the cooling water outlet temperature is 80 ℃, and the general-purpose reactor after the coolant is 50 ℃ at the heat exchanger, the heat utilization rate can reach 50%. In addition, ASEA in Sweden has also designed a similar heating station.
The first low-temperature nuclear heating mode reactor designed and built by China adopts a deep-pool type low-temperature heating reactor. The heating power is 5MW, the surface of the pool is atmospheric pressure, the cooling water temperature can reach 114℃, and it can provide about 90℃ heat to the heating network. Water, the nuclear heating station was completed and operated in 1989.
At present, China has designed a shell-type integrated natural circulation nuclear heating reactor. Its thermal power is 200MW, working pressure is 2.5 MPa, and the reactor core and main heat exchanger are arranged in the pressure shell. The system pressure is maintained by the pressure of the nitrogen and water vapor mixture in the upper space of the pressure shell. Because the reactor adopts integrated, self-regulated, full-power natural circulation cooling, control rod dynamic pressure hydraulic drive, double-layer structure and passive safety system and other measures. With excellent inherent safety characteristics, the pile can be built near dense residential areas.
A 200,000 kilowatt low-temperature nuclear heat station can provide heating for a building area of 5 million square meters. It saves 300,000 tons of standard coal every year, reduces the transportation volume of more than 100 million tons-kilometers and reduces the emission of smoke and dust.
(2) Economic benefits
Due to the adoption of multiple sealing and shielding measures, nuclear heating reactors, especially low-temperature heating reactors, emit much less radioactive materials into the environment during operation than coal-fired boilers. From an economic point of view, the initial investment of nuclear heating reactors is higher than that of coal-fired boilers, but the fuel cost is lower. Compared with coal-fired boilers of the same power, the annual transportation of nuclear fuel is only about one hundred thousandth of the amount of coal. , It can output hot water of about 100C ℃ for urban applications. The fuel cost is much lower than that of an oil-burning boiler. Some countries have begun to develop nuclear heating reactors. Among the nuclear power plants in operation, more than ten have been pumped for heating.
Nuclear heating reactor is a nuclear energy system that mainly outputs sensible heat, which can be used for heating and comprehensive utilization of urban residents. As a supplement to nuclear power, its promotion and application will help improve the energy structure, reduce greenhouse gas emissions and improve the urban environment. Nuclear heating reactors have good inherent safety, simple systems, reliable operation, and can be built in densely populated areas close to residents, saving the expensive cost of long-distance transportation of sensible heat. The world's first 5MW nuclear heating test reactor was built and operated in China in 1989. The operating results show that the nuclear heating reactor developed by China has excellent performance.
2. Nuclear power in aerospace and satellites
Both artificial earth satellites and spacecraft need to use long-term, highly reliable power supplies. However, the usual chemical batteries are heavy and have a short service life, and cannot adapt to the operation of satellites and spacecraft. Therefore, most satellites and spacecraft use solar cells and accumulators for power supply. However, solar cells are not applicable if they are too close or far away from the sun. Even in the solar system, it is estimated that the power per unit area of the solar energy received by Neptune is less than 1/900 of that on the earth, which cannot be used. In addition, when the power supply is large, the volume and weight of solar equipment are also very large, which is not suitable for space equipment. With the development of space technology, research on nuclear power sources suitable for satellites and spacecraft began in the 1960s. It is a device and system that converts nuclear energy into electrical energy and supplies it to spacecraft or electric thrust rockets. Space nuclear power devices can be divided into two types: small nuclear batteries that convert radioisotope decay heat into electricity and small nuclear power devices that directly convert fission heat from nuclear reactors into electricity.
3. Nuclear battery
Nuclear batteries use radiation from radioactive isotopes to be absorbed by substances to generate heat, and to obtain electricity through thermo-electric conversion equipment. The radioisotopes used in nuclear batteries mainly include strontium 90 (Sr-90, half-life of 28 years), plutonium-238 (Pu-238, half-life of 89.6 years), polonium-210 (P0-210, half-life of 138.4 days) and other long half-life isotope. Make it into a cylindrical battery. The fuel is placed in the center of the battery and surrounded by thermoelectric elements. The radioisotope emits high-energy alpha rays, which convert heat into electric current in the thermoelectric elements. The battery is small in size and light in weight, and it can be used for power supply on satellites and spacecraft. However, because these radioisotopes do not exist in nature, they are all produced in nuclear power reactors, and the power cannot be very large. The power level of nuclear batteries is generally about 1 kilowatt, and the service life is from several months to several years. Nuclear batteries are currently used on satellites in earth orbit.
4. Space nuclear power plant
With the development of space technology, long-term manned large spacecraft and space stations require power supplies with a power of more than a few kilowatts; large communications satellites also require power supplies with a higher power. And according to the special requirements of space use: power equipment should be light in weight, long in life, small in size, and large in power. For this international space nuclear power research, another kind of miniature nuclear power generation device. A nuclear power device integrating heat source, thermoelectric conversion and heat rejection.
A micro-nuclear power generation device whose reactor adopts a thermal neutron reactor in which high-concentration uranium fuel and zirconium hydride moderator are uniformly mixed. The heat generated by the reactor is carried out by the liquid metal sodium-potassium alloy, and the sodium-potassium coolant carries the heat in The thermoelectric conversion radiator converts it into electrical energy. This method has high conversion efficiency, but due to the long-term adjustment of rotation in space; the problems of gravity-free vapor-liquid two-phase separation, materials, and high temperature resistance are difficult to solve, so it has not yet been practically applied.
In the latest space nuclear reactor technology, the uranium fuel element is made like a diode. The cathode is made of nuclear fuel and metal tungsten sheet, and the metal niobium is made into the anode. After vacuuming, it is filled with cesium vapor to make the electrons easy to fly out from the cathode. . This device is called thermionic emission conversion stack. Fission in the reactor generates heat, which heats tungsten to a high temperature of 1300-2000°C. The tungsten emits a large amount of electrons, which form a current through diodes and external circuits. Using this kind of reactor to generate electricity does not require moving parts, and the entire device can be made small and light. The current power can reach more than 10 kilowatts, and the power can be further improved to 1000 kilowatts. It will be used as the main power source for large-scale communication satellites and interstellar spacecraft.
5. Rocket nuclear propulsion engine
Nuclear power plants that use nuclear energy as the primary energy for spacecraft propulsion can be divided into nuclear thermal rocket engines and nuclear power rocket engines.
The nuclear thermal rocket engine system is a rocket engine system that uses nuclear energy to heat the working medium to generate thrust. Its working principle is similar to that of a chemical rocket engine, except that the heating energy is different. The nuclear thermal rocket engine has a high specific impulse and a long life, but the technology is complex, and it is suitable for long-term spacecraft. Using the nuclear rocket engine system of a nuclear fission reactor, the working medium is generally hydrogen, which is heated by the reactor and adjusted to eject to generate thrust. When the reactor uses solid fuel, the working fluid injection speed can reach 8-12km/s. When liquid and gas nuclear fuels are used, the temperature of the working fluid should be increased so that the injection speed of the working fluid can reach 15-20km/s.
The nuclear power rocket engine system is a propulsion system that first converts the fission or fission energy of a nuclear reactor into electrical energy to power the electric rocket, and then the electric rocket generates thrust. Electric rockets can be electrothermal rocket motors, electrostatic rocket motors (ion rocket motors) and electromagnetic fluid motors. Both Russia and the United States are developing dual-use space nuclear reactor power systems for power generation and propulsion. The propulsion is partly the same as nuclear thermal rocket engine systems, but power generation elements are added. Such a space nuclear reactor power system not only has the function of a nuclear thermal rocket engine system, but also has the function of a space nuclear reactor power supply.
6. Nuclear power desalination
The reactor can also be used to desalinate seawater. The heat generated by the reactor core can be used to heat and distill the seawater to obtain desalinated purified water. The United States has designed a nuclear energy desalination device for use by more and more scientists based in Antarctica. This device can be used to directly fetch water from the bay for desalination, and it can desalinate more than 50 tons of seawater every day, which solves the problem of water use.
Many countries and regions in the world are facing an increasingly serious shortage of fresh water supply. Desalination is an important way to solve the shortage of fresh water. At present, industrial-scale seawater desalination technologies are divided into two categories: one is a process that uses membrane technology to consume electrical energy, that is, reverse osmosis (RO), and the other is a heat-consuming process, that is, the use of heat energy to heat seawater, through evaporation-condensation physics The process produces fresh water.
The desalination reactor device uses the heat energy generated by the nuclear reactor to desalinize seawater and convert it into fresh water. Seawater desalination usually only requires hot water (steam) below 140°C, so low-temperature heating reactors are more appropriate. The reactor coolant circuit adopts a shell-type integrated layout, with full power natural circulation, and transfers heat to the intermediate circuit in the main heat exchanger. The intermediate circuit is a circuit that separates the reactor radioactive water from the desalinated water circuit. The heat in the steam generator is transferred to the water in the water circuit of the desalination plant to evaporate and heat up to 120°C, and then pass to the desalination plant to evaporate the seawater and desalinate the seawater. Two technologies, multi-stage flash cover and multi-effect evaporation, are commonly used in seawater desalination. A 200MW nuclear heating reactor is matched with the multi-effect distillation desalination process, and the daily production of fresh water can reach 160,000 tons.
7. Use nuclear energy to smelt steel
People have mainly used blast furnaces to reduce iron ore through coke to obtain pig iron for many years. A new ironmaking method is currently being studied, called the direct reduction method. This method does not use a large amount of coke, but uses hydrogen at 850°C or a mixture of hydrogen and carbon oxide as a gas as the reducing body. The iron ore is directly reduced into sponge iron in the ironmaking furnace, and then the sponge iron is smelted by an electric furnace. Chenggang. This ultra-high temperature hydrogen and carbon monoxide can be provided by a new type of high-temperature gas-cooled reactor, which uses graphite as a neutron moderator. The high temperature helium gas is used as the coolant, and the outlet temperature can reach 1000°C. It is composed of three parts: the preparation of high-temperature reducing gas, the smelting of direct reduction of Haijin iron and the use of nuclear power and electricity to make steel.
(1) Preparation of high temperature reducing gas
The helium gas of the adjusted circulation is heated to 1000~1200℃ through the high-temperature gas-cooled reactor, and then the non-radioactive helium gas in the secondary loop is heated to about 950℃ through the intermediate heat exchanger, and the hydrocarbon (natural gas) is heated in the reducing gas device. , Heavy oil, etc.) is decomposed into high-temperature hydrogen and carbon monoxide, and then heated to 850°C by a heater, and then transported to the smelting furnace for reduction reaction.
(2) Smelting sponge iron by direct reduction method
In the reduction ironmaking furnace, iron ore is made into powder and added from the upper part of the furnace to form a multi-stage fluidized layer. The reducing gas (H2+CO) at 850°C is fed from the bottom of the furnace, and the iron ore powder is directly reduced into sponge-like pig iron by layered heating and reduction. The heat source of the reducing gas is continuously supplied by the high-temperature gas-cooled reactor, so that the heat energy produced by the reaction will continuously decompose and heat the heavy oil, etc., and send it to the reduction furnace to produce a reaction, and iron ore is smelted into pig iron.
(3) Use the electric energy generated by the reactor to further smelt Haijin Iron into steel
After passing through the heavy oil decomposition device and heating device, the secondary helium gas with a temperature of 900-950° still has a high temperature. In the steam generator, the heat of helium gas is converted into the heat energy of steam, which is sent to the steam turbine generator set to generate electricity. Part of the electricity obtained from the nuclear reactor is used to smelt sponge iron into crude steel, and the other part is used inside and outside the plant.
8. The application of nuclear energy in science and technology
(1) Medical application
The reactor is a very large source of neutrons and a very important research tool for basic science and applied scientific research. In medicine, the neutrons produced by the reactor can be used to treat cancer. This is because many cancer tissues have a good absorption of boron. After the neutron radiation of the reactor, boron will destroy cancer cells and can kill them. .
In 1998, the nuclear medicine method brought a simpler, safer, and cheaper treatment method to humans than surgery. It can detect whether cancer cells have spread to the lymphatic system in the early stages of cancer. Imaging technology is used in nuclear medicine diagnostic methods to detect tumors early and improve the survival rate of cancer patients.
In 1999, in the United States, more than 150 PET scanners were used in clinics, hospitals, and universities, and an increase of 20% each year. PET scanning uses radioactive technology to perform detailed scans of human organs and tissues for diagnosis.
Nuclear battery can be used as a heart wave generator. The characteristic is: the volume is smaller than the AA battery, but it can be used for more than 10 years.
Radiation technology can also be used to sterilize and sterilize medical supplies. It is not as costly as heating disinfection, nor does it pollute the environment and conceal hidden dangers like chemical disinfection. Radiation sterilization can be processed at room temperature and in a package. It is thoroughly disinfected, does not pollute the environment and saves energy and manpower, and Continuous production can be realized. At the end of the 1980s, 80% of medical devices in the world were sterilized by radiation. Irradiation of waste water and sludge such as radiated electron beams can remove the contaminants that pollute the water source. It can produce a series of physical, chemical, and biochemical reactions, destroying the vital nucleases or proteins in viruses, germs and other microorganisms. It will lead to metabolic disorders, hinder reproduction, and finally die, achieving the purpose of disinfection. In 1981, France convened an international conference on the application of radioactive isotopes to the radiation industry, and specifically established the "Radiation Treatment Waste and Its Recycling and Use". Estimated the broad prospects of radiation technology.
(2) Application in daily life
By the 1970s, nuclear energy and nuclear technology had formed new industries in many aspects. In western developed countries, the application of nuclear technology had penetrated into various fields of the national economy, the technology had matured day by day, and new progress had been made.
Wood processing uses radiation to change the material structure to make the wood harder, smoother and fire resistant.
Food preservation and preservation, and the radiation of technetium is also used to benefit mankind, and it is no longer something that causes fatal harm to the human body. Food can be kept fresh through radiation processing technology. After nearly 50 years of worldwide research, it has been shown that food radiation technology is a safe, hygienic, economical and effective new technology for food preservation. Radiation-treated roots and stems can be stored at room temperature for a long time without sprouting. It can kill pests hidden in grains and fruits or parasites in fresh meat, and it can also delay the ripening of fresh fruits and prevent them from decay quickly. , And the food that has been irradiated does not damage the shape, quality, or drug residues, and can also improve the quality of the food. After radiation treatment, it can be sterilized to achieve long-term preservation and anti-corrosion effects. At present, more than 80 kinds of radiated foods and nearly 100 kinds of condiments have been put on the market in the world. In addition, the "Radiation Food Safety Cooperation Agency" has been established internationally. It is conceivable that in the near future, radiated foods will appear like canned foods and frozen foods. On ordinary shelves.
Radiation technology is also very useful in controlling environmental pollution and protecting the ecological balance of nature. The accelerator electron beam can remove toxic components, such as nitrogen and sulfur, in the exhaust gas discharged into the atmosphere after burning coal, petroleum, ores. The United States and Japan have conducted in-depth studies in these areas, and they can remove 80% of toxic substances with this method. In 1984, Japan's Ebara Machinery Manufacturing Company established this type of exhaust gas removal device in Indiana, the United States. It is estimated that by 2000, the market size of exhaust gas treatment devices using this method will reach 6 billion US dollars, mainly in European and American countries.
Nuclear energy and nuclear technology are currently in a period of growth and maturity. The main indicator is that basic nuclear technology and nuclear military technology have matured, formed an industry, and have considerable value. In other areas, there are still a large number of new areas to be developed, but countries around the world have invested a lot of manpower and material resources for development, and economic and social benefits have surged. Moreover, some nuclear researchers and scientists estimate that the current development of nuclear technology applications is only 30%-40% of its maximum technological potential. The strong technological advantages of nuclear energy and nuclear technology determine its strong vitality, which cannot be replaced by other technologies. . It plays an extremely important role in solving some major problems faced by mankind, such as energy, environment, resources, population, and food. It will also have a profound impact on the transformation of traditional industries and the advent of new technological revolutions.
9. Nuclear applications on the moon
As early as the late 1960s and early 1970s, the American Apollo spacecraft brought back 368.194 kilograms of lunar rock and dust six times when it landed on the moon. When scientists heated the lunar dust to 3000 degrees Fahrenheit, they found helium and other substances. After further analysis and identification, there is a large amount of helium-3 on the moon. After conducting a lot of research, scientists believe that it is safer to use helium-3 fusion to generate electricity.
Relevant experts believe that helium-3 is particularly scarce on the earth, but there are many on the moon. Helium-3 alone can develop nuclear power for the earth for 10,000 to 50,000 years. The total amount of helium-3 on the earth is only 10 to 15 tons, which is extremely scarce. However, after analyzing lunar soil samples brought back from the moon, scientists estimated that in hundreds of millions of years, the moon has preserved about 500 million tons of helium-3, which would be sufficient for thousands of years if it were used as an alternative energy source for humans.