What is Controlled Nuclear Reaction

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91 The radioactive behavior of matter 3. How do nuclear power plants work? The chain reaction takes place in a regulated manner in the reactors of nuclear power plants. The fuel rods contain uranium pellets that contain around 3% uranium-235. However, the fuel rods do not burn, but get very hot during nuclear fission. For example, you immerse yourself in water that is heated in this way. The generated steam drives the turbine of a generator (Fig. 91.1). The water also serves as a moderator. This is the name of materials that can slow down neutrons. This is necessary for the split to take place. In order to control the chain reaction, control rods made of cadmium or boron compounds are required (Fig. 91.2). These can capture neutrons. The conspicuous cooling towers of a nuclear power plant only emit the thermal energy of the cooling water to the environment. The controlled chain reaction (Fig. 91.3) E1 Place the dominoes in a line. If you hit the first stone, the others will gradually fall over. In the controlled chain reaction, the number of splits remains the same. Advantages of a nuclear power plant: • The generation of electricity by nuclear fission is about 2 million times more efficient than the generation of electricity in thermal power plants. • There are no combustion gases from fossil fuels. Of course, this does not apply to the production of nuclear fuel! Disadvantages of a nuclear power plant: • Incorrect operation, malfunctions and natural disasters can lead to serious disasters. Large stretches of land will be contaminated by radioactive substances for many years ( pages 92–93). • The fission products resulting from the fission must be safely stored for millennia, for example in abandoned mines. • The transport of fissile material and radioactive waste entails risks, for example in the event of accidents. • Weapons-grade material can be obtained from fuel production. 4. What does nuclear fusion mean? The sun gives off enormous amounts of energy through the fusion of hydrogen nuclei to form helium nuclei (Fig. 91.4). This requires temperatures of a few million ° C and very high pressures. Until now, nuclear fusion has only been used in hydrogen bombs, not in power plants. Steam turbine Generator Reactor pressure vessel Fuel rods Primary circuit Secondary circuit Cooling water Condenser Heat exchanger Water Heavy concrete jacket Safety container Control rods 91.1 Principle of a pressurized water reactor in a nuclear power plant Neutron fuel rods U-235 (2-3%) U-238 Water (moderator) Control rods 91.2 Control of the chain reaction in a nuclear reactor V2 91.3 The controlled chain reaction - By capturing neutrons, the chain reaction in the reactor of the nuclear power plant runs linearly. In a nuclear power plant, a nuclear reactor generates thermal energy through fission. The chain reaction is regulated by trapping neutrons. The result is water vapor that operates the turbine of a generator. M Tritium Deuterium Fusion Neutron Proton Helium Neutron H + + + H He n Energy 2 1 3 1 4 2 1 0 91.4 Principle of nuclear fusion 91.5 The sun is a large fusion reactor. 91.6 View into a research reactor Worksheets qa35qg For testing purposes only - property of the publisher öbv

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