What is a chain reaction 1

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81 The radioactive behavior of matter  Learning objective check 16, page 91 Tritium Deuterium Fusion Neutron Proton Helium Neutron H + + + H He n Energy 2 1 3 1 4 2 1 0 81.4 Principle of nuclear fusion 81.3 The controlled chain reaction 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 81.1 Principle of a pressurized water reactor in a nuclear power plant 81.5 The sun is a large fusion reactor. 81.6 View into a research reactor Neutron fuel rods U-235 (2−3%) U-238 Water (moderator) Control rods 81.2 Control of the chain reaction in a nuclear reactor 3. How do nuclear reactors 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 by the heat that is released. The generated water vapor drives the turbine of a generator. The water also serves as a moderator - this is the name given to materials that can slow down neutrons. This is necessary for the split to take place. In order to be able to control the chain reaction, control rods made of cadmium or boron compounds that can capture neutrons are required. The conspicuous cooling towers only give off the heat from the cooling water to the environment. The controlled chain reaction (Fig. 81.3) Build the dominoes as in V1. Stop the chain reaction in a targeted manner by placing a ruler between the standing stones. M A nuclear reactor generates heat by fission. The chain reaction is regulated. The heat creates water vapor, which runs the turbine of a generator. 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 disasters of enormous proportions, as in 1986 in Chernobyl and 2011 in Fukushima. Large areas of land will be contaminated by radioactive substances for many years. • The fission products resulting from the fission have to be safely stored for thousands of years, for example in abandoned mines. 4. What does nuclear fusion mean? The sun gives off enormous amounts of energy through the fusion of hydrogen atom nuclei to form helium nuclei. This requires high temperatures of around 20 million Kelvin. Until now, nuclear fusion has only been used in hydrogen bombs, not in power plants. V2 For testing purposes only - property of the publisher öbv

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