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Anonymous asked in Science & MathematicsPhysics · 1 decade ago

Why is energy released when the nuclear reactions take place in a nuclear power plant? Use nuclear fusion?

Also the same question applies for the sun.

2 Answers

  • 1 decade ago
    Favorite Answer

    Energy is released because of E=mc^2.

    The atomic nucleus is made up of protons and neutrons. Carbon-12, for example, has 6 protons and 6 neutrons. If you calculate the mass of 6 protons and 6 neutrons, however, it turns out to be a little bit heavier than the actual nucleus. That's because some mass is lost when the protons and neutrons join together to become a nucleus.

    That lost mass is called "mass defect". The missing mass is turned into energy (use the equation E = mc^2 to figure out how much). If you wish to split the nucleons apart, you have to provide that energy back to the nucleus. For that reason, it's called "binding energy".

    If you calculate the amount of binding energy per nucleon for every isotope on the periodic table, you find that isotopes of nickel (element #28) and iron (element #26) have the greatest values.

    When nuclei with more than 26 or 28 protons split apart, the two or more resulting nuclei have a higher binding energy per nucleon than the parent nucleus did. That means that some of the energy that could have been used to split the nucleus was lost. Where did it go? It was released, ultimately as heat energy.

    In a nuclear reactor, the heat from splitting uranium (element #92) atoms boils water, and the steam turns a turbine, which produces electricity. That's power production via nuclear fission.

    Nuclear fusion is when two lighter nuclei (with fewer than 26 protons) join together. Although the process is different, the end result is the same: the reaction is extremely exothermic. The problem is that it's very hard to get atomic nuclei close enough to each other to fuse. Since all nuclei are positively charged, they repel each other strongly. You have to get the nuclei moving VERY fast in order for them to collide and stick, and that takes very high temperatures.

    The Sun manages those temperatures in its core, but we have problems doing so on Earth. We've investigated ways to catalyze nuclear fusion, so we can make it happen at lower temperatures, but so far we've had only limited success. We're still a long way off from building a profitable nuclear fusion reactor.

  • Anonymous
    5 years ago

    Nuclear reactions are not like chemical reactions. The processes for releasing energy are different and also much more powerful. The sun produces energy primarily by fusing hydrogen atoms, which makes helium atoms and also releases both energy in the form of radiation of a variety of types. This is very complicated stuff and you would not be able to understand it without taking years of specialized engineering and science. I don't understand it all that well either. In the sun the nuclear fusion take place deep in the interior of the star and releases a lot of deadly radiation, which is absorbed by outer layers of the sun. That converts it to heat and light, which eventually shines on the Earth. Raw sunlight does contain a fair amount of deadly radiation that is largely absorbed by the Earth's atmosphere. Even so some damaging radiation makes it through, which is why we can get a sun burn and skin cancer. If we did the same kind of nuclear reactions on Earth, we would have to deal with the deadly radiation that is trapped within the sun and which our atmosphere protects us from.

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