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ParisChiyann Group Title

3. Which of the following is NOT a way that water is used in a nuclear power station? (1 point) ~Water cools the steam in the turbine chamber. ~Water is changed to steam by heat released by the reactor core. ~Steam makes the turbines rotate. ~Running water cools the rotating turbines.

  • one year ago
  • one year ago

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  1. Carl_Pham Group Title
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    I can see why you posted this. They're all somewhat reasonable. This isn't a really good question, in my opinion, since answering it correctly doesn't really require any good insight into how water functions in a power plant. But FYI, here's how it does: the reactor core generates huge amounts of heat, as a result of the nuclear fission going on in it (as well as the radioactive decay of the results of the nuclear fission reaction). In the most common type of power reactor, water is circulated through the core to cool the core off, so it doesn't melt, and to transport away this heat, which is (as we'll see) very useful. The water is often under pressure so it doesn't boil even though its temperature goes way above 100C. This very hot water is also quite radioactive, since it's in contact with the intensely radioactive core. You don't want to run it through power turbines et cetera, so you can keep the radioactivitiy confined. So you let this very hot "primary coolant" water come into contact with secondary water, e.g. by letting the primary water flow through tubes around which the secondary water flows. This secondary water gets heated up by the primary water, and, since it's not usually under pressure, turns to steam. The steam is now not radioactive, or not much, since it doesn't come directly in contact with the core or the primary water. The steam pushes hard against the walls of the pipe, since it occupies much more space than the water from which it came. You pipe that high-pressure steam to a turbine, where it expands in a mighty jet and turns the blades of the turbine fast. This motion turns the shaft of an attached alternator, which creates AC electricity. That's how the power plant makes electricity. Once the steam passes through the turbine, it needs to be turned back into water, so it can be reheated again. This is often done by putting it in contact with still a third source of water, cool water, which often comes from a nearby ocean or river (which is why nuclear power plants are typically situated near oceans or rivers). The cool water cools down the steam and returns it to water, and then it's pumped back into contact with the primary water to get hot again. You can see the only thing the water hasn't for sure done yet is cool the turbine blades. Now, some turbines could use cooling, e.g. those used in supersonic airplane engines, where the gases flowing through them can be exceedingly hot, easily hot enough to melt common metals. But the turbines in nuclear power plants don't spin that fast, and they only have hot steam to deal with, which is much lower temperature than the melting point of the metal, so they probably don't need much cooling. And if you did want to cool them, you'd have to do it from the inside, with tiny channels through the blades, because if you run the water over the *outside* you will cool the steam flowing through the turbine prematurely, cutting off the power it produces. But putting tiny channels in the turbine blades would be really, really expensive. So that's very, very unlikely. All these facts point to the last answer as being likely your best choice.

    • one year ago
  2. Coday12 Group Title
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    D

    • 6 months ago
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