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  • There's a lot of talk about nuclear technology, what with Iran and Fukushima and Green Energy

  • being thrown around every day. But how do we even MAKE nuclear fuel?

  • Howdy atomic children, Trace here for DNewsDespite the controversy they often raise,

  • nuclear power plants are a huge source of energy. The Environmental Protection Agency

  • says nuclear power accounts for about 20% of electricity production in the U.S. One

  • of the reasons why is because it’s the most efficient means of extracting energy from

  • a fuel source - about 8,000 times more efficient than coal or oil. According to the Nuclear

  • Energy Institute, a fingertip-sized pellet of nuclear fuel contains as much energy as

  • "17,000 cubic feet of natural gas, 1,780 pounds of coal, or 149 gallons of oil." Nuclear energy

  • comes in two flavors, fusion or fission. Fusion is when two hydrogen atoms fuse -- this happens

  • in stars; and fission is when large "heavy" atoms are broken apart. Both release energy,

  • and both have pros and cons, but so far, we've only figured out nuclear fission; so when

  • I say fuel, I'm talking about fuel for nuclear fission.

  • Nuclear fuel is commonly referred to in the news, as "highly-enriched Uranium," but getting

  • it to that point requires a LOT of effort. In 1941, Enrico Fermi, created the first controlled

  • nuclear chain reaction using a small amount of uranium-235; and since then we've gotten

  • much better at taking uranium and creating usable fuel from it.

  • Uranium ore is most commonly mined in Canada, Australia, Niger, Kazakhstan, Russia, and

  • Namibia; though it's not THAT rare -- it's 40 times more prevalent than silver in the

  • Earth's crust. Once drilled or dug out of the ground, the uranium atoms are mixed in

  • with the surrounding minerals -- so it has to be processed -- this involves some pretty

  • intense chemistry. First, the ore is crushed, and then heated, to dry out carbon content

  • (like clay) so it can be washed away. That slurry of ore and water is leached with sulfuric

  • acid. These processes cause the uranium atoms to bond with the sulfur and oxygen forming

  • uranium oxide liquid. To get it to that yellow powder we recognize from movies, the uranium

  • is pulled out of solution using ammonia. This "yellow cake" uranium is put in barrels and

  • shipped off to be purified even MORE. At this point the uranium isn't super radioactive,

  • yetIf you stood one meter from a barrel full of U three O eight, you'd get no more

  • radiation than from the cosmic rays hitting passengers on a commercial airplane.

  • This uranium still needs to then be enriched before it can be used in power generation.

  • That yellow cake uranium is 99.3 percent Uranium 238 and only 0.7 percent of uranium-235. To

  • make the fuel, scientists need that U235 isotope -- this is where the now-famous nuclear centrifuges

  • come in. If you watch the news, you know Iran is developing a nuclear program -- whether

  • for energy or weaponry, I'll leave that to the experts; but they use centrifuges to enrich

  • that uranium.

  • As things go forward from here, it gets more dangerous, and more radioactive, so the engineering

  • has to be VERY precise or people can die. First, they take the yellowcake uranium and

  • they turn it into a gas by creating a reaction with fluorine -- the resulting uranium hexafluoride

  • gas is even MORE pure than yellowcake and ready to go in a centrifuge. A centrifuge

  • is a giant spinning container designed to use physics in order to separate materials.

  • When you donate plasma, doctors draw blood and spin it in a centrifuge. During the spinning,

  • centrifugal -- or center fleeing -- forces cause the heavier red blood cells to come

  • out of solution and collect as far from the center as possible; lighter plasma stays nearer

  • the inside! In the case of uranium, it's the same. The heavier U238 isotopes get thrown

  • outward, allowing the lighter U235 to stay closer to the middle. It's not as good as

  • blood, because there's only a 1 percent difference in mass; so it has to be spun again and again

  • in centrifuge after centrifuge THOUSANDS of times. Eventually, the gas in the middle of

  • the centrifuge gets more and more concentrated -- or ENRICHED! The gas is MORE U235! Once

  • the fuel is 5 percent U235 (95 percent U238) it's suitable for some nuclear reactors. Others

  • require as high as 20 percent. But that's nowhere NEAR enriched enough for nuclear weapons,

  • which can require as high at 90 percent U235.

  • Once it's reached the desired enrichment for the type of power plant you want to run, the

  • enriched uranium hexafluoride has to be turned into a solid by adding calcium. The calcium

  • and fluoride react, creating a salt, leaving behind only uranium oxide, which is heated

  • to 1400C and extruded into tiny ceramic pellets. Those uranium pellets are, in turn, put into

  • rods, and then hundreds or thousands of those rods can be placed in various configurations

  • inside a nuclear power plant.

  • When we talk about nuclear energy programs in other countries, world leaders get nervous.

  • And now that you know the process, can you see why? The massive centrifuges used make

  • nuclear fuel, are the same ones that could create weapons grade uranium. It requires

  • a lot of technical and chemical knowledge to GET to that point, but in the end it's

  • dig uranium out, clean it up, and then spin it!

  • Nuclear energy continues to be a controversial choice for powering the future, and it's connection

  • to nuclear weapons is clear, but how do you feel about

  • nuclear energy?

There's a lot of talk about nuclear technology, what with Iran and Fukushima and Green Energy


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B1 中級 美國腔

鈾如何成為核燃料 (How Uranium Becomes Nuclear Fuel)

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    YuSiang Chen 發佈於 2021 年 01 月 14 日