跟讀練習: The Magic of Thorium Nuclear Reactors - 通過影片學習英語口語
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Thorium is a kind of miraculous element.
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Thorium found in nature isn't fissile – the atom's nucleus won't split when it absorbs a neutron.
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And yet, if you put a chunk of this same thorium in a special nuclear reactor,
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after a while most of the thorium will be gone,
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a whole bunch of energy will have been generated,
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and you'll be left with typical byproducts of fission.
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It's as if thorium is fissile, even though it's not.
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This is the genius of thorium breeder reactors.
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Oh, and I should disclose here that this video is sponsored by Copenhagen Atomics,
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who are working to make thorium power a reality,
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but they didn't get any say in the video and didn't get to review it before posting.
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The standard oversimplified picture of a fission reactor is,
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a uranium nucleus splits apart,
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or fissions, releasing heat energy and two or three neutrons,
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and those neutrons go on to be captured by more uranium nuclei and cause them to fission,
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releasing more heat energy and more neutrons, and so on.
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The heat is used to generate electricity,
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the neutrons to maintain the fission chain reaction.
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However, the actual story is more complicated.
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When a nucleus splits, there are actually four things that can happen to the neutrons it emits.
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One, like we've already mentioned,
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they can be captured by a fissile atom like uranium-235,
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causing it to fission and release more neutrons,
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and this part has to happen on average at least once per fission to sustain the chain reaction.
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Two, neutrons can be captured by the nuclei of other atoms in the reactor,
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without causing fission, like maybe the metal case,
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or the moderator, or the control rods, or whatever.
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3 Neutrons can escape and leave the reactor entirely.
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Or 4 A neutron can be captured by an atom that's not fissile,
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and transmute it into an atom that is fissile.
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Because remember, these are atomic nuclei we're dealing with.
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Absorption of a neutron will turn uranium-238 into uranium-239,
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the number is just the total number of protons and neutrons.
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And uranium-239 can then radioactively decay into neptunium-239,
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which can then decay into plutonium-239, which is fissile.
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If the capture of a neutron transforms a non-fissile element into a fissile one,
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it's called a fertile capture.
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And fertile capture is what makes thorium useful.
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In fact, even in a normal uranium reactor,
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fertile capture accounts for over a third of the energy generated by the reactor.
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A normal nuclear reactor uses uranium-235,
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which is fissile, but naturally occurring uranium ore contains only 0.7% uranium-235.
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Almost all the rest is uranium-238,
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which is essentially non-fissile, but it is fertile.
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Even when using fuels with enriched levels of uranium-235 undergoing fission,
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there's so much non-fissile U-238 around that some of the chain reaction neutrons instead transform U-238 into plutonium-239,
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which can then fission.
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But U-235 doesn't make enough neutrons,
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and U-238 doesn't turn into plutonium easily enough
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that you can both sustain a fission chain reaction and continue to transform new fissile fuel.
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So at the end you're left with a big chunk of unfissioned but still full of radioactive waste, uranium-238.
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There's a different kind of reactor,
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called a fast breeder reactor,
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that uses plutonium as the primary fissile fuel,
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and uranium-238 as a fertile secondary source.
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This combination can both sustain the fission chain reaction and transform new fuel in a self-sustaining way.
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But fast breeder reactors are less researched,
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more expensive, and harder to run effectively.
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For now.
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This is where thorium comes in.
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The same route used in the transformation of uranium-238 to plutonium-239 can be replicated down here,
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starting instead with thorium-232.
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By adding a neutron, we get thorium-233,
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which decays to protactinium-233, which decays to uranium-233,
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which is fissile and can be used to generate energy.
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So if you load your reactor with thorium-232,
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which, remember, is not fissile,
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and you throw in some starter fissile fuel,
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then for each fission reaction,
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the number of new fissile atoms created is more than one on average,
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and the number of new atoms split is more than one on average,
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and remember those atoms give you more neutrons.
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So the transformation of thorium,
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and the fission of uranium,
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can keep going and going and going,
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until in principle, all of the thorium is gone.
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And crucially, thorium transformation can happen in a reactor that doesn't have the same challenges as a fast breeder reactor,
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and it gets rid of most of the long-lived radioactive waste.
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And thorium is more abundant than uranium,
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and doesn't need the expensive refining process to concentrate the fissile uranium-235,
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and so you can see why people get excited about thorium.
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There are, of course, challenges and downsides to making thorium reactors,
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which is why we don't have and so far have never had commercial energy generation from thorium.
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But that's fertile material for another time.
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Getting commercial power from thorium may soon be possible thanks to the work of organizations such as this video's sponsor, Copenhagen Atomics.
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Copenhagen Atomics is building compact,
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modular thorium reactors to produce cheap energy.
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Unlike traditional nuclear power stations,
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which are giant infrastructure projects,
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Copenhagen Atomics are designing a self-contained reactor unit that can fit inside a shipping container.
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The reactors are based on a design pioneered over 50 years ago that uses molten salt to carry the fuel,
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resulting in fewer lost neutrons and more complete combustion,
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so you get more energy for less waste.
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These reactors can also use plutonium waste from classic nuclear reactors as fuel,
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extracting ten times more energy out of spent nuclear fuel than the initial reactor did in the first place,
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and in doing so converting long-lived radioactive waste into short-lived radioactive waste.
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In theory, these reactors could run anything from grids to ships to moon bases.
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Check out Copenhagen Atomics website to learn more about their work.
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關於本課
在本課中，學習者將通過觀看《釷核反應堆的魔力》這一影片，練習英語聽力和口語。通過深入解讀影片中的內容，您將能夠加深對核能技術的理解，並通過跟讀、模仿發音來提高您的英語口語能力，特別是在雅思口語練習方面。這個課同時也將幫助您學會如何在日常對話中使用生詞和短語，為您的語言交流增添更多的專業性和深度。
關鍵詞彙與短語
- 釷 (thorium)
- 裂變 (fission)
- 能量 (energy)
- 中子 (neutron)
- 可孕育捕獲 (fertile capture)
- 鈾 (uranium)
- 反應堆 (reactor)
- 放射性衰變 (radioactive decay)
練習技巧
為了有效地提高您的英語發音和口語表現，請遵循以下幾個練習技巧：
- 慢速練習：從影片的慢速部分開始，重複影片中的句子和段落。確保能夠準確聽到每個單詞的發音。
- 模仿重音：注意演講者的語調和重音。嘗試模仿他們的語音、語速和情感，這將幫助您提高英語發音。
- 錄音回放：錄下您自己的聲音與影片中演講者進行對比，找到需要改進之處，尤其是在複雜詞彙和短語的發音上。
- 視聽結合：觀看影片時，同時關注字幕內容，幫助您更好地理解單詞在上下文中的使用。
- 定時跟讀：選擇影片中的某一段落進行重複跟讀，儘量控制在與影片相同的時間內完成，挑戰自己的反應速度。
通過這些練習方法，利用 看YouTube學英語 的機會，您將能有效提高您的英語表達能力，特別是在雅思口語練習方面，掌握更多專業術語和表達方式，為您未來的交流打下堅實的基礎。
影片中的語法
說話人最常用的結構，並附上影片中的原話：
| 結構 | 影片中的用法 |
|---|---|
| 被動語態 be + 過去分詞 — 強調發生了什麼，而不是誰做的 | have been generated · be left · is sponsored |
| 現在完成時 have/has + 過去分詞 — 過去發生但與現在仍有關聯的事 | we've already mentioned · have never had |
什麼是跟讀法？
跟讀法 (Shadowing) 是一種有科學依據的語言學習技巧，最初開發用於專業口譯員的培訓，並由多語言者Alexander Arguelles博士普及。這個方法簡單而強大：您在聽英語母語原聲的同時立即大聲重複——就像是一個延遲1-2秒緊跟說話者的影子。與被動聽力或語法練習不同，跟讀法強迫您的大腦和口腔肌肉同時處理並模模擬實的講話模式。研究表明它能顯著提高發音準確性，語調，節奏，連讀，聽力理解和口語流利度——使其成為雅思口語備考和真實英語交流最有效的方法之一。