Steven Cowley 談核融合是能源的未來希望

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講者：Steven Cowley
2009年7月演講，2009年12月在TED上線
MyOOPS開放式課程
翻譯：洪曉慧
編輯：劉契良
簡繁轉換：陳盈
後製：洪曉慧
字幕影片後制：謝旻均
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Steven Cowley 談核融合是能源的未來希望
關鍵問題是，「我們何時能達成核融合反應？」自從我們知道核融合開始，確實已有一段漫長的時間了。從1920年，當愛丁頓爵士和英國科學促進協會推測，這就是太陽光為何會發光時，我們開始知道核融合。
我一直很擔心資源。我不知道你們怎麼想，但當我母親給我食物，我總是從我不喜歡的開始，排列到我喜歡的。我先吃不喜歡的，因為你會想要保存喜歡的。我是一個總是擔心資源的孩子，當有人告訴我，我們將多快就用盡了世界的資源，我變得非常苦惱，就像是，當我瞭解到地球只能再生存50億年，便會被太陽吞噬掉一樣苦惱，這是我生活中的大事件，還真是個奇怪的孩子（笑聲）。
目前來說，能源主要來自於資源。許多國家花了很多資金，將能源從地下採出。本國的燃煤供電工業革命－如石油、天然氣，抱歉（笑聲），天然氣等。當普丁先生關閉天然氣閥門時，我可能是唯一真正開心的人，因為我得到的預算也升高了。
我們現今正受制於其的東西，就是我們越來越快將其用盡的東西。當我們試圖使生活在第三世界、或發展中國家的幾十億人擺脫貧困，我們使用能源的速度也越來越快；而這些資源正在消失。未來製造能源的方式，不是來自於資源，而是來自於知識。如果你看看50年後的未來，我們製造能源的方式可能是這三者之一：（核融合、核分裂、太陽能），加上使用風力，或其他方式，但這些將成為能源驅動的基載。
太陽能是可行的。我們當然必須發展太陽能，但我們還需獲得很多知識，才能使太陽能成為世界能源供應的基載。核分裂；我們政府將建造6個新的核電廠，他們將建造6個新的核電廠，之後可能更多。中國正在建造核電廠；大家都是。因為他們知道，這是一個確保得到無碳能源的方法。
但如果你想知道，什麼是完美的能源？完美的能源不佔太多空間、幾乎取之不盡、安全、不會釋放任何碳到大氣中、不會留下任何長存的放射性廢物，它就是核融合。但有一個困境；當然，總會有一些困境。核融合很難達成。我們已不斷嘗試了50年。
Okay，什麼是核融合？要來談核物理學了。抱歉，但這讓我感到很興奮（笑聲），我是個奇怪的孩子。產生核能的原因很簡單，最穩定的是鐵原子核，它就在元素週期表中央，它是一個中型原子核。如果想獲得能源，就必須朝鐵的組態進行。因此，鈾非常大，它傾向於分裂；但小原子傾向於結合在一起。小原子核傾向於結合在一起，以形成近似鐵的大原子。
你可以由這種方式得到能源。事實上，這正是恆星進行的方式。在恆星中心，氫結合形成氦，氦結合形成碳，再形成氧；所有物質的形成都在恆星中心進行。但這是一個艱難的過程。因為，如你所知，恆星中心相當熾熱。從定義上看來似乎如此。這裡有個反應，或許是最簡單的核融合反應，就是氫的兩個同位素之間的反應。這兩種氫，其一為氘，它是重氫，可由海水獲得；而氚是超重的氫。
當這兩個均帶有電荷的原子核相距遙遠時，將它們推近，會使它們彼此相斥。但是當你使它們足夠接近，某種所謂的強大力量開始作用，將它們拉在一起。因此，它們大多時候是相斥的。你使它們愈來愈接近，然後在某一點上，強大力量將它們拉在一起，一會兒，它們成為氦5，因為其內會有五個粒子。
這就是其過程。氘和氚結合在一起形成氦5，當氦分裂，釋出一個中子，也釋出大量能量。如果你能使某種東西達到約 1.5億度，粒子會很快的彼此碰撞。當每次碰撞都在恰到好處的結構位置時，這將會發生。它將釋放能量，這就是所謂的核融合能，這就是我們想要達成的反應。
關於這個反應有個棘手處。嗯，有個棘手處－你必須使它達到 1.5億度。但還有一個關於反應的棘手處－它相當熾熱。關於反應的棘手處是－氚不存在於自然界中，你必須由別的東西來製造它；你可由鋰來製造它。這個反應寫在下方（鋰與中子作用產生氚）。這是鋰 6，加上一個中子，會產生更多的氦加上氚，這就是製造氚的方法。幸運的是，如果你能夠進行這個核融合反應，就會得到一個中子，所以你可以做到這一點。
為什麼我們非要費心去做這個呢？這就是基本上為什麼我們要費心這麼做。如果畫出我們還剩下多少燃料，以目前世界消耗量為單位，經由這個，你可以看到只剩下幾十年的石油量－補充一下，這條藍線是現有資源的最低估計，黃線是最樂觀的估計。
經由這個，你會看到只剩幾十年，也許只剩100年的化石燃料。天知道我們真的不想將其燃燒殆盡，因為它會在空氣中產生極大量的碳。我們來看鈾，以目前的反應爐技術來說，我們確實沒有很多的鈾，我們將必須從海水中提取鈾－就是這條黃線，以使傳統的核電廠能確實對我們貢獻良多。這令人有點震驚，因為事實上，我們政府依賴它來使我們遵守京都協議，並竭盡所能進行這類工作。
若要有更多進展，就必須擁有增殖技術。增殖技術－就是快速滋生。那是相當危險的；最重要的一項在右邊，就是世界上存有的鋰。鋰存在於海水中，就是那條黃線；在海水中，我們還有相當於三千萬年的核融合燃料，大家都可以獲取它，這就是為什麼我們想要進行核融合！它是否具有成本競爭力？根據估計，我們認為實際上建造一個核融合電廠的成本，不超過相當於目前電力的價格。
我們將如何做呢？我們必須使某種裝置保持在1.5億度。事實上，我們已完成了，我們用磁場來維持它。在其內部，就是這個環形，甜甜圈形中心，其中心為1.5億度，它的中心在1.5億度保持沸騰狀態。我們確實能夠達成核融合，這正在預期中進行。這是JET，它是世界上唯一能實際進行核融合的機器（JET，世界上最大的核融合實驗）。
當人們說核融合是30年後的事了，必定如此…。我說：「是的，但我們確實已經完成了」，對嗎？我們能夠做到核融合。在這個裝置的中心，我們在1997年製造了1600萬瓦的核融合能。在2013年，我們會再次將它啟動，並打破所有紀錄。但這並不是真正的核融合能。這只是使一些核融合發生。我們必須做這些，我們必須使它成為一個核融合反應爐，因為我們希望為地球獲得相當於三千萬年的核融合能，這是我們正在建造的裝置（ITER：國際熱核實驗反應爐）。
做這個研究是非常昂貴的。事實證明你無法就在桌面上進行核融合。除了那些關於冷核融合的無稽之談。對嗎？你無法這麼進行，你必須在一個非常大的裝置中進行，世界一半以上的人口參與建造這個裝置。就在法國南部，這是個進行實驗的好地方。七個國家參與建造工程，這將花費100億美元，我們將生產五億瓦的核融合能；但這還不是電力。我們必須建造這個（EU發電廠），我們必須建造一個發電廠，我們必須用這個非常複雜的技術，開始把電力放到電網中。我非常希望它能比實際所需的時間更快成真，但目前我們所能想像的，是在2030年代的某個時刻。
我希望會有所不同，我們目前確實需要它。在未來5年中，本國將面臨能源問題；2030年似乎遙不可及，但現在我們不能放棄，我們必須向前邁進，使核融合成真。希望我們有更多的錢，更多的資源，但我們正以此為目標：在2030年代的某刻－真正有來自核融合的電力。非常感謝（掌聲）

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以下為系統擷取之英文原文
About this talk
Physicist Steven Cowley is certain that nuclear fusion is the only truly sustainable solution to the fuel crisis. He explains why fusion will work -- and details the projects that he and many others have devoted their lives to, working against the clock to create a new source of energy.

About Steven Cowley

Steven Cowley directs the UK's leading fusion research center. Soon he'll helm new experiments that may make cheap fusion energy real on a commercial scale. Full bio and more links

Transcript

The key question is, "When are we going to get fusion?" It's really been a long time since we've known about fusion. We've known about fusion since 1920, when Sir Arthur Stanley Eddington and the British Association for the Advancement of Science conjectured that that's why the sun shines.

I've always been very worried about resource. I don't know about you, but when my mother gave me food I always sorted the ones I disliked from the ones I liked. And I ate the disliked ones first, because the ones you like, you want to save. And as a child you're always worried about resource. And once it was sort of explained to me how fast we were using up the world's resources, I got very upset, about as upset as I did when I realized that the Earth will only last about five billion years before it's swallowed by the sun. Big events in my life, a strange child. (Laughter)

Energy, at the moment, is dominated by resource. The countries that make a lot of money out of energy have something underneath them. Coal-powered industrial revolution in this country -- oil, gas, sorry. (Laughter) Gas, I'm probably the only person who really enjoys it when Mister Putin turns off the gas tap, because my budget goes up.

We're really dominated now by those things that we're using up faster and faster and faster. And as we try to lift billions of people out of poverty in the Third World, in the developing world, we're using energy faster and faster. And those resources are going away. And the way we'll make energy in the future is not from resource, it's really from knowledge. If you look 50 years into the future, the way we probably will be making energy is probably one of these three, with some wind, with some other things, but these are going to be the base load energy drivers.

Solar can do it, and we certainly have to develop solar. But we have a lot of knowledge to gain before we can make solar the base load energy supply for the world. Fission. Our government is going to put in six new nuclear power stations. They're going to put in six new nuclear power stations, and probably more after that. China is building nuclear power stations. Everybody is. Because they know that that is one sure way to do carbon-free energy.

But if you wanted to know what the perfect energy source is, The perfect energy source is one that doesn't take up much space, has a virtually inexhaustible supply, is safe, doesn't put any carbon into the atmosphere, doesn't leave any long lived radioactive waste, it's fusion. But there is a catch. Of course there is always a catch in these cases. Fusion is very hard to do. We've been trying for 50 years.

Okay. What is fusion? Here comes the nuclear physics. And sorry about that, but this is what turns me on. (Laughter) I was a strange child. Nuclear energy comes for a simple reason. The most stable nucleus is iron, right in the middle of the periodic table. It's a medium-sized nucleus. And you want to go towards iron if you want to get energy. So, uranium, which is very big, wants to split. But small atoms want to join together, small nuclei want to join together to make bigger ones to go towards iron.

And you can get energy out this way. And indeed that's exactly what stars do. In the middle of stars you're joining hydrogen together to make helium and then helium together to make carbon, to make oxygen, all the things that you're made of are made in the middle of stars. But it's a hard process to do because, as you know, the middle of a star is quite hot, almost by definition. And there is one reaction That's probably the easiest fusion reaction to do. It's between two isotopes of hydrogen, two kinds of hydrogen, deuterium, which is heavy hydrogen, which you can get from seawater, and tritium which is super-heavy hydrogen.

These two nuclei, when they're far apart, are charged. And you push them together and they repel. But when you get them close enough, something called the strong force starts to act and pulls them together. So, most of the time they repel. You get them closer and closer and closer and then at some point the strong force grips them together. For a moment they become helium 5, because they've got five particles inside them.

So, that's that process there. Deuterium and tritium goes together makes helium 5. Helium splits out, and a neutron comes out and lots of energy comes out. If you can get something to about 150 million degrees, things will be rattling around so fast that every time they collide in just the right configuration, this will happen, and it will release energy. And that energy is what powers fusion. And it's this reaction that we want to do.

There is one trickiness about this reaction. Well, there is a trickiness that you have to make it 150 million degrees, but there is a trickiness about the reaction yet. It's pretty hot. The trickiness about the reaction is that tritium doesn't exist in nature. You have to make it from something else. And you make if from lithium. That reaction at the bottom, that's lithium 6, plus a neutron, will give you more helium, plus tritium. And that's the way you make your tritium. But fortunately, if you can do this fusion reaction, you've got a neutron, so you can make that happen.

Now, why the hell would we bother to do this? This is basically why we would bother to do it. If you just plot how much fuel we've got left, in units of present world consumption. And as you go across there you see a few tens of years of oil -- the blue line, by the way, is the lowest estimate of existing resources. And the yellow line is the most optimistic estimate.

And as you go across there you will see that we've got a few tens of years, and perhaps 100 years of fossil fuels left. And god knows we don't really want to burn all of it. Because it will make an awful lot of carbon in the air. And then we get to uranium. And with current reactor technology we really don't have very much uranium. And we will have to extract uranium from sea water, which is the yellow line, to make conventional nuclear power stations actually do very much for us. This is a bit shocking, because in fact our government is relying on that for us to meet Kyoto, and do all those kind of things.

To go any further you would have to have breeder technology. And breeder technology is fast breeders. And that's pretty dangerous. The big thing, on the right, is the lithium we have in the world. And lithium is in sea water. That's the yellow line. And we have 30 million years worth of fusion fuel in sea water. Everybody can get it. That's why we want to do fusion. Is it cost-competitive? We make estimates of what we think it would cost to actually make a fusion power plant. And we get within about the same price as current electricity.

So, how would we make it? We have to hold something at 150 million degrees. And, in fact, we've done this. We hold it with a magnetic field. And inside it, right in the middle of this toroidal shape, doughnut shape, right in the middle is 150 million degrees. It boils away in the middle at 150 million degrees. And in fact we can make fusion happen. And just down the road, this is JET. It's the only machine in the world that's actually done fusion.

When people say fusion is 30 years away, and always will be, I say, "Yeah, but we've actually done it." Right? We can do fusion. In the center of this device we made 16 megawatts of fusion power in 1997. And in 2013 we're going to fire it up again and break all those records. But that's not really fusion power. That's just making some fusion happen. We've got to take that, we've got to make that into a fusion reactor. Because we want 30 million years worth of fusion power for the Earth. This is the device we're building now.

It gets very expensive to do this research. It turns out you can't do fusion an a table top despite all that cold fusion nonsense. Right? You can't. You have to do it in a very big device. More than half the world's population is involved in building this device in southern France. Which is a nice place to put an experiment. Seven nations are involved in building this. It's going to cost us 10 billion. And we'll produce half a gigawatt of fusion power. But that's not electricity yet. We have to get to this. We have to get to a power plant. We have to start putting electricity on the grid in this very complex technology. And I'd really like it to happen a lot faster than it is. But at the moment all we can imagine is sometime in the 2030s.
I wish this were different. We really need it now. We're going to have a problem with power in the next five years in this country. So 2030 looks like an infinity away. But we can't abandon it now; we have to push forward, get fusion to happen. I wish we had more money, I wish we had more resources. But this is what we're aiming at, sometime in the 2030s -- real electric power from fusion. Thank you very much. (Applause)
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