美国国家公共电台 NPR--U.S. reaches a fusion power milestone. Will it be enough to save the planet?

U.S. reaches a fusion¹ power milestone². Will it be enough to save the planet?

Transcript³

Scientists with the U.S. Department of Energy have reached a breakthrough in nuclear fusion.

For the first time ever in a laboratory, researchers were able to generate more energy from fusion reactions than they used to start the process. The total power out was around 150% of the power that was put in by 192 laser beams.

"America has achieved a tremendous scientific breakthrough," Energy Secretary Jennifer Granholm said at a press conference.

The achievement came at the National Ignition Facility (NIF), a $3.5 billion laser complex at Lawrence Livermore National Laboratory in California. For more than a decade, NIF has struggled to meet its stated goal of producing a fusion reaction that generates more energy than it consumes.

But that changed in the dead of night on Dec. 5. At 1 AM local time, researchers used the lasers to zap a tiny pellet of hydrogen fuel. The lasers put out 2.05 megajoules of energy, and the pellet released roughly 3.15 megajoules.

It's a major milestone, one that the field of fusion science has struggled to reach for more than half a century.

"In our laboratory we've been working on this for almost 60 years," says Mark Herrmann, who oversees⁴ the NIF program at Livermore. "This is an incredible team accomplishment⁵."

Researchers say that fusion energy could one day provide clean, safe electricity without greenhouse gas emissions⁶. But even with this announcement, independent scientists believe that dream remains⁷ many decades away.

Unless there's an even larger breakthrough, fusion is unlikely to play a major role in power production before the 2060s or 2070s, says Tony Roulstone, a nuclear engineer at Cambridge University in the U.K., who's done an economic analysis of fusion power.

"I think the science is great," Roulstone says of the breakthrough. But many engineering obstacles remain. "We don't really know what the power plant would look like."

At that rate, fusion power won't come soon enough for the Biden administration, which is seeking to bring America's net greenhouse gas emissions to zero by 2050 — a goal that experts say must be met to avoid the worst effects of climate change.

Laser power

Fusion power has long fired the imaginations of nuclear scientists and engineers. The technology would work by "fusing" light elements of hydrogen into helium, generating an enormous amount of energy. It's the same process that powers the sun, and it's far more efficient than current nuclear "fission⁸" technology. What's more, fusion power plants would generate relatively⁹ little nuclear waste, and they could run off of hydrogen readily found in seawater.

The ten-story-tall NIF facility is the world's most powerful laser system. It is designed to aim its 192 beams onto a tiny cylinder¹⁰ of gold and depleted¹¹ uranium. Inside the cylinder is a diamond capsule smaller than a peppercorn. That capsule is where the magic happens — it's filled with two isotopes¹² of hydrogen that can fuse together to release astonishing amounts of energy.

When the lasers are fired at the target, they generate x-rays that vaporize the diamond in a tiny fraction of a second. The shockwave from the diamond's destruction crushes the hydrogen atoms, causing them to fuse and release energy.

NIF first opened in 2009, but its initial laser shots fell well short of expectations. The hydrogen in the target was failing to "ignite", and the Department of Energy had little to show for the billions it had invested.

Then in August 2021, after years of slow but steady progress, physicists¹³ were able to ignite the hydrogen inside the capsule, creating a self-sustaining burn. The process is analogous¹⁴ to lighting¹⁵ gasoline, says Riccardo Betti, the chief scientist of the laboratory for laser energetics at the University of Rochester. "You start with a little spark, and then the spark gets bigger and bigger and bigger, and then the burn propagates through."

Bang in a box

This self-burning ignition actually resembles a process similar to that of a modern thermonuclear warhead, albeit¹⁶ on a much smaller scale.

The United States has not tested a nuclear weapon since 1992, and the primary purpose of the NIF facility is to conduct very small-scale bangs that closely mimic¹⁷ nukes. The data from these tiny explosions are fed into complex computer simulations that help physicists understand whether the nation's nuclear weapons remain reliable, despite decades on the shelf.

"We use these experiments to get experimental data to compare to our simulations," says Herrmann, who also oversees nuclear weapons research at the lab. In addition, he says the radiation from the explosions can be used to test components¹⁸. Such tests will make sure that new and refurbished parts of nuclear weapons behave as expected.

More out than in

Even after last-year's achievement, there was still one more goal to reach – producing more power from the tiny capsule than the lasers put in.

Herrmann says that the August 2021 shot gave the team a starting point. "That put us on the threshold," he says. "We actually made a lot of progress in the last year." Steady improvements in the lasers, targets, and other components gradually put the facility in a position where it could finally generate energy from the capsule.

"It is a big scientific step," says Ryan McBride, a nuclear engineer at the University of Michigan. But, McBride adds, that does not mean that NIF itself is producing power. For one thing, he says, the lasers require more than 300 megajoules worth of electricity to produce around 2 megajoules of ultraviolet laser light. In other words, even if the energy from the fusion reactions exceeds the energy from the lasers, it's still only around one percent of the total energy used.

Moreover, it would take many capsules exploding over and over to produce enough energy to feed the power grid¹⁹. "You'd have to do this many, many times a second," McBride says. NIF can currently do around one laser "shot" a week.

Still, the long-term potential is staggering, says Arati Dasgupta, a nuclear scientist with the U.S. Naval²⁰ Research Laboratory. Whereas a giant pile of carbon-spewing coal might generate electricity for a matter of minutes, the same quantity of fusion fuel could run a power plant for years–with no carbon dioxide emissions. "This is a great demonstration²¹ of the possibility," Dasgupta says. But, she adds, many technical issues remain. "It's a huge undertaking²²."

And getting economical power out of a fusion reactor²³ is even tougher, says Roulstone. He and his team looked at a rival technology known as a tokamak and concluded that there were still an enormous number of challenges to making fusion work economically. His analysis estimated that fusion won't be ready for the grid before the second half of this century. He believes the same timeline holds for NIF's technology. "It's not very easy to see how you scale this into a power reactor quickly," he says.

By then most climate experts believe the world will have to have already made drastic cuts to carbon emissions to avoid the worst effects of climate change. To limit warming to 2.7 degrees Fahrenheit²⁴ by the end of the century, the world must nearly halve²⁵ its carbon output by 2030 — a far shorter timescale than what's needed to develop fusion.

Betti agrees that the timeline to building a fusion plant is "definitely decades". But, he adds, that could change. "There's always a possibility of breakthrough," he says. And the new NIF results could help spur that breakthrough forward. "You're going to get more people to look into this form of fusion, to see whether we can turn it into an energy-making system."

NPR's Rebecca Hersher contributed to this report.

1 fusion   

n.溶化；熔解；熔化状态，熔和；熔接

参考例句：

• Brass is formed by the fusion of copper and zinc. 黄铜是通过铜和锌的熔合而成的。
• This alloy is formed by the fusion of two types of metal.这种合金是用两种金属熔合而成的。

2 milestone   

n.里程碑；划时代的事件

参考例句：

• The film proved to be a milestone in the history of cinema.事实证明这部影片是电影史上的一个里程碑。
• I think this is a very important milestone in the relations between our two countries.我认为这是我们两国关系中一个十分重要的里程碑。

3 transcript   

n.抄本，誊本，副本，肄业证书

参考例句：

• A transcript of the tapes was presented as evidence in court.一份录音带的文字本作为证据被呈交法庭。
• They wouldn't let me have a transcript of the interview.他们拒绝给我一份采访的文字整理稿。

4 oversees   

v.监督，监视( oversee的第三人称单数 )

参考例句：

• She oversees both the research and the manufacturing departments. 她既监督研究部门又监督生产部门。 来自《简明英汉词典》
• The Department of Education oversees the federal programs dealing with education. 教育部监管处理教育的联邦程序。 来自互联网

5 accomplishment   

n.完成，成就，（pl.）造诣，技能

参考例句：

• The series of paintings is quite an accomplishment.这一系列的绘画真是了不起的成就。
• Money will be crucial to the accomplishment of our objectives.要实现我们的目标，钱是至关重要的。

6 emissions   

排放物( emission的名词复数 )； 散发物（尤指气体）

参考例句：

• Most scientists accept that climate change is linked to carbon emissions. 大多数科学家都相信气候变化与排放的含碳气体有关。
• Dangerous emissions radiate from plutonium. 危险的辐射物从钚放散出来。

7 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

8 fission   

n.裂开；分裂生殖

参考例句：

• The fission of the cell could be inhibited with certain chemicals.细胞的裂变可以通过某些化学药品加以抑制。
• Nuclear fission releases tremendous amounts of energy.核裂变释放出巨大的能量。

9 relatively   

adv.比较...地，相对地

参考例句：

• The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
• The operation was relatively painless.手术相对来说不痛。

10 cylinder   

n.圆筒，柱(面)，汽缸

参考例句：

• What's the volume of this cylinder?这个圆筒的体积有多少？
• The cylinder is getting too much gas and not enough air.汽缸里汽油太多而空气不足。

11 depleted   

adj. 枯竭的, 废弃的 动词deplete的过去式和过去分词

参考例句：

• Food supplies were severely depleted. 食物供应已严重不足。
• Both teams were severely depleted by injuries. 两个队都因队员受伤而实力大减。

12 isotopes   

n.同位素；同位素( isotope的名词复数 )

参考例句：

• the many isotopes of carbon 碳的诸多同位素
• Tritium is one of the mildest radioactive isotopes. 氚是最和缓的放射性同位素之一。 来自《简明英汉词典》

13 physicists   

物理学家( physicist的名词复数 )

参考例句：

• For many particle physicists, however, it was a year of frustration. 对于许多粒子物理学家来说，这是受挫折的一年。 来自英汉非文学 - 科技
• Physicists seek rules or patterns to provide a framework. 物理学家寻求用法则或图式来构成一个框架。

14 analogous   

adj.相似的；类似的

参考例句：

• The two situations are roughly analogous.两种情況大致相似。
• The company is in a position closely analogous to that of its main rival.该公司与主要竞争对手的处境极为相似。

15 lighting   

n.照明，光线的明暗，舞台灯光

参考例句：

• The gas lamp gradually lost ground to electric lighting.煤气灯逐渐为电灯所代替。
• The lighting in that restaurant is soft and romantic.那个餐馆照明柔和而且浪漫。

16 albeit   

conj.即使；纵使；虽然

参考例句：

• Albeit fictional,she seemed to have resolved the problem.虽然是虚构的，但是在她看来好象是解决了问题。
• Albeit he has failed twice,he is not discouraged.虽然失败了两次，但他并没有气馁。

17 mimic   

v.模仿，戏弄；n.模仿他人言行的人

参考例句：

• A parrot can mimic a person's voice.鹦鹉能学人的声音。
• He used to mimic speech peculiarities of another.他过去总是模仿别人讲话的特点。

18 components   

（机器、设备等的）构成要素，零件，成分； 成分( component的名词复数 )； [物理化学]组分； [数学]分量； （混合物的）组成部分

参考例句：

• the components of a machine 机器部件
• Our chemistry teacher often reduces a compound to its components in lab. 在实验室中化学老师常把化合物分解为各种成分。

19 grid   

n.高压输电线路网；地图坐标方格；格栅

参考例句：

• In this application,the carrier is used to encapsulate the grid.在这种情况下，要用载体把格栅密封起来。
• Modern gauges consist of metal foil in the form of a grid.现代应变仪则由网格形式的金属片组成。

20 naval   

adj.海军的，军舰的，船的

参考例句：

• He took part in a great naval battle.他参加了一次大海战。
• The harbour is an important naval base.该港是一个重要的海军基地。

21 demonstration   

n.表明，示范，论证，示威

参考例句：

• His new book is a demonstration of his patriotism.他写的新书是他的爱国精神的证明。
• He gave a demonstration of the new technique then and there.他当场表演了这种新的操作方法。

22 undertaking   

n.保证，许诺，事业

参考例句：

• He gave her an undertaking that he would pay the money back with in a year.他向她做了一年内还钱的保证。
• He is too timid to venture upon an undertaking.他太胆小，不敢从事任何事业。

23 reactor   

n.反应器；反应堆

参考例句：

• The atomic reactor generates enormous amounts of thermal energy.原子反应堆发出大量的热能。
• Inside the reactor the large molecules are cracked into smaller molecules.在反应堆里，大分子裂变为小分子。

24 Fahrenheit   

n./adj.华氏温度；华氏温度计(的)

参考例句：

• He was asked for the boiling point of water in Fahrenheit.他被问到水的沸点是华氏多少度。
• The thermometer reads 80 degrees Fahrenheit.寒暑表指出华氏80度。

25 halve   

vt.分成两半，平分；减少到一半

参考例句：

• Let's halve the project between our two teams.让我们两个队平均分担这项工程吧。
• I'll halve expenses with you.我要跟你平均分摊费用。