The brilliant and tragic history of nuclear fusion
Sun in a Bottle: The Strange History of Fusion and the Science of Wishful Thinking
Viking Adult, October 2008
Among all of humanity’s great quests to wrest control of nature and its own destiny, few quests have been as grand in scale and optimism as nuclear fusion. The fascinating history of nuclear fusion shows man’s relentless efforts to first understand and then gain power over the source of energy that makes the stars shine. This history has also been dotted with some of the most brilliant, colorful and tragic figures in scientific history. Most importantly, fusion also demonstrates the dangers and pitfalls inherent in trying to seize nature’s greatest secrets from her.
In this engaging and informative history, Charles Seife tells us the story of trying to put the sun in a bottle, the singular personalities which permeated this history, the monumental mistakes made in understanding and harnessing this awesome source, and the wishful thinking that has pervaded the dream ever since its conception. Seife who has bachelor’s and master’s degrees in mathematics from Princeton and is now a journalism professor at NYU does a great job of clearly explaining the science behind fusion, and sprinkles his narrative with wit and gripping human drama.
These days fusion is mostly associated with hydrogen bombs that can obliterate entire cities and populations. And yet its story begins with a quest to understand one of the oldest and most profound questions that man has pondered; what makes the sun shine? Quite early on, it was quickly recognized that chemical rections couldn’t sustain the tremendous power of the sun for so long. After many decades of efforts, it was the great physicist Hans Bethe who finally cracked the secret of the stars’ luminous glow. Bethe found out a set of reactions catalysed by carbon that achieved the transformation of four hydrogen atoms into helium atoms. This central mechanism was soon shown to underlie the production of energy in all so-called main sequence stars like the sun.
It was with the entry of the United States into the Second World War however, that a more sinister use for nuclear fusion was envisioned by the volatile, brilliant Hungarian physicist Edward Teller, a dark character whose shadow looms large over the history of fusion and nuclear weapons. Teller proposed setting off a then still conceptual atomic bomb to generate the immense temperatures of tens of millions of degrees at the center of the sun that would ignite and hopefully propagate a fusion reaction in deuterium and tritium, isotopes of hydrogen that would be easier to fuse compared to hydrogen itself. Achieving fusion is an enormously difficult endeavor; one has to overcome the intense repulsive barrier between nuclei that keeps them from approaching one other. Only temperatures of tens of millions of degrees can get these nuclei hot enough to fuse. And yet as Seife explains, there is a fundamental paradox here; the very temperatures that can overcome the repulsive barrier between nuclei also blow them apart. It seems that in achieving nuclear fusion, we are constantly working against ourselves.
The history of the US and Soviet thermonuclear weapons program has been well documented in other sources. I have a summary in my last post. Seife succintly enumerates this history and narrates the development of genocidal megaton yield hydrogen bombs which are now part of almost every nuclear arsenal.
It is however in life and not in death that fusion promises mankind eternal glory. Efforts to attain this glory bear the stamp of the quintessential Faustian bargain for knowledge, where men gambled their careers and reputations, not to mention billions of government dollars, in trying to secure their place in history and free mankind of the burden of energy sources.
These efforts, while they taught us a lot about the workings of nuclei and electrons, have been riddled with tall claims and monumental failures. Seife recounts one program after another starting in the early 1950s that promised working fusion reactors in about twenty years. In Argentina and Britain, in Russia and the United States, claims about fusion regularly appeared and were hungrily lapped up by the popular press until a few months later, when the premature optimism came crashing down in the light of further investigations. In the first UN conference organized to discuss peaceful uses for atomic energy, Indian physicist Homi Bhabha talked about fusion becoming the practical solution to all our energy needs in three decades. And yet, effort after effort exposed fundamental problems in the system, hideously recalcitrant barriers that nature seemed to have erected to thwart us in our quest. The barriers still seem insurmountable.
On one hand, grandiose schemes using hydrogen bombs to excavate harbors, to carve out canals, to analyze moon dust and to solve almost every conceivable problem were imagined by Edward Teller and his followers. None of them worked, and all of them would produce dangerous radioactive fallout. On the other hand, early on scientists recognized a basic mechanism for taming fusion; by keeping fusing deuterium or tritium nuclei confined within a magnetic field in an extremely hot plasma of electrons and nuclei. The field of plasma physics emerged. This is the famous inertial confinement approach for harnessing fusion. This approach was developed and tested throughout the 50s and 60s. Some schemes looked as if they were working. Later it was found that not only were they producing less energy than what went in, but sometimes fusion was not even taking place and the neutrons that are a signature of the process were coming from elsewhere. The first condition, a net gain of energy, is called breakeven and is a fundamental condition for any energy-generating source to be satisfied. You have got to get more energy than what you put in. Ever since then, fusion has been achieved on smaller scales, but breakeven has never been attained.
Apart from inertially confined plasma fusion, Seife also describes the second major approach called laser fusion, which gradually arose as a competitor to plasma fusion in the 1970s. In this process, intense lasers shine on a small pellet of a deuterium or tritium compound from many directions. In the center of the pellet where unearthly temperatures and pressures are achieved, fusion takes place. This approach has been pursued in many grand schemes. One is called Shiva and involves 20 laser beams from 20 different directions squeezing a fusile pellet. The latest approach is called Nova which uses even more lasers. Both Shiva and Nova are closely guarded secrets. A computer program called LASNEX which helps their operation by simulating different fusion scenarios based on hundreds of variables and conditions is highly classified. Billions of dollars were spent on both these developments. And yet, as practical energy producing devices, both Shiva and Nova now look like dead ends.
Why is this the case? Why has almost every attempt to tame fusion failed? The answer has to do simply with the magnitude of the problem, and with how less we still understand nature. Both laser fusion and inertial fusion suffer from some fundamental and extremely complex problems that were discovered only when the experiments were underway. One problem has already been stated; the difficulty of confining such a hot plasma of particles. Another problem has to do with instability. As a hot plasma of deuterium and tritium circulates in an intense magnetic and electric field, local inescapable defects and asymmetries in the fields get quickly amplified and cause ‘kinks’ in the flow. The kinks gradually grow bigger like cracks in weak concrete and finally bring the entire structure down, quickly dissipating the plasma and halting fusion. While impressive progress has been made in controlling the fine parameters of the magnetic and electric fields, the problem still persists because of its basic nature. The other problem was that the electrons were getting heated much faster than the nuclei so that the nuclei- the real target- would stay relatively cool. A third serious problem was the initiation of Rayleigh-Taylor instabilities, little whirlpools and tongues that develop when a less-dense material presses against a more-dense material. Interestingly it’s Rayleigh-Taylor instabilities and not gravity that is the reason why water from an overturned glass escapes. Rayleigh-Taylor instabilities developed in laser fusion when less dense photos of light tried to compress a denser pellet of deuterium. These instabilities quickly destroyed the fine balance of the fusion process. The process is exquisitely sensitive to the finest of defects, like nanoscopic dimples of the surface of the pellet. Solving this problem requires the best of physics and engineering.
All these problem still plague fusion, and billions of dollars, thousands of brilliant scientists and hundreds of innovative ideas later, fusion still remains a dream. It has been achieved many times, neutrons have been observed, but breakeven still is a land that’s far, far away.
But scientists don’t give up. And while legitimate scientific efforts on the two ‘hot fusion’ approaches continue, there have been cases where some scientists believed they were observing fusion a tad too easily under circumstances that were too good to believe. These events saw their careers being destroyed and the promise of fusion again mangled. The events refer to the infamous cases of ‘cold fusion’ which constitute the last and most important part of Seife’s book. Seife weaves a riveting tale around these events, partly since he was a participant in one of the debacles.
The story of Pons and Fleischmann’s 1989 cold fusion disaster at the University of Utah is well known. The two took the unusual step of announcing their results in a press conference before getting them peer-reviewed and published. Later their experiments were shown to be essentially irreproducible. Seife recounts in details the developments that gradually cast a black cloud over this claim. One of the characters in this story is Steve Jones, a physicist who has recently gained notoriety for becoming a 9/11 denier.
But I was particularly interested in the next story since I had actually met and talked to one of the characters in the cold fusion catastrophe many years ago. Rusi Taleyarkhan, an Indian scientist, happened to come to our University in 2002 to give a talk. Just a few months before, he and his colleagues had published a paper in the prestigious journal Science, which if true would herald one of the greatest breakthroughs in scientific history. Taleyarkhan and his group claimed to have observed fusion in the most disarmingly simple experiment. They had taken a solution of deuterated acetone (acetone with its hydrogen atoms replaced by deuterium) and had bombarded it with neutrons that caused giant bubbles to form in the solution. They had then exposed the solution to intense acoustic waves, thus causing the bubbles to violently collapse. The phenomenon was well known and is called sonoluminescence, a name alluding to the light that is often given off because of these violent collapses. But what was Taleyarkhan’s claim? That the immense pressures and temperatures generated at the center of the bubbles caused nuclear fusion of the deuterium in the acetone, essentially in a tabletop apparatus at room temperature. Why acetone? This was the question I asked Taleyarkhan when I met him in 2002. He did not know, and he sounded sincere about it.
But this was before the storm was unleashed and the controversy erupted. In this case unlike the previous one, the work had been peer reviewed by one of the most famous and stringent journals in the world. But curiously, further investigation by Seife and others revealed that the paper had been published by Science’s editor in spite of objections by the reviewers. This was highly unusual to say the least. What was more disturbing was that concomitant experiments done at Oak Ridge National Laboratory, Taleyarkhan’s home turf at the time, revealed negative results. Once the results were announced, researchers across the world including some at prestigious institutions scurried around to repeat the experiments using more sophisticated detectors and apparatus. Fusion produces very signature neutrons of specific energy. The more sophisticated apparatus failed to detect these neutrons. In the earlier cold fusion debacle, there had been doubt about the energy peaks of the neutrons. Similar doubts started surfacing in this case. Questions were also raised about the possibly shoddy nature of the experiments, including the absence of control experiments. Later Taleyarkhan moved to Purdue, and Purdue initially defended the experiments. But the story remained murky. Some ‘independently’ published later articles turned out to not be so independent after all. Gradually, just like it had previously, the great edifice turned into a crumbling structure and came down. As a reporter for Science then, Seife personally covered these events. Purdue reinvestigated the matter and as of 2008, Taleyarkhan is forbidden from working as a regular PhD. student advisor at Purdue. Even though he was not convicted of deliberate fraud, his reputation has come crashing down.
This then is the history of fusion, episode after episode of wishful thinking to solve the biggest problem in the history of mankind. A fusion reactor may someday be possible, but nothing until now suggests that it would be so. It’s hard to trust a technology if it has consistently failed to deliever on its promise time after time. After all this, even the mention of the statement ‘cheap, abundant and universal energy’ should raise our eyebrows. In the afterword, Seife discusses the rather harsh nature of the scientific process where skepticism is everyone’s best friend and results are intensely vetted, a fact that’s necessary though to keep science and scientists in line. Fusion seems to be one of those endeavors where tall claims have been more consistently proclaimed than perhaps in any other branch of science. This has been undoubtedly so because of the earth-shattering implications of a true practical nuclear fusion reactor and the fame that it will bring its inventor. Even with such a reactor, our problems may not be over. First of all fusion is not as clean as it is made out to be; copious amounts of neutrons, gamma rays and other forms of radiation are released in the process. Secondly, even with mass production fusion reactors may cost no less than tens of millions of dollars. Even as Seife writes, the world’s economies have pooled their resources together into ITER, an international thermonuclear project that promises to be the biggest of its kind until now. The United States did not support the project earlier and it had to be scaled back. Now the US seems to be contributing again to a more modest version of the vision. As with other matters, the politics of fusions seems to be even more elusive than the science of fusion. Gratifyingly, Seife thinks that our best current bet to solve the energy problem is nuclear fission. It emits no carbon dioxide, provides the biggest bang for your buck, and most importantly unlike fusion is already here. Compared to the will-o-wisps of fusion, the very real strands of fission can solve many of our real problems. Ironically, controlled fusion is still a distant dream while very tangible thermonuclear bombs sit securely in the arsenals of so many nations.
In the end, one factor which Seife should have appreciated more in my opinion is the immense knowledge that has been gained from so many years of fusion research. That is one of the great virtues of science, that even failed endeavors can contribute key insights into the workings of nature and uncover new principles. Fusion might be wishful thinking, a grandiose and tragic scheme to put the sun in a bottle, but science always wins. And if not for anything else, for that we should always be grateful.