Is Cold Fusion Possible?

Michael J. Schaffer, a senior scientist at one of the major U.S. fusion research laboratories (his employer has requested not to be identified), has provided this historical overview, along with a rather moderate assessment current status of cold fusion:

"Because cold fusion is still an unresolved and controversial subject that generates strong opinions and passionate debate among scientists, I begin by stating up front that I am a mainstream plasma physicist researching fusion energy. I also read many of the papers published on cold fusion, however. I attended the last three International Conferences on Cold Fusion, and I myself ran two sets of cold fusion experiments, both with no clear evidence of excess power release. Overall, I consider myself to be a fairly neutral observer.

"To understand the controversy, it helps to know some basic facts about fusion. Fusion is a nuclear reaction wherein two smaller nuclei join (fuse) to form a new, larger nucleus. When that large nucleus is unstable, it quickly breaks apart and releases energy. The big difficulty is that because the initial nuclei are all positively charged, they are strongly repelled as they approach one another. Therefore, only nuclei having a high kinetic energy approach closely enough to fuse. High-speed nuclei can be made on the earth either by particle accelerators or by extremely high temperatures — on the order of 50 million degrees Celsius or more. In controlled 'magnetic' fusion energy experiments, such as tokamaks and others, a magnetically confined plasma is heated by electromagnetic waves or neutral particle beams. In 'inertial' fusion energy experiments, tiny pellets are compressed and heated by powerful pulsed laser or ion beams.

"Cold fusion claims to release measurable energy from fusion reactions at or near room temperature when deuterium is dissolved in a solid, usually palladium metal. The idea, which has its roots in research going back to the 1920s, is that hydrogen and its isotopes can dissolve to such high concentrations in certain solids that the hydrogen nuclei approach closer to one another than even in solid hydrogen. Furthermore, negative electrical charges from the electrons of the solid host partly cancel the repulsion between the nuclei. Early experiments did not detect any signs of fusion, however. Furthermore, modern theoretical calculations show that the proposed effects, while real, are much too small to produce detectable rates of fusion.

"Electrochemists Martin Fleischmann and Stanley Pons decided to revisit room-temperature fusion. Their technique is to pass current through an electrolytic cell consisting of a palladium (Pd) cathode, platinum (Pt) anode and LiOD (a compound of lithium, oxygen and deuterium, or heavy hydrogen) electrolyte in heavy water (water containing deuterium in place of the ordinary hydrogen). The cathodic reaction liberates unbound atoms of deuterium (D), which enter palladium much more rapidly than do deuterium molecules. Under proper conditions, the concentration can build up to 0.9 or more deuterium atoms per palladium atom, at which point the loss of deuterium balances its rate of implantation. Pons and Fleischmann's cells were part of a calorimeter (heat-measuring device), whose temperature rise on a few occasions indicated on the order of 10 percent excess power, that is, about 10 percent more power leaving the cell than electrical power used to run it. Pons and Fleischmann announced their results at a now famous news conference on March 23, 1989. They also thought they had detected gamma radiation characteristic of neutrons passing through water, but these results later had to be retracted.

"There was an immediate rush to reproduce the Pons and Fleischmann experiments. A few experimenters reported success, many others failure. Even those who reported success had difficulty reproducing their results. Furthermore, no one was seeing the expected fusion products. The three known D + D reactions are:

D + D — > H + T (two deuterium nuclei yield a hydrogen nucleus and tritium, a heavy hydrogen isotope containing two neutrons) or

D + D — -> n + 3He (yielding a neutron and helium 3, a light isotope of helium), or

D + D — -> 4He + gamma (yielding normal helium 4 and a gamma ray).

"The first two reactions are equally probable, and if one watt of nuclear power were produced, the neutron and tritium production would be easy to measure. But they could not be detected; if they were present at all, it was only at an extremely low level. The third D + D reaction normally proceeds much more slowly than the first two. Some experiments eventually did report helium 4 production, although great care must be used to avoid contamination by trace amounts of helium normally present in the air. This led many cold fusion researchers to postulate that somehow the third fusion reaction was catalyzed in the palladium. Moreover, it was necessary to postulate the suppression of the gamma radiation, which was never observed. There is no widely accepted theory that might explain such effects, however. Therefore, most of the scientific community concluded that the 'Pons and Fleischmann effect' was experimental error.

“Production of such heavy nuclei is so unexpected from our present understanding of low-energy nuclear reactions, that extraordinary experimental proof will be needed to convince the scientific community. All available analytical techniques will have to be applied and the results reproduced.

“So, what is the current scientific thinking on cold fusion? Frankly, most scientists have not followed the field since the disenchantment of 1989 and 1990. They typically still dismiss cold fusion as experimental error. Even so, given the extraordinary nature of the claimed cold fusion results, it will take extraordinarily high quality, conclusive data to convince most scientists, unless a compelling theoretical explanation is found first.”

Robert F. Heeter of the Princeton Plasma Physics Laboratory is the author of the "Conventional Fusion FAQ" (internet newsgroup sci.physics.fusion) and webmaster of the Fusion Energy Educational Web Site. He responds:

"The 'cold fusion' phenomenon, in which the law of conservation of energy is apparently violated when electricity and heat are applied to special systems involving hydrogen isotopes (in water or gaseous form) and particular metals (notably palladium and nickel), defies conventional scientific explanation. All new theories explaining 'cold fusion' effects require large revisions in existing physical theories (one might call them 'miracles'). Scientific skepticism requires that unless the experimental evidence justifies belief in these miracles, we must conclude that experimental errors are being misinterpreted as positive results.

"One would normally expect that about half of all careful energy-balance measurements would indicate excess energy, and about half would show an energy deficit, because experimental error spreads the results around the expected outcome. A preponderance of results showing excess energy might indicate something new. But if one is deliberately searching for excess energy, then one may be able to 'optimize' a complicated system to yield large amounts of apparent excess energy by fooling the measurement apparatus somehow. Whether a given excess-heat result represents a physical 'miracle' or an experimental error is very difficult to determine if the amount of excess heat is small or if the fraction of excess power to total input power is low — as is the case in reports of cold fusion.

"If indeed miracles are occurring in 'cold fusion,' they are not fusion reactions involving hydrogen isotopes. The inevitable signatures of fusion reactions — in which atomic nuclei combine, thereby releasing a large amount of energy — are combinations of energetic particles (neutrons, positrons and ions) and gamma rays. The direct conversion of fusion energy into heat is not possible because of energy and momentum conservation and the laws of special relativity. Energetic particles and their secondary effects should be easily detectable if the claimed levels of excess power were the result of fusion reactions. But measurements of these fusion signatures have been either nonexistent, inaccurate or orders of magnitude too low. Attempts to explain 'cold fusion' as something other than nuclear fusion require similar miracles supported by similarly weak evidence.

"The case for experimental error is supported by the unreliability and lack of independent replication of key results. Furthermore, the nature of the complex systems and measurement equipment involved in 'cold fusion' research is beyond the range of expertise of most researchers involved.

"'Cold fusion' resembles the alchemy of the middle ages. The search for truth suffers now, in the quest to convert hydrogen into energy, just as it did 1,000 years ago in the quest to convert lead into gold. The allure of fame and wealth and the natural desire to believe in good news have been corrupting influences on scientific skepticism. So researchers working outside their main areas of professional expertise are even more likely to misinterpret experimental errors as positive results. And it is hard not to be skeptical about a revolutionary new discovery that would so conveniently have such tremendous and immediate economic value.

"I entered graduate school wishing to help solve our impending energy crisis, so I studied 'cold fusion' carefully and with an open mind in order to make a wise career choice. I learned that the critical positive results have not been reliably and independently reproduced, and many careful and thorough studies have yielded negative conclusions, although often these unexciting results went unpublished. It is probably impossible to prove that 'cold fusion' is nothing more than the result of misinterpreted experimental errors, but the probability of it being otherwise is low.

"Efforts to disprove 'cold fusion' remind me of the O. J. Simpson case — the evidence is clear enough that most people have firm beliefs, yet truly conclusive proof is elusive. But science is not law: when one puts a scientific theory on trial in an experiment, the existing theory is presumed guilty of explaining your observations until it is proven innocent by showing that only a new theory will fit the evidence properly. Large changes in well-established theories require a stronger body of evidence. 'Cold fusion,' if true, requires radical changes in our understanding of energy and matter, but even after eight years of intense effort costing tens of millions of dollars, the evidence remains weak — although apparently the cold fusion conferences in Hawaii, Monte Carlo and elsewhere have been quite lavish. I now doubt 'cold fusion' is really an easy alchemical solution to the world's energy needs.”

— Originally published: Scientific American Online, October 21, 1999