Current Commentary: Energy from Nuclear Fusion – Realities, Prospects and Fantasies?

When I was about 10, I recall hearing that nuclear fusion power would become a reality "in about thirty years". The estimate has increased steadily since then, and now, forty odd years on, we hear that fusion power will come on-stream "in about fifty years". So, what is the real likelihood of fusion-based power stations coming to our aid in averting the imminent energy crisis? Getting two nuclei to fuse is not easy, since both carry a positive charge and hence their natural propensity is to repel one another. Therefore, a lot of energy is required to force them together so that they can fuse. To achieve this, suitable conditions of extremely high temperature, comparable to those found in stars, must be met. A specific temperature must be reached in order for particular nuclei to fuse with one another. This is termed the "critical ignition temperature", and is around 400 million degrees centigrade for two deuterium nuclei to fuse, while a more modest 100 million degrees is sufficient for a deuterium nucleus to fuse with a tritium nucleus. For this reason, it is deuterium-tritium fusion that is most sought after, since it should be most easily achieved and sustained.

One disadvantage of tritium is that it is radioactive and decays with a half-life of about 12 years, and consequently, it exists naturally in only negligible amounts. However, tritium may be "bred" from lithium using neutrons produced in an initial deuterium-tritium fusion. Ideally, the process would become self-sustaining, with lithium fuel being burned via conversion to tritium, which then fuses with deuterium, releasing more neutrons. While not unlimited, there are sufficient known resources of lithium to fire a global fusion programme for about a thousand years, mindful that there are many other uses for lithium, ranging for various types of battery to medication for schizophrenics. The supply would be effectively limitless if lithium could be extracted from the oceans.

In a working scenario, some of the energy produced by fusion would be required to maintain the high temperature of the fuel such that the fusion process becomes continuous. At the temperature of around 100 - 300 million degrees, the deuterium/lithium/tritium mixture will exist in the form of a plasma, in which are nuclei are naked (having lost their initial atomic electron clouds) and are hence exposed to fuse with one another.

The main difficulty which bedevils maintaining a working fusion reactor which might be used to fire a power station is containing the plasma, a process usually referred to as "confinement" and the process overall as "magnetic confinement fusion" (MCF). Essentially, the plasma is confined in a magnetic bottle, since its component charged nuclei and electrons tend to follow the field of magnetic force, which can be so arranged that the lines of force occupy a prescribed region and are thus centralised to a particular volume. However, the plasma is a "complex" system that readily becomes unstable and leaks away. Unlike a star, the plasma is highly rarefied (a low pressure gas), so that the proton-proton cycle that powers the sun could not be thus achieved on earth, as it is only the intensely high density of nuclei in the sun's core that allows the process to occur sustainably, and that the plasma is contained within its own gravitational mass, and isolated within the cold vacuum of space.

In June 2005, the EU, France, Japan, South Korea, China and the U.S. agreed to spend $12 billion to build an experimental fusion apparatus (called ITER)1 by 2014. It is planned that ITER will function as a research instrument for the following 20 years, and the knowledge gained will provide the basis for building a more advanced research machine. After another 30 years, if all goes well, the first commercial fusion powered electricity might come on-stream.

The Joint European Torus (JET)
I heard Dr Chris Warrick from the Culham Centre for Fusion Energy2 based near Abingdon in Oxfordshire, which hosts both the MAST (Mega Amp Spherical Tokamak) and the better known JET (Joint European Torus) experiments, speak on this topic at a Cafe' Scientifique3 meeting in Reading recently. In the audience was a veteran engineer/physicist who had worked on the pioneering ZETA4 experiment in the late 1950s, from which neutrons were detected leading to what proved later to be false claims that fusion had occurred, their true source being different versions of the same instability processes that had beset earlier machines.

Nonetheless, his comment was salient: "In the late 50s, we were told that fusion power was 20 years away and now, 50-odd years later it is maybe 60 years away." Indeed, JET has yet to produce a positive ratio of output power/input energy, and instability of the plasma is still a problem. Dr Warrick explained that while much of the plasma physics is now sorted-out, minor aberrations in the magnetic field allow some of the plasma to leak out, and if it touches the far colder walls of the confinement chamber, it simply "dies". In JET it is fusion of nuclei of the two hydrogen isotopes, deuterium and tritium that is being undertaken, a process that as noted earlier, requires a "temperature" of 100 million degrees.

I say "temperature" because the plasma is a rarified (very low pressure) gas, and hence the collisions between particles are not sufficiently rapid that the term means the same distribution of energy as occurs under conditions of thermal equilibrium. It is much the same as the temperatures that may be quoted for molecules in the atmospheric region known as the thermosphere which lies some 80 kilometers above the surface of the Earth. Here too, the atmosphere is highly rarified and thus derived temperatures refer to translational motion of molecules and are more usefully expressed as velocities. However expressed, at 100 million degrees centigrade, the nuclei of tritium and deuterium have sufficient translational velocity (have enough energy) that they can overcome the mutual repulsion arising from their positive charges and come close enough that they are drawn together by attractive nuclear forces and fuse, releasing vast amounts of energy in the process.

JET is not a small device, at 18 metres high, but bigger machines will be necessary before the technology is likely to give out more energy than it consumes. Despite the considerable volume of the chamber, it contains perhaps only one hundredth of a gram of gas, hence its very low pressure. There is another matter and that is how long the plasma and hence energy emission can be sustained. Presently it is fractions of a second but a serious "power station" would need to run for some hours. There is also the problem of getting useful energy from the plasma to convert into electricity even if the aforementioned and considerable problems can be overcome and a sustainable, large-scale plasma maintained.

The plan is to surround the chamber with a "blanket" of lithium-containing material with pipes running through it and some heat-exchanger fluid passing through them. The heated fluid would then pass on its heat to water and drive a steam-turbine, in the time-honoured fashion used for fossil fuel fired and nuclear power plants. Now my understanding is that this would not be lithium metal but some oxide material. The heat would be delivered in the form of very high energy neutrons that would be slowed-down as they encounter lithium nuclei on passing through the blanket. In principle this is a very neat trick, since absorption of a neutron by a lithium nucleus converts it to tritium, which could be fed back into the plasma as a fuel. However produced, either separately or in the blanket, lithium is the ultimate fuel source, not tritium per se. Deuterium does exist in nature but only to the extent of one part in about two thousand of ordinary hydrogen (protium) and hence the energy costs of its separation are not inconsiderable.

The neutron flux produced by the plasma is very high, and to enhance the overall breeding efficiency of lithium to tritium the reactor would be surrounded with a "lithium" blanket about three feet thick. The intense neutron flux will render the material used to construct the reactor highly radioactive, to the extent that it would not be feasible for operators to enter its vicinity for routine maintenance. The radioactive material will need to be disposed of similarly to the requirements for nuclear waste generated by nuclear fission, and hence fusion is not as "clean" as is often claimed. Exposure to radiation of many potential materials necessary to make the reactor, blanket, and other components such as the heat-exchanger pipes would render them brittle, and so compromise their structural integrity. There is also the possibility that the lithium blanket around the reactor might be replaced by uranium, so enabling the option of breeding plutonium for use in nuclear weapons.

Providing a fairly intense magnetic field to confine the plasma (maybe 4 Tesla - similar to that in a hospital MRI scanner) needs power (dc not ac as switching the polarity of the field would cause the plasma to collapse) and large power-supply units containing a lot of metals including rare earths which are mined and processed using fossil fuels. The issue of rare earths is troublesome already, and whether enough of them can be recovered to meet existing planned wind and electric car projects is debatable, let alone that additional pressure should be placed upon an already fragile resource to build a first generation of fusion power stations.

World supplies of lithium are also already stressed, and hence getting enough of it not only to make blankets for fusion reactors and tritium production but also for the millions-scale fleet of electric vehicles needed to divert our transportation energy demand away from oil is probably a bridge too far, unless we try getting it from seawater, which takes far more energy than mining lithium minerals. The engineering requirements too will be formidable, however, most likely forcing the need to confront problems as yet unknown, and even according to the most favourable predictions of the experts, fusion power is still 60 years away, if it will arrive at all. Given that the energy crisis will hit hard long before then, I suggest we look to more immediate solutions, mainly in terms of energy efficiency, for which there is ample scope.

UK and US join forces on laser-fusion energy5
The UK company AWE and the Rutherford Appleton Laboratory have joined-forces with the US-based National Ignition Facility (NIF) to help provide energy using Inertial Confinement Fusion (ICF), in which a pellet of fuel is heated using powerful lasers. Since the late 1950s, UK scientists have been attempting to achieve the fusion of hydrogen nuclei (tritium and deuterium) using magnetic confinement (MCF). The UK-based Joint European Torus (JET) is the largest such facility in the world and may be regarded as a prototype for the International Thermonuclear Experimental Reactor (ITER) based in France. So far, the "breakeven point" has not been reached, and the energy consumed by the plasma has yet to yield more energy than it takes to maintain it; moreover, there are problems of instability as already alluded to.

An alternative is Inertial confinement fusion (ICF), in which fusion of nuclei is initiated by heating and compressing a fuel target, typically in the form of a pellet containing deuterium and tritium contained in a device called a hohlraum (hollow space or cavity) using an extremely powerful laser. Energy is delivered from the laser to the inner surface of the hohlraum which produces high-energy X-rays. The impingement of these X-rays on the target causes its outer layer to explode, and by a Newtonian counter reaction, drives the inner substance of the target inwards, compressing it massively. Shock-waves are also produced that travel inward through the target.

If the shock-waves are intense enough, the fuel at the target centre is heated and compressed to the extent that nuclear fusion can occur. The energy released by the fusion reactions then heats the surrounding fuel, within which atomic nuclei may further begin to fuse. In comparison with "breakeven" in MCF, in ICF a state of "ignition" is sought, in which a self-sustaining chain-reaction is attained that consumes a significant portion of the fuel. The fuel pellets typically contain around 10 milligrams of fuel, and if all of that were consumed it would release an energy equivalent to that from burning a barrel of oil. In reality, only a small proportion of the fuel is "burned". That said, "ignition" would yield far more energy than the breakeven point value.

At the NIF it is hoped to have ignition within a couple of years, or far sooner than the carrot before the donkey "50 years away" for MCF, although there is much to be done yet. A single shot from the world's most powerful laser at NIF is reported to have released "a million billion neutrons" and for a tiny fraction of a second produced more power than was being consumed in the entire world, although to achieve ignition this would need to be increased a thousand-fold.

A real breakthrough, no doubt, but as with MCF, how long before this technology can be fabricated into actual power stations? There are many non-trivial ancillary challenges too, especially the secondary procedure of actually getting the energy out of the reactor into a useful form, i.e. heat to drive steam-turbines as with all other kinds of thermal power stations, to generate electricity. This is very complex and untested technology compared, say, to coal- and gas-fired or nuclear power plants. Actual fusion power is still at best many decades away and the concept should not be thrown as a red-herring that the world's impending energy crisis has been abated.

Most immediately, what fusion in any of its manifestations does not address is the problem of providing liquid fuels as conventional supplies of oil and gas decline, and it is this which is the greatest and most pressing matter to be dealt with, against a backdrop of mere years not a luxury of decades. There are more than one billion vehicles on the World's roads powered by liquid fuels refined from crude oil, and electrically powered versions of them will not supplant their number significantly in the immediate future.

"Cold fusion" proven?
I remember well the phenomenon of "cold fusion" (or fusion in a test tube) as it was dubbed.6 This was back in 1989 when Professors Stanley Pons and Martin Fleischman claimed that they could extract 40% more energy in the form of heat than they had input in the form of electricity into an electrochemical cell containing deuterium oxide ("heavy water"). They proposed the deuterium nuclei had undergone a nuclear fusion. The potential implications of this were staggering: that rather than trying to mimic the massively high temperature conditions of some hundred million degrees or so as are necessary to overcome the strong Coulombic forces that tend to keep two positively charged nuclei apart, as in "hot" plasma-fusion, it was feasible to somehow overcome this barrier such that the process could occur at room temperature.

Pons and Fleischman became largely dismissed as charlatans when many other research groups around the world found themselves unable to reproduce their results and confirm their claims, which were accordingly dismissed as unfounded. However, note the comment below to the effect that the phenomenon has since been confirmed in many highly credible laboratories around the world. I remember there were some really quite bizarre effects found by other workers - for example, one young man was killed when a cold-fusion cell exploded while he was trying to demonstrate the phenomenon of "fusion in a test-tube" as the popular press described it.7 So, something real was happening, fusion or not. A senior scientist and champion of cold-fusion, Dr Eugene Mallove, was murdered during the furore, which incited a number of conspiracy theories at the time.8

The matter never entirely went away and I recall reading an article either in The Guardian or New Scientist (or both) to the effect that a scientist in the U.S. had claimed to have demonstrated fusion when he exposed hexadeuteroacetone (that's C3D6O as opposed to the more common C3H6O) to ultrasound. He was vilified by the scientific community, as I recall and its dogma that cold fusion did not exist and could not as there is no theory to explain it.9 However, a professor in Japan has apparently demonstrated that if deuterium gas is passed into a reactor containing composite palladium-zirconium oxide (Pd-ZrO2) nanoparticles, Helium-4 is produced (a sure sign of fusion?), the temperature of the reactor rises and its centre remains warm for 50 hours.10

If this is true it is absolutely fascinating and perhaps some accepted scientific laws will need to be substantially modified, as has been said. However, from a practical point of view, that of dealing with the energy crunch, even if cold fusion is a reality, have we found our salvation? I don't think so, frankly. I have not seen any figures for how much Pd and deuterium gas are used to run this cell and how much excess heat is produced. However, I have yet to be convinced that the energy needed to produce deuterium gas (by the electrolysis of deuterium oxide - "heavy water") and to make enough heavy water in the first place to feed the electrolysis units, will be offset by the final thermal output of the "fusion" reactors. Then there is the matter of availability of palladium metal, the energy for its fabrication into the composite nanoparticles and so on, and how would the heat energy be extracted usefully, say to heat buildings or drive electricity turbines? The problem of energy extraction is even worse for "hot" fusion, from a plasma that even if it can be sustained, would produce ultra-high energy neutrons that no known materials are yet able to withstand, from which to extract thermal energy.

Energy-Catalyzer11
The issue of "cold fusion" has resurfaced in the guise of the Energy Catalyzer. This is also referred to as E-Cat and is claimed as a Low-Energy Nuclear Reaction (LENR) heat source, and is the creation of Andrea Rossi who is an inventor. Much has been written on this subject in the popular press, and the matter has been summarized in a useful wikipedia article11, containing original references which I have verified as being accurate. A patent was approved in Italy on April 6, 2011 by Rossi and physicist Sergio Focardi which designates the E-Cat as "process and equipment to obtain exothermal reactions, in particular from nickel and hydrogen". Now this is where it gets interesting: Rossi and Focardi say the device works by infusing heated hydrogen into nickel, transmuting it into copper and producing heat. However, an international patent application has received an unfavourable international preliminary report on patentability because it seemed to "offend against the generally accepted laws of physics and established theories" and it is concluded that the application is lacking in either experimental evidence or a firm theoretical basis that accords with current scientific understanding. The device has been demonstrated to a number of invited audiences, but it has not been independently verified. Writing on Forbes, Mark Gibbs has concluded that: "until a verifiably objective analysis is conducted by an independent third party that confirms the results match the claims, there's no real news".

Actual demonstrations of the E-Cat
Two such demonstrations were given in January and February and others as summarised in the list below. Reporting on the January demonstration, Benjamin Radford, an analyst on the Discovery Channel wrote: "If this all sounds fishy to you, it should," and that "In many ways cold fusion is similar to perpetual motion machines. The principles defy the laws of physics, but that doesn't stop people from periodically claiming to have invented or discovered one."

On the 29th of March, 2011, two Swedish physicists, Hanno Essén and Sven Kullander witnessed a test of a smaller version of the Energy Catalyzer, which ran for six hours. It was claimed that a net power output of 4.4 kW had been achieved with a total energy output of about 25 kWh. An analysis of the unused powder showed it to be pure nickel while that taken from the reactor (reported as used for 2.5 months) contained 10 percent copper and 11 percent iron. Kullander said that the presence of copper is "a proof that nuclear reactions took place in the process". However, other researchers, Ekström and Aleklett concluded that since that copper had the same isotopic ratios as natural copper, and that the proportion of it is too high, it most likely arises from contamination. Significantly, the formation of iron is not mentioned at all in the patent. Essen and Kullander were guarded in their evaluation, writing that: "Since we do not have access to the internal design of the central fuel container... we can only make very general comments." Essén later stated "I am still very uncertain about this."

Potential commercial exploitation
A Greek company, Defkalion, had intended to build a heating plant based on the Energy Catalyzer, but the deal fell through, although the company has announced that they plan to fabricate a similar device. Rossi made a deal in May 2011 with AmpEnergo in Ohio, to receive royalties on sales of licenses and products built on the Energy Catalyzer throughout North and South America. It was reported that an engineer Domenico Fioravanti had tested a1 MW power plant based on the Energy Catalyzer on the 28th of October, 2011, although the name of the client was not disclosed. Fioravanti claimed that over a period of 5.5 hours the plant produced 2,635 kWh, which corresponds to an average power output of 479 kW. Independent observers were not permitted, but also the plant remained connected to a power supply throughout the test, purportedly to run the fans and the water pumps. It is reported that the customer took possession of the plant afterwards. Rossi claims to have orders for thirteen more 1 MW units which are on sale for $2 million each, in addition to the unnamed customer who has the one from the 28th of October test. Focus, a popular science magazine in Italy, has stated that 12 additional units are to be provided to the same, undisclosed customer. Rossi commented: "We are building a 13 MW thermal plant, made of 13 plants such as the one you saw on October 28th: but it's a military research and I can't reveal any further detail, not the name, nor the place, nor the nationality of the customer".

This is all quite fascinating and further reports are awaited with interest. Whatever the outcome, the problem of peak oil and the attendant liquid fuels crisis remains.

References.
(1) http://www.iter.org/
(2) http://www.ccfe.ac.uk/
(3) http://www.cafescientifique.org/
(4) http://en.wikipedia.org/wiki/ZETA_%28fusion_reactor%29
(5) http://www.bbc.co.uk/news/science-environment-14842720
(6) http://en.wikipedia.org/wiki/Cold_fusion
(7) http://www.science-frontiers.com/sf080/sf080u19.htm
(8) http://www.wanttoknow.info/eugenemallove
(9) http://en.wikipedia.org/wiki/Bubble_fusion
(10) http://www.rexresearch.com/arata/arata.htm
(11) http://en.wikipedia.org/wiki/Energy_Catalyzer

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Future Energies

By Chris Rhodes

Current Commentary: Energy from Nuclear Fusion – Realities, Prospects and Fantasies?

By Chris Rhodes

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