Nuclear fusion is a process in which two elements are fused into one, a process that releases energy from the nucleus of an atom, hence the name “nuclear energy.” It contrasts with nuclear fission, a process that man has used for 60 years to produce electricity. In fission, a large atom is split into smaller atoms. In fusion, two small atoms are fused into a larger atom. Both processes release energy. Pound for pound, fission produces 8,000 times as much energy as burning fossil fuels. Fusion produces seven times more energy than fission, or 56,000 times as much energy as fossil fuels.
Advantages and Disadvantages of Fusion
Advantages: Fusion creates much more energy than fission, it doesn’t produce radioactive waste, and fuel is abundant and cheap.
Disadvantages: The sun is powered by fusion occurring in its core where pressures and temperatures are enormous. We can’t duplicate the pressure in the center of the sun, so we have to compensate by creating much higher temperatures to achieve fusion on Earth – around 150 million degrees Celsius. By comparison, the temperature at the core of the sun is a balmy 27 million degrees Celsius. At 150 million degrees, electrons separate from the nuclei of atoms, creating a form of matter called plasma. Plasma is highly energetic and hard to contain. It is also too hot to touch a containment vessel. So the three problems for fusion are achieving the incredibly high temperatures required, suspending the plasma in some non-physical containment field, and containing the plasma long enough to produce a sustained fusion reaction.
There is also a problem caused by the choice of fuel that the industry has opted for. Where the sun uses ordinary hydrogen, on Earth (once again because of the lower pressure) we must use hydrogen isotopes (deuterium and tritium) that are 24 orders of magnitude (1 x 1024) more reactive than ordinary hydrogen. This compensates for the lower particle density due to the low pressure. The problem this creates is that the isotopes have neutrons, and so the fusion reaction creates energetic streams of neutrons that create four problems: radiation damage to the structures, radioactive waste, the need for biological shielding, and the potential for the production of weapons-grade plutonium 239.
In addition, fusion reactors would share some of the other serious problems that plague fission reactors, including tritium release, daunting coolant demands, and high operating costs. There will also be additional drawbacks that are unique to fusion devices: the use of a fuel (tritium) that is not found in nature and must be replenished by the reactor itself; and the need to use immense amounts of electricity to heat and contain the fuel, resulting in a large power drain that drastically reduces the electric power available for sale.
A Fateful Design Decision
The idea of using nuclear fusion to create power began in the 1930’s. In the 1940’s, researchers began to look for ways to initiate and control fusion reactions. Starting in the 1960’s, after the invention of the laser, researchers sought to heat fuels with a laser so suddenly that the plasma would not have time to escape before it was burned in the fusion reaction. It would be trapped by its own inertia. This newer approach was thus named ”inertial confinement”.
During this period, scientists realized that the key problem for controlled fusion was the tendency of plasma to develop instabilities that caused it to escape from the magnetic confinement. By the end of the 1960’s there were many different fusion devices, and no one knew which approach would actually lead to practical fusion power. But in the mid-1970’s administrators in the United States decided to focus all magnetic confinement work on a single device, the tokamak, which had been invented in the Soviet Union. In part, this decision was due to the effort to portray fusion as a short-term solution to the oil crisis of the early 1970’s, requiring only engineering development. In fact, fusion was then, and still is, a research project, investigating which route to fusion power is best.
The largest fusion project in the world is the International Thermonuclear Experimental Reactor. It is a multinational installation being built in Provence in southern France. Work was started in 2013. The design is a magnetic confinement tokamak and the fuel is deuterium-tritium, so all the drawbacks previously mentioned apply.
Everything about ITER is gargantuan. It is being built on a 445-acre site. The base for the facility is a five-foot thick concrete slab measuring 1,300 by 3,300 feet supported by 493 anti-seismic columns. It required 883,000 cubic feet of concrete weighing over 13 million pounds and contains over 8 million tons of reinforcing steel. The base of the tokamak complex which sits on top of this foundation, is also 5 feet thick, required 50,000 cubic feet of concrete, and weighs 7.5 million pounds. The tokamak itself weighs 16 million pounds. The tokamak and associated equipment will weigh 28,000 pounds.
ITER will not produce electricity, which avoids a major challenge – that of figuring out how to convert a stream of high energy neutrons to electricity. It is supposed to produce the equivalent of 500 MW of energy. ITER has falsely advertised that this will be ten times the energy (50 MW) that will be required to produce it. But 50 MW is only what is required to heat the fuel. What this figure doesn’t include is the electricity that is required to run the rest of the machinery (superconducting magnets, coolant system, and all the other support equipment). When this is included, and when a conservative conversion factor is used to calculate electrical energy from thermal energy, ITER will only produce 71% of the energy it consumes.
Robert L. Hirsch, former director of the U.S. fusion energy program in the 1970’s, believes that narrowing funding to a single device (the tokamak) was a major mistake. He has noted that as early as 1994, studies indicated that the tokamak would be 60 times as massive as a fission reactor core of the same power, and thus far more expensive. Given the fundamental problems of huge size and cost and the radioactivity induced by the deuterium-tritium (DT) fuel, “one can only guess at why ITER continues to be built,” Hirsch wrote.
ITER is only a proof of concept project. It is supposed to end in 2035. Based on the outcome, then a demonstration power plant may be built that will explore continuous or near-continuous operation. Assuming that the demonstration project is successful, a commercial fusion plant could conceivably be in operation around 2060. But there are many hurdles to cross, and there is still the problem of the exorbitant complexity and cost of the tokamak design, along with drawback of neutron radiation.
Even if the tokamak design is eventually perfected, it will be far too late to do what needs to be done now to reduce greenhouse gas emissions. Rather than pouring huge sums of money into engineering and construction of a design with so many drawbacks, we would be better off to focus on evaluating alternative designs.
There are many other fusion projects going on around the world. They all share the same premise: heat the fuel (usually deuterium-tritium) to incredibly high temperatures to make a plasma, contain it with magnets or lasers, and use it to boil water to make steam to power generators to make electricity. Expensive to build, costly to run, and still producing radioactive waste.
There is one notable exception, the HB11 process which uses lasers to fuse hydrogen and boron11. Conceived by Heinrich Hora, a pioneering theoretical physicist and Emeritus Professor at the University of New South Wales, HB11 technology differs radically from all other fusion approaches in that it does not require fuels to be heated, so it would require much less energy to run. In addition to avoiding the need to heat the fuel, boron is abundant and safe, produces an aneutronic reaction and therefore no radioactive waste. Another big advantage of hydrogen-boron fusion is that its energy is produce in the form of protons and alpha particles (helium nuclei). Because these are charged particles, it is possible to convert them directly to electricity without the use of steam turbines. And because it does not require steam turbines, it is scalable from small to very large installations.
The downside of the HB11 process is that you need even more extreme temperatures to produce it – 765 million degrees Celsius. One proposed method uses one laser to create a boron-11 plasma and another to create a stream of protons that smash into the plasma. The laser-generated proton beam produces a tenfold increase of boron fusion because protons and boron nuclei collide directly. Except for the extreme heat required, this approach avoids many of the pitfalls of deuterium-tritium fusion in a tokamak. The hopes are that this technology could produce useful energy in 30 years, so it also cannot address the immediate need to reduce the use of fossil fuels.
Iron pyrite (FeS2) is one of the most common forms of sulfide materials. It has a pale brass-yellow metallic luster that gives it a superficial resemblance to gold. During the California gold rush, inexperienced gold-hunters would mistake the pyrite for gold and hurry to the assayer’s office clutching their ore samples, only to find they were worthless. Amused by the naivete of the newcomers, more experienced prospectors dubbed the substance “Fool’s Gold.” It quickly entered the vernacular as a metaphor for false value and vain hopes.
Fusion energy is like Fool’s Gold. In a world besotted by the endless desire for more energy and in thrall to what we imagine to be the limitless capability of technology, the allure of a cheap, endless, non-polluting source of energy is irresistible. It is a modern-day Siren call, both mesmerizing and deceiving.
All this puts me in mind of the narrator’s close to Shakespeare’s play The Tempest.
Our revels now are ended. These our actors,
As I foretold you, were all spirits, and
Are melted into air, into thin air:
And like the baseless fabric of this vision,
The cloud-capp’d tow’rs, the gorgeous palaces,
The solemn temples, the great globe itself,
Yea, all which it inherit, shall dissolve,
And, like this insubstantial pageant faded,
Leave not a rack behind. We are such stuff
As dreams are made on; and our little life
Is rounded with a sleep.
On one level, this can be taken as a metaphor for the dream of fusion power – a fanciful play that will end when it collapses under the weight of its own inertia. On a deeper level, we might consider the play a metaphor for life, as Shakespeare suggests. “We are such stuff as dreams are made on.” Or, from As You Like It, “All the world’s a stage and all the men and women merely players.” Climate change may draw the final curtain on the relatively brief play called Mankind, and with it, all the dreams we might ever have.
- IEEE Spectrum
- LPP Fusion
- New Energy Times
- Bulletin of the Atomic Scientists with particular credit to Daniel Jassby who was a principal research physicist at the Princeton Plasma Physics Lab until 1999. For 25 years he worked in areas of plasma physics and neutron production related to fusion energy.