Preface. When my husband Jeffery Kahn was a science writer at Lawrence Berkeley National Laboratory, we became friends with several astrophysicists who used to joke about how fusion was 30 years away and always would be.

If world peak oil was in 2018, then we’re out of time. ITER was supposed to be ready now, but its completion date for full fusion is now 2035.  By then energy decline will be in earnest, with diesel rationed to agriculture and other essential services.  Fusion, like all other contraptions that generate electricity, depends on fossil fuels for every single step of its construction in transportation, manufacturing and the making of its parts — the cement, steel, ceramics, microchips and more.

After the overview below, there are over half a dozen more articles about fusion. There are many issues with fusion not included in this post, see the others in category Energy/Fusion here.

Alice Friedemann  www.energyskeptic.com  Author of Life After Fossil Fuels: A Reality Check on Alternative Energy; When Trucks Stop Running: Energy and the Future of Transportation”, Barriers to Making Algal Biofuels, & “Crunch! Whole Grain Artisan Chips and Crackers”.  Women in ecology  Podcasts: WGBH, Jore, Planet: Critical, Crazy Town, Collapse Chronicles, Derrick Jensen, Practical Prepping, Kunstler 253 &278, Peak Prosperity,  Index of best energyskeptic posts

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Fusion is not likely to work out, yet it is the only possible energy source that could replace fossil fuels (No single or combination of alternative energy resources can replace fossil fuels).

Ugo Bardi (2014), in his book “Extracted” points out that even the minerals needed for nuclear fusion are finite, and the “infinitely abundant energy” thought possible at the beginning of the atomic age isn’t possible.  here’s why:

“In practice, past attempts to obtain controlled nuclear fusion as a source of energy had hinged on the possibility of fusing a heavier isotope of hydrogen, deuterium. But not even the controlled deuterium-deuterium reaction is considered feasible, and the current effort focuses on the reaction of a still heavier hydrogen isotope, tritium, with deuterium. Tritium is not a mineral resource, as it is so unstable that it doesn’t exist on Earth. But it can be created by bombarding a lithium isotope, Li-6, with neutrons that in turn can be created by the deuterium-tritium fusion reaction. (In this sense a fusion reactor is another kind of “breeder” reactor, as it produces its own fuel.) However, since the mineral resources of lithium are limited, and since the Li-6 isotope forms only 7.5 percent of the total, the problem of mineral depletion exists. 58″

The immense gravity of the sun creates fusion by pushing atoms together.  We can’t do that on earth, where the two choices (and the main projects pursuing them) are:

ITER uses magnetic fields to contain plasma until atoms collide and fuse. This has been compared to holding jello together with rubber bands.  Well, not really, ITER is far from being built:

• The cost so far is $22.3 billion
• The original deadline was 2016, the latest 2027 date is highly unlikely.
• Their goal of a ‘burning plasma’ that produces more energy than the machine itself consumes is at least 20 years away
• It’s so poorly run that a recent assessment found serious problems with the project’s leadership, management, and governance. The report was so damning the project’s governing body only allowed senior management to see it because they feared “the project could be interpreted as a major failure”.
• April 2014: The U.S. contribution to ITER will cost a total of $3.9 billion — 4 times as much as originally estimated according to a report that came out April 10, 2014
• Even if ITER does reach break-even someday, it will have produced just heat, not the ultimate aim, electricity. More work will be needed to hook it up to a generator. For ITER and tokamaks in general, commercialization remains several decades away.

Hirsch RL, Bezdek RH (2021) Fusion: Ten times more expensive than nuclear power. RealClearEnergy.org.

Hirsch & Bezdek wrote the 2005 Department of Energy Peak Oil report.

The U.S. and world fusion energy research programs are developing something that no one will want or can afford. Ever so slowly the promise of commercially viable fusion power from tokamaks has ebbed away.  Some recognized the worsening commercial outlook, but most researchers simply continued to study and increase the size of their tokamak devices — and to increase the size of their budgets.

Today, the ITER plant, which was initially expected to cost $5 billion, will now cost somewhere between $22 and 65 billion dollars.  Even at $22 billion, the cost is ten times more than a nuclear fission power plant, and 30 times more if $65 billion.  And nuclear fission power plants are considered to be too expensive for further adoption in the U.S.

The largest source of tritium in the world is heavy water nuclear reactors in Canada. The combination of very limited world production of tritium and its loss by radioactive decay means that world supplies of tritium are inherently limited.  It has recently become clear that world supplies of tritium for larger fusion experiments are limited to the point that world supplies are inadequate for future fusion pilot plants, let alone commercial fusion reactors based on the deuterium-tritium fuel cycle.  In other words, fusion researchers are developing a fusion concept for which there will not be enough fuel in the world to operate!

So fusion researchers are developing a fusion concept that stands no hope of being economically acceptable, running on a fuel that does not exist in adequate quantities.

To stop wasting funding on these pointless fusion projects, we recently suggested to the Secretary of Energy that she appoint a panel of non-fusion engineers and environmentalists to conduct the objective, independent evaluation we believe is necessary.

NRC (2021) Bringing Fusion to the U.S. Grid. National Research Council, National Academies Press.

This document starts out reasonably understandable in the summary.  Fusion science sounds cool, with words like corrosion, fracture toughness, peeling, and ballooning, like surfer slang action verbs of rip, ragdolled, and barreled.

Here’s a fairly understandable paragraph describing what needs to be solved before a pilot plant can be built.  A pilot plant is a tiny baby plant, far from producing profitable, commercial electricity with a positive energy return.

“Virtually every major component of a future nuclear fusion energy reactor will require materials development in order to provide confidence in the ability to withstand significant limits of essential material properties including: neutron damage, creep resistance, fracture toughness, surface erosion/re-deposition, corrosion, chemistry, thermal conductivity and many others. A particular challenge is the need to safely and efficiently close the fuel cycle, which for deuterium-tritium fusion designs involves the development of blankets to breed and extract tritium, as well as the fueling, exhausting, confining, extracting, and separating tritium in significant quantities.”

But then, like all “how far away is fusion” documents it gets into the weeds, where you need a degree in nuclear engineering to understand it.  For example, can you make any sense out of the following barrier to making fusion work?

Power exhaust in high power density, compact fusion systems has two key challenges. One is the experimentally observed narrow steady-state e-folding length of power flow in the scrape-off-layer (SOL). Since the peak heat flux at the divertor plate (qdiv) is inversely proportional to the power e-folding length [Greek formula with letters not on my keyboard], narrow power e-folding length gives rise to an excessive heat flux at the divertor plate. Experimental observation shows [Greek formula] where [Greek formula] and [Greek formula] are power e-folding length and the poloidal field at the plasma surface. Since [Greek formula], power e-folding length in a compact fusion device tends to be smaller. However, the high operating density of a compact fusion device is likely beneficial for enhancing radiative cooling and to achieve detached plasma state.  Another challenge is taming the transient heat flux including those due to ELMs (Edge Localized Mode). ELMs are an edge relaxation phenomena driven by the peeling/ballooning mode, whose onset is reasonably well understood and characterized.  ELM Suppression by methods such as application of 3D magnetic perturbations in DIII-D¹⁴ reveals the promise for minimizing the impact of transient heat fluxes on the first wall, but much more research is required, especially for managing the heat flux challenge of a compact, high power density fusion reactor.

But you can almost understand that the solution of “High plasma core power density presents a significant heat exhaust challenge for the plasma facing components, armor, and first wall in fusion systems” which probably means that a bunch of important stuff will melt If Solutions Aren’t Found.

The next paragraph is another mystery (not shown), and so is the solution: the  Department of Energy needs to “support studies of the compatibility of innovative divertor designs in toroidal confinement concepts with divertor plasma detachment, which can significantly relax the radiated power requirement, and including the possibility of liquid metal PFCs, and create a research program and facilities with linear devices for testing plasma facing components and non-plasma heat flux testing platforms, to identify, evaluate, and finalize a high-confidence, robust design for PFC and first wall armor materials, including both solid and liquid metal options, that are compatible with managing steady state and transient power loading.”

And so on.  The main reason to try read these documents even if you don’t understand them, is that you will really understand why fusion will be forever 30 years away, a phrase that’s a favorite of nuclear engineers themselves.

This document has nothing on fusion studies that go far more in depth describing the challenges.  Please do check out the following 247-page free book:  NRC. 2013 An Assessment of the Prospects for Inertial Fusion Energy. National Research Council, National Academies Press.   Or give it to an enemy to induce headaches.

My impression after reading many fusion books is that equipment has to be built with atomic precision, not a single atom out of place in some components.  Really???  And even if that were possible, with global conventional oil production flat-lining since 2005 and all oil, conventional and unconventional peaking in production in 2018, the world of the future will be much simpler, with precision of less than a thousandth of an inch (for more on that, read: Winchester S (2018) The Perfectionists: How Precision Engineers Created the Modern World).

Moyer (2010) Fusion’s False Dawn. Scientific American.

Scientists have long dreamed of harnessing nuclear fusion—the power plant of the stars—for a safe, clean and virtually unlimited energy supply. Even as a historic milestone nears, skeptics question whether a working reactor will ever be possible

The deuterium-tritium fusion only kicks in at temperatures above 150 million degrees Celsius — 25,00 times hotter than the surface of the sun.

Yet the flash of ignition may be the easy part. The challenges of constructing and operating a fusion-based power plant could be more severe than the physics challenge of generating the fireballs in the first place.  A working reactor would have to be made of materials that can withstand temperatures of millions of degrees for years on end. It would be constantly bombarded by high-energy nuclear particles–conditions that turn ordinary materials brittle and radioactive. It has to make its own nuclear fuel in a complex breeding process. And to be a useful energy-producing member of the electricity grid, it has to do these things pretty much constantly–with no outages, interruptions or mishaps–for decades.

Fusion plasmas are hard to control. Imagine holding a large, squishy balloon. Now squeeze it down to as small as it will go. No matter how evenly you apply pressure, the balloon will always squirt out through a space between your fingers. The same problem applies to plasmas. Anytime scientists tried to clench them down into a tight enough ball to induce fusion, the plasma would find a way to squirt out the sides. It is a paradox germane to all types of fusion reactors–the hotter you make the plasma and the tighter you squeeze it, the more it fights your efforts to contain it.  So scientists have built ever larger magnetic bottles, but every time they did so, new problems emerged.

No matter how you make fusion happen–whether you use megajoule lasers (like at Lawrence Livermore National Laboratory) or the crunch of magnetic fields–energy payout will come in the currency of neutrons. Because these particles are neutral, they are not affected by electric or magnetic fields. Moreover, they pass straight through most solid materials as well.

The only way to make a neutron stop is to have it directly strike an atomic nucleus. Such collisions are often ruinous. The neutrons coming out of a deuterium-tritium fusion reaction are so energetic that they can knock out of position an atom in what would ordinarily be a strong metal–steel for instance. Over time these whacks weaken a reactor, turning structural components brittle.

Other times the neutrons will turn material radioactive, dangerously so.

Other times the neutrons will turn benign material radioactive. When a neutron hits an atomic nucleus, the nucleus can absorb the neutron and become unstable. A steady stream of neutrons—even if they come from a “clean” reaction such as fusion—would make any ordinary container dangerously radioactive, Baker says. “If someone wants to sell you any kind of nuclear system and says there is no radioactivity, hang onto your wallet.”

A fusion-based power plant must also convert energy from the neutrons into heat that drives a turbine. Future reactor designs make the conversion in a region surrounding the fusion core called the blanket. Although the chance is small that a given neutron will hit any single atomic nucleus in a blanket, a blanket thick enough and made from the right material—a few meters’ worth of steel, perhaps—will capture nearly all the neutrons passing through. These collisions heat the blanket, and a liquid coolant such as molten salt draws that heat out of the reactor. The hot salt is then used to boil water, and as in any other generator, this steam spins a turbine to generate electricity.

Except it is not so simple. The blanket has another job, one just as critical to the ultimate success of the reactor as extracting energy. The blanket has to make the fuel that will eventually go back into the reactor.

Although deuterium is cheap and abundant, tritium is exceptionally rare and must be harvested from nuclear reactions. An ordinary nuclear power plant can make between two to three kilograms of it in a year, at an estimated cost of between $80 million and $120 million a kilogram. Unfortunately, a magnetic fusion plant will consume about a kilogram of tritium a week. “The fusion needs are way, way beyond what fission can supply,” says Mohamed Abdou, director of the Fusion Science and Technology Center at the University of California, Los Angeles.

For a fusion plant to generate its own tritium, it has to borrow some of the neutrons that would otherwise be used for energy. Inside the blanket channels of lithium, a soft, highly reactive metal, would capture energetic neutrons to make helium and tritium. The tritium would escape out through the channels, get captured by the reactor and be reinjected into the plasma.

When you get to the fine print, though, the accounting becomes precarious. Every fusion reaction devours exactly one tritium ion and produces exactly one neutron. So every neutron coming out of the reactor must make at least one tritium ion, or else the reactor will soon run a tritium deficit—consuming more than it creates. Avoiding this obstacle is possible only if scientists manage to induce a complicated cascade of reactions. First, a neutron hits a lithium 7 isotope, which, although it consumes energy, produces both a tritium ion and a neutron. Then this second neutron goes on to hit a lithium 6 isotope and produce a second tritium ion.

Moreover, all this tritium has to be collected and reintroduced to the plasma with near 100 percent efficiency. “In this chain reaction you cannot lose a single neutron, otherwise the reaction stops,” says Michael Dittmar, a particle physicist at the Swiss Federal Institute for Technology in Zurich. “The first thing one should do [before building a reactor] is to show that the tritium production can function. It is pretty obvious that this is completely out of the question.”

“This is a very fancy gadget, this fusion blanket,” Hazeltine says. “It is accepting a lot of heat and taking care of that heat without overheating itself. It is accepting neutrons, and it is made out of very sophisticated materials so it doesn’t have a short lifetime in the face of those neutrons. And it is taking those neutrons and using them to turn lithium into tritium.

ITER, unfortunately, will not test blanket designs. That is why many scientists—especially those in the U.S., which is not playing a large role in the design, construction or operation of ITER—argue that a separate facility is needed to design and build a blanket. “You must show that you can do this in a practical system,” Abdou says, “and we have never built or tested a blanket. Never.” If such a test facility received funding tomorrow, Abdou estimates that it would take between 30 and 75 years to understand the issues sufficiently well to begin construction on an operational power plant. “I believe it’s doable,” he says, “but it’s a lot of work.”

The Big Lie

Let’s say it happens. The year is 2050. Both the NIF and ITER were unqualified successes, hitting their targets for energy gain on time and under budget. Mother Nature held no surprises as physicists ramped up the energy in each system; the ever unruly plasmas behaved as expected. A separate materials facility demonstrated how to build a blanket that could generate tritium and convert neutrons to electricity, as well as stand up to the subatomic stresses of daily use in a fusion plant. And let’s assume that the estimated cost for a working fusion plant is only $10 billion. Will it be a useful option?

Even for those who have spent their lives pursuing the dream of fusion energy, the question is a difficult one to answer. The problem is that fusion-based power plants—like ordinary fission plants—would be used to generate baseload power. That is, to recoup their high initial costs, they would need to always be on. “Whenever you have any system that is capital-intensive, you want to run it around the clock because you are not paying for the fuel,” Baker says.

Unfortunately, it is extremely difficult to keep a plasma going for any appreciable length of time. So far reactors have been able to maintain a fusing plasma for less than a second. The goal of ITER is to maintain a burning plasma for tens of seconds. Going from that duration to around-the-clock operation is yet another huge leap. “Fusion will need to hit 90 percent availability,” says Baker, a figure that includes the downtime required for regular maintenance. “This is by far the greatest uncertainty in projecting the economic reliability of fusion systems.

It used to be that fusion was [seen as] fundamentally different from dirty fossil fuels or dangerous uranium. It was beautiful and pure—a permanent fix, an end to our thirst for energy. It was as close to the perfection of the cosmos as humans were ever likely to get. Now those visions are receding. Fusion is just one more option and one that will take decades of work to bear fruit…the age of unlimited energy is not [in sight].

Clery D (2013) The Most Expensive Science Experiment Ever. Popular Science.

Some people have spent their whole working lives researching fusion and then retired feeling bitter at what they see as a wasted career. But that hasn’t stopped new recruits joining the effort every year…, perhaps motivated by … the need for fusion has never been greater, considering the twin threats of dwindling oil supplies and climate change.  ITER won’t generate any electricity, but designers hope to go beyond break-even and spark enough fusion reactions to produce 10 times as much heat as that pumped in to make it work.

To get there requires a reactor of epic proportions:

• The building containing the reactor will be nearly 200 feet tall and extend 43 feet underground.
• The reactor inside will weigh 23,000 tons.
• Rare earth metal niobium will be combined with tin to make superconducting wires for the reactor’s magnets. When finished, they will have made 50,000 miles of wire, enough to wrap around the equator twice.
• There will be 18 magnets, each 46 feet tall and weighing 360 tons (as much as a fully-laden jumbo jet) with  giant D-shaped coils of wire forming the electromagnets used to contain the plasma

That huge sum of money is, for the nations involved, a gamble against a future in which access to energy will become an issue of national security. Most agree that oil production is going to decline sharply during this century.  That doesn’t leave many options for the world’s future energy supplies. Conventional nuclear power makes people uneasy for many reasons, including safety, the problems of disposing of waste, nuclear proliferation and terrorism.

Alternative energy sources such as wind, wave and solar power will undoubtedly be a part of our energy future. It would be very hard, however, for our modern energy-hungry society to function on alternative energy alone because it is naturally intermittent–sometimes the sun doesn’t shine and the wind doesn’t blow–and also diffuse–alternative technologies take up a lot of space to produce not very much power.

Difficult choices lie ahead over energy and, some fear, wars will be fought in coming decades over access to energy resources, especially as the vast populations of countries such China and India increase in prosperity and demand more energy. Anywhere that oil is produced or transported–the Strait of Hormuz, the South China Sea, the Caspian Sea, the Arctic–could be a flashpoint. Supporting fusion is like backing a long shot: it may not come through, but if it does it will pay back handsomely. No one is promising that fusion energy will be cheap; reactors are expensive things to build and operate. But in a fusion-powered world geopolitics would no longer be dominated by the oil industry, so no more oil embargoes, no wild swings in the price of crude and no more worrying that Russia will turn off the tap on its gas pipelines.

Hambling D (2011) Star power: Small fusion start-ups aim for break-even. NewScientist.

The deuterium-tritium fusion only kicks in at temperatures above 150 million degrees Celcius — 25,00 times hotter than the surface of the sun. Not only does reaching such temperatures require a lot of energy, but no known material can withstand them once they have been achieved. The ultra-hot, ultra-dense plasma at the heart of a fusion reactor must instead be kept well away from the walls of its container using magnetic fields. Following a trick devised in the Soviet Union in the 1950s, the plasma is generated inside a doughnut or torus-shaped vessel, where encircling magnetic fields keep the plasma spiraling clear of the walls – a configuration known as a tokamak. This confinement is not perfect: the plasma has a tendency to expand, cool and leak out, limiting the time during which fusion can occur. The bigger the tokamak, the better the chance of extracting a meaningful amount of energy, since larger magnetic fields hold the plasma at a greater distance, meaning a longer confinement time.

Break-even is the dream ITER was conceived to realize.

With a huge confinement volume, it should contain a plasma for several minutes, ultimately producing 10 times as much power as is put in.  But this long confinement time brings its own challenges. An elaborate system of gutters is needed to extract from the plasma the helium produced in the reaction, along with other impurities. The neutrons emitted, which are chargeless and so not contained by magnetic fields, bombard the inside wall of the torus, making it radioactive and meaning it must be regularly replaced. These neutrons are also needed to breed the tritium that sustains the reaction, so the walls must be designed in such a way that the neutrons can be captured on lithium to make tritium. The details of how to do this are still being worked out.

The success of the project is by no means guaranteed 

“We know we can produce plasmas with all the right elements, but when you are operating on this scale there are uncertainties,” says David Campbell, a senior ITER scientist. Extrapolations from the performance of predecessors suggest a range of possible outcomes, he says. The most likely is that ITER will work as planned, delivering 10 times break-even energy. Yet there is a chance it might work better – or produce too little energy to be useful for commercial fusion.

Richard Wolfson, in “Nuclear Choices: A Citizen’s Guide to Nuclear Technology”:

“In the long run, fusion itself could bring on the ultimate climactic crisis. The energy released in fusion would not otherwise be available on Earth; it would represent a new input to the global energy flow. Like all the rest of the global energy, fusion energy would ultimately become heat that Earth would have to radiate into space. As long as humanity kept its energy consumption a tiny fraction of the global energy flow, there would be no major problem. But history shows that human energy consumption grows rapidly when it is not limited by shortages of fuel. Fusion fuel would be unlimited, so our species might expand its energy consumption to the point where the output of our fusion reactors became significant relative to the global input of solar energy. At that point Earth’s temperature would inevitably rise. This long-term criticism of fusion holds for any energy source that could add to Earth’s energy flow even a few percent of what the Sun provides. Only solar energy itself escapes this criticism”. page 274

Robert L. Hirsch, author of the Department of Energy 2005 Peak Oil study, in his book “The Impending World Energy Mess”:

“Fusion has been in the research stage since the 1950s….Fusion happens when fuels are heated to hundreds of millions of degrees long enough for more energy to be released than was used to create the heat. Containment of fusion fuels on the sun is by gravity. Since gravity is not usable for fusion on earth, researchers have used magnetic fields, electrostatic fields, and inertia to provide containment. Thus far, no magnetic or electrostatic fusion concept has demonstrated success.”  Hirsch thinks this will never work out and it’s been a waste of tens of billions of dollars.

William Parkins, formerly the chief scientist at Rockwell International, asks in the 10 Mar 2006 edition of Science  “Fusion Power: Will it Ever Come?“

When I read Parkins article and translated some of the measurements to ones more familiar to me, it was obvious that fusion would never see the light of day:

• Fusion requires heating D-T (deuterium-tritium) to a temperature of 180 million degrees Fahrenheit — 6.5 times hotter than the core of the sun.
• So much heat is generated that the reactor vacuum vessel has to be at least 65 feet long, and no matter what the material, will need to be replaced periodically because the heat will make the reactor increasingly brittle as it undergoes radiation damage.  The vessel must retain vacuum integrity, requiring many connections for heat transfer and other systems.  Vacuum leaks are inevitable and could only be solved with remotely controlled equipment.
• A major part of the cost of a fusion plant is the blanket-shield component. Its area equals that of the reactor vacuum vessel, about 4,500 cubic yards in a 1000 MWe plant.  The surrounding blanket-shield, made of expensive materials, would need to be at least 5.5 feet thick and weigh 10,000 metric tons, conservatively costing $1.8 billion dollars.

Here are some of the other difficulties Parkins points out in this article:

The blanket-shield component “amounts to $1,800/kWe of rated capacity—more than nuclear fission reactor plants cost today. This does not include the vacuum vessel, magnetic field windings with their associated cryogenic system, and other systems for vacuum pumping, plasma heating, fueling, “ash” removal, and hydrogen isotope separation. Helium compressors, primary heat exchangers, and power conversion components would have to be housed outside of the steel containment building—required to prevent escape of radioactive tritium in the event of an accident. It will be at least twice the diameter of those common in nuclear plants because of the size of the fusion reactor.

Scaling of the construction costs from the Bechtel estimates suggests a total plant cost on the order of $15 billion, or $15,000/kWe of plant rating. At a plant factor of 0.8 and total annual charges of 17% against the capital investment, these capital charges alone would contribute 36 cents to the cost of generating each kilowatt hour. This is far outside the competitive price range.

The history of this dream is as expensive as it is discouraging. Over the past half-century, fusion appropriations in the U.S. federal budget alone have run at about a quarter-billion dollars a year. Lobbying by some members of the physics community has resulted in a concentration of work at a few major projects—the Tokamak Fusion Test Reactor at Princeton, the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, and the International Thermonuclear Experimental Reactor (ITER), the multinational facility now scheduled to be constructed in France after prolonged negotiation. NIF is years behind schedule and greatly over budget; it has poor political prospects, and the requirement for waiting between laser shots makes it a doubtful source for reliable power.

Even if a practical means of generating a sustained, net power-producing fusion reaction were found, prospects of excessive plant cost per unit of electric output, requirement for reactor vessel replacement, and need for remote maintenance for ensuring vessel vacuum integrity lie ahead. What executive would invest in a fusion power plant if faced with any one of these obstacles? It’s time to sell fusion for physics, not power”.

Former House of Representatives Congressman Roscoe Bartlett (R-MD), head of the “Peak Oil Caucus”:

“…hoping to solve our energy problems with fusion is a bit like you or me hoping to solve our personal financial problems by winning the lottery. That would be real nice. I think the odds are somewhere near the same. I am about as likely to win the lottery as we are to come to economically feasible fusion.”

Bartlett’s full speech to congress: http://www.energybulletin.net/4733.html

National Academy of Sciences. 2013. An Assessment of the Prospects for Inertial Fusion Energy

The 3 principal research efforts in the USA are all trying to implode fusion fuel pellets by: (1) lasers, including solid state lasers at the Lawrence Livermore National Laboratory’s (LLNL’s) NIF and the University of Rochester’s Laboratory for Laser Energetics (LLE), as well as the krypton fluoride gas lasers at the Naval Research Laboratory; (2) particle beams, being explored by a consortium of laboratories led by the Lawrence Berkeley National Laboratory (LBNL); and (3) pulsed magnetic fields, being explored on the Z machine at Sandia National Laboratories. The minimum technical accomplishment that would give confidence that commercial fusion may be feasible—the ignition of a fuel pellet in the laboratory—has not been achieved.

This is 247 pages long chock-full of the problems that fusion must overcome – not just technical but the funding — billions of dollars in the unlikely event any of the various flavors of fusion makes enough progress to scale up to a higher level.  If you ever wanted to know the minutiae of why fusion will never work, this is a great document to read  — if you can understand it that is.  I spent about 10 minutes grabbing just a few of the hundreds of “challenges” that need to be overcome:

• Making a reliable, long-lived chamber is challenging since the charged particles, target debris, and X-rays will erode the wall surface and the neutrons will embrittle and weaken the solid materials.
• Unless the initial layer surfaces are very smooth (i.e., perturbations are smaller than about 20 nm), short-wavelength (wavelength comparable to shell thickness) perturbations can grow rapidly and destroy the compressing shell. Mix Similarly, near the end of the implosion, such instabilities can mix colder material into the spot that must be heated to ignition. If too much cold material is injected into the hot spot, ignition will not occur. Most of the fuel must be compressed to high density, approximately 1,000 to 4,000 times solid density.
• To initiate fusion, the deuterium and tritium fuel must be heated to over 50 million degrees and held together long enough for the reactions to take place. Drivers must deliver very uniform ablation; otherwise the target is compressed asymmetrically. If the compression of the target is insufficient, the fusion reaction rate is too slow and the target disassembles before the reactions take place. Asymmetric compression excites strong Rayleigh-Taylor instabilities that spoil compression and mix dense cold plasma with the less dense hot spot. Preheating of the target can also spoil compression. For example, mistimed driver pulses can shock heat the target before compression. Also, interaction of the driver with the surrounding plasma can create fast electrons that penetrate and preheat the target.
• The technology for the reactor chambers, including heat exhaust and management of tritium, involves difficult and complicated issues with multiple, frequently competing goals and requirements.  Understanding the performance at the level of subsystems such as a breeding blanket and tritium management, and integrating these complex subsystems into a robust and self-consistent design will be very challenging.
• Avoiding frequent replacement of components that are difficult to access and replace will be important to achieving high availability. Such components will need to achieve a very high level of operational reliability.
• Experimental investigations of the fast-ignition concept are challenging and involve extremely high-energy-density physics: ultraintense lasers (>1019 W cm–2); pressures in excess of 1 Gbar; magnetic fields in excess of 100 MG; and electric fields in excess of 1012 V/m. Addressing the sheer complexity and scale of the problem inherently requires the high-energy and high-power laser facilities

References

Bardi, Ugo. 2014. Extracted: How the Quest for Mineral Wealth Is Plundering the Planet. Chelsea Green Publishing.

Biello, David.  June 2014. A Milestone on the Long and Winding Road to Fusion.  Scientific American.

Chang, Ken. Mar 18, 2014. Machinery of an Energy Dream Machinery of an Energy Dream. New York Times.

Clery, D. 28 February 2014. New Review Slams Fusion Project’s Management. Science: Vol. 343 no. 6174 pp. 957-8.

Hinkel, D *, Springer P * , Standen, A, Krasny, M. Feb 13, 2014. Bay Area Scientists Make Breakthrough on Nuclear Fusion. Forum. (*) scientists at Lawrence Livermore National Laboratory.

Moyer, M. March/April 2010. Fusion’s False Dawn. Scientific American.

Perlman, David. Feb 13, 2014. Livermore Lab’s fusion energy tests get closer to ‘ignition’. San Francisco Chronicle.