Alternatives to tokamak fusion

This is a draft of a summary I'm doing on alternatives to tokamak fusion.  It seems to me that if any of these alternatives could be developed into commercial applications within the next 1 to 5 decades, it would be the most important invention since...well, fire.  I know that sounds incredibly hyperbolic, but consider this:  Let's say any of these technologies could be developed such that they could compete with coal or nuclear fission in the operating cost to generate electricity (that's about 2 cents per kilowatt hour in the United States).  Well, fusion is vastly more environmentally friendly than coal or nuclear fission, so the non-tokamak fusion alternative would very quickly replace all the world's coal and nuclear fission power plants.  It would also replace natural gas power plants, because it would be cheaper.  Finally, it would represent an essentially limitless supply of electricity...and dramatically hasten the day when automobiles use electricity (e.g. plug-in hybrids) for most or even all of their power.

1. GENERAL SUMMARY

Description:  This document contains summaries of alternatives to standard (tokamak) fusion.  The general positive attribute of these alternatives is that they appear to require far smaller equipment expenditures to create fusion.  In many cases, the amount  of money required to create fusion—although not a break-even rates—is less than $1 million.  None of these alternatives are as far along developmentally as tokamak fusion, but it seems possible that some alternatives might “leapfrog” tokamak fusion, given the current developmental path of tokamak fusion (i.e., a break-even test reactor a decade away, and commercial reactors at least 2-3 decades into the future...if not more).

Pluses:

• Alternative technologies appear to require significantly smaller equipment expenditures to achieve fusion, compared to the standard tokamak.

• All these alternative technologies are significantly less studied than standard tokamak fusion, so it should be possible for “newcomers” to the field to quickly make important contributions...particularly given the smaller equipment expense to generate fusion.

• These technologies generate no long-lived radioactive materials.

• Fusion creates very large amounts of energy in a very small space; a 20 MW (megawatt) power plant (comparable to the UNC power plant) could fit in a 2-car garage.  Therefore, even densely populated areas such as New York City could generate all their power needs locally.

• These technologies produce no greenhouse gases; no air pollution in fact. Further, they also require no mining or resource extraction to provide fuel to the plant.

Minuses:

• By far the most serious potential minus to all these technologies is that they might conceivably be used to produce powerful explosions. This is not to say that any of them could generate such explosions by accident; merely that people with malicious intent might be able to produce powerful explosions.  Given the inexpensive nature of these technologies, such weapons would not necessarily even require expenditures by governments; small groups might be able to produce the devices.

2. PLASMA FOCUS REACTOR (HYDROGEN-BORON FUSION)

Description: Focus fusion reactors use a plasma focus device and hydrogen-boron fuel to achieve fusion.  This requires a much higher temperature than conventional (deuterium-tritium) fusion; hydrogen-boron fusion requires a temperature of approximately 1 billion degrees Kelvin.

“The plasma focus device consists of two cylindrical copper or beryllium electrodes nested inside each other. The outer electrode is generally no more than 6-7 inches in diameter and a foot long. The electrodes are enclosed in a vacuum chamber with a low pressure gas (the fuel for the reaction) filling the space between them.  A pulse of electricity from a capacitor bank (an energy storage device) is discharged across the electrodes. For a few millionths of a second, an intense current flows from the outer to the inner electrode through the gas. This current starts to heat the gas and creates an intense magnetic field. Guided by its own magnetic field, the current forms itself into a thin sheath of tiny filaments; little whirlwinds of hot, electrically-conducting gas called plasma.  This sheath travels to the end of the inner electrode where the magnetic fields produced by the currents pinch and twist the plasma into a tiny, dense ball only a few thousandths of an inch across called a plasmoid. All of this happens without being guided by external magnets.  The magnetic fields very quickly collapse, and these changing magnetic fields induce an electric field which causes a beam of electrons to flow in one direction and a beam of ions (atoms that have lost electrons) in the other. The electron beam heats the plasmoid thus igniting fusion reactions which add more energy to the plasmoid. So in the end, the ion and electron beams contain more energy than was input by the original electric current. These beams of charged particles are directed into decelerators which act like particle accelerators in reverse. Instead of using electricity to accelerate charged particles they decelerate charged particles and generate electricity. Some of this electricity is recycled to power the next fusion pulse while the excess, the net energy, is the electricity produced by the fusion power plant.” (Focus Fusion Society, 2005).

Pluses: 

▪ Generates electricity directly (from a particle decelerator); therefore, a steam generator is not required.  This is claimed to significantly reduce capital cost.

▪ Does not require external magnets to contain plasma.

▪ Appears to be technically far along in development (fusion apparently achieved, and claimed to be within striking distance of breakeven).

Minuses:

▪ Requires even higher temperatures than standard (deuterium-tritium) fusion. 

Researchers:

1. Eric Lerner, Lawrenceville Plasma Physics (LPP), Inc.   

2. Bruce Freeman, Texas A&M.

3. Hank Oona, Los Alamos National Laboratory.

References:

1. PES Network, Inc., 2006.  “Sandia Z-Pinch and Focus Fusion Compared.” Available at: Comparison of Z-Pinch and Focus Fusion
   

2. Focus Fusion Society, 2006.  “Lawrenceville Plasma Physics and Chilean Nuclear Commission Initiate Experimental Collaboration to Test Scientific Feasibility of Focus Fusion.  Available at: Focus Fusion feasibility test in Chile 

3.  SONOFUSION

Description:  Sonofusion is an extension of the phenomenon of sonoluminescence, which occurs when a cavitation bubble collapses.  Sonofusion as produced by Taleyarkhan (Purdue) involves use of deuterated acetone (i.e., the hydrogen in the acetone is in the form of deuterium, which is necessary for fusion to occur).

Pluses:

▪ Appears to be mechanically very simple.

Minuses:

▪ None apparent.

Researchers:

1. R. P. Taleyarkhan at Purdue University (formerly of Oak Ridge National Laboratory). 

3. D, Felipe Getain (Impulse Devices Inc.)

4. Acoustic Fusion Technology Energy Consortium (AFTEC, consisting of:  Boston University; Impulse Devices, Inc.; Purdue University; University of Mississippi; and the University of Washington Center for Industrial and Medical Ultrasound). 

References:

1. Acoustic Fusion Technology Energy Consortium (AFTEC), 2005.  “AFTEC formed.”  Available at: AFTEC formed.

5. About.com, 2005.  “Rusi Taleyarkhan - Bubble Fusion.”  Available at: Sonofusion (aka, "bubble fusion")
   

4. PYROELECTRIC CRYSTAL FUSION

Description:  “In April 2005, Seth Putterman's group at UCLA published a paper describing a new method of nuclear fusion based on pyroelectric crystals. In the experiment a pyroelectric crystal, lithium tantalate (LiTaO₃), was heated 25 C in low-pressure (0.7 Pa) deuterium gas generating a potential of 100 kV. The electric field of 25 GV per meter, focussed by a tungsten needle, ionizes the deuterium which is accelerated into a target of erbium deuteride (ErD₂). There the deuterium nuclei fuse about once in every million collisions to produce helium atoms and about 1000 neutrons per second.”

Pluses:

▪ Appears to be mechanically very simple.

▪ Appears to produce fusion (in miniscule amounts) with extremely simple equipment.

Minuses:

▪ May never be capable of generating breakeven energy.

References:

1. “Pyroelectric Crystal Fusion.”  Available at:  Pyroelectric crystal fusion

5.     COLLIDING ELECTRON SPIRAL TOROIDS REACTOR (CESTR)

Description: In a manner similar to ball lighting, electrical spiral toroids generate their own magnetic containment fields.  The CESTR attempts to collide toroids of boron and hydrogen to produce hydrogen-boron fusion.

References:

1. Electron Power Systems, Inc.  Explanation of the technology.  Available at:  Electron Power Systems, CESTR reactor  

Comments

[Rob McMillin]

How does sonofusion get to have no minuses, while pyroelectric crystal fusion "May never be capable of generating breakeven energy"? Doesn't the same problem hold for both? In light of Seth Putterman et al's research indicating Taleyarkhan's alleged fusion is the product of Californium isotope decay and a widespread inability to reproduce results (not to mention over a decade of research in this area by various parties), doesn't that sort of make both of these dead ends (at least, so far)?

[Steve Kunkee]

Where is information on Bussard's reactor? It is at least as far along as the focus device.

[Mark Bahner]

Hi Steve,

Yes, at the time I wrote my summary of alternatives to tokamak fusion, I hadn't heard about Bussard's reactor.

I was aware of the Farnsworth fusor, which as I understand it is universally agreed as never going to generate breakeven energy.

But I wasn't aware of Bussard's alternative. It does seem very intriguing.

http://en.wikipedia.org/wiki/Polywell

Mark

[Mika]

Thanks for this, very much appreciated!