July 07, 2008

The next Bussard IEC fusion reactor could be 100MW size producing net energy

Dr Nebel is talking about is a 1.5 meter 100 MW net power fusion reactor Dr Nebel has said he is getting good data from the WB7 test device. He is under a publishing embargo and cannot discuss the data, (neutron counts) but he has said the next device might as well be a 100MW version. This 100MW version may only cost $20 million to make. The implication is that Dr Nebel and his team are getting very good results. Hopefully this speculation is confirmed in August or September of this year with results published and next stages funded.

Dr Nebel said: The one you have to worry about is the input power scaling, because that one is related to the plasma losses (or transport). This one answers the question of “How much power do I need to supply to the device to maintain constant Beta”. Theoretical modeling of transport has a much poorer track record than plasma equilibrium has. These scaling laws are where the major risks for the larger device reside. The major saving grace is that for the Polywell is that the projected average densities are ~ 2 orders of magnitude higher than they are in Tokamaks so the energy confinement times don’t have to be all that good. (It’s the product of the density and the confinement time that’s important.) Our contention is that since our projections for a power producing device only require a machine [1.5 Meters in diameter would in theory be able to produce something around 100MW of net power] we might as well build the next one in that size range and accept the risk. The machines just aren’t all that expensive. Also, there are a multitude of things that can be done to improve confinement (such as pulse discharge cleaning, pellet injection, etc.) that have been successful in the magnetic confinement program that can be instituted if our projections fall short. This approach will minimize the development time and lead to a lower costs for the overall program.

The peak fields for the reactor designs (at least for our reactor designs) are in the 5-10 T range. however, these are work in progress.

We have run Gauss meters all over the face of the cubes and through the corners and we don't see any low field regions. The fields peak near the conductors and fall off near the coil centers, as you would expect.

Other Dr Nebel comments of interest:
1. The theory says that you can beat Bremstrahlung, but it's a challenge. The key is to keep the Boron concentration low compared the proton concentration so Z isn’t too bad. You pay for it in power density, but there is an optimum which works. You also gain because the electron energies are low in the high density regions.

2. The size arguments apply for machines where confinement is limited by cross-field diffusion like Tokamaks. They don't apply for electrostatic machines.

3. The Polywell doesn't have any lines of zero field. Take a look at the original papers on the configuration. See :
Bussard R.W., FusionTechnology, Vol. 19, 273, (1991) .
Krall N.A., Fusion Technology. Vol. 22, 42 (1992).

Furthermore, one expects adiabatic behavior along the field lines external to the device. Thus, what goes out comes back in. Phase space scattering is small because the density is small external to the device.

4. The machine does not use a bi-modal velocity distribution. We have looked at two-stream in detail, and it is not an issue for this machine. The most definitive treatise on the ions is : L. Chacon, G. H. Miley, D. C. Barnes, D. A. Knoll, Phys. Plasmas 7, 4547 (2000) which concluded partially relaxed ion distributions work just fine. Furthermore, the Polywell doesn’t even require ion convergence to work (unlike most other electrostatic devices). It helps, but it isn’t a requirement.

5. The system doesn’t have grids. It has magnetically insulated coil cases to provide the electrostatic acceleration. That’s what keeps the losses tolerable.

6. The electrostatic potential well is an issue. Maintaining it depends on the detailed particle balance. The “knobs” that affect it are the electron confinement time, the ion confinement time, and the electron injection current. There are methods of controlling all of these knobs.

Bussard thought the truncated dodecahedron might be better than the truncated cube of WB-6. Reason, the cusps are smaller, the triangular corners of the "cube". The electrons would have a tougher time escaping.

Where Dr Nebel originally posted his comments about making a reactor of "that size"

Polywell forum discussion speculating on the cost to make just one 100MW prototype system

$20-50 million depending upon the magnets and power supplies. If you run D-D and don't care about coil longevity (1 hr estimated) we can make do with some specially constructed MRI magnets (water jackets for alpha/neutron cooling). That might be acceptable for initial experimental purposes. (360 - 10 second runs). Thus $20 million for big test machine and $50 million for a better big test machine.

More questions from Art Carlson, the critique who was having a productive exchange with Dr Nebel

M Simon notes some problems and challenges for a 100MW version of an IEC fusion reactor.

The "first wall" problem is the hardest of the "we have very little idea" problems. A B11 coating has been tried for ITER. That would be ideal if it works. However, ITER is now looking into diamond coating. No mention of Boron these days.

Cooling the coils from alpha impingement is hard. But we do know where to start and we do have some tricks.

Some other lesser problems: design for compactness and energy extraction. Power converter designs. Control of reactant flows. Superconducting magnets. Integrated reactor controls. POPS enhancement.

Roger Fox has written a diary on Dr Nebel's work and Dr Nebels comments and adds his own speculation

Currently the fuel is "puffed" in gaseous form, there is no carburetor. The fuel ions are puffed in, the plasma lights up, some fusion occurs, and the magnets get very hot. All this occurs in under a second. It takes hours for the magnets to cool down for the next run. Superconducting magnets would solve this problem, but at a much higher cost.

Theory says if you scale up the 35 cm magnets to 2 meters, you will have a 500 mw net power reactor. This scaling theory is unproven. A carburetor also needs to be built and there is a possibility that slightly different designs can be more efficient.

An introduction to inertial confinement fusion

IEC fusion uses magnets to contain an electron cloud in the center. It is a variation on the electron gun and vacuum tube in television technology. Then they inject the fuel (deuterium or lithium, boron) as positive ions. The positive ions get attracted to the high negative charge at a speed sufficient for fusion. Speed and electron volt charge can be converted over to temperature. The electrons hitting the TV screen can be converted from electron volts to 200 million degrees. The old problem was that if you had a physical grid in the center then you could not get higher than 98% efficiency because ions would collide with the grid. Bussard's innovation was to use magnets in a configuration that the electrons and ions never hit and keep losses 100,000 times lower. 99.999+% efficiency.

Previous update on the inertial confinement fusion demonstration project

A review of new funded approaches to nuclear fusion

If IEC nuclear fusion works as well as hoped then not only does it solve energy issues but also provides super space capabilities with launch costs reduced 1000 times

Even expensive net power generation means that one fusion reactor can burn the fuel of ten regular fission reactors to make all nuclear power cleaner.


Mercy Vetsel said...

Wow! Now this is great stuff and the reason I read this blog. I tried not to get too excited after I read the June 12th post, but after this update, it sounds even more promising.

This may or may not pan out, but unlike Black Light Power, this is for real.

Notice that the skeptical Dr. Carlson seems to soften his position by the end of the dialogue.

Obviously, even if the next step is 100MW and even if no show-stoppers appear in August, we’re still looking at several years until the conventional engineering problems can be resolved. BUT, this could be one of the biggest discoveries in my lifetime.

I’m curious to know what the scale model predicts for the NET output for a 100MW machine. Or is 100MW the net output?


bw said...

If the scaling holds up as expected then the 1.5 meter size means 100MW of NET power output.

Noah said...

Here's what I'm hoping for: The results from series of experiments are being used to validate their physical models, which relate fuel input rates, magnet currents, electrostatic fields, geometry, energy losses, power output, etc.

If they can end up with a validated model, then they've got the world at their finger-tips: they will be able to configure a larger system and determine what configuration maximizes the energy gain.

I'm looking forward to hearing more!

Dezakin said...

Here's what I expect: Massive braking radiation losses making electrostatic fusion useful only as a neutron source, and this concept will quietly wither over the next decade, yet clamoring for more grant money just in case they missed something.

Joseph said...

1) "Even expensive net power generation means that one fusion reactor can burn the fuel of ten regular fission reactors to make all nuclear power cleaner."

Did you mean "burn the waste of" ?

bw said...

Yes, burn the waste which is still unburned fuel.

Cyril R said...

Do you have any information on how durable this system would be? High MeV neutrons have destructive influences on pretty much all materials.

Brock said...

Where's the $3 million figure from? That's lower than I've seen before.

bw said...

The 3 million figure is from Roger Fox.

Lets squeeze it, and the cusps are even smaller now. Since Polywell recirculates the electrons, this sort of thinking is no longer paramount. But ya never know, and for 3 million, why not build one to see what the difference in performance might be.

It is a quote below one of wiffle ball configurationm graphics. EMC2 the company working on the projects have previously quoted $200 million for a project with such a large energy level and size. I believe that this would mean several reactors built for testing.
The $3 million figure I believe is a one off demo attempt (to shake out scaling issues) and one which does not work out the carberator and other feed systems for a full commercialized version of a 100MW IEC reactor.

a fully funded effort requires more cost for trial and error and for sorting out all the system issues.

the statement apparently is that they would learn more from a 1.5 meter 100MW demo than from a modified 35 cm demo and that costs for the larger size can be kept under control.

Brock said...

Hmm. That figure seems really off the cuff. But I guess if the current 35cm one cost $1.8M, than $3M for "no new systems, just 3x bigger" isn't impossible.

Thanks for the clarification.

bw said...

Unfortunately because of the publication restrictions all of this article is basically aggregated tea leaf reading.

A couple of off the cuff remarks from Dr Nebel interpretted. Speculation from the IEC fusion discussion forums.

the multiple reactors for X budget is also from some who are actual experimental practioners (like M. Simon).

===durability question from Cyril

This will depend upon whether Proton-Boron11 fusion can be achieved. That is aneutronic. No neutrons. If there are neutrons then this is the same issue as a working Tokomak would face. One would run if for a few decades and then have to deal with the irradiated parts and damage.

Roger said...

The 3 million figure is for a 30cm dodecahedron operated in pulse mode just like WB-7.

A 160cm 100MW net power size reactor would likely cost a minimum of 20 million. Power supply is the culprit, some serious grid power will be required.

Roger said...

Dezakin said...

Here's what I expect: Massive braking radiation losses making electrostatic fusion useful only as a neutron source,

Here we go again.

Todd Riders theory in wire gridded IEC systems says Bremsstrahlung radiation relies on a square topped potential well, a broad wide well, with less than optimum ion focus.

Except that shape well doesn't occur in a Polywell, which has no wire grids ...

Bremsstrahlung radiation occurs when you have hi density and hi temp/energy electrons. Which doesnt occur in a Polywell.

In the potential well electrons are dense and have given up their kinetic energy, as potential energy to the potential well.

We know the potential well exists, it has been measured, and without the potential well you cant accelerate ions, so you would have no fusion.

Isn't Todd Rider working as a biologist now ?

Roger said...

bw said...

"Unfortunately because of the publication restrictions all of this article is basically aggregated tea leaf reading."

Unkind but basically correct.

"One would run if for a few decades and then have to deal with the irradiated parts and damage."

Decades ? That seems optimistic.

bw said...


Thanks for the clarifications.

Plus I should say that it was masterful tea leaf reading and reading between lines and using exceptional knowledge of the known work, science and engineering.

I will make the adjustment to the article on the cost of a big demo system.

Cyril R said...

Thanks for all the clarification. Aneutronic, yes of course. The reason I was wondering about durability is that they keep building new (bigger) ones but it's not entirely clear how the device would hold up over a decade or so. Of course if it's really this cheap then that's not a showstopper.

Cheers, Cyril