The Stagecoach and the Spaceship

Posted by Rezwan on Apr 23, 2010 at 10:55 AM
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Differentiating Fusion

Explaining the concept of aneutronic fusion has proven challenging.  Here’s a summary of the difference between conventional Deuterium Tritium fusion and aneutronic fusion:

Conventional fusion - neutrons

Basically, the goal of conventional fusion reactions is to produce neutrons.  Neutrons produce heat and radiation.  The heat boils water to create steam to run a turbine and generate electricity. 

What’s the big deal with neutrons?  They make things they touch radioactive, so you have a waste disposal problem.  Also, tritium (the other ingredient besides deuterium in the conventional approach), is radioactive, very expensive (has to be generated by nuclear reactions), and useful in nuclear weapons applications.  These issues are played up or down depending on who you talk to.  Charles Seife (”Sun in a Bottle”) refers to these as fusion’s “dirty secret”.  Fusion scientists note that the radiation is short lived and is easily managed, nothing like fission. 

In any case, these factors tarnish the shining promise of fusion to some extent.  But that’s only because people haven’t been informed of the aneutronic fusion ideal.

Aneutronic fusion - “without” neutrons

In contrast, aneutronic fusion (“a” = not - not neutronic) does not seek to produce neutrons as a by-product of the reaction.

A few neutrons are, indeed, produced, but so few that it’s negligible, and far fewer than conventional fusion.  It’s simply not the goal. 

What’s great about this?  It gets rid of Charles Seife’s “dirty secret” - the tritium and neutron-generated radiation are gone. 

Bonus:  Unlike tritium, hydrogen and boron are plentiful, clean, cheap sources of fuel - you may even have some boron in your house right now, in the form of borax.  When they fuse, they generate helium, a harmless gas (people inhale it to talk funny).  The 3 helium nuceli come out as positively charged ions - electricity itself.  No need for steam or a turbine for electricity. 

Goodbye, Steam Engine!

No need for steam.  Put another way, conventional fusion uses a space age fuel to run an old fashioned steam engine.  Aneutronic fusion gets rid of the steam engine.  It’s time we left the 1800s!

Aneutronic upside

All the promise of conventional fusion, intensified. 

Aneutronic fusion is truly clean, green, unlimited energy.  No radiation, no weapons potential, no green house gases.  And if an inexpensive way can be found to do it, then the energy is cheap, easily distributed, accessible.  We solve the global warming crisis, we get energy for everyone so that electricity becomes equally available everywhere - people stop chopping down their forests.  Most importantly, we can generate clean water (desalinization - reverse osmosis - very expensive).  Energy = water.  All the deserts in the southwest will no longer be lost to salt (our irrigation farming practices will now become sustainable - currently we’re on course to poison all of California in about a hundred years - no more bread basket) - and more. 

Aneutronic downside - difficulty

The big problem with aneutronic fusion is that it’s more difficult than conventional fusion.  It requires one to three orders of magnitude more energy than conventional fusion to pull off.  As scientists are barely getting a grasp of conventional DT fusion (they don’t expect to have anything solid for 10-30 years), aneutronic aspirations tend to be shelved.  This is explained in various ways.  A prominent physicist at LIFE (Laser Inertial Fusion Energy program at NIF) explained it like this:  the physics challenges of DT fusion are pretty well understood, and it’s the engineering challenges that are the barrier.  But engineering, we can handle.  In contrast, the physics of aneutronic fusion are not as well understood, which makes it more of a pure science/physics problem and in the “speculative” realm.  We’re speculating about how it actually works.

Note that the LIFE physicist was very interested in eventually cracking aneutronic fusion.  The issue, however, is one of strategy.  He emphasized that fusion is perceived as a failure, and needs a success to recapture the public (and funders) imagination.  Thus, all energy should be put to the projects that will yeild results quickly - such as NIF and LIFE.  Success in these areas should translate into better support of fusion all around, and then maybe these other more challenging problems can be tackled.

That’s a valid strategy, and may be the one that works.  Our organization is trying to get diversified approaches to fusion happening now - even without laser success (since that’s a year off anyway - the more time we waste, the fewer students will be enrolling in fusion sciences…the pipeline needs to be fed now…)  But enough about strategy - let’s get back to differentiating DT and aneutronic fusion.

Stagecoach Metaphor

I was at Princeton recently, visiting some researchers at PPPL (Princeton Plasma Physics Labs) to get a sense of their views on aneutronic fusion.  This was a great visit.  They seem to be more open to aneutronic fusion than they have been for some time.  The time is ripe for more collaboration, but the budget is tight. 

I spoke with a prominent fusion physicist.  He said that aneutronic fusion was indeed, the ultimate goal of fusion research.  But he echoed the strategy of the LIFE physicist:  aneutronic fusion is too difficult, and we need to spend all the research money right now developing conventional fusion first.  He also supplied the great metaphor.  He likened the strategy to the need to develop the stagecoach before you can develop a high-performance sports car. 

I would liken it more to developing a stagecoach before you develop an elegant, radiation free spaceship. 

The Spaceship beyond the Stagecoach:  A strategy for public support of fusion

Physicists wonder why there isn’t more public support for fusion.  I think a big part of the reason is that most people are unaware of the spaceship lying beyond the stagecoach.  People don’t know about aneutronic fusion.  Ask anyone if they know what “aneutronic fusion” is. 

With all the delays in development of conventional fusion, and the realization that the reactors envisioned are so huge, expensive, and still have radiation problems - it’s no wonder that people don’t care.  They figure solar energy has a better chance of becoming affordable and ubiquitous before fusion.

It’s not so much that fusion is a pipe dream - but that, as a pipe dream, there isn’t more of a payoff, and there isn’t more of an effort being put to exploring the problem in all its wonderous dimensions.

Conventional fusion doesn’t have a big payoff.  Aneutronic fusion does. 

Importance of funding diverse approaches

At the Focus Fusion Society (FFS), we start with the ideal.  We want the sports car, the spaceship, the true holy grail of fusion, the big payoff.  And we know it’s incredibly difficult.  But we don’t buy the idea that all research money has to go to conventional fusion in a 20-50 linear year journey to develop the cumbersome stagecoach.

First of all, we want resources spent in parallel on multiple approaches to various stagecoach models. 

Also, we want adequate resources fast-tracked to aneutronic fusion projects.  In particular, we want Eric Lerner’s dense plasma focus project funded (he’s undercapitalized).  And our society is looking for other projects we like - and trying to create perspective on all the projects out there for better comparison, decision-making, collaboration. 

Perhaps the Princeton physicist is right, and until the stagecoach is finished, we can’t possibly figure out the spaceship.  Certainly, working on the stagecoach provides ideas for the spaceships (Another researcher at PPPL pointed out that an aneutronic idea he got actually came out of the work he did on the conventional tokamak).

We think that by opening up the race between the design for the stagecoach and the design for the spaceship - we’ll increase public interest and support for both and that this is win-win.  We’d also like to see more collaboration.

If you look around this website, this isn’t all reflected here yet.  It’s the emerging strategy that is coming about from discussions on our forums, and from the time I’ve been taking to talk to various researchers and funders and members about fusion.