How Accurate Are Simulations in Advancing Fusion Research?

[HTGRBoy]

How effective is simulation in fusion research? Many years ago i designed simulators for fission reactors and they were extremely accurate, sometimes approaching 1% accuracy in terms of core behaviour. It seems to me that it should be possible to determine whether ITER can exceed breakeven, for example, by designing a quality simulation before building the thing. I sometimes get the feeling the scientists are afraid to do simulations because they already know what the answer will be and it is politically unacceptable. Does anyone have any insight into how much simulation is being done in fusion research and what kind of accuracies the simulations are achieving?

 

[Astronuc]

There is a lot of work in simulation of plasmas and fusion systems, e.g.,

http://cips.colorado.edu/simulation/publications.htm (U. of Colorado)

http://ptsg.eecs.berkeley.edu/ (U of California - Berkeley)

See the journal Physics of Plasmas.
http://pop.aip.org/

Also - some background on plasma and fusion (~9.5 Mb, so use 'Save target as')
http://wsx.lanl.gov/RSX/PPSS_2006/lectures/Bellantalk/BellanLANL206SummerSchool.ppt

www.ofes.fusion.doe.gov/News/IPPAPrint.pdf[/URL] (~5.5 Mb)

 

[HTGRBoy]

Astronuc,

Your reply was very succinct and clear, but, like any good politician, you did not answer the question, and neither do any of the references you cited.

So let me rephraseave any high quality simulations been done for ITER that demonstrate whether it can meet or exceed break-even?

 

[phyzguy]

I'm not an expert in this area, but do know something about it. I think the answer to your question is that it is a much more complicated problem than simulating a fission reactor. A fission reactor is a solid matrix, so everything stays more or less in place. In a system like ITER, you have a plasma, EM fields, nuclear reactions, and a lot of complex physics happening at once. I think simulations have been done, but the question is whether the simulations accurately incorporate all of the physics involved. I think in the past simulations have shown that much smaller reactors should achieve practical fusion energy, but when the reactors were built, new physics showed up that invalidated the simulations. So people are a little "gun-shy" about believing the simulations. At least this is what I think the situation is - anybody else know more?

 

[Astronuc]

Astronuc,

Your reply was very succinct and clear, but, like any good politician, you did not answer the question, and neither do any of the references you cited.

So let me rephraseave any high quality simulations been done for ITER that demonstrate whether it can meet or exceed break-even?

I'm not sure where the sophistication of simulation is with respect to demonstrating break-even with ITER. Breakeven certainly has not been achieved in other systems. I believe the simulations are focussing on the physics of the instabilities within the plasma with the intent of optimizing the heating methods that will minimize onset of instabilities while dumping as much heat in as possible.

Certainly one can demonstrate breakeven if one ignores the physics.

 

[GiftOfPlasma]

You can search PPPL's reports here: http://www.pppl.gov/techreports.cfm" type in ITER.

Simulation is just as effective in plasma physics as in other fields. There are many models which are accurate in different ranges of plasma conditions. Most of the models are classical but people are actively developing quantum plasma models. New physical effects show up in experiments but they aren't always bad (H-mode).

The design of ITER is pretty well understood. ITER looks quite a bit like JET scaled up. A lot of the other technologies are being tested out in other reactors first. There are lots of simulations of all facets of the design from the gyrotrons to plasma wave mode conversion and tunneling.