Reply To: Repowering the electric utility industry

[DaveMart]

It sprawled across two sites:
http://nextbigfuture.com/2012/08/lawrenceville-plasma-physics-raising.html
And:
http://www.energyfromthorium.com/forum/viewtopic.php?f=2&t=3762&p=47147#p47147

I am trying to move the discussion here, and will post on those sites to that effect, but pstudier has now replied to Cyril on the thorium energy site:

‘Good points! Conventional fusion people generally assume that all the energy that escapes the plasma is adsorbed. So all these gradients, plus complex interactions between plasma and magnetic fields lead to instabilities. Conventional fusion people have been building tokamaks bigger and bigger for decades, and with each new size, they get hotter, denser plasmas and new instabilities. The Wikipedia article “Plasma stability” lists over 50 different types of instability. These novel fusion schemes, focus, polywell, etc, are orders of magnitudes from breakeven and have not even begun to start evaluating the instabilities. For example, the polywell people brag about detecting 3 neutrons.

There are good scaling arguments that say tokamaks will never be economical, based on the maximum power density allowed by radiation damage of the first wall, costs of the magnets, blanket, shielding, support structure, etc.

Fusion is easy, breakeven is horrendous, and economic is probably impossible.’

And sebtal to pstudier on NBF:

‘The flip side is you really don’t want heavy elements into your plasma (this is why fusion is so damned hard), because while fully ionizing low elements is viable, if you introduce iron etc. atoms, they don’t fully ionise, and the resultant line emission leads to radiative quench of the plasma.

One of the problems with MCF is that eventually,a magnetic surface intersects the wall, and heavy elements are introduced. One of the significant advances in the field was the invention of divertors and x-points so you could peel off a flux surface using a magnetic null point (this sounds really complicated in words: it’s just this http://www.google.com/imgres?u…, and have the plasma directed onto a material surface in a controlled way at a much greater distance (along the field line) from the core plasma preventing contamination.’