By: Melchior! on Venerdì 12 Settembre 2014 12:04
gli "enormi problemi" di ITER [ talmente enormi da confinare con impossibili ]:
1. The ITER design was downsized in the 1990's when it was realized that
the first wall problem was, at the time (and maybe for a long time)
insurmountable at the requisite power levels.
2. tritium breedinging via neutron multiplication in the first wall via
Li-6 and Li-7 neutron capture, now has Be added as a neutron multiplier.
Be is a really bad idea, from a health safety POV. Even so, every neutron
is precious, and I don't believe they'll actually maintain a 1.1 ratio of
neutrons/tritons. DoE publishes reviews of the ITER program periodically.
One of the recent (several hundred pages) glossed over the tritium
breeding "strategy" in a few paragraphs.
3. How likely is it that they'll successfully scavenge ALL of the bred
and unburned tritium? Not very.
4. ITER now is at a US$13B cost, isn't finished, and is STILL 1/6 the
size of a commercial power plant. It is a monster.
5. ITER is now robbing EU Framework Programme funds (FP-7 and next FP-8)
for basic research to sustain ITER.
6. Hot fusion suffers pathologically from bremstrahlung radiational
plasma cooling that increases exponentially as the temperature increases.
E.g., you pump in more power to push the reaction, but it's cooling the
plasma faster than you can pump it in. Excellent MIT thesis on this
problem 15 years ago, or so.
7. Fast neutron activation of the chamber and all materials is a
significant problem, as is the tritium inventory. I believe the tritium
inventory of ONE commercial, 1 GWe plant for 1 day is comparable to
current world tritium stocks. That's a lot of tritium to make and keep on
hand.
8. Laser fusion (e.g. Inertial Confinement Fusion, or ICF), was developed
for weapons effect simulation. That is, the once classified indirect
drive (use a Hohlrum that produces x-rays that implode the capsule)
"simulates" the physics package of a hydrogen bomb: in the privacy of your
home, if you will. However, if you want to produce power, then you need
to have a 1 MJ UV laser, firing 10 times/second with a gain of at least
100x, and they'd prefer 1000x. Most "containers" don't like impulse
power, and hence setting off 48 sticks of dynamite (2.2 MJ/stick), or 500
sticks at a time isn't a good idea, either. NIF only gets 10 - 20
shots/DAY! Small rep rate problem too.
9. However, you can make a bad idea, worse: use either Tokamaks or NIF
(Livermore National Ignition Facility) as sources of fast neutrons to
fission nuclear waste. LLNL calls this LIFE: Laser Inertial Fission
10. Those superconducting magnets, up close and personal to the plasma?
Neutron damage, that is inevitable due to the necessary fluxes and
energies, severely change the superconducting properties of magnets.
These are typically Type I, NbSn or similar compounds, running at 20K. It
is also very exciting when the magnets "go normal" or quench. There are
gigajoules of energy stored in the magnetic field that WILL release.
Clever windings can dump this into copper braid interwoven with the
superconductor. But, it stresses things such that you aren't sure you
want to do this again. Was a major concern on MFTF-B, though since that
mirror machine was only turned on, once, to validate the neutral beams (in
order to pay the vendor), we've not played with ITER size magnets since
(1986, or thereabouts).
