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PostPosted: Oct 27, 2014 3:39 pm 
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Does anyone know of any muon-based reactions that release additional muons? (analogous to fission releasing more neutrons)


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PostPosted: Oct 27, 2014 4:01 pm 
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Kirk Sorensen wrote:
Does anyone know of any muon-based reactions that release additional muons? (analogous to fission releasing more neutrons)


None that I know of. A muon has a mass of 106 Mev, which is more than any of the fusion reactions of light elements. From Wikipedia Only nuclear fission produces single-nuclear-event energies in this range, but does not produce muons as the production of a single muon is possible only through the weak interaction, which does not take part in a nuclear fission. They are also hard to slow down. They have been used to "X-Ray" the pyramids of Egypt.

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PostPosted: Oct 27, 2014 11:37 pm 
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In the 20th century there were many mind blowing scientific discoveries and inventions that radically changed the way we live and the way we perceive the world around us. In this century we will have many such events, and I feel we are headed for a cluster of such dramatic events created by a critical mass of accumulated information and the lighting speed at which that information is communicated around the world. The discovery of the neutron was a big deal in the last century. In this century the discovery of nanoscale magnetic fields and other natural phenomena will alter our understanding of physics. Expect radical new technologies instead of being surprised by them. They are predictable by the mathematics of our situation and position in history. If you live in an old mental box created in the 20th century, you will not be able to see what is going on now.


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PostPosted: Oct 31, 2014 6:24 am 
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I'm trying to figure out the first wall neutron damage problem of the Lockheed concept.

Here's some figures I found:

PWR vessel lifetime dose: 3x10e23 n/m2
ITER first wall dose rate: 3x10e18/nm2/s

So, the ITER vessel will receive a neutron dose equivalent of a lifetime of a PWR vessel, every full power day. How long is that going to last?

Presumably these figures don't consider that D-T fusion neutrons are much faster than the PWR dose?

Anyway, Lockheed's concept should be about 10x higher if it were the same size as ITER, because its smaller it might be 3-5x perhaps? Anyone have a precise figure?


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PostPosted: Oct 31, 2014 7:56 am 
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The following source has a high end peak of 10e15 n/m2/s for PWR, resulting in 10e-9 dpa/s.

http://aprs.ornl.gov/~webworks/cppr/y20 ... 117080.pdf

So this is a relative displacement rate of 1 dpa per 10e24 neutrons.

What is the displacement rate for unmoderated D-T fusion neutrons?


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PostPosted: Oct 31, 2014 12:21 pm 
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Isn't neutron embrittlement of the pressure vessel the primary problem with PWR pressure vessels?
This isn't much of an issue for ITER as the pressure vessel is under a drastically reduced loading.

The big problem appears to be neutron flux killing the superconducting magnets - that is what you have to calculate.


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PostPosted: Oct 31, 2014 5:46 pm 
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Embrittlement is about loss of ductility which is independent of loading.

Magnets are definately a problem but you can put neutron shielding and insulation in front of them. First wall must pass all neutrons plus can't be insulated.


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PostPosted: Oct 31, 2014 6:00 pm 
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Yes it is independent of loading but overbuilding the pressure vessel is easier due to the lower pressures. Shielding 14MeV neutrons from getting to the magnets is far more challenging.


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PostPosted: Oct 31, 2014 6:57 pm 
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E Ireland wrote:
Yes it is independent of loading but overbuilding the pressure vessel is easier due to the lower pressures.


Doesn't matter. A non ductile vessel is a non ductile vessel. Big chunk of glass is still glass.

The high thickness for PWRs is actually an advantage. It results in much self shielding of neutrons. This isn't available with fusion first walls.

If the neutron flux is say 10000 times higher than PWR vessel plus maybe 100x higher displacements from the much higher neutron energy, then that's 1 million times more damage. That's a problem.


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PostPosted: Oct 31, 2014 7:24 pm 
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It doesn't matter if its a big chunk of glass when there are no mass loadings on its structure. It's not having to hold back 200atm water with crazy boiling pressure transients.
Its quite feasible to design a reactor where the pressure boundary is far far away from the neutron flux.


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PostPosted: Nov 01, 2014 2:50 am 
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E Ireland wrote:
It doesn't matter if its a big chunk of glass when there are no mass loadings on its structure. It's not having to hold back 200atm water with crazy boiling pressure transients.
Its quite feasible to design a reactor where the pressure boundary is far far away from the neutron flux.


The first wall is a containment for tritium and blanket fluids/coolants. The thermal and fluid loadings are very significant.

The transient loadings are also substantial. In case of magnet failures, the first wall must retain tritium and plasma pressure transient for a reasonable amount of time.

Good luck trying to get a brittle containment licensed.


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PostPosted: Nov 01, 2014 4:43 pm 
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Is there any sort of self-annealing alloy that might work, or would that much atom mobility make it too soft and susceptible to creep?


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PostPosted: Nov 01, 2014 5:53 pm 
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Creep isn't a problem if it only comes under significant loads during a quench scenario.

Blanket fluids can be run at subatmospheric pressures if neccesary.


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PostPosted: Nov 01, 2014 5:56 pm 
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Titanium48 wrote:
Is there any sort of self-annealing alloy that might work, or would that much atom mobility make it too soft and susceptible to creep?


Annealing requires high temperatures, at which the neutron damage increases more rapidly than annealing can heal it. This is true for fission neutrons so will be even more true for the faster D-T fusion neutrons.

But it may be possible to anneal out the damage in offline annealing runs like the British gas cooled reactors did.


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PostPosted: Nov 01, 2014 6:01 pm 
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E Ireland wrote:
Creep isn't a problem if it only comes under significant loads during a quench scenario.


The problem there (accidents/transients) will be pneumatic and thermal shock or even vaporization of the first wall. It is 100+ million degrees plasma after all.

Quote:
Blanket fluids can be run at subatmospheric pressures if neccesary.


I don't see how, there's hydrostatic pressure from the heavy FLiBe or the even heavier Pb-Li, plus there's pumped pressure.

The first wall has to retain large amounts of tritium in accidents, too.

What happens if you have 150 million degree plasma held together by super powerful magnets, and the power goes out? What is the thermal and pneumatic shock? What happens to all the tritium?


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