Is My Idea Valid? Nuclear Fusion Power

[mfb]

You have to contain it in all three dimensions. One is easy in a torus (along the ring), the other two are not.
Note: that has nothing to do with pellets.

 

[Astronuc]

The first wall in a fusion reactor has to resist an aggressive environment including high temperature, high heat flux, and neutron/gamma radiation, as well chemical interaction. Ideally, it has high temperature and low atomic number (Z), since there is a change that the atoms on the surface can be knock off into the plasma, and high Z atoms result in energy losses due to recombination and brehmsstrahlung radiation.

The neutron irradiation has several effects: 1) radiation damage, i.e., atomic displacements in the lattice structure, 2) spallation reactions (e.g., (n,p), (n,d), (n,α)), and 3) activation. Neutrons knock atoms out of lattice sites, and in some metals, create voids. We measure displacements per atom. Neutrons knock out nucleons (spallation) or otherwise breakup small nuclei, and neutrons are absorbed and the nucleus transmutes by beta decay to a new element (Z+1).

Chemical effects involve hydrogen diffusion into the first wall, which can result in the formation of hydrides and blistering, where hydrides occupy greater volume than the bulk material. Blistering can produce flaking of the first wall, which finds it's way into the vacuum chamber causing impurities in the plasma, which increases the energy loss.

Austenitic stainless steel was an early candidate for Tokamak structural material, but austenitic alloys are subject swelling. Ferritic and martensitic steels resist swelling.

High temperature alloys and graphite are considered as well. Ceramics are also a possibilities.

http://en.wikipedia.org/wiki/Plasma-facing_material is a reasonably accurate article.

The challenge for materials increases with power density.

http://en.wikipedia.org/wiki/Alcator_C-Mod

 

[Mark Harder]

Another fascinating possibility is the Liquid Salt Thorium Reactor. India and China are sinking a lot of resources into engineering one of these. The idea has been kicked around since the '50s

That's not quite accurate. I checked with Wikipedia under Molten Salt Reactor Experiment (My underline.). People may have been thinking along this direction in the '50s. Alvin Weinberg might be called the father of the MSRE. He directed experimental molten salt reactor experiments in Oakridge, TN from 1964-1969. The original model used U-235 fluorides as fuel, and it did generate some plutonium. However, the fuel was later changed to Uranium-233. U-233 was generated in quantity in a separate reactor, and transferred to the MSRE. So it wasn't really a thorium reactor, since it didn't use Th as the primary fuel.

However, modern concepts still include breeding the initial charge of U-233 from Th-232 in a U-235 reactor. I don't know if U-233 can be made in an LFTR. LFTR designs make it easy to remove spent fuel and replenish with fresh fuel. Molten spent fuel is drained off and new molten fuel is pumped in. They also include a vital safety feature in the form of a solid plug in the liquid fuel line that melts if fuel temperatures get too high, draining the fuel into a separate containment vessel that passively quenches the nuclear reaction. There are disadvantages as well, and the projects are still controversial. Another information source is the Wikipedia article covering the 'Thorium Fuel Cycle', which covers these better than I can.

 

[Teen4Ideas]

High temperature alloys and graphite are considered as well. Ceramics are also a possibilities.

http://en.wikipedia.org/wiki/Plasma-facing_material is a reasonably accurate article.

The challenge for materials increases with power density.

http://en.wikipedia.org/wiki/Alcator_C-Mod

Is carbon fiber a viable candidate? Or carbon fiber layered on top of tungsten?

 

[Zackary Miller]

That's not quite accurate. I checked with Wikipedia under Molten Salt Reactor Experiment (My underline.). People may have been thinking along this direction in the '50s. Alvin Weinberg might be called the father of the MSRE. He directed experimental molten salt reactor experiments in Oakridge, TN from 1964-1969. The original model used U-235 fluorides as fuel, and it did generate some plutonium. However, the fuel was later changed to Uranium-233. U-233 was generated in quantity in a separate reactor, and transferred to the MSRE. So it wasn't really a thorium reactor, since it didn't use Th as the primary fuel.

However, modern concepts still include breeding the initial charge of U-233 from Th-232 in a U-235 reactor. I don't know if U-233 can be made in an LFTR. LFTR designs make it easy to remove spent fuel and replenish with fresh fuel. Molten spent fuel is drained off and new molten fuel is pumped in. They also include a vital safety feature in the form of a solid plug in the liquid fuel line that melts if fuel temperatures get too high, draining the fuel into a separate containment vessel that passively quenches the nuclear reaction. There are disadvantages as well, and the projects are still controversial. Another information source is the Wikipedia article covering the 'Thorium Fuel Cycle', which covers these better than I can.

You can make U-233 from Th-232 in a MSR, however that will produce Pa-233, which has a half life of 27 days and a neutron capture cross section > 1 for thermal neutrons, which necessitates constant reprocessing and thus increases the cost of operation as a reactor operator you have to both run a chemical plant and a reactor. Needless to say that could be quite expensive to do.

 

[DEvens]

It may require some sacrifice on the part of consumers. If you're interested in solving energy problems technologically, you could research the efforts put into more efficient and less polluting technologies, and don't neglect the social and economic issues such solutions create.

I am highly in favor of you making sacrifices. Especially economic and social sacrifices. It would be so nice if you would go first and show us what it's like.

The rest of us will go ahead and create the future.