fusion as replacement for fossil fuels?

My grandfather (aka Uncle Bill) asked me if fusion power could replace fossil fuels. Here's my response....

Unk Bill,

You asked me if fusion can replace fossil fuel in our energy economy in the relatively near term (30 years). Below I’ll describe two candidate fusion machines. The first is a tokamak. It is unlikely to solve the problem because it’s too expensive. The other is the compact torus (CT). It is unlikely to solve the problem because a technological breakthrough is required. However, anything is possible, especially if enough research money is devoted to the challenge.

Tokamaks have received the vast majority of research effort in the past 50 years. With the tokamak, we have achieved “breakeven”, which that the ratio of fusion power out to electrical power in is one. For a commercial powerplant, this ratio should be about 10. If things go as planned, the International Thermonuclear Experimental Reactor (ITER) will achieve this desired factor of 10. However, tokamaks are incredibly complex and expensive engineering marvels. Superconducting magnets are required to produce the strong magnetic fields in tokamaks. Perhaps in 30-50 years, tokamaks can be made commercially competitive with coal plants, but not in the near term.

A sudden breakthrough in an innovative device called a compact torus (CT) is a long-shot possibility. The CT is similar to the tokamak, but is generally smaller and doesn’t require the superconducting magnets. One of the keys to the CT is that it allows the magnetic fields to relax naturally instead of using the high magnetic fields of a tokamak to force the plasma to behave. Consider bridge building: if an engineer wasn’t very crafty, he/she might just make the bridge deck very thick. However, a crafty engineer would use cables to suspend the bridge, thereby greatly reducing the cost of the bridge. The CT is the crafty engineer’s approach. CT development is far behind the tokamak in funding levels and in technological development. However, a breakthrough might yield a useful fusion powerplant in the next 20 years.

Now… if fusion can’t solve the problem alone, can it help somehow? Nuclear fission technology works, but has a radioactive waste problem. Nuclear fusion can help solve that problem. Fission produces radioactive isotopes. By bombarding the radioactive isotopes with neutrons, they can be transmuted into radioactively stabilized. Fusion produces lots of neutrons even if it doesn’t produce energy. With fission-fusion hybrid technology, we can employ those neutrons to deal with radioactive waste.

Many people don’t realize how much progress has been made in fusion! We routinely control plasmas and make fusion energy. Hydrogen (which can be obtained by splitting water) is the fuel for fusion. This is a technology that humanity will surely benefit from in the long run if not the short run.

Hope this sheds some light on the issue!

Eric

P.S. I’ve only talked here about magnetic confinement fusion which uses electromagnetic fields to trap plasma (hot charged particles). Another approach is to use lasers to compress a chunk of fuel. This idea also has some merit, but I think magnetic confinement is preferable, so I ignore laser compression here.