Wednesday, June 10, 2015

Review of SuperFuel: Thorium, the Green Energy Source for the Future by Richard Martin

Nuclear reactors for power generation don't have to use uranium for fuel and water for coolant, the way that the 99 power reactors in the U.S., and the ones in the rest of the world, currently do. In fact, it's somewhat of a historical accident that reactors don't use a completely different fuel - thorium - and a completely different coolant, like molten salt or metal.

Wired reporter Richard Martin wrote SuperFuel in 2012 to advocate for a switch to liquid fluoride thorium reactors. Generating power with thorium is a hot topic, with advocates like Kirk Sorensen, and startups like Terra Power (which is backed by Myhrvold) all trying to push for a nuclear renaissance with a new fuel.

The advantages of thorium for power generation involve the fuel and the reactor design. A thorium reactor makes more efficient use of a fuel that is more abundant than uranium and generates less waste. The design has also better inherent safety: the negative temperature coefficient of reactivity provides negative feedback against meltdowns, the coolant is stable (does not react with water like sodium coolant, or break down to hydrogen at high temperature like water), and the reactor operates at close to atmospheric pressure because of the high boiling points of the coolant salts.

The disadvantage at this point is that it is starting to seem like we really don't have the energy crisis that it looked like we did from 2008-2011. In fact, the mentions of energy scarcity and global warming now seem really dated.

Some of the complex aspects of the LFTR reactor are a bit hand-wavy, vaporware type stuff. For example, the design of the reactor calls for a continuous reprocessing loop of the molten salt (to remove undesired decay products like xenon). Of course, this has never been tried at plant-sized scale; the testing has been limited to the laboratory.

But the more important question given the past two years' developments is: can it compete with the cost of utility scale solar? Checking some recent updates, we see utilities buying solar for around 5 cents per kwh. Another example is an Xcel energy exec saying that solar project was chosen on a strictly economic basis, without considering carbon emissions or renewable energy standards. Here's further examples of an unsubsidized solar price close to 5 cents per kwh.

Five cents (and falling) is dirt cheap, and it makes it hard to justify the enormous research and development cost that it would take to commercialize an entirely new reactor design and fuel cycle.

The book functions best as an example of path dependence. It was the desire to produce material for nuclear weapons that led to reactors initially using uranium, and it was the desire to use water to cool naval reactors (for obvious reasons) that prevented any other design besides light water reactors.

Last time we mentioned path dependence was in reference to the paper  "Portage: Path Dependence and Increasing Returns in U.S. History". Path dependence is a good concept that explains why many things are the way they are.

By the way, thorium also ties into the distress of rare earth producer Molycorp. Thorium is almost always found in the ores (like monazite) that contain rare earth metals. Thus, rare earth ore is slightly radioactive and a refining operation both has to separate the rare earths from the thorium and dispose properly of concentrated radioactive waste product.

3/5

3 comments:

Taylor Conant said...

Doesn't the US use uranium so it has material for bombs, not because its a good energy technology?

CP said...

Yes.

Notice I did say "The book functions best as an example of path dependence. It was the desire to produce material for nuclear weapons that led to reactors initially using uranium, and it was the desire to use water to cool naval reactors (for obvious reasons) that prevented any other design besides light water reactors."

Merry Christmas!

Taylor Conant said...

Oops, didn't read as closely as I should've, missed that part.