energywhiz | On 23, Nov 2013
File this one under Pseudo-Sustainable Energy.
Nuclear energy in any form isn’t technically sustainable, given all scenarios rely on a limited resource. Even a star like our Sun has a fixed, measurable amount of hydrogen to burn, and it’ll run out some 6 billion years from now.
When the ratio of energy density to fuel supply is high enough, we tend to look at the supply as essentially infinite. Such has been the concept of nuclear. If we could improve the technology of reactors, and do it so that safety and environmental concerns were all but eradicated, we could claim to have a pseudo-sustainable energy source.
We had heard about Bill Gates and Nathan Myrvold getting involved in nuclear a few years back, and the first reaction was… well… skeptical. Nuclear? Admittedly, our uninformed opinion was rash, and painted by biases against nuclear built up over 40 years of experience with it. But all said, we’re not the multi-billionaires who built one of the biggest technology companies in the world. And they aren’t stupid. So we decided to take a deeper look, give it the benefit of the doubt and educate ourselves.
After watching Gates’ 2010 Ted Talk on Energy, specifically touting the company he has helped found– TerraPower– we got a bit more curious given the premises upon which the company has been founded, which are in and of themselves defensibly logical. TerraPower proposes to reboot nuclear founded on tenets that include:
- Use Modern Technologies and Techniques
It is mostly true that for all intensive purposes, that serious, committed research into nuclear technologies ceased decades ago. A lot has happened technologically in those decades, and concepts and theories that could not be proven or tested then, can be now.
TerraPower seeks to perfect and deploy what they’ve coined as “traveling wave reactors”, or TWRs as their core technology. It is a technology posited in the 1950s and spuriously explored since. And TerraPower claims to have cracked the code on how to design and maintain a TWR platform.
Think of a log burning from its inside outwards over 50 years, constantly producing heat. At the beginning of the burn, a TWR requires a bit of enriched uranium (the U-235) to get the party started, but once burning, the core can ostensibly “breed and burn” it’s own fuel, making and consuming its own fuel, using the abundant U-238 as a primary fuel source.
- Use the 99% of Uranium as Fuel Instead of the 1%
Naturally occurring uranium has two primary components: Uranium-235 (U-235) and Uranium-238 (U-238). U-235 makes up around 1%, and U-238 the other 99%. Guess which one we use for fuel in current fission reactors?
Yep. The 1% is U-235.
The U-238 is considered waste and now vast quantities rest in stockpiles around the world.
TerraPower proposes to use those waste stockpiles of U-238 as fuel, which their calculations claim can provide hundreds of years of power. After which they plan to use raw naturally occurring U-238, which they claim will last a millenium.
- Closed Loop Fuel Cycle
TerraPower claims their TWR technology doesn’t require waste reprocessing. There is waste, but that it is produced in a closed system over a 40 to 50 year reactor core lifecycle and then comprises a small fraction of the original fuel core by volume; and there is no risky swapping in and out of fuel cells every 18 months or so, like typical modern reactors require. That is, the bulk of the fuel is “burned”, and it’s a fire-and-forget (for a few decades) operational proposition.
- Grid parity or below
TerraPower proposes to do all these things and produce energy at grid parity or better, as compared to carbon-based combustion fuel sources.
As we all now know from 3-Mile Island, Chernobyl and Fukushima, while on paper nuclear looks like a viable no-carbon energy source, when the current implementations of nuclear fission technology it go bad, they go *really* bad.
“Mining” is antithetical to sustainability. No matter how efficient the reactors, today the only way to get uranium is from destructive, environmentally unfriendly fashion. For EGW, this would be a non-starter if it wasn’t for the “sunk cost” already made in the essentially “undisposable” depleted Uranium waste product already here on the planet.
The pervasive nuclear technology in current nuclear plants involves fission of Uranium or Plutonium. In the most common Light Water Reactors, Uranium is used. Specifically, Uranium 235 (U-235). But the bulk of naturally occurring Uranium is the U-238, from which it is harder to unlock its energy potential. When processing Uranium from mines and then processed to be considered “enriched”, the U-238 is considered waste and stored in vast stockpiles. It is ironic that the waste is 99% of the Uranium mined.
Relying on a plentiful fuel source that is a toxic societal problem is compelling. Depleted uranium stockpiles in the United States weigh in at some 700,000 metric tons. While U-238 does occur naturally, the vast majority of available feedstock is left as a byproduct of the Uranium enrichment process. TerraPower has claimed that the Paducah enrichment facility stockpile alone represents an energy resource equivalent to $100 trillion worth of electricity. TerraPower has also estimated that wide deployment of Traveling Wave Reactors could enable projected global stockpiles of depleted uranium to sustain 80% of the world’s population at U.S. per capita energy usages for over a millennium.
If true, these are indeed world-changing numbers.
Further, it turns out that Uranium is an abundant element. Some 3ppm (parts per million) throughout the earth’s crust, about as common as tin or zinc. Our rivers naturally erode the uranium in the earth’s crust and carry it out to the ocean, where they estimate some 4 billion metric tons of Uranium. TerraPower claims that practical
Trust and Verify
Naturally, there are skeptics.
Some say the molten sodium they plan to use as a coolant is itself dangerous. It’s a great heat sink, but if that sodium meets water, bad things happen.
Others claim that it is more difficult that TerraPower is characterizing, or that if it is doable it will be far more expensive than Gates and crew are claiming.
We’re certainly not entirely convinced, either, but Gates, Myrvold and team are doing their homework. The concept and economics of employing the “99% of Uranium”– U-238– and deploying it closed-cycle, clean burning nuclear reactors that uses up existing stockpiles of toxic depleted Uranium-238 that we don’t really know what to do with? That deserves exploration.
And that’s sort of the meta-point, isn’t it?
While we’re not convinced that TerraPower’s TWR platform will be economically viable, we don’t have to be. And shouldn’t have to be. TerraPower’s core technology is an exemplar for the broader and deeper investment in “energy miracles” in which we should be engaged– the commitment to clever engineers working on big energy problems will breed-and-feed more investment, more risk taking, more commitment to visionary people taking on gigantic and worthy energy challenges that will change the world. They are providing pioneering leadership in (pseudo) sustainable energy research that will inevitably precipitate more of the same. The energy miracles to which Gates’ referred is the takeaway here. TerraPower and it’s notable stakeholders are feeding an R&D eco-system that creates that fertile ground from which energy technology miracles can and will sprout.
EGW feels Gates’ and crew would be better suited putting their money into developing storage technology “miracles”, or exploring massive scale truly renewable technologies that companies like Space Energy are pursuing; but if there are massive stockpiles of toxic, unwanted depleted uranium stored around the world– which there are– to deliver a hundreds of years of power to a billions of people in a relatively clean and sustainable fashion. That seems a worthy exploration.