I recently learned about traveling wave reactors (TWRs) on the Netflix Bill Gates special, as an example of a cutting-edge technology Gates is funding which has the potential solve several environmental problems.

The TWR is a nuclear fission reactor which sounds a bit too good to be true (via Wikipedia):

  • Uses spent fuel from other fission reactors, meaning it doesn't require mining of new uranium
  • Consumes the spent fuel from these reactors, meaning it could be used to dispose of this nuclear waste
  • Doesn't produce any of its own toxic byproducts
  • Can run in containment for decades, with no need to add/remove fuel, reducing operational costs and risk to operators

So, what gives? Why don't these exist yet? The Wikipedia article (and the Netflix special) mention some political challenges that have delayed construction of a demonstration reactor, but I wasn't able to find any additional detail on technical challenges.

Like fusion reactors (which have both political and financial support, and never seem to get any closer to existing), I assume there must be some specific, unsolved technical challenges.

  • 1
    $\begingroup$ Bill Gates, which has tirelessly been working on advancing this to generate cheap power for poor communities had a contract with China to build a small scale working prototype. But Trump has basically torpedoed the project. $\endgroup$
    – kamran
    Feb 18, 2020 at 0:08
  • $\begingroup$ This Stanford coursework references a few scientific articles in peer-reviewed journals. The problem seems to be that most of the research is published by TerraPower themselves. $\endgroup$
    – sba222
    Jul 27, 2020 at 8:14
  • $\begingroup$ I'm particularly interested to which degree the technology depends on non-renewal resource inputs. $\endgroup$
    – sba222
    Jul 27, 2020 at 8:18

1 Answer 1


I am not aware of any technological challenges. There have been several sodium fast reactors that have operated, the latest being the Experimental Breeder Reactor II (EBR-II) in Idaho and the Fast Flux Test Facility (FFTF) in Washington. The next step in the development is to build one and gain operational experience.

I think the answer you are looking for is "cost". These reactors will be first-of-a-kind builds and will be expensive, much more expensive alternative methods of generating electricity. The only realistic way for one to be built is if the government funds it as a research project, and it just isn't a high priority right now.

For it to be a higher priority, it needs to solve an urgent problem. There are currently cheaper ways to generate electricity, so this isn't a driver. Uranium is cheap right now, so there isn't a need to develop a breeder reactor. People talk about nuclear waste, but the reality is that it is accumulating at reactor sites without any major issues.

I personally would love to see one built, but there isn't currently a driver for spending the money.


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