6 thoughts on “Space Nuclear Power”

  1. “However, commercial entities are better suited to developing LEU designs and LEU designs could be cheaper in the long-term.[20]”

    [20] Powis, Andrew, and Frank von Hoppel. “How Will a NASA Decision on Low vs High Enriched Uranium for a Nuclear Fission Space Power Reactor Effect the Commerical Sector?” Nuclear and Emerging Technologies for Space, 2020.

    Okay, this kind of krapp really bugs me. I took the time to dig up and read the reference and the take is that it is easier for commercial entities to develop LEU for a host of federal regulatory reasons and international policies. In my mind, that is far different from being “better suited.” The US entities likely to undertake this work are all DoD and DoE contractor with deep experience in developing compact HEU reactor system. Yes, there are some interesting small companies dabbling in LEU but I don’t see them getting a lot of the initial work.

    For those who want to read it, starts on pg 68 – https://nets2020.ornl.gov/wp-content/uploads/2020/09/TRACK-3-Full-submission.pdf

  2. A low-enriched-uranium reactor has to be far heavier to form a critical mass. Tens of tonnes at least. A highly enriched uranium reactor can be (depending on how dangerously you want to live) as small as a softball.

    LEU is pretty crippled for spacecraft propulsion applications, where the mass really matters.

    1. More like 4 tonnes, for a heavy water moderated reactor using natural uranium (e.g. CANDU).

      Really, the nuclear cycles available are endless. The Oak Ridge people studied over 1,000 possible cycles for both military and commercial nuclear reactors. Pressurized water was selected only because of the minimal enrichment required (a cost consideration only). U.S. Navy nuclear vessels use 95%+ enriched uranium, so they can go unrefueled for 25 to 30 years – the life of a capital ship. But it costs a LOT of money, in terms of both enrichment and security.

      Space nuclear offers an even broader array of choices. Oddly enough, one of them is the availability of solar power. Accelerator driven reactors, powered by solar arrays, can achieve tremendous gain factors even with fuels such as depleted uranium or natural thorium (over time). In fact, space solar power for terrestrial applications would probably be best provided by accelerator-produced isotopes (e.g. polonium 210) which could then be sent back to Earth in compact entry vehicles.

      This is a very rich field for development, provided the government doesn’t get in the way – which it undoubtedly will.

      1. Is accelerator-produced isotope generation a storage option for ground-based solar? I mean, leaving out the hand-wringing about nuclear fission. Or do you need a steady source of electricity to run the accelerators, either for the time to achieve steady-state operation or for economic reasons?

        1. No, you could do it with ground-based solar (or wind). But neither is very economical, and both are terrible environmentally.

          Space-based accelerators would have tremendous engineering advantages, and would be able to operate 24/7/365 – even topping ground-based nuclear or coal plants.

          There a a lot of isotopic choices for energy storage, and no particular need to settle on just one. Polonium 210 is hideously toxic, but has prodigious energy output as it decays to the absolutely benign, stable lead 206. There are many other isotopes having a variety of half-lives (i.e. specific power output), and stable end-states.

          1. What you’re describing is essentially the basis for the 1954 juvenile novel “Tom Swift and His Outpost in Space.” The Outpost (it never had a name) was constructed from a hub and 12 wetlabs (upper stage fuel tanks). It did some research, but it’s primary purpose was to produce energy dense, solar charged “atomic batteries” to be sold by Swift Enterprises. Depleted batteries were brought back up in one of the Swifts’ fully reusable 4-stage cargo rockets. The batteries were used to power things like the Jetmarine, Atomic Earth Blaster, and Diving Seacopter.

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