Americium: How a long-life nuclear fuel will transform space travel
interestingengineering.com
Americium, a much more common element, may replace plutonium in long-life nuclear batteries, powering spacecraft for centuries.

“The isotope of interest for space is americium-241…Its half-life is a staggering 432 years, five times longer than plutonium-238.”

  • treadful@lemmy.zipEnglish
    25·
    24 days ago

    In the UK, large stocks of civil nuclear waste contain significant quantities of americium-241. That makes the fuel not only long-lasting but also readily accessible. Instead of building new reactors to produce plutonium, agencies can extract Americium from existing waste, a form of recycling at a planetary scale.

    Using it seems way more preferable to just letting it sit in casks.

    Traditional RTGs utilize thermoelectrics, which are reliable but inefficient, often achieving only five percent efficiency. Stirling engines can convert heat to electricity with an efficiency of 25 percent or more. […] Stirling engines introduce moving parts, which also raises reliability concerns in space. However, Americium’s steady heat output enables RTG designs with multiple Stirling converters operating in tandem. If one fails, the others compensate, preserving power output.

    That seems a little ridiculous though. All that friction requires a lube that’ll last “generations.” In space, without gravity, and at incredibly low temperatures.

    • rowinxavier@lemmy.worldEnglish
      5·
      24 days ago

      Yeah, but there are many good options. Magnetic alignment can keep things from touching most of the time, maintaining very good movement without friction. Graphite is a great lubricant and works even in very cold environments, not to mention it will not be all that cold given the heat passing through the system. Redundancy is also a big part of the design, making failures much less impactful. And using sterling engines for the highest draw part of the lifetime of a probe with peltier style generators there for later would allow a failover to a solid state system at lower efficiency.