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NASA to test prototype Kilopower nuclear reactor

world-nuclear-news.org

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Re: NASA to test prototype Kilopower nuclear reactor

#31

Post by raverbashing »

yborg wrote: post #21
curtis wrote: post #6

This is similar to the "Stirling radioisotope generator" [1] but it is an actual nuclear reactor (albeit a small one). Both systems are a response to the same fundamental problem, the dwindling supply of Plutonium-238 [2]. The Stirling radioisotope generator uses Pu-238 more efficiently than thermoelectric RTGs, and the nuclear reactor from the article dispenses with Pu-238 altogether. [1] https://en.wikipedia.org/wi…

The problem with Stirling engines is they have moving parts. It's highly unlikely a Stirling cycle generator on the Voyagers would have operated for 40+ years as their RTGs have.

Yup, I wonder how they can guarantee the engine will keep turning for 10 years even. Maybe if everything is sealed in a (very long) lived lubricant that stands the harshness of space?

Still hard to imagine

Re: NASA to test prototype Kilopower nuclear reactor

#32

Post by bildung »

rwcarlsen wrote: post #27
sp332 wrote: post #25

Earlier quoted context omitted.

It's because sometimes a rocket explodes on the launch pad or a few seconds later, and it could spread radiactive material over a very wide area.

The half-life of fuel for these reactors is very long - over 100,000 years. So for all practical biological effects they are basically stable. If it exploded before it was activated (far into space), it would be about the same danger to people and the environment as the rest of the exploding metal the rocket was made of.

The half-life of the currently used fuel (Plutonium 238) is 87 years.

Re: NASA to test prototype Kilopower nuclear reactor

#35

Post by rm445 »

raverbashing wrote: post #31
yborg wrote: post #21

Earlier quoted context omitted.

The problem with Stirling engines is they have moving parts. It's highly unlikely a Stirling cycle generator on the Voyagers would have operated for 40+ years as their RTGs have.

Yup, I wonder how they can guarantee the engine will keep turning for 10 years even. Maybe if everything is sealed in a (very long) lived lubricant that stands the harshness of space? Still hard to imagine

That's the usual way things are done. If you buy for instance a simple 5:1 gearbox for industrial use, it will quite likely be a sealed casing 'greased for life'.

Not that I'm disagreeing with you really - mechanical devices have high failure rates. 10 years maintenance-free is a bit of a dream. As a mechanical engineer I'm interested to see whether the Stirling engines involved have radically different scaling to optimise for reliability, or NASA just plan to do the engineering really well.

Of course manned maintenance may be possible - they are touting this technology for Mars bases. Plus robotic maintenance is going to become more of a thing over time.

Re: NASA to test prototype Kilopower nuclear reactor

#36

Post by jlebrech »

GlenTheMachine wrote: post #8

This is a very cool technology, but frankly I have a hard time imagining that it will see much use. NASA sees public protests and scare mongering whenever it tries to fly an RTG, which is based in the radioactive decay of (usually) plutonium, and does not use a nuclear chain reaction. They did fly one on Mars Science Lab, because it was the only way to get enough power for the rover. But it takes a PR hit every time…

they should be indoctrinating kids at school that nuclear is safe, rather than other "stuff" they tell them nowadays

Re: NASA to test prototype Kilopower nuclear reactor

#37

Post by Faaak »

gozur88 wrote: post #17
curtis wrote: post #6

This is similar to the "Stirling radioisotope generator" [1] but it is an actual nuclear reactor (albeit a small one). Both systems are a response to the same fundamental problem, the dwindling supply of Plutonium-238 [2]. The Stirling radioisotope generator uses Pu-238 more efficiently than thermoelectric RTGs, and the nuclear reactor from the article dispenses with Pu-238 altogether. [1] https://en.wikipedia.org/wi…

The other problem with RTGs is they scale very badly.

how ?

Re: NASA to test prototype Kilopower nuclear reactor

#38

Post by baybal2 »

nickhalfasleep wrote: post #2

Thermo-acoustic stirling engines have long been a niche product. Seems like a great environment for them to shine, and far better efficiency than RTG's.

Another thing to mention is sodium/lithium salt thermochemical generators that run at 15 percent efficiency with liquid salt being the only moving part

Re: NASA to test prototype Kilopower nuclear reactor

#39

Post by wiredfool »

jlebrech wrote: post #34

the cold of space and the heat of a nuclear reactor would be the perfect combination for a peltier reaction. not very good for a rover though.

Space is cold, but there's not much there, so your flux will be very small. Of the three ways to move heat (radiation, convection, and conduction) you're basically reduced to radiation, which is the least efficient.

Re: NASA to test prototype Kilopower nuclear reactor

#40

Post by gruturo »

jlebrech wrote: post #34

the cold of space and the heat of a nuclear reactor would be the perfect combination for a peltier reaction. not very good for a rover though.

cold of space? Unfortunately, no - space is an extremely effective insulator, so it's extremely difficult to get rid of heat. You need large heat sinks (which adds weight) and they have piss-poor efficiency in space. So your cold side would get hot very quickly
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