NASA completes full-power tests of small, portable nuclear reactor • Hacker News Board

Re: NASA completes full-power tests of small, portable nuclear reactor

#31

Post by nerdponx » Thu, May 03, 2018, 4:55 PM UTC

syntaxing wrote: post #7

For those curious, this uses a nuclear reactor to power a Stirling engine.Stirling engines are a good choice because there is no mass transfer to create the work (i.e. no fuel needed, just heat). It only needs a temperature differential and sealed gas/liquid to work. I highly recommend to read more about Stirling engines since they are of one the most efficient form of work generation with just a temperature differen…

Funny this should come up today. Just last night I was wondering why we don't have better technology for learning how to turn heat into electricity.

Re: NASA completes full-power tests of small, portable nuclear reactor

#32

Post by linuxguy2 » Thu, May 03, 2018, 5:03 PM UTC

zaroth wrote: post #10

rbanffy wrote: post #2

I wonder if it can operate in zero g...

That is in fact precisely what it is designed for.

Isn't it actually designed for working on Mars? Convection in the sodium heat pipes wouldn't work in zero G.

> generate heat that is carried to the Stirling converters via passive sodium heat pipes.

https://en.wikipedia.org/wiki/Kilopower

Re: NASA completes full-power tests of small, portable nuclear reactor

#33

Post by mkoryak » Thu, May 03, 2018, 5:05 PM UTC

I wonder how safe these are. Could I get one in my basement and stop paying nstar for the rest of my life? Would my neighbors complain much?

Re: NASA completes full-power tests of small, portable nuclear reactor

#34

Post by Thorazul » Thu, May 03, 2018, 5:09 PM UTC

They should team up with Tesla to develop storage batteries for the reactors in case a reactor fails you would still have some temporary emergency power.

Re: NASA completes full-power tests of small, portable nuclear reactor

#35

Post by darken » Thu, May 03, 2018, 5:09 PM UTC

dukoid wrote: post #18

Sir_Substance wrote: post #16

Earlier quoted context omitted.

Passive decay is still fission, it's just not artificially sped up fission :) it's probably more complex than that. Is high speed natural decay of an artificially created or enriched heavy element natural or artificial? I'm not sure how that gets classified.

My bad, I had assumed fission was splitting atoms by adding neutrons, but actually fission is just the "splitting" part, so both cases are indeed fission....

The fission process releases neutrons, so you effectively "add neutrons" by concentrating self-fissioning material in a small space.

To put another way: If you increase the size of a sphere of fissionable material, its rate of "natural" decay stays the same, but more of these decays lead to neutrons triggering additional fission reactions. So doubling the size of the sphere leads to >>2x fission events due to neutrons having more fissile material to hit on the way out.

A large fission reactor is just a scaled up version of this with control rods to adsorb extra neutrons to control secondary "induced" fission.

Re: NASA completes full-power tests of small, portable nuclear reactor

#36

Post by mehrdadn » Thu, May 03, 2018, 5:16 PM UTC

netzone wrote: post #4

What would the effects be of releasing nuclear waste in space? Could we sent up all of our nuclear waste, put a rocket on it and just let it disappear into the distance?

Note that you'd want to go beyond the escape velocity or you'll just put it in some orbit. I'm not sure how practical that is, keeping in mind costs.

Re: NASA completes full-power tests of small, portable nuclear reactor

#37

Post by forkandwait » Thu, May 03, 2018, 5:16 PM UTC

So... Are plans available anywhere?

Re: NASA completes full-power tests of small, portable nuclear reactor

#38

Post by forapurpose » Thu, May 03, 2018, 5:20 PM UTC

What are the other uses for this? Civilian power? Military applications?

Re: NASA completes full-power tests of small, portable nuclear reactor

#39

Post by jabl » Thu, May 03, 2018, 5:23 PM UTC

mkoryak wrote: post #33

I wonder how safe these are. Could I get one in my basement and stop paying nstar for the rest of my life? Would my neighbors complain much?

The black helicopter people might arrive and have a nice chat with you when they discover you ordered a bunch of HEU from aliexpress.

Re: NASA completes full-power tests of small, portable nuclear reactor

#40

Post by asteli » Thu, May 03, 2018, 5:25 PM UTC

linuxguy2 wrote: post #32

zaroth wrote: post #10

Earlier quoted context omitted.

That is in fact precisely what it is designed for.

Isn't it actually designed for working on Mars? Convection in the sodium heat pipes wouldn't work in zero G. > generate heat that is carried to the Stirling converters via passive sodium heat pipes. https://en.wikipedia.org/wiki/Kilopower

The wiki page you linked specifically mentions deep space applications as a design goal.

I'm not sure about the sodium heat pipes but the alcohol vapor heat pipes you see in electronics typically use an internal wick to return the working fluid.