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NASA to test prototype Kilopower nuclear reactor

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Re: NASA to test prototype Kilopower nuclear reactor

#81

Post by pault »

tpurves wrote: post #23
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…

For anyone else wondering why Pu-238 is dwindling, from the linked wikipedia: “The United States stopped producing bulk Pu-238 with the closure of the Savannah River Site reactors in 1988.[12][13][14] Since 1993, all of the Pu-238 used in American spacecraft has been purchased from Russia. In total, 16.5 kilograms (36 lb) has been purchased but Russia is no longer producing Pu-238 and their own supply is reportedly r…

When I lived in Seattle I was sitting at a cafe one day and a government motorcade came down the street with an 18 wheel truck carrying a dumbell-shaped canister with a giant yellow nuclear symbol on the side. I've never been able to figure out what they were transporting. Does anybody here know what it might have been? It was post 9/11 so I was surprised they were still moving radioactive material on the surface streets of a major city.

Re: NASA to test prototype Kilopower nuclear reactor

#82

Post by acidburnNSA »

pault wrote: post #81
tpurves wrote: post #23

Earlier quoted context omitted.

For anyone else wondering why Pu-238 is dwindling, from the linked wikipedia: “The United States stopped producing bulk Pu-238 with the closure of the Savannah River Site reactors in 1988.[12][13][14] Since 1993, all of the Pu-238 used in American spacecraft has been purchased from Russia. In total, 16.5 kilograms (36 lb) has been purchased but Russia is no longer producing Pu-238 and their own supply is reportedly r…

When I lived in Seattle I was sitting at a cafe one day and a government motorcade came down the street with an 18 wheel truck carrying a dumbell-shaped canister with a giant yellow nuclear symbol on the side. I've never been able to figure out what they were transporting. Does anybody here know what it might have been? It was post 9/11 so I was surprised they were still moving radioactive material on the surface str…

Could be related to all the Navy nuclear stuff around town like the shipyard at Bremerton or the Bangor sub base

Re: NASA to test prototype Kilopower nuclear reactor

#83

Post by acidburnNSA »

masklinn wrote: post #50
andygates wrote: post #47

Earlier quoted context omitted.

They're very low power, make a lot of waste low-grade heat, and use an inefficient electricity generation approach.

> make a lot of waste low-grade heat That's probably the biggest issue for deep space it's extremely difficult to shed heat in hard vacuum (without ejecting mass and its heat with it) as you can only radiate it away.

And radiative heat transfer scaled with temperature to the fourth power so it would be easy to do if you had materials that could handle really high temperatures for long times.

Re: NASA to test prototype Kilopower nuclear reactor

#84

Post by acidburnNSA »

matt4077 wrote: post #52
TeMPOraL wrote: post #43

Earlier quoted context omitted.

Totally. You're probably catching downvotes from people offended by "indoctrination", but a) indoctrination is what schools do, that's their purpose, and b) nuclear is actually pretty safe. I agree with the sentiment. Anti-science sentiments proliferate partly because science doesn't spend much on public outreach, especially compared to people who want to make a buck off scaring others about new technologies. NASA ha…

In your zeal to defend nuclear energy, you're come around full circle, defending something indefensible, with arguments far removed from actual science. Nuclear energy may be safe, if done under near-perfect condition, with extremely large budgets to understand risks, and plans to mitigate incidents. There is truth to the argument that nuclear power saves lives compared to coal power. But nuclear power isn't inherent…

The models we use to guess dose vsm health are linear with no threshold and we chose this to be conservative in lieu of real low dose data. Since then there has been zero conclusive evidence that low dose radiation causes any harm at all. The people who live in very high natural background level areas have never been shown to have higher incidence of anything that could be linked to the radiation. The body has error correcting repair mehcanisms that can handle a lot.

Re: NASA to test prototype Kilopower nuclear reactor

#85

Post by Manglano »

pault wrote: post #81
tpurves wrote: post #23

Earlier quoted context omitted.

For anyone else wondering why Pu-238 is dwindling, from the linked wikipedia: “The United States stopped producing bulk Pu-238 with the closure of the Savannah River Site reactors in 1988.[12][13][14] Since 1993, all of the Pu-238 used in American spacecraft has been purchased from Russia. In total, 16.5 kilograms (36 lb) has been purchased but Russia is no longer producing Pu-238 and their own supply is reportedly r…

When I lived in Seattle I was sitting at a cafe one day and a government motorcade came down the street with an 18 wheel truck carrying a dumbell-shaped canister with a giant yellow nuclear symbol on the side. I've never been able to figure out what they were transporting. Does anybody here know what it might have been? It was post 9/11 so I was surprised they were still moving radioactive material on the surface str…

To some extent we are radioactive material on the surface streets of the major cities, because we have consumed soil!! Even our steel tools can be somewhat radioactive, refinement concentrates point sources.

However, containment vessels like that are usually for refined ores, which end up in reactors, smoke detectors, medical devices, radiotherapy machines, you name it. Too expensive and possibly hazardous to airlift.

As far as I know, production of atomic weapons has stopped in this country and we're not even sure if they still work (half-lives--they rot). Could've been materiel for a stewardship program at the Hanford Site, or waste being evacuated from the Hanford Site.

Generally speaking, the remaining atoms transported and transmuted are for peace. That's why Russia brokers Uranium to the States, and why people in Kazakhstan and elsewhere continue to mine fissile ore.

If you were to shut down the remaining fission plants of Planet Earth, civilization as we know it, would end almost immediately, such is our need for these fuels. It would not be pretty--consider the amount of electric heat, the number of electric stoves with 50+ year duty lifetimes. That's why Japan recycles spent fuel at the French reactor.

Re: NASA to test prototype Kilopower nuclear reactor

#86

Post by acidburnNSA »

monob wrote: post #48
hutzlibu wrote: post #45

My first thought was "deep space mission". But because of moving parts involved, this is probably not the use-case. So a bit OT, I was wondering if anyone has yet thought about the solution of still using solar panels for them, but to also use a mirror to focus more light in the direction of the probe or a laserbeam? I mean, theoretical I don't see why not, appart from being more expensive? Andd you could also offset…

Inverse square law. Every n AU you go out from the earth you will need n 2 are of mirror to focus on a solar panel to get the same power. That assumes you can even build a structure that can keep that shape. Say you have a mission to Uranus, you will need a mirror with 400 times the area of the solar cells to get as much power as they would in earth orbit.

I made a cool plot of this in the solar system the other day.

https://whatisnuclear.com/img/solar-system-insolence.png

Re: NASA to test prototype Kilopower nuclear reactor

#87

Post by lloyd-christmas »

Manglano wrote: post #80
tpurves wrote: post #23

Earlier quoted context omitted.

For anyone else wondering why Pu-238 is dwindling, from the linked wikipedia: “The United States stopped producing bulk Pu-238 with the closure of the Savannah River Site reactors in 1988.[12][13][14] Since 1993, all of the Pu-238 used in American spacecraft has been purchased from Russia. In total, 16.5 kilograms (36 lb) has been purchased but Russia is no longer producing Pu-238 and their own supply is reportedly r…

US production has resumed, according to Wikipedia, as Cobalt 60 is coproduced and useful for medical sterilization. As an aside: There are some people who are very skeptical of both atoms and space exploration. I'm not sure what their motives are but given the amount of steel necessary to produce wind turbines, I'm unconvinced that "renewable" is actually "greener."

"over 20 years, a three-megawatt wind turbine can deliver 80 times more energy than is used in its production and maintenance." [0]

Beyond that, Steel is 100% recyclable^, and that accounts for over 65% of US steel production. Recycled steel can be done in arc furnaces, requiring no coal coke. [1]

Info like this is at the tip of your fingers.

[0] https://www.worldsteel.org/en/dam/jcr:f07b864c-908e-4229-9f9...

[1] https://seekingalpha.com/article/3785906-metallurgical-coal-...

^ This rate is never achieved. Global average is ~90%, as some countries aren't efficient: http://www.steel.org/sustainability/steel-recycling.aspx

Re: NASA to test prototype Kilopower nuclear reactor

#88

Post by wbl »

dvdkhlng wrote: post #72
lholden wrote: post #66

Earlier quoted context omitted.

The 40+ years the Voyager probes have stuck around for is impressive... but the actual primary mission duration was about 12 years (for Voyager 2), and that was with two (planned but not guaranteed) extensions for Uranus and Neptune. The RTGs on both probes have decayed A fair amount at this point and are producing a lot less power. 10 years may seem short, but combined with an electrically powered thruster there is…

If you want to use the RTG to power thrusters, then I'd think that doing the "detour" via a stirling engine to create electrical current to turn into thrust might be unnecessary. There must be some way to directly turn radioactivity (or heat) into thrust with sufficiently high exhaust velocity!?

Let me introduce you to the NERVA rocket. Nuclear thermal propulsion exists, but it's a real pain to make work and they had to search for coatings that could stand the heat and fuel.

Re: NASA to test prototype Kilopower nuclear reactor

#89

Post by wbl »

acidburnNSA wrote: post #83
masklinn wrote: post #50

Earlier quoted context omitted.

> make a lot of waste low-grade heat That's probably the biggest issue for deep space it's extremely difficult to shed heat in hard vacuum (without ejecting mass and its heat with it) as you can only radiate it away.

And radiative heat transfer scaled with temperature to the fourth power so it would be easy to do if you had materials that could handle really high temperatures for long times.

But then your Carnot efficiency goes way down.

Re: NASA to test prototype Kilopower nuclear reactor

#90

Post by freeone3000 »

sp332 wrote: post #25
JumpCrisscross wrote: post #14

Earlier quoted context omitted.

Has anyone studied these protesters? My off-the-cuff sense is they’re mostly older environmentalists.

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.

Pretty much any uncontrolled explosion propels highly toxic material over a large area (rocket fuel is not lickable). I don't see how alpha radiation is inherently worse than hydrazine.
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