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NASA to test prototype Kilopower nuclear reactor

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Re: NASA to test prototype Kilopower nuclear reactor

#61

Post by dgoodell »

hutzlibu wrote: post #42
ChuckMcM wrote: post #30

Okay, this is awesome. 10kW is a serious enough amount of energy to do some fun stuff. Things like rovers that move at km/h rather than m/h and all day operation. It also solves the 'base load' problem on deep space missions which would like to use more power for radio communications.

"It also solves the 'base load' problem on deep space missions which would like to use more power for radio communications." Not really, since "moving parts" ...

One of the primary uses are deep space probes. The stirling engine has exactly two moving parts and uses non contact seals. In theory the lifetime should be limited by the deformation of the piston at elevated temperatures. Still, you’re right. They certainly have to do a lot of reliability testing to be able to show that these stirling engines will last 10+ years before they use them in a mission. They have several stirling engines that have been running for multiple years in simulated conditions for just this purpose at NASA GRC.

Re: NASA to test prototype Kilopower nuclear reactor

#62

Post by _0w8t »

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…

"nuclear is safe/unsafe" is meaningless unless we compare that with other technologies. Nuclear, despite all its nasty problems, is safer than many other technologies that are in wide use.

Consider coal electricity. It kills much more people globally than potential harm from space probes with nuclear engine blowing up in atmosphere periodically. Yet we continue to burn coal.

Or consider bio-engineering. We mess with cells without understand how they work. And since cells are self-replicating, we have a potential of quickly making the whole planet permanently unsuitable for human life. Compared with that the total risk of nuclear is bounded even after accounting for a possibility of a large-scale global nuclear war. Yet protests against, say, GMO are rather weak compared with protests against nuclear energy.

Re: NASA to test prototype Kilopower nuclear reactor

#63

Post by cptaj »

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…

Here's an episode of Space Policy from Planetary Radio. They go very in depth on the issue of pu-238, the efforts to restart production and why it is so complicated.

http://www.planetary.org/multimedia/planetary-radio/show/201...

Re: NASA to test prototype Kilopower nuclear reactor

#64

Post by 7952 »

TeMPOraL wrote: post #43
jlebrech wrote: post #36

Earlier quoted context omitted.

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

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…

I don't think people respond well to this kind of objective reasoning, it just doesn't work very well as an argument. At worse it can sound like you are calling them dumb. We need to explain the benefits, and why they are worth a tiny amount of risk. And accept that sceticism and concern are exactly what an intelligent layman should be exhibiting. Wondering if the thing is going to explode and cause cancer is a perfectly legitimate question to ask. To pursuade people you need to engage with them on an emotional level, not just bash them dismissively.

Re: NASA to test prototype Kilopower nuclear reactor

#65

Post by iliis »

More details in this german article: https://www.golem.de/news/kilopower-ein-kernreaktor-fuer-rau...

I'll summarize some of the interesting points:

- The nuclear core (75kg of enriched uranium/molybdenum [1]) is designed to not go critical, even if it accidentally falls into the sea and is surrounded by water (which is a good neutron reflector). It only starts when you surround it with a neutron reflector made of beryllium (an even better neutron reflector, mainly due to less absorbtion). Combined with the fact that the reactor only gets nasty when it's been running for a while (and thus is already far away from earth) it is a lot safer than plutonium fueled RTGs.

- It would be very useful to reach far away destinations (like the orbit of Uranus, Neptun or Pluto) using ion drives, as they need to run for years and solar panels aren't effective far away from the sun.

- While there have been other attempts at developing nuclear reactors for space, most of them didn't go far. They could use an existing research reactor (Flattop [2]) for this project which already has all the required permissions to run, so a lot of paperwork could be saved for the Kilopower experiments.

- The Kilopower reactor is the first to use heatpipes instead of pumps for the heat transport and stirling engines for the energy generation. The first experiment was thus to show that the cyclic heat draw of the stirling engine would be safe, because usually nuclear reactors reach an equilibrium between heating up (and thus expanding slighty which slows down the reaction) and cooling down (which accelerates the reaction).

- Instead of the planned eight 125W Stirling engines, they're currently using two 70W ones from the Advanced Stirling Converter Project [3]. The other ones will be simulated using simple heatsinks.

- Theoretically it could run for hundreds of years (after 500 years less than 1% of the uranium will be used), but the Stirling engines will break much sooner than that.

[1] http://www.iaea.org/inis/collection/NCLCollectionStore/_Publ...

[2] https://en.wikipedia.org/wiki/Flattop_(critical_assembly)

[3] https://tec.grc.nasa.gov/rps/stirling-research-lab/advanced-...

Re: NASA to test prototype Kilopower nuclear reactor

#66

Post by lholden »

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.

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 potential for doing types of missions we have not really been able to do before. That 10 years could be spent doing propulsion.

If you want to use it more in the science phase, use chemical rockets to get up to speed and then boot up the reactor in time to say, decelerate into orbit and you are looking at having the majority of that 10 years used at the destination.

My main concern isn't really the duration, but the reliability of the moving parts. But without plutonium, there are not a whole lot of other options for powering missions to Uranus and Neptune.

Re: NASA to test prototype Kilopower nuclear reactor

#67

Post by Filligree »

bildung wrote: post #32
rwcarlsen wrote: post #27

Earlier quoted context omitted.

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.

The article is about a reactor that does not use plutonium.

Re: NASA to test prototype Kilopower nuclear reactor

#68

Post by lholden »

andygates wrote: post #49
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 used to get protests back when Galileo launched, but I don't recall any for Curiosity. There's the soothing effect over time of a known technology not screwing up. Kilopower is safer, because it would launch inert, and it avoids Pu so any failures would be less toxic. Downplaying the usefulness of a technology because of imaginary protesters isn't very helpful.

I don't think New Horizons received any protestors either.

Re: NASA to test prototype Kilopower nuclear reactor

#69

Post by TeMPOraL »

7952 wrote: post #64
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…

I don't think people respond well to this kind of objective reasoning, it just doesn't work very well as an argument. At worse it can sound like you are calling them dumb. We need to explain the benefits, and why they are worth a tiny amount of risk. And accept that sceticism and concern are exactly what an intelligent layman should be exhibiting. Wondering if the thing is going to explode and cause cancer is a perfe…

I agree. I didn't mean bashing people, just addressing some of the more irrational worries confidently as non-issues.

The way I feel it, engaging with irrationality legitimizes it. You don't want to do that too much. If you bend over yourself to explain that people really don't need to worry, it'll only make them feel that there is something to fear.

What I want to suggest is engaging with people on an emotional level, but projecting confidence while doing so.

Re: NASA to test prototype Kilopower nuclear reactor

#70

Post by rijoja »

gambiting wrote: post #56
tobyhinloopen wrote: post #33

put it in a car

1kW isn't driving you anywhere though(even if we ignore all the dangers of having a nuclear reactor in a car). A typical automotive engine produces 100-300kW.

But it would be perfect for a well isolated home wouldn't it?
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