NaK Coolant Droplets - ..."orbital debris hazard in LEO"

Palomar · 2004-03-29 18:39:30

[http://www.space.com/news/mystery_monday_040329.html]Terrific

*I suppose someone may tell me this isn't as serious a matter as it sounds, but it certainly -does- concern me! :-\

A little quote: "Krisko explained that a study of the NaK coolant droplets circling Earth, floating about in varying sizes, is estimated to be 110,000 to over 115,000 in number."

And this nugget of comfort: "Old Soviet nuclear powered satellites leaked a trail of menacing radioactive droplets that have become a debris threat to other spacecraft."

Maybe we won't have to wait for crackpots in the Middle East to eject tons of gravel into LEO and mess up our future plans...

--Cindy

::EDIT:: Want to include these quotes too: "However, in ejecting the core from the main body of a RORSAT, a plumbing problem plagued the satellite design. Faulty seals permitted the NaK coolant to leak, leaving thouands upon thousands of droplets to spill freely in to space."

"There is evidence from ground-based radar measurements that 16 of a total of 31 RORSAT nuclear reactors orbited lost coolant following core ejection into disposal orbits."

SBird · 2004-03-29 18:58:20

Gee, small enough to be hard to track and big enough to do serious damage. Yet another Soviet legacy we've got to clean up after.

I've heard Germany's smuggling of Lenin into Russia in 1917 described as being akin to the importation of a plague. What an apt analogy...

Palomar · 2004-04-02 12:03:41

*This question keeps coming to mind since my original post, so what the heck...I'll ask:

"Tiny spheres of liquid sodium-potassium (NaK) reactor coolant..."

Just out of sheer curiosity, how is liquid sodium and potassium a coolant? I work in the medical field, so I'm especially curious. Any replies appreciated...thanks.

--Cindy

SBird · 2004-04-02 13:47:01

Both sodium and potassium melt at reasonably low temperatures. They can carry a lot of heat and so work great for a nuclear reactor. The efficiency of a thermodynamic system like a turbine power plant is largely goverened by the heat you run it at. The greater the temerpature differentials, the more efficient it works. Therefore, the steam driven power plants we use on Earth are quite inefficient, something like 30%, IIRC. You cant go higher in temperature because of the low boiling point of water and the tremendous presure and corrosion problems of handling it at high temperatures. The use of liquid metals helps tremendously. However, such a reactor is more expensive. Even more important, sodium and potassium, you'll recall from high school chemistry, burn on contact with water. Molten sodium and potassium explode on contact with water. On Earth, the rather ubiquitous presence of water makes them too dangerous to be considered most of the time. In space, though, there's no water to be worried about.

The Soviets used liquid metal reactors in some of their submarines. (despite the even greater amount of water in that case, the Soviet engineers figure that if water is somehow inside the submarine and mixing with the sodium in your reactor core, you've got a hole in your submarine and much more important problems to worry about.) We tried doing a liquid sodium readtor on the Seawolf submarine prototype but it was too problematic. Eventually, they had to cut the entire submarine in half and replace the reactor.

Bill White · 2004-04-02 13:55:37

Both sodium and potassium melt at reasonably low temperatures. They can carry a lot of heat and so work great for a nuclear reactor. The efficiency of a thermodynamic system like a turbine power plant is largely goverened by the heat you run it at. The greater the temerpature differentials, the more efficient it works. Therefore, the steam driven power plants we use on Earth are quite inefficient, something like 30%, IIRC. You cant go higher in temperature because of the low boiling point of water and the tremendous presure and corrosion problems of handling it at high temperatures. The use of liquid metals helps tremendously. However, such a reactor is more expensive. Even more important, sodium and potassium, you'll recall from high school chemistry, burn on contact with water. Molten sodium and potassium explode on contact with water. On Earth, the rather ubiquitous presence of water makes them too dangerous to be considered most of the time. In space, though, there's no water to be worried about.
The Soviets used liquid metal reactors in some of their submarines. (despite the even greater amount of water in that case, the Soviet engineers figure that if water is somehow inside the submarine and mixing with the sodium in your reactor core, you've got a hole in your submarine and much more important problems to worry about.) We tried doing a liquid sodium readtor on the Seawolf submarine prototype but it was too problematic. Eventually, they had to cut the entire submarine in half and replace the reactor.

SBird - do you have an opinion on using supercritical CO2 as a working fluid in a nuclear reactor?

Palomar · 2004-04-02 14:10:28

(despite the even greater amount of water in that case, the Soviet engineers figure that if water is somehow inside the submarine and mixing with the sodium in your reactor core, you've got a hole in your submarine and much more important problems to worry about.)

:laugh:

Thanks, SBird. You're fab. I appreciate the explanation.

--Cindy

SBird · 2004-04-02 14:12:53

I'm not qualified to answer that question. See if you can get GCNRevenger over here, he seems well versed in reactor design stuff. I know that he knows more than me, at any rate.

I'd guess that it's better than water but not as good as liquid metal.

On an aside, one thing that will really help Mars colonization is that we're rapidly going over to supercritical CO2 for much of our manufacturing these days. It turns out that lots of the sorts of processes that require lots of toxic organic solvents can be done with supercritical CO2 instead. Environmental concerns (and in some cases, economic benefits) have given a huge push to go over to CO2-based industry on Earth. This should be a great boon to future industries on MArs as the basic technologies will have been hammered out even before we get there.

SBird · 2004-04-02 14:15:34

You're fab.

Yep, that's me, Mod Squad all the way... :laugh:

dicktice · 2004-04-04 11:17:43

My take on orbital debris damaging vehicles in the approximately same LEO is that--as long as the rotational direction is the same--relative velocity differences will result in survable impacts using present structurally failsafe designs. (I assume there are international agreements already in place, to lways launch Eastwards.)

GCNRevenger · 2004-04-04 11:59:31

CO2 as reactor coolant? I think the gas was tried in a reactor in England, but didn't work very well. As for supercritical CO2, it isn't very stable at high temperatures you'd want to run a reactor at.

For space use, the current coolant of choice is probably a combination of sodium/potassium for the primary coolant and helium or helium mixed with other gasses for the secondary coolant. You can wring up to 33% efficency (which is pretty good) from a fairly light weight package. Just one drawback, it requires large radiators apparently.

All the old Soviet reactors used thermocouples or thermoionics for power generation. These can be run at high temp directly from the liquid metal coolant, cutting out the need for secondary low-efficency coolant, and has no moving parts. Unfortunatly they have one big achillies' heel... efficency. The best thermocouples can't break 10% and thermoionics probably can't top 12-15%.

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#1 2004-03-29 18:39:30

Re: NaK Coolant Droplets - ..."orbital debris hazard in LEO"

#2 2004-03-29 18:58:20

Re: NaK Coolant Droplets - ..."orbital debris hazard in LEO"

#3 2004-04-02 12:03:41

Re: NaK Coolant Droplets - ..."orbital debris hazard in LEO"

#4 2004-04-02 13:47:01

Re: NaK Coolant Droplets - ..."orbital debris hazard in LEO"

#5 2004-04-02 13:55:37

Re: NaK Coolant Droplets - ..."orbital debris hazard in LEO"

#6 2004-04-02 14:10:28

Re: NaK Coolant Droplets - ..."orbital debris hazard in LEO"

#7 2004-04-02 14:12:53

Re: NaK Coolant Droplets - ..."orbital debris hazard in LEO"

#8 2004-04-02 14:15:34

Re: NaK Coolant Droplets - ..."orbital debris hazard in LEO"

#9 2004-04-04 11:17:43

Re: NaK Coolant Droplets - ..."orbital debris hazard in LEO"

#10 2004-04-04 11:59:31

Re: NaK Coolant Droplets - ..."orbital debris hazard in LEO"

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