OTA@S1-A@sri-unix (09/15/82)
From: Ted Anderson <OTA at S1-A> Date: Wed, 15 Sep 82 12:52:28 EDT From: dyer at NBS-VMS Subject: Reactors on the moon A moon-based reactor has all kinds of plusses going for it. You don't have to worry much about the safety features that are currently plauging the US's public utility reactors -- if there are no people around to be affected by a leak or meltdown, then who cares? The moon is an ideal enviroment for containing leaks because of the lack of atomosphere and prevailing winds to carry the gasses away. A lunar reactor could be /very/ minimal compared to earth-based reactors -- the best shielding might be six or seven miles worth of horizon, with the core and cooling system installed in a crater or pit. Set up a dozen or so 'throw-away' fast breeders on an otherwise empty plain. The reactors would be designed to last only five to ten years, and would be (comparatively) inexpensive. Every once in a while you switch fuel rods and process the plutonium, an operation that could also take place in an inexpensive lunar-based plant. Use the plutonium for mining, for power reactors, or for shoving asteroids around, a-la Dyson's ORION. Hopefully not for bombs. After ten years, or a melt-down, you bury the reactor with rock and moondust and spread radiation warning signs liberally around the area. Since the signs will probably stay around as long as the area stays hot (several million years?), future space-faring nations will be able to see that the burying-gound is an unhealthy place to dig. Gee, you could even have cheap waste-disposal: just launch waste cannisters with a mass-driver, so they would intersect the sun.... -Landon-
Ciccarelli@PARC-MAXC@sri-unix (09/16/82)
On Earth, nuclear reactors are (by some arguments) a cost-effective power source compared to alternatives. On the Moon, *no* such advantage exists when compared to the obvious competitor: sunlight. Consider the following criteria: [Generator site] Nuclear: If you build it "dirty" and unshielded (as suggested), its users must be some distance away, at least outside the crater. Solar: No site restrictions. Power is generated where needed, without long transmission lines. Move the power station when you need to; it's not "hot", large, or heavy (especially with photovoltaics). [Fuel] Nuclear: (a) Launch it from earth, *if* your citizens and the rest of the world don't object to the possibility of an unexpected "hot" shower if the launch vehicle fails, or (b) Find it (if it exists), mine it, and set up and power a separation plant on the moon (not worth considering). By the way there's the nasty detail of reprocessing breeder output. Presumably this involves robots or highly-paid humans, not to mention a plutonium remanufacture facility. Sounds complex... Solar: Spread a thin reflective sheet, or set up your photovoltaics! No hot waste to reprocess, either. [Electrical generator] Nuclear: (and Solar) could run a turbine (such a solar turbine has been proposed for an orbiting solar power satellite), but turbogenerators have to be shipped from Earth until you can make them "up there", and they have certain economies of scale (lower efficiency when made smaller). Solar: Photovoltaics would be much easier (than turbines) to make "locally", since no iron is involved and silicon is plentiful. They are usable in ANY size; just connect enough cells in series and/or parallel to provide the desired voltage and current. They have NO moving parts, aren't "hot", and are easily relocated. There's no downtime or power reduction during repairs since you can replace modules without shutting down others in the array. [Industrial process heat, i.e. for smelting and reduction of rocks] Nuclear: Heat can't be used directly without shielding (if you expect to have humans anywhere nearby...). This means electrical conversion (lossy) and reconversion to heat or RF. Why bother...? Solar: Easier than power generation; just aim mirrors at whatever needs the heat. Turns on and off instantly; not true for a reactor. ...Lastly, I abhor the "run it till it melts down, then bury it" school of engineering. The same goes for the "launch the wastes into the sun" suggestions. Why *create* these problems in the first place, when obviously better paths exist? I'll be damned if I'd like to be the 22nd-century lunar homesteader who happens to encounter your (oops, mistakenly unmarked) plutonium waste dump. /John
grunwald (09/17/82)
#R:sri-unix:-328000:uiucdcs:12700010:000:591 uiucdcs!grunwald Sep 16 18:38:00 1982 re: dumping wastes on the moon Somehow, some little voice inside my head says that if we dump all of our nuclear waste so close to home so soon, that in 5000 years, we'll wish we hadn't. Assuming people are still alive, the moon would have a much more key position for travel and whatnot. It would seem a shame to to that to such a nicely situated piece of rock. A better plan would be to be a little safer about it, and then cleanup and shoot the wastes into deep space (say at a near by star). Even if it takes a few centuries to get to the star, it wouldn't matter much in deep space.
mcdaniel (09/17/82)
#R:sri-unix:-328000:uiucdcs:12700011:000:589 uiucdcs!mcdaniel Sep 16 21:09:00 1982 However, Luna is a *B*I*G* rock! There is plenty of room for just about anything you'd like to do. Furthermore, unlike the earth, one spot is just about as good as any other (no weather, river, air pressure, etc. worries -- just land roughness, and that can be solved with a grader or by going down to one of the "seas".) Luna's radius is Order(3000 km) (plus or minus 75%!), and tha surface area of a sphere is 4*pi*r*r (I think), so the lunar surface has an area of 4*3*3e3*3e3 = 1e8 or so square kilometers of more or less usable area (give or take a factor of 100). Plenty of room.
karn (09/17/82)
Gee, you'd have to be careful not to put all those waste dumps together on one side of the moon, or else they might reach a critical mass and explode and drive the moon out of its orbit to wander through the galaxy and encounter all kinds of aliens and weird things... Seriously, reactors do have the advantage of generating power (and much needed heat) during the long lunar night. I would suppose that both solar and nuclear sources would have their places on the moon. Remember that the ALSEP packages used radioisotope generators. Phil Karn
ech (09/17/82)
#R:sri-unix:-330400:whuxlb:9300003:000:1162 whuxlb!ech Sep 17 15:24:00 1982 The observations about the relative advantages of solar over nuclear power on the moon are persuasive, except for one glitch: the sun shines only about half the time, and when it does shine you have to "point" your collectors at it for maximum advantage (simply spreading a sheet on the more-or-less horizontal means you wind up with a power uptake that looks like a sine curve with the negative side clipped to 0). Indeed, the solar arguments are most persuasive only when the sun shines almost all the time, e.g. in orbit. This is the tremendous advantage of the L5-style space colony: the sun is almost always there to tap, and keeping the collector aimed at it is fairly easy in freefall. The major problem with solar power on planetary surfaces remains the lack of effective energy storage technology. The need for energy storage transcends solar needs, of course: any electric utility would like to be able to run its generating plant at a constant rate, storing the surplus at times of low demand and tapping it for peak demand. Solar power for mining the moon has the dual problem: a constant demand and a fluctuating power source. =Ned Horvath=
CSD.MCGRATH@SU-SCORE@sri-unix (09/18/82)
From: Jim McGrath <CSD.MCGRATH at SU-SCORE> -------
barnes (09/20/82)
#R:sri-unix:-328000:uiucdcs:12700012:000:1131 uiucdcs!barnes Sep 19 19:49:00 1982 I seem to recall from my history classes that back a few decades we thought the oceans and remote sections of our planet were big enough to take it. The World has a slightly different opinion now. In 5000 years I don't think that hunk of rock will mean anything to us execpt as a museum. Think of what was happening on this planet 5000 years ago and if we survive another 5000 years, we won't be worrying about little star systems like this one. uiucdcs!barnes ***** uiucdcs:net.space / mcdaniel / 9:09 pm Sep 16, 1982 However, Luna is a *B*I*G* rock! There is plenty of room for just about anything you'd like to do. Furthermore, unlike the earth, one spot is just about as good as any other (no weather, river, air pressure, etc. worries -- just land roughness, and that can be solved with a grader or by going down to one of the "seas".) Luna's radius is Order(3000 km) (plus or minus 75%!), and tha surface area of a sphere is 4*pi*r*r (I think), so the lunar surface has an area of 4*3*3e3*3e3 = 1e8 or so square kilometers of more or less usable area (give or take a factor of 100). Plenty of room. ----------