Suitcase Nuclear Reactors for Space

I read about this last week when they announced it at a meeting of the American Chemical Society, but I wanted more details before posting about it here.  Since then I’ve found some terminology that I could search for to gather information for you and maybe answer some questions that myself and others have brought up concerning this technology on various comment threads.  The sources for what I found are detailed in the links provided in this article.

First, the basics…

NASA is working on a suitcase-sized fission nuclear reactor design which they call the “Fission Surface Power System” for use in powering space exploration and colonization projects on the Moon and Mars and other places.  These devices will use Uranium dioxide for fuel and will be cooled by radiators and a liquid metal called NaK (sodium-potassium alloy) instead of the water and huge cooling towers used by fission reactors here on Earth.  These self-contained power units would produce 40 kilowatts of energy for eight years.

One of the questions I’ve heard folks ask concerns the possibility of using something like this to power one’s home.  I wondered the same until I wikied that liquid metal stuff, NaK.  It turns out that NaK becomes an explosion hazard when exposed to air, so the likelihood of anyone actually selling a piece of equipment to the general public that contains NaK, to be used on Earth, seems unlikely to me.

Another question I hear a lot is how the radiation is shielded.  I finally found a diagram of what these power units will look like when installed and it shows that the portion of the design that contains the actual reactor will be underground.

Someone else in a comment was interested in whether or not this technology can be used to power a spacecraft.  While researching NaK I discovered that the Russians were flying NaK cooled, U235 nuclear reactors on their Radar Ocean Reconnaissance SATellite ( RORSAT ) from 1967 to 1988.  I don’t know if the design is similar to the power units being proposed, but I don’t like what I read about the RORSAT satellite.  Several failed missions and RORSAT retirements resulted in either radioactive debris surviving reentry through the atmosphere, or droplets of NaK-78, contaminated with radioactive Argon-39, orbiting the planet where they remain a hazard to spacecraft to this day.  At the end of their missions, all of the successful RORSATs ejected their reactor cores into a high “disposal” orbit which will still decay after several hundred years and accidental RORSAT reactor reentries have historically caused radiation contamination on the ground or in the ocean. 

I don’t know much about such things, so people smarter than me who read this might be able to shed more light on them.  I’m sure that the problems with the RORSAT were due in part to a lack of safety and environmental emphasis on the part of the former Soviet Union.  But we live in different times now and I hope that any issues like this will be fully addressed and the questions answered officially by the folks who will build these “new” power units and by NASA who will fly them.  So far, all they seem to want to say publicly is that these reactors “are safe”.

~ by Bill Housley on September 10, 2011.

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