[ExI] Double-Earth (Was: kepler study says 8.8e9 earthlike planets)

[spike]

Doh!  I meant 640C, not 640K.  Embarrasskin!

 

Here's something cool: the Pu alpha decays to 240Np, which is denser, so it
sinks toward the center, but really doesn't have time to go far with that
hour half-life to 240Pu, but then the concentration of 240Pu goes up and
heats up, so I suppose it would boil, but under enormous pressure perhaps
not, so it isn't clear if a critical mass eventually results.  At about 900K
starting temperature, the radiative heat loss to space isn't much, and there
is gravitational heating as the helium bubbles to the surface and the radius
decreases, resulting in heating.

 

Wowsers I need to get to work on a sim of this, oy.  My intuition tells me
it eventually creates enough Pu240 to create a critical mass.  It alphas
down to Uranium 236 with a half-life of about 6600 years.  Then some of that
alphas to 232U and a little of it undergoes honest fission to lead and
magnesium.  What I don't know is if a critical mass in the center of an
enormous ball of Pu244 does what we are so accustomed to critical masses
doing.

 

Any nucular physicists, do feel free to jump in and help me here.

 

Hey I wonder if the feds are getting nervous watching me google around on
plutonium and uranium?

 

spike 

 

From: extropy-chat-bounces at lists.extropy.org
[mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of spike
Sent: Tuesday, November 26, 2013 8:02 AM
To: 'ExI chat list'
Subject: Re: [ExI] Double-Earth (Was: kepler study says 8.8e9 earthlike
planets)

 

 

 

>. On Behalf Of Anders Sandberg

 

>>>. Even I agree that a planet with plutonium oceans is unlikely to be
habitable for life. -- Dr Anders Sandberg

 

>>.I learned a new thing by thinking about this.  There is an isotope of
plutonium which is non-fissile, 244.  Get a sphere of the stuff, heat it to
900 and some Kelvin, you have an ocean of plutonium, with radioactive
particles up the kazoo but no fission.  Until Anders' offhanded comment
about an ocean of plutonium, I never knew there was such a critter.  Ain't
science kewallll?  {8-]


>.Sounds like a great practical joke to do when re-engineering a solar
system. A hot ecology based on plutonium as a solvent for some weird
metal-oxide biochemistry/mechanochemistry.  -- Dr Anders Sandberg

 

As practical jokes go, that one would be elaborate.

 

As Anders' comments often do, this notion of a plutonium sea has me
pondering.  Assume into existence a sphere of molten plutonium 244.  The
melting point of plutonium is not so high, about the same as magnesium and
lower than that of aluminum, both of which are easy to melt for the home
hobbyist, and even if not, most of us here have tossed aluminum soda cans
into the campfire, so it isn't glowing red when it melts.

 

So I was starting to work on a heat model that has some interesting
properties.  If you assume the liquid plutonium planet out in space far from
anything, at about 650K, ten over the melting point, it is easy to calculate
the heat loss from radiation to space with Boltzmann's law.  Now take the
radioactive decay energies, 80 million year half life for Pu244, then see
what happens.  There is an alpha decay to Neptunium 240 plus a helium atom
at first, and helium reacts with nothing so that stuff comes bubbling to the
surface, and the 240Np beta decays with a half life of about an hour to
Pu240, which is fissible.  The model's future may depend on the initial
radius of your planet, but it looks to me like the thing eventually
explodes.

 

Thanks Anders!

 

spike 

 
 
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