Re: [sl4] giant planets ignation - one more existential risk

From: John K Clark (
Date: Sun Dec 14 2008 - 10:57:51 MST

On Sun, 14 Dec 2008 "Alexei Turchin"
<> said:

> Use google!

Read books. I’ll let you in on a little secret, not everything on the
internet is true.

> US goverment think that Pu-238 may have critical mass:
> "Updated Critical Mass Estimates for Plutonium-238"

The most important sentence in the entire article is:

“Pu 238 is dependent on fast neutrons for criticality”.

I want to emphasize that this came from a paper that YOU recommended, it
said “FAST neutrons” and fast neutrons come from fusion reactions not
fission. So we are NOT talking about a chain reaction; how could we be,
Pu238 is not even a neutron emitter, not of the fast variety nor even of
the slow.

You could have a solid sphere of Pu238 (or Uranium 239) the size of
Jupiter and it would not explode without fast neutrons, and even then it
would not be a chain reaction; a small amount of fast neutrons would
only produce a small explosion, if you wanted a huge explosion you’d
need a huge amount of fast neutrons. In this regard Plutonium 238 is no
different from common cheap Uranium 238, indeed about 70% of the energy
of an H bomb comes from the splitting of cheap Uranium 238, but only
because it is hit by a HUGE number of fast neutrons caused by a nearby
fusion reaction. Neither 238 substance can produce a chain reaction.

> John, how would you explain that in 1979 scientists returned
> to the question and wrote the article there they said that
> detonation is possible if concentration of deiterium are higer then 1 to 300?

I know nothing about this 30 year old paper, nor do I know anybody who
does; and after you quote one of the equations in it I am not in any big
hurry to learn more. You quote:

“E = p**2 X***3 T**30”

I have no idea what “X” is and I don’t know what “***” means, presumably
“T**30” means T^30, that is to say taking temperature to the power of
30. But if you see any equation that has a term like T^30 in it then you
can be almost certain it is physically unrealistic. I can’t think of any
valid physical equation that rises ANY term to the power of 30! And my
God, why are Fusion reactors so Damn hard to make? And why didn’t
Jupiter blow up a long time ago? The power of 30?!

> Maybe you remeber Teller''s idea of
> Simple Super bomb which doesn''t
> work. It was a tube with liqiud deiterium,
> and it doesn''t want to propogate detonation wave.

It was a mixture of Deuterium and Tritium, the most fusion friendly
substance in the known universe and it STILL didn’t work. The gas giant
planets are composed of common hydrogen, common helium, a slight trace
of Deuterium and no Tritium. That is astronomically less fusion friendly
then Teller’s mixture, but you expect it to work anyway. I don’t.

> But why? Because it was too small

Size doesn’t enter into it. If the ocean is big and you’re a long way
from the bomb things are not extreme at all. If you’re right next to the
bomb things will get very hot but not super dense like they do in a H
You need both high temperature and high density for things to become
explosive, that’s because even at 100 million degrees when Deuterium and
Tritium collide most of the time nothing happens, they have to keep
trying over and over and over before a successful fusion event happens.
If things are super dense then all those retries can happen in a very
very short time, but if things are not dense (and I mean dense) after
the first failure by the time it finds another potential partner so much
time has passed that things have expanded and cooled off.

> In fact if Teller Simple Super would have widhth
> of several hundreds meters it would work.


 John K Clark

  John K Clark
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