Uranium in the past

How difficult would it have been to develop
nuclear power in the past? Let's go back 3 Billion
years, and assume.. some other planet. Could
"people" then have developed nuclear power easier
than us? The answer is surprising.. and yes! The
uranium isotope that fission with slow neutrons is
called uranium 235, and today it is present in as
mined uranium at about .7%, the rest being another
uranium isotope called 238. Now radioactive
isotopes, like uranium, decay and how fast they
decay (or change) is called their half life. Uranium in
the end decays into the element lead. But because
of the half life nature of decay uranium 235, about 3
billion years ago, was present at about 10%, not
.7% in natural uranium ore. In our power reactors
uranium is enriched to just 3% so ordinary water
can be used as a "moderator" (not important for
this discussion why it is used.. just remember the
3%). When you get up to 10% uranium 235 it is
possible to build smaller high power reactors. Now
if we go back 6 billion years, natural uranium ore
would have uranium 235 present at almost 90%.
Nuclear weapons using 90% uranium 235 are
feasible, although are modern weapons use even
higher percentages. What this means is that if life
developed elsewhere in the galaxy, became
intelligent, and discovered uranium.. to make the
material for a nuclear weapon all that need be done
back then would be to purify the element from the
ore, and if a "critical" amount was contained
properly, it would explode, as an atomic bomb. All
the problems our civilization has with weapons that
could be used to exterminate itself (and the only
reason it hasn't happened yet is the difficulty
individuals have in obtaining concentrated uranium
235 from ore that only has 0.7% in it) would not
have existed for any "people" living 6 billion years
ago. They would not have lived on earth of course,
our own study of earth history shows that, but it
might help explain why there seem to be so few
civilizations elsewhere obvious to us. Because they
would have been able to destroy themselves much
easier than us.. although I think we may be catching
up in our ability to do so.

As a matter of fact earth actually had an operational
nuclear reactor 2 billion years ago. The evidence indicates
it happened naturally, exactly because the uranium 235
then was more concentrated than today. Here is some
information about it.

falundafa-newengland.org...

Interesting.. No?

I don't know about uranium in the past but i know that we use depleted uranium in the back of boeing 747 airoplanes to balance it.

was it a high concentration of u-235?