Yes, CP-1 used natural uranium (~0.7% U-235) and ultra high purity graphite. It would become impossible to attain without isotope separation in just a few hundred million years, to add to the billions from the formation of uranium in the star. Conversely, 1.7 billions years ago, it occurred naturally, with regular water to slow down neutrons.
Yes, CP-1 used natural uranium (~0.7% U-235) and ultra high purity graphite. It would become impossible to attain without isotope separation in just a few hundred million years, to add to the billions from the formation of uranium in the star. Conversely, 1.7 billions years ago, it occurred naturally, with regular water to slow down neutrons.
Fusion is more interesting.