The original reactor built in 1942 was just “barely” critical because the natural uranium that was used contained less than of the fissionable isotope U-235 (half-life 713 million years). If, in 1942,...

The original reactor built in 1942 was just “barely” critical because the natural uranium that was used contained less than
of the fissionable isotope U-235 (half-life 713 million years). If, in 1942, the Earth had been 9 billion years old instead of 4.5 billion years old, would this reactor have reached critical stage with natural uranium?