This is indeed very important. Nuclear energy is clean and efficient.
That it is, but thorium also works. You need a "starter motor" of U-235 to get things rolling, but after that, you're good. The thorium molten-salt inherently safe reactor design is far superior to today's uranium-based systems, and we should be busting butt to get it fully researched and implemented, otherwise, we will be buying reactors from the Indians (and maybe the Chinese).
IIRC, the US has far more thorium than uranium (of course, India has more than anyone, which is why they are so interested in it.