In particular, Gates singled out a company called TerraPower, which designs nuclear reactors that run on depleted and unenriched uranium. By producing power from these less pure forms of uranium, TerraPower's reactors would produce electricity at a far lower cost than current nuclear plants, since they could use both spent fuel from other reactors and skip the costly enrichment process for newly mined uranium. Plus, by running on used fuel rods, TerraPower reactors also solve the problem of nuclear waste. So far, TerraPower reactors running on U-238 have succeeded in computer simulations, but have yet to see action in the real world.