Comment by kulahan

Nuclear has an extensive startup cost, which makes it an extremely walled garden. This is the only place where it's prone to overruns. Once it's built, of course, it's by far the most efficient, most reliable, and most secure.

You can also bypass most project overrun concerns if you use already-approved reactors instead of trying to use a brand-new one, but of course this pushes back the schedule for profitability.