It is not cheap if you include the cost of decommissioning. Consider the cost of taking care of the leftovers for the next few thousand years. Frankly no one knows what that cost might be since no one has ever decommissioned a atomic plant. They have shut them down and keep the maintenance up because:
A: No one wants the wase in their back yard B: No one knows how to do it.
Maybe you don't care, but frankly I don't want to leave my grand kids and great great great grand kids with all that waste and cost.
Atomic energy has never been cheep enough to compete with other sources. The only way atomic plants have been built was to provide materials for great projects like bombs. Take a look and see what the true cost of building and operating a modern atomic plant per unit of energy (after deducting government investment) and see what the real cost is, not counting decommissioning.