There has been some experience, in this country, and worldwide, with power reactor decommissioning. The costs vary depending on when the plant was built in the first place (newer plants have higher capital costs because of construction delays caused by intervenors). But the numbers I recall are in the range of 10-30% of the initial capital investment, adjusted for inflation, are required for decommissioning and restoration.
BTW, not many people know it, but the nuclear industry is one of the few, perhaps the only, industry that is required to set funds aside ahead of time to cover decommissioning costs. This is known as the decommissioning fund and every licensed reactor has to demonstrate on a periodic basis to the NRC that funds are available for this purpose. I don't think the same is required of other industries, like refineries, chemical plants, factories, etc. I know some mining operations that involve strip mining are required to "restore" the land, but, to be honest, most places I've seen "restored" in this manner look more like a covered-over landfill. In my town alone there are dozens of abandoned industrial sites, such are aircraft manufacturing, steel rolling mills, bearing plants, a trash-to-power generating plant, that were simply abandoned in place, with the owners walking away and letting them rot, leaving it to "someone else" to deal with the legacy. Nuclear energy generating plants are required by law to plan for their own burial, yet you'll hear anti-nuke kooks ranting all the time about how "evil" the industry is because it plans ahead to manage it's waste.
As far as "waste" goes (most of the material isn't that at all), reprocessing with full actinide recycle is the way to deal with it. We have the technology and the know-how to do it, but lack the political will.
Well thanks for the info, guess I was wrong (happy to be wrong this time!) about shutdown costs on a nuke plant. thanks again.