I don't see any accounting for the cost of storing nuclear waste, long-term. (Nobody wants to do it; how do you even estimate that?)
Let's say you want to generate 1 megawatt-hour of electricity (roughly enough to power an average American household for a month). With coal power, you get roughly 2,000 pounds of carbon dioxide dumped into the atmosphere. [1] To generate the same amount at a nuclear plant, the waste primarily consists of about 3 grams of spent fuel. [2][3]
(And before anyone jumps on me, I'm not trying to dismiss other renewable options... just trying to put nuclear power in perspective.)
[1]: https://www.eia.gov/tools/faqs/faq.cfm?id=74&t=11 [2]: http://www.nei.org/Knowledge-Center/Nuclear-Statistics/US-Nu... [3]: http://www.nei.org/Knowledge-Center/Nuclear-Statistics/On-Si...
Now multiply that by the number of households, and again by twelve to see the amount you'd need to permanently store each year.
Newer designs, and some others, burn spent fuel. Out of the 3 major nuclear reactor incidents, all were old reactor designs. There are new ones that also cannot meltdown in the common understanding of the term.
Don't forget coal mining releases nuclear radiation, since you are unearthing radioactive minerals. So much so, that you are exposed to more radiation in the vicinity of a coal plant than a nuclear reactor.
Here's some info from the royal commission: http://nuclearrc.sa.gov.au/
And from the Citizens' Jury: http://nuclear.yoursay.sa.gov.au/
As I understand it, being paid to store nuclear waste is being viewed as an income stream for the state to backup or replace income from mining operations.
I think the supply line from port to the facility would be a softer target and is something the jury and stakeholders would be considering in serious detail.
By "still standing" do you include ruins where, say, only part of a wall remains?
Regarding the Pont du Gard, it's intact "due to the importance of its secondary function, as a toll bridge. For centuries the local lords and bishops were responsible for its upkeep, in exchange for the right to levy tolls on travellers using it to cross the river."
I believe bigiain's point is that the structures needed active upkeep to last thousands of years.
Your point is true about people robbing the masonry, but that's closely related to bigiain's comment about "keeping curious humans away from long half life radioactive trash".
Watch how it's done: https://www.youtube.com/watch?v=HeVPMzJOFrQ