Plastic bags last longer in landfills than nuclear waste will last in a repository; plastic photodegrades in about 500 years, multiply by a two-hundred-meter-deep landfill and that plastic will finish going away in about a million years [1]. Nuclear waste is fundamentally static; unlike tailings, it pretty much stays where you put it. Coal plants actually produce titanic amounts of radiation, vastly more than nuke plants, thanks to impurities in coal, and that radioactivity is going straight into the atmosphere [2]. Nuke plants don't produce that much waste in the first place; thirty tons a year, compared to millions of tons of radioactive, caustic fly ash [3, 4]. And, finally, the kinds of nuclear reactors we can build these days simply don't produce waste that lasts that long; a good breeder reactor eats anything that's immediately dangerous (short half-life -> lots of radiation) or long-term dangerous (long half-life -> not much radiation) [5].

[1] http://www.slate.com/articles/news_and_politics/explainer/20... [2] http://en.wikipedia.org/wiki/Coal_plant#Radioactive_trace_el... [3] http://en.wikipedia.org/wiki/Nuclear_waste#High-level_waste [4] http://en.wikipedia.org/wiki/Fly_ash#Environmental_problems [5] http://en.wikipedia.org/wiki/Breeder_reactor#Waste_reduction