A lot (assuming that you are talking about the mess at Hannaford). Most of that mess however is from government and early commercial nuclear power and/or weapons research and testing going back to WWII.
That's part of the problem, spent fuel is presently stored on-site because nobody has put up the cost to invent a reprocessing solution. Storing the waste safely at diverse locations, perhaps for centuries with continual security, and the future transport and reprocessing, are costs that aren't necessarily recognized in comparing nuclear to other energy sources.
