Long term storage and/or reprocessing of fuel. On site storage is not a viable long term solution. We need some way to safely store expended fuel or change the rules to allow reprocessing. Commercially, we need to figure out an economical way to build power plants that doesn't die under the weight of its own regulations. Vogtle 3 & 4 went waaayy over budget, and almost bankrupted the partners (Westinghouse I believe). Solar and wind are seeing reduction in cost due to expanding market and the economy of scale that goes with it, along with generous subsidies. For nuclear to get those benefits it would have to be constructed at a rate not seen since Three Mile Island. We lost all of those benefits accrued during the 60s 70s and 80s. We would be starting at least 10 years behind wind and solar.