What are you saying, that fossil fuel power plants, presumably quick responding natural gas fired ones, will always have to be incorporated into a power supply mix? If it is just for emergencies, that seems like a reasonable compromise. Would it even be considered part of the mix in that case? Still, I'm not convinced that that would really be necessary. Couldn't a properly sized variable load be sited at each nuclear power plant to the same effect? Couldn't it be as simple as sending a little bit of steam to small turbines that are just for grid start up and then venting the rest?