Why should nuclear power increase production? Let's face it for anything but military purposes it's just another source of power. There's really no reasing that a city with a nuclear power plant should be more productive than one getting it's energy from oil or coal.
The meltdown chance is a bit high at the moment, but should stay IMO.
Can't tell you how to edit it, sorry. One thing though : Power Plants don't really give a bonus to production directly, they give power, which gives a bonus to production. Which doesn't depend on the source of the power. So to change this you would have to add an production increasing effect directly to the power plant.