Myth: Nuclear is the best backup energy for renewables

Nuclear energy can provide all the backup needed for a grid that is mostly powered by renewables.

Fact:

The problem with this line of argument is that nuclear reactors must operate at near full capacity in order to amortise their high capital costs. This means they cannot ramp up their output if there is a sudden dearth of wind and/or sun. And even if they were to operate at a loss, at say 60 percent capacity, they cannot increase their output anywhere near quickly enough to deal with a failure elsewhere in the grid. 

Battery storage, hydro storage and peaking gas are far better forms of backup for renewable energy. They can be brought into play almost instantly, preventing blackouts while the power outage is rectified.