AFAIK, nuclear power plants and renewables do not mix well. In a grid with 80% renewables, there is no need and use for classical baseload generation like nuclear power plants, since they cannot be dialed up or down fast enough to follow demand. However, gas power plants can do this. And with using power-to-gas during periods with abundant renewables, storing the generated gas (this infrastructure already exists, at least in Europe), and burning it when there is a lack of renewables, a grid with 100% renewables is very well feasible.
In addition, nuclear power plants take ages to build, even if we started building loads of them right now, they would come online too late.
[Edited for typos.]
