Not sure if you're referring to a different simulator since model.energy doesn't seem to allow modeling nuclear? But, qualitatively, it sounds like the step-li

Not sure if you're referring to a different simulator since model.energy doesn't seem to allow modeling nuclear? But, qualitatively, it sounds like the step-like behavior you describe simply reflects whether LCOE(nuclear) > LCOE(renewable+storage)? That wouldn't tell the whole story though, since you might still want to keep the number of nuclear plants low, or you might simply be thinking about whether to keep operating existing plants, rather than building new ones.