I'm not sure what you mean. Solar power has significant shorter emission amortization than 20 years. I think ATM we are at 2-3 years? And solar plants can usually run far longer than 20 years. And still, how does solar relate to nuclear, when solar is not the only solution for replacing nuclear?
This is not about amortization but about low-emission capacity
Then please explain a bit more than just throwing around some words.