> Do you consider nuclear energy sustainable?
Low-carbon, yes. Sustainable, yes. Renewable, not until we productionize extraction of uranium from seawater. [1]
> ... but do you believe nuclear, either fission or fusion, will play a large role in the future?
Fusion if we can crack it, totally. Seems like a clear winner. Fission probably will if there's some political will behind it, but not unless there's a change in sentiment.
[1] https://www.forbes.com/sites/jamesconca/2016/03/24/is-nuclea...
> of which the following sources are considered to be renewable
in other words, it attempts to define the world "renewable" along favoured political ideologies.
From Wikipedia:
> Advances in breeder reactor technology could allow the current reserves of uranium to provide power for humanity for billions of years, thus making nuclear power a sustainable energy
TL;DR: nuclear is just as renewable as solar (beyond any likely duration of the human civilisation).
It's probably not renewable (well, neither is the Sun on large enough timescale), but do you believe nuclear, either fission or fusion, will play a large role in the future?