Nuclear requires least mining and materials over lifecycle vs any alternative so in this regard it's clean.

It has low land footprint as a bonus point

It outputs comparable or even smaller waste volumes vs alternatives per kwh over lifecycle. Both nuclear and renewables do create toxic waste over lifecycle. For eg ren do use much more copper both internally and for the grid. Copper mining is associated with arsenic and other dangerous chemicals that must be isolated forever, otherwise you get nasty spills like recently in Africa.

To sum it up, yes, nuclear is as clean as any good ren alternative