If the world continues on a high-emissions trajectory, and people do not later pursue active remediation measures to remove CO2 from the atmosphere, it will take hundreds of thousands of years for natural silicate weathering to draw down atmospheric concentrations to preindustrial levels. More than half will be removed by faster processes, within 1000 years, but a significant minority of the excess will go away over the course of ~400,000 years:

https://www.nature.com/articles/climate.2008.122/figures/1

This is actually longer than the time it will take for the majority of fission products and actinides generated in nuclear fuel to decay. The waste CO2 problem is also distributed over the whole globe rather than easily confined to storage casks like spent nuclear fuel is.