Well, I think you're right that we need to move away from fossil fuels, and you're right that nuclear power is a good way to do that. But you're mistaken about volcanic eruptions as a big contributor of CO2. While in theory a single big enough eruption, as in, bigger than any in all recorded history, could contribute more CO2 than a single year of human industry, there has been no such eruption. The biggest eruptions since we began recording CO2 levels have not even shown up as wrinkles in the plot of that quantity over time. What is seen at the monitoring station is a drop in CO2 every northern spring and summer, as northern-hemisphere vegetation captures atmospheric CO2, and a larger rise every northern fall and winter, as leaves decay and release that captured CO2---with the extra, year-over-year rise in CO2 coming from human fossil fuel use, or to a lesser extent, from deforestation. All other sources of CO2 are just rounding errors.