The uptime (or capacity factor) for fission plants is the highest of any energy source, at over 90% [1] [2]. By comparison, wind and solar at at 35% and 25% respectively.

1. https://www.statista.com/statistics/183680/us-average-capaci...

2. https://en.wikipedia.org/wiki/Capacity_factor#Worldwide

Also most downtime for nuclear power is scheduled which helps the grid operator avoid blackouts.

For anyone curious, usually down time is a month every 12-18 months. They refuel, do maintenance, and inspections during this time as well. Usually plants have more than one reactor, so these will be out of phase with one another.

Somehow I doubt those figures reflect disaster response downtime, such as we have had in Japan for a decade.

One may argue that was an overreaction, but the people of Japan beg to differ.

Regardless, those shut down reactors ought to drag down capacity factor for the nuclear industry, if the figures are to be credible.

Wind doesn't always blow and people react badly to melt-down. These are both facts of life.

Normally there are multiple reactors and scheduled shutdowns. This is true for any power source. I'm sure there are differences in maintenance efficiency vs coal or hydro, but it's a different question than short term fluctuation that are a characteristic of wind and solar.