In terms of pure operating costs ignoring everything else it can look good vs other sources that include all costs.

However, ‘Paid off nuclear’ in terms of construction costs still needs to worry about decommissioning, and their maintenance costs keep increasing every year.

Several power plants have looked at going offline for potentially years and spending billions at around year 40 to get to year ~60 as not being worth the investment. That’s the issue with projecting those long lifespans, the buildings/containment structure/cooling tower may be fine but that doesn’t mean the pipes, pumps, turbines, and control systems etc are still fine.