I believe "these units" refer only to the nuclear reactors, not to the plant as a whole. The plant will likely need ongoing replacements, and more, newer react

I believe "these units" refer only to the nuclear reactors, not to the plant as a whole. The plant will likely need ongoing replacements, and more, newer reactors can be added over time. The same plant/real estate could serve as a power plant for many times that amount of time. It is also quite feasible to move the spent fuel and any other radioactive material to another location... there are politics involved, but the physics are pretty straight forward.