https://arstechnica.com/science/2019/01/how-an-oak-ridge-lab-group-hopes-to-extend-the-lives-of-aging-nuclear-reactors/

Nuclear power provides roughly 20 percent of the United States' electricity and about half of its low-carbon electricity. Whether you think nuclear power is a good or a bad thing, the fact is that the existing nuclear power fleet contributes a significant amount of energy to the US grid, and all that capacity is rapidly approaching its sunset years.