Nuclear energy comes from splitting atoms in a reactor to heat water into steam, which turns a turbine to generate electricity.
Carbon-free power generation 24/7/365
As RE and NG become cheaper, nuclear power plants are increasingly struggling to operate economically. Additionally, nuclear fuel is dangerously radioactive for thousands of years after commercial use and poses an existential threat in the event of man-made or environmental catastrophe (e.g. terrorist attack, tsunami, earthquake).
A great near-term source of carbon free generation; however, over time they need to be transitioned out of service.