According to the author of The Curve of Binding Energy [0], civil reactors were being subsidized by the purchase of plutonium (from the spent fuel rods) by the Department of Energy [1] to the tune of $1,000,000 per kg of Pu. The end of this program was coincidentally at about the same time as the Three Mile Island incident which leads many people to think that reaction to TMI was the reason that US reactor construction stopped.

When the Senate ratified some non-proliferation treaties, that also ended reprocessing spent fuel in the US which gets blamed on Carter.

Notes:

0 - https://www.amazon.com/Curve-Binding-Energy-Alarming-Theodor...

1 - The DOE owns all of the US nuclear weapons and leases them to the DOD.