Using the fuel in production is not.
“Making nuclear fuel is dirty and expensive.”
Uranium is currently around $45 per pound. Each pound contains roughly the energy of 500 tons of coal.
You do the math.
“Ironically the electricity used to enrich uranium is usually provided by conventional coal/gas plants.”
If common sense were to prevail and we generated more electricity using nuclear power, that wouldn’t be the case, would it?