Because nuclear power plants are stupid expensive to build. The electricity sales prices is dominated by paying back the multi-billion dollar loan which funded

Because nuclear power plants are stupid expensive to build. The electricity sales prices is dominated by paying back the multi-billion dollar loan which funded the construction. Running a nuclear plant half of the time means doubling the electricity price - and it is already by far the most expensive method of producing electricity. If you build nuclear power plants, you basically have to run them at 100% capacity 100% of the time to be even remotely close to being economically viable.