And a nuclear plant costs about the same to run whether it's running at 100%, or 20%. Fuel costs are negligible relative to capital and operational costs. So when lower-cost competition appears and eats into the demand for nuclear power, it actually increases the per-unit cost of nuclear power, which makes alternatives more compelling, which eats into demand, which turns into a cost death spiral.
Nuclear plants are great for base demand for these reasons (ie, the power that is always needed 24 hours round the clock, 365 days a year).
Alternative energies can provide some of that, meaning that plants need to shut down because outside of providing base demand, they're incredibly expensive to make power from.
