No it isn't. Ramping is slow and can't be done beyond 20% very often or you destroy your fuel and control rods
Reducing output doesn't reduce costs, it increases them. This is the opposite of dispatchable.
If you can only pay for your reactor by coercing people into buying daytime electricity for 20c/kWh rather than buying a solar panel that will pay for itself in 3 years then it's not dispatchable.
You don't need to alter the thermal output of the reactor to modulate a nuclear plant's electrical output. You can more aggressively cool the reactor to reduce the energy delivered to the turbine. This isn't often done since it's essentially deliberately reducing the efficiency of the plant.
> Ramping is slow and can't be done beyond 20% very often or you destroy your fuel and control rods
It's not slow: the turbine water is can be cooled more aggressively immediately, and will start reducing output with one circuit of the generation turbine. Also, modulation only needs to vary 20-30% over the span of entire days not of tens of seconds. And no, dispatchable generation does not ramp in 10s of seconds. Natural gas plants - the most popular peaking generation plant - still takes an hour to activate. But this isn't an issue because electricity use doesn't fluctuate by 20% in the matter of tens of seconds.
> And it's still not dispatchable if not using it costs you anyway.
No? This just plain wrong. A dispatchable source is a dispatchable source, regardless of any associated costs. And with nuclear there isn't even any direct cost with running the plant at a reduced capacity. There's only the opportunity cost of lost electricity sales, which would happen anyway because there isn't enough demand.
If there's 100 GW of peak demand and 80 GW of minimum demand, building 100 GW of nuclear plants and reducing output during periods of non-consumption does not have any increase of costs.
Reducing output doesn't reduce costs, it increases them. This is the opposite of dispatchable.
If you can only pay for your reactor by coercing people into buying daytime electricity for 20c/kWh rather than buying a solar panel that will pay for itself in 3 years then it's not dispatchable.