I don't get the nuclear fetish. Wind and solar are already far cheaper. I'm sure you're immediately thinking "but they don't work all the time!". That's true but we're still pretty far from having enough wind/solar to turn all other power plants off even when it is windy and sunny.
Also the cost estimates of nuclear don't include decomissioning because nobody has actually decomissioned a nuclear power station yet so who knows how much it costs.
Wind and solar are not at the scale we need to replace all the coal and gas plants. Nobody has build enough wind and solar at this scale so we don't know how much it costs to permanently maintain that setup (a lifespan of a solar panel/wind turbine is pitiful compared to nuclear).
Decommissioning costs can be considered once the planet is carbon neutral, which it is not right now. Right now the goal is to build up carbon-free energy generation. That said, if you ask the right people [1] they probably can give you an estimate.
Also the cost estimates of nuclear don't include decomissioning because nobody has actually decomissioned a nuclear power station yet so who knows how much it costs.