So no energy is used to build nuclear power stations or to store the waste or for the many years of decommissioning?
There is no loss to the ecosystem during it's build, operation and when it goes horribly wrong?
A tidal system would generate power, not store it.
Renewables get turned off when they produce more energy than is required. A basic system to capture that excess energy to use when there is a demand is needed. It should be relatively cheap and reliable.
Pumped hydro doesn't need a huge area, just the required volume of water to store the excess energy expected. Any water would do as long as the turbines are designed to handle it.
The average life of a nuclear power plant is 50 years and they have many problems. They are also very expensive.
