That's kind of irrelevant.

Nuclear handles the base power generation. Grid storage is meant to handle peaks. It needs to be cheaper than coal, which is also used for peaks.

Anyway, grid storage is already about 200$ per installed kw with lithium. If sodium gets us to 100$, a 1GW installation comparable to a nuclear plant would cost 100 million. That's like 150 to 300x cheaper than a nuclear plant. And a plant takes years to build, decades even. A storage facility takes days or weeks.

Of course that does not count energy generation, but grid scale storage basically stores free excess energy from nuclear and renewables. So they actually improve the cost efficiency of nuclear and renewables, they don't compete with them.