Except that nuclear plants do not serve peak demand in any way, unless by "peak" you mean something other than the electrical supply industry means by that term; nukes are by nature very much baseload generation, taking days and weeks to spin up and synchronise. Pumped storage, gas turbine, large-scale hydro,... those are peak supply generation that can be brought onstream in minutes to hours to meet peak demand.

And don't forget the good old diesel generators that are the last line of defence when all other capacity is maxed out.

As we currently experience to great cost here in South Africa currently, where, due to a decade of neglected maintenance and capacity building brought about by a short-sighted government, rolling blackouts (euphemistically called "load shedding") are the norm, and diesel generation is brought to bear as a poor substitute for baseload capacity, at - as you may imagine - ruinous financial cost. Something in the region of USD400million a month for diesel fuel. Boy, are we in for some price hikes coming up!

Batteries (like Tesla's PowerWall) are an increasingly-relevant option for peak loads.

I was also under the impression that most peaker plants are likely to be natural gas fired and not nuclear -- as in, easier to build, and less of an investment to recoup if something better/cheaper comes along for peak loads.