From a purely technological perspective, this may be true, but from a political, corporate investment ideology, and legal perspective, it won’t happen fast enough. Even the recent plants under construction have ceased with no other new ones even being planned.
They can build all the nuclear plants they want in Europe and Asia, it does nothing for us beyond proving the viability of new designs.
Here in the USA, the barriers to new plants are multi-facetted:
• The political winds between pro and anti nuke can shift too fast for corporations to risk spending that kind of money.
• Anti-monopoly laws stand in the way of a single style reactors unless they are designed and built to allow the use of fuel from more than one manufacturer. There are currently only 2 manufacturers of nuclear fuel assemblies in the US. Power plant owners/operators are required to buy from both so both stay in business in order to not violate these laws.
• While the public opinion towards nuclear is slowly shifting to pro, this isn’t the case when it comes to the “NIMBY” syndrome. “Not in my back yard” !
• Currently, nuclear generation only equates to about 25% of the generating capacity required for our needs. It also resides in only a small portion of the US. It’s impractical to transmit electricity all over the country and would necessitate building more plants in more areas (see last “NIMBY” comment.
• New regulations for ensuring the safety of current reactors that came out of the 9/11 and Fukushima events have required companies to invent a huge amount of money in current plants which takes away from using assets to build new ones. I think the added re-design and operational costs were, at least somewhat, responsible for the termination of continued construction of the new plants being built.
I could go on, but you get the idea.
I personally think your estimate on a “Viable Fusion Reactor” is a very liberal one. Currently, the fusion process can only be sustained for just a few milli-seconds. Beyond the need to make this a sustainable reaction in a laboratory environment, it will take many more years to design and test a practical, commercial design. And then they have to balance the cost of construction to long term pay-off.