Ammonia is made with hydrogen. If you are making hydrogen, nuclear biggest putative advantage, its lack of intermittency, becomes much less important.

If you are proposing thermochemical watersplitting using nuclear heat to make hydrogen, there is very great reason to be skeptical of that approach (superheated vaporized sulfuric acid, anyone?). These processes have never been practical, and the decline in cost of renewable electricity, and the decline in cost of electrolyzers, makes the thermochemical approaches even less competitive.