Why nuclear-gun fleet actions offered no useful victory

Did navies war-game capital-ship actions fought with nuclear shells?

Yes, and the general conclusion was that both sides would lose large numbers of ships.

Surface actions using nuclear shells were considered as naval thought exercises. British and American interest is recalled, while Soviet nuclear-shell work for cruisers is also mentioned. The conclusion offered is that such combat would be a way to lose large numbers of ships on both sides. The exchange supplies that broad judgment without detailed scenario rules, yields, or casualty calculations.