Layman's question: I don't see how this small reactor is so unique or why it took so long to be developed for regulatory approval. The article claims it produces about 50MW of power with a planned 60MW version. Well, there are already very compact reactors in use on today's aircraft carriers (the A1B and A4W) that produce a much larger 500 to 700MW per module and are also relatively small (after all they fit on individual ships). And obviously deemed quite safe for the exact same reason -they're on ships that travel to all major ports and contain thousands of crew members right inside the same metal hull that the reactor is in. Even more compact and fit into an even smaller vessel quite safely for the crew: submarine reactors like the S8G, which produces over 220MW and measures only 42 x 55 feet in size, with a weight that's not unreasonably greater than that of the NuScale

Basically: What's so dramatically difficult about doing the same for a terrestrial compact reactor to make something like the NuScale take so long to get approval?