The U.S. Navy’s first nuclear submarine, launched in 1954, was highly influential in our nuclear power design history. I spent ages researching a land-based prototype built in an obscure part of the country, in Idaho. Called variously STR or S1W (the screenshot below is from its Wikipedia entry), I thought I’d mastered its history, until I read this in Todd Tucker’s Atomic America: How a Deadly Explosion and a Feared Admiral Changed the Course of Nuclear History: “Even today [written in 2009], the exact power capacity of the S1W reactor remains classified, and the S1W prototype in Idaho, decommissioned since 1989, is one of the few historic locations at the site that remains strictly off-limits to visitors.”
So it turned out I didn’t know the most basic fact about one of the most important historical reactors! And at the time I read Tucker’s book, I could do no better. Not until this year, when plans were made to finally decommission S1W in Idaho, did power capacity figures surface for the benefit of my book. A secret for some seven decades!