In 1960 or so, in elementary school in the Boston area, we did hide under the desk for nuclear bomb drills, like that would save you.
You might find this link interesting, its photos of the chain reactions of a nuclear bomb by a colleague of my Dad's, Harold Edgerton, He did it with really, really fast film speeds, he also invented the strobe light.Here is the link:
https://www.google.com/search?channel=cus2&source=univ&tbm=isch&q=high+speed+photography+nuclear+explosion&client=firefox-b-1-d&sa=X&ved=2ahUKEwjigY3t8fDrAhXJjp4KHWcyAl4QsAR6BAgJEAE&biw=1920&bih=938
I actually met him at a few BBQs at my parents house when I was around 9 or 10, he got/shared the Nobel Prize in Physics for his work, I was too young to understand what that meant. I remember that after he got the Nobel Prize he still drove a 1960 or so VW micorbus.