Oh.
Oh.
The 1943 Los Alamos Primer was a 24-page document for new scientists joining the Manhattan Project. It's fairly readable, and discusses several problems I hadn't considered.
https://sgp.fas.org/othergov/doe/lanl/docs1/00349710.pdf
https://physicstoday.scitation.org/doi/10.1063/PT.3.3692