It just so happens that I am reading Andrei Sakharov's (https://en.wikipedia.org/wiki/Andrei_Sakharov) memoirs, he was heavily heavily involved in USSR's thermonuclear weapons design and development, and then became a peace activist, dissident and eventually a Nobel Peace prize winner. His memoirs are a mix of highly technical details and lovely descriptions of people. He mentions "demon core" in passing in an early part of the book, and I am paraphrasing/translating here, their "object" (barbed-wire walled off city, similar to Los Alamos, except USSR had way more of them) had technician who was measuring things just like the guy doing it with demon core - neutron flux, neutron absorption, etc; the measurements were using gaskets of standard width, with multiple layers in between the half-spheres; the technician was a) very capable, b) getting there in age and crucially c) prone to hitting the bottle at work. He eventually got caught and was immediately sacked and replaced with someone a) less capable and b) younger but c) not drinking, who eventually did something similar and I quote "although no lives were lost like in american incident, lots of equipment was ruined". He proceeds to add that they added lots of procedures and fail checks and safety equipment, and it slowed things a lot. He also quips then that after he learned about USA mishaps, he wasn't surprised that stuff like that went on "over there" too.