More Words, Deeper Hole

"Or just extremely durable stuff. That was the deal apparently in the Empire: the machines still existed, but nobody knew how to fix them, so when they broke down the inhabitants were "back to coal and oil". "

Japan is back to coal and oil. So is Germany.

Quoting Dorwin:
"The powah plant did undergo meltdown and it was quite a catastwophe, y'know. I believe wadiatsen damage. Weally, the govuhnment is sewiously considewing placing seveah westwictions upon the indiscwiminate use of nucleah powah though that is not a thing for genewal publication, y'know."
"It had bwoken down some yeahs pweviously and it is thought that the weplacements and wepaiah wuhk wuh most infewiah. It is so difficult these days to find men who weally undahstand the moah technical details of ouah powah systems."

Fits perfectly well with the nuclear stations "built forever" we see 105 years later. No more nuclear stations were licenced to open, and no repairs, because every nuclear station which needed repair needed to be shut down as "unsafe". Therefore no demand for technicians with ability to either build a new nuclear power station or repair a broken one. Therefore all schools teaching such to be shut down. Last technicians who did learn repairing nuclear power stations graduated early 50s just before Dorwin passed his restrictions, found something else to do and died decades before Mallow.