Hm, you're right. I haven't seen any of these episodes since the mid-80s, so my memory's a little fuzzy about it (I remember the episode about Nero's Ghost very well, especially the craptacularly cheesy "twist" ending, but in my mind over the years it had morphed into Napoleon's Ghost).

I thought about that radio thing in the remake, but the project had been going on for eight months and obviously people weren't staying in the core all the time, so maybe some vague rumors had leaked out/been overheard about some kind of nuclear incident, and the phrase "the 240" was being banded about.