> Eventually, more taps were installed on Soviet lines in other parts of the world, with more advanced instruments built by AT&T's Bell Laboratories that were nuclear-powered and could store a year's worth of data.

I assume they're referring to an RTG[1], where heat is generated by natural decay.

Earlier the article specifically mentions the storage medium being tape, and that they were replaced on a monthly basis. Perhaps the larger capacity versions were also tape? Was that the only realistic option at the time in such a situation, deep underwater with a requirement for large storage capacity?

[1] https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...