As for the highly enriched uranium fuel, it would certainly *not* be worthwhile mounting a salvage mission to get it -- we have many thousands of kilos of HEU that is being taken out of weapons stocks and diluted to LEU (low-enriched uranium) for power plant fuel, as part of the "Megatons to megawatts" program.

As for the reactor units themselves, with energy-converting thermionic cells (or whatever the Soviets used on the Rorsats), I suspect they had a limited life, which would long since have passed. Various kinds of materials degradation mechanisms will likely have made them useless by now.

However, I imagine that a couple hundred years from now, they may become sufficiently easy to salvage, that they may simply be collected as historical artefacts for some museum display.....