The difference between telecom radiation, UV radiation, and nuclear radiation is that the latter is the result of radioisotope decay; you basically have the unstable elements floating around emitting gamma particles, or what-have-you. Whether these isotopes would just settle to the bottom of the ocean, and whether they could be incorporated into the food chain I don't know. I imagine that ocean currents could carry them a ways before they'd settle, and that they would be incorporated into the food chain.
I don't know how much of these types of elements you can ingest before it's considered unsafe (or if there is even a safe level), but it'd probably be best to avoid them. Unlike energy (e.g. UV waves, etc.), these elements (e.g. cesium, uranium, etc.) can persist in the environment or in an organism for many decades, emitting damaging particles as they decay.
That being said, there is the hormesis hypothesis; low levels of a toxic substance actually improve survival. IIRC, individuals far from and close to Hiroshima when the bomb went off fared worse than those at mid-distance from the blast...