I like the idea of a bit of radiation near stars and certain parts of space, but wrecked ships being permanently irradiated? Or said radiation effecting the environment so bad that charged beams of energy malfunction? Nah.
I'm not an expert in the field, so please do correct Me if I'm wrong, (as I probably am) but as I understand it, there are different types of radiation (alpha, Beta, Etc).
And only some types of radiation can screw up another entity's structure enough to make it radioactive.
From what I've read in the past, I could strip naked and do a little dance in Alpha wave radiation, and be fine (As long as I don't ingest said radiation source).
If I leave My clothes on, I could do a quick little dance around Beta radiation.
I'm not going flipping near Gamma or X-ray radiation, but I don't think they can make other items permanently irradiated.
I've spent about three years working around x-ray machines, The macjines themselves are perfectly safe and of no threat to the environment.
I think Neutron radiation is the only thing that can FUBAR the molecular bits of something so bad that it becomes radioactive, and I think neutron radiation stuff (lol) only happens in the moment of a massive nuclear reaction. The moment said reaction stops (like, say, shutting down a reactor), then neutron radiation stops.
What I'm getting at is, that unless every ship in that graveyard was carrying currently highly radioactive materials (like spent nuclear fission fuel rods or radon gas.... In a vacuum), there'd be no reason for them to be radioactive. At least not to any extent that it would effect the environment or create a hazard.
TL;DR: Unless those ships were parked at Chernobyl, or made out of radium 266, Radioactive death fields-o-ships get's a big "meh" from Me.