This is assuming that radiation actually affects Xenomorphs. Also, if it affected them at all, it would likely be that the radiation-affected Xenomorphs would be useless, and likely killed by their brethren.
I forget whether or not Aliens: CM was canon, because if it is, that would mean that Xenomorphs do undergo changes when exposed to Radiation. Even though radiation doesn't work like that at all.
I think I asked this before when I first joined. Someone pointed out that there's a difference between radioactivity in fiction (the one we typically think of) and actual radioactivity, which isn't awesome at all.
As pointed out by a lot of people, the radiation blast at the end of Aliens shouldn't have affected the Xenos in ACM. At least, not in the way it did. Some even call it stupid. I don't really care.
Edit: This is all assuming radiation has the same effect on them as it does anything from Earth. But realistically (as loosely as I can say that in relation to Xenos), they wouldn't get powers, abilities, (useful) mutations, etc. They would just get sick and die.
Probably, over time, they could develop some kind of resistance to the radiation poisoning like some species of animal do. Not a useful thing, but it would be a small step higher on the evolution stairway.