11,500 tons is about .01 cubic kilometer. According to wikipedia the Pacific Ocean has a volume of 600 million cubic kilometers. I think it is going to get diluted pretty quickly.
Unless it has a reaction with the slightly warmer temperature of our earth's seawater because of too many people own Hummers! What if that reaction turns the radioactive material into some sort of self-replicating radioactive flesh eating virus!
What the hell would we do if that happened?
-Sab