Radioactive Waste-where do we store it?

Was reading in SciAm about the benefits of nuclear power. There seems to be little doubt we need to come up with a number of alternate energy sources to lesson the havoc about to be wreaked on our small planet by global warming.

Although I agree that nuclear power plants have a much better safety record than they used to have, we still have a problem as to what to do with megatons of radioactive waste from these uranium burners. Some of the waste must be stored for thousands of years. Linguists are trying to come up with some kind of signage to warn future humans of the danger of these dumps thousands of years from now when language may be very different from today's.

Another problem is the plutonium produced in burning U235. You need to keep it out of the hands of wingnuts who might want to build a bomb.