Waste is a much bigger problem in the US than it is in other countries because fuel reprocessing is prohibited in the US. About 20% of the spent fuel is plutoni

Waste is a much bigger problem in the US than it is in other countries because fuel reprocessing is prohibited in the US. About 20% of the spent fuel is plutonium created from neutron activation of uranium 238. Another ~65% is stable fission products. The amount of dangerous materials is a lot smaller than what the US currently insists on burying. The US has held the no reprocessing position since 1977 when Jimmy Carter put a stop to it. Carter was worried about nuclear weapons proliferation, and believed that stopping spent fuel processing would help with that by reducing the amount of available plutonium. It seems that he hoped other countries would follow the US' example, but everyone else in the world went on processing and the US now has a big nuclear waste storage problem.