Vitrification, geological disposal, reprocessing, and transmutation are some of the main long-term nuclear waste disposal methods. Vitrification involves mixing waste with glass to encase it. Geological disposal buries waste underground, but risks contamination if not properly contained. Reprocessing separates usable material from waste, but proliferation is a concern. Transmutation converts elements into less harmful ones through chemical reactions. Each method has challenges regarding the large volumes and long half-lives of nuclear waste.