There are three types of nuclear waste, classified according to their radioactivity: low-, intermediate-, and high-level. The vast majority of the waste (90% of total volume) is composed of only lightly-contaminated items, such as tools and work clothing, and contains only 1% of the total radioactivity.

High-level radioactive waste is the waste that comes from producing nuclear materials for defense purposes. Ultimately, this waste is stored as sludge, liquid, or pellets, and must be solidified before manufacturers or labs can dispose of it.

Low-level waste is typically stored onsite by licensees, either until it has decayed away and can be disposed of as ordinary trash, or until the accumulated amount becomes large enough to warrant shipment to a low-level waste disposal site. For further information, see Low-Level Waste.

Disposal of low-level waste is straightforward and can be undertaken safely almost anywhere. Storage of used fuel is normally under water for at least five years and then often in dry storage. Deep geological disposal is widely agreed to be the best solution for final disposal of the most radioactive waste produced.

Low-level waste is typically stored on-site by licensees, either until it has decayed away and can be disposed of as ordinary trash, or until amounts are large enough for shipment to a low-level waste disposal site in containers approved by the Department of Transportation.

Most commercially-generated (i.e., non-DOE) mixed waste is classified as low-level mixed waste (LLMW). LLMW is waste that contains low-level radioactive waste (LLRW) and hazardous waste. LLRW is defined as any radioactive waste that is not high-level radioactive waste, spent nuclear fuel, or byproduct material.