There are two levels of high level waste (HLW): the liquid waste from reprocessing which contains the fission products; and the entire unreprocessed used fuel (if direct disposal is planned). HLW is highly radioactive and contains long-lived activity; it generates a considerable amount of heat and requires constant cooling for many years. See Management and disposal of radioactive waste: concepts and requirements
Current definition: the highly radioactive solid material that results from the chemical reprocessing of spent nuclear fuel. It contains mainly fission products, trace amounts of uranium and plutonium and other transuranic elements.
is highly radioactive waste, usually in the form of spent fuel (or fuel which has been discharged from the reactor as waste) containing a high level (as defined by NRC regulations) of radioactive fission products.Â HLW is handled remotely, using water or a thick container as a radiation shield.