High-Level Radioactive Waste

High level waste (HLW) is a type of nuclear waste that arises from the use of uranium fuel in a nuclear reactor and nuclear weapons processing. It contains the fission products and transuranic elements generated in the reactor core. HLW accounts for over 95% of the total radioactivity produced in the process of nuclear electricity generation.
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Noun
1. radioactive waste that left in a nuclear reactor after the nuclear fuel has been consumed
(hypernym) radioactive waste

Waste generated in core fuel of a nuclear reactor, found at nuclear reactors or by nuclear fuel reprocessing; is a serious threat to anyone who comes near the waste without shielding. (See: low-level radioactive waste.)