What constitutes 'high-level' radioactive waste?

High-level radioactive waste refers to materials that are highly radioactive and require specialized handling and disposal due to their potential hazards to human health and the environment. This category typically includes waste produced from the nuclear fuel cycle, particularly from activities such as nuclear power generation and the reprocessing of spent nuclear fuel.

The necessity for specialized handling and disposal comes from the intense radioactivity and long half-lives associated with high-level waste, making it dangerous if not managed properly. These materials generate significant heat and can remain hazardous for thousands of years, which is why they must be isolated from people and the environment through secure and long-term disposal methods, such as deep geological repositories.

In contrast, low-level radioactive waste does not necessitate such extensive precautions, and materials meant for recycling do not possess the same level of radioactivity and risk associated with high-level waste. Therefore, the emphasis on specialized handling and disposal sets high-level radioactive waste apart from other categories of radioactive materials.