Why does nuclear waste stay radioactive for so long?

Nuclear waste remains radioactive for extended periods due to the presence of isotopes with long half-lives, which are the time it takes for half of a radioactive substance to decay. Many of these isotopes, such as plutonium-239 and cesium-137, emit radiation as they decay into stable forms, a process that can take thousands to millions of years. The stability and longevity of these isotopes mean that their radioactivity diminishes extremely slowly, posing long-term storage and environmental challenges. Consequently, effective management and containment strategies are essential to minimize risks associated with nuclear waste.