Final answer:
The statement that radioactive elements with extremely long half-lives present the most challenging waste management problems is false. Short-lived isotopes emit more intense radiation, but long-lived isotopes require longer management due to their prolonged radioactivity. The half-life is key to determining the duration a substance remains hazardous.
Step-by-step explanation:
It is false that the most challenging radioactive waste management problems are presented by those radioactive elements with extremely long half-lives. In fact, elements with shorter half-lives can be more radioactive and hence can be of greater initial concern due to their more intense radioactivity. However, elements with long half-lives remain hazardous for a very extended period of time and require long-term storage solutions. Incidentally, short-lived isotopes decay more quickly into stable forms.
Radioactive waste is dangerous for thousands of years, and there is no definitive solution for its disposal. Radioactive waste from nuclear power plants, for example, must be stored for an extended period, around 10 half-lives of the radioactive elements, before it reaches acceptable levels of radioactivity. For example, storage of strontium-90, with a half-life of 28.8 years, would require around 300 years to reach safer levels.
Half-life is the period needed for half of the radioactive atoms in a sample to decay, and this measurement is crucial in determining the duration of said hazard. Substances like plutonium-239, with a half-life of 24,000 years, pose a significant challenge in radioactive waste management due to the long-term risk they present.