According to the NRC, when can radioactive waste be delayed in storage?

The correct answer is based on the NRC's regulations regarding the management of radioactive waste. Specifically, radioactive waste that has a physical half-life of less than 120 days can be delayed in storage because it typically decays quickly enough that it will not pose a long-term risk. This allows for a more efficient handling process, as shorter-lived isotopes can be stored temporarily while they decay to safer levels. The regulation is designed to balance safety with practical management of waste.

In contrast, factors such as environmental storage conditions or the total activity of the waste (like mCi levels) do not influence the regulations governing how and when storage can be delayed. Additionally, while ensuring that waste is fully decayed before disposal is essential for safety, it does not directly relate to delay in storage regulations outlined by the NRC. Hence, the focus on the half-life of the material is crucial to understanding the guidelines for radioactive waste management.