When can sources with a short half-life be disposed of?

The correct choice emphasizes that sources with a short half-life can be disposed of when survey readings near the sources are not above background levels. This is important for ensuring safety and compliance with regulations regarding radioactive materials. When the survey readings indicate that the radiation levels are at or below natural background radiation, it suggests that the radioactive decay has reached a level where the material no longer poses a significant health risk.

This approach underscores the importance of monitoring radiation levels and applying appropriate safety protocols before disposal. Regulatory bodies often require that radiation exposure be minimized, and ensuring that levels are not above background indicates that it is safe to proceed with disposal.

In contrast, suggesting disposal simply when they are no longer needed lacks a safety focus, and indicating a specific time frame based on age (as in being over a month old) does not consider the actual radiation level, which is critical. Approval from a technician is necessary for various operational decisions, but it must be informed by a thorough evaluation of safety. Thus, monitoring radiation through survey readings is the most reliable and safety-conscious approach.