In what scenario might a radiation worker use a shield made of lead?

Using a shield made of lead is particularly effective when working with gamma radiation due to its high penetration power. Gamma rays are highly energetic electromagnetic radiation that can pass through most materials, making them more challenging to shield against compared to alpha or beta particles. Lead is dense and has a high atomic number, which allows it to effectively absorb and attenuate gamma radiation, thus significantly reducing the radiation dose to the worker.

In contrast, for alpha radiation, which has low penetration capability and can be stopped by a sheet of paper or even the outer layer of human skin, lead is unnecessary and not the most efficient choice for protection. Beta radiation is more penetrating than alpha radiation, but materials like plastic or glass can often be sufficient for shielding against it. Therefore, using lead specifically for gamma radiation is based on the need to address its unique penetrating characteristics. The option of using lead when no radiation sources are present would not apply, as shielding is only necessary in the presence of radiation.