Why Is Lead Commonly Used As A Radiation Shielding Material?

Lead is familiar to medical personnel working with radiation; it's used in observation windows, protective doors, and walls of hospital X-ray machine rooms, as well as protective equipment in workplaces handling unsealed radioactive materials. Lead is frequently used as a radiation shielding material, so what's special about its structure?

We know that a substance's ability to block nuclear radiation depends primarily on two factors: its atomic number and its density.

Generally, the higher the atomic number, the stronger the radiation blocking ability. However, elements with higher atomic numbers are more difficult to form and therefore rarer, resulting in very high raw material costs. Furthermore, many elements with very high atomic numbers are themselves radioactive and unsuitable for radiation shielding.

Generally, the higher the density of a substance, the stronger its radiation blocking ability. Lead's density is 11.3 g/cm³. The densest substance on Earth is metallic osmium, with a density of 22.8 g/cm³.

In fact, lead's structure is not particularly special. Lead has a relatively high atomic number and density, while its material cost is relatively low. As seen in the periodic table, lead is the last element that is not radioactive; all the elements after it are radioactive and cannot be chosen. In many situations, lead is chosen as a radiation shielding material due to a trade-off between the application scenario, radiation blocking capability, and material cost. All materials have a certain degree of radiation shielding capability; nuclear power plant reactors use thick layers of concrete, and even water can be used as a radiation shielding material.