Believe it or not, there’s more than one type of radiation. In fact, there are 4 main types to discuss: electromagnetic, alpha particle, beta particle, and neutron.
Alpha radiation is a positively charged helium nucleus. Alpha particles are extremely dangerous but are extremely easy to block. Alpha particles can be stopped by the outer layer of skin. As a result, alphas are only dangerous if ingested or inhaled.
Beta radiation is that due to electrons and positrons being emitted. Betas can be blocked by clothing or thin paper.
The final two forms of radiation that are dealt with on a regular basis are gamma rays and neutron emission. Neutrons and gammas are both difficult to stop and are highly damaging albeit less so than alphas. In order to protect people from these types of radiation, specialized shielding is required. Hydrogenous materials are typically used for blocking neutrons due to their high neutron absorption and scattering cross sections. Typically either water tanks or borate-infused polyethylene are used in order to block neutron radiation. Neutron irradiation is of special concern due to its ability to transmute materials into a radioactive source. If a human was exposed to a neutron source for a sufficient length of time, the calcium in his or her bones would become radioactive.
Gamma radiation is typically attenuated by heavy metals. The most common metal for this purpose is lead. Steel can also be used; however, it is only about half as effective compared to lead. Ultraviolet radiation can also cause ionization (cellular damage) as well as cosmic radiation. Cosmic radiation is mostly dissipated in the Earth’s atmosphere; however, some still reaches the surface.