radiation equipment & shielding (3842-rs)

overview of radiation equipment & shielding (3842-rs)

— radiation protection can be divided into occupational radiation protection, medical radiation protection, which is the protection of patients, and public radiation protection. different types of ionizing radiation interact in different ways with shielding material. the effectiveness of shielding is dependent on the stopping power of radiation particles, which varies with the type and energy of radiation and the shielding material used. particle radiation consists of a stream of charged or neutral particles, both charged ions and subatomic elementary particles. this includes solar wind, cosmic radiation, and neutron flux in nuclear reactors. alpha particles are the least penetrating. beta particles are more penetrating. however, in cases where high energy beta particles are emitted shielding must be accomplished with low atomic weight materials such as acrylic sheet. in the case of beta+ radiation, the gamma radiation from the electron-positron annihilation reaction poses additional concern. neutron radiation is not as readily absorbed as charged particle radiation, which makes this type highly penetrating.

neutron shielding materials include borated polyethylene. cosmic radiation is extremely high energy, and is very penetrating. nasa determined that materials that have high hydrogen contents, such as polyethylene, can reduce primary and secondary radiation to a greater extent than metals. x-ray and gamma radiation are best absorbed by atoms with heavy nuclei; the heavier the nucleus, the better the absorption. gamma rays are better absorbed by materials with high atomic numbers and high density, although neither effect is important compared to the total mass per area in the path of the gamma ray. the effectiveness of a shielding material in general increases with its atomic number, called z, except for neutron shielding which is more readily shielded by the likes of neutron absorbers and moderators such as compounds of boron, cadmium and carbon & hydrogen.