However, this does not imply that e-beam sterilization is limited in application to low-density or smaller products. The penetrating ability of electrons is less than that of gamma rays. This makes it easier to meet both the dose required for sterilization and remain below the maximum dose tolerated by the product. Consequently, treatments have comparable uniformity, usually expressed by the ratio between maximum and minimum dose (dose uniformity ratio or DUR) deposited in the irradiation configuration. The penetration of high-energy x-rays used for sterilization is comparable to that of gamma rays. Consequently, assuming same flux of electrons and gamma rays, e-beam dose rates are much higher than gamma-ray dose rates, resulting in significantly reduced exposure times (seconds versus minutes or hours) and allowing for higher throughput. Gamma rays from a cobalt-60 source are emitted omnidirectionally, whereas e-beam and high-energy x-ray photons are directed toward the product to be irradiated. ![]() The main differences in the different modalities are related to dose rate, exposure time, penetration depth, and product compatibility. Sterilization by gamma-ray, e-beam, and x-ray modalities is broadly similar in terms of the transfer of energy and interaction with matter (see Appendix F). The materials to be sterilized are typically packaged on a conveyor that transports them at a controlled speed from a loading area to a treatment area where they are irradiated and then returned to an unloading area. The Centers for Disease Control and Prevention (CDC) protects people’s health and safety by preventing and controlling diseases and injuries enhances health decisions by providing credible information on critical health issues and promotes healthy living through strong partnerships with local, national, and international organizations.Radiation for sterilization applications is typically derived from one of three sources: gamma rays (cobalt-60), electron beam (e-beam) accelerators, and accelerators that produce x-rays for irradiation. įor more information on protecting yourself before or during a radiologic emergency, see CDC’s fact sheet titled “Frequently Asked Questions (FAQs) About a Radiation Emergency” at /radiation/emergencyfaq.htm, and “Sheltering in Place During a Radiation Emergency,” at /radiation/shelter.htm. Co-60 absorbed by the liver, kidneys, or bone tissue can cause cancer because of exposure to the gamma radiation.įor more information about Co-60, see the Public Health Statement by the Agency for Toxic Substances and Disease Registry at, or visit the Environmental Protection Agency at. Most Co-60 that is ingested is excreted in the feces however, a small amount is absorbed by the liver, kidneys, and bones. ![]() It resembles iron or nickel.īecause it decays by gamma radiation, external exposure to large sources of Co-60 can cause skin burns, acute radiation sickness, or death. Co-60 can occur as a powder if the solid sources have been ground or damaged.Ĭo-60 is a hard, gray-blue metal. Co-60 also is a byproduct of nuclear reactor operations, when metal structures, such as steel rods, are exposed to neutron radiation.Ĭo-60 occurs as a solid material and might appear as small metal disks or in a tube, enclosed at both ends, that holds the small disks. ![]() Radioactive Co-60 is produced commercially through linear acceleration for use in medicine and industry. Nonradioactive cobalt occurs naturally in various minerals and has long been used as a blue coloring agent for ceramic and glass. Co-60 also is used for food irradiation, a sterilization process. It is used industrially in leveling gauges and to x-ray welding seams and other structural elements to detect flaws. Mode of decay: Beta particles and gamma radiationĬhemical properties: Metallic solid that can become magnetically chargedĬo-60 is used medically for radiation therapy as implants and as an external source of radiation exposure.
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