An overview of electron beam decontamination technology and applications

High-energy radiation is an effective means of decontamination, including sterilization, sanitization, and pasteurization. The principal sources are radioisotope and machine-generated radiation. Radioisotope sources use radioactive materials such as /sup 60/Co or /sup 137/Cs, which produce gamma radiation from nuclear decay. The inventory of radioactive material is typically 1 MegaCurie or more for a high-volume radioisotope irradiator. In contrast, the machine-generated radiation is obtained from an electrical power source that first produces a high-energy electron beam, to be used in a direct e-beam mode or in an indirect X-ray mode. The advantages of the machine-generated radiation are related to the lack of radioactive materials inventory, the ability to configure the radiation output to optimize coupling into the product, the reliability of modern industrial accelerators, and the relative simplicity of engineering the accelerator to the irradiator facility. The choice between the direct electron beam and indirect X-ray conversion systems is typically made as a trade-off between efficiency and product penetration distance. The efficiency of X-ray conversion of electron energy to total radiation is about 18 percent at 10 MeV. The major advantage of the X-ray process is the longer penetration distance, a factor of about 5 greater than that for the direct electron beam for typical treatment conditions. Accelerator technology and irradiation applications will be discussed, including food pasteurization, medical sterilization, and other decontamination applications. Several examples will be used to illustrate design choices and practical tradeoffs for these applications.