RADIATION EFFECTS IN ORGANIC COMPOUNDS

DOE-HDBK-1017/2-93 Plant Materials RADIATION EFFECTS IN ORGANIC COMPOUNDS RADIATION EFFECTS IN ORGANIC COMPOUNDS As described previously, the effects of gamma and beta radiation on metal are not permanent. On the other hand, organic material will suffer permanent damage as its chemical bonds are broken by incident gamma and beta radiation. This chapter discusses how radiation effects organic compounds. EO 1.23 STATE how gamma and beta radiation effect organic materials. EO 1.24 IDENTIFY the change in organic compounds due to radiation. a. Nylon b. High-density polyethylene marlex 50 c. Rubber EO 1.25 IDENTIFY the chemical bond with the least resistance to radiation. EO 1.26 DEFINE the term polymerization. Radiation Effects Incident gamma and beta radiation causes very little damage in metals, but will break the chemical bonds and prevent bond recombination of organic compounds and cause permanent damage. Ionization is the major damage mechanism in organic compounds. Ionization effects are caused by the passage through a material of gamma rays or charged particles such as beta and alpha particles. Even fast neutrons, producing fast protons on collision, lead to ionization as a major damage mechanism. For thermal neutrons the major effect is through (n,gamma) reactions with hydrogen, with the 2.2 MeV gamma producing energetic electrons and ionization. Ionization is particularly important with materials that have either ionic or covalent bonding. Ion production within a chemical compound is accomplished by the breaking of chemical bonds. This radiation-induced decomposition prevents the use of many compounds in a reactor environment. Materials such as insulators, dielectrics, plastics, lubricants, hydraulic fluids, and rubber are among those that are sensitive to ionization. Plastics with long-chain-type molecules having varying amounts of cross-linking may have sharp changes in properties due to irradiation. In general, plastics suffer varying degrees of loss in their properties after exposure to high radiation fields. Nylon begins to suffer degradation of its toughness at relatively low doses, but suffers little loss in strength. Rev. 0 Page 45 MS-05