DOE-HDBK-1017/2-93ATOMIC DISPLACEMENT DUE TO IRRADIATIONPlant MaterialsATOMIC DISPLACEMENT DUE TO IRRADIATIONThe effects of radiation on plant materials depend on both the type of radiationand the type of material. This chapter discusses atomic displacements resultingfrom the various types of radiation.EO 1.16STATE how the following types of radiation interact with metals.a.Gammad.Fast neutronb.Alphae.Slow neutronc.BetaEO 1.17DEFINE the following terms:a.Knock-onb.Vacancyc.InterstitialOverviewIonization and excitation of electrons in metals is produced by beta and gamma radiation. Theionization and excitation dissipates much of the energy of heavier charged particles and does verylittle damage. This is because electrons are relatively free to move and are soon replaced. Thenet effect of beta and gamma radiation on metal is to generate a small amount of heat.Heavier particles, such as protons, a-particles, fast neutrons, and fission fragments, will usuallytransfer sufficient energy through elastic or inelastic collisions to remove nuclei from their lattice(crystalline) positions. This addition of vacancies and interstitial atoms causes property changesin metals. This effect of nuclear radiation is sometimes referred to as radiation damage.In materials other than metals in which chemical bonds are important to the nature of thematerial, the electronic interactions (ionizations) are important because they can break chemicalbonds. This is important in materials such as organics. The breaking of chemical bonds can leadto both larger and smaller molecules depending on the repair mechanism. In either case there are material property changes, and these changes tend to be greater for agiven dose than for metals, because much more of the radiation energy goes into ionizationenergy than into nuclear collisions.MS-05Page 32Rev. 0
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