(191x) Effects of Radioactivity On Surface Interaction Forces

Explosion of radiological devices is expected to generate radiological debris.  Transport and distribution of this debris in the surrounding environment is of great concern with regard to understanding the environmental and health risks and devising methods to reduce these risks.  Current tests and analyses of radioactive-particle plumes do not take into consideration the possibility that radioactive particles may behave differently than “cold” particles.  Radioactive particles can become electrostatically charged as a result of the decay process.  A theory has been proposed to describe this self-charging phenomenon, which may have a significant effect on how these particles interact with one another and with charged surfaces in the environment.  In this study, atomic force microscopy (AFM) is employed to quantify surface forces between a particle and a planar substrate and to compare measurements with and without the involvement of radioactivity.  The main objective of the study is to assess directly the effects of radioactivity on the surface interactions of radioactive aerosols via the measurement of the adhesion force and the surface potential.  The adhesion force between (i) a silicon nitride AFM tip and an activated gold substrate and (ii) between a radioactive particle attached onto the AFM cantilever and a planar substrate is measured so that any possible effects due to radioactivity can be observed.  Preliminary experiments have shown that the adhesion force between the tip and the gold surface increases significantly when the gold substrate is activated to a certain level.