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"Health Physics and Environmental Resuspension of Radioactivity"

Physics Seminar Speaker Series: Professor Shaun Marshall

Snacks at 4:30 pm, Talk begins at 4:45 pm

Health Physics is the science of radiation safety which studies the beneficial uses of radiation while protecting people and the environment from its hazards. Following a contamination event, radionuclides can become airborne and will deliver an internal dose of ionizing radiation when inhaled or ingested. Predicting the airborne quantities which have resuspended from a deposition is complex given the number of factors which can influence the resuspension mechanism. The currently accepted predictive model used by federal agencies, the 2011 Maxwell-Anspaugh semi-empirical resuspension factor, has limited applicability due to the basis data spanning a wide range of environments, particulate sources, and nuclide species. This has motivated a recent effort to develop a catenary compartment model to relate surface-to-air concentrations and characterize the resuspension kinetic rate constant. An in-house resuspension chamber was developed to probe air sampling times and protocols to quantify resuspended particulates. Micron-sized Europium oxide powder was deposited on a concrete substrate and air was sampled at heights of 0.25 and 1 meters using a low-volume air sampler. Air sampler filters were then analyzed for mass using neutron activation analysis with delayed gamma spectroscopy. Results indicated substantially lower resuspension factors than the historic data, in agreement with the proposed catenary model. Additionally, lowering the sampler head from 1 to 0.25 meters appeared to significantly enhance particulate collection, suggesting a sensitive height distribution of particulates.

Shaun Marshall is a Visiting Assistant Professor of Physics at Mount Holyoke College and previously a Senior Staff Radiation Scientist at Geosyntec Consultants; he is an Associate Member of both the Health Physics Society and the American Academy of Health Physicists.

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