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Title:The effects of contaminant aging and decontamination logistics on remediation after a radiological dispersal event
Author(s):Hepler, Katherine C
Director of Research:Kaminski, Michael D
Doctoral Committee Chair(s):Huff, Kathryn D
Doctoral Committee Member(s):Roy, William R; Stubbins, James F; Valocchi, Albert
Department / Program:Nuclear, Plasma, & Rad Engr
Discipline:Nuclear, Plasma, Radiolgc Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):radiological decontamination
washdown operations
Abstract:Rapid remediation of an urban environment after a large-scale nuclear or radiological material release requires simple, non-destructive decontamination techniques with manageable waste. The Integrated Wash-Aid Treatment Emergency Reuse System (IWATERS) was developed for this purpose. In IWATERS, urban surfaces are sprayed, the contaminated wash solution is collected and treated, and the treated wash solution is recycled. This work adds to IWATERS by simulating the logistics of IWATERS and performing experiments that provide insight into optimal IWATERS operating parameters and changes in decontamination efficacy over time. The simulation of material transport and top-level operations of washing down surfaces to remediate four blocks of downtown Chicago, IL identified clay for the treatment of wash solution as the limiting factor in decontamination progress. More importantly, this work created the framework for future simulations of IWATERS deployment to aid recovery optimization. Decontamination experiments showed longer solution application times improve soluble cesium removal and runoff solution can effectively decontaminate larger surfaces. Combined, these results suggest the optimal spray pattern for responders washing down surfaces is spraying along the top portion of buildings for 15 minutes per section and allowing the solution runoff to decontaminate lower portions of buildings. However, the removal of soluble cesium decreases over the first 5 - 10 days following contamination until removals are insignificant (<12%). Changes in the removal efficacy of contaminants that are primarily removed via physical decontamination mechanisms over time, such as inert particles encapsulating radioactivity, were insignificant. Contaminant depth profiles showed that particles did not migrate into the subsurface whereas cesium did. After two months of aging at 65% - 75% average relative humidity with artificial rainfall events, the majority of cesium was found within the first one millimeter of the subsurface. The application of rainfall events after contamination facilitated the migration of cesium into the concrete subsurface. The understanding of decontamination efficacy changes and contaminant-surface interactions as the time between contamination and decontamination increases will aid in recovery planning efforts.
Issue Date:2020-03-19
Rights Information:Copyright 2020 Katherine Hepler
Date Available in IDEALS:2020-08-26
Date Deposited:2020-05

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