92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Wednesday, 25 January 2012: 4:45 PM
Air Dispersion Modeling of Demolition of Radioactively-Contaminated Structures
Room 339 (New Orleans Convention Center )
James G. Droppo Jr., PNNL, Richland, WA; and J. P. Rishel, B. A. Napier, and R. W. Boom

Pre-demolition air dispersion modeling can be an invaluable tool in planning open-air demolition projects of radioactively contaminated structures. The planning for demolition of such buildings must ensure the protection of both workers and the public. The current cleanup of cold-war production of nuclear material production facilities includes plans to demolition highly alpha-contaminated structures operations that will often last for many months. To define potential exposures that may result from such extended demolition activities, pre-demolition air-dispersion modeling analyses using AERMOD have been conducted. Estimated hourly emission rates of transuranic materials during the full schedule of proposed demolition activities are used as input to these analyses. The climatological frequencies of occurrence of peak air and surface exposures at locations of interest are estimated based on five years of local hourly meteorological records. Based on the demolition activity occurring at any during the year, the radiation exposure modeling results include 1) composite site maps of worst-case maximum possible weekly air exposure levels, 2) case study site maps of maximum cumulative soil-surface depositions patterns, and 3) location-specific frequencies of occurrences of weekly air exposure levels. The maps are particularly useful in planning radiation-protection boundaries and defining needs for additional administrative controls. The air exposure distributions which reflect the local dispersion climatology primarily give an indication of the likelihood of exposure levels occurring during the demolition activities that exceed set exposure limits. A secondary use of the distribution is to use predictions to indicate the potential for detectable occurrences of exposure levels at local monitoring stations. The prediction of such occurrences, which depends on the sensitivity of the monitoring methodology, may be at levels that are well below the level of concern. Post-demolition modeling was also conducted based on the actual demolition schedule and conditions. The close agreement of modeled and monitoring results provides a confirmation of validity of the modeling efforts.

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