Re-Evaluation of the Indoor Resuspension Factor for the Screening Analysis of the Building Occupancy Scenario for NRC's License Termination Rule - Draft Report for Comment (NUREG-1720)
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Manuscript Completed: April 2002
Date Published: June 2002
R.M. Abu-Eid, R.B. Codell, N.A. Eisenberg*
T.E. Harris, S. McGuire**
*1208 Harding Lane, Silver Spring, MD 20905
**Incident Response Office, U.S. Nuclear Regulatory Commission
Division of Waste Management
Office of Nuclear Material Safety and Safeguards
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
The purpose of this study was to re-evaluate the resuspension factor (RF) parameter used in the screening analysis for demonstration of compliance, using the building occupancy scenario, with the radiological criteria in the license termination rule in 10 CFR 20, Subpart E. The RF is a highly sensitive parameter impacting the inhalation dose calculation. An RF parameter value of 1.42 x 10-4 m-1 was established for screening analysis (Beyeler et al., 1999). Assuming a 10 percent fraction of loose (removable) contamination, NRC staff selected a default RF value of 1.42 x 10-5 m-1 for use in the inhalation dose calculation. Based on this RF value, and using the DandD code, the derived default concentration or surface activity screening limits for most radionuclides, particularly the alpha-emitters, were at background levels or far below the corresponding detection limits. In this study, NRC staff analyzed further literature data considering more realistic assumptions of the average member of the critical group in the building occupancy scenario and accounting for more recent actual RF field data collected for two facilities undergoing decommissioning. Based on the current analysis and re-evaluation, staff recommends using an RF value of 10-6 m-1 in the screening analysis of the inhalation dose calculation for the building occupancy scenario. The staff believes that the newly proposed RF default value is more realistic than the current value in DandD code and sufficiently conservative for screening analysis.