Kevin Konzen*, CH2M-WG Idaho, LLC ; Craig Nesshoefer, Idaho Cleanup Project

Abstract: CH2M-WG Idaho, LLC (CWI) had sought alternative surface clearance limits for personal property from those referenced in DOE Order 458.1, which were approved September 2013 by the Department of Energy. Because much of the property would remain within DOE control, implementation was contingent upon receiving an exemption from 10 CFR 835, Surface Contamination Values (pending). CWI requested these changes due to inadequate instrument sensitivity of standard field instruments used across the nuclear industry for the clearance of several listed radionuclides. This included 241Pu, 125I, and 129I listed in the transuranic category; 90Sr, 126I, 131I and 133I listed in the thorium category; and several Hard-To-Detect (HTD) radionuclides listed in the beta-gamma emitter category. Instrument detection capabilities are now required to be justified by DOE Order 458.1, with personal property meeting the measurement objectives specified in MARSAME. MARSAME provides a consistent approach across the industry for determining the instrument MDC for comparison with the clearance limits of personal property. Challenges were discovered with the standard GM pancake probe for achieving the required sensitivity necessary for releasing property with radionuclides listed in the beta-gamma emitter category, and was determined incapable of surveying beta-gamma emitters with total surface clearance limits below this category using standard field scanning techniques. This affected 90Sr and iodine radionuclides listed in the thorium and transuranic categories. Likewise, the transuranic category included all radionuclides meeting the generic definition of a transuranic radionuclide, such as 241Pu. CWI proposed establishing an HTD category with higher clearance limits for all radionuclides with an average beta or electron emission up to 50 keV. CWI also proposed clarifying that the transuranic and thorium category clearance limits were to be applicable only for alpha emitters, which included their associated decay products. CWI was able to justify these changes by providing a technical basis that included an exposure pathway analysis for property released to the public and an extensive literature review. The revised clearance limits and justification may have application with sites across DOE meeting similar challenges.

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