Technical Considerations for Using in situ Gamma Spectroscopy in Conducting Final Status Surveys


J. C. Dehmel, S. Schneider


Facilities undergoing decommissioning are required to conduct radiological surveys to initially characterize contaminants, guide remediation activities, and demonstrate that cleanup criteria have been met, based on screening or site-specific derived concentration guideline levels (DCGLs). Most decommissioning plans (DP) or license termination plans (LTP) rely on the use of hand-held instrumentation using technical guidance described in various U.S. Nuclear Regulatory Commission (NRC) documents, such as the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) and others (NRC 2000a,b, 1995a). However, licensees are considering the use of in situ gamma spectroscopy to supplement or replace conventional survey methods relying on hand-held radiation survey instrumentation, followed by sampling and analysis. Currently, the NRC provides only limited guidance (NRC 1995b) on using in situ gamma spectroscopy, which is not as detailed as that given for other types of survey instrumentation. In recognition that gamma spectroscopy technology is being considered by licensees, the NRC understands that technical considerations unique to this method should be shared since the method offers technical benefits, as well as cost savings when compared to conventional methods. This paper presents a number of technical considerations, not all inclusive, associated with the use of in situ gamma spectroscopy that should be addressed when such a method is proposed for conducting final status surveys. The technical issues identified here do not yet reflect the policy of the NRC on this subject.


This abstract was presented at the 35th Annual Midyear Meeting, "Decommissioning and Environmental Restoration", Instrumentation Session, 2/17/2002 - 2/20/2002, held in Orlando, FL.

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