DOE OSTI2010
This document contains the process knowledge, radiological data and subsequent statistical methodology and analysis to support approval for the radiological release of Corrective Action Unit (CAU) 117 – Pluto Disassembly Facility, Building 2201 located in Area 26 of the Nevada National Security Site (NNSS). Preparations for release of the building began in 2009 and followed the methodology described in the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM). MARSSIM is the DOE approved process for release of Real Property (buildings and landmasses) to a set of established criteria or authorized limits. The pre-approved authorized limits for surface contamination values and corresponding assumptions were established by DOE O 5400.5. The release criteria coincide with the acceptance criteria of the U10C landfill permit. The U10C landfill is the proposed location to dispose of the radiologically non-impacted, or “clean,” building rubble following demolition. However, other disposition options that include the building and/or waste remaining at the NNSS may be considered providing that the same release limits apply. The Final Status Survey was designed following MARSSIM guidance by reviewing historical documentation and radiological survey data. Following this review a formal radiological characterization survey was performed in two phases. The characterization revealed multiple areas of residual radioactivity above the release criteria. These locations were remediated (decontaminated) and then the surface activity was verified to be less than the release criteria. Once remediation efforts had been successfully completed, a Final Status Survey Plan (10-015, “Final Status Survey Plan for Corrective Action Unit 117 – Pluto Disassembly Facility, Building 2201”) was developed and implemented to complete the final step in the MARSSIM process, the Final Status Survey. The Final Status Survey Plan consisted of categorizing each individual room into one of three categories: Class 1, Class 2 or Class 3 (a fourth category is a “Non-Impacted Class” which in the case of Building 2201 only pertained to exterior surfaces of the building.) The majority of the rooms were determined to fall in the less restrictive Class 3 category, however, Rooms 102, 104, 106, and 107 were identified as containing Class 1 and 2 areas. Building 2201 was divided into “survey units” and surveyed following the requirements of the Final Status Survey Plan for each particular class. As each survey unit was completed and documented, the survey results were evaluated. Each sample (static measurement) with units of counts per minute (cpm) was corrected for the appropriate background and converted to a value with units of dpm/100 cm2. With a surface contamination value in the appropriate units, it was compared to the surface contamination limits, or in this case the derived concentration guideline level (DCGLw). The appropriate statistical test (sign test) was then performed. If the survey unit was statistically determined to be below the DCGLw, then the survey unit passed and the null hypothesis (that the survey unit is above limits) was rejected. If the survey unit was equal to or below the critical value in the sign test, the null hypothesis was not rejected. This process was performed for all survey units within Building 2201. A total of thirty-three “Class 1,” four “Class 2,” and one “Class 3” survey units were developed, surveyed, and evaluated. All survey units successfully passed the statistical test. Building 2201 meets the release criteria commensurate with the Waste Acceptance Criteria (for radiological purposes) of the U10C landfill permit residing within NNSS boundaries. Based on the thorough statistical sampling and scanning of the building’s interior, Building 2201 may be considered radiologically “clean,” or free of contamination.
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗