Nonparametric statistical methods applied to the final status decommissioning survey of Fort St. Vrains prestressed concrete reactor vessel

by Pamela Longmire

Institution: The Ohio State University
Department: Nuclear Engineering
Degree: MS
Year: 1998
Keywords: Nuclear Engineering
Record ID: 1695609
Full text PDF: http://rave.ohiolink.edu/etdc/view?acc_num=osu1407398430


Final status surveys using the parametric statistical methodology prescribed in NUREG/CR-5849 were performed as part of the decommissioning process at Fort St. Vrain (FSV). Using this method, volumes of environmental data were generated to demonstrate that all radiological parameters satisfied established guidelines and conditions. The purpose of this thesis is to investigate the appropriateness of a nonparametric statistical method that requires collection of far fewer environmental samples to determine whether the decommissioned property has met the requirements for release for unrestricted use, and termination of the 10CFR50 license.Final status survey data collected at FSV was used in this study. In particular, the final radiological condition of the prestressed concrete reactor vessel (PCRV) surfaces (i.e., walls, floor, and bottom head penetrations) and metal tendon tubes in the walls was investigated. Radiological information contained in the release records at FSV for the PCRV surfaces and metal tendon tubes was analyzed by employing both parametric and nonparametric statistical methods. The radiological parameters of interest were total and removable surface activity, and exposure rate. NUREG/CR-5849 methodology, using parametric procedures, was applied to measurements collected at or near the PCRV surfaces and the same results that FSV reported in their documentation were reproduced in this study. When nonparametric procedures described in NUREG-1505 were applied to the same data, far fewer measurements were required to arrive at the conclusion that the survey units met the unrestricted use release criteria.