Decontamination and its role in the Fort St. Vrain decommissioning

The full scale decommissioning of a reactor requires the use of a variety of decontamination processes, techniques and equipment. In August of 1992, the decommissioning of the Fort St. Vrain High Temperature Gas-Cooled Reactor (HTGR) was initiated by Public Service Company of Colorado. The Fort St. Vrain Decommissioning Project is being performed by a team comprised of Westinghouse Electric Corporation, Scientific Ecology Group, and MK Ferguson. This project is the largest decommissioning and early dismantlement of a commercially operated reactor in the United States to date. The scope of the project includes decontamination and dismantlement of the Prestressed Concrete Reactor Vessel (PCRV) and decontamination/removal of contaminated plant systems, site cleanup, and a comprehensive final radiation survey. This paper discusses the various types of decontamination equipment, survey instrumentation and techniques used during the Fort St. Vrain Decommissioning Project. Decontamination techniques range from simple methods such as soapy water, high pressure washing, scabbling, strippable paint; to more complicated methods such as remotely operated grit blast equipment used to decontaminate embedded pipe. The parameters necessary to evaluate the cost effectiveness of various decontamination techniques are discussed. Typically this includes consideration of the type and level of contamination, the substrate and surface to bemore » decontaminated, the type and volume of waste generated from the decontamination process, whether the decon will be performed on site or off site, equipment and labor costs, project schedule impact, and the unconditional release criteria that must be achieved. These factors and costs are then compared to the costs associated with the removal, possible volume reduction and final disposal of a particular component or system. The successes and lessons learned during the Fort St. Vrain Decommissioning Project are presented.« less