Saxton Nuclear Experimental Corporation, Containment Vessel (CV) Concrete Removal: Decommissioning in a Flood Plan

The Saxton Nuclear Experimental Corporation (SNEC) constructed and operated a nuclear reactor in rural Pennsylvania as an early demonstration project. The 23.5 MWth pressurized water reactor (PWR) operated from 1962 through 1972, and completed operations with failed fuel experiments. The facility was placed into SAFSTOR and decommissioning activities began in the mid 1990’s. The reactor facility was sited on the banks of a Pennsylvania river within the immediate one hundred year floodplain. Because of the elevated groundwater levels at the site, completion of the decommissioning process would prove to be challenging. The containment was constructed as a vertical steel cylinder of 11/16” (1.75 cm) thick carbon steel, one hundred and nine feet (33 meters) tall with a diameter of fifty feet (15.25 meters). The bottom of the containment vessel was torispherical steel located approximately fifty feet below grade in the flood plain of Central Pennsylvania’s Juniata River. Construction of the vessel included an internal concrete structure that was designed as the ballast to prevent flotation of the vessel, and provided mechanical structure for the reactor and equipment installation. The steel cylinder provided the forms for the internal concrete installation. The initial phase of decommissioning for the reactor containment consisted of the complete removal of the reactor and associated components, and was completed in the late 1990’s without regard to stabilization requirements required to maintain the stability of containment. Due to concerns of possible radioactive material between the concrete structure and the steel shell, it was decided that the internal concrete would be removed. Removal of the concrete constituted removal of the ballast material and possibly degraded the structural integrity of the CV. Therefore, stabilization of the steel cylinder was required to prevent uplift (flotation) and/or deformation of the steel shell. This stabilization required the installation of a bedrock anchoring system, internal and external anti-buckling steel beam stiffener rings, and a complete site dewatering system. TLG Services completed concrete removal in October of 2002, and this paper will provide information and details of the complex concrete removal project, project challenges, and lessons learned.