Envirocon recently added a complex radiological demolition project to its extensive demolition resume in completing the selective dismantlement and demolition of a uranium conversion facility in Gore, Oklahoma. The 600-acre site is southeast of Tulsa and located on the Illinois River. The demolition area encompasses the 85-acre process facility located within the site boundaries. Uranium processing operations at the site began in 1969 and in 1993 the owner terminated Nuclear Regulatory Commission (NRC) licensed activities.
The demolition of this facility was awarded to Envirocon in April of 2010 and was completed on schedule in April of 2012. This project was jointly executed by two Envirocon business units, Nuclear Services and Demolition Services. Expertise from both units was drawn upon to ensure safe, efficient, and cost-effective completion of the work. Envirocon worked with the owner to establish protocols and processes incorporating the owner’s existing radiological protection program by modifying the format from production to decommissioning, decontamination, and demolition. Envirocon’s own industrial safety program was implemented and managed on this project.
In fulfilling its mission, the uranium conversion facility had performed two process operations. The main process converted yellowcake uranium to uranium hexafluoride gas for shipment to the Department of Energy for enrichment. In addition, the facility processed depleted uranium for use in production of depleted uranium penetrator ammunition. Both processes involved various chemical states of uranium as well as caustic solutions utilized for digestion and fluorination of the uranium. Cleanup and demolition of the facility was further complicated because the facility underwent a “hot shutdown,” leaving substantial residual radioactive process feedstock in the piping, conveyors and vessels, as well as in the ventilation system and on the interior building structures. In addition, process chemicals were present in much of the equipment.
Evaluation of potential radiological and chemical exposure and consideration of industrial/mechanical safety issues were the main drivers in the choice of worker protection protocols, equipment selection, and overall project direction as the team worked through several conceptual approaches prior to actual field execution.
The main plant building was a four-story steel frame, metal clad building with approximately 95,000 square feet on the ground floor. It was the largest building in the process area and contained the uranium hexafluoride (UF6) conversion process equipment. Envirocon’s total scope of work included demolition of 15 facilities and structures, occupying over 265,000 square feet. Initial dismantlement activities included selective removal of uranium contaminated systems and components to prepare the main plant building for bulk demolition using heavy equipment. Envirocon worked closely with the owner to generate a complete hazard analysis for the work, paying close attention to the fluorine circuit, potentially the most hazard component of the work. Site employees purged and monitored systems ahead of demolition to ensure worker safety. High value process equipment including Monel vessels were removed for resale by the owner and residual process feedstock material was removed and turned over to the owner for disposition. In another building, the DUF4 facility, owner-designated components including a large bridge crane and a reactor vessel with associated valve manifolds were carefully removed and staged for resale to another facility.
Conventional demolition included concrete slabs, foundations and vaults, as well as sorting, segregating, and size reduction of stored piping, tanks, pumps, valves and other components staged at the site. To eliminate void spaces and potential subsidence, selected equipment and components were crushed or filed with contaminated soil. Once processed to meet waste acceptance criteria (WAC), demolition debris was transported and disposed of in an on-site cell.
The project was completed in April 2012 with Envirocon on-site personnel executing 20,400 manhours without a safety incident or environmental impact. The project management team and craft were involved in the development and implementation of the safety and project execution plans, which resulted in buy-in on all levels and resulting in an excellent project safety record while dealing with an ever changing and potentially hazardous work environment.
During the planning phase of the project, Envirocon developed a strategy to minimize manual dismantlement techniques to the extent practical and maximize the use of heavy equipment for dismantlement, size reduction, and processing. This approach ensured more effective labor utilization and smaller crew sizes; higher productivity; enhanced worker safety by removing the worker from the hazard; and accelerated schedule performance. This approach resulted in a 20% reduction in project costs. It also allowed for the removal and recovery of 100,000 pounds of uranium from the process which will be used for future production at another facility.
Overall, and from the perspectives of safety, efficiency, and client satisfaction, this was one of Envirocon’s most successful projects, an accomplishment we intend to duplicate at other nuclear facilities across the country.