A Successful Remediation Project

As part of a program to visit formerly licensed sites to determine if they meet current uncontrolled release conditions, a United States Nuclear Regulatory Commission (USNRC) inspection was conducted in the fall of 1993 at a site that had possessed a radioactive material license from about 1955 to 1970. While the license was in force, the plant processed magnesium scrap containing up to 4 percent thorium. The source of the scrap is believed to be the aircraft manufacturing industry. The scrap was placed in furnaces and heated to the melting point of magnesium, and the molten magnesium was drawn off, leaving the thorium with the residue (dross). Under the regulation in existence at that time, the thorium dross was buried on site in an approximate 14 acre field. In 1993 the inspector found readings up to 900uR/h. Early in 1994 an informal grid survey of most of the 14 acre site was conducted. Based on that survey, it was concluded that the thorium was widespread and extended beyond the property lines. The preliminary findings were reported to the USNRC, and in 1994 the site was designated as a Site Decommissioning Management Plan (SMPD) site. A remediation team was formed which included the following disciplines: remediation health physics, geology, hydrology, engineering, law, public relations, and project management. This remediation team planned, participated in selecting vendors, and provided project over site for all activities from site characterization through the final status survey. In 2006 the site was released for uncontrolled access. A chronology of activities with lessons learned will be presented.