Radiological Challenges Associated with Decontamination and Demolition of Two Highly Contaminated Outdoor Carbon Steel Ancillary Facilities at Hanford's N-Reactor Complex
G.J. Gibbons (Bechtel Hanford, Inc.)
The Hanford site is home to the Department of Energy's surplus N-Reactor Complex. Between 1963 and 1987, its purpose was to support the U.S. nuclear weapons program by producing plutonium from uranium targets. With the end of the Cold War, however, the mission for the reactor and its support facilities changed from plutonium production to dismantlement and disposal. During operations two support facilities to the N-Reactor complex, the 1304N Emergency Dump Tank (EDT) and the 1300N Emergency Dump Basin (EDB), were carbon steel structures that received and stored radiologically contaminated process water from the 105N reactor primary coolant loop and blowdown water from the 109N steam generator building. In order to support the new mission for the reactor complex, these facilities were demolished and disposed at the Environmental Restoration Disposal Facility (ERDF) located in the Hanford 200 West Area. Radiological hazards associated with these demolition activities included high levels of removable and fixed alpha and beta-gamma contamination, potential airborne radioactivity areas (ARAs), radiation areas (RAs), and high radiation areas (HRAs). These hazards were further compounded in complexity by being located within a close proximity (i.e. < 15 meters) to the Columbia River shoreline, which is an uncontrolled off-site location. Various contamination control and dose reduction methods were used to help mitigate these hazards to ensure the safe and successful removal of these facilities. Use of these methods and experience gained through lessons-learned during these evolutions may be useful at sites with similar radiological control hazards.