Dig-face monitoring during excavation of a radioactive plume at Mound Laboratory, Ohio

摘要

A dig-face monitoring system consists of onsite hardware for collecting information on changing chemical, radiological, and physical conditions in the subsurface soil during the hazardous site excavation. A prototype dig-face system was take to Mount Laboratory for a first trial. Mound Area 7 was the site of historical disposals of Th-232, Ac-227, and assorted debris. The system was used to monitor a deep excavation aimed at removing Ac-227-contaminated soils. Radiological, geophysical, and topographic sensors were used to scan across the excavation dig-face at four successive depths as soil was removed. A 3-D image of the contamination plumes was developed; the radiation sensor data indicated that only a small portion of the excavated soil volume was contaminated. The spatial information produced by the dig-face system was used to direct the excavation activities into the area containing the Ac-227 and to evaluate options for handling the separate Th-232 plume.