Underground radioactive waste tank remote inspection and sampling

Characterization is a critical step in the remediation of contaminated materials and facilities. Severe physical- and radiological-access restrictions made the task of characterizing the World War II-era underground radioactive storage tanks at the Oak Ridge National Laboratory (ORNL) particularly challenging. The innovative and inexpensive tank characterization system (TCS) developed to meet this challenge at ORNL is worthy of consideration for use in similar remediation projects. The TCS is a floating system that uses the existing water in the tank as a platform that supports instruments and samplers mounted on a floating boom. TCS operators feed the unit into an existing port of the tank to be characterized. Once inserted, the system's position is controlled by rotation and by insertion and withdrawal of the boom. The major components of the TCS system include the following: (1) boom support system that consists of a boom support structure and a floating boom, (2) video camera and lights, (3) sludge grab sampler, (4) wall chip sampler, and (5) sonar depth finder. This simple design allows access to all parts of a tank. Moreover, the use of off-the-shelf components keeps the system inexpensive and minimizes maintenance costs. The TCS proved invaluable in negotiating the hazards of ORNL's Gunite and Associated Tanks, which typically contain a layer of radioactive sludge, have only one to three access ports that are usually only 12- or 24-in. in diameter, and range from 12 to 50 ft in diameter. This paper reviews both the successes and the difficulties encountered in using the TCS for treatability studies at ORNL and discusses the prospects for its wider application in remediation activities