DOE OSTI2015
In October 2012, Washington River Protection Solutions LLC (WRPS) determined that waste had leaked into the annulus of Tank 241-AY-102. WRPS conducted an extensive review of Tank AY-102 and increased both inspection and monitoring of the tank; however, the precise cause and location of the leak could not be determined. In parallel with the leak in the primary tank, the Tank AY-102 leak detection pit (LDP) was accumulating water through the drain system external to the secondary tank liner. Liquid collecting in the LDP is suspected to be from water intrusion and collects at a rate such that the LDP must be pumped routinely. Following a routine pumping event on June 20, 2013, elevated radiation dose rates were noted on the transfer hose and surface contamination readings were found on the transfer pump when it was removed from the Tank AY-102 LDP. These two field readings suggested that tank waste from a secondary liner breach could be leaking into the LDP. As a result, WRPS initiated a plan to ascertain the integrity of the secondary tank liner including a robotic inspection of the LDP. To perform the robotic visual inspection, a custom robotic crawler with a deployment device was designed, built, and operated by IHI Southwest for WRPS to inspect the 6 in (152 mm) leak detection pit drain line. To ensure success when deployed in the field, the inspection equipment was demonstrated at both the IHI facility in Denver, Colorado, and the Hanford Site using full scale piping mockups. On November 20, 2013 WRPS inspected the 6 in (152 mm) diameter drain line. The deployment device successfully attached to the drain line, and the crawler entered the drain line and traversed to within approximately 7 ft (2.1 m) of the central sump located under the center of the tank before losing traction. Crawler performance was satisfactory, and the quality of the camera image and lighting provided sufficient detail to document the current condition of the visible regions of the pipe. The inspection showed that the majority of the drain line was dry. Two wet areas were observed, a portion of the line nearest the LDP and a portion near the center of the tank. The portion nearest the LDP was under water prior to pumping on November 14, 2013. Although sediment and debris were seen during the inspection, it is believed to be construction debris and corrosion products. No material was found in the inspection that looked like tank waste or the material seen in the Tank AY-102 annulus (i.e., no greenish or yellowish deposits or dark fluids, dried salt deposits, or crystalline material). The contamination levels seen on the crawler were consistent with past values seen on LDP pumping equipment. Sampling and analysis of the recovered residues from the crawlers did not find material consistent with tank waste. (authors)
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗