241-AY-102 Leak Detection Pit Drain Line Inspection

摘要

On August 1, 2012 a routine visual inspection showed the presence of unexpected material on the floor of the secondary liner in Tank 241-AY-102 (AY-102). In October 2012, it was determined that waste had leaked into the annulus of AY-102. As a result, an extensive review of Tank AY-102 was conducted quickly triggering increased inspection and monitoring of the tank; however, the precise cause and location of the leak could not be determined. At the same time 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, 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. Therefore, a plan was initiated to ascertain the integrity of the secondary tank liner including a robotic inspection of the LDP. This paper provides a description of the design components, operational approach, and those results gained from the Tank AY-102 LDP drain piping visual inspection. To perform this inspection, a custom robotic crawler with a deployment device was designed, built, and operated, through subcontract, to inspect the 6 in (152.4mm) leak detection pit drain line. These tasks were accomplished, from initial award of the contract to completion of the inspection, in about two months.