WM2009 Conference, March 1-5, 2009, Phoenix, AZ Structural Integrity of Single Shell Tanks at Hanford – 9491 Rinker MW, SP Pilli, NK Karri, JE Deibler, KI Johnson, JD Holbery, OD Mullen, and DE Hurley Pacific Northwest National Laboratory, Richland, WA-99352 ABSTRACT The 149 Single Shell Tanks at the Hanford Site were constructed between the 1940’s and the 1960’s. Many of the tanks are either known or suspected to have leaked in the past. While the free liquids have been removed from the tanks, they still contain significant waste volumes. Recently, the tank farm operations contractor established a Single Shell Tank Integrity Program. Structural integrity is one aspect of the program. The structural analysis of the Single Shell Tanks has several challenging factors. There are several tank sizes and configurations that need to be analyzed. Tank capacities range from fifty-five thousand gallons to one million gallons. The smallest tank type is approximately twenty feet in diameter, and the three other tank types are all seventy-five feet in diameter. Within each tank type there are varying concrete strengths, types of steel, tank floor arrangements, in-tank hardware, riser sizes and locations, and other appurtenances that need to be addressed. Furthermore, soil properties vary throughout the tank farms. The Pacific Northwest National Laboratory has been conducting preliminary structural analyses of the various single shell tank types to address these parameters. The preliminary analyses will assess which aspects of the tanks will require further detailed analysis. Evaluation criteria to which the tanks will be analyzed are also being developed for the Single Shell Tank Integrity Program. This information will be reviewed by the Single Shell Tank Integrity Expert Panel that has been formed to issue recommendations to the DOE and to the tank farm operations contractor regarding Single Shell Tank Integrity. This paper provides a summary of the preliminary analysis of the single shell tanks, a summary of the recommendations for the detailed analyses, and the proposed evaluation criteria by which the tanks will be judged. INTRODUCTION/BACKGROUND Single shell tanks (SSTs) are underground nuclear waste storage tanks having a single liner of carbon steel housed within a cylindrical reinforced concrete structure. A total of 149 underground SSTs were constructed during the years 1943 through 1964. These SSTs are divided into 12 separate groups (based on their location) referred to as tank farms. The twelve tank farms are identified as A, AX, B, BX, BY, and C in the 200 East Area and S, SX, T, TX, TY, and U in the 200 West Area of the Hanford Site near Richland, Washington. There are 133 large capacity (530,000, 758,000 and 1,000,000 gallons) 100-Series tanks with a 75-foot internal diameter and 16 small capacity (55000 gal) 200-Series tanks with a 20-foot internal diameter. Figure 1 shows four schematics of the 100 and 200-Series SST configurations. The three larger tanks are the 100-Series, and the smaller tank is the 200-Series in the figure. Tank geometry details, construction drawings and specifications are mentioned in greater detail in Han [1]. 1