Appurtenance Influence on Type III Hanford Single-Shell Tank Structural Integrity
The interim stabilized Hanford Single Shell Tanks (SSTs) are currently undergoing a state of the art analysis to assess the structural integrity of the waste storage tanks, for cleanup and closure operations, considering their adverse thermal histories and an updated seismic hazard for the Hanford Site near Richland, Washington. The SSTs contain a variety of ancillary pits, piping, piping supports, risers, equipment, and penetrations known as appurtenances. These appurtenances may alter the structural response and ultimately could affect the structural integrity of the SSTs. An important challenge to the structural analysis of the SSTs is determining the impact of these appurtenances on structural integrity. To achieve this, the various appurtenances were reviewed and bounding appurtenance configurations for SST Types II and III tank designs were analyzed using finite element software. The bounding configurations for the Type II tanks considered four heavy offset pits with a central pit with and without a 36-inch diameter central post-construction penetration and four 42-inch diameter offset penetrations. The bounding configuration for the Type III tanks is a tank with two heavy offset pits and one heavy central pit. For each bounding configuration two finite element models are developed: a seismic analysis model and a thermal and operating loads analysis (TOLA) model. The TOLA models include a Type II or III thermal history, concrete cracking and thermal degradation, reinforcement yielding, and soil plasticity. Additionally, operating loads such as internal waste pressure and concentrated and distributed soil surface loads are applied to the TOLA model. The seismic model treats the tank concrete as linear elastic based on the present day degraded concrete properties. Also, in the seismic model the soil is treated as linear elastic while special techniques are used in the soil above the tank dome and along the tank wall to avoid soil arching and achieve the proper soil pressure on the tank walls. Seismic time histories (in the horizontal and vertical directions) are applied to the seismic model. The American Concrete Institute (ACI) has code requirements for nuclear safety-related concrete structures (ACI-349-06) that are used to evaluate the structural integrity of the SSTs. ACI-349-06 recommends evaluating factored load combinations against reduced tank section capacities to account for both loading and material uncertainties. From both the TOLA and seismic models the structural demands (forces and moments) are extracted from sections throughout the tank under the appropriate load combinations. These demands are compared against the ACI-349-06 capacities at each of the sections. This ratio of demand to capacity is reported as a measure of structural integrity. The Type II and Type III appurtenances configurations are found to increase the demand to capacity ratios in local regions near the appurtenances. Away from the appurtenances the influence on structural integrity is minor. A comparison of the Type II and III results show that even though the Type II offset pits weight less, they have a larger impact on the structural integrity of the tanks due to their locations. Finally, lessons learned from the Type II and Type III appurtenance analysis, and their application to the more complex Type IV structural integrity analysis, will be discussed.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1092674
- Report Number(s):
- PNNL-SA-84038; 830403000
- Resource Relation:
- Conference: Annual Waste Management Symposium (WM2012): Improving the Future in Waste Management, February 26 - March 1, 2012, Phoenix, Arizona, Paper No. 12255
- Country of Publication:
- United States
- Language:
- English
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