Stress Analysis of CANDU Containment Structure Hatch Opening
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Abstract
The CANDU3 containment structure batch opening is located 2.0 meters above the base slab. Subsequently, in the design of the containment structure, it is important to examine the stress concentration. deflection and rotation of the walls in the opening zone. This becomes more complicated when one includes the presence of the containment structure steel liner. Preliminary Axi-symmetric finite element model of the containment structure can only provide the over all stress state of the structure but can not include the opening. In the past imposed boundary conditions were applied to the cut-away of the containment structure opening to simulate the effect of the rest of the structure, this led to the need for interpretation of such input. Therefore, a full 3-D finite element model of the containment structure with the opening included is required to provide an appropriate structural stress assessment. This paper examines the analysis scope, work process, displacement and stress state in the containment structure opening area under different loading conditions and under different containment structure base boundaries. 1be base boundaries includes the following: i. Fixed wall base boundary without the containment structure base slab; ii. containment structure base slab sliding boundary; iii. 3-D model with the substructure of the soil cake added to the containment structure to represent a more realistic interaction. Results obtained from the analyses are compared with the results from the Axi-symmetric model. The comparison reflects a fair agreement between the 3-D model and the Axi-symmetric model away from the opening zone and the base slab boundaries. A higher degree of conservatism was observed when using fixed base boundaries when compared to the containment structure model with the full bard soil substructure attached. The results also provides the stress concentration level around the comers and under the opening. The deflection and rotation magnitude of the walls in the opening area will assist in selecting the appropriate connection type between the air lock and the containment structure walls.
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