Nuclear safety regulations in India require assessment of containment structure for Ultimate Load Capacity (ULC) for internal pressure. The Russian Federation designed WER 1000 reactor building constructed at Kudankulam (KKNPP) was assessed for ULC of its primary containment. The reactor building consists of a pre-stressed concrete primary containment and a reinforced concrete secondary containment built over a large cellular foundation structure consisting of containment base slab connected to the mat foundation through a number of reinforced concrete cross walls and intermediate slabs. The evaluation was carried out using a numerical model of the complete structure by non-linear Finite Element Method using ABAQUS software. The ULC value was established based on criteria specified in USNRC RG 1.216. The structural response was studied using the patterns observed in deformations, stresses & strains with rise in internal pressure. It is noted that structural response in general areas of the containment is linear till twice the design pressure (Pd). The start of yielding of reinforcing bars in the general area of the wall is noted at a pressure of 2.80 Pd. The ULC pressure is estimated as 3.0 Pd. Based on the study, it is concluded that structural capacity for pressure load of the steel lined pre-stressed concrete containment of KKNPP satisfies the Indian regulatory requirement.
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