Assessment of Ultimate Load Capacity of concrete containment structures against structural collapse

Nuclear safety regulations in India require assessment of containment structure for Ultimate Load Capacity (ULC) for internal pressure. ULC and associated behavior of containment is evaluated with respect to various performance indicators based on defined criteria. Non-linear FE analysis of the containment structures was carried out considering non-linear material properties of concrete and steel using ABAQUS and ANSYS software. Evaluation of ULC was undertaken to understand containment performance under severe accident conditions, as a round robin analysis based on 1:4 containment model test results conducted at SANDIA national Lab, USA. AERB also participated in the international round-robin exercise organized by BARC to assess the ULC of BARC's containment test model (BARCOM). The test model is a 1:4 scale replica of 540 MWe PHWR pre-stressed concrete inner containment structure of Tarapur Atomic Power Station Units 3&4. Based on the knowledge gained from these studies VVER 1000 reactor building constructed at Kudankulam (KKNPP) was assessed for ULC of its primary containment as a regulatory requirement. VVER containment study was first of its kind as it is a lined containment with cellular basement structure. Non-linear FE analysis in ABAQUS using layered shell model was performed to assess the ULC of the containment structure. Three times of design pressure is estimated to be ULC of the structure.