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Fig. 7.24 (c)&(d) : Residual Hoop Stress across the Thickness for (c) Isotropic Material Model and (d) Anisotropic Material
Model for different internal Pressure

Therefore, an experimental program to evaluate (ABAQUS) for fitness assessment of NPP components
the parameters for material model which accounts for were brought out.
anisotropy and cyclic behaviour for the Indian Pressure
Tube specimen is initiated. The gap areas are identified 7.9 SAFETY STUDIES TO SUPPORT REVIEW
through in-depth study of available published data. This AND ASSESSMENT
program is in collaboration with NML, Jamshedpur.
7.9.1 Benchmarking SSI Analysis of Lotung Quarter
7.8.2 Evaluation of Fracture Mechanics Parameters Scaled Containment Model
using XFEM
Soil-Structure Interaction (SSI) is an important
A benchmark was proposed by OECD/NEA to aspect of structural engineering, especially for
enable a comparison of XFEM capability of different massive constructions, such as nuclear power plants,
codes used in the nuclear industry. AERB participated concrete and earth dams, on soft soils. To ensure
in the benchmark. The principal objectives of the project safety of NPP structures of deep soil sites, detailed
were to compare Stress Intensity Factor (SIF) obtained analysis to capture the SSI phenomena realistically
by classical FE method and analytical formulae to SIF is needed. To have a detailed understanding of the
obtained by X-FEM. analytical approach for such analysis, a Standard

Simulation of benchmark problems for fracture Problem Exercise (SPE) on SSI was conceived with
mechanics parameters K , K , K for different type of USNRC, using the seismic response data from SSI
I
II
III
loadings (mechanical, thermal) was carried out using experiments conducted on the scaled containment
XFEM tool of ABAQUS. model at Lotung, Taiwan. As the first task of the SPE,
benchmarking SSI analysis of the Lotung quarter
The FE model of semi elliptical underclad crack in scale containment model was carried out in ACS
the shell of the reactor pressure vessel is shown in (Fig. SASSI, considering one case of horizontal East-
7.25(a)). Sequential heat transfer and structural analyses West shaking corresponding to the earthquake event
were performed to evaluate SIF values for thermal recorded on May 20, 1986. The response spectra at
loading which corresponds to LOCA conditions in reactor top and bottom of the containment, top and bottom
pressure vessel. Fracture mechanics parameters like SIF, of the steam generator has been compared with the
J-integral etc. were evaluated and these were compared recorded responses (Fig. 7.26). It was observed that
with analytical solutions (RSE-M code) as shown in (Fig. responses from the SSI analysis are generally in good
7.25(b)). Overall capabilities and advantages of XFEM agreement with the recorded motions.

94 AERB Annual Report 2019