Using Ansys for Seismic Simulation of Large-Scale Nuclear Equipment

Task Description

RATEN-CITON undertook the seismic assessment of a large nuclear tank (DA98), with over 700 metric tons of total mass, as part of a structural safety evaluation. The challenge was to accurately model complex support conditions—including snubbers, frictional sliding pads, and high-damping rubber bearings—and evaluate the tank’s response under postulated earthquake conditions, following ASME III and Eurocode 8 standards.

Pic. 1: Recent seismic analysis - DA98 Tank

Solution

Ansys Mechanical & CFD Integration: A full 3D FEM model was developed to capture nonlinear structural and fluid behavior, including sloshing effects, base excitation, and foundation interaction.

Advanced Simulation Techniques: Time history, modal, and spectrum-based simulations were used to assess both impulsive and convective seismic loads, while verifying saddle stress concentrations, deflections, and displacement limits.

Multiple Support Scenarios: Comparative simulations were run using frictional sliding models (µ = 0.2), snubber-based restraints, and high-damping rubber bearings (HDRB) with 4% and 13% damping, using viscodamper modeling and stiffness-based constraints.

Pic. 2: DA98-4T Basic Model

Benefits

• Max displacement reduction of 80% with HDRB isolators compared to unrestrained friction models.

• Compliant primary stress values across all configurations, meeting ASME III and Eurocode 8 Part 4 limits (e.g., Pl + Pb = 153 MPa vs. Sm = 397 MPa).

• Validated tank behavior under both fully filled and partially filled conditions, including sloshing verification, enabling a confident structural safety assessment.