Highly detailed structural integrity assessment of the reactor pressure vessel nozzle of Atucha-I during a pressurized thermal shock event

• Published in: Nuclear engineering and design 2024-03, Vol.418, p.112905, Article 112905
• Main Authors: Rabazzi, Santiago M., Albanesi, Alejandro E., Nervi, Juan E. Ramos, Signorelli, Javier W.
• Format: Article
• Language: English
• Subjects: Atucha-1; Elastoplastic material behavior; High fidelity modeling; Pressure vessel nozzle; Pressurized thermal shock; Pressurized water reactor
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2024.112905

In pressurized water reactor (PWR) nuclear plants, reactor pressure vessel (RPV) nozzles are critical due to geometric stress concentrations that worsen with large temperature gradients. In the context of Atucha-I Long Term Operation (LTO) assessment, this work presents a high-fidelity thermo-mechanical simulation approach to verify the stress levels on the main nozzles of the vessel under a pressurized thermal shock event. Nucleoeléctrica Argentina S.A. (NA-SA) has provided the boundary conditions, including the thermal plume that results from computational fluid dynamics (CFD) simulations of the transient event. Then, using a one-way and non-conformal projection procedure, CFD data is coupled to a highly-detailed 3D finite element model (FEM), including the RPV, closure head, nuts and bolts, and moderator tank, all interconnected through non-linear contact condition that accounts for friction. Finally, a 3D FEM submodel assuming an elastoplastic material behavior with non-linear isotropic hardening is used to verify the structural integrity of the nozzle. Results indicate that the plastic strain and stresses on the nozzles are low enough to ensure the correct function of the reactor during the LTO period. •Thermo-mechanical verification of the main nozzles of the Atucha I pressure vessel.•The highly-detailed 3D FEM model of RPV and internals uses contact with friction.•Temperatures, pressures, and a thermal plume computed with CFD were considered.•Both linear elastic and elasto-plastic material models have been compared.•Plastic strain and stresses on the main nozzle ensure safe function of the reactor.