Nonlinear dynamic verification of the boron injection lances for the Atucha-I Nuclear Power Plant

Abstract

This work deals with the nonlinear transient dynamic verification of the boron injection lances for the Atucha-1 Pressurized Heavy Water Reactor backup shutdown system. The lances inside the moderator tank constitute the end part of the fast boron injection piping. The current dynamic verification of the lances is performed in the context of modifications in the piping and valve configuration for Atucha-I Long Term Operation (LTO). It is intended to ensure the structural integrity of the lances in the event of Loss of Coolant Accidents (LOCA) and spurious opening of level control valves (Spurious) scenarios. All boundary conditions have been provided by Nucleoeléctrica Argentina S.A. (NA-SA), and a 3-D numerical model of the lances was built and analyzed with the open-source suite Salome-Meca v2019 using the Code_Aster finite element solver. Results indicate that the displacement of the lances does not produce collisions with other reactor internals and that stresses on the lances and their fastening bolts are low enough to ensure the correct function of the system during LTO period.