Dynamic Finite Element Analyses of the Primary System of the Atucha II NPP under Beyond Design Basis Earthquakes

JOSÉ RISSO; ALBERTO CARDONA; AGUSTIN PECORARI; ADRIANA POLITI

La Plata

Congreso; Congreso ENIEF 2017 XXIII Congreso de Métodos Numéricos y sus Aplicaciones.; 2017

Facultad de Ingenieria UNLP

Atucha II Nuclear Power Plant (CNA II) is a pressurized heavy water reactor (PHWR) that started its commercial operation in May 2016. Construction began during 1980, and the designlicensing base, agreed between the Responsible Entity (CNEA at that time) and the designer(KWU/Siemens), did not consider the double-ended guillotine break (DEGB) event in the primarypipe loop as a requirement of the emergency core cooling systems and reactor shutdown. Instead, a10% loss of coolant of the cross section of the primary system, which would be equivalent to asurgeline DEGB (line connecting the primary system with the pressurizer), was considered. TheAutoridad Regulatoria Nuclear (nuclear regulatory body of Argentina ? ARN) entrusted the realizationof an independent evaluation, to assess whether a DEGB caused by a beyond design basis event couldbe possible. A dynamic analysis of the Loop 2 of CNA II?s primary system was performed employingthe finite element method (FEM) for a beyond design basis earthquake scene, i.e. an earthquake with amean probability of exceedance of 10-6 per year, to evaluate the possibility of occurrence of a DEGBwith critical preexisting areas with circumferential through-wall cracks in the primary system. Themodel utilized displacement time histories as input data, applied at the supporting points of majorcomponents (reactor pressure vessel, stream generator, main coolant pump, pressurizer), obtained bynumerical integration of the acceleration time histories at such points, provided by the designer.