ICONE19-44118 Influence of aircraft impact on seismic isolated SMR reactor

Abstract

In the past decades a lot of effort has been done to increase the reliability of NPP, particularly against the earthquakes effects, adopting the highly attractive strategy of the seismic isolation. Isolator bearings seem able to increase the safety margin/integrity of the safety relevant nuclear structures and to enable the standardization of the reactor design to be deployed across a wider range of sites. However in principle the design of a nuclear power plant depends on the safety aspects related also to other type of external events, like the aircraft impact that was/is of relevant importance for NPP safety (especially after the Sept. 2001) and must be considered in the design of both Generation III+ and IV reactors. This paper is related to a preliminary study of the global response of a seismically isolated reactor building subjected to a vicious commercial aircraft impact. In this framework the effects of impulsive loading due to the progressive aircraft crashing were evaluated, considering the potential for structural failure of the external building walls due to shearing and bending dynamic loads, with reference to the effects of the structure perforation, including concrete spalling of the internal surfaces and propagation of dynamic waves that could affect NPP safety systems and structures. To the purpose a rather refined numerical methodology was employed; three-dimensional models (FEM approach) of a reference SMR reactor containment and possible realistic aircraft structures were set up and used in the performed analyses, taking also into account suitable materials behaviour and constitutive laws. The structural analysis of the reference NPP internal components was carried out to appropriately check mainly the containment strength margin in the case of the considered accident and test the chosen models and numerical calculation approach.