Seismic evaluation of containment shell - WWER-1000 type reactor building

摘要

This investigation is part of the Modernization Program for units 5/6 (VVER 1000) of Kozloduy NPP, Bulgaria. ThernReactor Building is studied for the recently defined Review Level Earthquake (RLE) and Local Earthquakes (LE). A 3-DrnFinite Element model is used for definition of seismic response and seismic capacity assessment. Most attention is paid to therncontainment evaluation. For that purpose a complementary finite element model is developed. It represents the cylinder shell,rnthe dome and the supporting ring structure of the containment. The model is characterized by refined mesh and detailedrnrepresentation of loading caused by the stressing tendons. The structural stiffness increase due to prestressing is considered inrnthe modal analysis. First static analysis is performed with the pre-stressing loads, consequently eigenvalue analysis is donernunder consideration of the strains due to prestressing.rnThe capacity check of the containment is performed in meridian and circumferential direction separately. Principlernstresses from several load combinations are examined in order to determine the scenarios for containment cracking and lossrnof integrity. The domination loading is that caused by LOCA. The tension stresses however do not affect the structuralrnintegrity. The seismic effects are of minor importance. The HCLPF values of several scenarios studied show very highrnacceleration that may cause failure.