Preliminary Study on Effect of Baseline Correction in Acceleration Excitation Method on Finite Element Elastic-Plastic Time-History Seismic Analysis Results of Nuclear Safety Class I Components

원전 안전 1등급 기기의 유한요소 탄소성 시간이력 지진해석 결과에 미치는 가속도 가진 방법 내 기준선 조정의 영향에 대한 예비연구

Abstract

The paper presents preliminary investigation results for the effect of the baseline correction in the acceleration excitation method on finite element seismic analysis results (such as accumulated equivalent plastic strain, equivalent plastic strain considering cyclic plasticity, von Mises effective stress, etc) of nuclear safety Class I components. For investigation, finite element elastic-plastic time-history seismic analysis is performed for a surge line including a pressurizer lower head, a pressurizer surge nozzle, a surge piping, and a hot leg surge nozzle using the Chaboche hardening model. Analysis is performed for various seismic loading methods such as acceleration excitation methods with and without the baseline correction, and a displacement excitation method. Comparing finite element analysis results, the effect of the baseline correction is investigated. As a result of the investigation, it is identified that finite element analysis results using the three methods do not show significant difference.

Fig. 1 Schematic configuration and lay-out of a surge line.

Fig. 2 Acceleration time-history at each support point.

Fig. 3 Displacement time-history at each support point.

Fig. 4. Finite element model of the surge line.

Fig. 5 Accumulated equivalent plastic strain distribution of the surge line calculated applying the acceleration time history with baseline correction.

Fig. 6 Equivalent plastic strain distribution considering cyclic plasticity of the surge line calculated applying the acceleration time history with the baseline correction.

Fig. 7 von Mises effective stress distribution of the surge line calculated applying the acceleration time history with the baseline correction.

Fig. 8 Comparison of the displacement distributions at final time among the various cases.

Fig. 9. Variation of the accumulated equivalent plastic strain time histories on the maximum value generation location according to application of the baseline correction and the acceleration/ displacement time histories.

Fig. 10 Variation of the equivalent plastic strain time histories considering cyclic plasticity on the maximum value generation location according to application of the baseline correction and the acceleration/displacement time histories.

Fig. 11 Variation of the von Mises effective stress time histories on the maximum value generation location according to application of the baseline correction and the acceleration/displacement time histories.

Table 1. Physical properties of SA508 Gr.3 Cl.1 and SA182 TP316 at 316 oC.

Table 2 Chaboche hardening model parameters of SA508 Gr.3 Cl.1 and SA182 TP316 at 316˚C¹³⁾.

Table 3 Comparison of the maximum accumulated equivalent plastic strain value vs. application of the baseline correction and the acceleration/displacement time histories.

Table 4 Comparison of the maximum equivalent plastic strain (considering cyclic plasticity) value and maximum value generation time vs. application of the baseline correction and the acceleration/displacement time histories.

Table 5 Comparison of the maximum von Mises effective stress value and maximum value generation time vs. application of the baseline correction and the acceleration/displacement time histories.