Evaluation of seismic integrity for an integral reactor assembly

The structural integrity of integral reactor assembly of 65 MWt thermal capacity is assessed by using the commercial finite element package ANSYS in order to evaluate the seismic safety margin. First of all, the modal analyses are performed using the various analysis models with/without the fluid coupling effect in order to validate a super element model and to evaluate the coupling effect on natural frequency. Based on the modal analysis results, the seismic analyses are performed using the ground response spectrum defined in Reg. Guide 1.60. Finally, time-history analyses are performed using the modal analysis results, the super element model and an inertia load approach. As a result, the reliable and efficient seismic analysis model for an integral reactor assembly is developed and it is found that an integral reactor assembly has the sufficient seismic safety margin. The results show that the resonance of the integral reactor can hardly occurred because its fundamental frequency (70 - 72 Hz) is relatively higher than zero period acceleration frequency (33 Hz). Therefore, there is less possibility of reactor damage from earthquake than other structures