Re-evaluation of floor response spectra of reactor building for Daya Bay NPP

The seismic analysis of nuclear island of Daya Bay Nuclear Power Plant (NPP) was just in accordance with the approaches in RCC-G standard for the model M310 in France, in which the simplified impedance matrix method was employed for the consideration of soil's function. In this paper the more sophisticated 3D half-space continuum impedance method based on the Green functions is used to analyze the function of soil. In addition, multi-group of input time histories was used in the seismic response analysis in the existing design and their average of responses for each group was taken as the design basis. The same multi-group of input time histories was used in the seismic response analysis in this study, but the average and enveloped value of responses for each case are calculated respectively to account for the uncertainty of input motions. Focused on the above two issues, the seismic responses of the reactor building are calculated and the floor response spectra (FRS), a very important data for the design of nuclear system and equipment, are generated and then compared with the corresponding design values, so that the evaluation and discuss on the design method and results are conducted. Some useful conclusions hopefully to provide some important references to the assessment of seismic safety margin for the NPP in operation are taken. (authors)