Seismic risk assessment of the Ignalina NPP refuelling machine

Abstract

The Ignalina NPP operates a RBMK type reactor. An important characteristic of the RBMK reactor is its online refuelling. The refuelling is carried out using the refuelling machine at a time of reactor operation. The refuelling machine is situated in the hall located above the reactor. The refuelling machine is supported and moved by a girder crane. The dropping dawn of the refuelling machine bears high risk to its integrity and reactor core functioning. One of risk scenarios considers impact of an earthquake on the plant. As a part of it, it is essentially important to carry out a global seismic assessment of the refuelling machine. The seismic assessment of the support of refuelling machine is presented in this paper. The response of the reactor building to an earthquake was considered in the seismic analysis. The recently updated free field response spectra for the Ignalina NPP site were applied. The 3D thin-walled FE model of the reactor building was used for analysis. The 5 damping was applied in calculation of the secondary response spectra of the refuelling machine. The response spectra of the acceleration and displacement of the supports of the refuelling machine were examined. The modelling was run for three different positions of the refuelling machine, i.e. at an initial position (waiting mode), at a position of unloading fuel assemblies and at a position of transportation.