Seismic behaviour of PFBR core

Seismic analysis of the PFBR core, consisting of 1758 CSA, has been carried out using in-house computer code CORESEIS, for the horizontal excitations applied at the grid plate level corresponding to both OBE (0.066g ZPA) and SSE (0. 156g ZP A). Dynamic displacements are extracted. The maximum tip displacement are 12 mm and 18 mm and maximum displacements at the load pad level where the reactivity effects are maximum, are 6 and 10 mm under OBE and SSE respectively. The net reactivity due to horizontal excitation worked out to be 0.065$ and 0.085$ for ORE and SSE respectively. The reactivity addition due to vertical excitation is worked out to be 0.09$ corresponding to the computed relative vertical displacement of 2.0 mm between core and CSRDM, under OBE and 0.126$ corresponding to the relative displacement of 2.8 mm, under SSE. Both the reactivity values, in vertical and horizontal direction are combined and net reactivity addition (RMS) has been reported to be 0.11 $ (RMS) and 0.15$ (RMS) which are less than the specified limit (0.5 $). The maximum relative horizontal displacement, between core top and CR as calculated to be 21 mm, is within the limit of 25 mm. Hence there will not be any problem of insertability of CSR during EQ event. (author)