Design of Fuelling Machine and Carriage to Meet Seismic Qualification Requirements

Abstract

During each refuelling operation, the boundary of primary heat transport system is extended up to Fuelling Machines. A breach in the pressure boundary of Fuelling Machine in this condition would cause a loss of coolant accident. Fuelling Machines are also used for transit storage of spent fuel bundles till discharged to fuel transfer system. Therefore fuelling machine including its support structures is required to be seismically qualified for both on-reactor (coupled) mode and off-reactor (uncoupled) mode. The fuelling machine carriage used in the first generation of Indian PHWRs is a mobile equipment on wheels moving over fixed rails. As this configuration was found unsuitable for withstanding strong seismic disturbances, bridge type design with fixed columns was evolved for the next generation of reactors. Initially, the seismic analysis of the fuelling machine bridge and carriage was done using static structural analysis and values of natural frequencies for various structures were computed. The structures were suitably modified based on the results of this analysis. Subsequently, a detailed dynamic seismic analysis using finite element model has been completed for both coupled and uncoupled conditions. The qualification of the structure has been carried out as per ASME section III Division 1, sub section NF. Details of the significant design features, static and dynamic analysis, results and conclusions are given in the presentation.