A biaxial stress-strain response model for LMFBR reactor vessels

In a reactor accident, the reactor vessel and the cover are loaded by the expanding “gas bubble”. The gas bubble is generated in the accident, as a result of highly-heated fuel forming pressurized vapour. There is an interest in a quick and simplified model for deformation dynamics studies to enable arrival at a proper design of the vessel and the cover. Earlier, a simplified 1-D vessel response model had been developed and used extensively for the scoping studies. It had been observed that the deformation dynamics and energy partition are considerably influenced by many design and other parameters; one of them is the vessel strength. It has been decided to consider a more realistic biaxial response model for the bulging deformation that the vessel undergoes in place of the uniaxial response model that had been assumed in the earlier studies. In this paper, the more realistic response model, its formulations and the comparison of its results with the results of the earlier model have been reported.