On slow crack growth in fuel cladding by finite element analysis

The present paper deals with the use of a thermoelasto-plastic finite element analysis for the prediction of the instability of a single crack or cracks and their subsequent growth in thin Zircolay fuel claddings. Special elements called 'Breakable elements' were developed for this purpose. This new computional algorithm allows not only considerably larger elements near the crack tip but also the gradual advance of crack front without having to re-number the finite element model. The equivalent rupture strain used as the criterion of initial crack growth is obtained from experimentally determined R-curve for the cladding material. It has been shown that slow growth of a minute crack in a fuel cladding resulting from the application of fission gas pressure can be determined analytically thus avoids costly experimental measurements. (orig.)