The deformational responses of urania fuel pellets

This paper reviews deformational phenomena experienced in light water reactor fuel pellets under normal and anticipated operational conditions. The review is an initial step to help organize observational information and to suggest how it might be applied in the qualification of fuel performance codes. The general development is to present observations in the form of either photo macrographs or micrographs. These observations were collected from a number of cooperative programs as representative examples. The physical phenomena suggested by these observations, their influence on pellet deformational evaluations and references to methods used to model the phenomena are then presented. The major phenomena covered are fuel cracking, fuel and void restructuring, dish filling, localized deformations at crack and pellet interfaces, chemical deposits and axial force redistribution by friction and trapped stack effects. Included in the review are comments on the influence of various phenomena and model assumptions on the procedures used to evaluate fuel performance. (author)