An experimental research program into the loose part damage process identified important mechanisms that govern accumulated loose part damage to steam generator tube sheets. Relationships were developed to quantify damage due to single and multiple impacts, including such effects as tube end open diameter reduction and tube end contour deformation. These experimental investigations have led to the development of a computational model for estimating loose part impact damage on steam generator tube ends. Comparisons to experimental data show the loose part damage model to be a good approximation of actual loose part impact damage and provide a convenient and quantitative linkage between loose part impact properties and damage. Impact damage effects are local effects that depend only on the single impacts and impact overlaps in a small region of interest. The damage can be directly related to local impact density. Since in general the local impact density on a steam generator tube sheet is unknown, a model developed to simulate loose part impact distributions as a function of operating conditions is described.