Radiochemical trends and anomalies experienced during cycle 15 of the Haddam Neck nuclear power plant, as a result of >450 debris-induced fuel rod failures, presented a situation previously unreported in the nuclear industry. These data, along with shutdown and depressurization spiking data, needed to be evaluated against ultrasonic fuel assembly examination results to derive a predictive model, called the xenon pin equivalent (XPE), to be used for cycle 16. During the development of the model, a fission product release mechanism for this particular type of failure needed to be postulated based on cycle 15 data. The predictive model was tested during cycle 16, which presented similar but more subtle radiochemical trends than cycle 15. Several operational events affected the XPE model, including use of degasification and down-power maneuvers. After the cycle 16 shutdown, the XPE model results were reviewed and evaluated against ultrasonic testing results. Although expected to be conservative, this evaluation proved encouraging in that the model performed more accurately than expected. Additionally, these data helped confirm the postulated release mechanism and its contribution to the XPE model.