Radiation-induced damage in nucleosomal DNA from Auger electron cascades due to incorporated cold IUdR has been modelled through Monte Carlo simulations. Probabilities of DNA double strand break (DSB) production following a vacancy in the K, L, M and N shells of iodine are estimated. DSB complexity from the base damage accompanying a break was also estimated. Multiple DSB events were analysed for correlated breaks due to nucleosome periodicity. The probability of an Auger cascade causing at least one DSB strongly depended on the shell in which the initial vacancy was produced. This probability was approximately 0.35 for K and L shells and fell to 0.02 for the N shell. As expected, DSBs were predominantly induced in a nucleosome containing incorporated iodine and were accompanied with extensive base damage. Analysis of multiple DSB events showed that approximately 14% of the DSBs produced following a vacancy in the L1 orbital can be interpreted as correlated with base pair separation attributable to the nucleosome periodicity. The data generated in this work provide a basis for the development of photon-activation therapy using kilovoltage X rays incident upon IUdR sensitised tumours.