Risk analysis for industrial sites considers, very often, that accidental explosions generate given categories and shapes of structural fragments, i.e standardized projectiles, whose velocity depends on an arbitrary ratio of the total energy. Furthermore, a detailed analysis is required in order to evaluate the risk of impacts and the mechanical damage that may be caused to the surrounding facilities This paper presents a stochastic framework in order to define the source terms. i.e. the mechanical and kinetic features of the projectiles generated by an industrial explosion Based on the maximum entropy principle, the probabilistic distributions are developed for these fragment parameters: number, shape, mass, departure velocity and departure angles. These distributions are compared to the existing data collected from industrial explosions. The study is limited to the case of cylindrical and spherical vessels under pressure. (C) 2009 Elsevier Ltd. All rights reserved