The growing number of Resident Space Objects, driven by advancements in technology and reduced launch costs, has increased the probability of in-orbit collisions, potentially producing space debris and thus posing significant sustainability challenges to the space environment. With over 30,000 catalogued objects currently in orbit, including recent mega-constellations like Starlink and OneWeb, the need for effective Space Situational Awareness programs is critical. In this context, this paper proposes an integrated architecture to model in-orbit fragmentation events (i.e., collisions and explosions), which represent a major source of space debris, and to estimate the resulting risk to space assets of interest in Low-Earth Orbit. The architecture comprises two main modules: one implementing the NASA Standard Breakup Model to determine the number and the characteristics of the fragments generated by the breakup event, and the other implementing the Uncertainty-aware Cube algorithm to compute collision rates while accounting for positional uncertainties. The proposed system supports several SSA functions, such as the estimation of the time evolution of the spatial density and the evaluation of the conjunction risk induced by generated debris cloud to given assets, such as those belonging to a mega-constellation. The applicability of the proposed architecture is demonstrated through realistic Low Earth Orbit scenarios, emphasizing the impact of fragmentation events on mega-constellations under different environmental conditions.