This is the second part of a three-part series of papers addressing the probability of liner failure in a Mark-I containment. The purpose is to quantify melt release and spreading phenomena in a form suitable for use in the probabilistic framework as discussed in the first part of this series. The quantification of melt release parameters (quantity, superheat, and zirconium content) is derived from an assessment of available system code results and certain independent auxiliary considerations of the physics of the meltdown and slumping processes in the relevant geometries. The quantification of melt spreading phenomena is based primarily on simulant scaled experiments run specifically for this purpose; however, auxiliary considerations of the physics of operative cooling and quenching mechanisms also play a significant role in this assessment.