Lomapaseo,
@ TurbineD...."I assure you that the intact disc (minus the drive arm flange) is only unsupported for a few milliseconds, as the gas pressure drives it aft to a false bearing surface in the LPT inner duct. Now it is once again supported against a fairly low-friction surface, akin to the thrust bearing on your car's crankshaft against which your clutch reacts.
I think TurbineD is correct here, and from the statement, aft migration puts the Turbine's airfoils into the LPT Stator ring, where they are ejected from their slots. This eliminates the ability of the gas path to turn the IPT. The amount of aft migration is failure dependent; but if the circumferential fracture happens about the bolt flange, as he proposed, their is nothing to prevent the drift from continuing well past the Stator into the inner web of the partition.
The HP is receiving fuel in excess of the rpm ratio to flow, (via EEC), I think raw fuel may have entered the cavity to exacerbate the fire post separation, making matters worse. In any event, where do you put the fracture?