Didier Fourcot Jul 6, 2016:

THROUGH the reactor pressure vessel? - from inside to outside: "molten debris" are inside the "reactor pressure vessel", that is in turn inside the "ex-vessel configuration"
- the pressure vessel that confines the molten debris fails, ie creates leaks, holes, etc, probably in the bottom for molten debris (core melt = corium?) rather than in higher parts from your larger context with noble gases
- the molten debris can then go through the failed pressure vessel (that hardly holds any pressure by the way) into the "ex-vessel configuration" that I understand as the secondary confinement (reactor building)

In short and plain English: corium is so hot that it melts the vessel that contains it and flows through to the outside of this vessel

Masoud Kakouli Varnousfaderani (asker) Jul 5, 2016:

More context After the fission products are released from the overheated reactor core, the noble gases, as well as the fission product vapours are transported by flows of gas or steam into cooler regions of the primary containment vessel (PCV). The fission product vapours start to condense to form small airborne particles (aerosols). These aerosols and the noble gases are then further transported by flows of gas or steam until they are either retained (e.g. by condensation, plate-out, scrubbing, etc.) inside the PCV or released into the environment through PCV leaks. The presence of very hot, high pressure steam in the RPV can create a number of possible leak paths, such as through the flanges of the SRVs or the seals of the recirculation pumps, for the other radionuclides to escape into the dry well and the SC of the PCV. While a fraction of the fission products released from the reactor core will be trapped in the water of the pressure suppression pool the remainder may be dispersed within the PCV and eventually released from the PCV to the outside atmosphere by either a controlled or an uncontrolled route.