Regional Basic Professional Training Course in Korea

In-vessel processes during the late phase of damage progression,
Ex-vessel processes at or soon after vessel breach;
Long term processes following vessel breach.
9.4.4.2. Physical phenomena
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9. Probabilistic Safety Analysis
All physical phenomena involved in severe accidents should be considered as far as they
influence the challenge to the containment integrity and the fission product source terms.
A typical list of the physical phenomena to be considered is the following:
Core heat-up, degradation and meltdown, cladding rupture, hydrogen production
by cladding oxidation, and flowing down of corium to the vessel bottom;
Interaction between corium and water in the vessel bottom, in-vessel steam
explosion, blast loads, missile generation, vessel head rupture, and consequences
for containment integrity;
Vessel bottom rupture, corium dispersal into the containment building, direct
containment heating, and consequences for containment integrity;
Interaction between corium and water in the reactor cavity, ex-vessel steam
explosion, interaction between corium and concrete, and non condensable gas
generation;
Containment pressurization, hydrogen combustion in the containment (laminar and
turbulent deflagration, detonation), and consequences for containment integrity.
These physical phenomena must be evaluated using appropriate computer codes, where
the phenomena and the events that may appear in the course of the accident are modelled
and where the interactions between these phenomena are correctly considered.