Regional Basic Professional Training Course in Korea

❙ 597 ❙
9. Probabilistic Safety Analysis
of the initial core inventory for each group of radionuclides having similar physical
and chemical characteristics;
The time of release, which is relative to reactor shutdown;
The location of release, relative to ground level;
The energy content of release, which is a function of containment temperature and
pressure prior to failure;
The particle size distribution of released aerosols, which affect the deposition
during plume transport.
In order to assess these characteristics, several plant specific source term calculations
should be performed with an appropriate computer code, considering the following
phenomena:
Release of fission products during core heat-up, degradation and meltdown,
chemical reactions between fission products, and cladding and control rods;
Retention of fission products within the reactor coolant system, condensation of
fission products vapour on structures, aerosols agglomeration and deposition,
chemical interactions with metallic surfaces, re-vaporization, and mechanical
re-suspension of material previously deposited;
Release of fission products during the ex-vessel phase, due to steam explosion or
core concrete interaction;
Retention of fission products inside the containment, aerosol agglomeration and
deposition, chemical reactions with structures and paints (especially for iodine),
effect of spray system, and deposition inside suppression pool water (for BWRs);
Retention of fission products within the ventilation systems and the containment
filtered venting system, if such a device is installed.