A Procedure to Address the Fuel Rod Failures during LB-LOCA Transient in Atucha-2 NPP

Table 1

Specific acceptance criteria for design basis accidents [2].

Safety parameter	Criterion for the DBA
Fuel temperature	𝑇max<𝑇melt for 90% of pellet cross-section at hot spot
Fuel enthalpy (for RIA)	Average fuel hot-spot enthalpy < 180 cal/g for irradiated fuel
Heat transfer cladding/coolant	Departure from nucleate boiling (DNB) is admissible, except for the cases listed below under*
Cladding temperature	𝑇clad<1200^∘C except for the cases listed below* when 𝑇clad<650^∘C
Cladding integrity (for LOCA)	Limited loss of integrity admissible maximum local oxidation < 17%
Core-wide oxidation (for LOCA)	Maximum hydrogen generation H2<1% of H2TOTAL
Operation of PZR safety valves	Challenge admissible
RCS pressure	ASME code level C service limit (p < 1.2 𝑝design)
Secondary side pressure	ASME Code Level B Service Limit (p < 1.2 𝑝design)
Containment pressure	Maximum pressure < design pressure
Permissible dose	Calculated doses below limits 10CFR50.67 0.25 Sv total effective dose equivalent 0.05 Sv total effective dose equivalent for control room

*Examples of events with potential primary medium release outside the containment are (i) SG tube or moderator cooler tube rupture (with emergency mode), (ii) Long-term loss of main heat sink with SG or moderator cooler tube leakage (equal to operational leakages) (iii) Main steam line rupture outside containment with SG or moderator tube leakage (iv) Break of an instrument line in the annulus.